Hydrogen Energy Fraction Research Articles

Characterizing hydrogen-diesel dual-fuel performance and emissions in a commercial heavy-duty diesel truck

This study investigates hydrogen (H2) as a supplementary fuel in heavy-duty diesel engines using pre-manifold injection. A H2-diesel dual-fuel (H2DF) system was implemented on a commercial class-8 heavy-duty diesel truck without modifying the original diesel injection system and engine control unit (ECU). Tests were conducted on a chassis dynamometer at engine speeds between 1000 and 1400 rpm with driver-demanded torques from 10 to 75%. The hydrogen energy fraction (HEF) was strategically controlled in the range between 10 and 30%. Overall, CO2 reduction (comparable to the HEF level) was achieved with similar brake-specific energy consumption (BSEC) at all loads and speeds. To maintain the same shaft torque, the driver-demanded torque was reduced in H2DF operation, which resulted in a lower boost pressure. At higher loads, engine-out BSNOx slightly decreased, while BSCO and black carbon (BC) increased significantly due to lower oxygen concentration resulting from the lower boost pressure. At lower loads, engine-out BSCO and BSBC decreased moderately, while NO2/NO ratio increased substantially in H2DF operation. Deliberate air path and diesel injection control are expected to enable higher HEF and GHG reductions.

Numerical investigation of the hydrogen-enriched ammonia-diesel RCCI combustion engine

Incorporating hydrogen into the fuel blend of ammonia/diesel in reactivity controlled compression combustion (RCCI) engines, while maintaining high indicated mean effective pressure (IMEP) and combustion efficiency (CE), presents a promising approach for mitigating nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), unburnt ammonia emissions and nitrous oxide (N2O) greenhouse gas (GHG)-a pressing challenge in the field. By supplementing ammonia/diesel combustion with hydrogen, potential issues related to incomplete combustion can be mitigated, along with a reduction in intake valve close temperature (TIVC). This study aims to assess the impact of hydrogen enrichment on combustion characteristics in RCCI engines utilizing ammonia and diesel as fuels, employing the kinetic mechanism of combustion reactions within Converge software. The effect of TIVC on key engine parameters, including in-cylinder pressure, heat release rate (HRR), CE, IMEP, and exhaust emissions, are analyzed by considering chemical reaction pathways. The findings reveal that introducing hydrogen into the ammonia /diesel RCCI combustion blend, leads to significant enhancements in CE and IMEP while simultaneously lowering emissions of CO, HC, unburnt ammonia, and N2O greenhouse gas (GHG). Specifically, when utilizing 80 % ammonia energy fraction (AEF) without hydrogen, minimum TIVC of 440 K is necessary to prevent incomplete combustion, increasing NOx emissions by approximately 20 g/kWh. However, by addition of 20 % hydrogen energy fraction (HEF) into the fuel mixture, the TIVC requirement drops to 380 K, thereby reducing NOx emissions to around 13 g/kWh, while maintaining consistent level of N2O GHG (2.7 g/kWh).

Split injection strategies for a high-pressure hydrogen direct injection in a small-bore dual-fuel diesel engine

Hydrogen-diesel dual direct-injection (H2DDI) engines present a promising pathway towards cleaner and more efficient transportation. In this study, hydrogen split injection strategies were explored in an automotive-size single-cylinder compression ignition (CI) engine, with a focus on varying the injection timings and energy fractions. The engine was operated at an intermediate load with fixed combustion phasing through adjustments of pilot diesel injection timing. An energy substitution principle guided the variation in energy fraction between the two hydrogen injections and then diesel injection while keeping the total energy input constant. The findings demonstrate that early first hydrogen injection timings lead to characteristics indicative of premixed combustion, reflecting a high homogeneity of the hydrogen-air mixture. In contrast, hydrogen stratification levels were predominantly influenced by later second injection timings, with mixing-controlled combustion behaviour apparent for very late injections near top dead centre or when the second hydrogen injection held high energy fractions, which led to decreased nitrogen oxides (NOx: NO and NO2) emissions. The carbon dioxide (CO2) emissions did not show high sensitivity to the hydrogen split injection strategies, exhibiting about 77 % reduction compared to the diesel baseline due primarily to increased hydrogen energy fraction of up to 90 %.

Enhancing ammonia engine efficiency through pre-chamber combustion and dual-fuel compression ignition techniques

In pursuit of unleashing ammonia’s potential in internal combustion engines, an extensive computational study was conducted to explore the effects of two advanced combustion techniques: pre-chamber combustion (PCC) and dual-fuel compression ignition (DF−CI) on a heavy-duty ammonia engine. In the PCC mode, hydrogen was introduced into the pre-chamber (PC) to generate distributed reacting jets, with a small energy fraction of 0.5%. The case featuring a slightly narrower PC throat (diameter of 5.4 mm) yielded the highest indicated thermal efficiency (ITE) of 50.4%, owing to the rapid distribution of reacting jets and advanced combustion phasing. Further increase in hydrogen energy fraction and reduction in throat diameter resulted in a lower ITE because of the enhanced wall heat transfer loss. The DF−CI mode also exhibited significant potential for achieving high efficiency. Through a systemic optimization of parameters such as diesel injection timing, spray included angle, injection pressure, swirl ratio, and piston shape, a significantly enhanced ITE of 50.3% was attained, 7.2% higher than the baseline scenario. The improvement was primarily attributed to the promoted mixing of diesel with air. Among the design parameters, the swirl ratio and spray included angle exhibited the most significant impact on the engine performance. Overall, both the PCC and DF−CI modes were found to yield high ITE and low ammonia emissions. However, because 20% of the diesel energy fraction was utilized to mitigate ammonia slip in the DF−CI mode, notably higher greenhouse gas emissions (carbon dioxide of 96 g/kW-h) were generated than in the PCC mode. In this regard, the ammonia-hydrogen PCC mode should be a more promising solution to achieve zero-carbon emissions for future ammonia engines.

Investigation on flame propagation and end-gas auto-ignition of ammonia/hydrogen in a full-field-visualized rapid compression machine

Ammonia-hydrogen engine has attracted much attention due to its carbon-free nature. Given that ammonia has high knock resistance (indicated by its high research octane number of nearly 130), researchers are trying to increase the compression ratio (CR) to improve engines’ thermal efficiency. However, knocking cycles can still be detected in ammonia-hydrogen engines under elevated thermodynamic conditions. To further explore the ammonia-hydrogen knocking process, this study conducted a series of spark-ignition combustion experiments focusing on flame propagation and end-gas auto-ignition in a full-field-visualized rapid compression machine. Four ammonia-hydrogen blended fuels with hydrogen energy fractions of 0 % (H0), 10 % (H10), 20 % (H20), and 100 % (H100) were comparatively tested under the thermodynamic conditions of 30 bar and 750–985 K. The experimental results showed that the flame speed of H0, H10, and H20 is around 3–6 m/s under test conditions, much lower than that of H100, which exceeds 37 m/s at 30 bar/750 K. Strong end-gas auto-ignitions with maximum pressure amplitudes of 77 bar and 101 bar were recorded for H0 at 30 bar/985 K and H10 at 30 bar/915 K, respectively. The two auto-ignition events both exhibited detonation characteristics by clear wavefronts with speeds reaching up to 1620 m/s (H0) and 1812 m/s (H10). Based on the experimental results, simulations were carried out to analyze the chemical process during the end-gas auto-ignition. The simulated results showed that for H0 at 30 bar/985 K, the NO-, NO2-, and H2NO-related reactions contributed most to heat production, which improved the end-gas reactivity and promoted the occurrence of auto-ignition. For H10 at 30 bar/915 K, the H + O2 (+M) = HO2 (+M) became the most exothermic reaction, indicating the hydrogen addition significantly promoted the ammonia's end-gas auto-ignition. Additionally, the detonation events observed in this study can be well classified in the ε -ξdiagram.

Diesel Substitution with Hydrogen for Marine Engines

Zero-carbon fuels are expected to catalyse the decarbonisation of the maritime industry, with hydrogen being considered a long-term solution. This study aimed to investigate the feasibility of using hydrogen as a secondary fuel in marine diesel engines. A marine four-stroke engine with a nominal power output of 10.5 MW at 500 rpm was investigated, whereas the hydrogen injection at the engine port was considered. A CFD model was set up in CONVERGE for both diesel and the diesel-hydrogen operating modes to investigate the effects of 20% hydrogen fuel fraction (by energy) on engine performance, emissions, and combustion characteristics. This model was validated against experimental data for the diesel operating mode. Based on a parametric study, the mesh characteristics were selected to compromise between the prediction error and the computational effort. The impact of 20% hydrogen energy fraction on the heat release rate (HRR) and NOx emissions is comparing with the diesel mode. The results demonstrate that despite the reduction in carbon emissions when using hydrogen, the NOx emissions increase by 2.5 times, whereas the lower compression ratio allows for engine free-knock operation. This study contributes to the identification of efficient and reliable combustion conditions for diesel-hydrogen dual-fuel marine engines.

Study on lean combustion of ammonia-hydrogen mixtures in a pre-chamber engine

Ammonia holds promise for achieving zero carbon emissions from internal combustion engines. The pre-chamber turbulent jet ignition, characterized by multipoint distributed ignition and rapid combustion, could be applied to ammonia combustion to extend combustion limits and stability. This study investigates the impacts of hydrogen energy fraction (Hfrac), equivalence ratio, and ignition timing on the combustion and emission characteristics of ammonia-hydrogen mixture at lean combustion conditions in a pre-chamber (PC) marine engine by CFD Simulation. In H2-fuel active PC mode, increasing the hydrogen content or achieving stoichiometric combustion within the PC will shorten the cold jet phase and accelerate the formation of a more intense hot jet. As the Hfrac and the equivalence ratio in the main-chamber increase, the combustion pressure, temperature, and heat release rate (HRR) rise, while the combustion duration shortens due to enhanced reactivity, potentially leading to end gas auto-ignition and knock due to lower auto-ignition energy of the mixture. NO primarily forms near the flame front, and both NO concentration and the generation area increase with an increase in hydrogen content and equivalence ratio. Fuel-NO is likely to be the dominant factor in NO generation with lean combustion conditions. N2O, as a product of NH3 low-temperature combustion, is mainly concentrated near the flame front. An increase in unburned NH3 emissions corresponds to an increase in N2O emissions. Delaying the ignition timing to reduce NOx emissions is primarily achieved by controlling NO emissions, even though there is a slight increase in N2O.

Numerical simulation of methane slip from marine dual-fuel engine based on hydrogen-blended natural gas strategy

This study examines the effect of a hydrogen-blended natural gas strategy on methane slip in two-stroke marine engines using numerical simulation. A combined simulation model, integrating a 1-D engine model from GT-POWER and a 3-D CFD model from CONVERGE, was developed and validated with experimental data. Subsequently, the effects of hydrogen molar fraction and energy fraction on methane slip were investigated. It was demonstrated that an appropriate hydrogen doping ratio in natural gas can effectively reduce methane slip. The methane slip decreased with an increase in the hydrogen molar fraction. The maximum reduction in methane slip was 26.76% when the molar fraction of hydrogen was 40% and the equivalent CO2 emission decreased by 142.78 g/kWh. Furthermore, with an enhanced energy fraction of hydrogen, a decrease in methane slip from 10.00 g/kWh to 5.83 g/kWh was observed. The CO2 emission was reduced by 143.86 g/kWh, and the equivalent CO2 emission (CO2 + 36 × CH4) was reduced by 293.80 g/kWh. However, there was a slight increase in indicated specific fuel consumption by 0.03 g/kWh and a decrease in power output by 54.6 kW. The findings offer theoretical guidance and technical suggestions for mitigating methane slip in marine dual fuel engines.

Effectiveness of hydrogen enrichment strategy for Wankel engines in unmanned aerial vehicle applications at various altitudes

This study investigates the effectiveness of the hydrogen-enrichment strategy on a Wankel engine for unmanned aerial vehicles (UAVs). The primary motivation behind this study is to contribute to the Wankel-type rotary engine designs by revealing the influences of the hydrogen enrichment method on the Wankel engine performance at various altitudes. To achieve these objectives, CFD simulations were conducted by applying a hydrogen enrichment method to a neat gasoline Wankel engine model at sea level, 5000 ft and 15,000 ft altitudes. The hydrogen energy fraction at the intake was gradually increased from 0% to 10%. The decrease in ambient air temperature, pressure, density, and insufficient fresh charge with the increase in altitude leads to the reduced reference chamber temperature and pressure of the Wankel engine. Thus, the combustion worsens, the heat release rate (HRR) and performance decrease, also emissions deteriorate in these colder operating conditions. On the other hand, the unique physicochemical properties of hydrogen such as wide flammability limits, high homogeneity, relatively small quenching distance and high flame speed allow hydrogen-enriched mixture flames to propagate toward the narrower gaps in the combustion chamber and make up for some drawbacks of Wankel engines. As a result, flame propagation is accelerated and fuel burning rate, peak pressure and temperature values in the reference chamber are increased by hydrogen addition. For the cases at sea level with 5% and 10% hydrogen energy fraction, IMEP is increased by 6.59%, 8.50%, and the indicated power is increased by 35.51% and 52.47%. In the cases with the same energy fraction at 15,000 ft, IMEP is increased by 26.61% and 48.75%, and the indicated power is reduced by 26.61% and 48.75%, respectively. It has been proven that a small amount of hydrogen by energy fraction improves combustion efficiency and performance. The findings show that hydrogen has excellent compatibility with Wankel engines and hydrogen enrichment is a very practical concept for the improvement of the performance of these engines for UAVs. Thus, Wankel engines, which are already a very favorable power source for UAVs, become even more favorable by the hydrogen-blending strategy.

Visualization and simulation study of ammonia blending with hydrogen as combustion application in lean-burn condition

Ammonia (NH3), as one of the two zero-carbon fuels, has attracted lots of attention. However, its poor properties, including slow laminar burning velocity (LBV), high ignition energy, and low flammability, make it unfavorable for use in engines. On the other hand, hydrogen (H2), another zero-carbon fuel, has a much higher LBV and flammability. Adding a certain amount of hydrogen to ammonia mixture has the potential to improve the combustion process and extend the lean-burn limit of ammonia. This paper investigates the combustion and emission improvements of ammonia blended with a small amount of hydrogen under lean-burn conditions, both experimentally and numerically. A new NH3/H2 chemical reaction mechanism was developed to accurately predict ignition delay time (IDT), LBV and NO generation under a wide range of initial conditions. The flame propagation schlieren and NO chemiluminescence measurements with a homogenous NH3/H2 mixture ignited by a spark plug in constant volume combustion chamber (CVCC) were conducted. The 3D numerical simulations in CVCC, coupled with the new mechanism, were validated with the experimental results. The hydrogen energy fraction up to 30 % (X30) and ER down to 0.4 (ER0.4) were studied in experiments and simulations. The results showed that, in comparison to pure ammonia (X0) at ER1.0, lean-burn conditions can be extended to ER0.6 and ER0.4 for X10 and X30, respectively, while still achieving a shorter combustion duration. NO is initially increased and then decreased with decreasing ER, regardless of hydrogen addition. Comparatively, X30ER0.4 can achieve relatively low NOx emissions, and maintaining an equivalent combustion rate with a low combustion temperature.

Experimental investigation of variable compression ratio and ignition timing effects on performance, combustion, and Nox emission of an ammonia/hydrogen-fuelled Si engine

In the present experimental study hydrogen-assisted ammonia combustion strategy is used in a SI engine with variable ignition timings (18ºCA bTDC to 32ºCA bTDC) and wide-open throttle conditions, CR changes (14–16) at 1400RPM and 1800RPM. This article aims to optimize ignition timing to boost efficiency and power without knocking. It has been established that ammonia/hydrogen fuels are a clean energy source capable of reducing pollution caused by undesirable emissions. The results revealed that increasing the CR from 14 to 16 increased brake power, brake thermal efficiency, NOX, cylinder pressure, and net heat release rate by 36.82%, 25.11%, 30.21%, 10.35%, and 9.53%, respectively. CA10-90 and EGT, on the other hand, are reduced. Increased speed reduces volumetric efficiency by 9.5% at 1800 RPM. In each CR, 28ºCA bTDC ignition timing and 21% hydrogen energy fraction performed well, which can be observed. Hence, the experiment results indicate hydrogen can be used as a combustion promoter, establishing a new standard for developing ammonia-fuelled engines.

Effect of the hydrogen/kerosene blend on the combustion characteristics and pollutant emissions in a mini jet engine under CDC conditions

In this CFD study conducted with the geometry of a mini gas turbine engine using kerosene as fuel, colorless distributed combustion conditions were achieved by increasing the N2 ratio in the air. Then, H2 was added to the kerosene fuel in order to increase the combustion performance and the combustion chamber temperature distributions, NOx, CO, and CO2 values were examined. In the simulations using the simplified GTM-120 geometry, the combustion chamber outlet temperatures at 80 k, 100 k, and 120 k rpm were compared with the experimental results in the literature by changing the ratio of fuel and air for the validation study. Standard k-ε and Discrete Ordinates were chosen for turbulence and radiation models, respectively. In the study conducted with the non-premixed combustion model, simulations were made at O2 rates of 21%, 19%, 17%, and 15% for the formation of colorless distributed combustion conditions. For enrichment with hydrogen, H2 was added from 0% to 50% with 10% increments. HEF (Hydrogen energy fraction) has been used as the hydrogen addition rate. In light of the analyses made, it was seen that the colorless distributed combustion regime reduced the flame temperature from 2292 K to 1912 K and the NOx amount from 2.85 ppm to 0.0086 ppm. On the other hand, it is seen that this regime increased the CO emissions from 6.9 ppm to 38.67 ppm and the mole ratio of CO2 from 6.25% to 6.94%. It was observed that these findings prepared the ground for increasing the amount of hydrogen in the fuel, which increases the flame temperature and, accordingly, NOx emissions. By adding 50% H2 to kerosene under standard atmospheric conditions, the average NOx emission at the combustion chamber outlet increased from 2.85 ppm to 7.97 ppm, while the average CO emission decreased from 6.9 ppm to 1.08 ppm. As a matter of fact, by the addition of 50% H2 to the kerosene with air that contains 15% O2, which is the most extreme combustion situation in this study, the flame temperature decreased to 1912 K, and NOx rose to 0.0713 ppm. However, the CO emissions at the combustion chamber outlet decreased to 1.83 ppm and the CO2 ratio to 3.48%. Thus, with this study, it has become possible to use hydrogen as an alternative fuel in a real engine geometry by using CDC and hydrogen enrichment together, both in terms of pollutant emissions and combustion performance.

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 NOx 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 NOx increase is inevitable due to enhanced premixed combustion. To keep the NOx 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.

Effects of compression and mixing ratio on NH3/H2 fueled Si engine performance, combustion stability, and emission

• NH 3 /H 2 are attractive alternative fuels for the worldwide decarbonization movement. • H 2 is an excellent ammonia additive because it eliminates the cold start problem. • The combustion of ammonia/hydrogen reduces fuel waste while increasing BP. • There are no greenhouse gas emissions from ammonia/hydrogen combustion. • As a result, it appears that fuel NOx predominates over thermal NOx. Carbon-free fuels for the worldwide decarbonization movement are ammonia and hydrogen. The experiment is conducted under WOT conditions with a constant ignition timing of 24°CA BTDC to evaluate performance, combustion stability, and emissions with varying CR (12 to 15), hydrogen energy fractions (5 to 21%), and engine speeds between 1500 and 1700 RPM. BP increased by 31.2% at 1700RPM and BTE increased by 39.0% at 1500RPM, despite a 9% decrease in volumetric efficiency at 1700RPM, from 5% hydrogen fraction at CR12 to 21% hydrogen fraction at CR15.The combustion process is sped up by the effect of hydrogen fraction and CR, causing the flame development and propagation period to shorten. NOx emission was increased significantly with hydrogen and CR, with an increase of 42.34% from 5% hydrogen at CR12 to 21% hydrogen at CR15 at 1700 RPM. Excessive NOx emissions are a drawback that can be successfully controlled by installing after treatment or exhaust gas recirculation technologies. Ammonia is another important key element used to reduce NOx emissions from vehicles because it is used in SCR.

Emissions and Performance of a Hybrid Hydrogen-gasohol E20 Fueled Si Engine

T his paper has investigated the effects of an alternative hybrid hydrogen-gasohol E20 fueled spark ignition engine on engine performance and exhaust pollutants. A hydrogen mixture with gasohol E20 was performed in an external mixture formation by installing a hydrogen fuel injection kit into the intake manifold area which is responsible for injecting hydrogen fuel into the inside of the engine’s cylinder. The hydrogen energy fraction in the intake was gradually increased from 3% to 9% ignition degree in the range of 20°, 25°, 30° and 35° before top dead center were controlled by using the electronic control unit to study the optimal condition for a four-stroke single-cylinder engine. In the steady-state test condition with half-open throttle under the variable load engine at 28%, 42%, 56%, and 70% of maximum engine torque, the engine can be available satisfactorily for an average relative air-fuel ratio (λ) value of 1.2 for hybrid hydrogen-gasohol E20 fuel. The results indicated that when the increase of hydrogen volume fraction. Postponing the spark timing was closer to top dead center (TDC) at 25° BTDC, the brake power and thermal engine efficiency increases. It is also noted that postponing the spark timing also caused NOx, HC and CO emissions to decrease. NOx emissions increased as the hydrogen volume fraction increased, whereas HC and CO emissions decreased.

The effect of euro diesel-hydrogen dual fuel combustion on performance and environmental-economic indicators in a small UAV turbojet engine

This paper aims to examine the effect on performance and environmental-economic indicators of euro diesel-hydrogen dual-fuel combustion in a small turbojet engine suitable for the propulsion system of unmanned air vehicles (UAVs). For this purpose, experimental studies were conducted at seven different engine speeds, in the range of 40,000–100,000 rpm, of a JetCat P80-SE type small turbojet engine with a single-stage radial compressor and an axial turbine on the same shaft. The hydrogen flow rate for each engine speed is changed in 10 l.min−1 increments up to 120 l.min−1, and the euro diesel fuel energy is substituted with hydrogen, resulting in different hydrogen energy fractions (HEFs). The results of the paper show that the maximum reduction in SEC is 9.6% with 40% HEF at 40,000 rpm. In addition, with 15% HEF provided for each engine speed: while the reduction in specific energy consumption (SEC) at 40,000 rpm is 6.5%, at 100,000 rpm the reduction in SEC is 1.2%; the decrease in CO emissions at 40,000 rpm is 33%, while at 100,000 rpm the decrease in CO is 54%; in the range of 40,000–100,000 rpm, the decrease in CO2 emissions changes the range of 16–18%; while the increase in HC emission is 10% at 70,000 rpm, it increases up to 50% at 100,000 rpm; the increase in NOx emissions appearing after 80,000 rpm, is only around 1 ppm; and despite the increase in HC and NOx emissions by the increase of HEFs, the decrease in CO2 and CO emissions leds to a remarkable improvement in environmental-economic indicators.

Investigation of Performance and Emission Parameters of Hydroxygen (HHO)-Enriched Diesel Fuel with Water Injection in the Compression Ignition Engine

The development of engine technologies and research on combustion processes are focused on finding new generation CI engines with simple control of the combustion process while efficiently maintaining desirable engine performance and meeting emission regulations. This comprehensive study on the relatively low hydrogen energy fraction (0.65–1.80%), supplied by onboard water electrolysers and on water injection, was performed on the performance and emission parameters of the CI engine. The article presents results of both experiment and simulation about the effect of hydroxygen and water injection on the combustion process, auto-ignition delay, combustion intensity, the temperature of the mixture and engine performance at BMEP of 0.2 MPa, 0.4 MPa, 0.6 MPa, and 0.8 MPa at a speed of 1900 rpm. For the first part, the test engine operated with diesel fuel with 3.5 L/min of hydroxygen gas supplied with an external mixture formation. The HHO has an effect on the combustion process at all range of BMEP. A decrease in BTE and increase in BSFC were noticed during tests. The peak pressure and the rate of heat release decreased, but the NOx decreased as well. The second part of experiment was performed with the injection of a substantial amount of water, 8.4–17.4 kg/h (140–290 cm3/min), and the same amount of hydroxygen. The injection of water further decreased the NOx; therefore, HHO and WI can be used to meet emission regulations. A simulation of the combustion process was carried out with the AVL BOOST sub-program BURN. The AVL BOOST simulation provided a detailed view of the in-cylinder pressure, pressure-rise, combustion intensity shape parameter and SOC.

An investigation of euro diesel-hydrogen dual-fuel combustion at different speeds in a small turbojet engine

PurposeThis study seeks the effect on static thrust, thrust specific energy consumption (TSEC) and exhaust emissions of euro diesel-hydrogen dual-fuel combustion in a small turbojet engine.Design/methodology/approachExperimental studies are performed in a JetCat P80-SE type small turbojet engine. Euro diesel and hydrogen is fed through two different inlets in a common rail distributing fuel to the nozzles. Euro diesel fuel is fed by a liquid fuel pump to the engine, while hydrogen is fed by a fuel-line with a pressure of 5 bars from a gas cylinder with a pressure of approximately 200 bars.FindingsAt different engine speeds, it is found that there is a decrease at the TSEC between a range of 1% and 4.8% by different hydrogen energy fractions (HEF).Research limitations/implicationsThe amount of hydrogen is adjusted corresponding to a range of 0–20% of the total heat energy of the euro diesel and hydrogen fuels. The small turbojet engine is operated between a range of 35,000 and 95,000 rpm engine speeds.Practical implicationsOn the other hand, remarkable improvements in exhaust emissions (i.e. CO, CO2, HC and NOx) are observed with HEFs.Originality/valueThis is through providing improvements in performance and exhaust emissions using hydrogen as an alternative to conventional jet fuel in gas turbine engines.

Improving burning speed by using hydrogen enrichment and turbulent jet ignition system in a rotary engine

Low flame speed restrains engine efficiency and increases HC emissions in rotary engines. Hydrogen addition and turbulent jet ignition have a great potential in increasing engine performance as they increase fuel burning speed. In this study, the classical R13b-Renesis Wankel engine and a modified one with a turbulent jet ignition configuration are numerically investigated by using hydrogen as a supplement. Eccentric motion of the rotor was generated by using User Defined Function in ANSYS-Fluent software. Pure methane and methane blended with 3% and 6% hydrogen energy fractions were used as fuels in the calculations. Combustion was modeled by using reduced mechanism of hydrogen-methane combustion having 22 species and 104 reactions. The Wankel engine was simulated at 2000 rpm speed and partial load conditions. At first, classical engine configuration having two spark plugs was simulated with pure methane. Then, hydrogen blended methane simulations were conducted to investigate the benefits of the hydrogen addition. Similar procedure was applied for the turbulent jet ignition application. The results show that both approaches are effective on increasing the burning speed of the fuel. It is revealed that hydrogen addition increases the indicated mean effective pressure (IMEP) by 1.8% and 5.2% for 3% and 6% hydrogen fraction cases respectively in the classical engine. Turbulent jet ignition with pure methane increases IMEP by 4.7% compared to the classical engine. Hydrogen addition only in pre-chamber is effective as much as 6% hydrogen fraction of classical engine. As the burning speed is increased by the application of these methods, CO and HC emissions are reduced and NO emission is increased. It is concluded that benefits of hydrogen addition and turbulent jet ignition applications can be optimized for both reducing harmful emissions and increasing engine performance.

Effects of hydrogen addition on combustion, thermodynamics and emission performance of high compression ratio liquid methane gas engine

It is a potential approach to improve the fuel efficiency that the liquid methane gas (LMG) purified from liquefied natural gas (LNG) is fueled with the high compression ratio (CR) engine, while the actual effect is restricted by the lowcombustion velocity of methane. To solve this problem and further improve the LMG engine performance, the approach of hydrogen addition to LMG engine was investigated by combining experiment with numerical simulation. Based on experimental data, the computational fluid dynamics (CFD) model coupled with reduced chemical kinetic mechanism was built and calibrated, which was then employed to study the effects of different hydrogen energy fraction (HEF) on combustion, thermodynamic and emission of LMG engine. The results show that, the peak of heat release rate (HRR) increases sharply with the HEF rising and leads the maximum in-cylinder pressure to increase. The indicated thermal efficiency of LMG engine first increases and then decreases, and the maximum falls in the HEF range between 8% and 12%. Although the combustion velocity of mixture gas is obviously increased by hydrogen addition, the detonation trend still becomes larger and it increases by 10 times as HEF changes from 12% to 20%. As the HEF increases from 0 to 20%, NOx emission increases continuously, while CO and CH4 emissions decrease due to the higher combustion temperature. All these provided direction for improving LMG engine performance, and offered theoretical basis for selecting technology routes to meet emission regulations.