内燃机瞬态燃烧与热功转换过程在线辨识及分析的关键科学问题研究

It is a very difficult and yet to develop technology to diagnose the states and variation histories of the in-cylinder combustion and thermo-to-mechanical work conversion processes, as well as the correction of operational parameters real time in an IC engine under transient operation conditions. The two major obstacles are: 1. from the view point of on-line diagnosis of multiply parameters: there is no suitable approach yet developed which could meet the diagnostic frequency and measurement accuracy requirements at the same time; 2. for on-line correction of operational parameters: there exists no theoretic guidance with regard to how to correct due to lack of understanding to the fundamental inner-relationships between the in-cylinder processes and the operational parameters. To solve those issues, a new approach is proposed in this research, which is based on a hybrid method of dynamic signal measurements coupled with gas dynamics/thermodynamics process simulation in the engine system. Several key theoretic issues are to be solved to make the method on-line applicable: 1. selection and optimization of the mathematic solver among several differencing schemes of the governing equations, discrete and iteration methods, as well as the data coupling methods at the measurements/simulation boundary, to solve the controlling equations of the gas dynamics and thermodynamics processes in the engine system in order to meet the diagnostic frequency and measurement accuracy requirements at the same time; 2. revealing of the fundamental inner-relationships between engine operational and performance parameters under transient operational conditions, and establishment of common influencing trends as well as theoretic relationships, in order to create a theoretic foundation and to provide guidance for the judgment and correction of operational parameters on-line, to achieve favorable engine performances under transient operation conditions. The feasibility of the approach will be validated in an advanced automotive engine.

瞬变工况状态下内燃机的燃烧与热功转换过程状态和变化历程的在线辨识以及运行参数的实时调整是一个未解决的难题。 困难在于两个方面：1、从参数辨识的角度上：没有检测速度与精度能同时满足要求的方法；2、从参数控制的角度上：由于对诸运行参数的影响机理和共性规律的认识不深入从而缺乏参数调整、纠偏的理论依据。本研究提出一种基于动态压力传感器实测与气体动力学/热力学过程模-数耦合、联立求解的多参数同步辨识、分析方法，致力于解决该方法在线应用中的几个关键、共性理论问题：1、寻求快速、精准的气体动力学与热力学控制方程组的差分求解和模-数动态偶合方法，解决多参数同步、在线检测、辨识的时间尺度问题；2、在对大量数据进行深入分析的基础上，破解瞬变状态下运行参数对性能参数的影响机理、总结共性规律，为运行参数的在线辨识、评判以及纠偏控制技术提供理论依据。最终在一台先进车用内燃机上进行试验验证。

车用内燃机绝大部分时间工作在瞬变工况，其实际热效率与稳态台架性能水平相差较大。改善车用内燃机瞬变工况下热功转换效率是实现汽车节能环保最直接、有效的途径，对于实现汽车节能减排的目标意义深远。然而，瞬变工况下车用内燃机的燃烧与热功转换过程状态和变化历程的在线辨识以及运行参数的实时调整是一个尚未解决的难题。困难在于两个方面：（1）从参数辨识的角度上，没有检测速度与精度能同时满足要求的方法；（2）从参数控制的角度上，由于对诸运行参数的影响机理和共性规律的认识不够深入从而缺乏参数调整、纠偏的理论依据。.本项目提出了一种基于动态压力信号实测与气体动力学/热力学过程耦合、联立求解的多参数同步辨识方法，解决了该方法在线应用中的几个关键共性问题：（1）通过对比分析，寻求了一种快速精准的气体动力学与热力学控制方程组的差分求解和模-数动态耦合方法，解决了多参数同步、在线检测和辨识的时间尺度问题；（2）根据提出的内燃机瞬态性能在线检测方法的工作原理，开发了相应的软件应用技术平台，并且在整车道路循环试验中进行了验证，成功实现了对内燃机工作过程运行和状态参数按循环-循环进行检测，精度满足实机应用要求；（3）在对大量数据进行深入分析的基础上，破解了瞬变状态下运行参数对性能参数的影响机理、总结了大量的共性规律，为运行参数的在线辨识、评判以及纠偏控制技术提供理论依据；（4）将检测得到的整车道路循环工况下的内燃机瞬态性能数据与其相应的稳态性能结果进行对比分析，得出稳态和瞬态工况下缸内燃烧和热功转换性能的差异及其影响因素。.通过本项目的研究，在内燃机瞬态工作过程在线模拟计算、数-模信号无缝链接与实时传输方法等方面取得突破；开发的内燃机瞬态性能在线检测技术填补了现有技术不能对内燃机瞬变工况下运行和性能参数在线、连续检测的空白。上述研究成果为改善车用内燃机标定策略、提升瞬变工况下内燃机实际性能提供理论依据和数据支撑。