【作者】 王宇；

【导师】 马凡华；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2009， 硕士

【摘要】 天然气掺氢燃料(HCNG),是将天然气和氢气按一定比例混合得到的一种新型车用燃料,它不仅是一种满足汽车行业的发展方向“节能减排”的替代燃料,也是从传统汽车向氢能汽车过渡的最具可行的方案。本论文的主要工作内容为通过试验研究与模拟计算的方法来对火花点火HCNG发动机的性能及工作过程进行研究和分析。前期的研究结果表明:掺氢对CNG发动机性能的改善主要原因在于其对CNG发动机稀燃能力的提高,因此本文通过试验主要研究分析了以下三个问题:(1)掺氢对CNG发动机稀燃能力提高即降低稀燃循环变动的原因;(2)掺氢可以在多大程度上提高CNG发动机的稀燃能力;(3)掺氢对CNG发动机经济性、排放性等综合性能带来的影响。由于在研究过程中需要从燃烧角度分析试验所用发动机的缸内压力数据,因此本文也发展了通过HCNG发动机缸压数据计算燃烧放热率的双区热力学模型。在数值模拟计算研究中,主要借助了AVL Boost和Fire软件,其中Boost软件用于HCNG发动机整机性能的一维模拟而Fire软件则用于较详细的分析HCNG发动机进气和燃烧过程。本文通过一维模拟计算分析了掺氢比、发动机负荷、压缩比和配气相位对HCNG发动机综合性能的影响。通过三维模拟计算分析了掺氢对缸内燃烧速度、温度及NOx排放的影响,并研究了进气和压缩过程中进气道和缸内的速度场及其对燃烧过程的影响。更多还原

【Abstract】 Hydrogen enriched compressed natural gas (HCNG) is a new type of fuel for ground vehicle applications which can be achieved by blending natural gas with hydrogen. HCNG is not only an alternative vehicular fuel that accords with the trend of“energy saving and emission reduction”in the automotive industry but also serves as a feasible approach to fasten the transition from traditional vehicles to vehicles powered by hydrogen. The main work of this thesis is to examine the performance and working process of a spark-ignition HCNG through both experimental and simulation methods.According to previous results, the advantages caused by hydrogen addition mainly are based on hydrogen’s ability to improve the lean burn capability of CNG engines. So in the experimental analysis, much effort has been given to elucidate the following three questions: (1) why hydrogen can improve engine’s lean burn capability-that is why hydrogen can reduce the cycle-by-cycle variations of lean burn CNG engines; (2) to what extent can hydrogen addition improve the lean burn capability of CNG engines; (3) the effects of hydrogen addition on the overall performance of CNG engines, including fuel efficiency and emission characterisitcs. Due to the need to analyze the experimentally obtained cylinder pressure data from a combustion point of view, this theiss also include the work of develop a computer program to derive the burn rate data from the cylinder pressure profile through a two-zone thermodynamic model.The simulation work involved in this thesis mainly based on the AVL Boost and Fire software. Boost is used to conduct a one-dimensional simulation of the overall performance while Fire is employed to do a more detailed analysis of the intake and combustion process of the HCNG engine. Through one-dimensional simulation the effects of hydrogen blending ratio, engine load, compression ratio and valve phasing on engine overall performance is analyzed. And by employing multi-dimensional simulation the effects of hydrogen addition on the combustion rate, cylinder temperature and NOx formation is analyzed. The flow patter in the intake port and the cylinder during the intake and compression process are also examined.更多还原