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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]

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]

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]

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Objective: In order to study the lean combustion process of a natural gas engine by separating the combustor, a spark ignition natural gas engine with separated combustors was retrofitted from a S195 single-cylinder diesel engine. Methods: The electronic control system controlled the gas supply and the spark plug ignition. A low pressure injection valve was set in the inlet pipe to form a lean mixture while a high pressure injection valve was placed in the subsidiary chamber to create a rich mixture, which was then ignited and injected into the main combustor, where the lean mixture was subsequently ignited again to achieve stratified combustion. Results: The test results showed that steady ignition is feasible in the system and verified the impact of the shape of the main combustor on HC, the impact of channel diameter on NOX production, and the impact of the ratios of high-pressure gas and low-pressure gas on HC and NOX. The combustion conditions of high-pressure gas and low-pressure gas in the engine combustor vary greatly. Our results signify that the shape of the main combustor has a great impact on the performance of the engine, that is, a shorter propagation distance can reduce the generation of HC. Conclusion: The best ignition advance angle under different conditions was determined using a spark ignition natural gas engine. The ratios of high-pressure gas and low-pressure gas greatly impact the performance and emission of the engine. The reduced diameter of the channels between the main and subsidiary combustors can enhance the stratification and facilitate the secondary ignition. [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]

Marine emission policies are becoming more demanding; thus, ship propulsion and power generation technologies need to be adapted to current scenarios. LNG is already considered to be a transition fuel, and new alternative marine fuels are emerging. The aim of this study was to develop an innovative methodology to optimize and adapt the combustion system of an LNG internal combustion marine engine to burn alternative marine fuels. The present study was based on LBG, but the methodology could be replicated with other fuels. A total of six tests were carried out, with three prechamber designs and three spark plug designs. Each test was carried out in a single-cylinder engine with two types of high-methane-number fuel. The influence on thermal efficiency parameters such as the prechamber volume, the orientation of the flame holes, and the existence of a central hole was studied. In the case of the spark plug, the influence of the amount of precious metal in the electrode, its shape and its insertion into the prechamber were analysed. Experiments showed that by modifying both the prechamber and the spark plug, maximum improvements in thermal efficiency of 1.9% can be achieved. Those improvements allowed the LBG engine to suffer only a 4.3% thermal efficiency reduction, as opposed to its LNG counterpart. By applying the proposed methodology, the thermal efficiency of commercially available internal combustion gas engines could be improved. [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 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]

Conventional gasoline engines suffer from low performance and NOx emissions. Controlled autoignition (CAI), sometimes referred to as homogeneous charge compression ignition (HCCI), is a promising concept to solve such problems. CAI has the potential to improve spark ignition (SI) engine fuel economy while at the same time solving the trade-off of NOx-soot emissions found in compression ignition (CI) engines. The CAI engine can reach a fuel economy comparable to that of a conventional diesel engine with ultra-low NOx and negligible soot emissions. However, controlling auto-ignition remains the biggest difficulty that hinders the implementation of CAI as a commercial engine. Research towards a cleaner and more efficient engine is driven by the progressively stringent emission regulation imposed worldwide. Therefore, the CAI was developed to meet the emissions target while maintaining engine performance. CAI works on the principle of lean mixture and auto-ignition. To obtain CAI combustion, the temperatures in the cylinder must be sufficient to initiate auto-ignition. Without the use of a spark plug or injector, the CAI suffers from a direct control mechanism to start the combustion. The most practical approach to controlling the initiation of auto-ignition in CAI is diluting the intake charge by either trapping the residual gas or recirculating the exhaust gas. Both approaches enable the engine to achieve CAI combustion without requiring significant modifications to control the onset of CAI combustion phase. [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]

Ultralean burn is considered an effective way to enhance the thermal efficiency of direct injection spark ignition engines. Herein, under ultralean burn condition, the split injection strategy is induced to investigate the in‐cylinder mixture distribution, combustion characteristics, and emissions by simulation in a high compression ratio engine model. First, the homogeneity index shows that compared with the single injection method, the split injection strategy shows better stratification of the mixture gas at the early stage of the compression stroke, which results in higher in‐cylinder pressure and heat release. Meanwhile, the results of heat balance show that split injection shows a slight effect on ignition delay, but significantly shortens combustion duration and advances CA50, and thus the exhaust loss is decreased. Second, with the decrease of a second injection fuel mass, the rich mixture is formed near the spark plug, thus reducing the ignition delay and combustion duration. Third, the split injection strategy presents faster flame kernel growth and propagation. A larger flame area is observed with the second injection mass decreasing. Finally, as the second fuel injection mass is reduced, NOx emissions increases continuously, while the soot emission decreases. [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]

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]

Hydrogen, as a suitable and clean energy carrier, has been long considered a primary fuel or in combination with other conventional fuels such as gasoline and diesel. Since the density of hydrogen is very low, in port fuel-injection configuration, the engine's volumetric efficiency reduces due to the replacement of hydrogen by intake air. Therefore, hydrogen direct in-cylinder injection (injection after the intake valve closes) can be a suitable solution for hydrogen utilization in spark ignition (SI) engines. In this study, the effects of hydrogen direct injection with different hydrogen energy shares (HES) on the performance and emissions characteristics of a gasoline port-injection SI engine are investigated based on reactive computational fluid dynamics. Three different injection timings of hydrogen together with five different HES are applied at low and full load on a hydrogen–gasoline dual-fuel SI engine. The results show that retarded hydrogen injection timing increases the concentration of hydrogen near the spark plug, resulting in areas with higher average temperatures, which led to NOX emission deterioration at −120 Crank angle degree After Top Dead Center (CAD aTDC) start of injection (SOI) compared to the other modes. At −120 CAD aTDC SOI for 50% HES, the amount of NOX was 26% higher than −140 CAD aTDC SOI. In the meanwhile, an advanced hydrogen injection timing formed a homogeneous mixture of hydrogen, which decreased the HC and soot concentration, so that −140 CAD aTDC SOI implied the lowest amount of HC and soot. Moreover, with the increase in the amount of HES, the concentrations of CO, CO2 and soot were reduced. Having the HES by 50% at −140 CAD aTDC SOI, the concentrations of particulate matter (PM), CO and CO2 were reduced by 96.3%, 90% and 46%, respectively. However, due to more complete combustion and an elevated combustion average temperature, the amount of NOX emission increased drastically. [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]

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]

Multiple ignition is beneficial to the improvement of engine thermal efficiency since it helps to shorten combustion duration and enhance lean-combustion stability. However, more researches are still needed to further understand knocking combustion under multiple ignition conditions, especially under lean-burn conditions. This study presents an investigation into the knocking characteristics under lean to stoichiometric conditions using multiple ignition on an optical rapid compression machine (RCM). Up to six ignition configurations were tested under three equivalence ratios (0.7/0.85/1). High-speed photography and high-frequency pressure acquisition were used to record the combustion processes. The results showed that the burning velocity increased nonlinearly with the increase of spark plug numbers while the knocking intensity (KI) first decreased and then increased, exhibiting a "U-shaped curve" trend. The burned mass fraction (BMF) at the instant of end-gas auto-ignition was also affected by ignition configuration. Generally, the smaller the BMF is at the instant of auto-ignition, the stronger the KI becomes. Furthermore, the key product during iso-octane oxidation, ·OOQOOH, was selected as an indicator to conduct chemical kinetics analysis on end-gas oxidation process. Results showed that the ignition configuration had strong impact on the heat release during flame propagation, which further influenced the reaction process of end-gas by influencing its low-temperature reactions. Under moderate spark plug number (around 3), the heat release during the flame propagation was most intensive, which further suppressed the low-temperature reactions of the end-gas and thus weakened auto-ignition intensity. [ABSTRACT FROM AUTHOR]

The increasingly stringent performance requirements for spark ignition engines have necessitated the use of precious metals as spark plug electrodes. However, the welding quality of these electrodes must be improved. An Ir–Rh alloy and a Ni-based material were welded by focusing a fiber laser with different offsets close to the weld centerline. Optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were conducted to analyze the microstructure and bonding mechanism of the welding seam as well as thermal fatigue performance. The welding seam mainly consists of an Ir–Ni solid solution, with a thin intermetallic compound (IMC) layer formed at the Ni-welded metal interface. Thermal fatigue experiment (TFE) results indicated that the thermal fatigue resistance is affected by thermal stress and high-temperature oxidation, and the dominant factor changes with the change in the laser beam offset. The joint exhibited the highest breakdown force of 163.3 N when the laser offset was 0.1 mm on the Ni side. Further, fracture only occurred on the Ir–Rh fusion line area, with different fracture mechanisms being observed. The results showed that the welding quality and thermal fatigue resistance of Ir–Rh/ Ni-based alloy joint were significantly improved by using an appropriate laser offset setting, which also reduced the abnormal expiration probability of the spark plug. [ABSTRACT FROM AUTHOR]

The increasing population density of automobiles leads to demands more fuel consumption that leads to reducing the availability and also raises the cost. Therefore, it is necessary to search for an alternate fuel, which can effectively replace the conventional fuel without affecting the engine design. The objective of this paper is to discuss the influence of waste plastic oil blends from 0% to 25% at four different ratios fuelled in a multi-cylinder Maruti 800 SI engine by using two types of sparkplugs; the conventional type spark plug that consists of a centre electrode with a copper core, and a plug with an iridium based electrode tip. From the outcomes of the experiments, the engine efficiency is improved, and emissions are controlled by using iridium spark plugs compared to the conventional type spark plugs. At a higher blend of 25%, PPO performance and emissions are analysed and presented in this research. The oxides of nitrogen emissions of engine fuelled with 25% of the plastic oil blend are 13% reduced, and 4.5% brake thermal efficiency are enhanced by using iridium spark plugs compared to 25% of plastic oil by using the conventional type of spark plugs at full load conditions. [ABSTRACT FROM AUTHOR]

In this study, the combustion chamber geometry for spray-guided, wall-guided, and air-guided combustion strategies were fabricated. The piston crown shape and the cylinder head in each combustion chamber geometry was machined by fixing the fuel injector and spark plug at proper positions to obtain swirl, turbulence, and squish effects for better mixing of fuel with air and superior combustion of the mixture. Conducted tests on all the three modified gasoline direct injection engines with optimized exhaust gas recirculation and electronic control towards fuel injection timing, the fuel injection pressure, and the ignition timing for better the performance and emissions control. It is clear from the results that NOx emissions from all three combustion modes were reduced by 4.9% up to 50% of loads and it increase for higher loads due to increase of in-cylinder pressure. The fuel consumption and emissions showed better at 150 bar fuel injection pressure for wall-guided combustion chamber geometry. Reduced HC emissions by 3.7% and 4.7%, reduced CO emissions by 2% and 3.3%, reduced soot emissions by 6.12% and 10.6%. Reduces specific fuel consumption by about 10.3% and 13.3% in wall-guided combustion strategy compare with spray-guided and airguided combustion modes respectively. [ABSTRACT FROM AUTHOR]

The main objective of this research study is to perform a thermographic analysis of a spark ignition engine by inducing controlled failures not detected by OBD II (Second Generation On-Board Diagnostic System) and by using a design of experiments (DoE). A full factorial design of two levels and two factors is applied. The experimental unit is a Hyundai Accent vehicle that is subjected to eight treatments in a dynamometric bench. The results show a temperature variation of 18.78 °C and a NOx of 291 ppm when altering the spark plug and 18.98 °C and a NOx of 20 ppm when modifying air filters. The results of combining both failures simultaneously are 55 °C and a NOx of 25 ppm. It is concluded that the quadratic mean (RMS) of a thermographic profile is the feature that best serves to assess vehicle failure factors and consequences since it provides an improved adjustment and a reduced standard deviation. [ABSTRACT FROM AUTHOR]

A port injection engine that supplies hydrogen to the intake manifold or port exhibits a low intake air amount and torque output. The torque output is limited by backfire. In the present study, the performance and efficiency of a port injection-type hydrogen engine using the fuel injector of a natural gas engine is investigated at various engines speeds under wide open throttle conditions and two operation strategies, i.e., limiting nitrogen oxide emission and maximizing the torque. The increase in electrode temperature is reduced by increasing the heat rating number of the spark plug or reducing the ignition energy applied to the spark plug. Even when the ignition energy is reduced, as the minimum ignition energy of hydrogen is very low, it does not eliminate backfire. However, when a cold-type spark plug is used, backfire is effectively suppressed, resulting in an increase in the maximum torque and a decrease in efficiency. • The excess air ratio must be at least 2.25 to meet the NO x level of 15 ppm. • The excess air ratio and tendency of backfire to occur increase with an increase in engine speed. • Reduction of the ignition energy does not eliminate the occurrence of backfire. • Backfire is effectively suppressed using a cold-type spark plug. [ABSTRACT FROM AUTHOR]

The study has focused on determining the laser plug effects on engine characteristics and the laser plug usage results have compared with spark plug usage. The laser ignition technique is a type of new ignition technique and an important solution that can make combustion systems more efficient. The testing of an engine with a laser plug is the novelty of the study and the tests were carried out with reference to equivalence ratio and plug power ranges. The behaviors of the engine at full load were examined so experimentally for both ignition techniques at hydrogen enriched CNG and iso-octane mixture usage. The tests were carried out for variations of 0.4–2.0 equivalence ratio and 20–120 W plug power. A mixture that 90% iso-octane and 10% HCNG in mass was used at two ignition modes in tests for 3300 rpm maximum engine torque speed. Also, the flame formation and propagation for both ignition techniques were detected via a high-speed camera. The tests have shown the laser ignition leads to more energy consumption in the rich mixture conditions and also, less energy is required in the lean conditions. The laser ignition discharge has extended the engine's lean combustion limits via a small energy input at the tests. The high-speed camera images have shown that the laser ignition reduces the Kernel flame formation and propagation time. The laser ignition technique was produced less NO x than the conventional spark ignition method. • Laser ignition effects on engine performance characteristics and emissions. • The tests were carried out for iso-octane - HCNG mixture at maximum torque speed. • Comparison of laser ignition effects with spark ignition for the flame formation. • The laser ignition has lead to less energy is required in the lean conditions. • The laser ignition technique has produced less NO x than the spark plug. [ABSTRACT FROM AUTHOR]

Lean burn combustion of natural gas in spark‐ignited engines is a promising approach to improving engine performance and efficiency by reducing pollutant emissions and better fuel consumption. However, inducing excessive lean mixture to the engine makes the combustion unstable, and misfire happens in a significant number of cycles. The pre‐chamber ignition technology is a useful solution that can make spark‐ignition engines more efficient. In this study, the lean mixture's combustion was empirically investigated with a new pre‐chamber spark plug in a one‐cylinder engine fueled with natural gas. Tests were performed at 11.5, 13.5, and 16 compression ratios and a wide range of air‐fuel ratios. With the pre‐chamber spark plug usage, the lean operating limit is enlarged by 10%–45% and gives 4% and 3% the average lower in‐cylinder pressure and exhaust gas temperature than the conventional spark ignition system. The brake‐specific fuel consumption was improved by 4%–11% using the pre‐chamber spark ignition. The HC, CO, and NOx formation is about 11%, 16.3%, and 10% lower than the conventional spark ignition usage. Outcomes confirmed that the new design pre‐chamber plug gives 1% improved COVIMEP than the standard spark plug. The use of pre‐chamber due to the lean‐burn combustion causes larger ignition delay and increases brake thermal efficiency by up to 9%. It can be concluded that the pre‐chamber increases the ignition ability, and the lean mixture limit is extended. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the ignition advance difference between the leading and trailing spark plugs found in the 13B-MSP (Multi Side Port) Wankel engine. The optimum ignition advance difference between the two-spark plugs had been determined by examining brake specific fuel consumption, emissions, p–V diagram, cumulative heat release rate and cyclical variations on the engine. Better results were obtained, if the advance difference was 15 or 20° in terms of total hydrocarbon and brake specific fuel consumption. It was observed that as the ignition advance difference decreased between the two-spark plugs, the combustion started earlier and completed in a short time, and when the ignition advance difference increased, the combustion started later and slower. Therefore, combustion improved with the ignition advance difference being 15°. The average of maximum pressures for 200 cycles was found as 20.48 bar, 26.11 bar and 17.36 bar in 5°, 15° and 30° ignition advance differences, respectively. 15° ignition advance difference was found to be faster to burn than other advance differences. It was observed that the optimum advance difference between the leading and trailing spark plugs should be 15°. Subsequently, single-spark plug (Trailing plug) and two-spark plug (Trailing + Leading plug) experiments were performed on different loads. As a result, two-spark plug compared to single-spark plug, fuel consumption and emissions decreased, and it was observed that combustion became better by increasing in-cylinder pressure and heat release rate. [ABSTRACT FROM AUTHOR]

The impact of injection timings on the in-cylinder flow field intensity, mixture formation process, combustion, and emission characteristics are analyzed. The range of injection timing is set between −320°CA and −260°CA. The research results indicate: Delaying the injection timing causes the spray plumes increasingly align with the tumble direction, consequently enhancing the in-cylinder tumble intensity and the turbulence near the spark timing. The mixture homogeneity is influenced by both the formation time and the in-cylinder flow field intensity. Moreover, combustion performance is linked to the homogeneity of the mixture and turbulence intensity near the spark timing. Despite the fact that postponed injection may augment both turbulence intensity and the equivalent ratio around the spark plug at the moment of spark, achieving higher explosion pressure, but the higher viscosity of n-butanol impedes droplet break-up, and its low volatility decelerates the evaporation rate, leading to poorer mixture homogeneity, reduced BMEP, and increased CO and soot emissions. However, at −300°CA start of injection, the extended mixing time optimizes the fuel-air mixture homogeneity, thus improving combustion quality and reducing CO, soot, and HC emissions, albeit leading to increased NOx emissions. • This research examines the process of mixture formation, combustion, and emission performance of n-butanol, which is characterized by higher dynamic viscosity，surface tension and lower volatility. • As the injection timing gets postponed, there is a simultaneous increase in both the in-cylinder tumble ratio and turbulence at the ignition moment. • Mixture homogeneity is dictated by the combination of mixture formation time and in-cylinder flow field intensity. • Earlier injection results in superior mixture homogeneity, thereby achieving improved combustion and emission performance. [ABSTRACT FROM AUTHOR]

In this study, the performance of different spark plugs was tested with varied spark gap sizes in a spark-ignited engine. Gasoline fuel was enriched with hydrogen and methanol to evaluate how much they affect the performance of the engine. The engine tests were performed with a four-stroke, single-cylinder, naturally aspirated, variable compression ratio (VCR) spark ignition engine. 1500 rpm engine speed and MBT for spark timing were applied throughout all experiments. Iridium, platinum and conventional (copper) spark plugs were tested using 3 different spark plug gaps (SPG) (0.6 mm, 0.8 mm, 1 mm). Depending on the experimental condition, hydrogen was added with 3 l/min of flow rate and methanol was used with 10% of volume fraction in the total liquid fuel. As for performance criteria, brake power (BP) and brake specific fuel consumption (BSFC) values were obtained from the test engine. According to the findings, platinum and iridium spark plugs had shown better performance than conventional spark plugs. The increment of SPG size improved the performance of the engine, too. On the other hand, despite methanol addition to gasoline fuel reduced performance, this loss could be compensated by hydrogen enrichment. Additionally, multiple linear regression (MLR) technique was applied through experimental results to obtain a linear relationship between explanatory variables (inputs) and response variables (outputs). An MLR model was set with four selected input variables (spark plug type, hydrogen flow rate, methanol ratio, and spark gap) to estimate BP and BSFC. Prediction equations showed that experimentally obtained results were in good agreement with MLR results. • SPG was tested with platinum, iridium and copper spark plugs. • Gasoline, methanol and hydrogen fuels were used. • Platinum and iridium spark plugs are effective on increasing performance. • Methanol deteriorates the engine performance. • Increment of SPG and H 2 increases performance characteristic. [ABSTRACT FROM AUTHOR]

Following rapid depletion of fossil fuels and growing efficiency concerns enforce researchers to enhance combustion quality and find alternative fuels for SI engines. For this purpose, various spark plugs are available in the market with different electrode materials. However, they have not been tested together with different engine parameters. In this work, a variable compression ratio (VCR) spark-ignited engine equipped with different spark plugs (conventional, iridium and platinum) tested to determine performance values of brake power and brake specific fuel consumption. Effects of hydrogen enrichment (0%, 2% and 4% by volume fraction) and VCR (8.5:1 and 10:1) were applied to the engine at engine speeds of 1200, 1500 and 1800 rpm during experiments. The results revealed that higher performance values attained with iridium and platinum spark plugs comparing with the conventional spark plug at all hydrogen fractions, engine speeds and compression ratios. Besides that platinum spark plug increased the performance of the test engine more than iridium one. [ABSTRACT FROM AUTHOR]

The ignition sparks provided by the conventional spark plug (CSP) do not always ensure a fast and complete combustion of the hydrocarbon–air mixture. For this reason, we offer a new type of spark plug with two simultaneous discharges generated by a pulsed high voltage–power supply. First, we present results concerning geometrical and electrical characteristics of plasmas produced in air and in engine combustion chamber. A more important volume of plasma is highlighted. The larger surface of interaction of plasma with the air-to-fuel mixture promotes the initiation of a greater number of chemical reactions thus increases the rate of propagation of the combustion. In addition, for long pulse durations the energy delivered by the double spark plug (DSP) to the discharge is 20% higher, as compared to a CSP. The current rise rate is more important for the DSP, which allows better ionization of the mixture. Afterwards, we present a study of two four-strokes engines ignited by this DSP, one powered with gasoline and the second one with propane. The pressure into the cylinder, measured as a function of the crankshaft angle, allowed to compute the IMEP, COVIMEP, and PPP, for both tested engines. In the case of the gasoline engine, when the ignition and flame development conditions are difficult—a high ignition angle was considered—the DSP can offer an almost 3.5 times better operation stability (considering the coefficient of variation of the indicated mean effective pressure as main indicator) and a faster development of the combustion flame (defined by the means of the pressure peak position). A study was also performed as a function of the equivalence ratio for the propane-powered engine, which confirmed the results regarding the DSP performances obtained with the first engine. In addition, this study highlighted that for very lean mixtures, the DSP can provide a better stability in operation (COVIMEP, COVPPP) is assured even for equivalence ratios in the range of 0.65, where the use of CSPs involves misfires and very high engine vibrations. [ABSTRACT FROM AUTHOR]

Backfire, an abnormal combustion phenomenon, in a hydrogen fuelled spark ignition (SI) engine was analyzed using computational fluid dynamics (CFD) and experimental tests. One of the main causes of backfire origin is the presence of any high temperature heat source including hot spot in the combustion chamber of the engine during intake process. A CFD based parametric study was carried out by varying the temperature of hot spot and its location in the combustion chamber of the engine in order to analyze their effects on backfire origin and its propagation in the intake manifold of the engine. The temperature of hot spot was varied from 800 K to till the temperature of backfire occurrence. The minimum temperature of hot spot at which backfire occurred was observed as 950 K and beyond. The probability of backfire occurrence increases with increase in hot spot temperature. The CFD simulations were also carried out by varying the location of hot spot (spark plug tip and exhaust valve) and the results indicate that the location of hot spot does not influence the characteristics of backfire but it affects the timing of its origin. The average backfire velocity is 230 m/s based on the average turbulent flame velocity during backfire propagation in the intake manifold and the value agreed reasonably well with the experimental observations of backfire propagation on the engine with the transparent intake manifold. Backfire propagation is under the category of deflagration based on its velocity (subsonic), and the maximum pressure gradient (<0.3 bar). The backfire phenomenon is characterized into three stages namely ignition delay for backfire, backfire propagation and its termination. The study results provide a better in-depth understanding of backfire origin and its propagation and would be helpful for developing a robust control strategy. Based on this study, it is recommended that the spark plug and exhaust valves of hydrogen fuelled SI engine should be customized in such a way that the temperature of spark plug tip and exhaust valves should not exceed 900 K during suction process in order to eliminate backfire occurrence. • Backfire in hydrogen fuelled SI engine was characterized using CFD and experiments. • Hot spot's minimum temperature for backfire occurrence was 950 K. • Hot spot's location does not influence backfire except the timing of its origin. • Backfire propagation was characterized as deflagration. • Spark plug tip/ex valves' temperature shall be below 900 K for controlling backfire. [ABSTRACT FROM AUTHOR]