CFD analysis of hydrogen injection pressure and valve profile law effects on backfire and pre-ignition phenomena in hydrogen-diesel dual fuel engine

This paper focuses on optimizing the hydrogen TMI (timed manifold injection) system through valve lift law and hydrogen injection parameters (pressure, injection inclination and timing) in order to prevent backfire phenomena and improve the volumetric efficiency and mixture formation quality of a dual fuel diesel engine operating at high load and high hydrogen energy share. This was achieved through a numerical simulation using CFD code ANSYS Fluent, developed for a single cylinder hydrogen-diesel dual fuel engine, at constant engine speed of 1500 rpm, 90% of load and 42.5% hydrogen energy share. The developed tool was validated using experimental data. As a results, the operating conditions of maximum valve lift = 10.60 mm and inlet valve closing = 30 °CA ABDC (MVL10 IVC30) prevent the engine from backfire and pre-ignition, and ensure a high volumetric efficiency. Moreover, a hydrogen start of injection of 60 °CA ATDC (HSOI60) is appropriate to provide a pre-cooling effect and thus, reduce the pre-ignition sources and helps to quench any hot residual combustion products. While, the hydrogen injection pressure of 2.7 bar and an inclination of 60°, stimulate a better quality of hydrogen-air mixture. Afterwards, a comparison between combustion characteristics of the optimized hydrogen-diesel dual fuel mode and the baseline (diesel mode) was conducted. The result was, under dual fuel mode there is an increase in combustion characteristics and NOx emissions as well as a decrease in CO2 emissions. For further improvement of dual fuel mode, retarding diesel start of injection (DSOI) strategy was used.     

Studies on the effect of hydrogen induction on performance,emission and combustion behaviour of a WCO emulsion based dual fuel engine

This paper aims at studying the effect of hydrogen induction on engine performance, emission and combustion behaviour of a diesel engine fuelled with the emulsion of used palm oil (called as WCO-waste cooking oil) as pilot fuel and hydrogen as primary fuel. A single cylinder water-cooled direct injection diesel engine was tested at 100% and 40% loads. Results were compared with neat diesel, neat WCO and WCO emulsion at both loads in single fuel operation. WCO emulsion in single fuel mode indicated improvement in performance and reduction in all emissions as compared to neat WCO. Dual fuel operation with hydrogen induction further reduced the emissions of smoke HC and CO with WCO as pilot fuel at all power outputs. However, hydrogen induction resulted in reduced thermal efficiency at 40% load. WCO emulsion showed higher ignition delay as compared to neat WCO. Dual fuel operation with hydrogen induction increased the ignition delay further. Heat release pattern showed higher premixed combustion rate with hydrogen induction mainly at high power outputs. Premixed combustion rate became very high at higher rates of hydrogen admission mainly at high power output. In general, hydrogen induction showed superior performance at high power output and inferior performance at low power output with WCO emulsion as injected fuel.     

A renewable pathway towards increased utilization of hydrogen in diesel engines

In the present work, dual fuel operation of a diesel engine has been experimentally investigated using biodiesel and hydrogen as the test fuels. Jatropha Curcas biodiesel is used as the pilot fuel, which is directly injected in the combustion chamber using conventional diesel injector. The main fuel (hydrogen) is injected in the intake manifold using a hydrogen injector and electronic control unit. In dual fuel mode, engine operations are studied at varying engine loads at the maximum pilot fuel substitution conditions. The engine performance parameters such as maximum pilot fuel substitution, brake thermal efficiency and brake specific energy consumption are investigated. On emission side, oxides of nitrogen, hydrocarbon, carbon monoxide and smoke emissions are analysed. Based on the results, it is found that biodiesel-hydrogen dual fuel engine could utilize up to 80.7% and 24.5% hydrogen (by energy share) at low and high loads respectively along with improved brake thermal efficiency. Furthermore, hydrocarbon, carbon monoxide and smoke emissions are significantly reduced compared to single fuel diesel engine operation. Exhaust gas recirculation (EGR) has also been studied with biodiesel-hydrogen dual fuel engine operations. It is found that EGR could improve the utilization of hydrogen in dual fuel engine, especially at the high loads. The effect of EGR is also found to reduce high nitrogen oxide emissions from the dual fuel engine and brake thermal efficiency is not significantly affected.     

Optimization control of hydrogen engine ignition system based on ACO-BP

With the development of new energy, hydrogen fuel engines have become a research boom in the automotive field. But there are abnormal problems such as backfire and pre-ignition during the combustion of hydrogen engines. This paper is based on the Ant Colony Optimization-Back Propagation (ACO-BP) algorithm to study the influence of different speed and load conditions on the ignition advance angle, so as to optimize the control of the hydrogen engine. The experimental system is established on a hydrogen engine converted from a 492Q gasoline engine. The prediction of the optimal ignition advance angle was obtained through experiments, and the optimal ignition MAP diagram of the hydrogen engine is constructed. The optimal ignition advance angle under different working conditions can effectively avoid the occurrence of hydrogen engine pre-ignition. The accuracy reaches 0.0018209 when the training reaches 14 times, the fitness between the actual value and the predicted value of ACO-BP training is 0.99921, the verification accuracy reaches 0.99913, and the test accuracy reaches 0.99932. Compared with the three optimization methods, the convergence speed and error accuracy of ACO-BP are significantly better than the BP neural networks and Genetic Algorithm-Back Propagation (GA-BP). This method realized the model of the nonlinear mapping model from hydrogen engine speed and load to optimal ignition advance angle, which is of great significance for solving the problem of abnormal combustion in hydrogen engine.     

Research on diagnosis of pre-ignition of hydrogen engine based on SOM-MAS

Abnormal combustion is an important factor in the development process of hydrogen engine and it mainly includes pre-ignition, backfire and knocking, among which pre-ignition has the most serious impact on hydrogen engine. In this paper, it is divided into four types: normal combustion, slight pre-ignition, moderate pre-ignition and severe pre-ignition according to different crankshaft rotation angles. In order to identify different combustion types, this paper proposes a fault diagnosis model based on the fusion of SOM neural network and Multi-Agent System (SOM-MAS). Firstly, different combustion types are identified by SOM. Secondly, the abnormal combustion is tracked and located mainly through the Multi-Agent System, and the location of the abnormality is identified. Finally, based on 44 sets of pressure data samples collected from the in-cylinder combustion of a hydrogen engine on the experimental bench, different combustion types were diagnosed and identified, and the location of abnormal combustion faults was tracked, which verifies the effectiveness of the proposed method shows that the method has certain feasibility and superiority for the diagnosis of hydrogen engine pre-ignition.     

Performance and combustion characteristic of CI engine fueled with hydrogen enriched diesel

The combustion of hydrogen–diesel blend fuel was investigated under simulated direct injection (DI) diesel engine conditions. The investigation presented in this paper concerns numerical analysis of neat diesel combustion mode and hydrogen enriched diesel combustion in a compression ignition (CI) engine. The parameters varied in this simulation included: H₂/diesel blend fuel ratio, engine speed, and air/fuel ratio. The study on the simultaneous combustion of hydrogen and diesel fuel was conducted with various hydrogen doses in the range from 0.05% to 50% (by volume) for different engine speed from 1000 – 4000 rpm and air/fuel ratios (A/F) varies from 10 – 80. The results show that, applying hydrogen as an extra fuel, which can be added to diesel fuel in the (CI) engine results in improved engine performance and reduce emissions compared to the case of neat diesel operation because this measure approaches the combustion process to constant volume. Moreover, small amounts of hydrogen when added to a diesel engine shorten the diesel ignition lag and, in this way, decrease the rate of pressure rise which provides better conditions for soft run of the engine. Comparative results are given for various hydrogen/diesel ratio, engine speeds and loads for conventional Diesel and dual fuel operation, revealing the effect of dual fuel combustion on engine performance and exhaust emissions.     

A coupling dynamics and thermodynamics study of diesel pilot-ignition injection effect on hydrogen combustion of a linear engine

Linear hydrogen engine is a new type of energy conversion device to supports variable compression ratio operation for clean emission. However, the new hydrogen engine using conventional spark ignition shows slow combustion speed and low thermal efficiency. This study makes a preliminary assessment to discuss the application of diesel pilot-ignition technology in linear hydrogen engine aiming to accelerate combustion and improve efficiency. A new coupling model between dynamics and thermodynamics is proposed and then iteratively calculated to give insight the interrelationship of combustion and motion in a diesel pilot-ignited linear hydrogen engine, while the effect of injection position on the hydrogen engine combustion is also investigated to make clear the feasibility of combustion optimization. The results indicate that the linear hydrogen engine is speeded by properly advancing the injection to promote combustion, and it has a positive effect on in-cylinder gas temperature, pressure and pressure rise rate, unless the injection is too early which results in higher NO emissions and aggravate the working intensity of the engine. In addition, the closer the fuel injection is to the top dead center, the incomplete combustion of hydrogen and diesel in the cylinder, the decrease of engine fuel economy and the increase of soot emissions. There is an optimal thermal efficiency of 40.7% for the LHE when it operates in the 0.8 mm injection position condition.     

An onboard hydrogen generator for hydrogen enhanced combustion with internal combustion engine

Hydrogen enhanced combustion (HEC) for internal combustion engine is known to be a simple mean for improving engine efficiency in fuel saving and cleaner exhaust. An onboard compact and high efficient methanol steam reformer is made and installed in the tailpipe of a vehicle to produce hydrogen continuously onboard by using the waste heat of the engine for heating up the reformer; this provides a practical device for the HEC to become a reality. This use of waste heat from engine enables an extremely high process efficiency of 113% to convert methanol (8.68 MJ) for 1.0 NM of hydrogen (9.83 MJ) and low cost of using hydrogen as an enhancer or as a fuel itself. The test results of HEC from the onboard hydrogen production are presented with 2 gasoline engine vehicles and 2 diesel engines; the results indicate a hike of engine efficiency in 15–25% fuel saving and a 40–50% pollutants reduction including 70% reduction of exhaust smoke. The use of hydrogen as an enhancer brings about 2–3 fold of net reductions in energy, carbon dioxide emission and fuel cost expense over the input of methanol feed for hydrogen production.     

Performance and emission characteristics of CIE using hydrogen,biodiesel, and massive EGR

Hydrogen is considered as an excellent energy carrier and can be used in diesel engines that operate in dual fuel mode. Many studies have shown that biodiesel, which is sustainable, clean, and safe, a good alternative to fossil fuel. However, tests have confirmed that using biodiesel or hydrogen as a fuel or added fuel in compression ignition engines increases NOx concentrations. Cooled or hot exhaust gas recirculation (EGR) effectively controls the NOx outflows of diesel engines. However, this technique is restricted by high particulate matter PM emissions and the low thermal efficiency of diesel engines.In this study, gaseous hydrogen was added to the intake manifold of a diesel engine that uses biodiesel fuel as pilot fuel. The investigation was conducted under heavy-EGR conditions. An EGR system was modified to achieve the highest possible control on the EGR ratio and temperature. Hot EGR was recirculated directly from the engine exhaust to the intake manifold. A heat exchanger was utilized to maintain the temperature of the cooled EGR at 25 °C.The supplied hydrogen increased NOx concentrations in the exhaust gas emissions and high EGR rates reduced the brake thermal efficiency. The reduction in NOx emissions depended on the added hydrogen and the EGR ratios when compared with pure diesel combustion. Adding hydrogen to significant amounts of recycled exhaust gas reduced the CO, PM, and unburned hydrocarbon (HC) emissions significantly. Results showed that using hydrogen and biodiesel increases engine noise, which is reduced by adding high levels of EGR.     

Influence of operating parameters on performance and emissions for a compression-ignition engine fueled by hydrogen/diesel mixtures

Hydrocarbon exhaust emissions are mainly recognized as a consequent of carbon-based fuel combustion in compression ignition (CI) engines. Alternative fuels can be coupled with hydrocarbon fuels to control the pollutant emissions and improve the engine performance. In this study, different parameters that influence the engine performance and emissions are illustrated with more details. This numerical work was carried out on a dual-fuel CI engine to study its performance and emission characteristics at different hydrogen energy ratios. The simulation model was run with diesel as injected fuel and hydrogen, along with air, as inducted fuel. Three-dimensional CFD software for numerical simulations was implemented to simulate the direct-injection CI engine. A reduced-reaction mechanism for n-heptane was considered in this work instead of diesel. The Hiroyasu-Nagel model was presented to examine the rate of soot formation inside the cylinder. This work investigates the effect of hydrogen variation on output efficiency, ignition delay, and emissions. More hydrogen present inside the engine cylinder led to lower soot emissions, higher thermal efficiency, and higher NO_x emissions. Ignition timing delayed as the hydrogen rate increased, due to a delay in OH radical formation. Strategies such as an exhaust gas recirculation (EGR) method and diesel injection timing were considered as well, due to their potential effects on the engine outputs. The relationship among the engine outputs and the operation conditions were also considered.     

Engine combustion and emission fuelled with natural gas: A review

Natural gas (NG) is one of the most important and successful alternative fuels for vehicles. Engine combustion and emission fuelled with natural gas have been reviewed by NG/gasoline bi-fuel engine, pure NG engine, NG/diesel dual fuel engine and HCNG engine. Compared to using gasoline, bi-fuel engine using NG exhibits higher thermal efficiency; produces lower HC, CO and PM emissions and higher NOx emission. The bi-fuel mode can not fully exert the advantages of NG. Optimization of structure design for engine chamber, injection parameters including injection timing, injection pressure and multi injection, and lean burn provides a technological route to achieve high efficiency, low emissions and balance between HC and NOx. Compared to diesel, NG/diesel dual fuel engine exhibits longer ignition delay; has lower thermal efficiency at low and partial loads and higher at medium and high loads; emits higher HC and CO emissions and lower PM and NOx emissions. The addition of hydrogen can further improve the thermal efficiency and decrease the HC, CO and PM emissions of NG engine, while significantly increase the NOx emission. In each mode, methane is the major composition of THC emission and it has great warming potential. Methane emission can be decreased by hydrogen addition and after-treatment technology.     

An experimental investigation on DI diesel engine with hydrogen fuel

The internal combustion engines have already become an indispensable and integral part of our present day life style, particularly in the transportation and agricultural sectors [Nagalingam B. Properties of hydrogen. In: Proceedings of the summer school of hydrogen energy, IIT Madras, 1984]. Unfortunately the survival of these engines has, of late, been threatened due to the problems of fuel crisis and environmental pollution. Therefore, to sustain the present growth rate of civilization, a nondepletable, clean fuel must be expeditiously sought. Hydrogen exactly caters to the specified needs. Hydrogen, even though “renewable” and “clean burning”, does give rise to some undesirable combustion problems in an engine operation, such as backfire, pre-ignition, knocking and rapid rate of pressure rise [Srinivasa Rao P. Utilization of hydrogen in a dual fueled engine. In: Proceedings of the summer school of hydrogen energy, IIT Madras, 1984; Siebers DL. Hydrogen combustion under diesel engine conditions. Hydrogen Energy 1998;23:363–71]. The present investigation compares the performance and emission characteristics of a DI diesel engine with gaseous hydrogen as a fuel inducted by means of carburation technique and timed port injection technique (TPI) along with diesel as a source of ignition [Swain N, Design and testing of dedicated hydrogen-fueled engine. SAE 961077, 1996]. In the present study the specific energy consumption, NO_x emission and the exhaust gas temperature increased by 6%, 8% and 14%, respectively, and brake thermal efficiency and smoke level reduced by 5% and 8%, respectively, using carburation technique compared to baseline diesel. But in the TPI technique, the specific energy consumption, exhaust gas temperature and smoke level reduced by 15%, 45% and 18%, respectively. The brake thermal efficiency and NO_x increased by 17% and 34%, respectively, compared to baseline diesel. The emissions such as HC, CO, and CO₂ is very low in both carburation and TPI techniques compared baseline diesel.     

Analysis of different combustion chamber geometries using hydrogen / diesel fuel in a diesel engine

ABSTRACT

In this study, the effects on combustion characteristics and emission were investigated in a direct injection diesel engine. In experimental and numerical studies, the engine was operated at 2000 rpm. The analyzes were made in the AVL-FIRE ESE Diesel part with Computational Fluid Dynamics (CFD) software. Standard combustion chamber (SCC) and Modified combustion chamber (MCC) geometry were compared in the modeling. By means of the designed MCC combustion chamber geometry, the fuel released from the injector was directed to the piston bowl area. Therefore, the mixture was homogenized and the combustion had been improved. In addition, the evaporation rate of the mixture increased with the MCC geometry. Also, lower NO and CO emissions were obtained with the MCC model compared to the SCC model. On the other hand, diesel fuel and mass 5% hydrogen fuel was used into diesel fuel as fuel in the study. The combustion process was investigated using hydrogen in different combustion chambers. The use of hydrogen as additional fuel resulted in higher combustion pressure, temperature and NO emissions. Compared to SCC type combustion chamber in the MCC type combustion chamber used diesel fuel, CO emission decreased of 6% and 3% for hydrogen-added mixture fuel. Also, compared to SCC type combustion chamber in the MCC type combustion chamber used diesel fuel, NO emission decreased of 11% and 32% for hydrogen-added mixture fuel. Moreover, flame velocity, heat release rate and flame propagation increased with the addition of hydrogen fuel.     

Experimental investigation of combustion characteristics and NOx emission of a turbocharged hydrogen internal combustion engine

In order to alleviate the contradictions of increasingly prominent environmental pollution, greenhouse gas emissions and oil resource security issues, the search for renewable and clean alternative energy sources is getting more and more attention. Hydrogen energy is known as a future energy source because of its safety, reliability, wide range of resources and non-polluting products. Hydrogen internal combustion engine combines the technical advantages of traditional internal combustion engines and has comprehensive comparative advantages in terms of manufacturing cost, fuel adaptability and reliability. It is one of the practical ways to realize hydrogen energy utilization. In this paper, the combustion characteristics and NOx emission of a turbocharged hydrogen engine were investigated using the test data. The results showed the combustion duration (the crank angle of 10%–90% fuel burned) at 1500 rpm and 2000 rpm was equal and the combustion duration is much bigger than the other loads when the BMEP is 0.27 MPa. The reason is the effect of the turbocharger on the gas exchange process, which will influence the combustion process. The cylinder pressure and pressure rise rate were also investigated and the peak pressure rise rate was lower than 0.25 MPa/°CA at all working conditions. Moreover, the NOx emission changed from 300 ppm to 1200 ppm with engine speed increasing and the maximum value can reach to 7000 ppm when the equivalence ratio is 0.88 at 2500 rpm, maximum brake torque. The NOx emission shows different changing tendencies with different working conditions. Finally, these conclusions can be used to develop controlling strategies to solve the contradictions among power, brake thermal efficiency and NOx emission for the turbocharged hydrogen internal combustion engines.     

不同喷醇方式对柴油机实行柴油/醇组合燃烧时性能的影响

提出了柴油／甲醇的组合燃烧方式。在一台高速非增压直喷柴油机上采用组合燃烧方式进行了柴油机燃用甲醇的试验，对比了不同喷醇方式(单点喷醇和多点喷醇)对柴油机实行组合燃烧时性能的影响。试验结果表明，采用组合燃烧方式的柴油机燃用甲醇时，多点喷醇方式获得的动力性、经济性以及排放品质等综合性能要优于单点喷醇方式。     

Combustion and emission characteristics of a hydrogen-diesel dual-fuel engine

Hydrogen generated from renewable sources is an eco-friendly fuel that can be used in automotive industry or for energy generation purposes. Hydrogen is a high-energy content gas and its carbonless chemical structure can provide significant benefits of high thermal efficiency and near zero or very low carbon emissions when combusted with other fuels.In this study, the implementation of hydrogen fuel was tested at low and medium operating loads in a heavy-duty hydrogen-diesel dual-fuel engine. The paper provides a detailed experimental analysis of the effects of hydrogen energy share ratio and various combustion strategies such as exhaust gas recirculation, diesel injection pressure and diesel injection patterns.At low load conditions, engine operation with an H₂ energy share ratio of up to 98% was achieved without any engine operation implications. This condition provided a simultaneous reduction of carbon and NOx emission of over 90% while soot emissions were dropped by 85% compared to the conventional diesel-only operation. At medium load, the increased NOx emission due to the high energy content of hydrogen fuel was found to be the primary challenge.     

Analysis of ignition delay by taking Di-tertiary-butyl peroxide as an additive in a dual fuel diesel engine using hydrogen as a secondary fuel

Ignition delay (ID) is one of the important parameters that make influenced on the combustion process inside the cylinder. This ignition delay affects not only the performances but also the noise and emissions of the engine. In this regards the experiments were conducted on single cylinder 4–stroke compression ignition research diesel engine, power 3.50 kW at constant speed 1500 rpm Kirloskar model TV1 with base fuel as diesel and hydrogen as secondary fuel with and without Di-tertiary-butyl-peroxide (DTBP). Experiments were conducted to measure the ignition delay of the dual fuel diesel (DFD) engine at different load conditions and substitution of diesel by hydrogen with or without DTBP and then it was compared with predicted ID given by Hardenberg-Hase equation and modified Hardenberg-Hase equation.The experimental values of ignition delay were compared with theoretical ignition delay which was predicted on the basis of Hardenberg-Hase equation by considering mean cylinder temperature, pressure, activation energy and cetane number and variations are found in between 6.60% and 21.22%. While, the Hardenberg-Hase equation was modified (by considering variation in activation energy) for DFD engine working on diesel as primary fuel and hydrogen as secondary fuel shows variations 1.20%–11.96%. Furthermore, with DTBP it gives variation up to 18.01%. It was found that ID decreases with increase in percentage of DTBP and hydrogen in air-fuel mixture. This might be due to the cetane improver nature of DTBP, pre-ignition reaction rate and energy release rate of hydrogen fuel. The polytropic index get increased by addition of (Di-tert butyl peroxide) DTBP. Similarly, 5% Di tertiary butyl peroxide reduces Ignition delay.     

Recent studies on hydrogen usage in Wankel SI engine

In this study, investigations on the hydrogen usage in spark ignition (SI) rotary engines are reviewed to assess trend researches. Many scientists conducted various studies to investigate performance, emission and combustion characteristics of hydrogen technology. The studies generally focused on their usage as an additive fuel. It can be seen that hydrogen usage in SI engine are very promising for their lower emissions, more efficient combustion, and higher power output. Nevertheless, hydrogen utilization may cause combustion problems such as back fire, auto and pre-ignition. Moreover, because of their small molecular structure hydrogen storage is another issue. Especially, hydrogen blending is a particular solution and this makes hydrogen gas tolerable for storage and transporting problem. In the recent studies, hydrogen usage in rotary engine is found well suited and feasible by scientists. Combustion difficulties caused by long and narrow shaped combustion chamber and long quenching distance of this type of engine can be solved by hydrogen addition. However, absence of a light, safe and low cost storage technology are still bottlenecks for their usage and waiting for solution.     

Evaluation of fuel consumption and vibration characteristic of a compression ignition engine fuelled with high viscosity biodiesel and hydrogen addition

Viscosity property of a fuel is a crucial point for internal combustion engine characteristics. Performance and emission parameters as well as injector's life of an engine is primarily effected by viscosity of the fuels. In present study, effect of high viscosity biodiesel fuels with hydrogen addition was investigated in a compression ignition engine. Biodiesels that are produced from Pongamia Pinnata and Tung oils were used as pure biodiesels as well as blended with low sulphur diesel fuel at the volume ratios of 50% and 75%. Furthermore, hydrogen gas was injected into intake manifold in order to evaluate its effect with the usage of high viscous liquid fuels. The results revealed that brake specific fuel consumption was increased with biodiesel fuels, whereas hydrogen addition into intake manifold improved the consumption. Total vibration acceleration of the engine reduced with biodiesel and hydrogen additions. Frequency spectrum indicated that this decrement was primarily lowered due to less energy transmitted through engine pistons that converted from chemical energy of fuels.     

A numerical study on a hydrogen assisted diesel engine

This work aims to numerically study the performance, combustion and emission characteristics of a hydrogen assisted diesel engine under various operating conditions. Simulations were performed using multi-dimensional software KIVA4 coupled with CHEMKIN. The Kelvin–Helmholtz and Rayleigh–Taylor hybrid break up model was implemented to accurately model the spray development. A detailed reaction mechanism was constructed to take into account the chemical kinetics of diesel and hydrogen, and it was validated against the experimental results with 0% of hydrogen induction. Simulation results showed that at low engine speeds, the indicated thermal efficiency, in-cylinder pressure and apparent heat release rate increased significantly with the induction of hydrogen. On the other hand, at high engine speed and high load conditions, no tangible changes on the engine performance, combustion characteristics were observed. In terms of emissions, CO and soot emissions were shown to be reduced under most of the engine operating conditions. Whereas for NO_x emissions, a slight increase was observed at low engine speed of 1600 rpm.