| Today, environmental protection and the conservation of natural resources are of greater concern, and the need to develop a clean and low fuel-consuming vehicle is increasingly important. Hydrogen is considered the most promising alternative energy vehicle because it is clean, efficient and renewable, and currently the most feasible application of hydrogen in the engine is through the implementation of HCNG as a fuel. Idle condition is one of the engine’s most important conditions, the engine’s performance characteristics, fuel economy and emission characteristics are greatly affected by the idle performance. This thesis based on the government‘863’project, focuses on examining the performance and emissions characteristics of both pure hydrogen and HCNG on a spark-ignition engine at idle conditions through both experimental and simulation methods.In this paper, the experimental study consists of the following three main issues:(1) Pure hydrogen was used at idle conditions: by analyzing the emissions, economy, and performance, the optimal combination of using different air-fuel ratios and ignition timings are determined; (2) Different hydrogen ratios at idle conditions: by analyzing the emissions, economy, and performance, the optimal combination of using different air-fuel ratios and ignition timings are determined (3) Different hydrogen ratios at wide close throttle: by analyzing the emissions, economy, and performance, the optimal combination of using different air-fuel ratios and ignition timings are determined.The simulation involved in this thesis mainly based on the AVL Boost software. Boost is used to conduct a one-dimensional simulation of the overall performance of the engine using both HCNG and hydrogen. Through one-dimensional simulation the effects of compression ratio and valve phasing on engine overall performance is analyzed. The objective is to use engine simulation to predict the performance and to resolve problems that may exist such as reduction of power while using a high hydrogen ratio and fuel prematurely entering the exhaust pipe and exploding while using a high hydrogen ratio. The simulation results show that for a compression ratio of 12, the optimal performance is achieved. When using a high hydrogen ratio, the fuel may prematurely enter the exhaust pipe and explode which is due to the large valve overlap angle, therefore it is necessary to adjust the valve timing. When the overlap angle is reduced, the indicated mean effective pressure will drop slightly, but the actual pressure will remain unchanged, and the explosion will be controlled. In order to ensure safety when using pure hydrogen, an appropriate valve overlap is betwen 5-10 degrees. |
