Slow diffusion of LPG vehicles in China—Lessons from Shanghai,Guangzhou and Hong Kong

Compared with other alternative fuel vehicles (AFV), LPG vehicles (LPGV) have lower economic and technological barriers, leading to its faster growth in some developing countries in recent years. By means of regulation, Shanghai managed to have nearly all taxis converted to LPGV in the early 2000s, and all taxis and 80% of buses in Guangzhou are LPGV. Nevertheless, LPGV diffusion in China (excluding Hong Kong) has been slow and even showing signs of retreating. By 2008, less than 5% of taxis in Shanghai were LPGV. This paper looks into the problem by comparing the LPGV development of Shanghai, Guangzhou versus that of Hong Kong where the LPGV development seems to be running well. The obstacles of LPGV development in China include a lack of policy coherence between the central and local governments; insufficient price advantage of Autogas; not enough fueling stations; and high maintenance costs due to immature technology and poor quality control. Bi-fuel system has further magnified the problems in China. In order to facilitate the use of alternative fuel, efforts should be made to increase the number of AFVs as well as to ensure the availability and price-competitiveness of the alternative fuel concerned.     

Dual-injection: The flexible,bi-fuel concept for spark-ignition engines fuelled with various gasoline and biofuel blends

Dual-injection strategies in spark-ignition engines allow the in-cylinder blending of two different fuels at any blend ratio, when simultaneously combining port fuel injection (PFI) and direct-injection (DI). Either fuel can be used as the main fuel, depending on the engine demand and the fuel availability. This paper presents the preliminary investigation of such a flexible, bi-fuel concept using a single cylinder spark-ignition research engine. Gasoline has been used as the PFI fuel, while various mass fractions of gasoline, ethanol and 2,5-dimethylfuran (DMF) have been used in DI. The control of the excess air ratio during the in-cylinder mixing of two different fuels was realized using the cross-over theory of the carbon monoxide and oxygen emissions concentrations. The dual-injection results showed how the volumetric air flow rate, total input energy and indicated mean effective pressure (IMEP) increases with deceasing PFI mass fraction, regardless of the DI fuel. The indicated efficiency increases when using any ethanol fraction in DI and results in higher combustion and fuel conversion efficiencies compared to gasoline. Increasing the DMF mass fraction in DI reduces the combustion duration more significantly than with increased fractions of ethanol or gasoline in DI. The hydrocarbon (HC), oxides of nitrogen (NO_x) and carbon dioxide (CO₂) emissions mostly reduce when using any gasoline or ethanol fraction in DI. When using DMF, the HC emissions reduce, but the NO_x and CO₂ emissions increase.     

Conversion of a commercial gasoline vehicle to run bi-fuel (hydrogen-gasoline)

Bi-fuel internal combustion engine vehicles allowing the operation with gasoline or diesel and hydrogen have great potential for speeding up the introduction of hydrogen in the transport sector. This would also contribute to alleviate the problem of urban air pollution. In this work, the modifications carried out to convert a Volkswagen Polo 1.4 into a bi-fuel (hydrogen-gasoline) car are described. Changes included the incorporation of a storage system based on compressed hydrogen, a machined intake manifold with a low-pressure accumulator where the hydrogen injectors were assembled, a new electronic control unit managing operation on hydrogen and an electrical junction box to control the change from a fuel to another. Change of fuel is very simple and does not require stopping the car. Road tests with hydrogen fuel gave a maximum speed of 125 km/h and an estimated consumption of 1 kg of hydrogen per 100 km at an average speed of 90 km/h. Vehicle conversion to bi-fuel operation is technically feasible and cheap.     

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机动船大多数以汽油、柴油为燃料，不仅消耗了大量汽油和柴油，而且发动机废气还加剧了江河湖泊流域的大气污染。因此以天然气替代汽油和柴油，缓解液体燃料的紧张状况，减少环境污染是我国一项长期的能源政策和环境保护政策。为此，提出了天然气—汽油和天然气—柴油双燃料机动船及其船运CNG充气装置等配套技术方案，并对采用该系统的社会、经济效益及其实施方案进行了详细的分析研究。结果表明：采用天然气双燃料机动船及船运CNG充气装置在技术上可行；可节约燃料30%～50%，经济性较好；排放废气中有害物质大幅度减少，环保效果明显；值得推广与应用。     

发动机一发电机组水电阻吸能装置电阻计算研究

在以内燃机为原动机的电传动系统研究中，要研究动力系统的特性必须对其加载，因此寻找一种吸收系统电能的方法非常重要。从研究电解液导电机理出发，分析了用水电阻吸收电能的机理和影响因素，电极和电解液构成孤立的耗能系统，可以用场理论进行计算，在此基础上提出了用能量理论计算水电阻的方法，并以该理论为指导设计了水电阻试验台，通过试验对研究结果进行了验证。     

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.     

柴油发电机房通风排烟系统设计

分析了周围环境对柴油发电机组功率的影响;介绍了柴油发电机房通风排烟系统的设计及注意事项;并给出了某型号发电机组的相关数据,供同行在今后的设计中参考。     

Conversion of a gasoline engine-generator set to a bi-fuel (hydrogen/gasoline) electronic fuel-injected power unit

The modifications performed to convert a gasoline carbureted engine-generator set to a bi-fuel (hydrogen/gasoline) electronic fuel-injected power unit are described. Main changes affected the gasoline and gas injectors, the injector seats on the existing inlet manifold, camshaft and crankshaft wheels with their corresponding Hall sensors, throttle position and oil temperature sensors as well as the electronic management unit. When working on gasoline, the engine-generator set was able to provide up to 8 kW of continuous electric power (10 kW peak power), whereas working on hydrogen it provided up to 5 kW of electric power at an engine speed of 3000 rpm. The air-to-fuel equivalence ratio (λ) was adjusted to stoichiometric (λ = 1) for gasoline. In contrast, when using hydrogen the engine worked ultra-lean (λ = 3) in the absence of connected electric load and richer as the load increased. Comparisons of the fuel consumptions and pollutant emissions running on gasoline and hydrogen were performed at the same engine speed and electric loads between 1 and 5 kW. The specific fuel consumption was much lower with the engine running on hydrogen than on gasoline. At 5 kW of load up to 26% of thermal efficiency was reached with hydrogen whereas only 20% was achieved with the engine running on gasoline. Regarding the NO_x emissions, they were low, of the order of 30 ppm for loads below 4 kW for the engine-generator set working on hydrogen. The bi-fuel engine is very reliable and the required modifications can be performed without excessive difficulties thus allowing taking advantage of the well-established existing fabrication processes of internal combustion engines looking to speed up the implementation of the energetic uses of hydrogen.     

Numerical analysis of performance and emissions behavior of a bi-fuel engine with compressed natural gas enriched with hydrogen using variable compression ratio strategy

The increase in the compression ratio reduces the fuel consumption and improves the performance. These effects of compression ratio could be observed in all of the engines, such as compression or spark ignition engines. Moreover, due to the compression ratio constraint based on the knocking phenomenon in spark ignition engines, there will always be an optimal compression ratio, which is one of the most fundamental factors in engine design. The optimum compression ratio could be achieved depending on the type of fuel, but in the case of bi-fuel engines, since the nature of each fuel is different, the design must be relatively optimal for both fuels. In this work, by using the VCR (variable compression ratio) strategy, the bi-fuel EF7 engine performance, combustion, and emissions were investigated in different compression ratios when the engine uses gasoline or HCNG (hydrogen enriched compressed natural gas) as fuel. The results revealed that by changing the compression ratio from 11.05 (actual compression ratio of engine) to 11.80 in HCNG mode, an increase of 13% in power could be achieved. Also CO formation, at the compression ratio of 11.80, was slightly lower (7%) than the compression ratio of 11.05. In addition, by reducing the compression ratio from 11.05 to 10.50 in gasoline mode, there was a significant increase in emissions; that was 44% for the NO_x and 16% for the CO, which could be one of the limiting factors of the advance in spark timing. Moreover, due to the VCR strategy and the significant optimization of the compression ratio, the combinatory method of VCR – HCNG can be used as an effective method for the bi-fuel engines in order to improve the performance and reduce emissions.     

Impact of variable valve timing on power,emissions and backfire of a bi-fuel hydrogen/gasoline engine

Hydrogen-fueled internal combustion engines are a possible solution to make transportation more ecological. Apart from difficulties in production and storage of hydrogen, there are three major bottlenecks in the operation of hydrogen-powered engines: reaching a high power output, reducing NO_x emissions at high loads and avoiding backfire. This paper presents an experimental study of the influence of continuously variable valve timing of the intake valves on these bottlenecks. Measurements were performed on a four-cylinder engine that can run on gasoline as well as on hydrogen. The measurements on hydrogen are compared to those on gasoline. For hydrogen, the effects of the cam phasing were investigated at wide open throttle, where load is controlled by the quality of the mixture (equivalence ratio) as well as in throttled mode, where load is defined by the quantity of mixture.