液力緩速器制動機理研究
發(fā)布時間：2018-09-09 10:26
【摘要】：制動裝置直接關系行車安全,尤其是重型運輸車輛,制動扭矩很大,常規(guī)的摩擦制動裝置在制動過程中,存在熱耗散效率低,制動時間長,制動過熱、極易損壞等殃及行車安全問題,加裝液力緩速器輔助制動系統(tǒng)是解決其問題的重要途徑之一。為此,我們已展開了近10年的產(chǎn)品開發(fā)工作,研制出了幾種型號的液力緩速器產(chǎn)品。由于其急速制動過程的影響因素繁多,非穩(wěn)態(tài)充液過程中功熱轉換及耗散的非線性變化特征的理論表達,充液介質物性及其變化特征、流態(tài)、位置,功熱轉換強度動態(tài)變化,導致系統(tǒng)內部復雜地擾動,反過來又引起功熱轉換及耗散發(fā)生本質的變化,瞬態(tài)過程液固相互作用機制諸多技術基礎問題尚解釋不清。為此,本研究從表征液力緩速器制動性能的綜合特征參數(shù)入手,深入分析液力緩速器工作介質物性、裝置幾何結構定性特征參數(shù)、運動特征參數(shù)之間的內在關系及相互作用的機制,揭示介質溫度與粘度、充液率與介質流變特性、介質粘度與制動扭矩、不同充液率下轉速與制動扭矩的關系及其變化規(guī)律;以近年我們與深圳市特爾佳科技股份有限公司共同研發(fā)的THB40液力緩速器為對象,以量綱分析,相似性論證為主要任務,采用理論分析、CFD計算與試驗考證相結合的方法,揭示非穩(wěn)態(tài)過程中的功熱轉換與耗散規(guī)律,闡明液力緩速器制動機理,論文研究工作及創(chuàng)新點主要體現(xiàn)在以下幾方面:1)在分析國內外液力緩速器研究的基礎上,結合課題組與深圳市特爾佳科技股份有限公司合作研發(fā)的THB40液力緩速器,在分析其原理、結構、特性和存在的問題的基礎上,證實了介質的運動特征狀態(tài)在制動過程中,存在由膨性、塑性、假塑性流態(tài)交互轉換的質變點。2)在計算流體力學典型的控制方程基礎上,以液力緩速器內流場的特點選擇kSST-ω雙方程湍流模型,并給出了方程中的關鍵參數(shù)的求法;在此基礎上介紹了求解過程與液力緩速器制動扭矩的計算方法。3)基于氣液兩相模型對液力緩速器以不同充液率、不同溫度、不同轉速、不同粘度進行了CFD仿真計算。通過對計算結果的分析,得出以下結論:相同轉速和介質溫度下制動扭矩隨充液率的增加而增大;相同充液率和轉速下制動扭矩隨溫度的升高而增大,但增加的速率隨溫度升高而減小,在溫度高于90℃時,制動扭矩值趨于平緩;在相同充液率和溫度下,制動扭矩隨轉速的變化與充液率有關,充液率在95%時轉速升高制動扭矩增大。4)用HVM472型全自動寬量程粘度儀對本文研究所用油液介質殼牌全合成5W-40潤滑油在不同溫度下的粘度進行了測定,驗證了表征油液介質粘溫特性的瓦爾塞方程的正確;在臺架上對液力緩速器以不同溫粘度、不同控制氣壓、不同轉速進行了制動性能試驗,制動扭矩結果和相同條件下CFD數(shù)值計算的制動扭矩結果進行了比對,兩者變化趨勢是基本一致的:在95%充液率、工作介質溫度95℃時,制動扭矩隨轉速升高而增大,兩者最大誤差3.6%;在95%充液率、轉速600r/min時,制動扭矩隨介質溫度升高而增大,隨表觀動力粘度增大而減小,兩者最大誤差5.83%;在轉速600r/min、介質溫度70℃時,制動扭矩隨充液率提高而增大,兩者最大誤差4.3%。結果表明CFD數(shù)值計算模型是正確的,結果是可信的。5)運用量綱分析的π定理,對與液力緩速器制動性能相關的參數(shù)進行了無量綱化研究,以介質密度、介質流速、介質定壓比熱容和液力緩速器特征長度為基本物理參數(shù),推導了基于介質表觀動力粘度、熱導率、液力緩速器工作腔壓力和制動扭矩量綱的無量綱數(shù)μπ、λπ、pπ和eTπ,得到了制動扭矩與介質密度、介質流速、液力緩速器特征長度、雷諾數(shù)、貝克萊數(shù)和歐拉數(shù)的關系式。接著結合CFD數(shù)值計算與臺架試驗對相似準則數(shù)與液力緩速器制動機理間的關系進行了研究,結果表明:在38%充液率下,雷諾數(shù)和貝克萊數(shù)隨轉速升高而減小,歐拉數(shù)和普朗特數(shù)隨轉速升高而增大,在95%充液率下則相反;制動扭矩都隨雷諾數(shù)和貝克萊數(shù)增大而增大,隨歐拉數(shù)和普朗特數(shù)增大而減小。結果驗證了基于量綱分析的制動扭矩關系式的正確。6)基于臺架試驗和CFD計算結果對介質參數(shù)與液力緩速器制動機理間的關系進行了研究,得出如下結果:充液率大于等于72%時,液力緩速器工作介質屬于假塑性非牛頓流體,粘度隨剪切速率增大而變小,制動扭矩隨轉速升高而增大;充液率小于等于68%時,工作介質屬于脹塑性非牛頓流體,介質粘度隨著剪切速率而增大,制動扭矩隨轉速升高減小;充液率和制動扭矩之間存在線性的對應關系;控制氣壓與充液率間存在近似線性對應關系,最大控制檔位2.8bar控制氣壓相當于95%充液率,0.66bar相當于38%充液率;介質表觀動力粘度隨溫度呈指數(shù)為負1.8系數(shù)K為與充液率有關的冪函數(shù)關系,K與充液率是系數(shù)為0.4523的線性正相關關系,并驗證了是正確的;液力緩速器制動扭矩都是隨工作介質表觀動力粘度的減小而增大的,但減小的方式和介質的流變特性有關;液力緩速器制動扭矩與介質密度間存在線性的正相關關系。
[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.
【學位授予單位】：華南農(nóng)業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：U463.5
，
本文編號：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.
【學位授予單位】：華南農(nóng)業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：U463.5
，
本文編號：2232117
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