| Energy and environment are the most concerned issues to human beings recently, they are not only the material basis of survival and development to human beings, but also the important strategic problem to China and other countries of the world.The continuing shortage of oil resources and the deteriorating environment worldwide is a huge problem that humanity faced this century, while the internal combustion engine is one of the main sources of the contaminants in the oil consumption sources and atmospheric environment.To our country, the situation of the energy and environmental issues are more serious and urgent.Exploring the development of new clean alternative fuel alternative to petroleum-based fuel is the current focus of attention of the world. In recent years, the low calorific value gas fuel (or referred to as low-quality gas fuel) is being more and more attention of the governments of the world, corporate and university research units; coal bed gas is a kind of typical low calorific value gas, and our country’s production and consumption of coal is huge;the energy structure focusing on coal,deciding our country must attach importance to the development and utilization of coal bed gas. On the other hand,the direct injection technology of gasoline engine has been rapid development in recent years.The combination of direct injection technology and low calorific value gas fuel engine,can effectively improve the volumetric efficiency of the engine and improve combustion characteristics, and extend the lean burn limit and reduce harmful emissions.This study was supported by National Natural Science Foundation of China (50906003).By ransforming the single-cylinder diesel engine into a direct injection gas fuel engines,and carried out the performance tests of the engine burning low calorific value gas fuel. Analyzing the test data,draw the following conclusions:(1) Under various injection pressure, with the increase of load, the effective rate of fuel consumption is reduced ceaselessly, Under the same injection pressure, the volume fractions of nitrogen in fuel have little effect on effective fuel consumption rate. When the load is same, the increase of nitrogen volume fractions can effectively reduce exhaust temperature and NOx emission concentration.(2) The ignition advance angle have an significant influence on engine performance, there is an range of ignition advance angle,that makes the effective power of the engine maximum, the ignition advance angle have an significant influence on engine emissions performance,especially NOx.When the injection pressure is higher, smaller ignition advance angle should be adopted, to control the emission of NOx concentration; while the injection pressure is lower, the NOx emissions concentration keeps low overall, at this time the dynamic and economy of engine should be considered in the first place.(3) Tn a certain range, the injection timing has little effect on engine power and effective fuel consumption rate, in this experiment conditions,the range of injection starting angle is80～160°CA ATDC,and the NOx, HC, CO emission concentration change little.Under various injection pressures,the injection timing has a same influence on engine performance,indicating that when the injection pressure changes in a certain range, does not need to adjust injection timing of engine.(4) The excess air coefficient has an obvious effect on the effective power and the economic of the engine.Increase the injection pressure can improve the excess air coefficient which makes the effective power of the engine maximum.Under different injection pressure, and when the excessive air coefficient makes the effective power of the engine maximum, NOx emissions are low, that is to say,there is no need to sacrifice the dynamic and economy of engine, can obtain lower NOx emission. |
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