Hydrogen Direct Injection Research Articles

Study on effects of split injection proportion on hydrogen mixture distribution, combustion and emissions of a gasoline/hydrogen SI engine with split hydrogen direct injection under lean burn condition

Split hydrogen direct injection is proved to be a better way to use the hydrogen in the engine. Therefore, a numerical study on effects of split injection proportion on hydrogen mixture distribution, combustion and emissions was presented of a gasoline/hydrogen SI engine with split hydrogen direct injection to investigate the principle of split hydrogen direct injection. Under lean burn condition, six different split injection proportions achieve six kinds of hydrogen mixture distribution, which affect the engine performance a lot. With split hydrogen direct injection, the mixture nearby the spark plug is denser and in other zone is more homogeneous at the same time, which achieve better performances of both efficiency and emissions. As the first injection proportion increases, the cylinder pressure climbs to the highest with first injection proportion of 33% and the NOX, CO and HC emissions decrease continually. When the first injection proportion is 75%, the NOX, CO and HC emissions are respectively 31.6%, 79.3% and 40.6% less than those of single hydrogen direct injection.

Effects of Hydrogen Addition Ratios on Cycle-by-Cycle Variations of a Duel-Fuel Spark Ignition Engine with Ethanol Intake Port Injection and Hydrogen Direct Injection under Various Excess Air Ratios

In order to improve the combustion stability of ethanol engine under lean-burn condition, the experiment was carried out on a spark ignition engine with ethanol intake port injection and hydrogen d...

Combustion characteristics of direct injection hydrogen in noble gases atmosphere

Hydrogen combustion in the internal combustion engine (ICE) has currently taken part in the transportation industry due to its environmentally friendly and high engine thermal efficiency. Hydrogen direct injection introduction in the internal combustion engine eliminates the harmful emission from carbon and improves engine stability. The substitution from nitrogen to noble gases for the intake will solve the high auto-ignition temperature of hydrogen in compression ignition (CI) engine problem. This paper intended to study the combustion characteristics of direct injection hydrogen in oxygen-noble gas atmosphere such as argon and helium to find the suitable engine and injection parameters for the optimum engine efficiency. The simulation conducted using Converge CFD V2.4 software based on Yanmar NF19K direct injection CI engine. The simulation was done for different oxygen-noble gases such as argon, neon, and helium, while the injection timing and ambient temperature were modified to optimize the hydrogen combustion characteristics. The study found that noble gases help to increase the in-cylinder temperature and ignite the hydrogen. The study also found that early injection timing results in the highest in-cylinder pressure. Besides, increasing ambient temperature for intake decreases the in-cylinder pressure and lengthen the ignition delay. Therefore, the most suitable injection parameter for the most optimum hydrogen combustion characteristics is 380 K ambient temperature, early injection timing at -10°CA, and higher injection pressure. Helium produced higher in-cylinder peak pressure compared to argon due to its high specific heat ratio. Hence, further consideration of helium and good injection strategies should be applied for better engine thermal efficiency.

筒内直接噴射水素エンジンの水素噴流と噴射時期の最適化による高熱効率・低NOx ニアゼロエミッションの実現と一層の性能向上に関する研究

筒内直接噴射水素エンジンの水素噴流と噴射時期の最適化による高熱効率・低NOx ニアゼロエミッションの実現と一層の性能向上に関する研究

Effects of direct-injected hydrogen addition on methane combustion performance in an optical SI engine with high compression-ratio

Natural gas is one of the most potential alternative fuel of clean combustion and anti-knocking property. However, slow-burning rate and obvious cyclic variations have become the major concerns for modern gas engines. Based on a high compression-ratio, optically accessible, single-cylinder spark-ignition engine, fundamental experiments were conducted to investigate the role of direct-injected hydrogen under from stoichiometric to lean combustion conditions. Synchronization measurement of in-cylinder pressure and optical flame imaging was conducted to analyze cycle-to-cycle variations, indicated thermal efficiency, and flame evolution. The results show that as the addition of direct-injected hydrogen, the cycle-to-cycle variations decrease and indicated thermal efficiency increases, with advanced combustion phase and shortened combustion duration. The combustion imaging indicates that the significant positive influence is from the direct-injected hydrogen, which promotes initial flame kernel formation and early flame propagation. Further, an empirical criterion for mass fraction burned combined with optical data was adopted for quantification and analysis of early flame evolution. It shows that the addition of direct-injected hydrogen mainly promotes the early-stage flame propagation, manifesting increased the burning rate and thermal efficiency. The results shall give useful information in the application of direct-injected hydrogen to improve natural gas engine performance while increasing flame speed and controlling cyclic variations.

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 NOX emissions with hydrogen addition increase by an average of 115%. For different hydrogen direct injection timings, the NOX emissions of 120°CA BTDC is the highest, which is 29.9% higher than the 75°CA BTDC. The hydrogen addition make the NOX 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 NOX 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.

A Review of Hydrogen Direct Injection for Internal Combustion Engines: Towards Carbon-Free Combustion

A paradigm shift towards the utilization of carbon-neutral and low emission fuels is necessary in the internal combustion engine industry to fulfil the carbon emission goals and future legislation requirements in many countries. Hydrogen as an energy carrier and main fuel is a promising option due to its carbon-free content, wide flammability limits and fast flame speeds. For spark-ignited internal combustion engines, utilizing hydrogen direct injection has been proven to achieve high engine power output and efficiency with low emissions. This review provides an overview of the current development and understanding of hydrogen use in internal combustion engines that are usually spark ignited, under various engine operation modes and strategies. This paper then proceeds to outline the gaps in current knowledge, along with better potential strategies and technologies that could be adopted for hydrogen direct injection in the context of compression-ignition engine applications—topics that have not yet been extensively explored to date with hydrogen but have shown advantages with compressed natural gas.

Numerical research on effect of hydrogen blending fractions on idling performance of an n-butanol ignition engine with hydrogen direct injection

In this paper, a numerical research on an n-butanol ignition engine with hydrogen direct injection was carried out, aiming to observe the effect of hydrogen blending fractions on idling performance. A three-dimensional dynamic mesh model coupled with a detailed chemical kinetic mechanism of n-butanol oxidation were established to investigate the engine combustion process in CFD software CONVERGE. And the numerical model was validated through experiments. The performance of pressure and temperature inside cylinder, HC and CO emissions and formaldehyde and acetaldehyde emissions with four hydrogen fractions were simulated and analyzed. The simulation results showed that in comparison with pure n-butanol, the peak cylinder pressure increased 18.62%, 22.86% and 25.41% at φH2 = 5%, φH2 = 10% and φH2 = 15%, respectively. Meanwhile, the process of heat release can be accelerated and concentrated by hydrogen blending. The HC and CO emissions decreased gradually with the increase of hydrogen fraction. The largest magnitude of reduced HC and CO emissions was at φH2 = 5% as 31.31% and 19.05%, respectively. In terms of unregulated emissions, the acetaldehyde emissions remained a higher level than formaldehyde emissions for all hydrogen fractions at idle condition, and both decreased with the increase of hydrogen fraction. The distribution of formaldehyde and acetaldehyde concentration were closely related to the temperature field inside cylinder. The improvement of acetaldehyde emissions affected by adding hydrogen was more significant than that of formaldehyde emissions. Through hydrogen direct injection, a local hydrogen-enriched area near the spark plug can be formed, which contributed to better combustion performance of n-butanol engine at idle condition.

Effects study of injection strategies on hydrogen-air formation and performance of hydrogen direct injection internal combustion engine

Based on the dual challenges of the global energy crisis and environmental pollution, hydrogen has been recognized as an ideal alternative internal combustion engine (ICE) fuel. To improve the combustion efficiency of hydrogen direct injection ICE, we numerically analyzed the effects of different injection parameters, including injection timing, injection pressure, and dual injection, on the formation of a hydrogen-air mixture using the CONVERGE software from the perspective of mass transfer and flow state. It was determined that it is enough to set the injection timing to −88° after top dead center (ATDC) for both uniform mixture and desirable indicated thermal efficiency (ITE). However, when the injection timing is set to −43° ATDC, an acceptable ITE and effective combustion can be achieved by employing the “jet-room coordination” effect of the ω chamber. Injection pressure has a minimal effect on mixture formation and combustion. In contrast, the timing and mass fraction of secondary injection have a significant influence on tumble strength, which is a key factor for the mixture improvement.

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions of a gasoline/hydrogen SI engine

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions was presented for a gasoline/hydrogen SI engine. Three kinds of injection modes (gasoline, gasoline plus homogeneous hydrogen and gasoline plus stratified hydrogen) and five excess air ratios were applied at low speed and low load on a dual fuel SI engine with hydrogen direct injection (HDI) and gasoline port injection. The results showed that, with the increase of excess air ratio, the brake thermal efficiency increases firstly then decreases and reaches the highest when the excess air ratio is 1.1. In comparison with pure gasoline, hydrogen addition can make the ignition stable and speed up combustion rate to improve the brake thermal efficiency especially under lean burn condition. Furthermore, it can reduce the CO and HC emissions because of more complete combustion, but produce more NOX emissions due to the higher combustion temperature. Since, in the gasoline plus stratified hydrogen mode, the hydrogen concentration near the sparking plug is denser than that of homogeneous hydrogen, the ignition is more stable and faster, which further speed up the combustion rate and improve the brake thermal efficiency. In the gasoline plus stratified hydrogen mode, the brake thermal efficiency increases by 0.55%, the flame development duration decreases by 1.0°CA, rapid combustion duration decreases by 1.3°CA and the coefficient of variation (COV) decreases by 9.8% on average than that of homogeneous hydrogen. However, in the gasoline plus stratified hydrogen mode, due to the denser hydrogen concentration near the sparking plug and leaner hydrogen concentration near the wall, the combustion temperature and the wall quenching distance increase, which make the NOX and HC emissions increase by 14.3% and 12.8% on average than that of homogeneous hydrogen.

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.

Investigation of a new concept of hydrogen supply for a spark-ignition engine

The article presents the results of conceptual and research works of an internal combustion engine adapted for hydrogen supply. The engine was equipped with a direct injection of hydrogen into the combustion chamber, allowing the control of the heat release rate. The developed concept of the power supply system and the fuel injection strategy were presented. Initial results of bench tests were also presented.

Combined influence of hydrogen direct-injection pressure and nozzle diameter on lean combustion in a spark-ignited rotary engine

A three-dimensional simulation on flow behavior and lean combustion in a hydrogen direct-injection gasoline rotary engine was implemented. The combined influence of hydrogen injection pressure (HIP) and nozzle diameter (HND) was numerically analyzed in the critical injection state. Results showed that with the increments of HIP and HND, further penetration and larger dispersion angle of jet-flow were presented. Increasing HIP led to larger jet-flow area and more jet-wall interaction, as well as greater deflection degree of hydrogen-flow after crashing upon the rotor surface. High-speed region expanded, while more jet-wall impingement occurred with the increment of HND. The spark ignited earlier and flame propagated faster as the HND modified smaller. As the HIP increased, the flame speed decreased slightly. The difference in the local Φ distribution and in-cylinder velocity field were the intrinsic mechanism of the HND impact, and the variation in the mixture concentration and TKE magnitude were the root causes of the HIP effect. The pressure and HRR traces were shifted to the downward clearly, while the peak positions were forming later as the HND extended larger. No perceptible difference in the peak positions of pressure and HRR were obtained with the HIP decrease, although pressure tended to increase along with heat release retard to be shortened. The combustion rate decreased with increments of HND and HIP, the timings of the initial consumption were delayed, and a proportional correspondence of reactants and intermediates was witnessed. The reduced NOx formation was obtained by increments of HND and HIP, and an inverse correlation can be seen between soot, CO, HC generations and NOx concentration. The scheme of 0.4 MPa HIP and 1 mm HND was the optimum configuration. Compared with a larger HND and higher HIP configuration, the peak pressure and maximum HRR were increased by 24.1% and 40.5%, and the productions of soot, CO, and HC were reduced by 55.7%, 61.5%, and 54.7%, respectively, though the NOx generation was increased to some extent. It was recommended in practice operations that the combination of lower HIP and smaller HND left a positive influence on improving the combustion characteristics of Wankel engines.

Study on Emission Characteristics of Hydrogen Direct-Injection Gasoline Engine

Experiments have been carried out on a hydrogen direct-injection and gasoline port-injection engine at the conditions of locally rich hydrogen and lean-burn mode in order to study the effect of hydrogen fraction and air-fuel ratio on the engine’s emissions. The experiments results demonstrated that when the excess-air ratio was increased from 1 to 1.8, NOx and CO emissions were at least decreased by 91% and 95% respectively and HC emission was increased by 56%. Almost 23% reduction was observed in HC emission when hydrogen fraction changed from 3.9% to 10.5%, whereas the NOx emission has almost been tripled and CO emission is found to be less affected with hydrogen fraction.

Experimental study on lean-burn characteristics of an SI engine with hydrogen/gasoline combined injection and EGR

Hydrogen has shown potential for improving the combustion and emission characteristics of the spark ignition (SI) dual-fuel engine. To reduce the additional NOx emissions caused by hydrogen direct injection, in this research, the cooperative control of the addition of hydrogen with exhaust gas recirculation (EGR) in the hydrogen/gasoline combined injection engine was investigated. The results indicate that both the addition of hydrogen and the use of EGR can increase the brake mean effective pressure (BMEP). As the αH2 value increases from 0% to 25%, the maximum BMEP increases by 9%, 12.70%, 16.50%, 11.30%, and 8.20%, respectively, compared with the value without EGR at λ = 1.2. The CA0-10 tends to increase with increases in the EGR rate. However, the effect of EGR in increasing the CA0-10 can be offset by the addition of 15% hydrogen at λ = 1.2. Measurements of the coefficient of variation of the indicated mean effective pressure (COVIMEP) indicate that the addition of hydrogen can effectively extend the EGR limit. Regarding gaseous emissions, NOx emissions, after the introduction of EGR and the addition of hydrogen, are lower than those of pure gasoline without EGR. An 18% EGR rate yields a significant reduction in NOx, reaching maximum decreases of about 82.7%, 77.8%, and 60% compared to values without EGR at λ = 1.0, 1.2, and 1.4, respectively. As the EGR rate increases, the hydrocarbon (HC) emissions continuously increase, whereas a blend of 5% hydrogen can significantly reduce the HC emissions at high EGR rates at λ = 1.4. Finally, according to combustion and emissions, the coupling of a 25% addition of hydrogen with 30% EGR at λ = 1.2, and the coupling of a 20% addition of hydrogen with an 18% EGR rate at λ = 1.4 yield the best results.

Effects of split injection proportion and the second injection timings on the combustion and emissions of a dual fuel SI engine with split hydrogen direct injection

In this paper, a new kind of injection mode, split hydrogen direct injection, was presented for a dual fuel SI engine. Six different first injection proportions (IP1) and five different second injection timings were applied at the condition of excess air ratio of 1, first injection timing of 300°CA BTDC, low speed, low load conditions and the Minimum spark advance for Best Torque (MBT) on a dual fuel SI engine with hydrogen direct injection (HDI) plus port fuel injection (PFI). The result showed that, split hydrogen direct injection can achieve a higher brake thermal efficiency and lower emissions compared with single HDI. In comparison with single HDI, the split hydrogen direct injection can form a controlled stratified condition of hydrogen which could make the combustion more complete and faster. By adding an early spray to form a more homogeneous mixture, the split hydrogen direct injection not only can help to form a flame kernel to make the combustion stable, but also can speed up the combustion rate through the whole combustion process, which can improve the brake thermal efficiency. By split hydrogen direct injection, the torque reaches the highest when the first injection proportion is 33%, which improves by 1.13% on average than that of single HDI. With the delay of second injection timing, the torque increases first and then decreases. With the increase of first injection proportion, the best second injection timing is advanced. Furthermore, by forming a more homogeneous mixture, the split hydrogen direct injection can reduce the quenching distance to reduce the HC emission and reduce the maximum temperature to reduce the NOX. The split hydrogen direct injection can reduce the HC emission by 35.8%, the NOX emissions by 7.3% than that of single HDI.

Effects of hydrogen direct-injection angle and charge concentration on gasoline-hydrogen blending lean combustion in a Wankel engine

To analyze the effects of hydrogen charge concentration (HCC) and injection angle (IA) on the lean combustion in a gasoline Wankel engine, the present work implemented a numerical simulation model coupling with the kinetic mechanisms and validated with the experimental data. Results found that with the increase in HCC, the penetration of hydrogen injection is enlarged and the area of the high-speed jet flow is expanded. The jet-flow area for IAs of 45° or 135° is larger than that of 90°. Changing IA could obtain the hydrogen distribution at different regions of the rotor chamber and IA of 90° acquires the smallest hydrogen-rich region. Increasing IA brings about the reduced flame speed substantially; the flame area for IAs of 45° and 90° expands with the increment of HCC whereas the contrary pattern is witnessed at the IA of 135°. Smaller IA leads to the major burning occurring untimely, which resulting in less work delivery of the engine. The hydrogen consumption for IAs of 45° and 90° increases as HCC is ascendant while that for IA of 135° is just the reverse. Variations in the mixture distribution and turbulence are the intrinsic mechanism of how the HCC and IA reflects the combustion progress. As hydrogen is injected with larger HCC and smaller IA, a relatively richer mixture and higher turbulent kinetic energy are distributed close in the spark ignition region. The peak combustion pressure reduces and its corresponding crank position delays with the widened IA at any HCC. Considering the fuel combustion and nitric oxide formation, as hydrogen volume fraction is 3% and IA is 45°, the engine could realize the optimized performance under the computational condition. An efficient combustion performance may be performed in engineering application if the hydrogen IA is in accordance with the rotor rotating direction at lower HCC.

Near-zero emissions with high thermal efficiency realized by optimizing jet plume location relative to combustion chamber wall, jet geometry and injection timing in a direct-injection hydrogen engine

Thermal efficiency was substantially improved and NOx emissions were reduced to a level at a single-digit ppm with PCC combustion by optimizing such characteristics as the direction, number and diameter of the injected jet and controlling the injection timing and also by combining with combustion of lean mixture. Output power declined by lean mixture was recovered by supercharging in keeping NOx emissions remained at the same level, while thermal efficiency was improved furthermore by slightly re-optimizing jet conditions. As a result, hydrogen engine which does not emit any CO2 and particulate matter in principle is worth to be called near-zero emission engines in both name and reality.

Effects of Air-fuel Ratio and Hydrogen Fraction on Combustion Characteristics of Hydrogen Direct-Injection Gasoline Engine

Effects of air-fuel ratio and hydrogen fraction on engine combustion at the conditions of locally rich hydrogen and lean-burn mode have been experimentally carried out on a hydrogen direct-injection (HDI) and gasoline port-injection engine. The test results showed that both excess-air ratio and hydrogen affect the HDI combustion. The peak cylinder pressure was decreased by 45% (3.9% hydrogen fraction) and 23% (10.5% hydrogen fraction) when the excess-air ratio was increased from 1 to 1.5. Hydrogen, which compensates the loss of cylinder pressure and heat release rate caused by lean burn, effectively improves the engine performance at lean burn operation. In addition, when the excess air ratio was set at 1.2, the rise in hydrogen fraction from 3.9% to 10.5% caused a 51.2 % increase in peak cylinder pressure and 101% increase in maximum heat release rate. The maximum cylinder temperature and exhaust temperature was increased firstly and then decreased afterwards with an increase in excess-air ratio. The increase in hydrogen fraction resulted in the acceleration of maximum cylinder temperature, but the exhaust temperature is not that much affected.

Numerical Study on Combustion and Emission Characteristics of a PFI Gasoline Engine with Hydrogen Direct-Injection

Abstract In this paper, the effects of hydrogen blending radio and EGR rate on combustion and emission characteristics of a PFI gasoline engine with hydrogen direct-injection have been investigated by numerical modeling methods using a new generation of CFD simulation software CONVERGE. Results showed that compared with original engine, hydrogen direct-injection PFI gasoline engine had a better performance on combustion characteristics, but it also had a disadvantage of increasing NOx emissions. With the increase of hydrogen blending radio, combustion duration shortened and CA50 advanced and was closer to TDC. And CO and THC emissions decreased, however NOx emission increased. The variations of the combustion and emission characteristics followed by the increase of the EGR rate were exactly the opposite to the change of hydrogen blending radio. Considering both the combustion and emission characteristics, using moderate EGR rate (15%~20%) under high hydrogen blending radio (15%~20%) condition can realize the simultaneous improvement of combustion and emission performance.