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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]

A pulsed detonation chamber (PDC) equipped with Hartmann–Sprenger resonators has been designed and tested for both Hydrogen/air and Hydrogen/Oxygen mixtures. A full-factorial experimental campaign employing four factors with four levels each has been carried out for both mixtures. Instantaneous static pressure has been measured at two locations on the exhaust pipe of the PDC, and the signal has been processed to extract the average and maximum cycle pressures and the operating frequency of the spark plug. The PDC has been shown to be able to reach sustained detonation cycles over a length below 200 mm, measured from the spark plug to the first pressure sensor. The optimal regimes for both air and Oxygen operation have been determined, and the influence of the four factors on the responses is discussed. [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]

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The main objective of the research is to assess the influence of the spark plug electrodes geometry on the structure of the electric arc. This issue is increasingly important in modern gas-fueled engines with lean and stratified air-gas mixtures. To explain the influence of electrode geometry on selected spark discharge indicators, optical tests were conducted, and the parameters of the test history, together with the movies of the discharging process, were recorded and analyzed. The tests were carried out comparatively for two types of spark plugs on the test stand: conventional spark plug and spark plug with a flat ground electrode. It has been found that using flat plug electrodes allows a larger spark area covered by the electric arc without losing the intensity of radiation. More, using an unconventional spark plug results in a shorter discharge time relative to the conventional spark plug, while the geometry of the conventional spark plug allows for maintaining a stable electric arc with a minimum tendency for creeping. [ABSTRACT FROM AUTHOR]