【作者】 张焕宇；

【导师】 郝志勇；

【作者基本信息】 浙江大学 ， 动力机械及工程， 2013， 博士

【摘要】 高强化柴油机是今后发动机行业发展的主流,而发动机强化后所出现的可靠性问题与振动噪声问题也日益凸显,解决这些问题成为内燃机工作者面临的重要责任。本文结合数字化仿真技术与试验分析技术对多物理场耦合条件下的柴油机可靠性与NVH性能进行了深入地研究,取得了显著的成果。建立了柴油机结构件与冷却水套的流固耦合计算模型,采用沸腾传热模型详细分析了柴油机在高热负荷下的散热性能,并以水套传热计算的结果为边界条件计算了柴油机主要结构件的温度场与应力场。在此基础上,对发动机的冷却水套进行了优化设计,提高了冷却系统的散热性能,改善了结构件的应力分布状况。对发动机曲轴在复杂耦合边界条件下的疲劳强度性能进行了深入研究,建立了带液力润滑轴承模型的曲轴多体动力学耦合计算模型,通过对比不同轴承模型的计算结果证明了轴承热力学性能对轴系动力学性能预测的重要性。以热弹性液力润滑轴承的曲轴多体动力学模型为基础,研究了曲轴的动态应力分布与疲劳强度性能,结合曲轴疲劳强度试验证明了曲轴数字化分析模型在曲轴疲劳强度设计中的重要性。首次将波束形成法应用于识别发动机噪声源,大幅提高了噪声源识别的效率与准确性。通过建立运动件多体动力学与液力润滑轴承耦合的整机计算模型对发动机噪声性能进行了预测,并对通过发动机振动与噪声测量结果验证了计算模型的可靠性。以噪声预测结果为基础,通过模态追踪法、形貌优化法对发动机主要结构件的噪声性能进行了改进设计,大幅降低了结构件的辐射噪声。通过测量柴油机的缸内燃烧状态、表面振动加速度以及辐射噪声,研究了传统衰减曲线法在柴油机噪声预测上的应用,指出了其优缺点。通过对柴油机的燃烧噪声影响因素的全面细致研究,找到了影响柴油机燃烧噪声的关键因素。提出了一种全新的基于噪声变化量的燃烧噪声优化方法,采用单变量寻优,多变量最优组合验证的方法对全转速工况下柴油机的噪声性能进行了优化设计。在国内率先完成了通过电控调节降低柴油机燃烧噪声和整机噪声的研究,为今后内燃机燃烧噪声控制的研究提供了重要的理论依据和工程应用基础。更多还原

【Abstract】 Highly strengthened diesel engine is the mainstream of the engine industry future development; however, with the increasing of the enhanced performance of the engine, the reliability problems and NVH problems of strengthened engines are increasingly prominent. Engine NVH problems will seriously affect the durability and comfort of the vehicle. Therefore, the noise and vibration reduction work of strengthening the engines is received more and more attention. How to solve these problems becomes the important responsibility of internal combustion engine workers. Based on digital simulation techniques and experimental analysis techniques, this paper carried out a detailed research on the reliability and NVH performance for diesel engines under multi-physics coupling conditions, and achieved remarkable results.Fluid-solid coupling calculation model of diesel engine parts and water jacket was established. Using boiling heat transfer model, a detailed analysis was earned out for the thermal performance of diesel engine at high load transfer model. The temperature field and stress field of diesel engine parts were calculated with water jacket heat transfer results as boundary conditions. After that, the engine cooling water jacket was optimized; the cooling system thermal performance and the state of the structure stress distribution were improved.A detailed research was earned out on engine crankshaft fatigue strength performance under complex multi-physics coupling conditions. The crankshaft multi-body dynamics model was established coupled with hydraulic lubricating bearings calculation model, and by comparing with the different bearing calculation model results, the importance of thermodynamic properties in bearing dynamic performance prediction was proved. Based on thermal elastic hydrodynamic lubrication model and crankshaft bearing multi-body dynamics model, the dynamic stress distribution and fatigue strength of crankshaft were studied. Combined with the fatigue strength experiments, the importance of crankshaft digital analysis model in the fatigue strength of the crankshaft design was proved.The beamforming method was firstly used on noise source identification; this method significantly improves the efficiency and accuracy of the noise source identification. Coupled with multi-body dynamics model and bearings hydrodynamic lubricating model, the whole engine calculation model was established. Based on this model, the engine noise performance was predicted and verified by engine bench tests. On the basis of noise prediction, track by modal method and shape optimization method were used to improve the noise performance of the engine parts, the structural radiation noise was significantly reduced.By measuring the in cylinder of diesel engine combustion state and surface vibration acceleration and radiated noise, traditional attenuation curve method is studied on the diesel engine noise prediction application, and its advantages and disadvantages were pointed out. By comprehensive and detailed research on diesel engine combustion noise influence factors, the key factors that affect the diesel engine combustion noise were found. An entirely new combustion noise optimization method based on the noise changes was proposed. By single-variable optimization, multivariable optimal combination verification method, the optimization design was carried out for the combustion noise performance of a diesel engine. The studies on engine noise reduction in this dissertation took the lead in the combustion noise and whole engine noise reduction, provided important theoretical basis and engineering application foundation for the future internal combustion engine noise control study.更多还原