本文關(guān)鍵詞： 齒輪泵 空化 空化演變 流體動力學(xué) 空化產(chǎn)熱　出處：《北京理工大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：外嚙合齒輪泵因結(jié)構(gòu)簡單、工作可靠被廣泛應(yīng)用于液壓傳動系統(tǒng)。隨著工業(yè)應(yīng)用和環(huán)境保護要求的提高，，齒輪泵正朝著低噪聲、低流量脈動以及高壓高速化的方向發(fā)展。通常條件下由于回路的背壓有限，入口壓力較低，齒輪泵容易發(fā)生空化，析出的氣體對齒輪泵的工作特性產(chǎn)生不利影響。因此，空化問題是齒輪泵研究中的一個重要方向。本文針對當(dāng)前油液空化模型與齒輪泵流體動力學(xué)仿真模型的不足，圍繞著外嚙合齒輪泵內(nèi)的空化演變過程和空化對齒輪泵工作特性的影響兩條主線展開了系統(tǒng)的研究，運用理論建模、CFD仿真和試驗分析相結(jié)合的研究手段，構(gòu)建了基于集中參數(shù)法的齒輪泵多連通容積空化演變模型，揭示了齒輪泵內(nèi)的空化演變規(guī)律，為進一步提高齒輪泵設(shè)計方法和探究空化與其它物理現(xiàn)象的耦合規(guī)律提供了有力工具，具有重要的理論和工程應(yīng)用價值。 通過考慮油液中空氣析出與消解過程的時變性，建立了密閉容積內(nèi)油氣兩相的動態(tài)空化模型，推導(dǎo)了油液屬性（如密度和有效體積彈性模量）與含氣率之間的本構(gòu)關(guān)系，繼而通過試驗驗證了該模型的有效性，并解釋了密閉容積壓縮膨脹過程中油液密度的“遲滯”現(xiàn)象。研究表明，油液密度主要受質(zhì)量含氣率影響而油液有效體積彈性模量主要受體積含氣率影響；油液膨脹過程中空氣的析出速率要大于壓縮過程中空氣的消解速率。 將密閉容積內(nèi)油氣兩相動態(tài)空化模型推廣至連通容積，綜合考慮容積內(nèi)空氣的析出和消解、相鄰連通容積之間的質(zhì)量交換以及容積自身體積的變化，推導(dǎo)了含氣率微分方程。應(yīng)用該方程建立了泵入口節(jié)流段的集中參數(shù)模型，研究了泵入口兩相臨界流效應(yīng)，進而獲得了喉口直徑、油箱壓力以及空氣析出系數(shù)等對臨界壓力和泵極限供油轉(zhuǎn)速的影響規(guī)律。結(jié)果表明，臨界狀態(tài)下節(jié)流段喉口區(qū)油液的流速等于聲速；減小空氣析出速率對改善齒輪泵空化性能有重要作用。 將外嚙合齒輪泵等效為多個連通的控制容積，建立了基于集中參數(shù)法的齒輪泵多連通容積空化演變模型，分析了氣體在不同齒腔內(nèi)的析出、流動、分布以及消解等演變過程，研究了齒腔內(nèi)油液壓力和含氣率的變化特性，揭示了空化對齒輪泵內(nèi)建壓過程、容積效率以及壓力流量脈動等特性的影響機理。研究表明，齒輪泵空化時內(nèi)部泄漏增加，容積效率降低，出口壓力脈動變大。 最后，研究了空化對齒輪泵開式回路溫升特性的影響。分析了回路中元件對外界的散熱率，結(jié)合氣體在齒輪泵流場中的演變行為，提出了空化產(chǎn)熱的計算方法。利用液壓系統(tǒng)的熱力學(xué)方程，建立了齒輪泵開式回路的熱力學(xué)模型，分析了空化時齒輪泵回路的油溫變化過程，并通過了試驗驗證。研究表明，空化產(chǎn)熱來源于齒輪泵建壓過程中對氣體的壓縮做功，空化使回路中油液溫度上升變快。
[Abstract]:External gear pump has the advantages of simple structure, reliable work is widely used in hydraulic transmission system. With the increase of industrial application and environmental protection requirements, the gear pump is moving towards low noise, low flow pulsation and high speed development direction. Under normal conditions due to the limited pressure loop, entrance pressure is low, easy to gear pump the occurrence of cavitation, adversely affect the working characteristics of precipitation of gas on the gear pump. Therefore, cavitation is an important direction in the study of gear pump. This paper aiming at the deficiency of fluid cavitation model and fluid dynamics simulation model of gear pump, gear pump around the cavitation effect on the characteristic of gear pump the evolution of the two main lines and cavitation are systematically studied, using the theory of modeling, simulation and experimental research method of CFD analysis, constructed the lumped parameter method based on gear The evolving model of pump multi connected volumetric cavitation reveals the evolution law of cavitation in gear pump. It provides a powerful tool for further improving the design method of gear pump and exploring the coupling rule between cavitation and other physical phenomena, which has important theoretical and engineering application value.
By considering the time variability of precipitation and air oil in the digestion process, establishes the dynamic model of gas oil two-phase cavitation within the confined volume, derived oil properties (such as density and effective bulk modulus) and the constitutive relation between the gas holdup, and the validity of the model is verified by experiment, and explain the closed volume compression expansion process of oil density lag. The study shows that the oil density is mainly affected by the quality of gas and effective fluid bulk modulus is mainly affected by the impact of the gas volume rate; oil expansion process air precipitation rate is greater than the compressed air in the process of digestion rate.
The sealed volume of gas oil two-phase dynamic cavitation model is extended to the communication volume, considering the volume of air in the precipitation and digestion, change of mass exchange between adjacent connected volume and volume of their size, derived gas rate differential equation. The lumped parameter model of the pump entrance throttling section has been established using the equation of pump the entrance of two-phase critical flow effect, and then get the influence of throat diameter, tank pressure and air separation coefficient on the critical pressure and pump speed limit control. The results show that the critical state of the throttle section throat oil liquid velocity equal to the velocity; reduce the air release rate has an important role to improve the cavitation performance of gear pump.
The external gear pump is equivalent to multiple connected control volume, a gear pump lumped parameter method based on multi connected volume cavitation evolution model, analyzed the precipitation of gas in different material flow distribution and elimination process, change of oil hydraulic force teeth and gas content. Reveals the cavitation on the gear pump internal pressure process, the influence mechanism of volumetric efficiency and pressure pulsation characteristics. The results show that the gear pump cavitation when the internal leakage increases, the volume efficiency, outlet pressure fluctuation becomes larger.
Finally, study the influence of cavitation rise characteristics of gear pump open loop temperature. Analysis of the circuit components on the outside of the heat dissipation rate, combined with the gas evolution behavior of the gear pump in the flow field, puts forward the calculation method of cavitation heat production. Using the thermodynamic equation of the hydraulic system, a thermodynamic model of a gear pump open loop. Analysis of cavitation temperature of gear pump loop process, and has been verified by experiments. The results show that the compression work of gas from the gear pump cavitation heat pressing process, the temperature of the oil liquid cavitation loop rise faster.

【學(xué)位授予單位】：北京理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TH137.51

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