The status of handling and storage techniques for liquid hydrogen in motor vehicles

Hydrogen-fueled internal-combustion engines show significant potential for low-pollution exhaust emissions. Especially when internal cryogenic air/fuel mixture formation is employed, the probability is good that exhaust emissions will remain below existing limits. The injection pressure requirements for internal mixture formation could be met by high-pressure fuel pumps for liquid hydrogen. Therefore, research and development work in advanced onboard fuel is of foremost importance. Refilling of liquid-hydrogen vehicular tanks, even by untrained people, and safety aspects are further areas for R&D work. An overview is included in this páper on experience gained from accidents involving liquid-hydrogen-fueled vehicles.     

车用汽油机排气污染控制技术

本文从燃料处理,燃烧系统改进和尾气后处理等方面,提出了改进车用汽油机排气污染所采用的主要技术措施,为车用汽油机节能和改善排放性能指明了方向。     

Vehicle evaluation of neat methanol—compromises among exhaust emissions,fuel economy and driveability

Methanol was evaluated as an alternative fuel in vehicles with spark-ignited, internal-combustion engines. Acceptable driveability was achieved with a methanol-fuelled car equipped with electronic fuel injection (EFI) which was modified to provide proper air-fuel ratios for methanol. the target level for driveability was not achieved with a methanol-fuelled carburetted car modified to provide proper air-fuel ratios for and increased vaporization of methanol. With the EFI car, using the average equivalence ratio (Φ_a = 0·96) and spark timing designed for the production gasoline car, exhaust emissions and fuel economy with methanol fuelling were compared to those with gasoline. With methanol, compared with gasoline, 60 per cent lower NO_x, 3·5 times higher unburned fuel emissions (UBF), and similar CO engine emissions were measured. the air pollution significance of the higher UBF emissions from methanol combustion is unknown because the UBF species (mainly methanol) are different from those from gasoline combustion. A catalytic converter decreased emissions of UBF and CO similarly for both fuels. Fuel economy with methanol—about half that of gasoline on a volume basis—was 7–10 per cent better on an energy basis than that with gasoline. With methanol fuelling, spark timing and Φ_a were varied from production values to obtain a more acceptable compromise among driveability, exhaust emissions and fuel economy. While fuelling with methanol at Φ_a = 0·96, using best power rather than production spark timing increased fuel economy 3 to 6 per cent without significantly affecting emissions and driveability. As Φ_a was leaned to 0·62 while maintaining best-power spark timing engine and tailpipe (after converter) CO emissions decreased, engine UBF emissions increased, NO_x and tailpipe UBF emissions were not greatly affected, and driveability deteriorated. With best-power spark timing and the Φ_a for maximum economy (0·83), driveability was acceptable, and CO and NO_x emissions met the 1977 standards. At Φ_a = 0·83, NO_x emissions were reduced below the statutory standard (0·4 g/mile) by retarding spark timing; however, driveability and fuel economy deteriorated. Although the feasibility and benefits of operating vehicles with neat methanol have been demonstrated, not all problems of methanol fuelling (for example, cold start) were addressed. In addition, other alternatives such as obtaining hydrocarbon liquids from coal or using methanol as fuel for stationary powerplants must also be considered to obtain the most efficient utilization of energy resources.     

A review of hydrogen as a compression ignition engine fuel

Diesel fuelled engines emit higher levels of carbon dioxide and other harmful air pollutants (such as noxious gases and particulates) per litre of fuel than gasoline engines. This fact, combined with the recent diesel emission scandal and the rumours of more widespread cheating by automotive manufacturers have initiated a long discussion about the future and sustainability of diesel engines.Improving the compression ignition engine is a direct way of going green. Reducing the harmful emissions can be achieved by future developments in the engine technology but also the implementation of alternative fuels. Hydrogen is a renewable, high-efficient and clean fuel that can potentially save the future of diesel-type engines. The evolution of high-efficiency renewable hydrogen production methods is the most important path for the start of a new hydrogen era for the compression ignition engine that can improve its sustainability and maximum efficiency.This paper provides a detailed overview of hydrogen as a fuel for compression ignition engines. A comprehensive review of the past and recent research activities on the topic is documented. The review focuses on the in-cylinder combustion of hydrogen either as a primary fuel or in dual fuel operation. The effects of injection strategies, compression ratio and exhaust gas recirculation on the combustion and emission characteristics of the hydrogen fuelled engine are fully analysed. The main limitations, challenges and perspectives are presented.     

改善涡流室柴油机供油系统和利用废气再循环降低排放研究

通过改进柴油机供油系统和利用废气再循环来改善混合气质量和燃烧过程,进而降低其有害排放。结果表明,推迟喷油提前角,适当降低喷油压力,抑制初期喷油率,减小高压油管直径,利用废气再循环以及几种方法的结合能够有效地降低排放。     

Development of a hybrid pneumatic-power vehicle

Many complex technologies have been developed and applied to improve the energy efficiency and exhaust emission of an engine under different driving conditions. The overall thermal efficiency of an internal-combustion engine, however, can be maintained at only about 20–30%, with aggravated problems in the design and development, such as overall difficulty, excessive time consumption or excessively high cost. For electric cars, there is still no major technological breakthrough for the rapid recharging of a large capacity battery and detection of remaining power in it. Although all currently available hybrid-power engines are able to lower the amount of exhaust emissions and the fuel consumption of the engine, they are still unable to achieve a stable and optimal running condition immediately after ignition; hence the engine's thermal-efficiency remains low. To solve the aforementioned problems, an innovative concept – a hybrid pneumatic power-system (HPPS), which stores “flow work” instead of storing electrochemical energy of the battery – is introduced. This innovative power system not only ensures that the internal-combustion ensures optimally but also recycles the exhaust flow to propel the vehicle. The optimization of the internal-combustion and recycling of the exhaust energy can increase the vehicle's efficiency from an original 15% to 33%, an overall increase of 18%.     

Comparative characteristics of compression ignited engines operating on biodiesel produced from waste vegetable oil

Performance and emission characteristics of two compression ignited engines of different compression ratios, number of cylinders, cooling system, and power output are studied. Waste vegetable oil-derived biofuel is used. Engines are fueled with B0, B20 and B100 mixtures. Thermal efficiency, brake specific consumption and engine emissions (CO, Unburned HC, O₂ and NO) are reported and comparisons are made for fuel mixtures running on both engines. Trends of emissions and performance curves are compared to the literature of the available data. It is noted that the biofuel certainly affects unburned HC emissions regardless of engine specifications and/or operating conditions. However, the type of fuel or adding biofuel to diesel may not affect parameters such as exhaust gas temperature and emissions (CO, Unburned HC, O₂, NO). These parameters may change as functions of engine specifications and operating conditions regardless of biofuel or diesel being used. These findings are supported by separate investigations using different biofuels in literature.     

Effects of intake air temperature on SI engine emissions during a cold start

This paper presents the concept of preheating the intake air to reduce cold-start emissions from gasoline engines. The effects of intake air temperature on emissions from a gasoline engine were studied by using an air heater based on spark ignition. A light-duty vehicle test of cold-start emissions was carried out at an ambient temperature of?7°C according to New European Driving Cycle for Euro 3 and Euro 4 exhaust emission legislations. The results showed that preheating the intake air could effectively reduce both hydrocarbon (HC) and carbon monoxide (CO) emissions and improve fuel economy during a cold start. During idling conditions, the key phase of the HC and CO emissions was the first 40 s. With the aid of the air heater, cold-start HC and CO emissions from the vehicle were lower than the limit values in the Euro 3 and Euro 4 regulations.     

车用汽油机有害排放物的形成、影响因素及危害

本文详细地论述了车用汽油机排放的特点,分析了车用汽油机有害排放物的形成、影响因素及危害,并指出降低车用汽油机排气污染,改善人类生存环境已是当务之急。     

燃料性质对发动机排放性能的影响

本文综述了控制发动机有害物质排放的前处理方法,详细分析了燃料的性质对发动机有害物质排放的影响。并指出改进燃料的性质以控制发动机有害物质排放的方向。     

Use of hydrogen in dual-fuel diesel engines

Hydrogen is a promising future energy carrier due to its potential for production from renewable resources. It can be used in existing compression ignition diesel engines in a dual-fuel mode with little modification. Hydrogen's unique physiochemical properties, such as higher calorific value, flame speed, and diffusivity in air, can effectively improve the performance and combustion characteristics of diesel engines. As a carbon-free fuel, hydrogen can also mitigate harmful emissions from diesel engines, including carbon monoxide, unburned hydrocarbons, particulate matter, soot, and smoke. However, hydrogen-fueled diesel engines suffer from knocking combustion and higher nitrogen oxide emissions. This paper comprehensively reviews the effects of hydrogen or hydrogen-containing gaseous fuels (i.e., syngas and hydroxy gas) on the behavior of dual-fuel diesel engines. The opportunities and limitations of using hydrogen in diesel engines are discussed thoroughly. It is not possible for hydrogen to improve all the performance indicators and exhaust emissions of diesel engines simultaneously. However, reformulating pilot fuel by additives, blending hydrogen with other gaseous fuels, adjusting engine parameters, optimizing operating conditions, modifying engine structure, using hydroxy gas, and employing exhaust gas catalysts could pave the way for realizing safe, efficient, and economical hydrogen-fueled diesel engines. Future work should focus on preventing knocking combustion and nitrogen oxide emissions in hydrogen-fueled diesel engines by adjusting the hydrogen inclusion rate in real time.     

缸内直接喷射汽油机的新技术

本文从燃油喷射系统、燃烧系统、混合气形成的基础理论研究、燃烧和排放等几方面介绍了汽油缸内直接喷射技术取得的新进展以及目前尚未解决的技术难题，指出排放问题将是决定缸内直喷汽油机发展的关键因素。     

A review of hydrogen usage in internal combustion engines (gasoline-Lpg-diesel) from combustion performance aspect

Demand for fossil fuels is increasing day by day with the increase in industrialization and energy demand in the world. For this reason, many countries are looking for alternative energy sources against this increasing energy demand. Hydrogen is an alternative fuel with high efficiency and superior properties. The development of hydrogen-powered vehicles in the transport sector is expected to reduce fuel consumption and air pollution from exhaust emissions. In this study, the use of hydrogen as a fuel in vehicles and the current experimental studies in the literature are examined and the results of using hydrogen as an additional fuel are investigated. The effects of hydrogen usage on engine performance and exhaust emissions as an additional fuel to internal combustion gasoline, diesel and LPG engines are explained. Depending on the amount of hydrogen added to the fuel system, the engine power and torque are increased at most on petrol engines, while they are decreased on LPG and diesel engines. In terms of chemical products, the emissions of harmful exhaust gases in gasoline and LPG engines are reduced, while some diesel engines increase nitrogen oxide levels. In addition, it is understood that there will be a positive effect on the environment, due to hydrogen usage in all engine types.     

Cold-start hydrocarbon emissions in port-injected gasoline engines

An analysis is made of the sources of the high engine-out hydrocarbon (HC) emissions during cold starting of port-injected gasoline engines. A cycle-by-cycle analysis of the different parameters, which affect engine-out HC emissions, is made during the startup process. The contribution of each cylinder of a four-stroke V6, 3.3 l production engine in the total HC emissions is investigated. The HC emissions were measured in the exhaust port using a fast response flame ionization detector (FID). The effect of the initial startup position of the piston and valves in the cycle on combustion and HC emissions is examined. The mass of fuel injected, burned and emitted was calculated for each of the first 120 cycles. Different approaches to reduce engine-out and tailpipe HC emissions during cold-start are discussed.     

柱塞泵性能的液力调整和喷油过程的分析

环保与人类生存的关系巳日趋紧密,而汽车尾气排放给环境带来严重威胁。由于柴油机应用极广,因此必须把改善它的燃烧和排放列为重要议题。柴油机喷油泵的供油特性及喷油过程对其燃烧和排放的影响很大,而出油阀结构的变化在改善这些性能上有独特效果,所以对出油阀进行改进,利用其缝隙在不同转速下对燃油的节流作用,实现对供油的优化调整,以达到节能和降低排放的目的。     

Role of mixture richness,spark and valve timing in hydrogen-fuelled engine performance and emission

The use of hydrogen as an engine fuel has a great potential for reducing exhaust emissions. With the exception of a little amount of hydrocarbon emissions originating from the lubricating oil, NO_x is the only pollutant emitted. The special properties of hydrogen compel much more study on hydrogen internal combustion engines (ICEs). Studying and analyzing the behavior of hydrogen ICE and its sensitivity to controllable parameters can help designers to have better understanding over hydrogen characteristics and its combustion in an ICE. In this paper, firstly a quasi-dimensional two-zone thermodynamic model of an SI hydrogen ICE is developed and validated by experimental data. The model is used as an engine simulator. Spark advance (SA), air to fuel ratio and valve timing are selected as the main effective and controllable parameters on engine emissions and performance characteristics. Valve timing parameter is defined as the intake and exhaust valves' lift, opening time and duration. Secondly, the effects of variation of the mentioned three parameters on emission and performance characteristics of the modeled engine are illustrated. Finally, the reasons of the engine behavior and characteristics under variations of these parameters are fully discussed.     

Influence of fuel properties and composition on NOx emissions from biodiesel powered diesel engines: A review

Biodiesel has proved to be an environment friendly alternative fuel for diesel engine because it can alleviate regulated and unregulated exhaust emissions. However, most researchers have observed a significant increase in NO_x emissions with biodiesel when compared to petrodiesel. The exact cause of this increase is still unclear; however, researchers believe that the fuel properties have been shown to effect the emissions of NO_x. The present work reviews the effect of fuel properties and composition on NO_x emissions from biodiesel fuelled engines. The paper is organised in three sections. The first section deals with the NO_x formation mechanisms. In the following section, the reasons for increased NO_x emissions of biodiesel fuel are discussed. After this, the influence of composition and fuel properties on NO_x emissions from biodiesel fuelled engines has been reviewed. Finally, some general conclusions concerning this problem are summarised and further researches are pointed out.     

Theoretical study of the effects of engine parameters on performance and emissions of a pilot ignited natural gas diesel engine

With the increasing concern regarding diesel vehicle emissions and the rising cost of the liquid diesel fuel as well, more conventional diesel engines internationally are pursuing the option of converting to use natural gas as a supplement for the conventional diesel fuel (dual fuel natural gas/diesel engines). The most common natural gas/diesel operating mode is referred to as the pilot ignited natural gas diesel engine (PINGDE) where most of the engine power output is provided by the gaseous fuel while a pilot amount of the liquid diesel fuel injected near the end of the compression stroke is used only as an ignition source of the gaseous fuel–air mixture. The specific engine operating mode, in comparison with conventional diesel fuel operation, suffers from low brake engine efficiency and high carbon monoxide (CO) emissions. In order to be examined the effect of increased air inlet temperature combined with increased pilot fuel quantity on performance and exhaust emissions of a PINGD engine, a theoretical investigation has been conducted by applying a comprehensive two-zone phenomenological model on a high-speed, pilot ignited, natural gas diesel engine located at the authors' laboratory. The main objectives of the present work are to record the variation of the relative impact each one of the above mentioned parameters has on performance and exhaust emissions and also to reveal the advantages and disadvantages each one of the proposed method. It becomes more necessary at high engine load conditions where the simultaneous increase of the specific engine parameters may lead to undesirable results with nitric oxide emissions.     

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.     

The comparison of engine performance and exhaust emission characteristics of sesame oil–diesel fuel mixture with diesel fuel in a direct injection diesel engine

The use of vegetable oils as a fuel in diesel engines causes some problems due to their high viscosity compared with conventional diesel fuel. Various techniques and methods are used to solve the problems resulting from high viscosity. One of these techniques is fuel blending. In this study, a blend of 50% sesame oil and 50% diesel fuel was used as an alternative fuel in a direct injection diesel engine. Engine performance and exhaust emissions were investigated and compared with the ordinary diesel fuel in a diesel engine. The experimental results show that the engine power and torque of the mixture of sesame oil–diesel fuel are close to the values obtained from diesel fuel and the amounts of exhaust emissions are lower than those of diesel fuel. Hence, it is seen that blend of sesame oil and diesel fuel can be used as an alternative fuel successfully in a diesel engine without any modification and also it is an environmental friendly fuel in terms of emission parameters.