【作者】 刘勇；

【导师】 明平剑；

【作者基本信息】 哈尔滨工程大学 ， 动力工程及工程热物理， 2021， 硕士

【摘要】 气缸中心距是柴油机整机概念设计关键尺寸之一,直接影响柴油机总体尺寸、强度和冷却等系统的布置。目前,关于缸心距尺寸设计的相关研究依旧停留在经验设计的方法上,该方法在设计过程中高度依赖经验设计值,且仅考虑了设计尺寸对柴油机动力学系统的影响。考虑到现有缸心距设计方法的不足,本文在Dymola平台建立柴油机缸心距设计计算仿真模型,提出一种综合考虑柴油机热力学系统、动力学系统以及冷却水系统的设计方法;在现役船舶柴油机设计参数的基础上,利用多层感知器神经网络模型实现缸心距设计尺寸的预测模型。以6EX340柴油机为例,搭建其单缸柴油机模型并仿真计算,其中动力学系统与缸内工作过程之间通过不同接口实时传递缸内压力与转速,实现了热力学与动力学之间的耦合计算;根据6EX340柴油机冷却水系统的布置图,并结合缸内工作过程搭建整机冷却水系统,仿真计算得到冷却水系统关键位置的温度、燃烧室部件壁面温度等信息,利用三维稳态温度场仿真验证了冷却水系统与热力学系统之间耦合计算的正确性;在单缸机、冷却水系统的仿真基础上,建立多缸柴油机缸心距设计计算模型,以6EX340柴油机为例进行不同工况的仿真计算,部分仿真结果与试验值进行对比证明了该模型的正确性,仿真计算的结果主要包含柴油机热力学的相关特征参数,冷却水流量的分布,输出扭矩等。在缸心距设计计算模型的基础上,提出综合考量缸心距尺寸适宜性的评估方法,评估方法主要包括在模型仿真基础上的柴油机平衡性分析、曲轴的受力分析、曲轴的疲劳强度分析以及冷却水的分布分析;通过改变缸心距尺寸,分析了缸心距尺寸变化对评估内容的影响,发现缸心距尺寸的变化对于冷却水分布的影响较小,会明显影响柴油机的平衡性以及曲轴的受力。统计现役船舶柴油机的设计参数,分析缸心距与缸径等参数的关系,并利用多层感知神经网络预测模型建立二冲程柴油机缸心距尺寸的预测模型,缸心距的预测模型整体预测表现较好,预测结果的平均百分比误差(MAPE)小于2%,相关系数达到0.999,预测结果与真实值已经充分逼近线性相关关系,在柴油机预设计阶段利用少量的基本设计参数即能够精确实现缸心距尺寸的预测。更多还原

【Abstract】 Cylinder center distance is one of the key dimensions in the conceptual design of the diesel engine,which directly affects the overall size,strength and cooling system layout of the diesel engine.At present,the relevant research on the design of the cylinder distance is still based on the empirical design method,which highly relies on the empirical design value in the design process,and only considers the influence of the design size on the dynamic system of the diesel engine.Taking into account the shortcomings of the existing cylinder center distance design method,this paper establishes a diesel engine cylinder center distance design calculation simulation model on the Dymola platform,and proposes a design method that comprehensively considers the diesel engine thermodynamic system,dynamic system and cooling water system;Based on the design parameters,the multi-layer perceptron neural network model is used to realize the prediction model of the cylinder center distance design size.Take the 6EX340 diesel engine as an example,build its single-cylinder diesel engine model and perform simulation calculations,in which the dynamic system and the in-cylinder working process are transmitted in real time through different interfaces between the in-cylinder pressure and speed,which realizes the coupled calculation between thermodynamics and dynamics;According to the layout drawing of the cooling water system of the 6EX340 diesel engine,combined with the working process in the cylinder to build the cooling water system of the whole machine,the temperature of the key positions of the cooling water system and the wall temperature of the combustion chamber components are obtained by simulation calculation,and the three-dimensional steady-state temperature field simulation is used to verify The correctness of the coupling calculation between the cooling water system and the thermodynamic system;based on the simulation of the single-cylinder engine and the cooling water system,the multi-cylinder diesel engine cylinder center distance design calculation model is established,and the 6EX340 diesel engine is used as an example to simulate different working conditions The calculation and comparison of part of the simulation results with the experimental values prove the correctness of the model.The simulation results mainly include the relevant characteristic parameters of diesel engine thermodynamics,the distribution of cooling water flow,and the output torque.Based on the design and calculation model of cylinder center distance,an evaluation method that comprehensively considers the suitability of cylinder center distance is proposed.The evaluation method mainly includes diesel engine balance analysis,crankshaft stress analysis,and crankshaft fatigue strength analysis based on model simulation.And cooling water distribution analysis;by changing the size of the cylinder center distance,the influence of the change of the cylinder center distance size on the evaluation content is analyzed,and it is found that the change of the cylinder center distance size has a small effect on the cooling water distribution,which will obviously affect the balance of the diesel engine And the force of the crankshaft.Calculate the design parameters of marine diesel engines in service,analyze the relationship between cylinder center distance and cylinder diameter and other parameters,and use the multi-layer perceptual neural network prediction model to establish a two-stroke diesel engine cylinder center distance prediction model.The prediction model of cylinder center distance performs well in overall prediction,the average percentage error(MAPE)of the prediction result is less than 2%,and the correlation coefficient reaches 0.999.The prediction result and the real value have fully approximated the linear correlation.In the diesel engine pre-design stage,a small amount of basic design parameters can be used to accurately achieve the cylinder center distance.Size prediction.更多还原