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• A micro pulsed plasma thruster was developed and tested. • Specific impulse reaches 1600 s and efficiency greater than 10 %. • The designed thruster has been used in Hangsheng-1 Satellite. Pulsed plasma thrusters appeal to the propulsive tasks on miniaturized satellites because of the low volume and high specific impulse. However, further increasing efficiency and reducing the size of pulsed plasma thrusters still require more effort. In this paper, the thruster's spark plug, plate structure, ignition system, charging system, electromagnetic compatibility system, and propellant have been particularly designed to maximize its performance and miniaturize its dimension. With the conducted designs, the whole mass of the micro-pulsed plasma thruster is 450 g, and its dimension is 90 mm * 90 mm * 35 mm. According to the experimental results, the specific impulse reached 1600 s, and the efficiency was more significant than 9 %. Thanks to its excellent performance, we have used this thruster for attitude control and drag compensation tasks on the Hang-sheng-1 Satellite. [ABSTRACT FROM AUTHOR]

In this study, the laser induced fluorescence lifetime of Ni atoms in ambient air with presence of a plasma discharge was measured for the first time. Free Ni atoms were generated in air at a pressure of 1 bar by spark plug discharges driven by an inductive coil. The Ni atoms were excited at the 336.957 nm absorption line by a 336.96 nm, 90 ps laser pulse and the resulting temporally resolved decaying fluorescence signals were captured by a PMT. An effective fluorescence lifetime of about 1.1 ns was observed for the fluorescence signal within a 7.4 nm detection window centered at 345 nm. Further analysis also revealed that the lifetime of the transition showed statistically insignificant change throughout the duration of the discharge. The peak intensity of the fluorescence signal was found to be proportional to the integrated signal intensities. This in turn suggests that the integrated fluorescence signals in the aforementioned spectral region are proportional to the population density of ground state Ni atoms in the detection volume. The number density of free Ni atoms in the spark gap was measured over time during the plasma discharge, showing an accumulating trend in the beginning phase of the discharge followed by a slow decrease until the termination. [ABSTRACT FROM AUTHOR]

Due to high greenhouse gas emissions, countries worldwide are stepping up their emission reduction efforts, and the global demand for new, carbon-free fuels is growing. Ammonia (NH3) fuels are popular due to their high production volume, high energy efficiency, ease of storage and transportation, and increased application in power equipment. However, their physical characteristics (e.g., unstable combustion, slow flame speed, and difficult ignition) limit their use in power equipment. Based on the structural properties of the power equipment, NH3 fuel application and emissions characteristics were analyzed in detail. Combustion of NH3 fuels and reduction measures for NOx emissions (spark plug ignition, compression ignition, and gas turbines) were analyzed from various aspects of operating conditions (e.g., mixed fuel, fuel-to-exhaust ratio, and equivalence ratio), structure and strategy (e.g., number of spark plugs, compression ratio (CR), fuel injection, and ignition mode), and auxiliary combustion techniques (e.g., preheating, humidification, exhaust gas recirculation, and secondary air supply). The performance of various NH3 fuel cell (FC) types was analyzed, with a focus on the maximum power achievable for different electrolyte systems. Additionally, the application and NOx emissions of indirect NH3 FCs were evaluated under flame and catalytic combustion conditions. The system efficiency of providing heat sources by burning pure NH3, anode tail gas, and NH3 decomposition gas was also compared. Based on a comprehensive literature review, the key factors influencing the performance and emissions of NH3-powered equipment were identified. The challenges and limitations of NH3-powered equipment were summarized, and potential strategies for improving efficiency and reducing emissions were proposed. These findings provide valuable insights for the future development and application of NH3 FCs. [ABSTRACT FROM AUTHOR]

In this study, three-dimensional modelling and simulation of a high-power six-cylinder hydrogen-blended methanol engine with direct hydrogen injection and methanol port injection were conducted using the simulation software CONVERGE. The control variable method was used to study the effects of hydrogen nozzle diameters of 1, 2, 3, and 4 mm on the in-cylinder airflow movement, hydrogen distribution, combustion, and emission characteristics of the hydrogen-blended methanol engine. The results showed that, with an increase in the hydrogen nozzle diameter, the injection duration was shortened, the distribution of hydrogen in the cylinder tended to be uniform, and the speed of flame propagation in the cylinder decreased. When the nozzle diameter was small, noticeable hydrogen accumulation occurred near the spark plug at the time of ignition, which accelerated flame propagation. Compared with increasing the diameter of the hydrogen nozzle, reducing the diameter of the nozzle caused the peak cylinder pressure and peak heat release rate to increase significantly; the ignition delay period was shortened; the mean indicated pressure and indicated thermal efficiency increased; and the emissions of CO, HC, and unburned methanol decreased, but the NO x emissions increased. Compared with pure methanol engines, hydrogen blending can optimise the combustion of methanol engines to a certain extent, improve power performance, and reduce the emissions of unburned methanol and formaldehyde. Therefore, a hydrogen nozzle diameter of 2 mm is considered the best solution for a hydrogen-blended methanol engine. • Hydrogen direct injection and methanol port injection. • Hydrogen-blended methanol engine has better combustion characteristics. • The hydrogen distribution under different hydrogen nozzle diameters was compared. • The engine with a hydrogen nozzle diameter of 2 mm has the best overall performance. [ABSTRACT FROM AUTHOR]

In this paper, in order to improve the fuel economy of the actual application of the engine under multi-operating conditions, an experimental study is carried out on a turbo-charged direct-injection engine based on different pre-chamber structures. The engine used for the study is a four-cylinder turbo-charged direct-injection gasoline engine with different structures of pre-chamber spark plugs. The operating conditions in this study include load characteristics at 2000 r/min and characteristic loads at different speeds, including 3000 r/min, 3200 r/min, and 3600 r/min. With stable BMEP or fully open throttle and pedal, the experiment was conducted by the spark angle scanning method to collect data of engine power, economy, and emission under each condition. It was found that the pre-chamber structure has a direct effect on engine performance, with a clear load demarcation line for its effect. Under the WOT condition, the power of pre-chamber ignition is 1.6% higher than that of conventional spark plugs; at the low load of 2 bar, the economy of pre-chamber ignition is degraded by 6%; at the medium load of 8 bar, the economy of the two is comparable; at the large load of 16 bar, the fuel economy proves advantageous. Compared with conventional spark plugs, the pre-chamber spark angle can be advanced by 2~3 °CA, and the pre-chamber ignition with separate ground electrodes is highly reliable. The emission levels of the pre-chamber spark plugs and conventional spark plugs are comparable at all loads. [ABSTRACT FROM AUTHOR]

Hydrogen fuel is gaining particular attention in internal combustion engines. In addition to zero-carbon emissions, major advantages relate to its combustion characteristics, which allow a significant increase in thermal efficiency under ultra-lean operation and with very low NOx levels. The ignition system is one of the main technology enablers, as it determines the capability to control ultra-lean operations, avoid backfire phenomena, and/or reduce the risks of abnormal combustions. The latter results from hydrogen's low ignition energy and it is associated with factors like high-temperature residuals, hot spots, and irregular spark plug discharge. The ACIS gen 2-Barrier Discharge Igniter excels in accelerating the initial flame growth speed by the generation of non-equilibrium low-temperature plasma, a strong ignition promoter for the combined action of kinetic and thermal effects. Moreover, its volumetric discharge facilitates combustion initiation on a wide region, in contrast to the localized ignition of traditional spark systems. In this work we present for the first time, to the best of our knowledge, experimental results showing the performance of a hydrogen engine with a low-temperature plasma discharge. Tests were conducted on a single-cylinder research engine, achieving ultra-lean conditions with cycle-to-cycle variability results below 2.5%. The analysis indicates that the H2-BDI combined solution is capable of accelerating the evolution of the flame front compared to traditional spark plugs, leading to a significant reduction in the cycle-to-cycle variability. A meticulous adjustment of the BDI control parameters further enhances igniter performance and contributes to a deeper understanding of the innovative approach proposed in this study. [ABSTRACT FROM AUTHOR]

Present paper numerically investigates the effect of injection strategy and start of injection (SOI) timing on in-cylinder flow, air–fuel mixing, fuel distribution near spark plug, engine performance, and exhaust emissions for highly stratified methanol-fueled, multi-injection, direct injection spark ignition engine having high compression ratio. SOI is kept constant at −23° crank angle (CA) after top dead center (ATDC) with a spark timing (ST) of −2° crank angle (CA) ATDC. Mass of fuel is divided into pilot and main injection ports having pilot to main fuel injection mass ratio of 1:1, 1:2, and 1:3 at 0° and 2° dwell times between main and pilot injections. As the quantity of fuel in main injection increases, pressure rise rate increases, which results in higher in-cylinder pressure and higher rate of burning that gives higher apparent heat release. Due to higher peak pressure rise rate and faster burning in the case of 2° crank angle (CA) dwell time, shorter combustion duration is achieved compared to 0° crank angle (CA) dwell time. In the case of multi-injection, faster burning rate enhanced in-cylinder temperature; therefore, nitrogen oxides (NOx) emissions are higher. Pilot to main fuel mass ratio of 1:3 has resulted highest indicated thermal efficiency, lowest specific fuel consumption, lowest soot, and carbon monoxide (CO) emissions. [ABSTRACT FROM AUTHOR]

The study delves into the potential application of the direct injection (DI) hydrogen engine as a carbon-neutral power source, exploring mixing and combustion dynamics across varied injection pressures. This research identifies an optimal injection strategy based on a 3-cylinder 4-stroke cycle turbocharged DI hydrogen engine crucial for enhancing the combustion behavior, significantly influenced by mixture formation. Numerical simulation results for a single cylinder show that rapid flame propagation hinges on a relatively rich mixture surrounding the spark plug. Surprisingly, low-pressure injection demonstrates superior combustion performance under the late-injection strategy, emphasizing the importance of an adjusted nozzle diameter to compensate for reduced flow rates. Furthermore, increasing the nozzle diameter from 0.8 mm to 3.0 mm with an optimal injection timing approaches the same combustion performance under the same injection pressure of 15 MPa. Moreover, low-pressure injection not only augments nozzle sealing and durability but also exhibits promising combustion efficiency and power generation under specific conditions. The study underscores the need for forthcoming research in low-pressure DI hydrogen engines, stressing the significance of high-performance injectors, emission mitigation technologies, and evolved combustion theories. • Mixing and combustion dynamics across varied injection pressures were explored for H 2 ICE. • Rapid flame propagation hinges on a relatively rich mixture surrounding the spark plug. • Low-pressure injection exhibits superior combustion performance and power generation. • An adjusted nozzle diameter was emphasized to compensate for reduced flow rates. [ABSTRACT FROM AUTHOR]

Hydrogen addition in SI engines has been a subject of extensive research over the years, primarily owing to its environmentally friendly attributes and its potential to optimize combustion, especially in lean-burn conditions. However, the use of hydrogen as a gaseous fuel presents challenges due to its high mass-to-volume ratio, which can substantially reduce engine power density, whether in direct injection (DI) or port injection PI conditions. Thus, how to maximum hydrogen's benefits on combustion while minimizing its consumption has become a topic worthy to be studied. In this research, a novel concept where hydrogen direct injected through an aperture on edge of the spark plug (SHDI) was proposed and experimentally investigated on a 1.5 L turbocharged gasoline direct injection (GDI) engine under lean-burn condition. Experiments were conducted at 1600 rpm and medium load conditions with hydrogen injection ratios φ H 2 varying from 0 % to 5.5 % and excess air coefficients (λ) up to 1.5. Hydrogen port injection (HPI) strategy was also employed as a reference to gauge the performance enhancement achieved through SHDI. The experimental results reveal that, in comparison to HPI, SHDI exhibited more pronounced effects in enhancing initial flame propagation and assisting to formation of stable flame nucleus which, in turn, extended the lean-burn limit substantially. Moreover, SHDI strategy also resulted in a more substantial improvement in mean effective pressure (IMEP) and brake thermal efficiency (BTE) compared to the HPI. However, emissions of NO X , HC and CO were higher in the SHDI mode as opposed to the HPI mode This disparity may be attributed to the elevated local temperatures in the vicinity of the spark plug and the interference caused by the hydrogen jet flow, which disrupted the in-cylinder flow pattern, consequently leading to increased levels of unburnt mixture. • A novel idea with hydrogen direct injected through a small hole on the spark plug edge (SHDI) was proposed. • An experimental study with the SDHI mode under lean-burn conditions was carried out on a GDI engine. • SDHI significantly improves BTE and reduces NO X emissions. • The effects of HPI and SHDI on GDI engines were analyzed comparatively. [ABSTRACT FROM AUTHOR]

The shortage of fossil energy and the aggravation of environmental pollution have led to stricter requirements for energy conservation and environmental protection of automobiles. The development of new energy vehicles still needs time and space. The internal combustion engine is still the power source that automobiles will need to rely on in the future. Lean combustion is one of the key research directions for efficient and clean combustion technology for gasoline engines. In this paper, the effects of high-energy ignition coupling hydrogen blending on the combustion stability of lean-burn gasoline engines were studied by means of multi-point high-energy ignition and gasoline/hydrogen double direct injection. Through the combination of gasoline and hydrogen injection timing, a suitable stratified mixture can be formed in the cylinder. Combined with high-energy ignition, the fire core can be formed smoothly, and the flame spreads rapidly. The introduction of hydrogen increases the concentration of H in the reaction system, enhances the activity of the reaction system, and accelerates the oxidation process of fuel molecules. Compared with a pure gasoline engine, hydrogen blending can expand the lean burn limit by 66.2% and increase ITE (Indicated Thermal Efficiency) by 6.5%. NO x emission increases first and then decreases with the increase in excess air ratio, but when λ > 1.6, NO x emission is much lower than that of the equivalence ratio condition. HC (Hydrocarbons), CO, and CO 2 emissions are also lower than the equivalent ratio conditions. • Multi-point high-energy ignition with three spark plugs. • Gasoline and hydrogen double direct injection to achieve lean combustion. • Effects on combustion and emission of lean burn gasoline engine. [ABSTRACT FROM AUTHOR]

Acceptance sampling plans based on the process yield indices have been adopted in the inspection of outgoing and incoming lots when the required fraction defective is very low. To achieve this aim and increase their overall efficiency and flexibility, various sampling plans have been constructed for different purposes using numerous methods. In practice, resubmitted sampling (RS) plan encourages suppliers to work harder to produce better quality products that pass the first inspection. Besides, the concept of switching inspection rules, which can provide a flexible sampling procedure and reducing the required sample size for inspection, is especially useful when the inspection is costly or destructive. This paper proposes integrated sampling plans by considering the merits of the process yield index Spk, RS, and switching inspection rules for controlling lot fraction nonconforming when the quality characteristic is normally distributed with two specification limits. The performance of the proposed plans is investigated and the results indicate a satisfactory performance of the proposed plans. Besides, the advantages of the proposed plans over the existing plans are discussed. Finally, real data from the spark plug industry are used to illustrate the implementation. [ABSTRACT FROM AUTHOR]

This paper explores pathways to achieve marine diesel-like, high-efficiency combustion fueled with propane in a RCEM research engine. Analyzing the novel technique of liquid propane injection is worthwhile given the potential for using propane in high-efficiency compression ignition engines. Since propane has a low cetane number, spark plug operating is provided to achieve reliable ignition. Investigations into combustion and the effect of spark discharge energy on propane direct injection were done through experiments on a modified head large bore RCEM with three spark ignition strategies and simulations. The findings demonstrate that the simultaneous ignition strategy had the greatest total released energy (roughly 190 mJ/s). When the SOI of the direct injection propane was set at 20oCA BTDC, diesel more efficiently than propane (on average, 3.46%). The benefits of the chosen strategy for achieving diesel efficiency parity were shown by the increasing of combustion efficiency when the spark period was lengthened. • In-cylinder combustion, performance characteristics and spark discharge energy were investigated. • Spark ignition was applied on RCEM research engine fueled with liquid propane direct injection. • Investigating the in-cylinder flow and velocity distribution around spark plug. • Spark plug ignition duration was investigated to achieve reliable ignition and reasonable ignition delays. • RCEM with spark produces high in-cylinder pressure when the SOI of liquid propane direct injection was set at 20 oCA BTDC. [ABSTRACT FROM AUTHOR]

Ammonia and hydrogen are two carbon-free alternative fuels for engines. Considering that there are few studies on improving an ammonia-hydrogen engine's lean combustion performance, this investigation based on an engine with the Miller cycle employs hydrogen direct injection (HDI) and NH 3 port injection and then proposes an adjustment strategy to vary the start of injection (SOI) of HDI for affecting the engine combustion process. When ammonia volume share (AVS) is greater than 50%, the engine shows poor performance. Nevertheless, the stratification effect of hydrogen jets may be used to elevate the hydrogen concentration around spark plug by properly delaying SOI and then creating the locally rich mixture with a high hydrogen share, which prominently promotes the flame kernel formation, shortens CA0-90, reduces C o V P m a x , and enables the engine to reach approximately 36% BTE. It is notable that very late SOI can slightly deteriorate the heat release process and lower engine performance. • Ammonia-hydrogen engines have poor combustion process under lean conditions. • A strategy to improve the lean combustion performance of the engine is proposed. • Effects of NH 3 –H 2 premixing and H 2 stratification effect on the engine are balanced. • Properly delaying SOI enhances the ignition and combustion process of the engine. [ABSTRACT FROM AUTHOR]

Despite the often outstanding functional as well as (high temperature‐) mechanical properties of ceramics, their usage is often limited due to their inherent brittleness. This also compromises the joining with metals, which is often indispensable for engineering applications. In this context, electrically conductive ceramics like MoSi2 are promising materials for the application as electrodes where high temperatures in harsh environments are present (e.g., in spark plugs for large gas engines). Due to the difficult joining of the respective materials, long‐term experiments are thereby often still pending. In this work, adhesive bonding, brazing, tungsten inert gas‐, and resistance welding were performed to evaluate their applicability for generating electrically conductive as well as mechanically reliable joints between MoSi2 and Inconel 600, aiming to utilize MoSi2 electrodes in spark plugs. Fractographic analyses are performed to understand cracks associated with the high (thermo‐) mechanical stresses. Additionally, a finite element model was set up for a deeper understanding of the observed fracture behavior. While adhesive bonding is acceptable for short‐term experiments at low temperatures, brazing and resistance welding may qualify for fast and reliable manufacturing of spark plugs with ceramic electrodes. [ABSTRACT FROM AUTHOR]

Several nitric oxide (NO) generating devices have been developed to deliver NO between 1 part per million (ppm) and 80 ppm. Although inhalation of high-dose NO may exert antimicrobial effects, the feasibility and safety of producing high-dose (more than 100 ppm) NO remains to be established. In the current study, we designed, developed, and tested three high-dose NO generating devices. We constructed three NO generating devices: a double spark plug NO generator, a high-pressure single spark plug NO generator, and a gliding arc NO generator. The NO and NO 2 concentrations were measured at different gas flows and under various atmospheric pressures. The double spark plug NO generator was designed to deliver gas through an oxygenator and mixing with pure oxygen. The high-pressure and gliding arc NO generators were used to deliver gas through a ventilator into artificial lungs to mimic delivering high-dose NO in the clinical settings. The energy consumption was measured and compared among the three NO generators. The double spark plug NO generator produced 200 ± 2 ppm (mean ± SD) of NO at gas flow of 8 L/min (or 320 ± 3 ppm at gas flow of 5 L/min) with electrode gap of 3 mm. The nitrogen dioxide (NO 2) levels were below 3.0 ± 0.1 ppm when mixing with various volumes of pure oxygen. The addition of a second generator increased the delivered NO from 80 (with one spark plug) to 200 ppm. With the high-pressure chamber, the NO concentration reached 407 ± 3 ppm with continuous air flow at 5 L/min when employing the 3 mm electrode gap under 2.0 atmospheric pressure (ATA). When compared to 1 ATA, NO production was increased 22% at 1.5 ATA and 34% at 2 ATA. The NO level was 180 ± 1 ppm when connecting the device to a ventilator with a constant inspiratory airflow of 15 L/min, and NO 2 levels were below 1 (0.93 ± 0.02) ppm. The gliding arc NO generator produced up to 180 ± 4 ppm of NO when connecting the device to a ventilator, and the NO 2 level was below 1 (0.91 ± 0.02) ppm in all testing conditions. The gliding arc device required more power (in watts) to generate the same concentrations of NO when compared to double spark plug or high-pressure NO generators. Our results demonstrated that it is feasible to enhance NO production (more than 100 ppm) while maintaining NO 2 level relatively low (less than 3 ppm) with the three recently developed NO generating devices. Future studies might include these novel designs to deliver high doses of inhaled NO as an antimicrobial used to treat upper and lower respiratory tract infections. • Development of three electrically generated high-dose nitric oxide devices. • Enhance nitric oxide production and maintain safe level of nitrogen dioxide. • Inhalation of high-dose nitric oxide to treat respiratory infections. [ABSTRACT FROM AUTHOR]

This study investigates the effect of misfire and postfire on backfire in a hydrogen-fuelled automotive spark ignition engine. Backfire is a preignition phenomenon and the flame propagates toward the engine's intake manifold during the suction stroke. Postfire is a post-ignition phenomenon occurring in the exhaust manifold during the exhaust stroke and the flame propagates towards the exhaust manifold or backflow to the combustion chamber or combined both. Misfire occurs when cranking the engine (starting), fouled spark plug, and unoptimized spark timing. Several misfire cycles lead to an increase in the accumulation of unburnt hydrogen-air charge inside the cylinder and 13% hydrogen leaves the exhaust manifold resulting in postfire occurrence in a subsequent cycle. The postfire in the current cycle acting as an external ignition source for the preignition of the accumulated hydrogen-air charge results in backfire in the immediate next cycle. The misfire, postfire and backfire stall the engine operation due to a drop in indicated mean effective pressure. The experimental data indicates the backfire limiting equivalence ratio (BLER) should decrease with an increase in the engine speed as the equivalence ratio varies from 0.91 at 2000 rpm to 0.4 at 4900 rpm. As too advancement of spark timing increases the probability of misfire leading to postfire and backfire, the engine must be operated at backfire limiting spark timing to avoid misfire, postfire, and backfire occurrence. An important point emerged from this study that misfire without postfire does not lead to backfire occurrence. Physical mechanisms and mitigative measures for misfire, postfire and backfire are discussed in detail. • Misfire occurs during cranking unoptimized spark timing and fouled spark plug. • Misfire leads to accumulation of unburnt hydrogen resulting in postfire. • Postfire in misfire cycle leads to backfire occurrence in the next cycle. • Too advanced spark timing increases probability of misfire, postfire and backfire. • BLER reduces from 0.91 to 0.4 as engine speed increases from 2000 to 4900 rpm. [ABSTRACT FROM AUTHOR]

The results of computer and physical simulation of discharge processes in a new type of pulseplasma ignition systems of gas turbine engines with a controlled switching spark gap are presented. A circuit design model of a pulse-plasma ignition system has been developed, which makes it possible to evaluate the regularities of discharge processes in a semiconductor spark plug depending on the parameters of the discharge circuits - the capacities of the high-voltage and low-voltage storage capacitors, the inductance of the main discharge circuit. The results of computer simulation are confirmed experimentally, the increased efficiency of the ignition system with a controlled spark gap compared to the known circuit solutions containing two switching spark gaps is substantiated. [ABSTRACT FROM AUTHOR]

The hydrogen-fueled Wankel rotary engine with excellent power and emission characteristic is under spotlight, while the leakage is still the major problem for Wankel rotary engine, especially the leading spark plug leakage. The peak pressure is increased from 3.34 MPa to 3.52 MPa and the indicated thermal efficiency reaches maximum value of 38.29% when the moving distance of leading spark plug is −6.5 mm, and the mass of leakage fresh mixture is reduced from 0.00311 g to 0 g. When leading spark plug is moved to minor axis, the flow field structure of working chamber is enhanced. However, the peak pressure and indicated thermal efficiency decrease when the moving distance of leading spark plug exceeds −6.5 mm. The excess leakage residual gas has negative effects on combustion. The optimum moving distance of leading spark plug is −6.5 mm at 3000 rpm with λ of 1.6. • The leakage mechanisms of spark plugs are analyzed. • The influence of leading spark plug location on gas leakage is analyzed. • The influence of leading spark plug location on combustion is analyzed. • The influence of leading spark plug location on flow field is analyzed. • The optimum location of leading spark plug is given. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional numerical model of a hydrogen direct-injection engine was established, and the combustion model was verified by experimental data. The influence of the injection timing and nozzle diameter on ultra-lean combustion was evaluated. The results suggest that, with the delay in the injection timing, the mixture concentration near the spark plug and combustion speed gradually increase. The maximum thermal efficiency increased from 47.44% to 49.87%. The combustion duration and ignition lag are shortened from 19.15°CA to 11.15°CA to 16.13°CA and 5.92°CA, respectively. As the nozzle diameter increased, the injection duration was shortened, and the mixture distribution area became more concentrated. Furthermore, under ultra-lean combustion, the combustion rate is more sensitive to the distribution of the mixture. Appropriately increasing the equivalence ratio near the spark plug can significantly shorten the ignition lag and combustion duration and obtain a higher thermal efficiency. • The laminar flame speed model of hydrogen is calibrated by experimental results. • The G-equation is used to simulation the hydrogen combustion. • The in-cylinder mixture distribution, hydrogen jet and flow field were investigated. • The maximum indicated thermal efficiency reaches 50.05%. [ABSTRACT FROM AUTHOR]

This paper analyses the influence of the type of electrode in a spark plug on exhaust gas emission. The objects of the research were the following vehicles of different years of production: the Volkswagen Beetle 1300, the Honda Nighthawk 650, the BMW e46 318i, the Hyundai i10, and the Audi A4 B6. The vehicles were powered by petrol and LPG. Spark plugs were selected for the vehicles, with different kinds of construction for the main electrodes and different numbers of poles but with similar heat values. A comparative analysis of the composition of the exhaust gas mixture was performed, depending on the set of spark plugs used. The amount of CO, HC, CO2, and O2 emissions was analysed. The results were compared with the applicable exhaust gas emission standards. Both in the case of E5 95 petrol and LPG gas, lower exhaust gas emissions were observed when iridium spark plugs were used. [ABSTRACT FROM AUTHOR]

This paper presents Unsteady Reynolds Averaged Navier Stokes (URANS) simulations of a large bore, hydrogen-fuelled direct injection spark ignition (DISI) engine at different spark and start of injection (SOI) timings. Six cases are simulated, including three with various spark timings at a low boost level and three with advanced to late injection timings at a higher boost level. The numerical simulations are validated with experimental data for four out of six cases, while the other two are considered blind computational fluid dynamics (CFD) simulations. It is shown that the autoignition occurs with advanced spark timing due to high in-cylinder pressure and unburnt temperature. For different SOIs, it is demonstrated that flame propagation involves a spark-initiated flame combined with an autoignition generated flame. The case with the late injection timing features poor mixing and slower combustion due to the presence of lean mixtures near the spark plug. As a result, this case features the lowest thermal efficiency when SOI is varied. In all cases, both mixture and temperature stratification are present. Simulations of zero-dimensional chemical reactors demonstrate that this stratification must be correctly captured for accurate prediction of autoignition timing. [ABSTRACT FROM AUTHOR]

The possibilities for reducing the fuel consumption of internal combustion engines focus mainly on developing combustion systems, as one such solution is a two-stage combustion system using jet ignition. The combustion of gaseous mixtures with a high excess air ratio leads to an increase in overall efficiency and a reduction in the emissions of selected exhaust components. In such a convention, gas combustion studies were conducted in the methane/propane configuration. Using an active prechamber where spark plugs were placed and direct injection through a check valve, the fuel dose was minimized into the prechamber. The tests were conducted for a constant center of combustion (CoC). The combustion process in both the prechamber and main chamber was analyzed using a test stand equipped with a 0.5 dm3 single-cylinder engine. The engine was controlled by varying the fuel supply to the prechamber and main chamber in excess air ratio λ = 1.3–1.8. The study analyzed thermodynamic indices such as the combustion pressure in both chambers, based on which the SoC in both chambers, the rate and amount of heat released, AI05, AI90 and, consequently, the indicated efficiency were determined. Based on the results, it was found that the use of CH4/C3H8 combination degraded the thermodynamic indicators of combustion more than using only the base gas (methane). In addition, the stability of the engine's operation was decreased. The advantage of using propane for the prechamber is to obtain more beneficial ecological indicators. For the single-fuel system, a maximum indicated efficiency of more than 40% was obtained, while with the use of propane for the prechamber, a maximum of 39.3% was achieved. [ABSTRACT FROM AUTHOR]

The following paper presents thermodynamic and optical investigations of hydrogen-enriched methane combustion, showing the potential of a hydrogen admixture as a means to decarbonize stationary power generation. The optical investigations are carried out through a fisheye optical system directly mounted into the combustion chamber, replacing one exhaust valve. All of the tests were carried out with constant fuel energy producing 16 bar indicated mean effective pressure. The engine under investigation is a port-fueled 4.8 L single-cylinder large-bore research engine. The test series compared the differences between a conventional spark plug and an unscavenged pre-chamber spark plug as an ignition system. The fuel blends under investigation are 5 and 10%V hydrogen mixed with methane and pure natural gas acting as a reference fuel. The thermodynamic results show a beneficial influence of the hydrogen admixture on both ignition systems and for all variations concerning the lean running limit, combustion stability and indicated efficiency, with the most significant influence being visible for the tests using conventional spark plugs. With the unscavenged pre-chamber spark plug and the combustion of the 10%V hydrogen admixture, an increase in the indicated efficiency of 0.8% compared to NG is achievable. The natural chemiluminescence intensity traces were observed to be predominantly influenced by the air–fuel equivalence ratio. This results in a 20% higher intensity for the unscavenged pre-chamber spark plug for the combustion of 10%V hydrogen compared to the conventional spark plug. This is also visible in the evaluations of the flame color derived from the dewarped combustion image series. The investigation of the torch flames also shows a difference in the air–fuel equivalence ratio but not between the different fuels. The results encourage the development of hydrogen-based fuels and the potential to store surplus sustainable energy in the form of hydrogen in existing gas grids. [ABSTRACT FROM AUTHOR]

The effect of two mechanisms that contribute to the cyclic variability of a spark-ignition (SI) engine fueled with lean methane–hydrogen blends was examined. This assessment was performed using a research computational fluid dynamics (CFD) code, employing a fast methodology that allowed the simulation of several cases (three per mechanism and per case) and thus greatly reduced the computational time. The first mechanism is related to the local gas turbulent properties at the spark plug, and the second mechanism is related to the fuel mass variation per cycle. The engine performance and emissions results were processed using a linear regression approach, and then using a Monte Carlo–based approach to extract the main indicators such as the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) for each individual mechanism as well as for their combination. It was found that the contribution of the first mechanism is significant and it mainly affects the initial flame propagation process. On the other hand, the second mechanism affects the equivalence ratio and subsequently the whole combustion process with a high variability of CO emissions, and its uncertainty was accounted for by expanding its range. [ABSTRACT FROM AUTHOR]

This research work is attempted to investigate the internal combustion characteristics which include combustion events using CH4 gases in a constant volume combustion chamber (CVCC). To visualize the flame event, the experiment via a high-speed camera shows the snapshot through quartz of internal walls. CH4 gases mixed with air are entered into a chamber via a mass flow controller. The ceramic capacitor is used to apply a plasma effect that can amplify the ignition spark in terms of current amperage. The specification of experimental compositions is set as 400 cc combustion chamber size, 1000 fps high speed camera, 15 ∼ 25 kV spark coil, 0.2 J amplified energy, 1000:1 high voltage probe, 0 ∼ 160 bar pressure sensor, 0 ∼ 15 l/m MFC, 150 bar check valve, and 12.5 V battery. Particularly, the maximum pressure of combustion is highly increased by 1 bar in a plasma plug model. As to an exhaust gas result, CO2 and NOx in a plasma plug model are partially increased rather than in a conventional plug model. On the other hand, CO and HC are shown that in a conventional plug model, exhaust gas amount is increased than in a plasma plug model. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of piston geometry design and spark plug position on the engine performance and emission characteristics at a range of speeds from 1200 rpm to 2200 rpm. Accordingly, the parameters of the indentation depth, the spark plug position, the location of the recess, and the engine's compression ratio are changed and evaluated. The concave center depth improved the mixture of air and fuel, increased power, and reduced fuel consumption. The power can be improved by up to 3% when the piston top recess is 25 mm. In addition, within a limited range, the combustion process and the engine's power and emission characteristics are enhanced when the engine's compression ratio rises. Increasing the depth of the depression on the top of the piston improves fluid flow in the cylinder, resulting in increased power, fuel efficiency, and emissions; however, the improvement between the indentations remains unclear. [ABSTRACT FROM AUTHOR]

The spark plug of an opposed‐piston two‐stroke (OP2S) gasoline engine is arranged on the side wall of the cylinder liner, far from the center of the combustion chamber; the ignition core of the mixture is offset, the flame propagation distance is increased, the combustion duration is prolonged, and the knock tendency is severe. In this paper, a quasi‐dimensional two‐zone combustion model is used in GT‐Power software to establish a thermodynamic process simulation model and a knock prediction model is included to analyze the effect and matching of the compression ratio, ignition timing, and other thermodynamic process parameters on the knock intensity and engine performance. The extended coherent flame model combustion model is coupled with the Huh–Gosman spray model in AVL‐Fire software, and the An B knock model is used to establish an in‐cylinder combustion model and analyze the flame propagation and the knock response rate of the flat and pit piston during the combustion process. With an increase of the compression ratio, the temperature and pressure of the mixture in the combustion chamber increase at the time of ignition, which leads to the knocking combustion in the cylinder. With an increase of the ignition advance angle, the in‐cylinder pressure and temperature increase rapidly, which increases the likelihood of knocking combustion. In comparison with the pit piston combustion chamber, the flame propagation speed of the flat piston combustion chamber is relatively slow, which increases the knock tendency. The results show that lowering the compression ratio and delaying the ignition can reduce the in‐cylinder knock tendency by setting a compression ratio of 10.5 and an ignition advance angle of 20°CA. When the pit piston is used to organize the squish and inverse squish before and after the inner dead center, the flame propagation process can be promoted. The knock response rate of pit piston is 24.7% lower than that of flat top piston. [ABSTRACT FROM AUTHOR]

In this study, the effect of intake manifold geometry on cylinder-to-cylinder variation was investigated considering the volumetric efficiency, early tumble development, turbulent kinetic energy, and spark plug gap velocity using computational fluid dynamic program, CONVERGE v2.4. The simulation model was validated based on the PIV experiment in the cylinder and Mie-scattering experiment of intake manifold, and its results agreed well with the experiment results. The curved intake manifold and straight manifold were compared. As a result, it was advantageous for cylinder-to-cylinder variation in the straight intake manifold compared to the curved intake manifold in perspective of volumetric efficiency which were a maximum deviation of 1.7% in curved manifold and 0.6% in straight manifold. And the straight manifold had an effect of the strengthening the in-cylinder flow, so that the turbulent kinetic energy near TDC was increased to maximum 11% than curved manifold. And considering the effect of manifold curve radius on in-cylinder flow intensity in straight manifold, with increasing engine speed, the in-cylinder flow intensified during compression with decreasing the intake manifold radius due to the short distance between manifold inlet and port. Especially at 2000 rpm, the tumble ratio increased 55% at intake manifold radius of 10 cm than of 7 cm at bTDC 280 deg. Therefore, for the purpose of enhancing the in-cylinder flow near spark plug timing, shortened distance between intake manifold inlet and port and increasing the manifold radius is required. [ABSTRACT FROM AUTHOR]

The paper deals with the experimental study of a medium-load spark ignition engine under operation with different fuel mixtures among those deemed as promising for the transition towards carbon-free energy systems. In particular, the performance of a non-conventional ignition system, which permits the variation of the ignition energy, the spark intensity and duration, was studied fuelling the engine with 60–40% hydrogen–methane blends, three real syngas mixtures and one biogas. The paper is aimed to find the optimal ignition timing for minimum specific fuel consumption and the best setup of the ignition system for each of the fuel mixtures considered. To this end, a series of steady-state tests were performed at the dynamometer by varying the parameters of the ignition system and running the engine with surrogate hydrogen–methane–nitrogen mixtures that permit the simulation of hydrogen–methane blends, real syngas, and biogas. The results quantify the increase of spark advance associated with the decrease of the fuel quality and discuss the risk of knock onset during methane–hydrogen operation. It was demonstrated that the change of the ignition system parameters does not affect the value of optimum spark advance and, except for the ignition duration, all the parameters' values are generally not very relevant at full load operation. In contrast, at partial load operation with low-quality syngas or high exhaust gas recirculation rate, it was found that an increase of the maximum ignition energy (to 300 mJ) allows for operation down to approximately 66% of the maximum load before combustion becomes incomplete. Further reductions, down to 25% of the maximum load, can be achieved by increasing the gap between the spark plug electrodes (from 0.25 to 0.5 mm). [ABSTRACT FROM AUTHOR]

Dual‐fuel mode internal combustion engines need perfect conditions to ignite the mixture of air and fuel without the use of a spark plug. A perfect mixture of fuel and air is essential for the most effective ignition, and this is a technical challenge. Ignition systems have been developed for use in internal combustion engines. Structural aspects of advanced combustion technology engines like compression ratio, exhaust gas recirculation rate, fuel ratio, and piston bowl geometry can influence heat regulation during the combustion process, increase the load range of the engine and reduce the formation of NOx, soot, and other emissions formed during the combustion process. This article shows how such an engine could be constructed. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The generator is the most popular mobile power device and backup power device in the world. It is very important for human life. Therefore, it is important to develop more efficient combustion technology in order to save energy and reduce air pollution. In this paper, a novel technology of hydrogen and oxygen compound gasoline fuel is developed. Hydrogen and oxygen gases are produced from an electrolytic cell and then mixed with the intake gasoline and air. The compound fuel is sucked into the engine combustion chamber. The hydrogen and oxygen gases can be produced immediately without any storage device of hydrogen. The experimental results show that this technology can increase the power generation and decrease emission pollution due to promoting combustion efficiency. In addition, the spark plug seat temperature increases due to higher heat value of hydrogen. This technique can reduce carbon monoxide and HC, but increase carbon dioxide. The research and development of this technique can achieve the goals of energy saving, emission reduction, relative safety, easy refitting and low refitting expense. Moreover, this research possesses academic innovation and industrial application. [ABSTRACT FROM AUTHOR]

• Role of hydrogen/ammonia ratio and equivalence ratio in jet ignition is identified. • The high hydrogen/ammonia ratio enhances ignition by improving mixture reactivity. • As hydrogen/ammonia ratio increases from 0 % to 20 %, ignition delay decreases by 70 %. • Equivalence ratio seriously affects ignition and flame expansion under lean-burning. Ammonia-hydrogen blend fuels offer the potential for zero-carbon emissions in internal combustion (IC) engines. To improve combustion performance, considerable attention has been focused on pre-chamber jet ignition technologies. Passive pre-chamber featuring a simple structure can be installed in the spark plug hole without modifying the cylinder head. However, the jet ignition characteristics of ammonia-hydrogen passive pre-chambers are not fully understood, and there is a lack of visualized evidence on how critical parameters (e.g., equivalence ratio and hydrogen/ammonia ratio) impact ignition processes. This work investigated the effects of equivalence ratio and hydrogen/ammonia ratio on ammonia-hydrogen jet ignition characteristics in a rapid compression machine with passive pre-chamber. High-speed photography and instantaneous pressure acquisition were employed to capture detailed ignition and combustion evolutions. Results show that under low hydrogen/ammonia ratio conditions, there exists a combustion regime with noticeable fluctuations in jet penetration, indicating degenerate ignition performance. As the hydrogen/ammonia ratio increases from 0 % to 20 %, the ignition delay time of mixtures in the main chamber is reduced by 70 %, suggesting an improved overall ignition performance. Regarding the equivalence ratio, more pronounced effects on jet ignition and flame propagation are identified under lean-burning conditions. For mixtures at the hydrogen/ammonia ratio of 20 %, as the equivalence ratio increases from 0.6 to 0.8 and from 0.8 to 1.0, the decay rates for 10 %–90 % combustion duration are 82.5 % and 20.6 %, respectively. Besides, with the increase of equivalence ratio, flame initiation is shifted from the jet head to the side surface. The role of hydrogen/ammonia ratio and equivalence ratio is different, with the former modifying mixture reactivity while the latter affecting ignition energy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigation of the combination of NRPD ignition and TJI. • Five different combustion strategies are investigated on the same engine with NRPD ignition and compared against an inductive discharge ignition system. The combustion strategies are passive Pre-Chamber (PC) with air and EGR dilution, active PC with air dilution, and Open Chamber (OC) with air and EGR dilution. • In the OC, the use of NRPD ignition leads to faster inflammation. At dilution levels above peak efficiency, the efficiency using NRPD ignition decreases at a slower pace, demonstrating its potential to tolerate higher AFR and EGR rates. • In the PC using NRPD ignition, an efficiency increase and a reduction of emissions compared to inductive discharge ignition are present thanks to a stronger pre-chamber discharge and a faster end phase of combustion. • Passive PC with NRPD ignition seems to be the ideal ignition concept that maximizes engine efficiency and minimizes emissions. Robust ignition of hard-to-ignite fuels is essential for future spark ignited internal combustion engines, particularly for introducing efficiency-enhancing diesel-like process parameters like air excess or high amounts of exhaust gas recirculation (EGR). On the one hand, novel plasma-based ignition systems like Nanosecond Repetitively Pulsed Discharge (NRPD) are promising in extending the ignition limits and the early flame development speed. On the other hand, Turbulent Jet Ignition is effective for shortening the combustion duration and decreasing the unburned hydrocarbon emissions. This article investigates experimentally the combination of NRPD ignition and TJI. The aim is to use a technology for robust inflammation (NRPD) in combination with a technology for fast combustion of the bulk charge (TJI). For this purpose, a turbocharged light-duty four-cylinder engine operated with natural gas is used. The engine can be fitted with a classical Open Chamber (OC) spark plug or with Pre-Chambers (PC). The PCs can be filled uniquely with fuel and air coming from the Main Chamber (MC) ("passive PC"), or additional fuel can be added to the PCs ("active PC"). The air-to-fuel ratio and EGR rate can be freely controlled. Five different combustion strategies are investigated with NRPD ignition and compared against an inductive discharge ignition system. The combustion strategies are passive PC with air and EGR dilution, active PC with air dilution, and Open Chamber (OC) with air and EGR dilution. HRR evaluations and a loss analyses are performed to interpret the results. Despite the faster inflammation present with NRPD ignition, similar peak efficiencies and emissions are reached in OC configuration using the inductive discharge and NRPD ignition systems, which are achieved by varying air-to-fuel ratios (AFR) and EGR rates. Above dilution levels for peak efficiency, the efficiency using NRPD ignition decreases at a slower pace and tolerates higher AFR and EGR rates, thanks to a more complete and shorter combustion. For the PC experiments using NRPD ignition, an efficiency increases and a reduction of emissions compared to inductive discharge ignition are present for the investigated AFR and EGR rates for both active and passive PC operations. The efficiency increase is present due to a stronger pre-chamber discharge and thanks to a faster end phase of combustion. Actively fueling the PC results in faster and more complete combustion that is overcompensated by the increased wall heat losses, reducing the overall efficiency. The results show that passive PC with NRPD ignition may be an ideal ignition concept that maximizes engine efficiency and minimizes emissions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new combustion strategy of turbulent jet-post spark ignition (TJ-PSI) is proposed. • TJ-PSI significantly enhances the combustion intensity of premixed ammonia/air mixture. • TJ-PSI strategy presents a more pronounced enhancement at elevated pressures. Ammonia is carbon free, while its low flame speed limits its applications in engines. This study aims to enhance ammonia combustion using pre-chamber turbulent jet combined with post spark ignition (TJ-PSI) strategy. The experiments are performed in a constant-volume combustion vessel, with one spark plug installed in the pre-chamber and the other spark plug placed in the downstream region of the pre-chamber turbulent jet. For the TJ-PSI mode, the spark plug in the pre-chamber is first triggered while the jet flame is quenched when passing through the nozzle orifice, and the mixture is ignited by the following post spark ignition in the main chamber. With premixed stoichiometric ammonia/'air' mixtures, the combustion characteristics of the TJ-PSI strategy and spark ignition strategy are compared. The experimental results show that the TJ-PSI strategy can significantly increase the heat release rate of the premixed ammonia/'air' mixture while maintaining higher combustion efficiency, with the combustion duration decreased by 69% maximum. Schlieren images show that the turbulence caused by jet ejection can enhance ammonia combustion. Meanwhile, the effects of time interval between two spark ignitions, and initial mixture pressure on the combustion characteristics are also investigated. The experimental results show that the time interval has a significant effect on the combustion process. The spark ignition that occurs during the jet ejection duration can lead to extinction of the ignition kernel due to the strong turbulent jet, while over extended time intervals shows a smaller enhancing effect. With increased pressure, TJ-PSI strategy shows a more significant enhancing effect. [ABSTRACT FROM AUTHOR]

High-speed schlieren visualization on the initiation process of non-premixed air and hydrogen continuous rotating detonation (CRD) is carried out in a well-designed rounded-rectangle hollow combustor in this study. The CRD initiation processes of pre-detonator ignition and spark plug ignition are comprehensively revealed by synchronous high-speed schlieren images and high-frequency dynamic pressure results. The results show that the CRD undergoes three processes after ignition, including initiation process, adjustment process and stable propagation process. The CRD initiation process of pre-detonator ignition involves the upstream-propagation phase of leading shock wave and reaction zone and the coupling phase of circumferentially-propagating shock wave and reaction zone, while that of spark plug ignition includes the upstream-propagation phase of reaction zone, and the coupling phase of circumferentially-propagating pressure wave and reaction zone. The formation of deflagration combustion flowfield and re-establishment of combustible mixture layer after ignition are important prerequisites for CRD initiation. The strong interaction between circumferentially-propagating shock wave and post-shock wave reaction conduces to the rapid initiation of CRD by pre-detonator ignition, while the pressure wave gradually interacts with reaction leading to the detonation initiation by spark plug ignition. The CRD initiation time and adjustment time of pre-detonator ignition are shorter than those of spark plug ignition. This study provides detailed insight into the physics of CRD initiation process of pre-detonator and spark plug ignition, which can deepen the understanding of the initiation mechanism and provide practical guidance for the optimal design of CRDE ignitor. [ABSTRACT FROM AUTHOR]

This work presents a multiscale modeling framework for predictive simulations of shock-to-detonation transition (SDT) in pressed energetic (HMX) materials. The macro-scale computations of SDT are performed using an ignition and growth (IG) model. However, unlike in the traditional semi-empirical ignition-and-growth model, which relies on empirical fits, in this work meso-scale void collapse simulations are used to supply the ignition and growth rates. This results in a macro-scale model which is sensitive to the meso-structure of the energetic material. Energy localization at the meso-scale due to hotspot ignition and growth is reflected in the shock response of the energetic material via surrogate models for ignition and growth rates. Ensembles of meso-scale reactive void collapse simulations are used to train the surrogate model using a Bayesian Kriging approach. This meso-informed Ignition and Growth (MES-IG) model is applied to perform SDT simulations of pressed HMXs with different porosity and void diameters. The computations are successfully validated against experimental pop-plots. Additionally, the critical energy for SDT is computed and the experimentally observed P s 2 τ s = constant relations are recovered using the MES-IG model. While the multiscale framework in this paper is applied in the context of an ignition-and-growth model, the overall surrogate model-based multiscale approach can be adapted to any macro-scale model for predicting SDT in heterogeneous energetic materials. [ABSTRACT FROM AUTHOR]

In general, as compared to conventional combustion engines, the homogeneous charge compression ignition (HCCI) engine offers better fuel efficiency, NOx, and particulate matter emissions. The HCCI engine, on the other hand, is not connected to the spark plugs or the fuel injection system. This implies that the auto-ignition time and following combustion phase of the HCCI engine are not controlled directly. The HCCI engine will be confined to a short working range due to the cold start, high-pressure rate, combustion noise, and even knocking combustion. Biofuel innovation, such as ethanol-powered HCCI engines, has a lot of promise in today's car industry. As a result, efforts must be made to improve the distinctive characteristics of the engine by turning the engine settings to different ethanol mixtures. This study examines the aspects of ethanol-fueled HCCI engines utilizing homogenous charge preparation procedures. In addition, comparing HCCI engines to other advanced combustion engines revealed their increased importance and prospective consequences. Furthermore, the challenges of transitioning from conventional to HCCI engines are examined, along with potential answers for future upgrade approaches and control tactics. [ABSTRACT FROM AUTHOR]

The amount of silicon in naphtha must be controlled because it results in silica deposits in vehicle components, such as spark plugs, catalytic converters, and oxygen sensors, which can lead to fuel economy degradation, increased emissions, and damage to catalytic converters. Naphtha has low specific gravity and high volatility; plasma does not form during analysis using inductively coupled plasma-optical emission spectrometry. Therefore, the analysis of silicon in naphtha has been conducted using a dilution method with organic solvents. On the other hand, a high dilution factor increases the LOQ (limit of quantitation), making it difficult to analyse below 100 ppb. In this study, propylene glycol monomethyl ether acetate (PGMEA) was used to solve this problem because it has excellent naphtha solubility, low volatility, and is used widely in semiconductor processing. A LOQ and LOD (limit of detection) of up to 3.3 ppb and 1.0 ppb, respectively, could be achieved using a concentration method by diluting naphtha in PGMEA and heating it. In addition, the reference materials were prepared with octamethylcyclotetrasiloxane to ensure analysis accuracy; excellent results were obtained with an 88% recovery rate. [ABSTRACT FROM AUTHOR]

Upcoming gasoline engines should run with a larger number of fuels beginning from petrol over methanol up to gas by a wide range of compression ratios and a homogeneous charge. In this article, the microwave (MW) spark plug, based on a high-speed frequency hopping system, is introduced as a solution, which can support a nitrogen compression ratio up to 1:39 in a chamber and more. First, an overview of the high-speed frequency hopping MW ignition and operation system as well as the large number of applications are presented. Both gives an understanding of this new base technology for MW plasma generation. Focus of the theoretical part is the explanation of the internal construction of the spark plug, on the achievable of the high voltage generation as well as the high efficiency to hold the plasma. In detail, the development process starting with circuit simulations and ending with the numerical multiphysics field simulations is described. The concept is evaluated with a reference prototype covering the frequency range between 2.40 and 2.48 GHz and working over a large power range from 20 to 200 W. A larger number of different measurements starting by vector hot- $S_{11}$ measurements and ending by combined working scenarios out of hot temperature, high pressure and charge motion are winding up the article. The limits for the successful pressure tests were given by the pressure chamber. Pressures ranged from 1 to 39 bar and charge motion up to 25 m/s as well as temperatures from 30° to 125°. [ABSTRACT FROM AUTHOR]

An experimental study of the ignition and combustion of a combustible propane–air mixture is carried out. The efficiency of two systems for igniting a combustible gas mixture is compared: a traditional technology using conventional spark plugs and a new system based on initiated streamer microwave discharges. The design features of a setup for creating and studying a multifocal microwave discharge system are described. The results of studies of the new microwave system for ignition of the fuel mixture are presented, which are compared with the data of the ignition system based on different numbers of spark discharges. The results of comparative analysis of the two ignition systems are presented for different initial pressures in the combustion chamber and fuel mixture compositions. [ABSTRACT FROM AUTHOR]

The use of ion current signals generated during the combustion process of mixed gas as a function of initial mixture composition, temperature and pressure to detect cylinder combustion states is the most recent approach in the design, development, and optimisation of automotive engine combustion control. This paper aims to design predictive identification and computationally fast and accurate ion current models for obtaining combustion information in the engine cylinder in real time. To build a more comprehensive ion current calculation model, the effect of the flame ionisation process, the geometry of the spark plugs, and the combustion pressure and temperature are considered in the new building ion current model. The simulation ion current waveform, which has a double-peak structure, is in good agreement with the experiment values; thus, the ion current model has the potential to be used for real-time control and optimisation of engine cylinder combustion. [ABSTRACT FROM AUTHOR]

The objective of this study is to apply an improved Faster-RCNN model in order to solve the problems of low detection accuracy and slow detection speed in spark plug defect detection. In detail, an attention module based symmetrical convolutional network (ASCN) is designed as the backbone to extract multi-scale features. Then, a multi-scale region generation network (MRPN), in which InceptionV2 is used to achieve sliding windows of different scales instead of a single sliding window, is proposed and tested. Additionally, a dataset of X-ray spark plug images is established, which contains 1,402 images. These images are divided into two subsets with a ratio of 4:1 for training and testing the improved Faster-RCNN model, respectively. The proposed model is transferred and learned on the pre-training model of MS COCO dataset. In the test experiments, the proposed method achieves an average accuracy of 89% and a recall of 97%. Compared with other Faster-RCNN models, YOLOv3, SSD and RetinaNet, our proposed new method improves the average accuracy by more than 6% and the recall by more than 2%. Furthermore, the new method can detect at 20fps when the input image size is 1024×1024×3 and can also be used for real-time automatic detection of spark plug defects. [ABSTRACT FROM AUTHOR]

The spark ignition (SI)-controlled auto-ignition (CAI) hybrid combustion is characterized by early flame propagation combustion and subsequent auto-ignition combustion. The application of combined SI–CAI hybrid combustion can be used to effectively extend the operating range of CAI combustion and achieve smooth transitions between SI and CAI combustion modes. However, SI–CAI hybrid combustion can produce significant cycle-to-cycle variations (CCV). In order to better understand the sources of CCV and minimize its occurrence, the large eddy simulation (LES) and Reynolds-averaged Navier–Stokes (RANS) approaches were employed in this study to model and understand the cyclic phenomenon of SI–CAI hybrid combustion. Both the multi-cycle LES and RANS simulations were analyzed against the experimental measurements in a single cylinder engine at 1500 rpm and a 5.43 bar average indicated the mean effective pressure (IMEP). The detailed analysis of the in-cylinder pressure traces, IMEP, in-cylinder peak pressure (PP), peak pressure rise rate (PPRR) and the crank angles with fuel mass burned fraction at 10%, 50%, 90% and mode transition was performed. The results indicate that overall, the adopted LES simulations could effectively predict the cyclic variations in the hybrid combustion observed in the experiments, while the RANS simulations failed to reproduce the cyclic characteristics at the chosen engine operating conditions. Based on the LES results, the correlation and visualization studies indicate that the cyclic variations in the local velocity around the spark plug lead to the variations in the early flame propagation, which in turn produce temperature fluctuations among the cycles and result in greater variations in the subsequent auto-ignition combustion events. [ABSTRACT FROM AUTHOR]

Failure mode and effects analysis (FMEA) is an effective risk assessment tool for detecting and reducing possible risks during a manufacturing process. However, traditional FMEA has some shortcomings when used in the real world. In recent years, improved FMEA approaches have been proposed to eliminate the inherent shortcomings of FMEA, but the risk ranking result obtained from those FMEA approaches may be inconsistent. Therefore, this paper integrates six FMEA approaches by using an ensemble learning technique to obtain comprehensive and reliable rankings for failure modes. Data from the assembly process of spark plugs are used to check the performance of the proposed method. Meanwhile, a comparation is designed to illustrate that the proposed FMEA method can not only obtain reliable results, but also provide meaningful management insights for practitioners. [ABSTRACT FROM AUTHOR]