Study On The Influence Of Hydrogen Blend On The Combustion Process And Performance Of CNG Engine

With the rapid development of the automobile industry, vehicles have taken up a large proportion of fossil fuel consumption year by year. The exhaust of vehicles is producing increasingly much damage to the environment. Developing alternative fuels is an important way to reduce the demands for petroleum and to alleviate the problems of environmental pollution. Natural gas is becoming widely used as its substantial deposits and environmental protection. But it has shortcomings, low burning velocity and low calorific value, which will result in low efficiency and low power performance. Hydrogen is an ideal fuel to make up the disadvantages of natural gas as its high burning velocity and high calorific value. The influences of blending hydrogen on the in-cylinder combustion process, economy and emission performance of natural gas engine were studied to explore the essence of how the combustion characteristic parameters change with the blend-ratio of hydrogen. Based on these rules, a standard numerical model for Compressed natural gas blended with hydrogen(HCNG) engine was built to predict the performance of other HCNG engines.In this paper, a high compression ratio, turbo charged, premixed natural gas engine was refitted to inject hydrogen and natural gas. Then tests were conducted to obtain performance parameters, operation parameters and combustion parameters, based on which the in-cylinder combustion process and performance parameters were studied, especially the key combustion parameters: the changing trends of 50% combustion location and 10%-90% burn duration with energy ratio of hydrogen. Based on the analyses above, the influences of hydrogen blending on the economy performance, NOX, HC, CO2 emissions were studied. In the end, a standard numerical model for HCNG engine was built to predict the performance of other HCNG engines.After studying on the HCNG engine, it is concluded that: In-cylinder combustion process was boosted with the increasing of hydrogen’s energy ratio. 0-10% burn duration, 10%-90% burn duration gets shorter with the increasing of hydrogen’s energy ratio, and 0-10% burn duration is more sensitive to the hydrogen’s energy ratio, that is to say the hydrogen’s impact on the combustion process of natural gas engine is primarily on the initial stage. As a result, 50% combustion location becomes earlier as the hydrogen’s energy ratio increases; the peak pressure and the maximum pressure rise rate increases and comes more and more earlier with the increasing of hydrogen’s energy ratio; the cyclic variation of combustion process also reduces with the increasing of hydrogen’s energy ratio; the equivalent fuel consumption rate decreases, NOX increases, HC and CO2 decreases with the increasing of hydrogen’s energy ratio. All the influences of hydrogen on these parameters weaken with the increase of speed and load. The standard numerical model for HCNG engine based on these rules has a high accuracy in predicting the performance of other HCNG engines.