Hydrogen Engine Research Articles

Unerroric of vibration diagnostics of a hydrogen engine

Unerroric of vibration diagnostics of a hydrogen engine

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.

Optimization of the pilot fuel injection and engine load for an algae biodiesel - hydrogen run dual fuel diesel engine using response surface methodology

The main objective of the study is to enhance the performance and emissions of hydrogen and biodiesel dual-fuel engines by optimizing injection timing and engine load using response surface methodology. The pilot fuel considered for this study is Algae biodiesel. A mono-cylinder water-cooled diesel engine is tested for three different pilot fuel injection timings (23° BTDC, 26° BTDC, and 29° BTDC) and five different engine loads (20%, 40%, 60%, 80%, and 100%). For a dual fuel operation, a maximum brake thermal efficiency of 28.21% and an 85% replacement of liquid charge was achieved at pilot fuel injection timing of 26° BTDC and 100% load based on the experimental results. For the same setting of injection timing of 26° BTDC, the emissions of CO and HC were significantly reduced by 12.12% and 36.13%, respectively, at the 80% load setting. While response surface optimum was found at 72.81% load and 25.73° BTDC Injection timing. At this optimal operating parameter setting, a significant reduction of CO, HC, and NOx emissions by 20.98%, 29.15%, and 1.91%, respectively, was obtained while maintaining a comparable brake thermal efficiency of 25.06% and a replacement of liquid charge by 72.15%, respectively. Thus, a biodiesel-hydrogen dual-fuel diesel engine is one of the green solutions for power generation.

Advanced hydrogen engine for modern transportation industry

Numerous environmental issues, such as climate change brought on by the greenhouse effect, result from the expanding air transportation sector. The internal combustion engine industry faces enormous difficulties due to the dual pressures of energy conservation and environmental protection, making finding new clean energy sources essential. To combat global warming, there is growing interest in achieving carbon-neutral flight. As the globe looks for new solutions to combat climate change and global warming, renewable energy and hydrogen have emerged as the environmental sectors' saviors. One of the key energy vectors for the twenty-first century is hydrogen. Particularly in the transportation industry, hydrogen as an energy carrier has the potential for sustainable development. Compared to other internal combustion engines, a hydrogen-fueled engine has the potential to produce significantly cleaner emissions. Based on the prediction of its future development direction, this paper focuses on the latest advances and challenges of the hydrogen engine, analyzes and summarizes the current research status of the hydrogen engine, and looks forward to its future development.

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.

Simulation study of N2/Ar dilution gas to improve thermal efficiency and reduce NOX emissions in hydrogen engines

Although N2 dilution is effective in reducing NOX emissions in hydrogen engines, it decreases thermal efficiency. Utilizing Ar with N2 as a dilution gas can improve thermal efficiency while reducing NOX emissions. However, the specific effects and mechanisms of the mixed dilution of Ar and N2 on the combustion and emission characteristics of hydrogen engines remain uncertain. This study examined the influence of Ar and N2 on the combustion and NOX emissions by adding Ar and N2 to the intake gas at various dilution rates. The examined cases were as follows: Case 1 (N2 = 100%), case 2 (N2:Ar = 80%:20%), case 3 (N2: Ar = 50%:50%), case 4 (N2:Ar = 20%:80%), and case 5 (Ar = 100%). The findings indicate that increasing the N2 ratio in the dilution significantly reduces NOX emissions, but it also reduces the combustion rate. In contrast, increasing the Ar proportion enhances combustion, resulting in higher peak values of the in-cylinder pressure, temperature, and heat release rate. In case 1 (N2 = 100%), the NOX emissions decreased from 255 to 3 ppm when the dilution rate increased from 5% to 20%. However, this also caused a significant decrease in the thermal efficiency from 44.4% to 22%. This limitation can be mitigated by appropriately increasing the proportion of Ar. Optimal results, with lower NOX emissions (250–500 ppm) and higher thermal efficiency (47.6%–49.3%), were achieved with a dilution rate of 17%–27% and an Ar proportion of 80%–90%.

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.

Knock control in hydrogen-fueled argon power cycle engine with higher compression ratio by water port injection

Hydrogen-fueled Argon Power Cycle engine is a novel concept for high efficiency and zero emissions, which chooses high specific heat ratio argon‑oxygen mixture as working fluid. However, the low specific heat of argon also increases the in-cylinder temperature, causing severe knock, which limits the efficiency of the engine. A typical knock-limited compression ratio for a hydrogen port-injected Argon Power Cycle engine is about 5.5:1 if no specific method is used. This article presents experimental research on the effect of water port injection under 1000 r/min at a compression ratio of 9.6:1 with IMEP ranging from 0.1 to 0.6 MPa and argon ratios of 79%, 85%, and 90%. The net indicated thermal efficiency peaks at 53.50% without a water injection but the knock intensity reaches 3.4 MPa. With the water injection, 16 mg/cycle water is sufficient to eliminate knock and the maximum net indicated thermal efficiency slightly reduces to 52.41%. With the water increased to 51 mg/cycle, a maximum IMEP of 0.64 MPa is achieved with an argon ratio of 85%. Argon ratio shows a marginal effect on the peak net indicated thermal efficiency, but the diagram factor is lower with higher argon ratios. At peak net indicated thermal efficiency conditions of different argon ratios, the diagram factor of Argon Power Cycle engine ranges from 76% to 80%, while a typical diagram factor of an air-breathing hydrogen engine can reach 90%. Both argon‑oxygen and air-breaching hydrogen engines can currently achieve the indicated thermal efficiency of over 52%, but the Argon Power Cycle engine shows a greater potential for further efficiency improvement. This paper suggests that the water injection is a feasible method for the knock suppression of the Argon Power Cycle engine with a marginal negative effect on efficiencies.

Exploring dilution potential for full load operation of medium duty hydrogen engine for the transport sector

The current political scenario and the concerns for global warming have pushed very harsh regulations on conventional propulsion systems based on the use of fossil fuels. New technologies are being promoted, but their current technological status needs further research and development for them to become a competitive substitute for the ever-present internal combustion engine. Hydrogen-fueled internal combustion engines have demonstrated the potential of being a fast way to reach full decarbonization of the transport sector, but they still have to face some limitations in terms of the operating range of the engine. For this reason, the present work evaluates the potential of reaching full load operation on a conventional diesel engine, assuming the minimum modifications required to make it work under H2 combustion. This study shows the methodology through which the combustion model was developed and then used to evaluate a multi-cylinder engine representative of the medium to high duty transport sector. The evaluation included different strategies of dilution to control the combustion performance, and the results show that the utilization of EGR brings different benefits to engine operation in terms of efficiency improvement and emissions reduction. Nonetheless, the requisites defined for the needed turbocharging system are harsher than expected and result in a potential non-conventional technical solution.

Levelised hydrogen production costs for a standalone photovoltaic powered system in Australia

This article presents an analysis of levelised costs of producing hydrogen via the photovoltaic electrolysis in Australia. Eight locations (Darwin, Alice Springs, Brisbane, Perth, Sydney, Mildura, Melbourne, and Hobart) covering six climate zones in Australia are selected for the analysis. They receive varying solar radiation to produce electricity by using photovoltaic systems. In the present work, a standalone photovoltaic electrolysis and hydrogen engine system for 69 kWhe of daily electricity used is studied. Photovoltaic system is designed based on the minimum average monthly solar irradiation received for each selected location. The required photovoltaic array sizes are determined at the optimal slopes of the solar panels. By using the electricity generated from the photovoltaic, hydrogen is generated in electrolyser. The levelised cost of hydrogen was determined and found to be AU$ 6.79-10.62 kg-1. The electrolyser cost was found to be 52-55% of the life cycle cost of the system. Therefore, the cost of an electrolyser is the determinant factor for the levelised hydrogen production cost.

Investigation of boost pressure and spark timing on combustion and NO emissions under lean mixture operation in hydrogen engines

Hydrogen may become a replacement for liquid fossil fuels, contributing to greenhouse gas emissions reductions by improving the thermal efficiency of boosted lean burn spark ignition engines. Single-zone engine combustion models are simple, but can yield useful results as a step in the design process for developing alternative fuel systems. The single-zone thermodynamic model is advanced by implementing a laminar flame speed sub-model to investigate combustion, an extended Zeldovich mechanism for nitric oxide emissions, and incorporating the Livengood-Wu integral model for knock characteristics. The results were validated using published experiments giving satisfactory predictions between simulation and experiment for spark timing variation, manifold air pressure, and equivalence ratios. A detailed analysis of boosted lean burn strategies showed that nitric oxide emissions increased with boosted pressure, hence emissions can be controlled through optimizing the excess air ratio and the start of combustion. Further techniques to achieve high thermal efficiency and to prevent knock for boosted lean burn hydrogen SI engine are discussed.

Sustainable propulsion alternatives in regional aviation: The case of the Canary Islands

Sustainability is one of the main challenges the aviation industry is currently facing. In a global context of energy transition towards cleaner and renewable sources, the sector is developing technologies to fly more efficiently and mitigate its environmental impact. Innovative propulsion alternatives such as biofuels, electric aircraft and hydrogen engines are already a reality or are close to becoming so. To assess their feasibility, a study is conducted on specific routes and aircraft across different flight ranges. The analysis focuses on the Canary Islands, an outermost region of the EU with high mobility and no comparable alternative means of transport. For three routes, flight profiles are analyzed, obtaining the fuel consumption and emissions generated by the conventional propulsion and later applying the sustainable alternatives. The results indicate optimistic perspectives, with reductions in environmental impact ranging between 40% and 75% compared to the present.

Assessing fuel economy and NOx emissions of a hydrogen engine bus using neural network algorithms for urban mass transit systems

Assessing fuel economy and NOx emissions of a hydrogen engine bus using neural network algorithms for urban mass transit systems

Research on optimizing turbo-matching of a large-displacement PFI hydrogen engine to achieve high-power performance

The output power of hydrogen engines is restricted due to the low volume energy density of hydrogen and lean burn, thus a turbocharger is necessary to boost the power intensity, especially for large-displacement hydrogen engines. However, turbine selection for hydrogen engines is complex comparing gasoline engines because of the different exhaust components and low exhaust temperature. In this research, the turbocharger-matching of a 5.13 L hydrogen engine is studied, and the results show the original turbine, whose maximum reduced mass flow is 0.00966 (kg/s)·Kˆ0.5/kPa, cannot achieve the desired power performance at high speeds. The reduced mass flow rate can be calculated, taking into account the effect that exhausts composition and temperature. The accuracy of the method is validated using data from a 2.3 L turbocharged H2ICE at various engine speeds and throttle openings, and the error between the measured and calculated expansion ratio is less than 5% mostly. At last, a well-matching turbine for high engine speeds of the 5.13 L hydrogen engine to meet the desired power of 120 kW, whose maximum reduced mass flow is extended to 0.0156 (kg/s)·Kˆ0.5/kPa, is selected according to the method, and the maximum power reaches 128.9 kW with a maximum torque of 662.6 N m, improving by 38.7% and 7.7% respectively comparing with the original turbine. However, the output torque reduces by 15.6% at 1200 rpm. The reduced mass flow rate varies significantly in comparison to the turbines that are well suited for low and high engine speeds respectively, thus the Variable Geometry Turbine may be the solution for both low and high speeds simultaneously for hydrogen engines.

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.

Computational study of hydrogen engine combustion strategies: Dual-Fuel compression ignition with Port- and Direct-Injection, Pre-Chamber Combustion, and Spark-Ignition

This work attempted to identify the best strategy for hydrogen internal combustion (IC) engines. Computational simulations were conducted to evaluate the combustion and emission characteristics of four combustion strategies: H2/diesel dual-fuel combustion with port-(DF-PI) and direct-injection (DF-DI) of H2, pre-chamber combustion (PCC), and port-injection spark-ignition (SI). Two ultra-lean conditions with an overall lambda (λ) of 2.5 and 3.0 were considered. A pilot energy fraction of 3% was applied in both DF modes to limit carbon oxide emissions. Note that since the DF-DI mode is free of end-gas autoignition, a high compression ratio at 17:1 was applied in contrast to the other three cases (13:1). Of the four strategies, the DF-DI and SI operations tended to yield the higher optimal indicated thermal efficiency (ITE) than the DF-PI and PCC modes, due to the highest expansion ratio and usable earliest spark timing, respectively. However, the diffusion combustion-dominant DF-DI operation generated the highest nitric oxides (NOx) emission, owing to the wide stoichiometric high-temperature flame periphery. Because of the pilot-intensified combustion process, the DF-PI operation was easy to induce end-gas autoignition, which considerably limited its load extension and improvement of ITE. In addtition, for both the DF-PI and DF-DI operations, their NOx emissions were challenging to be eliminated even with a modeled exhaust gas recirculation rate at 50% using water injection, indicating that a DI water injection method or an after-treatment system must be implemented for the further reduction of NOx emission. In contrast, both the PCC and SI modes were able to fulfill the EU VI regulation limit of NOx emission with a relatively high ITE. Considering that these two modes only need a single fuel supply system, they are considered more promising for practical applications than the DF-PI and DF-DI modes.

Japan's elite motor companies unite to develop hydrogen engines

Japan's elite motor companies unite to develop hydrogen engines

Experimental study and optimization of performance characteristics of compression ignition hydrogen engine with diesel pilot injection

World's energy demand is majorly met by fossil fuels. An increase in the demand for energy and the depletion of fossil fuels leads to look for the alternate source of energy. Hydrogen is one of the most viable alternate sources of alternate energy. This paper presents the performance study of a Compression Ignition engine using a fuel combination of diesel and hydrogen-diesel. The performance parameters have been analyzed with two input factors, load and Compression Ratio and three output responses, Brake Thermal efficiency (BTE), Brake Specific Fuel Consumption (BSFC) and Volumetric efficiency. The experimental results indicate the improvement in BTE, reduction in BSFC and volumetric efficiency. The BTE was improved by 6.38%, BSFC was reduced by 4.87% and Volumetric efficiency got reduced by 1.89% when hydrogen-diesel fuel is used in place of neat diesel. The experiments have been designed with the help of Design Expert® 13.0.5 using Response Surface Method. The experiments are conducted using Optimal (Custom) design. Mathematical relations are developed between the process parameters and the input factors using regression analysis. The optimal solution has been obtained using the desirability approach. The confirmation experiments have been performed on the optimal solution to verify with the experiment results. Results of the confirmation test shows that the developed mathematical are appropriate for the use in CI engine.

Emission behaviour and aftertreatment of stationary and transient operated hydrogen engines

As society moves towards climate neutrality, hydrogen fuelled internal combustion engines (H2 ICEs) should be considered as a prime technology. These engines are valued for their robustness, superior lifetimes, manufacturing techniques and characteristics, which are already known from diesel or gasoline engines. Since an H2 ICE is run on hydrogen (H2), carbon-based emissions are only released on a very low level from the lube oil. Nitrogen oxides (NOx) emissions are de facto the only gaseous pollutant that must be processed by the exhaust aftertreatment system (EAS) of such engines. This paper provides an overview of the raw exhaust gas emission behaviour of a 2 l four-cylinder passenger car engine that is run solely on hydrogen. As already mentioned, the main challenge faced by the EAS is to reduce NOx. Thus, the inspected EAS includes a selective catalytic reduction (SCR) catalyst with ammonia (NH3) as a reductant. The species of NOx was reduced under stationary operation conditions at all of the considered engine load points at an efficiency of at least 98%. Strategies that could be applied to conduct a load change of an H2 ICE were experimentally investigated. To perform a load change under high performance conditions, H2 ICEs needed to be run on a richer air-fuel mixture than under stationary operation conditions in order to provide enough exhaust enthalpy for the turbocharger. If a richer air-fuel mixture was used, higher NOx emissions were detected, increasing the necessity of an EAS containing an SCR catalyst for H2 ICEs. A WLTC and two RDE cycles were investigated to determine their raw and tailpipe exhaust gas emissions. By applying a simple AdBlue® dosing strategy, the raw NOx exhaust gas emissions from the WLTC could be reduced from 79.9 mg/km to as low as 7.3 mg/km. Carbon-based and secondary emissions such as NH3 and nitrous oxides (N2O) were measured at levels well below 5 mg/km.