【作者】 汤东；

【导师】 罗福强；

【作者基本信息】 江苏大学 ， 动力机械及工程， 2007， 博士

【摘要】 近年来发动机燃用气体燃料已成为改善内燃机经济性及降低排放的重要研究方向之一,柴油引燃的双燃料发动机由柴油机改装而来,具有高效率、低排放的优势,应用越来越广泛。由气化炉热解气化各种农林废弃物产生的生物制气是一种优良的发动机替代燃料,对缓解能源紧张状况、减少焚烧生物质产生的二次污染等方面具有较好的综合效益和广阔的应用前景。简述了双燃料发动机的开发现状和技术对策;综述了生物质能源的发展和研究现状以及压燃式双燃料发动机燃烧模型的进展。在前人研究的基础上从理论和实验研究两方面对生物制气-柴油双燃料发动机进行了较为深入的探讨,为生物质能源在双燃料发动机上的应用及发展提供了科学的依据。将一台单缸直喷柴油机改装为柴油引燃的生物制气-柴油双燃料发动机,既可纯柴油模式运行,也可以双燃料模式运行。对比分析了发动机运行于两种模式下的万有特性、燃烧特性和比排放性能。分析了负荷、转速、供油提前角等参数对柴油机及双燃料发动机燃烧过程的影响。结果表明:双燃料发动机的燃烧始点落后于柴油机;除低速大负荷外,最高燃烧压力、最大燃烧压力升高率均低于柴油机,最高燃烧压力与最大燃烧压力升高率对应相位均滞后于柴油机;双燃料发动机的后燃较为严重,排气温度较高,烟度稍大。双燃料发动机的NO_x排放量较柴油机显著降低,但CO和HC的排放量明显增加。从时域和频域两个方面对生物制气—柴油双燃料发动机的燃烧噪声进行综合评价,并计算出燃烧总声压级。与柴油发动机进行对比分析,研究了不同的供油提前角、负荷和转速对燃烧噪声的影响。结果表明,在相同转速下燃烧噪声随负荷变大而变大;在相同负荷下供油提前角变大其燃烧噪声变大,燃用纯柴油比燃用生物制气混合气的燃烧噪声大。根据双燃料发动机燃烧的特点,建立了由实测示功图计算双燃料发动机燃烧放热规律的多区计算模型,并将其和传统柴油机模型进行了计算结果对比。计算分析表明,生物制气-柴油双燃料发动机的最大放热率高于柴油机,燃烧延迟,后燃较严重。与传统模型相比,新模型与双燃料发动机实际燃烧过程更为吻合,可以更好地对双燃料发动机的燃烧过程进行诊断分析。通过对双燃料发动机燃烧过程的深入分析,建立了基于湍流火焰面分形理论的双燃料发动机现象学准维燃烧模型,包括滞燃期子模型,喷雾卷吸子模型,燃烧和火焰传播子模型,燃烧化学反应子模型,传热及NO_x排放形成子模型等,并运用该模型对生物制气-柴油双燃料发动机进行了燃烧过程的模拟,预测双燃料发动机的气缸压力及NO_x排放等参数,计算结果与实验结果有良好的一致性。更多还原

【Abstract】 During recent years the use of gaseous fuel in internal combustion engine is becoming an important research aspect for the improvement of fuel consumption and reduction of emission. The dual fuel engine modified from diesel engine with pilot diesel fuel ignition is widely used due to its high efficiency and low emissions. Biogas produced by gasification oven from biomass materials is a kind of good alternative fuel for the engines. It is becoming a most important resource to solve the shortage of energy and reduce the second pollution from the burning of biomass materials. The biogas is used more and more widely in engine. The current situation on development and technical strategy of dual fuel engine are briefly discussed. The development and the current situation of biomass energy and the evolvement of combustion model of compression ignition dual fuel engine are summarized. The dual fuel engine is discussed by theory and experiment on the basis research of predecessors. Scientific foundation for the utilizing and development trend of biomass energy sources is introduced.A biogas—diesel dual fuel engine ignited by the pilot diesel fuel has been modified from a single cylinder, direct injection diesel engine. The dual fuel engine can operate by normal diesel fuel (no gas was added) or dual fuel. The characteristics map of fuel consumption, combustion parameters and specific emissions of diesel engine and dual-fuel engine are analysed. The effects of parameters such as load, engine speed and fuel supply advance angle on combustion process are analysed. The results show that compared with diesel engine, the ignition timing of dual fuel engine is delayed.The maximum combustion pressure and maximum combustion pressure rise are lower and their corresponding phases are delayed except at low speed and high load conditions. The after combustion period is longer. The NO_x emission of dual fuel engine compared to the diesel engine decrease remarkably, but the HC and CO emission increase obviously.The combustion noise of the biogas diesel dual-fuel engine is comprehensively evaluated in time region and frequency region. The total combustion sound pressure level is caculated. The data of dual fuel engine are compared with those of diesel engine. The effect of the different fuel supply advance angle and load and speed on the combustion process are studied. The results show that the combustion noise is larger with the increasing of load. The combustion noise is larger with the increasing of fuel supply advance angle. The combustion noise of diesel engine is larger than that of dual fuel engine.According to the combustion characteristics of dual-fuel engine, a new multi-zone combustion and heat release model has been developed to calculate the combustion heat release rate based on the measured cylinder pressure. This new model is applied to the biogas-diesel dual fuel engine and compared with the conventional diesel calculation model. The research results show that the peak heat release rate of dual fuel engine is larger than that of the diesel engine. However the total combustion period is delayed. Compared with the conventional calculation model, the new model agrees well with the experimental results.On the basis of experimental data and theory analysis, a universal combustion model was developed to predict the performance of the dual fuel engine. The new model is based on the fractal nature of turbulent flames, including ignition delay model, fuel spray and air entrainment model, flame propagation model, combustion chemical reaction model, heat transfer model and the NO_x emission model. This new model is applied to the biogas-diesel dual fuel engine to predict the characteristics of the engine. The simulation results show that the model has good precision compared with the experimental data.更多还原