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In this study, the effect of injection strategy on the mixture formation and combustion in a hydrogen direct injection engine using CFD analysis was investigated. Four Start of Injection timings and three types of injection rate were used to understand how the fuel and air mixing process and fuel distribution at the spark timing affect the start of combustion and flame propagation. The results shows that injection timing and rate shape significantly influence the formation of the fuel–air mixture and the subsequent combustion process. Uneven mixture formations from direct injection necessitate careful consideration of local equivalence ratios around the spark plug to ensure efficient combustion initiation and flame propagation. [ABSTRACT FROM AUTHOR]

The reduction of greenhouse gas emissions and the effort of carbon neutrality require the improvement of spark-ignition engines in terms of efficiency and capability to operate on renewable fuels. The electrode wear of spark plugs, used for ignition of novel fuels and lean mixtures, emerges as a significant challenge in this transition. Understanding the physical mechanism and influence of spark operation parameters of the wear process is thus important. Compared to the conventional methodology of performing long-term wear tests, laser-based optical diagnostics methods are capable of assessing electrode wear during one single or a few spark discharges. In this work, the necessary initial steps required for performing optical investigations using laser-induced fluorescence (LIF) are presented. Several excitation pathways of nickel atoms were investigated, and 336.96 nm was identified as the optimal one. This excitation approach yielded emissions between 338.75 and 353.58 nm, effectively avoiding the major interference from N2 plasma emission in spark discharges. Additionally, a linear relationship in fluorescence signal intensity with excitation energy up to 400 µJ was observed. These findings indicate the potential of LIF for in situ diagnostics of electrode wear, contributing to engine development in both efficiency and compatibility with sustainable fuels. [ABSTRACT FROM AUTHOR]

Methanol can be synthesized using green electricity and carbon dioxide, making it a green, carbon-neutral fuel with significant potential for widespread application in engines. However, due to its low ignition energy and high laminar flame speed, methanol is susceptible to hotspot-induced pre-ignition and even knocking under high-temperature, high-load engine conditions, posing challenges to engine performance and reliability. This paper systematically reviews the manifestations and mechanisms of pre-ignition and knocking in methanol engines. Pre-ignition can be sustained or sporadic. Sustained pre-ignition is caused by overheating of structural components, while sporadic pre-ignition is often linked to oil droplets entering the combustion chamber from the piston crevice. Residual exhaust gas trapped within the spark plug can also initiate pre-ignition. Knocking, characterized by pressure oscillations, arises from the auto-ignition of hotspots in the end-gas or, potentially, from deflagration-to-detonation transition, although the latter requires further experimental validation. Factors influencing pre-ignition and knocking, including engine oil, in-cylinder deposits, structural hotspots, and the reactivity of the air–fuel mixture, are also analyzed. Based on these factors, the paper concludes that the primary approach to suppressing pre-ignition and knocking in methanol engines is controlling the formation of pre-ignition sources and reducing the reactivity of the air–fuel mixture. Furthermore, it addresses existing issues and limitations in current research, such as combustion testing techniques, numerical simulation accuracy, and the mechanisms of methanol–oil interaction, and offers related recommendations. [ABSTRACT FROM AUTHOR]

The article "Lineages and Mental Powers" by Joseph Vukov and Charles Lassiter, published in the Review of Metaphysics, explores the concept of a "Culture of Honor" in the American South, which influences higher homicide rates in the region. The authors delve into the historical development of mental powers, proposing a theory that powers have lineages that are essential for understanding differences in powers. They argue that lineages are individuating of powers, shaping their manifestation complexes and influencing future possibilities. The article critiques the Humean model of lineages and advocates for the inclusion of lineages in the Standard View to provide a more comprehensive metaphysical account of powers. [Extracted from the article]

The increase in the number of motor vehicles in Indonesia has a significant impact on increasing exhaust emissions that contribute to air pollution. One way to reduce these emissions is through optimizing the combustion process by using variable spark plugs and remapping the ECU (Electronic Control Unit). This study aims to analyze the effect of the use of standard, platinum, and iridium spark plugs, as well as ECU remap at 5° and 10° ignition angles on the exhaust emissions of Vario 125 cc motorcycles. The research method used is an experiment with a pre-test and post-test research design. The test was carried out on three spark plug variations (standard, platinum and iridium) with ignition at angles of 5° and 10°. The testing process involves measuring exhaust emissions, specifically carbon monoxide (CO) and hydrocarbons (HC), at four engine rev levels (rpm) of 1500, 2000, 2500, and 3000. The data was obtained using a gas analyzer and analyzed using mean statistics and percentage of change. The results showed that the use of platinum and iridium spark plugs significantly reduced CO and HC emissions compared to standard spark plugs. At 10° ignition with an iridium spark plug, the largest difference in CO was recorded at 2500 rpm with 23.12%, while the highest HC difference was at 2000 rpm with 37.67%. Platinum spark plugs also provide quite good results with consistent reductions in CO and HC emissions. Remap ECUs with an ignition angle of 10° have proven to be more effective in reducing exhaust emissions compared to 5° ignition. [ABSTRACT FROM AUTHOR]

Gasoline SI-CAI combustion has shown its advantages in expanding the operating range of high-efficiency combustion. However, the high cyclic variation occurs since the presence of exhaust gas limits the spark ignition and its controllability by auto-ignition. To further improve the stability and reliability of hybrid combustion, MFI (Micro Flame Ignition) strategy has been proposed. Although the phenomenon of MFI hybrid combustion was learned before, the chemical effect of high-activity fuel DME (Dimethyl Ether) and its inter-reaction with gasoline to the combustion process has yet to be studied. In this paper, the carbon tracer method was used to separate the reaction of DME and gasoline in CFD (Computational Fluid Dynamics) simulation, and chemical reaction kinetic analysis was carried out. The congregate DME could produce formaldehyde by 2-step oxidation of DME spontaneously, which led to a high flame speed than the spark ignition. The discrete MFI strategy showed a two-times flame speed ignited by the spark plug, which led to the mid-product of gasoline enhancing the first step of DME oxidation. Although the discrete DME showed high chemical activity in the whole cylinder, the high temperature and pressure caused by DME's auto-ignition led to a shorter ignition delay for the auto-ignition process in the congregate MFI strategy. [ABSTRACT FROM AUTHOR]

In this study, the split-channel supercharge and fuel-air mixing technology (SCS-FAM) is firstly proposed for large-bore ammonia (NH 3)-hydrogen (H 2) engine, which involves the separation of fuel and air intake ports to mitigate the risk of H 2 backfire in intake system. We explored the activity stratification under different intake schemes and H 2 blend ratios through simulation, as well as how it affects the NH 3 –H 2 combined combustion characteristics including in-cylinder flow turbulence, temperature, concentration, and key intermediates distribution. The results show that in Scheme 2 when air entered the high swirl ratio intake 1 and fuel entered the low swirl ratio intake 2, a rich mixture was formed near the spark plug, accompanied by localized NH 3 thermal reforming phenomena, which improved the activity distribution of H 2. Additionally, the strong swirl promoted combustion in the squish zone and significantly shortened the post-combustion period. Scheme 2 achieved a higher indicated thermal efficiency (ITE) than Scheme 1 with a small amount of H 2 addition, with the highest ITE of 42.1% obtained at 15 vol% H 2 blend ratio. Notably, the addition of H 2 promoted NH 3 consumption and the generation of active radicals, resulting in reduced N 2 O emissions during the expansion stroke, but causing an increase in NO emissions. • Split-channel supercharge and fuel-air mixing technology is proposed to prevent H 2 backfire. • Different NH 3 –H 2 blend mixtures are compared and higher thermal efficiency is reached by lower H 2 fraction. • The localized ammonia-rich auto-thermal reforming improves the activity distribution of NH 3 –H 2 mixture. • Improved in-cylinder swirl could enhance the flame propagation in squish zone and reduce post-combustion. [ABSTRACT FROM AUTHOR]

Large gas engines are typically applied to compensate for peak loads and grid instabilities in the electric power supply. A key component of these engines is the spark plug. Because of the harsh conditions encountered in their use, the spark plug electrodes are subject to significant wear. Conventional electrodes are expensive due to the precious metal alloys they contain. As an alternative, ceramic materials from the groups of silicide, carbides, and nitrides were selected for preliminary experiments that investigate functional as well as mechanical properties and wear behavior. Because of the harsh conditions during operation, the new materials must have a high melting temperature, good thermal shock resistance, high thermal conductivity, and high corrosion/oxidation resistance as well as high density. It was found that the mechanical and thermomechanical properties of certain ceramic candidates are sufficient for application as spark plug electrodes. Furthermore, the chosen ceramic materials achieve an adequate performance in terms of secondary voltage trace and ignition behavior. However, wear resistance may not be sufficient for service times longer than the service time of existing spark plugs and further research is still necessary before ceramic electrodes may be established as a commercial alternative to existing electrodes. [ABSTRACT FROM AUTHOR]

Multi-cycle large eddy simulations were conducted to resolve the turbulent flow field spatially and temporally in a pre-chamber ignited gasoline engine. The numerical models were validated by comparing with both the passive and active pre-chamber experimental data. Correlation analysis results of the two pressure peaks during combustion inside the pre-chamber showed that the combustion inside the pre-chamber directly influences the timing and strength of the turbulent jets, which would ignite the mixture inside the main chamber. Then, the flow field evolution and fuel/air mixture formation inside both the main chamber and pre-chamber during intake and compression strokes were investigated numerically. Results of the passive pre-chamber showed that mixture distribution near the orifices during the compression stroke affects the averaged lambda of the gas inside the pre-chamber. By using the orifices with a tilted orientation, the fuel inside the pre-chamber could be stratified. When the mixture near electrodes is rich, the development of ignition kernel and the consequent flame propagation would benefit. In the case of active pre-chamber, although the lambda distribution patterns of mixture before the spark plug ignition are similar between different cycles, the magnitude of velocity would affect the early flame propagation inside the pre-chamber. [ABSTRACT FROM AUTHOR]

The ignition of spray flames is a process of stochastic nature, especially relevant to the high-altitude relight of aeroengines. The present work aims to quantify the role of spray inhomogeneities in a realistic droplet-laden ignition set-up through Direct Numerical Simulations (DNS). Computations of the ignition process of weakly turbulent ethanol spray flows are performed using complex chemistry, a realistic energy deposition model and a polydisperse description of the spray. A good qualitative agreement of the flame radius evolution is found between the DNS and experiments, and both long-time failure and ignition modes are recovered with comparable radii, hence reproducing the experimentally-observed range of behaviour of ignition kernels. In contrast to experiments where the presence of large droplets at the spark impact both the actual energy deposited in the flow and the local fuel-air equivalence ratio, the effect of both parameters on the ignition outcome are assessed independently in this work by carefully choosing ignition locations in the flow representative of time-wise fluctuations. The minimum ignition energy (MIE) representative of the global flow condition is then evaluated using results from the DNS simulations and flow and spark characteristics. In order to understand the origin of the ignition stochasticity observed experimentally, local values of the fuel-air equivalence ratio $ \Phi _t $ Φt and turbulence level $ u' $ u′ at the spark plug are measured in the simulations using an averaging in volumes of size $ \Delta _b $ Δb. It is found that $ \Phi _t $ Φt best correlates to the MIE at three different locations in the domain for a size around 4 mm, which corresponds approximately to the kernel size at 0.1 ms, that is, the typical time scale of plasma processes and right when the flame becomes toroidal. The results give support to the experimental conjecture that stochasticity is largely due to the spatial fluctuations of $ \Phi _t $ Φt induced by polydispersity and in a lesser extent to those of $ u' $ u′. [ABSTRACT FROM AUTHOR]

In order to produce reliable and reproducible ignition of lean fuel–air mixtures and highly stratified mixtures, it is necessary to ensure a high concentration of spark discharge energy and to provide a strong energy impulse for the triggering of chain processes of chemical decomposition of fuel molecules. For this reason, studies have been undertaken on the flow of electrical energy from the ignition system to the spark plug and on the formation of an electric discharge arc with a high concentration of thermal energy. The experimental results were obtained using an ignition coil energy test stand and a constant volume chamber with high-speed spark discharge recording capability. It was confirmed that increasing the charging time of the ignition coil from 0.5 ms to 5.0 ms increases the energy delivered to the coil from 9.5 mJ to 330 mJ. In the same range, the energy generated by the coil was recorded to range from 4.2 mJ to 70 mJ. The coil's efficiency was found to decrease with increasing charging time from 45% up to 20.5%. Further energy losses were presented when the spark discharge energy was analyzed. In the paper, the results of investigations concerning electric discharge arc development have been presented, illustrated by a few exemplary photos, and discussed. The mathematical interpretation of the electrical energy flux in the ignition system resulting from the energy of the discharge arc has been conducted and illustrated by some functional independences and relationships. [ABSTRACT FROM AUTHOR]

The main objective of this study is to develop spark ignition engine parameters that allow complete combustion while reducing dependence on fossil fuels. To achieve this goal, optimization of compression ratio, gasoline-ethanol mixture, ignition timing, and spark plug type was used. In addition, this study used water injection that continuously injects water before the intake manifold. In this study, the Taguchi method with the L9 orthogonal array was applied. According to the experimental verification results, the best combination to reduce exhaust emission levels is to utilize gasoline-ethanol (E70), a compression ratio (CR) of 15.6:1, an ignition degree of +4°, and a platinum spark plug. Meanwhile, the presence of water injection at 1.45 ml/s helps reduce vehicle exhaust pollutants. [ABSTRACT FROM AUTHOR]

• 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]

The pulse detonation combustor is a new type of power device based on periodic high temperature and high pressure gas generated by detonation combustion as thrust. Due to its extremely fast heat release rate, detonation combustion has the characteristics of high thermal efficiency, low fuel consumption and low pollutant emissions. In recent years, relevant institutions have conducted extensive research on pulse detonation combustors. However, most research results focus on single studies where the fuel and oxidant are in the gas phase. Based on the vision of engineering application of pulse detonation combustors, the research progress of two key pulse detonation technologies, fuel atomization blending technology and rapid short distance low resistance detonation technology, as well as the research status of two-phase pulse detonation combustion based on kerosene are introduced. Regarding fuel atomization and blending technology, this paper mainly introduces the fuel atomization mechanism of two phase detonation, fuel atomization technology and oil and gas blending technology. Regarding rapid short distance low resistance detonation technology, it mainly introduces obstacle assisted detonation technology, spark plug ignition technology, hot jet ignition technology, pre-detonation tube ignition technology, shock wave focusing detonation technology and plasma ignition technology. [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]

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]

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]