车用柴油机性能的共性规律研究及瞬态工况测评

发布时间：2018-08-18 10:11

【摘要】：柴油机相较于汽油机,具有有效热效率更高、扭矩特性更好、二氧化碳排放更低的优势,因此,乘用车柴油化是实现汽车节能减排最有效的技术路线之一。概念设计的结果决定了新品柴油机的开发方向与未来的市场竞争力。由于车用柴油机引入的技术日趋复杂,影响其性能的设计以及运行参数从而也在不断增多,且各参数对于柴油机动力性、经济性、排放性的影响方式和程度不尽相同,部分参数之间还互为关联、相互影响、有些甚至互相矛盾,因此在新品柴油机的开发过程中,待优化变量的维度巨大,参数的优化将耗费大量的人力物力。另外,作为移动式内燃动力之一,车用柴油机的性能开发与运行参数的优化标定,通常是在稳态试验台上完成的,而其实际使用工况又大部分是瞬变工况,瞬变工况性能决定了移动式内燃动力的实际使用性能。因此,对车用柴油机实际使用工况下的燃烧过程的状态辨识及其影响参数的提炼、影响方式的共性规律总结及相应智能控制及纠偏技术的应用,也是新品柴油动力车辆开发过程中为达到节能减排目标所急需解决的难点问题之一。本论文致力于攻克以上几个方面的关键科学问题。主要研究内容和研究结果总结如下:(1)采用先进的AVL发动机台架测试系统,对四款先进的车用柴油机开展了详细的试验研究,获得了较为全面的柴油机运行参数和性能参数MAP。通过对试验数据的二次开发,分析、总结得到了不同类型柴油机性能参数的变化规律和关键影响因素。根据柴油机的实际工作情况,修正了IMEP的计算式,提出了进气参数K和缸内稀释参数L的概念,破解了稳态工况下柴油机动力性(IMEP)、排放性(NOx及PM)、燃烧性能参数(燃烧效率、燃烧持续期、燃烧品质参数)等随转速、负荷、过量空气系数、EGR等变化的共性规律。(2)分析了影响柴油机热功转换过程的关键参数,并导出了柴油机燃烧效率随过量空气系数变化的共性规律。将本研究团队提出的有效膨胀效率的概念拓展到柴油机缸内热功转换效率的量化方程上,并在四台先进柴油机上进行了验证。结果表明:该量化方程计算得到的柴油机指示热效率与试验值匹配程度很高,四台柴油机的偏差均在5%以内。通过建立柴油机的指示热效率与过量空气系数、燃烧效率、绝热效率及有效膨胀效率之间的量化关系,进一步细化了柴油机动力性及经济性的控制方程,拓展了同类、不同排量的柴油机之间进行参数移植的范围。(3)采用“瞬时实测信号+稳态插值仿真”的方法,解决了瞬变工况下柴油机扭矩及瞬时油耗率由于传感器的安装困难导致的难以在线、精准检测的问题,并与实测结果进行了对比验证,实现了对柴油机瞬变过程多参数的同步、连续、精准测量,为柴油机变工况下性能的检测、评价与分析提供了一种简便但精准的方法。(4)运用以上开发的柴油机瞬变工况下运行及性能参数的连续检测方法,针对一台车用2.8T增压柴油机,系统地开展了稳态工况下的万有特性试验,以及瞬变负荷试验研究。通过实测信号与软件耦合仿真相结合,展示了相同工况下,稳态与瞬态过程性能表现的异同点,找出了导致两者产生性能差异的关键影响参数,并基于以上总结的柴油机性能与设计及运行参数之间内在联系的共性规律及量化方程,评价了柴油机变工况下缸内燃烧及热功转换过程的优劣,为标定参数的纠偏提供了方向。
[Abstract]:Compared with gasoline engine, diesel engine has the advantages of higher effective thermal efficiency, better torque characteristics and lower carbon dioxide emissions. Therefore, passenger vehicle diesel is one of the most effective technical routes to achieve energy saving and emission reduction. The technology introduced by the engine is becoming more and more complicated, and the design and operation parameters that affect the performance of the engine are also increasing, and the influence of the parameters on the power, economy and emission of the diesel engine is not the same, and some parameters are correlated, influenced and even contradictory with each other. Therefore, the new diesel engine has been developed. In addition, as one of the mobile internal combustion powers, the performance development and calibration of automotive diesel engine are usually completed on the steady-state test bench, and the actual operating conditions are mostly transient conditions, and the transient operating conditions are determined. The actual performance of the mobile diesel engine is determined. Therefore, the identification of the combustion process and the extraction of its influencing parameters, the generality of the influencing modes and the application of the corresponding intelligent control and correction technology are also important for energy saving and emission reduction in the development of new diesel-powered vehicles. The main research contents and results are summarized as follows: (1) Using advanced AVL engine bench test system, a detailed experimental study on four advanced automotive diesel engines has been carried out and a more comprehensive diesel engine has been obtained. Operating parameters and performance parameters MAP. Through the secondary development of test data, the changing rules and key influencing factors of performance parameters of different types of diesel engines are summarized. According to the actual working conditions of diesel engines, the calculation formula of IMEP is revised, the concepts of intake parameter K and cylinder dilution parameter L are put forward, and the steady-state working conditions are cracked. (2) The key parameters affecting the thermal power conversion process of diesel engine are analyzed and the combustion efficiency versus excess air coefficient is derived. The concept of effective expansion efficiency proposed by our research team is extended to the quantitative equation of thermal power conversion efficiency in cylinder of diesel engine and verified on four advanced diesel engines. The deviation is less than 5%. By establishing the quantitative relationship between the indicated thermal efficiency and excess air coefficient, combustion efficiency, adiabatic efficiency and effective expansion efficiency, the governing equations of power and economy of diesel engines are further refined, and the range of parameter transplantation between similar and different displacement diesel engines is extended. The method of "instantaneous measured signal + steady-state interpolation simulation" solves the problem that the torque and instantaneous fuel consumption of diesel engine are difficult to be measured on-line and accurately because of the difficulty in installing sensors under instantaneous working conditions. The method is verified by comparing with the measured results and realizes the synchronous, continuous and accurate measurement of multi-parameters in the transient process of diesel engine. A simple but accurate method for testing, evaluating and analyzing the performance of a diesel engine under off-design conditions is provided. (4) Based on the continuous testing method developed above, the universal characteristic test and transient load test of a 2.8T Turbocharged Automotive Diesel Engine under steady-state conditions are carried out systematically. Experiments show the similarities and differences of performance between steady and transient processes under the same operating conditions through the combination of measured signals and software coupled simulation. The key parameters that lead to the performance differences between the two processes are found out. Based on the similarities and quantifications of the internal relations between diesel engine performance and design and operation parameters summarized above This paper evaluates the combustion and thermal power conversion process of diesel engine under off-design conditions, and provides a direction for calibrating parameters.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：U464.172

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