摘 要

本文设计一种天然气-柴油双燃料发动机的压力自适应活塞（PRP），通过其压力自适应性解决双燃料发动机在天然气模式下容易产生爆震、限制压缩比取得很高以及部分负荷和柴油模式下经济性不如柴油机的问题。压力自适应活塞通过实现高压缩比有助于改善低负荷下的燃油消耗率，提高燃油经济性；通过自身形变增强高负荷下的抗爆性。研究以压力自适应活塞为研究对象，应用迭代耦合的方法同时完成活塞动力学仿真和缸内工作过程仿真结果，利用指示指标对结果进行分析，评价其经济性和抗爆性。

通过对原型机在GT-POWER上进行建模与仿真，得到原型机的指示指标，定量分析部分负荷工况下损失构成，说明提高压缩比是部分负荷下提高发动机动力经济性的有效途径。

对原型机活塞头部进行重新设计，在活塞头与活塞裙之间设计出一个空腔放置压力自适应机构。该机构由碟簧以及其他附属机构组成。根据原型机的基本参数以及仿真结果，查阅相关资料，设计一种非标准尺寸的碟簧,通过采用复合组合的形式,以满足高负载、小变形以及耐高温的缸内条件，并对整个活塞进行设计，用Pro/E画出设计图。

利用动力学仿真软件Adams对压力自适应活塞建模，将Adams仿真结果与GT-POWER相互迭代的方法同时进行动力学和发动机性能的仿真。通过多次迭代耦合逐渐逼近平衡状态下燃烧室内的工作情况，最终同时得到缸内工作过程仿真结果和活塞动力学仿真结果。

通过对缸内燃烧过程的分析,对发动机的性能作出评价。利用原型机与PRP机指示指标的对比评定低负荷时及柴油模式下的燃油经济性以及在高负荷时发动机对抑制天然气模式下产生爆震的效果。

将最终结果与原型机ACD320进行比较，利用性能评价指标得出结论：（1）说明了PRP试验机在低负荷下的动力性、经济性得到大大提高，天然气模式下燃油消耗率最大可减少2.5%，柴油模式下燃油消耗率最多可减少4%；（2）在满负荷下PRP试验机的抗爆性也得到验证，在提高了压缩比的情况下，缸内温度、压力升高率与原型机基本一致，仍然处在可控范围内，没有出现爆震倾向。

关键词：双燃料发动机;碟形弹簧;压力自适应活塞;迭代耦合;经济性;抗爆性

Abstract

This paper designs a pressure-reactive piston (PRP) for a natural gas-diesel dual-fuel engine that solves the problems that double-fuel engine in natural gas mode was easy to knock and was limited in a high compression ratio by its pressure adaptability, and in a partial load and diesel mode, the economy was not as good as the diesel engine. Pressure reactive piston reduces the fuel consumption rate, improves fuel economy in the low load through the realization of high compression ratio; it also can enhance the anti-explosive in high load through its own deformation. In this paper, the reactive piston was used as the research object, and the simulation results of the piston dynamics and the working process of the cylinder were completed by the iterative coupling method. The results were analyzed by the instruction index to evaluate the economy and the anti-explosive.

Through the modeling and simulation of the prototype on the GT-POWER, the indicator of the prototype was obtained, and the loss structure under the partial load condition was analyzed quantitatively. It showed that increasing the compression ratio is an effective way to improve the engine power economy under partial load.

The prototype piston head was redesigned, and a cavity was placed between the piston head and the piston skirt to accommodate the pressure reactive mechanism. The mechanism consists of disc springs and other subsidiary bodies. According to the basic parameters of the prototype and the simulation results, access to the relevant information, a non-standard size of the disc spring was designed, through the use of composite combinations to meet the high load, small deformation and high temperature cylinder conditions, and the entire piston was designed. The design was draw in Pro/E.

It was modeled in Adams. The results of these two software iterated each other, and at the same time simulation of an engine performance and dynamics were carried out. The balanced state was gradually approximated by the iterative coupling. The working of the combustion chamber and the simulation results of the piston working process were obtained at the same time.

The performance of the engine was evaluated by analyzing the combustion process in the cylinder. The use of indicators assessed the fuel economy at low load and diesel mode, and the effect of anti-knock at high load and natural gas mode.

The simulation results were obtained by modeling and iterative coupling. The performance evaluation index was used to draw the conclusion: (1) The dynamic and economic efficiency of the PRP testing machine under low load are greatly improved, and the fuel consumption rate in the natural gas mode can be reduced by 2.5 %, The fuel consumption rate in diesel mode can be reduced by up to 4%; (2) The explosion resistance of PRP testing machine is also verified at full load. Under the condition of increasing the compression ratio, the cylinder temperature and the effect of anti-knock, is basically the same as the ACD320, still in the controllable range. There is no tendency to knock.

Keywords: dual-fuel engine, disc spring, pressure reactive piston, iterative coupling, fuel economy, antiknock

目录

第1章 绪论 1

1.1课题的背景及意义 1

1.1.1课题的背景 1

1.1.2课题研究的目的和意义 3

1.2.国内外研究现状 5

1.2.1国外的研究现状 5

1.2.2 国内的研究现状 7

1.3 压力自适应活塞的技术要求与拟解决的科学问题 9

1.3.1压力自适应活塞的技术要求 9

1.3.2 本课题拟解决的技术问题 9

1.4课题研究的目标和主要内容 10

1.4.1 本课题的主要研究目标 10

1.4.2 课题研究的主要内容 10

1.5本课题的研究思路与技术路线 10

1.6 本章小结 12

第2章 柴油-天然气双燃料发动机建模技术分析 13

2.1 原型发动机热力学过程分析 13

2.1.1 GT-power软件简介 13

2.1.2 原型机结构特征分析与主要参数 13

2.1.3 原型机工作过程的建模 14

2.2泵气损失和压缩比对发动机性能的影响 22

2.3 本章小结 23

第3章 双燃料发动机压力自适应活塞技术方案设计 24

3.1压力自适应活塞的设计 24

3.2 弹性元件参数设计 24

3.2.1 弹性元件预紧力的设计 24

3.2.2 压力自适应活塞变化量的设计 26

3.3弹性元件的选型设计 26

3.3.1选择弹性元件考虑的因素 26

3.3.2 碟形弹簧的优点 26

3.4 碟形弹簧的设计 27

3.4.1 碟形弹簧的设计流程 27

3.4.2 单片碟簧的设计 28

3.4.3 组合碟簧的计算 29

3.4.4 碟形弹簧的材料 30

3.5 压力自适应活塞几何模型 30

3.5.1结构设计与工作原理 31

3.6 本章小结 32

第4章 压力自适应活塞的迭代耦合计算 33

4.1压力自适应活塞的动力学仿真模型 33

4.1.1虚拟样机技术与Adams软件 33

4.1.2压力自适应活塞的动力学建模 34

4.2 活塞动力学仿真和发动机性能仿真的迭代耦合与分析 40

4.2.1迭代耦合方法的理论基础 40

4.2.2 迭代耦合方法的实际应用 41

4.3 本章小结 42

第5章 压力自适应活塞技术方案的评价 43

5.1评价指标 43

5.1.1平均指示压力 43

5.1.2指示功率 44

5.1.3 指示热效率 44

5.1.4 指示燃油消耗率 44

5.2与原型机性能对比 45

5.2.1 缸内压力的比较 45

5.2.2 指示平均压力的比较 48

5.2.3 有效燃油消耗率的比较 48

5.2.4 缸内温度对比 49

5.2.5 压力升高率对比 50

5.2.6 气缸工作容积 52

5.3本章小结 52

第6章 总结和展望 53