Direct injection of hydrogen main fuel and diesel pilot fuel in a retrofitted single-cylinder compression ignition engine

Up to 90% hydrogen energy fraction was achieved in a hydrogen diesel dual-fuel direct injection (H2DDI) light-duty single-cylinder compression ignition engine. An automotive-size inline single-cylinder diesel engine was modified to install an additional hydrogen direct injector. The engine was operated at a constant speed of 2000 revolutions per minute and fixed combustion phasing of ?10 crank angle degrees before top dead centre (°CA bTDC) while evaluating the power output, efficiency, combustion and engine-out emissions. A parametric study was conducted at an intermediate load with 20–90% hydrogen energy fraction and 180-0 °CA bTDC injection timing. High indicated mean effective pressure (IMEP) of up to 943 kPa and 57.2% indicated efficiency was achieved at 90% hydrogen energy fraction, at the expense of NO_x emissions. The hydrogen injection timing directly controls the mixture condition and combustion mode. Early hydrogen injection timings exhibited premixed combustion behaviour while late injection timings produced mixing-controlled combustion, with an intermediate point reached at 40 °CA bTDC hydrogen injection timing. At 90% hydrogen energy fraction, the earlier injection timing leads to higher IMEP/efficiency but the NO_x increase is inevitable due to enhanced premixed combustion. To keep the NO_x increase minimal and achieve the same combustion phasing of a diesel baseline, the 40 °CA bTDC hydrogen injection timing shows the best performance at which 85.9% CO₂ reduction and 13.3% IMEP/efficiency increase are achieved.     

Effect of manifold injection of hydrogen gas in producer gas and neem biodiesel fueled CRDI dual fuel engine

The high flammability of hydrogen gas gives it a steady flow without throttling in engines while operating. Such engines also include different induction/injection methods. Hydrogen fuels are encouraging fuel for applications of diesel engines in dual fuel mode operation. Engines operating with dual fuel can replace pilot injection of liquid fuel with gaseous fuels, significantly being eco-friendly. Lower particulate matter (PM) and nitrogen oxides (NO_x) emissions are the significant advantages of operating with dual fuel.Consequently, fuels used in the present work are renewable and can generate power for different applications. Hydrogen being gaseous fuel acts as an alternative and shows fascinating use along with diesel to operate the engines with lower emissions. Such engines can also be operated either by injection or induction on compression of gaseous fuels for combustion by initiating with the pilot amount of biodiesel. Present work highlights the experimental investigation conducted on dual fuel mode operation of diesel engine using Neem Oil Methyl Ester (NeOME) and producer gas with enriched hydrogen gas combination. Experiments were performed at four different manifold hydrogen gas injection timings of TDC, 5°aTDC, 10°aTDC and 15°aTDC and three injection durations of 30°CA, 60°CA, and 90°CA. Compared to baseline operation, improvement in engine performance was evaluated in combustion and its emission characteristics. Current experimental investigations revealed that the 10°aTDC hydrogen manifold injection with 60°CA injection duration showed better performance. The BTE of diesel + PG and NeOME + PG operation was found to be 28% and 23%, respectively, and the emissions level were reduced to 25.4%, 14.6%, 54.6%, and 26.8% for CO, HC, smoke, and NO_x, respectively.     

Combustion and emission characteristics of an Acetone-Butanol-Ethanol (ABE) spark ignition engine with hydrogen direct injection

Butanol could reduce emissions and alleviate the energy crisis as a bio-fuel used on engines, but the production cost problem limits the application of butanol. During the butanol production, ABE (Acetone-Butanol-Ethanol) is a critical intermediate product. Many studies researched the direct application of ABE on engines instead of butanol to solve the production cost problem of butanol. ABE has the defects of large ignition energy and vaporization heat. Hydrogen is a gaseous fuel with small ignition energy and high flame temperature. In this research, ABE port injection combines with hydrogen direct injection, forming a stratified state of the hydrogen-rich mixture around the spark plug. The engine speed is 1500 rpm, and λ is 1. Five αH₂ (hydrogen blending fractions: 0, 5%, 10%, 15%, 20%) and five spark timings (5°, 10°, 15°, 20°, 25° CA BTDC) are studied to observe the effects of them on combustion and emissions of the test engine. The results show that hydrogen addition increases the maximum cylinder pressure and maximum heat release rate, increases the maximum cylinder temperature and IMEP, but the exhaust temperature decreases. The flame development period and flame propagation period shorten after adding hydrogen. Hydrogen addition improves HC and CO emissions but increases NO_x emissions. Particle emissions decrease distinctly after hydrogen addition. Hydrogen changes the combustion properties of ABE and improves the test engine's power and emissions. The combustion in the cylinder becomes better with the increase of αH₂, but a further increase in αH₂ beyond 5% brings minor improvements on combustion.     

On-board generation of hydrogen to improve in-cylinder combustion and after-treatment efficiency and emissions performance of a hybrid hydrogen–gasoline engine

Hydrogen on-board fuel reforming has been identified as a waste energy recovery technology with potential to improve Internal combustion engines (ICE) efficiency. Additionally, can help to reduce CO₂, NO_x and particulate matter (PM) emissions. As this thermochemical energy is recovered from the hot exhaust stream and used in an efficient way by endothermic catalytic reforming of petrol mixed with a fraction of the engine exhaust gas. The hydrogen-rich reformate has higher enthalpy than the petrol fed to the reformer and is recirculated to the intake manifold, which will be called reformed exhaust gas recirculation (rEGR).The rEGR system has been simulated by supplying hydrogen (H₂) and carbon monoxide (CO) into a conventional Exhaust Gas Recirculation (EGR) system. The hydrogen and CO concentrations in the rEGR stream were selected to be achievable in practice at typical gasoline exhaust temperatures (temperatures between 300 and 600 °C). A special attention has been paid on comparing rEGR to the baseline ICE, and to conventional EGR. The results demonstrate the potential of rEGR to simultaneously increase thermal efficiency, reduce gaseous emissions and decrease PM formation.Complete fuel reformation can increase the calorific value of the fuel by 28%. This energy can be provided by the waste heat in the exhaust and so it is ideal for combination with a gasoline engine with its high engine-out exhaust temperatures.The aim of this work is to demonstrate that exhaust gas fuel reforming on an engine is possible and is commercially viable. Also, this paper demonstrates how the combustion of reformate in a direct injection gasoline engine via reformed Exhaust Gas Recirculation (rEGR) can be beneficial to engine performance and emissions.     

CFD analysis of hydrogen injection pressure and valve profile law effects on backfire and pre-ignition phenomena in hydrogen-diesel dual fuel engine

This paper focuses on optimizing the hydrogen TMI (timed manifold injection) system through valve lift law and hydrogen injection parameters (pressure, injection inclination and timing) in order to prevent backfire phenomena and improve the volumetric efficiency and mixture formation quality of a dual fuel diesel engine operating at high load and high hydrogen energy share. This was achieved through a numerical simulation using CFD code ANSYS Fluent, developed for a single cylinder hydrogen-diesel dual fuel engine, at constant engine speed of 1500 rpm, 90% of load and 42.5% hydrogen energy share. The developed tool was validated using experimental data. As a results, the operating conditions of maximum valve lift = 10.60 mm and inlet valve closing = 30 °CA ABDC (MVL10 IVC30) prevent the engine from backfire and pre-ignition, and ensure a high volumetric efficiency. Moreover, a hydrogen start of injection of 60 °CA ATDC (HSOI60) is appropriate to provide a pre-cooling effect and thus, reduce the pre-ignition sources and helps to quench any hot residual combustion products. While, the hydrogen injection pressure of 2.7 bar and an inclination of 60°, stimulate a better quality of hydrogen-air mixture. Afterwards, a comparison between combustion characteristics of the optimized hydrogen-diesel dual fuel mode and the baseline (diesel mode) was conducted. The result was, under dual fuel mode there is an increase in combustion characteristics and NOx emissions as well as a decrease in CO2 emissions. For further improvement of dual fuel mode, retarding diesel start of injection (DSOI) strategy was used.     

Effect of natural gas enrichment with hydrogen on combustion process and emission characteristic of a dual fuel diesel engine

The paper presents results of experimental research on a dual-fuel engine powered by diesel fuel and natural gas enriched with hydrogen. The authors attempted to replace CNG with hydrogen fuel as much as possible with a constant dose of diesel fuel of 10% of energy fraction. The tests were carried out for constant engine load of IMEP = 0.7 MPa and a rotational speed of n = 1500 rpm. The effect of hydrogen on combustion, heat release, combustion stability and exhaust emissions was analyzed. In the test engine, the limit of hydrogen energy fraction was 19%. The increase in the fraction caused an increase in the cycle-by-cycle variation and the occurrence of engine knocking. It was shown that the enrichment of CNG with hydrogen allows for the improvement in the combustion process compared to the co-combustion of diesel fuel with non-enriched CNG, where the reduction in the duration of combustion by 30% and shortening the time of achieving 50% of MFB by 50% were obtained. The evaluation of the spread of the end of combustion is also presented. For H₂ energetic share over 20%, the spread of end of combustion was 48° of crank angle. Measurement of exhaust emissions during the tests revealed an increase in THC and NO_x emissions.     

Investigation of the effects of hydrogen on cylinder pressure in a split-injection diesel engine at heavy EGR

The distinctive properties of hydrogen have initiated considerable applied research related to the internal combustion engine. Recently, it has been reported that NO_x emissions were reduced by using hydrogen in a diesel engine at low temperature and heavy EGR conditions. As the continuing study, cylinder pressure was also investigated to determine the combustion characteristics and their relationship to NO_x emissions. The test engine was operated at constant speed and fixed diesel fuel injection rate (1500 rpm, 2.5 kg/h). Diesel fuel was injected in a split pattern into a 2-L diesel engine. The cylinder pressure was measured for different hydrogen flow rates and EGR ratios. The intake manifold temperature was controlled to be the same to avoid the gas intake temperature variations under the widely differing levels (2%-31%) of EGR. The measured cylinder pressure was analyzed for characteristic combustion values, such as mass burn fraction and combustion duration.The rising crank angle of the heat release rate was unaffected by the presence of hydrogen. However, supplying hydrogen extended the main combustion duration. This longer main combustion duration was particularly noticeable at the heavy EGR condition. It correlated well with the reduced NO_x emissions.     

Optimization of hydrogen-enriched diesel/n-Amyl alcohol-fueled engine to meet emission standards through varying nozzle opening pressure and static injection timing

Important injection parameters such as fuel injection timing (FIT) and fuel injection pressure (FIP) on different piston bowl geometries substantially impact the performance, emissions, and combustion characteristics of a common rail direct injection engine. The aim of this study deals with the effects of piston bowl geometry (hemispherical bowl [HSB], troded bowl [TRB], and re-entrant bowl [REB]), FIP (200, 220, and 240 bar), and variable FIT (20, 24, and 28°bTDC) with hydrogen-diesel/1-pentanol (B20) (80% diesel and 20% pentanol) with a constant flow rate of hydrogen at 12 Lpm. Furthermore, to decrease emission standards and energy consumption, biodiesel and hydrogen are the ideal substitutes for conventional fuels. REB outperforms HSB and TRB in terms of brake thermal efficiency (5.67%) and hydrocarbon (8% reduction), increasing the FIP at full load (240 bar). However, with the increase in the FIP in the REB, a slight reduction in nitrogen oxide (NO_x) emissions (2%) is observed. With an increase in FIP in the case of REB, net heat release rate, peak pressure (in-cylinder), and rate of pressure rise all rise significantly by 3.4%, 4.2%, and 2.3%. NO_x emissions are marginally enhanced with higher FIP and advanced FIT. It is found that changing the piston shape and FIP simultaneously is a potential alternative for improving engine performance and lowering emissions.     

Exploration of engine characteristics in a CRDI diesel engine enriched with hydrogen in dual fuel mode using toroidal combustion chamber

The impact of dual fuel (diesel/hydrogen) on different performance aspects of CRDI diesel engines is investigated in this study. Amongst the fuel alternatives for IC (internal combustion) engines, the research described in this study recommended hydrogen as the least polluting and renewable in the long term. A CNG-LPG injector feeds hydrogen into the intake manifold, while diesel injectors pump pilot diesel to a DI engine adapted to hydrogen and diesel (dual-fuel mode). By maintaining 5.2 KW of consistent IP (Indicated Power) and engine speed at 1500 ± 10 rotations per minute (RPM), the hydrogen energy was varied in the dual fuel at 0% (100% diesel), 6%, 12%, 18% and 24%. With the increase in H₂ energy proportion, a decrease (5.2% decrease at 24% HES) in the BSEC (brake specific energy consumption) and the engine's BTE (brake thermal efficiency) is improved (7.85% increase at 24% HES). When emissions are considered, indicated NO_x increased (3.42%) while indicated CO₂ (3.61%), CO (2.84%), and smoke (4.85%) decreased with an increase in the proportion of hydrogen. Along with this, it was noted that the peak HRR (heat release rate) of 69.8 J/deg and in-cylinder pressure of 80.8 bar which increased significantly with the increase in hydrogen rate.     

Experimental investigation of the effect of hydrogen ratio on engine performance and emissions in a compression ignition single cylinder engine with electronically controlled hydrogen-diesel dual fuel system

In recent years, there has been a rapid transition from internal combustion engines to hybrid and electric vehicles. It is an inevitable fact that the dominance of internal combustion engines in the market will continue for many years due to the charging and battery problems in these vehicles. Therefore, it is an important issue to improve the performance and emissions of internal combustion engines by making them work with alternative energy sources. In this study, hydrogen-diesel dual fuel mode was used in a dual-fuel compression ignition single cylinder engine with common rail fuel injection system and electronically controlled gas fuel system. The study was carried out at constant speed (1850 rpm), different load (3-4.5-6-7.5-9 Nm) and different hydrogen injector opening amounts (1.6-1.8-2.0 ms). The effects of hydrogen energy ratios obtained with different hydrogen injector opening amount on engine performance and emissions were examined. According to the results, it was determined that the in-cylinder pressure values increased at medium and high loads, and the specific energy consumption decreased. When the emission values were examined, it was determined that there was an increase in NO emissions and a significant decrease in other emissions. However, increasing the hydrogen energy ratio above 14% adversely affected engine performance and emissions.     

Emission and performance estimation in hydrogen injection strategies on diesel engines

Recently, the increasing demand for energy requires the use of alternative fuels, especially in fossil fueled power systems. As a promising alternative fuel for next-generation diesel engines that utilize fossil fuel, hydrogen fuel is one step ahead due to its positive properties. In this study, the effects of hydrogen on the performance of a diesel engine have been numerically investigated with respect to different injection ratios and timings. The numerical results of the study for 25% load conditions on a single-cylinder, four-stroke diesel engine have been validated against experimental data taken from literature and good agreement has been observed for pressure results. Emission parameters such as NO_x, CO and performance parameters such as cylinder temperature, pressure, power, thermal efficiency and IMEP are presented comparatively.The results of numerical analyses show that the maximum pressure, temperature and heat release rate are observed with injection ratio of H15 and early injection timing (20° CA BTDC). Besides that, engine power, thermal efficiency and IMEP are greatly improved with increasing injection ratio and early injection timing. Although combustion chamber performance parameters improve with rising the hydrogen injection ratio, higher NO_x emissions have also been detected as a negative side effect. Furthermore, while early injection timing increases diesel engine performance, it also causes an increase in NO_x emissions. Therefore, precise determination of injection timing together with the optimum amount of hydrogen has revealed that it brings crucial improvement in engine performance and emissions.     

Hydrogen impacts on performance and CO2 emissions from a diesel power generator

This work investigates the performance and carbon dioxide (CO₂) emissions from a stationary diesel engine fueled with diesel oil (B5) and hydrogen (H₂). The performance parameters investigated were specific fuel consumption, effective engine efficiency and volumetric efficiency. The engine was operated varying the nominal load from 0 kW to 40 kW, with diesel oil being directly injected in the combustion chamber. Hydrogen was injected in the intake manifold, substituting diesel oil in concentrations of 5%, 10%, 15% and 20% on energy basis, keeping the original settings of diesel oil injection. The results show that partial substitution of diesel oil by hydrogen at the test conditions does not affect significantly specific fuel consumption and effective engine efficiency, and decreases the volumetric efficiency by up to 6%. On the other hand the use of hydrogen reduced CO₂ emissions by up to 12%, indicating that it can be applied to engines to reduce global warming effects.     

Numerical model to analyze Nox reduction by ammonia injection in diesel-hydrogen engines

Nowadays, the even increasing stringent environmental legislations have promoted interest in alternative fuels for internal combustion engines. Particularly, hydrogen is becoming a promising fuel due to its high specific energy and low emissions production. Environmentally, the main disadvantage of hydrogen is the high level of nitrogen oxides (NO_x) which produces. In this regard, this work proposes a NO_x reduction method which consists on direct injection of ammonia (NH₃) into the combustion chamber. A numerical model validated with experimental measurements was carried out to analyze emissions and brake specific consumption in a commercial engine operating with diesel-hydrogen blends. Comparing to diesel operation, a 10% hydrogen content increases a 5.3% the peak pressure and 5.7% the maximum temperature. The CO₂, CO and HC emissions are reduced but NO_x emissions increase up to 18.3%. Several injection instants and ammonia flow rates were analyzed, obtaining more than 70% NO_x reductions with a negligible effect on other emissions and brake specific consumption. It was found that the start of ammonia injection is too critical since the maximum NO_x reduction takes place when the temperature is around 1200 K. The NO_x reduction increases with the ammonia flow rate but an excessive quantity of ammonia can lead to un-reacted ammonia slip to the exhaust.     

Generating efficiency and emissions of a spark-ignition gas engine generator fuelled with biogas–hydrogen blends

We investigated the generating efficiency and pollutant emissions of a four-stroke spark-ignition gas engine generator operating on biogas–hydrogen blends of varying excess air ratios and hydrogen concentrations. Experiments were carried out at a constant engine speed of 1200 rpm and a constant electric power output of 10 kW. The experimental results showed that the peak values of generating efficiency, maximum cylinder pressure, and NO_x emissions were elevated at an excess air ratio of around 1.2 as the hydrogen concentration was increased. CO₂ emissions decreased as the excess air ratio and hydrogen concentration increased, due to lean-burn conditions and hydrogen combustion. An efficiency per NO_x emissions ratio (EPN) was defined to consider the relationship between the generating efficiency and NO_x emissions. A maximum EPN value of 0.7502 was obtained with a hydrogen concentration of 15%, for an excess air ratio of 2.0. At this EPN value, the NO_x and CO₂ emissions were 39 ppm and 1678.32 g/kWh, respectively, and the generating efficiency was 29.26%. These results demonstrated that the addition of hydrogen to biogas enabled the effective generation of electricity using a gas engine generator through lean-burn combustion.     

Performance assesment of hydrogen and ammonia combustion with various fuels for power generators

This paper proposes the use of hydrogen and ammonia as possible fuels for power generators and to do so the combustion is modelled by using different types of fuels which are; hydrogen, gasoline, diesel, ethanol, methanol, propane, butane and natural gas to see the effects of these fuel sources on combustion. The main aim of using a clean fuel is to decrease the greenhouse emissions, and by looking at the results, the reduction in CO₂ emissions shows that blending hydrogen and ammonia will result in a reduction for the deleterious emissions occurring after combustion. The reason behind using a dual fueled system is to make use of the secondary fuel source as a combustion promoter to help increase the low flame temperatures of ammonia that causes it not to ignite when used solely. In the modelling of combustion the maximum power output is set to 3.65 kW as this is the maximum power output for the power generator used in the experimental studies. In the studies the increase of clean fuel percentage in the fuel blend cause a reduction in the performance measures as expected with the lower energy density and lower heating values that ammonia offers but the reduction in CO₂ and NO_x emissions makes it a fuel source worth using with a combustion promoter.     

Effect of fuel injection timing and injection pressure on performance in a hydrogen direct injection engine

The in-cylinder hydrogen fuel injection method (diesel engine) induces air during the intake stroke and injects hydrogen gas directly into the cylinder during the compression stroke. Fundamentally, because hydrogen gas does not exist in the intake pipe, backfire, which is the most significant challenge to increasing the torque of the hydrogen port fuel injection engine, does not occur. In this study, using the gasoline fuel injector of a gasoline direct-injection engine for passenger vehicles, hydrogen fuel was injected at high pressures of 5 MPa and 7 MPa into the cylinder, and the effects of the fuel injection timing, including the injection pressure on the output performance and efficiency of the engine, were investigated. Strategies for maximizing engine output performance were analyzed.The fuel injection timing was retarded from before top dead center (BTDC) 350 crank angle degrees (CAD) toward top dead center (TDC). The minimum increase in the best torque ignition timing improved, and the efficiency and excess air ratio increased, resulting in an increase in torque and decrease in NO_x emissions. However, the retardation of the fuel injection timing is limited by an increase in the in-cylinder pressure. By increasing the fuel injection pressure, the torque performance can be improved by further retarding the fuel injection timing or increasing the fuel injection period. The maximum torque of 142.7 Nm is achieved when burning under rich conditions at the stoichiometric air-fuel ratio.     

Hydrogen addition effects on methane-air colorless distributed combustion flames

In this investigation the role of hydrogen addition in a reverse flow configuration, consisting of both non-premixed and premixed combustion modes, have been examined for the CDC flames. In the non-premixed configuration the air injection port is positioned at combustor exit end while the fuel injection port is positioned on the side so that the fuel is injected in cross-flow with respect to air injection. The thermal intensity of the flames investigated is 85 MW/m³ atm to simulate high thermal intensity gas turbine combustion conditions. The results are presented on the global flame signatures, exhaust emissions, and radical emissions using experiments and flowfield using numerical simulations. Ultra low NO_x emissions are found for both the premixed and non-premixed combustion modes. Addition of hydrogen to methane fuel resulted in only a slight increase of NO emission, significant decrease of CO emission and extended the lean operational limit of the combustor.     

Experimental investigation of the combustion characteristics,emissions and performance of hydrogen port fuel injection in a diesel engine

Diesel engines are indispensable in daily life. However, the limited supply of petroleum fuels and the stringent regulations on such fuels are forcing researchers to study the use of hydrogen as a fuel. In this study, a diesel engine is operated using hydrogen–diesel dual fuel, where hydrogen is introduced into the intake manifold using an LPG-CNG injector and pilot diesel is injected using diesel injectors. The energy contents of the total fuel, 0%, 16%, 36% and 46% hydrogen (the 0% hydrogen energy fraction represents neat diesel fuel), were tested at 1300 rpm of constant engine speed and 5.1 kW of constant indicated power. According to test results, the indicated thermal efficiency of the engine decreases and the isfc increases with an increasing hydrogen energy fraction. Additionally, indicated specific CO, CO₂ and smoke emissions decrease with an increasing percentage of hydrogen fuel. However, indicated specific NO_x emissions do not change at the 16% hydrogen energy fraction, in other words, with an increase in the hydrogen amount (36% and 46% hydrogen energy fraction of total fuel), a dramatic increase (58.8% and 159.7%, respectively) is observed. Additionally, the peak in-cylinder pressure and the peak heat release rate values increase with the increasing hydrogen rate.     

Analysis of CRDI diesel engine characteristics operated on dual fuel mode fueled with biodiesel-hydrogen enriched producer gas under the single and multi-injection scheme

The present work aims to investigate the consequences of pilot fuel (PF) multiple injections and hydrogen manifold injection (HMI) on the combustion and tailpipe gas characteristics of a common rail direct injection (CRDI) compression ignition (CI) engine operated on dual fuel (DF) mode. The CI engine can perform on a wide variety of fuels and under high pilot fuel (PF) pressure. Pilot fuel injection (PFI) is achieved at TDC, 5, 10, and 15ºCA before the top dead center (bTDC), and divided injection consists of injecting fuel in three different magnitudes on a time basis and PF is injected into the engine cylinder at a pressure of 600 bar. In this work, the hydrogen flow rate (HFR) was fixed at 8 lpm constant and producer gas was inducted without any restriction. The investigational engine setup has the ability to deliver a PF and hydrogen (H₂) precisely in all operating circumstances using a separate electronic control unit (ECU). Results showed that diesel-hydrogen enriched producer gas (HPG) operation at maximum operating conditions provided amplified thermal efficiency by 4.01% with reduced emissions, except NOx levels, compared to biodiesel-HPG operation. Further, DiSOME with the multi-injection strategy of 60 + 20+20 and 50 + 25+25, lowered thermal efficiency by 4.8% and 9.12%, respectively compared to identical fuel combinations under a single injection scheme. However, reductions in NOx levels, cylinder pressure, and HRR were observed with a multi-injection scheme. It is concluded that multi-injection results in lower BTE, changes carbon-based emissions marginally, and decreases cylinder pressure and heat release rate than the traditional fuel injection method.     

Research and development of a low-BTU gas-driven engine for waste gasification and power generation

Combustion characteristics of low-BTU gases (about 1000 kcal/N m³) were experimentally investigated in order to develop engine generators for waste gasification and power generation systems. Two simulated low-BTU gases, obtained from one-step high temperature gasification (hydrogen rich) and two-step pyrolysis/reforming gasification (methane rich), as well as natural gas, were tested in a small-scale spark ignition engine. Compared to the natural gas driven engine, the hydrogen rich low-BTU gas driven engine showed similar thermal efficiency but with significantly lower NO_x and hydrocarbon emissions and wider equivalence ratio range for stable engine operation. On the other hand, the methane rich low-BTU gas engine showed narrower equivalence ratio range for stable operation. The test results show engine performance more depends on combustion characteristics than on the heating value of the fuel gas. For better engine performance, hydrogen rich fuel gas is desirable.