液力缓速器制动机理研究
发布时间：2018-09-09 10:26
【摘要】：制动装置直接关系行车安全,尤其是重型运输车辆,制动扭矩很大,常规的摩擦制动装置在制动过程中,存在热耗散效率低,制动时间长,制动过热、极易损坏等殃及行车安全问题,加装液力缓速器辅助制动系统是解决其问题的重要途径之一。为此,我们已展开了近10年的产品开发工作,研制出了几种型号的液力缓速器产品。由于其急速制动过程的影响因素繁多,非稳态充液过程中功热转换及耗散的非线性变化特征的理论表达,充液介质物性及其变化特征、流态、位置,功热转换强度动态变化,导致系统内部复杂地扰动,反过来又引起功热转换及耗散发生本质的变化,瞬态过程液固相互作用机制诸多技术基础问题尚解释不清。为此,本研究从表征液力缓速器制动性能的综合特征参数入手,深入分析液力缓速器工作介质物性、装置几何结构定性特征参数、运动特征参数之间的内在关系及相互作用的机制,揭示介质温度与粘度、充液率与介质流变特性、介质粘度与制动扭矩、不同充液率下转速与制动扭矩的关系及其变化规律;以近年我们与深圳市特尔佳科技股份有限公司共同研发的THB40液力缓速器为对象,以量纲分析,相似性论证为主要任务,采用理论分析、CFD计算与试验考证相结合的方法,揭示非稳态过程中的功热转换与耗散规律,阐明液力缓速器制动机理,论文研究工作及创新点主要体现在以下几方面:1)在分析国内外液力缓速器研究的基础上,结合课题组与深圳市特尔佳科技股份有限公司合作研发的THB40液力缓速器,在分析其原理、结构、特性和存在的问题的基础上,证实了介质的运动特征状态在制动过程中,存在由膨性、塑性、假塑性流态交互转换的质变点。2)在计算流体力学典型的控制方程基础上,以液力缓速器内流场的特点选择kSST-ω双方程湍流模型,并给出了方程中的关键参数的求法;在此基础上介绍了求解过程与液力缓速器制动扭矩的计算方法。3)基于气液两相模型对液力缓速器以不同充液率、不同温度、不同转速、不同粘度进行了CFD仿真计算。通过对计算结果的分析,得出以下结论:相同转速和介质温度下制动扭矩随充液率的增加而增大;相同充液率和转速下制动扭矩随温度的升高而增大,但增加的速率随温度升高而减小,在温度高于90℃时,制动扭矩值趋于平缓;在相同充液率和温度下,制动扭矩随转速的变化与充液率有关,充液率在95%时转速升高制动扭矩增大。4)用HVM472型全自动宽量程粘度仪对本文研究所用油液介质壳牌全合成5W-40润滑油在不同温度下的粘度进行了测定,验证了表征油液介质粘温特性的瓦尔塞方程的正确;在台架上对液力缓速器以不同温粘度、不同控制气压、不同转速进行了制动性能试验,制动扭矩结果和相同条件下CFD数值计算的制动扭矩结果进行了比对,两者变化趋势是基本一致的:在95%充液率、工作介质温度95℃时,制动扭矩随转速升高而增大,两者最大误差3.6%;在95%充液率、转速600r/min时,制动扭矩随介质温度升高而增大,随表观动力粘度增大而减小,两者最大误差5.83%;在转速600r/min、介质温度70℃时,制动扭矩随充液率提高而增大,两者最大误差4.3%。结果表明CFD数值计算模型是正确的,结果是可信的。5)运用量纲分析的π定理,对与液力缓速器制动性能相关的参数进行了无量纲化研究,以介质密度、介质流速、介质定压比热容和液力缓速器特征长度为基本物理参数,推导了基于介质表观动力粘度、热导率、液力缓速器工作腔压力和制动扭矩量纲的无量纲数μπ、λπ、pπ和eTπ,得到了制动扭矩与介质密度、介质流速、液力缓速器特征长度、雷诺数、贝克莱数和欧拉数的关系式。接着结合CFD数值计算与台架试验对相似准则数与液力缓速器制动机理间的关系进行了研究,结果表明:在38%充液率下,雷诺数和贝克莱数随转速升高而减小,欧拉数和普朗特数随转速升高而增大,在95%充液率下则相反;制动扭矩都随雷诺数和贝克莱数增大而增大,随欧拉数和普朗特数增大而减小。结果验证了基于量纲分析的制动扭矩关系式的正确。6)基于台架试验和CFD计算结果对介质参数与液力缓速器制动机理间的关系进行了研究,得出如下结果:充液率大于等于72%时,液力缓速器工作介质属于假塑性非牛顿流体,粘度随剪切速率增大而变小,制动扭矩随转速升高而增大;充液率小于等于68%时,工作介质属于胀塑性非牛顿流体,介质粘度随着剪切速率而增大,制动扭矩随转速升高减小;充液率和制动扭矩之间存在线性的对应关系;控制气压与充液率间存在近似线性对应关系,最大控制档位2.8bar控制气压相当于95%充液率,0.66bar相当于38%充液率;介质表观动力粘度随温度呈指数为负1.8系数K为与充液率有关的幂函数关系,K与充液率是系数为0.4523的线性正相关关系,并验证了是正确的;液力缓速器制动扭矩都是随工作介质表观动力粘度的减小而增大的,但减小的方式和介质的流变特性有关;液力缓速器制动扭矩与介质密度间存在线性的正相关关系。
[Abstract]:Brake device is directly related to traffic safety, especially for heavy-duty transport vehicles. Brake torque is very large. Conventional friction brake device has low heat dissipation efficiency, long braking time, over-heat braking and easy damage during braking process, which will affect traffic safety. Adding hydraulic retarder auxiliary brake system is an important way to solve the problem. 1. For this purpose, we have developed several types of hydraulic retarders in the past 10 years. Because of the various factors affecting the rapid braking process, the theoretical expression of the nonlinear variation characteristics of power-heat transfer and dissipation during the unsteady filling process, the physical properties of the liquid-filled medium and its variation characteristics, flow pattern, position, power-heat transfer characteristics, etc. The dynamic change of conversion intensity leads to complex disturbance in the system, which in turn leads to the change of power and heat transfer and dissipation. Many technical problems of liquid-solid interaction mechanism in transient process are still unclear. The physical properties of the working medium, the qualitative characteristic parameters of the geometric structure of the device, the intrinsic relationship between the characteristic parameters of motion and the mechanism of interaction are revealed. The THB40 hydraulic retarder developed by Shenzhen Teljia Science and Technology Co., Ltd. is taken as the object of study. The main task is dimension analysis and similarity demonstration. The method of combining theoretical analysis, CFD calculation with test verification is adopted to reveal the law of power and heat transfer and dissipation in the unsteady process, and to clarify the braking mechanism of hydraulic retarder. The work and innovations are mainly embodied in the following aspects: 1) On the basis of analyzing the research of hydraulic retarders at home and abroad, combined with the THB40 hydraulic retarder developed by the research group and Shenzhen Teljia Technology Co., Ltd., the principle, structure, characteristics and existing problems of the THB40 hydraulic retarder are analyzed, and the motion characteristics of the medium are confirmed. In the braking process, there is a mass change point from dilatancy, plasticity and pseudoplastic flow. 2) Based on the typical control equations of computational fluid dynamics, the kSST-_two-equation turbulence model is selected according to the characteristics of the flow field in the hydraulic retarder, and the method of solving the key parameters in the equation is given. Based on the gas-liquid two-phase model, the brake torque of hydraulic retarder is calculated by CFD simulation with different filling rate, temperature, rotational speed and viscosity. At the same filling rate and temperature, the change of the braking torque with the filling rate is related to the filling rate, and the braking torque increases with the filling rate at 95%. 4) The braking torque of HVM472 increases with the filling rate at 95%. The viscosity of 5W-40 lubricating oil synthesized by Shell was measured by dynamic wide-range viscometer at different temperatures, and the Walser equation was proved to be correct. The braking performance of the hydraulic retarder was tested at different temperatures, viscosities, pressure and rotational speeds on a bench. Test results show that the braking torque results are basically the same as those calculated by CFD under the same conditions. The braking torque increases with the increase of rotational speed at 95% liquid filling rate and working medium temperature of 95, the maximum error is 3.6%; the braking torque increases with the increase of medium temperature at 95% liquid filling rate and 600 R / min rotational speed. The maximum error is 5.83% when the apparent dynamic viscosity increases, and the maximum error is 4.3% when the rotational speed is 600 r/min and the medium temperature is 70%. The results show that the CFD numerical calculation model is correct and the results are credible. The dimensionless parameters related to the performance are studied. The dimensionless parameters of Mu pi, lambda pi, P PI and eT PI are derived based on the apparent dynamic viscosity, thermal conductivity, pressure and braking torque dimension of the fluid retarder. The relationship between braking torque and medium density, medium velocity, characteristic length of hydraulic retarder, Reynolds number, Berkeley number and Euler number is studied. Then the relationship between similar criterion number and braking mechanism of hydraulic retarder is studied by CFD numerical calculation and bench test. The results show that Reynolds number and Berkeley number vary with rotational speed at 38% filling rate. The braking torque increases with the increase of Reynolds number and Berkeley number, and decreases with the increase of Euler number and Plante number. The relationship between medium parameters and braking mechanism of hydraulic retarder is studied. The results are as follows: when the filling rate is greater than or equal to 72%, the working medium of hydraulic retarder belongs to pseudoplastic non-Newtonian fluid, the viscosity decreases with the increase of shear rate, the braking torque increases with the increase of rotational speed; when the filling rate is less than or equal to 68%, the working medium belongs to pseudoplastic non-Newtonian fluid. Expansion plastic non-Newtonian fluid, medium viscosity increases with shear rate, braking torque decreases with rotational speed; there is a linear relationship between filling rate and braking torque; there is an approximate linear relationship between control pressure and filling rate, the maximum control gear 2.8 bar control pressure is equivalent to 95% filling rate, 0.66 bar is equivalent to 38% filling rate. The apparent dynamic viscosity of the medium is exponentially negative 1.8 coefficient K, which is a power function of the liquid filling rate, and the linear positive correlation between K and the liquid filling rate coefficient is 0.4523, which is verified to be correct. There is a linear positive correlation between the torque and the density of the hydraulic retarder.
【学位授予单位】：华南农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：U463.5
，
本文编号：2232117
[Abstract]:Brake device is directly related to traffic safety, especially for heavy-duty transport vehicles. Brake torque is very large. Conventional friction brake device has low heat dissipation efficiency, long braking time, over-heat braking and easy damage during braking process, which will affect traffic safety. Adding hydraulic retarder auxiliary brake system is an important way to solve the problem. 1. For this purpose, we have developed several types of hydraulic retarders in the past 10 years. Because of the various factors affecting the rapid braking process, the theoretical expression of the nonlinear variation characteristics of power-heat transfer and dissipation during the unsteady filling process, the physical properties of the liquid-filled medium and its variation characteristics, flow pattern, position, power-heat transfer characteristics, etc. The dynamic change of conversion intensity leads to complex disturbance in the system, which in turn leads to the change of power and heat transfer and dissipation. Many technical problems of liquid-solid interaction mechanism in transient process are still unclear. The physical properties of the working medium, the qualitative characteristic parameters of the geometric structure of the device, the intrinsic relationship between the characteristic parameters of motion and the mechanism of interaction are revealed. The THB40 hydraulic retarder developed by Shenzhen Teljia Science and Technology Co., Ltd. is taken as the object of study. The main task is dimension analysis and similarity demonstration. The method of combining theoretical analysis, CFD calculation with test verification is adopted to reveal the law of power and heat transfer and dissipation in the unsteady process, and to clarify the braking mechanism of hydraulic retarder. The work and innovations are mainly embodied in the following aspects: 1) On the basis of analyzing the research of hydraulic retarders at home and abroad, combined with the THB40 hydraulic retarder developed by the research group and Shenzhen Teljia Technology Co., Ltd., the principle, structure, characteristics and existing problems of the THB40 hydraulic retarder are analyzed, and the motion characteristics of the medium are confirmed. In the braking process, there is a mass change point from dilatancy, plasticity and pseudoplastic flow. 2) Based on the typical control equations of computational fluid dynamics, the kSST-_two-equation turbulence model is selected according to the characteristics of the flow field in the hydraulic retarder, and the method of solving the key parameters in the equation is given. Based on the gas-liquid two-phase model, the brake torque of hydraulic retarder is calculated by CFD simulation with different filling rate, temperature, rotational speed and viscosity. At the same filling rate and temperature, the change of the braking torque with the filling rate is related to the filling rate, and the braking torque increases with the filling rate at 95%. 4) The braking torque of HVM472 increases with the filling rate at 95%. The viscosity of 5W-40 lubricating oil synthesized by Shell was measured by dynamic wide-range viscometer at different temperatures, and the Walser equation was proved to be correct. The braking performance of the hydraulic retarder was tested at different temperatures, viscosities, pressure and rotational speeds on a bench. Test results show that the braking torque results are basically the same as those calculated by CFD under the same conditions. The braking torque increases with the increase of rotational speed at 95% liquid filling rate and working medium temperature of 95, the maximum error is 3.6%; the braking torque increases with the increase of medium temperature at 95% liquid filling rate and 600 R / min rotational speed. The maximum error is 5.83% when the apparent dynamic viscosity increases, and the maximum error is 4.3% when the rotational speed is 600 r/min and the medium temperature is 70%. The results show that the CFD numerical calculation model is correct and the results are credible. The dimensionless parameters related to the performance are studied. The dimensionless parameters of Mu pi, lambda pi, P PI and eT PI are derived based on the apparent dynamic viscosity, thermal conductivity, pressure and braking torque dimension of the fluid retarder. The relationship between braking torque and medium density, medium velocity, characteristic length of hydraulic retarder, Reynolds number, Berkeley number and Euler number is studied. Then the relationship between similar criterion number and braking mechanism of hydraulic retarder is studied by CFD numerical calculation and bench test. The results show that Reynolds number and Berkeley number vary with rotational speed at 38% filling rate. The braking torque increases with the increase of Reynolds number and Berkeley number, and decreases with the increase of Euler number and Plante number. The relationship between medium parameters and braking mechanism of hydraulic retarder is studied. The results are as follows: when the filling rate is greater than or equal to 72%, the working medium of hydraulic retarder belongs to pseudoplastic non-Newtonian fluid, the viscosity decreases with the increase of shear rate, the braking torque increases with the increase of rotational speed; when the filling rate is less than or equal to 68%, the working medium belongs to pseudoplastic non-Newtonian fluid. Expansion plastic non-Newtonian fluid, medium viscosity increases with shear rate, braking torque decreases with rotational speed; there is a linear relationship between filling rate and braking torque; there is an approximate linear relationship between control pressure and filling rate, the maximum control gear 2.8 bar control pressure is equivalent to 95% filling rate, 0.66 bar is equivalent to 38% filling rate. The apparent dynamic viscosity of the medium is exponentially negative 1.8 coefficient K, which is a power function of the liquid filling rate, and the linear positive correlation between K and the liquid filling rate coefficient is 0.4523, which is verified to be correct. There is a linear positive correlation between the torque and the density of the hydraulic retarder.
【学位授予单位】：华南农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：U463.5
，
本文编号：2232117
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