摘 要

LNG发动机结合废气-燃料重整（REGR）技术，能实现在线制氢，改善发动机的燃烧和排放性能。本次研究运用GT-SUITE软件构建废气-燃料重整器与点燃式船用LNG发动机的一维闭环数值模拟模型，探究得出了部分运行参数对发动机燃烧与排放性能的一般影响规律： 随着REGR率的增大，发动机功率减小、NO_x排放较低、指示燃油消耗率增大；随着点火提前角的减小，HC排放和指示燃油消耗率急剧上升；随着重整甲烷量的增加，功率基本不变、HC排放有所降低；随着过量空气系数的增加，NO_x排放降低、指示燃油消耗率增加。

基于上述研究，借助modeFRONTIER开展闭环系统运行参数多目标优化研究，得到一系列重整器与发动机匹配运行的最优解组合。本文主要研究了以REGR率、过量空气系数、重整甲烷量等运行参数为输入变量，以同时满足NO_x排放和燃油消耗量为目标进行优化，实现LNG发动机催化重整制氢的量和发动机不同工况最优匹配。从多目标优化的Pareto最优解中选出一个最优匹配方案：过量空气系数λ=1.3353、REGR率=0.097737、重整甲烷MO=1.0235。该方案下NO_x排放为1054.5ppm,油耗为21.496kg/h,功率为117.92kW。与原机工况点相比，NO_x降低了1642.5ppm，相比原机NO_x下降60.9%；油耗降低了0.104kg/h，相比原机油耗下降4.8%。希望本文能为LNG发动机上REGR技术应用以及性能优化提供参考。

关键词：LNG发动机； 闭环系统模型； 多目标参数优化； Pareto最优解Abstract

The LNG engine combined with exhaust gas-fuel reforming (REGR) technology can realize online hydrogen production and improve the combustion and emission performance of the engine. This study uses GT-SUITE software to build a one-dimensional closed-loop numerical simulation model of exhaust gas-fuel reformer and ignited marine LNG engine, and explores the general influence of some operating parameters on engine combustion and emissions performance As the rate increases, engine power decreases, NO_x emissions are lower, and the indicated fuel consumption rate increases; as the ignition advance angle decreases, HC emissions and the indicated fuel consumption rate rise sharply; as the amount of reformed methane increases The power is basically unchanged, and HC emissions are reduced; as the excess air coefficient increases, NO_x emissions decrease and the indicated fuel consumption rate increases.

Based on the above research, with the help of modeFRONTIER, a multi-objective optimization study of the operating parameters of the closed-loop system was carried out, and a series of optimal solution combinations for the matched operation of the reformer and the engine were obtained. This paper mainly studies the operating parameters such as REGR rate, excess air coefficient, and reformed methane amount as input variables, and optimizes to meet the requirements of both NO_x emissions and fuel consumption. Optimal matching of operating conditions. An optimal matching scheme was selected from the Pareto optimal solution of multi-objective optimization: excess air coefficient λ = 1.3353, REGR rate = 0.097737, and reformed methane MO = 1.0235. Under this scheme, the NO_x emission is 1054.5ppm, the fuel consumption is 21.496kg / h, and the power is 117.92kW. Compared with the operating point of the original engine, NO_x decreased by 1642.5ppm, compared with the original engine NO_x decreased by 60.9%; fuel consumption decreased by 0.104kg / h, compared with the original engine fuel consumption decreased by 4.8%. I hope this article can provide a reference for the application of REGR technology and performance optimization on LNG engines.

Keywords: LNG engine; closed-loop system model; multi-objective parameters optimization; Pareto optimal solution

目录

第1章 绪论 1

1.1 研究背景 1

1.2废气重整LNG发动机概念简介 1

1.3 多目标参数优化简介 3

1.4研究内容与目的 4

第2章 LNG发动机与废气-燃料重整器闭环系统模型构建 6

2.1 基本控制方程 6

2.2 发动机模型构建 6

2.3 重整器模型构建 8

2．4 闭环模型构建与验证 8

2．4．1 闭环模型构建 8

2．4．2 闭环模型验证 12

第3章 LNG发动机与废气-燃料重整器闭环系统性能分析 13

3.1 REGR率对闭环系统性能的影响规律 13

3.2 重整甲烷供给量闭环系统性能的影响规律 15

3.3 点火正时对闭环系统性能的影响规律 17

3.4 过量空气系数闭环系统性能的影响规律 18

第4章 基于多目标参数优化的闭环系统优化研究 21

4.1多目标参数优化理论 21

4.2闭环系统目标函数构建 22

4.3 多目标优化分析 24

4.3.1 遗传算法迭代求解 24

4.3.2 Pareto最优解 26

4.3.3 满足NO_x排放要求的控制参数匹配 29

第5章 总结 32

展望 34

参考文献 35

致谢 37

第1章 绪论

1.1 研究背景

为了节约能源、降低污染物排放，满足现行日趋严格的排放法规，应对石油危机，发动机替代燃料的研究引起了国内外研究者的广泛关注。积极寻找清洁能源作为内燃机的动力来源也是内燃机技术革新的一项关键举措，乙醇、甲醇、二甲醚、异辛烷、天然气等清洁能源因其各自独特的优势，成为研究焦点，有望在不久的将来能替代石油成为新的内燃机燃料。

其中天然气储量丰富，液化天然气（即LNG）更是凭借储存运输方便、能量密度大、燃烧稳定、污染物排放低等优点，得到大力发展。低温稀薄燃烧能使天然气和空气更好地混合实现充分燃烧，同时降低氮氧化物的排放。采用低温稀薄燃烧和EGR，可以降低NO_x排放并在一定程度上抑制敲缸，但EGR率过大又容易引起较大循环波动，严重甚至会导致发动机失火，且会增加HC和CO排放。