【作者】 严军；

【导师】 何仁；

【作者基本信息】 江苏大学 ， 车辆工程， 2009， 博士

【摘要】 本文以制动力矩系数最大、启效时间短及恒转矩工作范围大作为液力缓速器设计的目标,着重做了以下工作:在分析和阐述液力缓速器工作特性的基础上,运用CFD技术,建立了液力缓速器单流道模型。为部分充液工况的流场的初始化奠定了基础。调整液力缓速器的结构参数,达到最大制动力矩系数的目的;得出叶片数为36,前倾角度为55°,循环圆形状为长圆形时制动力矩系数最大。以最大制动力矩系数的结构参数建模,全充液工况下,在考虑叶片强度的前提下,根据液力缓速器斜直叶片的结构特点,运用坐标变换、曲面拟合等方法,得到了叶片表面的压力随局部坐标变化的分布函数,根据拟合的压力分布函数,编制APDL加载程序,将叶片表面分布载荷施加到所建立的有限元模型中,从而实现了对压力载荷作用下的液力缓速器叶片强度精确分析。确定额定制动力矩及额定转速,当转速大于额定转速应设计为恒转矩工作范围,以免工作轮叶片过载。在部分充液工况下,采用Mixture多相流模型对部分充液工况下的气-液两相流动进行了数值模拟,得出充液率的变化影响流场的压降。通过数值模拟与试验对比,分析了出入口压差、充液率与制动力矩之间的变化规律,并结合全充液工况的计算结果,建立了基于流场分析的液力缓速器制动力矩控制模型。采用电磁比例阀的气压控制系统,能够满足车用液力缓速器快速响应的控制要求,并对其控制原理和工作过程作了简介。对装有液力缓速器的车辆制动过程进行动力学分析,建立了整车联合制动的数学模型,该数学模型包含的子模型有:汽车制动过程的动力学模型、主制动装置的制动力模型,液力缓速器的制动力模型。利用MATLAB/SIMULINK模块化建模软件,编写S函数模拟真实的恒速下坡制动特性。为有效预测装有液力缓速器车辆的整车制动性能提供可行方法。本文的创新点在于:(1)将液力缓速器动静交界面定义为内部边界,有效解决了液流出入口在同一平面内的问题,建立了液力缓速器流场计算的稳态模型,引入损失分析的方法,使得流场分析更为深入。(2)液力缓速器空转时数值模拟的结果与试验值迥异的根本原因是:循环腔内还存在着部分油液而不是以空气为介质的单相流,再加上传动链中的机械摩擦损失。(3)当缓速器的有效直径和动轮转速相同时,影响缓速能力的主要因素是在流场中是否形成涡旋,形成的涡旋强度越大,缓速能力就越强。以定轮的质量平均螺旋度作为衡量制动能力的量化指标,为液力缓速器的设计提供一种新方法。(4)对液力缓速器工作叶轮进行有限元分析,计算中不仅考虑了液力缓速器工作时的离心载荷,还引入了三维流场计算时所得的叶片工作时的流动载荷,利用坐标变换、曲面拟合以及基于单元的分布载荷加载方法,实现了流固耦合中数据交换,确定额定制动力矩M_N及对应的转速n_N,在超过n_N转速后,制定恒转矩工作的制动原则,以免工作轮过载。(5)利用Mixture多相流模型,对液力缓速器部分充液工况下的气液两相流场进行了数值模拟,得到充液率与流场压降的函数关系,建立了全工况下液力缓速器制动力矩控制模型。更多还原

【Abstract】 In the paper,to make a optimization design target of maximum 2,minimum response time and large scope of constant moment,the main research structure and highlights of the paper are as followed:On the basis of characteristic of hydraulic retarder,By using the time-averaged N-S equation and the standardκ-εturbulence and the SIMPLE-C algorithm simultaneously,the internal characteristics of flow field is simulated which establish the foundation of two-phrase model’s initialization.The geometrical parameters is adjusted in order to obtainedλ_M and results show that the model with 36 blade number,55 degree of lean-front blade and oval section recycled circle has the biggest braking impact.Stress of an actual three dimensional blade is analyzed with digitization model which obtain AM o According to the structural feature of hydraulic retarder,pressure distribution is obtained by using coordinate transformation and surface fitting,which vary with x-coordinate and y-coordinate in local coordinates.Pressure loads are loaded on the FEA model by compiling program with APDL.Noted moment and speed is determined under the promise of blade strength,and controlling strategy is made that noted braking moment is carried out when speed is higher than noted value.The two-phase flow of the partially filled in the hydraulic retarder is simulated by using the Mixture multiphase model.The experimental data is analyzed and compared with the numerical results,which show that variation of volume fraction effect the pressure drop.With the analysis results in full-filled condition,the braking torque control model is built by normalization method.Gas pressure controlling system which electromagnetic proportion valve is adopted meet the requirement of rapid response,while working principle and controlling method is discussed.The mathematic model of united braking system is set up which involved the hydraulic retarde and primary braking device.Simulink software is employed to analyse the simulation of emergency braking,nonemergency braking and contionous braking, especially using S function to simulate constant speed during downhill. The major innovations in this paper are as follows:(1) The interface between rotator and stator is defined as interior boundary in hydraulic retarder which effectively solve the problem of fluid flow in and out in the same plane.The internal characteristic of flow field is simulated and the method of loss analysis is proposed in order to make analysis furthermore.(2) Indicate that why the experiment data of air blass loss is larger than numerical result is that there are a few liquid oil not purely air in the flow field,in addition to the mechanical friction loss in driveline(3) Indicated that braking essential reason to the hydraulic retarder is that the more intensity of vortex,the more capacity of braking performance,and the method of analysis is proposed which mass-average helicity is used to compare the retarder ability.(4) Stress of an actual three dimensional blade is analyzed with digitization model, in which the stress and strain distribution of impellers are discussed in detail.It is noted about the calculation that not only the centrifugal load but also the flow load resulted from the 3D numerical simulations of the flow field of the blade are considered.By using coordinate transformation and surface fitting,pressure loads are loaded on the FEA model according to ANSYS Parametric Design Language to realize the data transformation in liquid-solid coupling.(5) The two-phase flow of the partially filled in the hydraulic retarder is simulated by using the Mixture multiphase model and indicate that volume fraction is in functional relationship with pressure drop and the braking torque control model is built by normalization method.更多还原