Hydrogen Direct Injection Research Articles

Synergic effect of hydrogen and n-butanol on combustion and emission characteristics of a hydrogen direct injection SI engine fueled with n-butanol/gasoline

Hydrogen, an ideal carbon-free energy carrier with favorable combustion properties, has drawn worldwide attention as a high-expectation way to enhance fossil fuels’ combustion performance. However, currently, limited investigations are about enhancing n-butanol hybrid gasoline engines through hydrogen addition. Thus, in this paper, the hydrogen direct injection (HDI) was put forward to improve an SI engine fueled with n-butanol/gasoline, and the synergic effect of hydrogen and n-butanol on combustion and emission characteristics was studied. Experimental results indicated the favorable influence of a low n-butanol mixing ratio (νN, νN = 25%) on enhancing combustion can relatively weaken the similar promoting effect of hydrogen. And the sequential increase in hydrogen addition ratio (φH, φH = 15–20%) can compensate for the negative impact of unfavorable atomization and vaporization quality caused by higher n-butanol blending (νN = 75–100%), namely the usage amount of n-butanol in engine can be raised. Further, compared with pure gasoline, the percentage change in BMEP (brake mean effective pressure) at νN = 25% and 100% can be increased from 1.79% to 5.04% and −5.38%–2.01% respectively by φH from 0 to 20%. Besides, the HDI can also shorten the combustion duration, accelerate the heat release process and improve the combustion stability of each νN, while the amplitude of promotion exhibits a relative downtrend with the increase of φH. As for emission characteristics, the HC, CO and particulate emissions decreased monotonously with the increasing φH under all νN, but there was a visible increase in NOX emissions.

수치해석을 통한 수소 직분사 엔진의 분무각도에 따른 실린더 내 혼합도 및 연소 특성 예측

수치해석을 통한 수소 직분사 엔진의 분무각도에 따른 실린더 내 혼합도 및 연소 특성 예측

Progressive strategies to avoid and exploit knock limit for optimal performance and stoichiometric operation of a DI hydrogen engine with high CR at WOT conditions

Knock is one of the crucial challenges facing direct injection (DI) hydrogen engines. In this study, the rational optimization of operating parameters and the proposal of two progressive knock suppression strategies enable the DI hydrogen engine to achieve knock-free operation at wide-open throttle (WOT) and stoichiometric conditions, which may better control the test system’s complexity. The present work uses 0.5 bar knock intensity (KI) as the threshold for occurring knock. The test consists of three parts. In Part 1, KI exceeds 0.5 bar at 1.7 λ. Then, considering the suppression effect of the stratified mixture on knock, a strategy for cooperative control of λ and start of injection (SOI) is proposed in Part 2, which can lower λ to 1.4 within the allowable borderline knocking. However, this strategy fails at 70°CA BTDC SOI. Based on the above results, a strategy to synergistically adjust λ and intake variable valve timing is adopted in Part 3, which suppresses knock mainly by varying the airflow exchange process and effective compression ratio. Finally, the strategies presented in Part 2 and Part 3 allow the engine to control the KI to less than 0.5 bar at WOT and stoichiometric conditions, which ensures power performance.

Numerical modelling of a heavy-duty diesel-hydrogen dual-fuel engine with late high pressure hydrogen direct injection and diesel pilot

Direct gaseous fuel injection in internal combustion engines is a potential strategy for improving in-cylinder combustion processes and performance while reducing emissions and increasing hydrogen energy share (HES). Through use of numerical modelling, the current study explores combustion in a compression ignition engine utilising a late compression/early power stroke direct gaseous hydrogen injection ignited by a diesel pilot at up to 99% HES. The combustion process of hydrogen in this type of engine is mapped out and compared to that of the same engine using methane direct injection. Four distinct phases of combustion are found which differ from that of pure diesel operation. Interaction of the injected gas jet with the chamber walls is found to have a considerable impact on performance and emission characteristics and is a factor which needs to be explored in greater detail in future studies. Considerable performance increase and carbon-based emission reductions are identified at up to 99% HES at high load but low load performance greatly deteriorated when 95% HES was exceeded due to a much reduced diesel pilot struggling to ignite the main hydrogen injection.

Experimental and modeling investigations to improve the performance of the near-zero NOx emissions direct-injection hydrogen engine by injection optimization

High NOx emissions present a significant constraint on the power and efficiency enhancement of direct-injection hydrogen engines. To address this issue, a 2.0 L turbocharged direct-injection hydrogen engine is optimized to achieve near-zero NOx emissions and high engine performance through injection optimization. Both experimental and simulation results indicate that early injection of supersonic hydrogen increases the turbulence energy, while late injection leads to the clustering of rich mixing gases, resulting in elevated combustion temperature and increased NOx emissions. The NOx emissions can keep near-zero while the brake thermal efficiency improves from 40.4% to 41.7% with appropriate retarded injection timing. Therefore, an optimal injection timing exists, and the experiments revealed that adjusting the end timing of injection to 80°CA BTDC resulted in the approximately 1.5% increase in the brake thermal efficiency compared to other injection strategies with near-zero NOx emissions.

Combustion stability for early and late direct hydrogen injection in a dual fuel diesel engine

The paper presents an analysis of the experimental results of direct hydrogen injection in a dual-fuel diesel engine. The test object is a four-cylinder, four-stroke ADCR engine. An analysis of the following parameters was carried out: indicated mean effective pressure, peak pressure, angle of maximum pressure and released heat. Statistical analysis of the obtained results was carried out for each cylinder separately for four different hydrogen doses. Both early and late direct hydrogen injection were analyzed. The significance of the differences for each of the analyzed parameters and type of injection was determined. The stability of the combustion process was evaluated using the coefficient of variation CoV(IMEP).

A high-efficiency internal combustion engine using oxygen and hydrogen

The work proposes the design of a novel internal combustion engine developed to benefit from the availability on board of cryogenic pressurized hydrogen and oxygen to serve a mechanical propulsion system. The rationale behind the design, as well as the results of simulations, are presented. The two-stroke engine uses direct injection of hydrogen, oxygen, and water, and downstream power turbines, to deliver power densities above 220 kW/L, zero-emission of nitrous oxides and carbon dioxide, and efficiency above 0.70. The novel engine could be an alternative to fuel cell electric propulsion systems, delivering in addition to better hydrogen fuel efficiency, also reduced weight and space of the complete propulsion system.

Full oxygen blast furnace steelmaking: From direct hydrogen injection to methanized BFG injection

This paper presents a novel concept of Power to Gas in an oxygen blast furnace, through blast furnace gas methanation and direct H2 injection. The PEM electrolyser produces H2, which reacts with the CO and CO2 from the blast furnace gas forming synthetic natural gas. The latter gas is injected into the blast furnace, closing a carbon loop and avoiding CO2 emissions. A parametric analysis is performed to vary the H2:CO2 ratio in the methanation reaction. Different ratios are simulated and compared, among of which the most representative are: (i) 2.5, where unreacted CO2 is directly recycled with the synthetic natural gas; (ii) 4, where stoichiometric conditions are found and the synthetic gas is composed mostly by CH4; and (iii) 8, where an excess of H2 is found in the synthetic gas; and (iv) an infinite ratio, where only H2 is injected in the blast furnace. In the latter, the methanation plant is not required, and no synthetic natural gas is produced. The results show that low H2:CO2 ratios perform poorly, involving high PEM sizes and high costs but only a 5% of CO2 avoidance (compared to conventional blast furnaces). A H2:CO2 ratio of 4 and full H2 injection results in higher reduction of CO2 emissions (33.8 % and 28.6%) with carbon abatement costs of 260 and 245 €/tCO2, respectively.

Impact of hydrogen direct injection on engine combustion and emissions in a GDI engine

The combustion and emission characteristics of a hydrogen engine were investigated through experimental analysis using a GDI engine. To enable hydrogen in-cylinder direct injection, a specialized hydrogen gas injector was employed. A comparative analysis of the combustion performance between gasoline and hydrogen fuels in a spark-ignited engine was conducted. Additionally, the study experimentally explored the thermal efficiency and emission reduction potential of hydrogen engines in lean combustion modes. The results indicated a significant improvement in the combustion rate when hydrogen fuel was utilized in the spark-ignited engine. However, the effective thermal efficiency was found to be lower than that of gasoline fuel due to the delayed MBF50 under stoichiometric conditions. Furthermore, when compared to gasoline fuel, the reduction of CO and THC emissions was accompanied by an increase in NOx emissions. Nevertheless, optimizing the air dilution ratio in hydrogen engines led to an improvement in the effective thermal efficiency. Specifically, under medium load conditions, a Lambda value of 2.7 resulted in an effective thermal efficiency of 43.5%. Additionally, under ultra-lean conditions (Lambda > 2.3), NOx emissions could be reduced to below 50 ppm, reaching as low as 44 ppm. This study highlights the potential of improving combustion efficiency and reducing emissions by utilizing hydrogen fuel, particularly in lean combustion modes. It contributes to the continuous development of hydrogen engine technology and promotes the implementation of cleaner and more efficient energy solutions.

Gas-dynamic and mixing analysis of under-expanded hydrogen jets: effect of the cross section shape

Green hydrogen is expected to have a key role in the transition towards a carbon-neutral society, particularly in the transportation sector. Exploration of novel solutions for the direct injection of hydrogen in internal combustion engines (ICEs) is a main topic for both academia and industry. Here, the authors explore the gas-dynamic and mixing features of hydrogen under-expanded jets exiting from non-axisymmetric cross-sections, with the aim to provide guidelines for designing novel generations of ICE hydrogen injectors. Triangular and star shapes have been compared with elliptical and rectangular sections with different aspect ratios. Differences in the shock wave systems are reported, and explanations of the gas-dynamic mechanisms developed by each section are proposed. Non-uniformity in the radial expansion of the jet boundary has been noticed in all of the non-axisymmetric sections, leading to an axis switching of the jet in some cases. Differences in the radial mixing and axial jet penetration have been reported too, and a robust correlation with the vorticity distribution along the jet boundary has been observed.

Operating and Thermal Efficiency Boundary Expansion of Argon Power Cycle Hydrogen Engine

The efficiency enhancement of argon power cycle engines through theoretical means has been substantiated. However, the escalation of in-cylinder temperatures engenders abnormal combustion phenomena, impeding the augmentation of compression ratios and practical efficiency. This study presents a comprehensive investigation employing experimental and simulation techniques, aiming to extend the boundaries of thermal efficiency and operational capabilities for hydrogen-powered argon cycle engines. The impact of hydrogen direct injection, intake boost, and port water injection is evaluated in conjunction with an argon power cycle hydrogen engine. The hydrogen direct injection, particularly at an engine speed of 1000 rpm, significantly increases the indicated mean effective pressure from 0.39 MPa to 0.72 Mpa, surpassing the performance of the port hydrogen injection. Manipulating the hydrogen direct injection timing results in the formation of a stratified mixture, effectively attenuating the combustion rate, and resolving the issue of excessively rapid hydrogen combustion within an Ar/O2 environment. The implementation of super lean combustion, combined with intake-boosting, achieves a maximum gross indicated thermal efficiency of 57.89%. Furthermore, the port water injection proves to be an effective measure against knock, broadening the operational range of intake-boosted conditions. Notably, the maximum gross indicated thermal efficiency recorded for the port water injection group under intake-boosted conditions reaches 59.35%.

Combustion characteristics of a turbocharged direct-injection hydrogen engine

The direct injection hydrogen internal combustion engines avoid backfires and have a higher power density, especially when coupled with a turbocharger. However, while previous researches have focused on specific aspects of direct injection hydrogen internal combustion engines, their whole combustion characteristics remain largely unclear. Therefore, this study aims to comprehensively investigate the combustion characteristics of turbocharged direct injection hydrogen internal combustion engines across the entire operating map in order to optimize their performance. The combustion characteristics are hypothesized to be significantly influenced by operating parameters, including the equivalence ratio, spark timing, start of injection, and other relevant factors. To achieve this, the experiments were conducted on a 2.0 L turbocharged direct injection hydrogen internal combustion engine, covering a wide range of operating conditions. Specifically, the engine speeds varied from 1000 to 4000 rpm, loads ranged from 3.7 to 10.6 bar, equivalence ratios spanned from 0.33 to 0.71, spark timing was adjusted within a range of 21 degrees of crank angle, and start of injection varied within a range of 80 degrees of crank angle. The experimental results reveal notable findings regarding the turbocharged direct injection hydrogen internal combustion engine. For instance, the maximum pressure rise rate of the turbocharged direct injection hydrogen internal combustion engine (3.85 bar/°CA at 1500 rpm) at various engine speeds at wide open throttle are greater than those of a turbocharged port fuel injection hydrogen internal combustion engine and a gasoline engine. Furthermore, variations in equivalence ratio and spark timing cause significant increases in pressure rise rate by 328.4% and 233.3%, respectively. The peak pressure rise rate characteristics provide valuable insights for optimizing the noise, vibration and harshness of turbocharged direct injection hydrogen internal combustion engines. Additionally, the burning duration demonstrates an initial increase and subsequent decrease with changes in the start of injection, aiding in the determination of the optimal start of injection for achieving high brake thermal efficiency. Overall, this research provides valuable insights into the macroscopic combustion characteristics of a turbocharged direct injection hydrogen internal combustion engine across different operating conditions. These findings not only can be directly applied to hydrogen internal combustion engines of the same displacement and type, but also can be applied to the design and development of hydrogen internal combustion engines with different displacements and types.

An experimental study of a strategy to improve the combustion process of a hydrogen-blended ammonia engine under lean and WOT conditions

Ammonia and hydrogen are two carbon-free alternative fuels for engines. Considering that there are few studies on improving an ammonia-hydrogen engine's lean combustion performance, this investigation based on an engine with the Miller cycle employs hydrogen direct injection (HDI) and NH3 port injection and then proposes an adjustment strategy to vary the start of injection (SOI) of HDI for affecting the engine combustion process. When ammonia volume share (AVS) is greater than 50%, the engine shows poor performance. Nevertheless, the stratification effect of hydrogen jets may be used to elevate the hydrogen concentration around spark plug by properly delaying SOI and then creating the locally rich mixture with a high hydrogen share, which prominently promotes the flame kernel formation, shortens CA0-90, reduces CoVPmax, and enables the engine to reach approximately 36% BTE. It is notable that very late SOI can slightly deteriorate the heat release process and lower engine performance.

A comprehensive study for the identification of the requirements for an optimal H2 combustion engine

As part of the fight against global warming and to achieve greenhouse gas emission targets, it is crucial to reduce the carbon footprint of ground transportation. Mobility needs are continuously growing with increase in population. All these factors will lead to an upsurge in the energy demand for the mobility in the very next future. Consequently, the diversification of low carbon energy sources is urgently required. Hydrogen can be used for mobility solution in its two energy conversion mechanisms: The Fuel Cell technology or the Internal Combustion Engine (ICE). The latter option, studied in the present work, offers the advantages of current fossil fuel engines – existing and proven technology, lifetime, controlled cost – with a very low carbon footprint. The overall objective of the study is to define the specifications of a dedicated Hydrogen direct injection combustion system for ground transportation application with the best fuel efficiency and lower raw emissions, to minimize the aftertreatment needs. A complete experimental and numerical study was carried out to get valuable information on various phenomena occurring throughout the engine cycle. The very first step of the study consisted in performing experimental investigations. For this purpose, an all metal single cylinder engine originally designed for gasoline spark ignited combustion (tumble air motion, gasoline direct injection) was modified for hydrogen direct injection combustion. The gas-gas injection was experimentally studied in the High Pressure/High Temperature vessel available at IFPEN. Those experiments were used to calibrate the 3D CFD numerical approach. Based on a 0D pre-study (boundary conditions) and using the injection modeling calibration introduced before, 3D CFD simulations have been then carried out with specific hydrogen kinetics properties. Finally, this comprehensive study highlights the specificities of ICE running with hydrogen. It provides indications and guidelines for further developments and optimization of hydrogen combustion engines.

Energy and exergy analysis for a turbocharged direct-injection hydrogen engine to achieve efficient and high-economy performances

Hydrogen is a potential alternative fuel for combustion engines with its higher renewability, near zero emission, and excellent combustion performance. The direct-injection (DI) engine provides favorable brake thermal efficiency (BTE), less dependence on the hydrogen purity but sacrificing the production cost. This study explores both effects of turbocharging and DI on the energy and exergy balances, as well as the cost-effective analysis on a spark ignition engine. Results reveal the exergy efficiencies are related to the engine speeds and loads, while its maximum is 58.8% with 3500 rpm and 1.4 MPa of brake mean effective pressure. The DI system increases 2.6% maximum BTE from the port fuel injection. However, the exhaust energy proportions exceed 32.8% and 18.9% at the maximum power and BTE. An organic Rankine cycle is utilized to improve the exergy to the maximum of 58.9%. The valuable experience can be widely applied for hydrogen engine design.

An experimental study of various load control strategies for an ammonia/hydrogen dual-fuel engine with the Miller cycle

Hydrogen and ammonia, as two renewable carbon-free combustibles, are considered to be potentially excellent alternative fuels for internal combustion engines. Since hydrogen and ammonia have opposite and complementary combustion characteristics, the co-combustion of ammonia with hydrogen is reasonable. However, there are few detailed experimental studies of load control strategies for an ammonia‑hydrogen engine. In this study, four load control strategies including the variation of ammonia volume share (AVS), qualitative control, quantitative control, and adjustment of intake variable valve timing (VVT) are proposed and assessed for their applicability in an ammonia/hydrogen dual-fuel engine. The ignition and combustion characteristics of ammonia do not allow for high thermal efficiency, so the Miller cycle is introduced to improve engine performance. The engine employs fuel supply modes of ammonia port injection and hydrogen direct injection at 1500 rpm. In general, the engine achieves higher brake mean effective pressure (BMEP) and brake thermal efficiency (BTE) at different AVS. Moreover, qualitative control and adjustment of intake VVT allow the engine to own a wide regulation range of BMEP and maintain the BTE of more than 37% under most conditions. However, quantitative control appears to be an inadequate strategy for the engine due to the lower BMEP and BTE.

Understanding hydrogen jet dynamics for direct injection hydrogen engines

The energy paradigm is shifting toward carbon-free and low-emission alternative fuels. Among the many candidates, hydrogen is considered a promising option thanks to its favorable fuel properties, including zero carbon content, high gravimetric energy density, and fast flame speed, despite its technical fuel production and storage challenges. Direct injection technology has been identified as the best approach for applying hydrogen in combustion engines to overcome the accompanying issues, such as backfire and low energy density. However, studies have yet to be conducted on hydrogen jet behavior in direct injection systems, specifically, studies that elucidate engine design and injection parameter optimization in the combustion system. Therefore, we aimed to assess hydrogen jet behavior through experiments and computational approaches comprehensively. Hydrogen was injected at 10 MPa using the direct injection method into a constant volume chamber under a quasi-steady ambient condition. Z-type high-speed Schlieren imaging was performed using a high-speed camera to visualize the hydrogen jet structure, which depicted the hydrogen jet’s vapor intermittency and vortex structure. We also performed a computational fluid dynamics (CFD) simulation to understand the aerodynamics of the jet. The results showed the formation of vortical flow in the inner core region, where the pressure was comparatively lower than that on the outer side of the jet. Our further investigation of the injection strategy showed that multiple injections were more beneficial in forming a favorable hydrogen-air mixture near the spark plug than a single injection case.

Combustion Chamber Development to Maximize the Performance of the Hydrogen Combustion Engine for the T1 Ultimate Category of the Dakar Rally Competition

<div class="section abstract"><div class="htmlview paragraph">As the world strives toward the common goal of carbon neutrality by 2050, motorsport cannot be allowed to stand alone as an exception. A gradual energy transition is clearly underway in the automotive industry but has already begun in motorsport as well. Among other initiatives, the Dakar Rally and the FIA have created the T1 ultimate category for prototypes powered by low-carbon fuels, including hydrogen. The Dakar is the pinnacle of off-road endurance rally competitions. It offers a great opportunity to ORECA Magny-Cours and FEV to expose their jointly developed internal combustion engine (ICE), fuelled with hydrogen only, to extreme conditions. In addition, the racing environment imposes a unique pace of development which can serve as a catalyst for spurring the H<sub>2</sub>-ICE technology. Moreover, a hydrogen powered engine is an interesting fit for motorsports because it combines high power output, a relatively long driving range and driving pleasure with an excellent carbon footprint.</div><div class="htmlview paragraph">This article outlines how ORECA Magny-Cours and FEV are currently converting a gasoline racing engine to hydrogen direct injection to meet the numerous challenges of the Dakar Rally. In several development steps, a combustion chamber was newly developed that is tailored to gaseous hydrogen combustion. A high level of charge motion and optimized mixture formation have ultimately been realized using FEV’s dedicated H<sub>2</sub>-ICE simulation tool chain. Design changes resulting from the simulation results are incorporated into the engine. Further thermodynamic investigations on an engine test bench will be undertaken by ORECA Magny-Cours to maximize performance while ensuring knock free operation and best engine efficiency. Although there are still development hurdles to overcome, the combined ORECA/FEV experience will bring a viable carbon neutral powertrain solution to compete in the future Dakar Rally.</div></div>

A proposal of a hydrogen injection system in to a miniature turbojet engine

The solution proposed in this article, based on direct injection of hydrogen into the combustion chamber, offers many benefits, including a better volumetric efficiency, complete combustion (avoidance of premature ignition and backfire) and significant benefits in terms of power density when compared to engines, in which hydrogen is injected into the air inlet duct. The article discusses advantages and disadvantages of systems responsible for injecting hydrogen into the combustion chamber based on the operational phases of the GTM 400 engine developed by the JET-POL Company. The use of an electronic controller combined with an injector placed in an appropriate place inside the combustion chamber allow for the mentioned engine to be modified this way to optimize its power, performance and emissions. The article discusses matters related to challenges faced by materials used to make components of hydrogen injectors as well as research on the topic in question with the use of diesel engines. The article considers the impact of a low mass density and hydrogen energy, high speed of sound and low thickness on the injection system and components of a miniature turbojet engine. Physical attributes shaped by hydrogen fuel directly affect the size of components, selection of materials and tribology of turbojet engines. The authors suggest that the solutions used in the research on the GTM 400 engine can be used in the future to build hydrogen systems (hydrogen injection, storage and distribution) for fullscale passenger aircraft jet engines.

Assessment of a synergistic control of intake and exhaust VVT for airflow exchange, combustion, and emissions in a DI hydrogen engine

Variable valve timing (VVT) and Miller cycle are advanced technologies employed to optimize engine performance by improving airflow exchange, which are seldom investigated based on the direct-injection (DI) hydrogen engine. The objective of this study is to assess the effects of intake valve closing (IVC) and exhaust valve opening (EVO) timing on the gas exchange performance, combustion, and emissions of a DI hydrogen engine, after which a synergistic control strategy of IVC and EVO timing is proposed. This work is conducted under wide-open throttle and 1500 rpm. The results indicate that the synergistic control of IVC and EVO timing can increase volumetric efficiency by more than 40%, enhance gas exchange performance, shorten combustion duration, and reduce cyclic variation, resulting in approximately 43.15% brake thermal efficiency. Furthermore, brake mean effective pressure can be increased by more than 60% and NO emissions are controlled to less than 20 ppm by optimizing valve timings.