Effect of hydrogen addition on combustion and emissions performance of a spark ignition gasoline engine at lean conditions

Hydrogen has many excellent combustion properties that can be used for improving combustion and emissions performance of gasoline-fueled spark ignition (SI) engines. In this paper, an experimental study was carried out on a four-cylinder 1.6 L engine to explore the effect of hydrogen addition on enhancing the engine lean operating performance. The engine was modified to realize hydrogen port injection by installing four hydrogen injectors in the intake manifolds. The injection timings and durations of hydrogen and gasoline were governed by a self-developed electronic control unit (DECU) according to the commands from a calibration computer. The engine was run at 1400 rpm, a manifold absolute pressure (MAP) of 61.5 kPa and various excess air ratios. Two hydrogen volume fractions in the total intake of 3% and 6% were applied to check the effect of hydrogen addition fraction on engine combustion. The test results showed that brake thermal efficiency was improved and kept roughly constant in a wide range of excess air ratio after hydrogen addition, the maximum brake thermal efficiency was increased from 26.37% of the original engine to 31.56% of the engine with a 6% hydrogen blending level. However, brake mean effective pressure (Bmep) was decreased by hydrogen addition at stoichiometric conditions, but when the engine was further leaned out Bmep increased with the increase of hydrogen addition fraction. The flame development and propagation durations, cyclic variation, HC and CO₂ emissions were reduced with hydrogen addition. When excess air ratio was approaching stoichiometric conditions, CO emission tended to increase with the addition of hydrogen. However, when the engine was gradually leaned out, CO emission from the hydrogen-enriched engine was lower than the original one. NO_x emissions increased with the increase of hydrogen addition due to the raised cylinder temperature.     

Experimental study on heat and exergy balance of a dual-fuel combined injection engine with hydrogen and gasoline

In this paper, a dual-fuel engine test rig with gasoline injected in the intake port and gasoline (or hydrogen) injected directly into the cylinder is built up; therefore, two injection models are realized. One is port fuel injection + gasoline direct injection (PFI + GDI), the other is port fuel injection + hydrogen direct injection (PFI + HDI). And the effects of two injection models on heat and exergy balance are investigated experimentally. The results show that, from the perspective of the first law of thermodynamics (heat balance), no matter what the injection mode is, the heat proportion of cooling water is the largest, the exhaust heat ratio and brake power are the second, which two are roughly equivalent, and the uncounted loss is the least. In PFI + GDI mode, the local mixture is too dense due to the increase of mixing ratio, which leads to insufficient combustion and a slight decrease of brake power ratio. However, due to the special characteristics of hydrogen, the increase of direct injection ratio improves the brake power ratio in PFI + HDI mode. Moreover, because of the short quenching distance of hydrogen, the cooling loss rises up with the increase of hydrogen ratio. The engine speed and load also have great impacts on heat distribution, but on account of the different physical and chemical properties between gasoline and hydrogen, resulting in varying degrees of impact and trends. On the basis of the second law of thermodynamics (exergy balance), it is found that no matter what injection mode is, the ratio of exergy destruction is always the highest, accounting for half of the total fuel energy, and the exhaust exergy ratio is lower than the brake power ratio. However, the proportion of exergy contained in cooling water is the smallest, which is quite different from the result of the first law of thermodynamics. The influences of several factors on engine energy balance are analyzed, and the differences and similarities between heat balance and exergy balance are compared. The two analytical methods are interrelated and complementary, and the purpose is to find a reasonable and comprehensive energy balance analysis method for internal combustion engine.     

Effects of hydrogen addition and cylinder cutoff on combustion and emissions performance of a spark-ignited gasoline engine under a low operating condition

Because of the low combustion temperature and high throttling loss, SI (spark-ignited) engines always encounter dropped performance at low load conditions. This paper experimentally investigated the co-effect of cylinder cutoff and hydrogen addition on improving the performance of a gasoline-fueled SI engine. The experiment was conducted on a modified four-cylinder SI engine equipped with an electronically controlled hydrogen injection system and a hybrid electronic control unit. The engine was run at 1400 rpm, 34.5 Nm and two cylinder cutoff modes in which one cylinder and two cylinders were closed, respectively. For each cylinder closing strategy, the hydrogen energy fraction in the total fuel (βH₂)$\left({\beta }_{{\text{H}}_2}\right)$ was increased from 0% to approximately 20%. The test results demonstrated that engine indicated thermal efficiency was effectively improved after cylinder cutoff and hydrogen addition, which rose from 34.6% of the original engine to 40.34% of the engine operating at two-cylinder cutoff mode and βH₂=20.41%${\beta }_{{\text{H}}_2}=20.41\%$. Flame development and propagation periods were shortened with the increase of the number of closed cylinders and hydrogen blending ratio. The total cooling loss for all working cylinders, and tailpipe HC (hydrocarbons), CO (carbon monoxide) and CO₂ (carbon dioxide) emissions were reduced whereas tailpipe NO_x (nitrogen oxide) emissions were increased after hydrogen addition and cylinder closing.     

Comparison of the performance of a spark-ignited gasoline engine blended with hydrogen and hydrogen–oxygen mixtures

This paper compared the effects of hydrogen and hydrogen–oxygen blends (hydroxygen) additions on the performance of a gasoline engine at 1400 rpm and a manifolds absolute pressure of 61.5 kPa. The tests were carried out on a 1.6 L gasoline engine equipped with a hydrogen and oxygen injection system. A hybrid electronic control unit was applied to adjust the hydrogen and hydroxygen volume fractions in the intake increasing from 0% to about 3% and keep the hydrogen-to-oxygen mole ratio at 2:1 in hydroxygen tests. For each testing condition, the gasoline flow rate was adjusted to maintain the mixture global excess air ratio at 1.00. The test results confirmed that engine fuel energy flow rate was decreased after hydrogen addition but increased with hydroxygen blending. When hydrogen or hydroxygen volume fraction in the intake was lower than 2%, the hydroxygen-blended gasoline engine produced a higher thermal efficiency than the hydrogen-blended gasoline engine. Both the additions of hydrogen and hydroxygen help reduce flame development and propagation periods of the gasoline engine. HC emissions were reduced whereas NOx emissions were raised with the increase of hydrogen and hydroxygen addition levels. CO was slightly increased after hydrogen blending, but reduced with hydroxygen addition.     

Analysis of the particulate emissions and combustion performance of a direct injection spark ignition engine using hydrogen and gasoline mixtures

Three different fractions (2%, 5%, and 10% of stoichiometric, or 2.38%, 5.92%, and 11.73% by energy fraction) of hydrogen were aspirated into a gasoline direct injection engine under two different load conditions. The base fuel was 65% iso-octane, and 35% toluene by volume fraction. Ignition sweeps were conducted for each operation point. The pressure traces were recorded for further analysis, and the particulate emission size distributions were measured using a Cambustion DMS500. The results indicated a more stable and faster combustion as more hydrogen was blended. Meanwhile, a substantial reduction in particulate emissions was found at the low load condition (more than 95% reduction either in terms of number concentration or mass concentration when blending 10% hydrogen). Some variation in the results occurred at the high load condition, but the particulate emissions were reduced in most cases, especially for nucleation mode particulate matter. Retarding the ignition timing generally reduced the particulate emissions. An engine model was constructed using the Ricardo WAVE package to assist in understanding the data. The simulation reported a higher residual gas fraction at low load, which explained the higher level of cycle-by-cycle variation at the low load.     

Energy and exergy analysis of a combined injection engine using gasoline port injection coupled with gasoline or hydrogen direct injection under lean-burn conditions

Hydrogen is considered to be a suitable supplementary fuel for Spark Ignition (SI) engines. The energy and exergy analysis of engines is important to provide theoretical fundaments for the improvement of energy and exergy efficiency. However, few studies on the energy and exergy balance of the engine working under Hydrogen Direct Injection (HDI) plus Gasoline Port Injection (GPI) mode under lean-burn conditions are reported. In this paper, the effects of two different modes on the energy and exergy balance of a SI engine working under lean-burn conditions are presented. Two different modes (GPI + GDI and GPI + HDI), five gasoline and hydrogen direct injection fractions (0, 5%, 10%, 15%, 20%), and five excess air ratios (1, 1.1, 1.2, 1.3, 1.4) are studied. The results show that the cooling water takes the 39.40% of the fuel energy on average under GPI + GDI mode under lean-burn conditions, and the value is 40.70% for GPI + HDI mode. The exergy destruction occupies the 56.12% of the fuel exergy on average under GPI + GDI mode under lean-burn conditions, and the value is 54.89% for GPI + HDI mode. The brake thermal efficiency and exergy efficiency of the engine can be improved by 0.29% and 0.31% at the excess air ratio of 1.1 under GPI + GDI mode on average, and the average values are 0.56% and 0.71% for GPI + HDI mode.     

Investigations on the effects of intake temperature and charge dilution in a hydrogen fueled HCCI engine

This work was aimed at improving the performance and extending the load range of hydrogen fueled homogeneous charge compression ignition (HCCI) engine through charge temperature regulation and addition of carbon dioxide in order to control the combustion phasing. Intake charge temperature and equivalence ratio were varied from 130 °C to 80 °C and 0.19 to 0.3 respectively. In the neat hydrogen mode it was possible to operate the engine only until a brake mean effective pressure (BMEP) of 2.2 bar. Higher charge temperatures lead to knocking and advanced combustion. At any equivalence ratio the lowest possible charge temperature is the one that leads to the highest thermal efficiency. Addition of carbon dioxide retarded the combustion process and improved the thermal efficiency and also extended the load range to a BMEP of 3.1 bar. Efficiencies of hydrogen HCCI mode were higher than the conventional diesel mode with negligible level of NO emissions.     

Combustion,performance and emission analyses of a CI engine operating with renewable diesel fuels (HVO/FARNESANE) under dual-fuel mode through hydrogen port injection

The use of hydrogen in internal combustion engines is pointed out as an alternative to reduce greenhouse gas emissions. In applications that require high levels of torque and low engine speeds, compression ignition (CI) engines are more appropriate. However, because of the high auto-ignition temperature of hydrogen, its use in these engine types is more suitable when the dual-fuel concept is applied. This study comprehensively investigates, through experimental techniques, the use of hydrogen port-injection in a four-stroke single-cylinder CI engine operating with the renewable diesel-like fuels hydrotreated vegetable oil (HVO) and farnesane, in comparison to fossil diesel dual-fuel operation. In this sense, the present work aims to fill a gap in the literature by performing a novel analysis of dual-fuel operation with hydrogen, considering different substitution fractions, and using groundbreaking biofuels, such as HVO and farnesane. The results showed that in-cylinder pressure and temperature were increased with H₂ enrichment for every pilot fuel, but green diesel fuels presented lower values than those for diesel operation. Furthermore, hydrogen port injection slightly delayed the start of combustion and increased the ignition delay, but a reduction in both premixed and diffusion combustion duration was observed. Reductions in PM, CO, and CO₂ emissions were reported during H₂ addition for every pilot fuel, while increased NO_x was observed. Despite this increase, both HVO and farnesane decreased the emissions of this pollutant in single and dual-fuel operations, compared with fossil diesel. In addition, both renewable diesel fuels presented higher BTE than diesel for every studied H₂ mass flow.     

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.     

Influence of hydrogen peroxide emulsification with gasoline on the emissions and performance in an MPFI engine

Spark ignition (SI) engines have been a major contributor from the transportation sector towards the increased emissions to the environment. Modifications to the SI engine like structural modifications, pre, and post-combustion treatments have been investigated in the literature. The use of oxygenated additives to gasoline fuel has been major research interest in curbing the emissions without any significant loss in engine performance. Hydrogen peroxide (H₂O₂) has not been investigated as an additive in SI engines although its effect is demonstrated for compression ignition (CI) engines. This paper aims to address this gap by ascertaining the influence of H₂O₂ concentration on SI engine emissions and performance. H₂O₂ is varied from 0 to 1.5% and the engine speed varied from 1500 to 3000 rpm by operating at a constant load. A total of 16 trials (with three replicates) is carried out. The output responses are brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), emissions of CO, CO₂, HC, and NOx. Artificial neural networks are adopted to ascertain the relation between the inputs and the output responses. Emulsifying gasoline with 1.5% H₂O₂ resulted in an average reduction of CO and HC emissions by 21.1% and 28.6% respectively with an overall average of 25.3% of reduction in the NOx. The average BTE at all engine speeds increases from 21.6% for G0 to 23.8% for G1.5 and an overall average of 10.5% reduction in BSFC is obtained. The study shows that H₂O₂ can be employed as an emulsifier to gasoline fuel, however, more rigorous studies are required to ascertain its impact, volatility, and storage.     

Examination of the effect of combustion chamber geometry and mixing ratio on engine performance and emissions in a hydrogen-diesel dual-fuel compression-ignition engine

The fact that fossil fuels, which supply a large amount of the energy need, are limited in the world and can be only found in certain regions, have led humankind to seek alternatives. In addition, the use of fossil fuels generates wastes detrimental to humans and nature, which has led this search to alternative, clean and renewable energy sources. The use of hydrogen, which is a clean energy source, in internal combustion engines is very important in terms of reducing emission values as well as providing an alternative to petroleum-derived fuels. This study presents a literature review on the effect of the hydrogen ratio and combustion chamber geometry on the engine performance and emissions in a compression-ignition engine operating in the hydrogen diesel bi-fuel mode. As a result of the study, it was concluded that the hydrogen energy ratio should be between 5 and 20% and the combustion chamber should be designed by considering the combustion characteristics. The main purpose of the study is to highlight the functionality of the use of hydrogen in dual fuel mode in compression ignition engines and to be a resource for researchers who will work on this subject.     

The effects of hydrogen on the combustion,performance and emissions of a turbo gasoline direct-injection engine with exhaust gas recirculation

The effects of hydrogen on the combustion characteristics, thermal efficiency, and emissions of a turbo gasoline direct-injection engine with exhaust gas recirculation (EGR) were investigated experimentally at brake mean effective pressures of 4, 6, and 8 bar at 2000 rpm. Four cases of hydrogen energy fraction (0%, 1%, 3% and 5%) of total fuel energy were studied. Hydrogen energy fraction of total fuel energy was hydrogen energy in the sum of energy of consumed gasoline and added hydrogen. The test results demonstrated that hydrogen addition improved the combustion speed and reduced cycle-to-cycle variation. In particular, cylinder-to-cylinder variation dramatically decreased with hydrogen addition at high EGR rates. This suggests that the operable EGR rate can be widened for a turbo gasoline direct-injection engine. The improved combustion and wider operable EGR rate resulted in enhanced thermal efficiency. However, the turbocharging effect acted in opposition to the thermal efficiency with respect to the EGR rate. Therefore, a different strategy to improve the thermal efficiency with EGR was required for the turbo gasoline direct-injection engine. HC and CO₂ emissions were reduced but NO_X emissions increased with hydrogen addition. The CO emissions as a function of engine load followed different trends that depended on the level of hydrogen addition.     

Numerical study on effects of hydrogen direct injection on hydrogen mixture distribution,combustion and emissions of a gasoline/hydrogen SI engine under lean burn condition

A numerical study on effects of hydrogen direct injection on hydrogen mixture distribution, combustion and emissions was presented for a gasoline/hydrogen SI engine. Under lean burn conditions, five different direct hydrogen injection timings were applied at low speeds and low loads on SI engines with direct hydrogen injection (HDI) and gasoline port injection. The results were showed as following: firstly, with the increase of hydrogen direct injection timing, the hydrogen concentration near the sparking plug first increases and then decreases, reaching the highest when hydrogen direct injection timing is 120°CA BTDC: Secondly, hydrogen can speed up the combustion rate. The main factor affecting the combustion rate and efficiency is the hydrogen concentration near the sparking plug: Thirdly, in comparing with gasoline, the NO_X emissions with hydrogen addition increase by an average of 115%. For different hydrogen direct injection timings, the NO_X emissions of 120°CA BTDC is the highest, which is 29.9% higher than the 75°CA BTDC. The hydrogen addition make the NO_X emissions increase in two ways. On the one hand, the average temperature with hydrogen addition is higher. On the other hand, the temperature with hydrogen addition is not homogeneous, which makes the peak of temperature much higher. In a word, the main factor of NO_X emissions is the size of high temperature zone in the cylinder: Finally, because the combustion is more complete, in comparing with gasoline, hydrogen addition can reduce the CO and HC emissions by 32.2% and 80.4% respectively. Since a more homogeneous hydrogen mixture distribution can influence a lager zone in the cylinder and reduce the wall quenching distance, these emissions decrease with the increase of hydrogen direct injection timing. The CO and HC emissions of 135°CA BTDC decrease by 41.5% and 71.4%, respectively, compared to 75°CA BTDC.     

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.     

Multi-objective optimization of a hydrogen production through the HyS process powered by solar energy in different scenarios

Thermochemical or hybrid cycles powered by concentrated solar energy are a very promising way to produce an effective clean hydrogen through the water splitting, in terms of greenhouse gas (GHG) emissions and power production sustainability. SOL2HY2 is an European project focused on this goal. It deepens the so-called HyS process in a closed or partially open version using a proper SO₂ depolarized electrolyser, and moreover, it investigates key materials and process solutions, along the entire production chain. However, the identification of the best solution to obtain a suitable hydrogen in terms of cost, efficiency, availability of energy and material, sharing of renewable energy source, continuity of operation in different locations and plant sizes, poses many challenges in terms of flexibility and complexity of the system. In fact, it involves various chemical equipment, different solar and thermal storage technologies, and variable operative conditions with different reaction temperatures and mixture concentrations. Hence it arises the importance to have a tool for the investigation of this system.In this paper, data analysis and multi-objective techniques are used to study and optimize the process under consideration. Several mathematical methods have been exploited to make the best use of the available data, such as Design of Experiments techniques, meta-modeling strategies and genetic algorithms. All these methods have been implemented in the open source environments Scilab and R.     

Numerical analysis of performance and emissions behavior of a bi-fuel engine with compressed natural gas enriched with hydrogen using variable compression ratio strategy

The increase in the compression ratio reduces the fuel consumption and improves the performance. These effects of compression ratio could be observed in all of the engines, such as compression or spark ignition engines. Moreover, due to the compression ratio constraint based on the knocking phenomenon in spark ignition engines, there will always be an optimal compression ratio, which is one of the most fundamental factors in engine design. The optimum compression ratio could be achieved depending on the type of fuel, but in the case of bi-fuel engines, since the nature of each fuel is different, the design must be relatively optimal for both fuels. In this work, by using the VCR (variable compression ratio) strategy, the bi-fuel EF7 engine performance, combustion, and emissions were investigated in different compression ratios when the engine uses gasoline or HCNG (hydrogen enriched compressed natural gas) as fuel. The results revealed that by changing the compression ratio from 11.05 (actual compression ratio of engine) to 11.80 in HCNG mode, an increase of 13% in power could be achieved. Also CO formation, at the compression ratio of 11.80, was slightly lower (7%) than the compression ratio of 11.05. In addition, by reducing the compression ratio from 11.05 to 10.50 in gasoline mode, there was a significant increase in emissions; that was 44% for the NO_x and 16% for the CO, which could be one of the limiting factors of the advance in spark timing. Moreover, due to the VCR strategy and the significant optimization of the compression ratio, the combinatory method of VCR – HCNG can be used as an effective method for the bi-fuel engines in order to improve the performance and reduce emissions.     

Design,modeling and optimization of a renewable-based system for power generation and hydrogen production

Due to the environmental concerns caused by fossil fuels, renewable energy systems came into consideration. In this study, a renewable hybrid system based on ocean thermal, solar and wind energy sources were designed for power generation and hydrogen production. To analyze the system, a techno-economic model was exerted in order to calculate the exergy efficiency as well as the cost rate and the hydrogen production. The main parameters that affect the system performance were identified, and the impact of each parameter on the main outputs of the system was analyzed as well. The thermo-economic analysis showed that the most effective parameters on the exergy efficiency and total cost rate are the wind speed and solar collector area, respectively. To reach the optimum performance of the system, multi-objective optimization, by using genetic algorithm, was applied. The optimization was divided into two separate case studies; in case A, the cost rate and the exergy efficiency were considered as two objective functions; and in case B, the cost rate and the hydrogen production were assigned as two other objective functions. The optimization results of the case A showed that for the total cost rate of 30.5 $/h, the exergy efficiency could achieve 35.57%. While, the optimization of the case B showed that for the total cost rate of 28.06 $/h, the hydrogen production rate could reach 5.104 kg/h. Furthermore, after optimizing, an improvement in exergy efficiency was obtained, approximately 19%.     

Effects of hydrogen injection strategy on the hydrogen mixture distribution and combustion of a gasoline/hydrogen SI engine under lean burn condition

Hydrogen is a carbon free energy carrier with high diffusivity and reactivity, it has been proved to be a kind of suitable blending fuel of spark ignition (SI) engine to achieve better efficiency and emissions. Hydrogen injection strategy affects the engine performance obviously. To optimize the combustion and emissions, a comparative study on the effects of the hydrogen injection strategy on the hydrogen mixture distribution, combustion and emission was investigated at a SI engine with gasoline intake port injection and four hydrogen injection strategies, hydrogen direct injection (HDI) with stratified hydrogen mixture distribution (SHMD), hydrogen intake port injection with premixed hydrogen mixture distribution (PHMD), split hydrogen direct injection (SHDI) with partially premixed hydrogen mixture distribution (PPHMD) and no hydrogen addition. Results showed that different hydrogen injection strategy formed different kinds of hydrogen mixture distribution (HMD). The ignition and combustion rate played an important role on engine efficiency. Since the SHDI could use two hydrogen injection to organize the HMD, the ignition and combustion rate with the PPHMD was the fastest. With the PPHMD, the brake thermal efficiency of the engine was the highest and the emissions were slight more than that with the PHMD. PHMD achieve the optimum emission performance by its homogeneous hydrogen. The engine combustion and emission performance can be optimized by adjusting the hydrogen injection strategy.     

Direct injection of hydrogen, oxygen and water in a novel two stroke engine

This short communication proposes novel two stroke engine burning hydrogen in oxygen in presence of large amounts of steam as residual gases. This engine has a bowl-in-piston combustion chamber, exhaust valves only and it uses direct injection of hydrogen, oxygen and water. Diesel-like compression ignition combustion is achieved by injecting the oxygen and the hydrogen in the surrounding steam close to a continuously operated glow plug. The operation of the engine is simulated by commercial softwares. The water injection enables acceptable metal temperatures and reduced heat losses. First computational results show brake efficiencies above 55% achieved with mass of water injected about twice the mass of oxygen and hydrogen mixture and operation with a significant amount of exhaust gas recirculation. It seems reasonable to guess efficiencies of the fully optimised and developed engine approaching the 60% mark, 20% higher than those of the state-of-the-art H₂ICEs designed for operation with air using the spark-ignition engine concept as well as of those projected for Diesel engines operating with exhaust energy recovery. Worth of mention is also the much higher power density following the two stroke operation.