Hydrogen Fueled Spark Ignition Engine Research Articles

Hydrogen-fueled PFI SI engine investigation for near-zero NOx emissions in de-throttled and supercharged ultra-lean burn conditions

This study investigates the efficiency and combustion characteristics of a hydrogen port fuel injection (PFI) spark ignition (SI) engine under various load levels, excess air ratios and intake pressures. Experiments were conducted on a single-cylinder research engine to evaluate the effects of throttle opening and supercharging on pumping work and combustion parameters. The key findings indicate that abnormal combustion events are more closely related to the relative air-fuel ratio (λ) than to load, further limiting load increases during de-throttled operation. Additionally, combustion variability compromised mixture enleanment in both naturally aspirated and supercharged conditions. The gross indicated efficiency was approximately 40.7% across the range of 2.2 < λ < 3.5 with minimal variation. Efficiency gains were linked to reduced heat transfer losses in lean conditions, as validated by computational heat transfer, thermodynamic and fluid dynamic models on Gamma Technologies GT-ISE software. Moreover, nitrogen oxides (NOx) emissions were nearly zero for all test conditions when λ was above 2.2. These findings provide crucial insights into optimizing hydrogen engine performance under various intake pressures, highlighting the potential for achieving high efficiency and low emissions.

An experimental investigation on the lean-burn characteristics of a novel hydrogen fueled spark ignition engine: Hydrogen injection via a micro-hole on the spark plug

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 φH2 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 NOX, 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.

Effects of Varying Excess Air Ratios on a Hydrogen-fueled Spark Ignition Engine with PFI and DI Systems under Low-load Conditions

Effects of Varying Excess Air Ratios on a Hydrogen-fueled Spark Ignition Engine with PFI and DI Systems under Low-load Conditions

Investigation on the performance of a by-product hydrogen-fueled spark-ignition engine with Miller cycle under various lean conditions

The direct combustion of by-product hydrogen is a promising way for reducing costs and greenhouse emissions. Coke oven gas (COG) which is mainly composed of H2, CH4 and CO is a major source of by-product hydrogen that is suitable to be adopted by internal combustion engines. This paper investigated the COG combustion in a spark-ignition engine with Miller cycle. To get an overview of by-product hydrogen combustion properties, two kinds of COG compositions with the maximum and minimum hydrogen fractions were tested. The excess air ratio (λ) was raised from stoichiometric to the lean limit to explore the capability of COG on improving the engine performance under a common-driving speed of 1500 rpm and part load conditions. The test results indicated that the engine fueled by COG with higher hydrogen fractions could gain concentrated heat release period, extended lean burn limit, reduced HC and CO2 emissions, and enhanced working capability only at ultra-lean conditions. The properly increased λ availed improving engine efficiency and lowering HC emissions. The peak indicated thermal efficiency of 38.6% was acquired at the λ of 1.2, while the lowest HC emissions of only 32 ppm was gained at the λ of 1.4. Under ultra lean conditions, NO emission dropped to near zero, and CO from the by-product hydrogen-fueled engine was negligible for all tested ranges. An interesting trend of peak pressure correlated crank angle versus λ was also found in this study.

Energy and exergy analyses of hydrogen-fueled spark ignition engine with various air excess ratios and ignition timings

Many studies have been conducted to determine the efficiency and emission of hydrogen internal combustion engines. However, only a few of these investigations have performed exergy analysis (especially when important parameters, such as excess air ratio, vary) based on the second law of thermodynamics. Accordingly, in this study, experiments were conducted on a commercial automotive spark ignition engine. The engine is modified to run on hydrogen as fuel at 1500 rpm with various spark timings and excess air ratios under a wide-open throttle. In addition, zero-dimensional two-zone modeling was conducted by matching and examining the experimental results considering both energy (first law of thermodynamics) and exergy (second law of thermodynamics) analyses.The results indicate that with the same excess air ratio, the trend exergy analysis results, such as increasing exhaust exergy loss and decreasing heat transfer exergy loss by retarding ignition timing, are similar to the energy analysis results. Additionally, irreversibility increased as the spark timing retarded owing to the reduction in combustion temperature caused by prolonged combustion duration. In considering various excess air ratios, the gap between the energy and exergy analysis results was evaluated: the heat transfer exergy loss increased from 27% to 31%, the exhaust exergy loss decreased from 20% to 15%, and irreversibility was maintained at approximately 10%. Irreversibility was maintained because of the offset between the irreversibility increment (due to the decrease in combustion temperature) and decrement (due to the decrease in fuel amount). Moreover, the relationship between the thermo-mechanical exergy rise rate and behavior of each exergy component was examined.

Effect of Excessive Air Ratio on Hydrogen-fueled Spark Ignition Engine with High Compression Ratio Using Direct Injection System toward Higher Brake Power and Thermal Efficiency

Effect of Excessive Air Ratio on Hydrogen-fueled Spark Ignition Engine with High Compression Ratio Using Direct Injection System toward Higher Brake Power and Thermal Efficiency

Effect of Two Mechanisms Contributing to the Cyclic Variability of a Methane–Hydrogen-Fueled Spark-Ignition Engine by Using a Fast CFD Methodology

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.

Optimization of fuel injection timing and ignition timing of hydrogen fueled SI engine based on DOE-MPGA

For the port injection hydrogen-fueled spark ignition (SI) engine modified from the Jialing JH600 gasoline engine, the hydrogen injection timing and ignition timing of the hydrogen SI engine are comprehensively optimized on the AVL-FIRE software based on the combination of design of experiment (DOE) and multiple population genetic algorithm (MPGA). Firstly, the effects of hydrogen injection timing and ignition timing on the performance of the hydrogen engine are investigated through the full factors design of experiment scheme, and then the optimum intervals of them are determined respectively. Secondly, the uniform design of experiments scheme is arranged, and the regression functions of indicated power, indicated thermal efficiency and emissions of the hydrogen engine under different working conditions are fitted. Then, the comprehensive optimization model is constructed. Finally, the optimum hydrogen injection timing and ignition timing of the hydrogen engine under different working conditions are solved based on MPGA. The results show that, compared with the standard genetic algorithm (SGA), the MPGA has faster convergence speed and higher convergence accuracy. In addition, as the load increases from low to high, the optimum hydrogen injection timing is advanced and the rate of variation increases from 0.6% to 1.1%, the optimum ignition timing is delayed and the rate of variation decreases from 29.1% to 17.8%.

Detonation development in hydrogen/air mixtures inside a closed chamber: role of a cold wall

Detonation development from a hot spot has been extensively studied, where ignition occurs earlier than that in the surrounding mixtures. It has also been reported that a cool spot can induce detonation for large hydrocarbon fuels with Negative Temperature Coefficient (NTC) behavior, since ignition could happen earlier at lower temperatures. In this work we find that even for hydrogen/air mixtures without NTC behaviors, a cold wall can still initiate and promote detonation. End-wall reflection of the pressure wave and wall heat loss introduce an exothermic center outside the boundary layer, and then autoignitive reaction fronts on both sides may evolve into detonation waves. The right branch can be further strengthened by appropriate temperature gradient near the cold wall, and exhibits different dynamics at various initial conditions. The small excitation time and the large diffusivity of hydrogen provide the possibility for detonation development within the limited space between the autoignition kernel and the cold wall. Moreover, detonation may also develop near the flame front, which may or may not co-exist with detonation waves from the cold wall. Correspondingly, wall heat flux evolution exhibits different responses to detailed dynamic structures. Finally, we propose a regime diagram describing different combustion modes including normal flame, autoignition, and detonation from the wall and/or the reaction front. The boundary of normal flame regime qualitatively agrees with the prediction by the Livengood-Wu Integral method, while the detonation development from both the end wall and the reaction front observes Zel'dovich mechanism. Compared to hydrocarbons, hydrogen is resistant to knock onset but it is more prone to superknock development. The latter mode becomes more destructive in the presence of wall heat loss. This study isolates and identifies the role of wall heat loss on a potential mechanism for superknock development in hydrogen-fueled spark-ignition engines.

A novel approach for experimental study and numerical modeling of combustion characteristics of a hydrogen fuelled spark ignition engine

This work is aimed for experimental study on effects of spark timings, compression ratios (4.5:1 to 7.2:1) and exhaust gas recirculation (EGR) on combustion characteristics of hydrogen fuelled spark ignition (SI) engine operating at 3000 rpm. The results indicate spark timing should be reduced for hydrogen fuelled engine as compared to the gasoline fuelled engine. Both ignition lag and DOC decreased with an increase in equivalence ratio and compression ratio, while the opposite trend was observed with an increase in EGR. The EGR was limited up to 23.5 % by volume, as higher EGR lead to cyclic variation. The standard Wiebe function constants were modified for the calculation of mass fraction burnt in a hydrogen fuelled SI engine. In addition to this, the empirical correlations were developed for ignition lag (IL) and duration of combustion (DOC) as a function of compression ratio, equivalence ratio, and EGR. The notable findings that emerged from this study are that hydrogen-fuelled SI engines should be operated at varying spark timing with respect to varying equivalence ratios (0.5 to 0.8) and EGR up to 23.5% by volume.

Effect of Excessive Air Ratio on Hydrogen-Fueled Spark Ignition Engine with High Compression Ratio Using Direct Injection System Toward Higher Brake Power and Thermal Efficiency

Effect of Excessive Air Ratio on Hydrogen-Fueled Spark Ignition Engine with High Compression Ratio Using Direct Injection System Toward Higher Brake Power and Thermal Efficiency

Investigation on the operable range and idle condition of hydrogen-fueled spark ignition engine for unmanned aerial vehicle (UAV)

In this study, a hydrogen-fueled spark ignition engine was investigated for UAV operation, with a focus on its combustion region and idle condition. A 2.4l, four-cylinder spark ignition engine was used for experiments, with modification for hydrogen usage instead of gasoline. In experiments, the feasible combustion region and limitations of the combustion phenomena for the hydrogen-fueled spark ignition engine at specific load and speed conditions of 50 Nm and 2000 RPM were examined. It was found that owing to the wide flammability range of hydrogen, the air–fuel ratio could be varied from 1.0 to 2.4. However, misfire and backfire occurred because of the mixing issue and highly ignitable characteristics of the hydrogen–air mixture, respectively, under relatively rich conditions (excess air ratio between 1.0 and 1.5). Unstable combustion occurred under a relatively lean condition (excess air ratio>2.0). Considering important parameters such as the nitrogen oxide emissions, unburned hydrogen, and brake thermal efficiency, an excess air ratio between 1.8 and 2.0 with maximum brake torque timing (MBT) operation was appropriate for this condition. Extremely lean conditions with zero load can be achieved with stable combustion with the excess air ratio up to 3.0, which can almost eliminate nitrogen oxide emissions.

Evaluating the effects of boosting intake-air pressure on the performance and environmental-economic indicators in a hydrogen-fueled SI engine

In this paper, the effects of external supercharger application on in-cylinder combustion, performance parameters, fuel efficiency and environmental-economic indicators are discussed together regarding a hydrogen-fueled spark ignition engine operating under a lean mixture. The engine was operated at an engine speed of 1600 rpm, under four different boosting pressures (between 10 kPa and 40 kPa), by optimized ignition timing and being compared to a normally aspirated condition. Hydrogen was injected at five bars into the inlet-air. The results show that the indicated mean effective pressure and thermal efficiency increased by 38.9% and 14.2%, respectively, with a 40 kPa boosting pressure under an optimized ignition timing condition according to the normally aspirated engine, and that the cyclic variation decreased by 15.5%. In addition, under 40 kPa boosting pressure, NOx emissions increased by 45.2% and its environmental-social cost increased by 21.8%, while specific fuel consumption and fuel cost were reduced by approximately 18.5%.

Effect of supercharger system on power enhancement of hydrogen-fueled spark-ignition engine under low-load condition

Hydrogen energy has received much attention in recent years due to its reliability and non-carbon products. However, it has been found that the backfire phenomenon plays a major part in limiting power and torque in the hydrogen internal combustion engine (H2ICE). Much research in recent years has considered turbocharger as a useful method to improve the power of H2ICE. Although the result of boosting a system with turbocharger became enhanced when compared to the natural aspiration system. Unfortunately, there were unsolved problems in exhaust backpressure and pumping losses that hindering the practical utilisation of H2ICE. This paper investigated the experiment of 2.4 L supercharged port fuel injection engine at 2000 rpm. Air excess ratio (lambda) was varied from stoichiometric to 2.8 by adjusting the boosting amount in supercharger, and throttling of the air. The hydrogen injection amount were maintained the same with turbocharger condition; spark advance timing was set at maximum brake torque. It was observed that by boosting engine with supercharger, the lower pumping loss and higher indicated mean pressure had been obtained when compared to turbocharger boosted engine under low-load condition. However, some additional power required for supercharging that lowers output of the engine.

Development of online control system for elimination of backfire in a hydrogen fuelled spark ignition engine

Backfire is one of the major technical issues in a port injection type hydrogen fuelled spark ignition engine. It is an abnormal combustion phenomenon (pre-ignition) that takes place in combustion chamber and intake manifold during suction stroke. The flame propagates toward the upstream of the intake manifold from combustion chamber during backfire and thus can damage the intake and fuel supply systems of the engine, and stall the engine operation. The main cause of backfire could be the presence of any hot spot, lubricating oil particle's traces (HC and CO due to evaporation of the oil) and hot residual exhaust gas present in the combustion chamber during suction stroke which could act as an ignition source for fresh incoming charge. Monitoring the temperatures of the lubricating oil and exhaust gas during engine operation can reduce the probability of backfire. This was achieved by developing an electronic device which delays the injection timing of hydrogen fuel with the inputs of engine oil temperature (Tlube oil) and exhaust gas temperature (Texh). It was observed from the experimental results that the threshold values of Tlube oil and Texh were 85 °C and 540 °C respectively beyond which backfire occurred at equivalence ratio (φ) of 0.82. The developed device works based on the algorithm that retards the hydrogen injection to 40 0aTDC whenever the temperatures (Tlube oil and Texh) reached to the above mentioned values and thus the backfire was controlled. Delaying injection of hydrogen increased the time period at which only air is inducted during the early part of the suction stroke, this allows cooling of the available hot spots in the combustion chamber, hence the probability of backfire would be reduced.

Fundamental characterization of backfire in a hydrogen fuelled spark ignition engine using CFD and experiments

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.

Effect of different excess air ratio values and spark advance timing on combustion and emission characteristics of hydrogen-fueled spark ignition engine

This study investigated the effect of varying the spark advance timing and excess air ratio (air excessive ratio; λ) on the combustion and emission of nitrogen oxide (NOx) in a hydrogen-fueled spark ignition engine under part load conditions. The engine test speed was fixed at 2,000 rpm and the torque condition was 60 Nm. Excess air ratio was varied from the stoichiometric (λ = 1) to the lean mixture condition (λ = 2.2) by throttling. The spark advance timing was controlled to determine the maximum brake torque timing (MBT) for each excess air ratio value. Subsequent to the determination of the spark advance timing for MBT, the spark timing was varied from MBT timing to top dead center. Based on the results, it is concluded that the leanest mixture condition (λ = 2.2) with MBT spark timing exhibited the highest brake thermal efficiency of 34.17% and the NOx emissions were as low as 14 ppm.

Experimental Investigation for NOx Emission Reduction in Hydrogen Fueled Spark Ignition Engine Using Spark Timing Retardation, Exhaust Gas Recirculation and Water Injection Techniques

The experimental tests were carried out on a single cylinder hydrogen fueled spark ignition (SI) generator set with different spark timings (4-20°CA bTDC), exhaust gas recirculation (EGR) up to 28% by volume and water injection up to 1.95 kg/h (maximum water to fuel mass ratio of 8:1). The engine speed was kept constant of 3000 r/min. The NOx emission and thermal efficiency of engine with gasoline and hydrogen fuel operation at 1.4 kW power output are 5 g/kWh and 12.1 g/kWh, and 15% and 20.9% respectively. In order to reduce the NOx emission at source level, retarding spark timing, exhaust gas recirculation (EGR), and water injection techniques were studied. NOx emission decreased with spark timing retardation, EGR, and water injection. NOx emission with hydrogen at 1.4 kW power output decreased from 12.1 g/kWh with maximum brake torque (MBT) spark timing (10°CA bTDC) to 8.1 g/kWh with retarded spark timing (4°CA bTDC) due to decrease in the in-cylinder peak pressure and temperature. The NOx emission decreased to 6.1 g/kWh with 20% EGR due to thermal and chemical dilution effect. However, thermal efficiency decreased about 33% and 17% with spark timing retardation and 20% EGR respectively as compared to that of MBT spark timing. But, in the case of water injection, the NOx emission decreased significantly without affecting the thermal efficiency of the engine and it is 5.6 g/kWh with water-hydrogen ratio of 4:1 (water flow rate of 0.92 kg/h). Water injection is the best suitable method to reduce the NOx emission in a hydrogen fueled engine compared with the spark timing retardation and EGR technique.

Realizing low emissions on a hydrogen-fueled spark ignition engine at the cold start period under rich combustion through ignition timing control

This paper analyzed low emissions on a hydrogen-fueled spark ignition (SI) engine at the cold start period under rich combustion through ignition timing (IT) control. Cold start characteristics of hydrogen-fueled engine were investigated experimentally. The study was performed under different IT. The results demonstrated that when excess air ratio (λ) was 0.7 and IT varied from 25 °CA BTDC to 10 °CA ATDC, the peak cylinder pressure of the first cycle and the successful start time (SST) of hydrogen engine first increased and then decreased with the retard of IT. At 15 °CA BTDC, the hydrogen engine gained the shortest SST and the highest cylinder pressure in the first cycle. Flame development period (CA0-10) first shortened and then lengthened, and flame propagation period (CA10-90) prolonged when IT gradually retarded. The average NOx emissions efficiently reduced by 90.2%, HC and CO emissions caused by the evaporated lubricant oil reduced individually by 33.8% and 19.7% in the first 6 s during the cold start process with the retard of IT. Especially when IT delayed from 25 °CA BTDC to 15 °CA BTDC, the effect of IT on HC emissions was significant.

Control of backfire and NOx emission reduction in a hydrogen fueled multi-cylinder spark ignition engine using cooled EGR and water injection strategies

The experimental study was carried out on a constant speed multi-cylinder spark ignition engine fueled with hydrogen. Exhaust gas recirculation (EGR) and water injection techniques were adopted to control combustion anomalies (backfire and knocking) and reduce NOx emission at source level. The experimental tests were conducted on the engine with varied EGR rate (0%–28% by volume) and water to hydrogen ratio (WHR) (0–9.25) at 15 kW load. It was observed from the experiments that both the strategies can control backfire effectively, but water injection can effectively control backfire compared to EGR. The water injection and EGR reduce the probability of backfire occurrence and its propagation due to the increase in the requirement of minimum ignition energy (MIE) of the charge, caused mainly due to charge dilution effect, and reduction in flame speed respectively. The NOx emission was continuously reduced with increase in EGR rate and WHR, but at higher rates (of EGR and WHR), there was an issue of stability of engine operation. It was found from the experimental results that at 25% EGR, there was 57% reduction in NOx emission without drop in brake thermal efficiency whereas, with WHR of 7.5, the NOx emission was reduced by 97% without affecting the efficiency. The salient point emerging from the study is that water injection technique can control backfire with ultra-low (near zero) NOx emission without compromising the performance of the hydrogen fueled spark ignition engine.