A liquid hydrogen car with a two-stroke direct injection engine and LH2-pump

Objectives for the practical application of hydrogen cars are (i) engine-output increase (power-up), suppression of abnormal combustion, and NO_x reduction; (ii) the development of a low cost liquid hydrogen-(LH₂) tank having high thermal insulation; and (iii) the development of a method to supply fuel from the LH₂-tank to the engine. We have developed a hydrogen car system consisting of a LH₂-tank-LH₂-pump-injector to inject high pressure and low temperature hydrogen gas into a two-stroke engine that is capable of meeting all the above-mentioned requirements except (ii). The system was then applied to a mini-car equipped with a 0.551, engine. The performance of the car has demonstrated the above-mentioned capabilities from the engine dynamometer and road tests.     

Development of a high-pressure hydrogen injection for SI engine and results of engine behavior

A high-pressure hydrogen injector was designed and developed in the laboratory. The injector was hydraulically operated by a separate pump. Measurement of injection characteristics on a bench stand showed very repetitive performance of the injector. The injection system was used to supply hydrogen fuel to a single-cylinder spark ignition engine. Results of the tests showed that the engine performance was superior to that achieved with carbureted gasoline fuel.     

Development of a large-sized direct injection hydrogen engine for a stationary power generator

A number of studies on hydrogen engines have targeted small-sized engines for passenger vehicles. By contrast, the present study focuses on a large-sized engine for a stationary power generator. The objective of this study is to simultaneously achieve low NOx emission without aftertreatment, and high thermal efficiency and torque. Experimental analysis has been conducted on a single-cylinder test engine equipped with a gas injector for direct hydrogen injection. The injection strategy adopted in this study aims generating inhomogeneity of hydrogen mixtures within the engine cylinder by setting the injection pressure at a relatively low level while injecting hydrogen through small orifices. High levels of EGR and increased intake boost pressures are also adopted to reduce NOx emission and enhance torque. The results showed that extreme levels of EGR and air-fuel inhomogeneity can suppress NOx emission and the occurrence of abnormal combustion with little negative impact on the efficiency of hydrogen combustion. The maximum IMEP achieved under these conditions is 1.46 MPa (135 Nm@1000 rpm) with engine-out NOx emission of less than 150 ppm (ISNOx < 0.55 g/kW) for an intake boost pressure of 175 kPa and EGR rate of around 50%. To achieve further improvement of the IMEP and thermal efficiency, the Atkinson/Miller cycle was attempted by increasing the expansion ratio and retarding the intake valve closing time of the engine. The test engine used in this study finally achieved an IMEP of 1.64 MPa (150 Nm@1000 rpm) with less than 100 ppm of NOx emission (ISNOx < 0.36 g/kWh) and more than 50% of ITE.     

Backfire prediction in a manifold injection hydrogen internal combustion engine

Hydrogen internal combustion engine (H2ICE) easily occur inlet manifold backfire and other abnormal combustion phenomena because of the low ignition energy, wide flammability range and rapid combustion speed of hydrogen. In this paper, the effect of injection timing on mixture formation in a manifold injection H2ICE was studied in various engine speed and equivalence ratio by CFD simulation. It was concluded that H2ICE of manifold injection have an limited injection end timing in order to prevent backfire in the inlet manifold. Finally, the limit of injection end timing of the H2ICE was proposed and validated by engine experiment.     

可生物降解TC-WⅡ水冷二冲程发动机油的研究

对研制与环境友好的TC-WⅡ水冷二冲程发动机油所需要的各种功能添加剂以及利用部分市售食用植物油、酯类油、低粘度的PAO合成油或加氢基础油复合使用作为可生物降解基础油的可行性进行了探讨。通过对基础油的复合使用,一方面解决了以植物油为可生物降解基础油带来的氧化安定性问题,另一方面解决了以酯类油作为可生物降解基础油带来的成本问题。     

Effect of fuel injection timing and injection pressure on performance in a hydrogen direct injection engine

The in-cylinder hydrogen fuel injection method (diesel engine) induces air during the intake stroke and injects hydrogen gas directly into the cylinder during the compression stroke. Fundamentally, because hydrogen gas does not exist in the intake pipe, backfire, which is the most significant challenge to increasing the torque of the hydrogen port fuel injection engine, does not occur. In this study, using the gasoline fuel injector of a gasoline direct-injection engine for passenger vehicles, hydrogen fuel was injected at high pressures of 5 MPa and 7 MPa into the cylinder, and the effects of the fuel injection timing, including the injection pressure on the output performance and efficiency of the engine, were investigated. Strategies for maximizing engine output performance were analyzed.The fuel injection timing was retarded from before top dead center (BTDC) 350 crank angle degrees (CAD) toward top dead center (TDC). The minimum increase in the best torque ignition timing improved, and the efficiency and excess air ratio increased, resulting in an increase in torque and decrease in NO_x emissions. However, the retardation of the fuel injection timing is limited by an increase in the in-cylinder pressure. By increasing the fuel injection pressure, the torque performance can be improved by further retarding the fuel injection timing or increasing the fuel injection period. The maximum torque of 142.7 Nm is achieved when burning under rich conditions at the stoichiometric air-fuel ratio.     

An experimental study of a direct injection compression ignition hydrogen engine

This paper describes the development of an experimental setup for the testing of a diesel engine in the direct injection hydrogen-fuelled mode. Test results showed that the use of hydrogen direct injection in a diesel engine gave a higher power to weight ratio when compared to conventional diesel-fuelled operation, with the peak power being approximately 14% higher. The use of inlet air heating was required for the hydrogen-fuelled engine to ensure satisfactory combustion, and a large increase in the peak in-cylinder gas pressure was observed. A significant efficiency advantage was found when using hydrogen as opposed to diesel fuel, with the hydrogen-fuelled engine achieving a fuel efficiency of approximately 43% compared to 28% in the conventional, diesel-fuelled mode. A reduction in nitrogen oxides emission formation of approximately 20% was further observed.     

Performance and combustion characteristics of a direct injection SI hydrogen engine

Hydrogen with low spark-energy requirement, wide flammability range and high burning velocity is an important candidate for being used as fuel in spark-ignition engines. It also offers CO₂ and HC free combustion and lean operation resulting in lower _NOx${\mathrm{NO}}_x$ emissions. However, well examined external mixing of hydrogen with intake air causes backfire and knock especially at higher engine loads. In addition, low heating value per unit of volume of hydrogen limits the maximum output power. In this study, attention was paid to full usage of hydrogen advantage employing internal mixing method. Hydrogen was directly injected into cylinder of a single-cylinder test engine using a high-pressure gas injector and effects of injection timing and spark timing on engine performance and _NOx${\mathrm{NO}}_x$ emission were investigated under wide engine loads. The results indicate that direct injection of hydrogen prevents backfire, and that high thermal efficiency and output power can be achieved by hydrogen injection during late compression stroke. Moreover, by further optimization of the injection timing for each engine load, _NOx${\mathrm{NO}}_x$ emission can be reduced under the high engine output conditions.     

Experimental investigation on a DI dual fuel engine with hydrogen injection

Over the past two decades considerable efforts have been undertaken to develop and introduce new alternative fuels for the conventional gasoline and diesel. Many alternative fuels, both liquid and gaseous, have been experimented and some have even been commercialized such as ethanol, natural gas, etc. Hydrogen has been considered as an excellent fuel to replace the petroleum‐based fuels due to its clean burning characteristics. In the present experimental investigation, hydrogen was injected in the intake manifold and diesel fuel was injected inside the engine cylinder in the conventional manner. Hydrogen injection parameters such as injection timing, injection duration and quantity of hydrogen injected were optimized based on the performance and emission characteristics. Exhaust gas recirculation (EGR) technique was adopted to reduce the oxides of nitrogen emission. From the results it was observed that for hydrogen diesel dual fuel (DF) engine, the optimal operating parameters for hydrogen injection were start of injection at gas exchange top dead centre with injection duration of 30° crank angle with the hydrogen flow rate of 7.5 litres per minute (lpm). With EGR the optimized condition was found to be 20% for the entire load. The brake thermal efficiency with 20% EGR increases by 16% at 75% load as compared with diesel, while at full load it reduces by 8% due to the recirculation of exhaust gases that results in a reduction of intake oxygen concentration compared with part load. NO_X emission decreases by five and half times, while other emissions increase by 1.4 times as compared with DF engine. Copyright © 2008 John Wiley & Sons, Ltd.     

Optimization of injection system for a medium-speed four-stroke spark-ignition marine hydrogen engine

In order to avoid the abnormal combustion in high-power hydrogen engine, a 3D CFD numerical model of a direct-injection spark-ignition hydrogen engine was built up based on a large-bore medium-speed four-stroke marine diesel engine using CONVERGE software. To obtain the influence of injection parameters on mixture homogeneity, a dimension reduction optimization method was proposed. The results revealed that the turbulence intensity and the penetration distance varied with the injection parameters, determined the level of mixture homogeneity. The performance comparison between the hydrogen engine and prototype diesel engine showed a great potential of hydrogen in internal combustion (IC) engines.     

Combustion and emission characteristics of a two-stroke diesel engine operating on alcohol

Though, as a renewable energy resource, alcohol fuel has many advantages in China, it is difficult for diesel engines to operate on alcohol due to its low cetane number and high latent heat of vaporization. This paper proposes an approach to its ignition problem by combining internal exhaust gas recirculation (EGR) with injection of small diesel fuel. Based on this approach, a two-stroke single-cylinder diesel engine was developed. Preliminary studies demonstrated that the engine can run on alcohol with almost zero level of smoke and low exhaust gas temperature, and that the engine operating on alcohol has lower nitrogen oxide (NO_x) emissions and 2–3% higher effective thermal efficiency than that operating on diesel fuel in moderate and high load zones.     

Evaluation of Miller cycle and fuel injection direction strategies for low NOx emission in marine two-stroke engine

A full cycle computational fluid dynamics (CFD) simulation model has been established to study the effect of injection direction and exhaust valve close (EVC) timing on performance and emissions for a slow speed marine engine. In order to find more combustion details, the model was coupled with simplified chemical kinetics mechanism. Meanwhile the paper presents the optimization results combining variable injection direction with late exhaust valve closing (LEVC). The results indicate that the consistency of injection direction and flow direction has an important impact on fuel economy. To improve fuel consumption, the injection direction must be carefully adjusted within certain limits. A certain degree of sacrifice in fuel economy is reflected on the transient calculation using the LEVC strategy. However, significant improvement in NOx (nitrogen oxides) emission can be achieved accordingly. With optimized EVC timing and injection direction, lower NOx emission can be realized with no penalty of fuel consumption.     

Research on the hydrogen injection strategy of a direct injection natural gas/hydrogen rotary engine considering apex seal leakage

The purpose of the present paper is to investigate the hydrogen injection strategy on the combustion performance of a natural gas/hydrogen rotary engine. Considering that apex seal leakage (ASL) is an inevitable problem in the actual working process of a rotary engine, the action of ASL cannot be ignored for an in-depth study of its combustion performance. Therefore, in this paper, a 3D dynamic simulation model that put the effect of ASL into consideration was established. Furthermore, based on the established 3D model, the combustion process of a natural gas/hydrogen rotary engine under various hydrogen injection angle (HIA) and hydrogen injection timing (HIT) was investigated. The results indicated that the hydrogen jet flow first impacted on the rotor wall after entering the cylinder, and then diffused under the action of the vortexes in the cylinder. Therefore, the HIA and HIT could change the hydrogen distribution by changing the hydrogen impact location and the intensities of the vortexes in the cylinder. In addition, the ideal hydrogen distribution at the ignition timing which could improve the combustion efficiency was given. That is, under the premise of ensuring minimized hydrogen leakage, the hydrogen should mainly distribute in the middle and the front of the cylinder, and a high hydrogen concentration is maintained near the spark plug.     

Hydrogen injection in two-stroke reciprocating gas engines

A research study in the field of hydrogen-fed engines aims to obtain sufficient maximum power and to avoid any combustion anomaly which might prevent the engine from operating in normal conditions. Thus to investigate the direct injection of hydrogen into the cylinder, with the aim of better combustion with subsequent higher specific outputs, would seem, in the present state of the art, very interesting. During research directed at finding the optimum performance of the engine, three parameters were changed, namely: the quantity of injected hydrogen, total injection timing and timing of ignition before top dead center. This experimental set-up was performed for several injection nozzles using a two-stroke Piaggio engine of 200 cc.     

A hydrogen injection system with solenoid valves for a four-cylinder hydrogen-fuelled engine

A four-cylinder four-stroke water-cooled gasoline engine with spark ignition is refitted to an in-cylinder injection spark-ignition hydrogen-fuelled engine, and the concept of its test apparatus is set up. The study to be reported in this paper focuses mainly on modification for its hydrogen supply system and combustion system to solve such problems as small power output and abnormal combustion in a hydrogen-fuelled engine. A fast response solenoid valve, which possesses good switch characteristics and very fast response, and its electronic control system are described. A high pressure hydrogen injector is designed to improve hydrogen jet penetration and mixture formation in the combustion chamber, and to prevent backfire occurring in the hydrogen supply pipe between the fast response valve and the combustion chamber. Ignition by spark plug is adopted and an Intel 8098 chip microprocessor is developed to control ignition and injection timing optimally. This study shows that abnormal combustion, such as backfire, pre-ignition, high pressure rise rate and knock, can be controlled and performance of the engine can be improved by means of this system.     

NOx emission from a two-stroke ship engine. Part 1: Modeling aspect

International Maritime Organization regulations forces ship owners to measure NO_x emission from ship engines, but standard equipped engine rooms has not installed any usable apparatus to analyze of exhaust gases. In this paper, we propose a method of NO_x emission estimation based on the measurements of working parameters of two-stroke ship engine. This estimation consists of both the model enabling to determine a temperature and model of composition of a gas mixture in the combustion chamber of the engine. Application of such model does not require carrying out direct measurements of engine exhaust gases by exhaust gas analyzers. For the developed method, results of engine working parameters should be sufficient to estimate the NO_x emission according to IMO regulations.     

Effects of second hydrogen direct injection proportion and injection timing on combustion and emission characteristics of hydrogen/n-butanol combined injection engine

Hydrogen and n-butanol are superior alternative fuels for SI engines, which show high potential in improving the combustion and emission characteristics of internal combustion engines. However, both still have disadvantages when applied individually. N-butanol fuel has poor evaporative atomization properties and high latent heat of vaporization. Burning n-butanol fuel alone can lead to incomplete combustion and lower temperature in the cylinder. Hydrogen is not easily stored and transported, and the engine is prone to backfire or detonation only using hydrogen. Therefore, this paper investigates the effects of hydrogen direct injection strategies on the combustion and emission characteristics of n-butanol/hydrogen dual-fuel engines based on n-butanol port injection/split hydrogen direct injection mode and the synergistic optimization of their characteristics. The energy of hydrogen is 20% of the total energy of the fuel in the cylinder. The experimental results show that a balance between dynamics and emission characteristics can be found using split hydrogen direct injection. Compared with the second hydrogen injection proportion (IP2) = 0, the split hydrogen direct injection can promote the formation of a stable flame kernel, shorten the flame development period and rapid combustion period, and reduce the cyclic variation. When the IP2 is 25%, 50% and 75%, the engine torque increases by 0.14%, 1.50% and 3.00% and the maximum in-cylinder pressure increases by 1.9%, 2.3% and 0.6% respectively. Compared with IP2 = 100%, HC emissions are reduced by 7.8%, 15.4% and 24.7% and NOx emissions are reduced by 16.4%, 13.8% and 7.9% respectively, when the IP2 is 25%, 50% and 75%. As second hydrogen injection timing (IT2) is advanced, CA0-10 and CA10-90 show a decreasing and then increasing trend. The maximum in-cylinder pressure rises and falls, and the engine torque gradually decreases. The CO emissions show a trend of decreasing and remaining constant. However, the trends of HC emissions and NOx emissions with IT2 are not consistent at different IP2. Considering the engine's dynamics and emission characteristics, the first hydrogen injection proportion (IP1) = 25% plus first hydrogen injection timing (IT1) = 240°CA BTDC combined with IP2 = 75% plus IT2 = 105°CA BTDC is the superior split hydrogen direct injection strategy.     

Time-averaged heat transfer correlation for direct injection hydrogen fueled engine

This paper presents the development of an empirical correlation for the prediction of time-averaged heat transfer for a direct-injection hydrogen fueled engine. Computer simulation based on one-dimensional gas dynamics approach was used to perform the time-averaged analysis for the in-cylinder heat transfer. Simulation was performed for 1800 ≤ rpm ≤ 5000, 0.2 ≤ φ ≤ 1.2 and 130 deg before top dead center (BTDC) ≤ SOI ≤ 70 deg BTDC. Experimental measurements were used to verify the developed model, during which the engine performance could be determined to a reasonable accuracy of 10%. The equivalence ratio (φ) was considered as a governing variable, through the new correlation for the time-averaged heat transfer. A nonlinear regression approach was used to develop the new correlations. In the case of all the simulation data, the proposed correlations have a satisfactory performance with the determination coefficient (R²) of about 0.99. A relative error of 10% was found in more than 95% of the simulation data. However, the relative error was reduced to about 50% in the newly developed correlations, which increased its reliability to more than the Taylor's correlation for representing the actual data. Due to the general form, hydrocarbon fuel is suitable for the newly developed correlations that are theoretically made.