瞬态流固耦合作用下天然气发电内燃机排气歧管结构优化设计  

Optimal structure design of exhaust manifolds of internal combustion engines in a natural gas generator under transient fluid-structure coupling

作　　者：杨汉乾[1,2] 马金浩 胡志坚 易仲威 付建勤[2] YANG Hanqian;MA Jinhao;HU Zhijian;YI Zhongwei;FU Jianqin(College of Mechanical and Electrical Engineering,Central South University of Forestry and Technology,Changsha 410004,China;College of Mechanical and Vehicle Engineering,Hunan University,Changsha 410082,China)

机构地区：[1]中南林业科技大学机电工程学院,长沙410004 [2]湖南大学机械与运载工程学院,长沙410082

出　　处：《重庆理工大学学报（自然科学）》2023年第4期286-293,共8页Journal of Chongqing University of Technology：Natural Science

基　　金：国家自然科学基金面上项目(51876056);湖南省自然科学基金重点项目(13JJ8001)。

摘　　要：天然气发动机用于发电用途后,工作时间长,排气温度高。车用柴油机改制成燃气发电内燃机后,为了进一步改善燃油经济性和提高排气歧管的可靠性,通过一、三维仿真建模对排气歧管结构进行优化。研究认为原机排气歧管为了兼顾低转速的性能,管径设计较小,在1500 r/min时排气背压较大,不适宜应用在改制后的燃气发电内燃机。本研究经过一维数值计算,通过优化管径可以降低线工况下的燃气消耗,并且提高了工作功率。其次通过逆向建模方法和Fluent UDF模块建立流固耦合瞬态仿真模型,耦合计算了5个工作循环中的3个时间点,并且提出了2种排气歧管的结构优化方法,进行了排温瞬变过程中的热负荷分析和对比。结果表明增加加强筋结构的方案在节省材料的基础上可进一步减少热变形量,有利于提高排气歧管的寿命,满足燃气发电内燃机的设计要求。建模和优化方法可为燃气发电内燃机排气管的设计提供参考。Nowadays,the development of efficient and clean low-carbon energy equipment is the main direction of energy and power development in China.Currently,diesel fuel is generally used as the main fuel for generator units,which has higher particulate matter and hydrocarbon content in internal combustion engine diesel emissions compared with natural gas.After the conversion of the automotive diesel engine into a gas-fired internal combustion engine,the exhaust temperature is higher due to its long operating time.In order to further improve the fuel economy and increase the reliability of an exhaust manifold,this article optimizes the exhaust manifold structure by means of a 3D simulation modeling.Before the modification,the exhaust manifold of the original machine is designed with a short diameter in order to take into account of the performance at a low speed.In addition,the exhaust back pressure at a speed of 1500 r/min is high,which is not suitable for the modified gas powered internal combustion engine.Through GT-Power one-dimensional numerical calculation,gas consumption in a single working condition can be reduced by optimizing the pipe diameter.After the manifold diameter increases from 35 mm to 40 mm,the power of the whole machine increases by 2.3 kW,the pump gas loss reduces by 5 kPa,and the gas consumption rate reduces by 1.7 g/(kW·h).Secondly,by using the inverse modeling method and Fluent UDF module,a transient fluid-structure coupling simulation model is established,and the heat transfer coefficient of the fluid domain wall and the heat deformation of the exhaust manifold area at three time points in five working cycles are calculated.The coupling time points are 180°CA,540°CA and 720°CA.Based on the numerical results,two structural optimization methods for exhaust manifolds are proposed.The first optimization plan removes part of the stiffeners and connecting plates,and the second plan adds two stiffeners.After the heat load analysis and comparison in the transient process of temperature discharge,the

关 键 词：天然气发动机 排气歧管 流固耦合 结构优化 热负荷分析 

分 类 号：TK433[动力工程及工程热物理—动力机械及工程]