农业工程学报2017，Vol.33Issue(22)：53-60,8.DOI:10.11975/j.issn.1002-6819.2017.22.007
液力减速器空化特征信号量化分析方法与验证
Quantitative analysis method and verification of cavitation characteristic signal of hydraulic retarder
摘要
Abstract
For accurately quantitatively analyzing characteristics threshold of hydraulic retarder cavitation signal and providing a theoretical basis for the structural optimization of hydraulic retarder and avoiding cavitation resulting in the decrease of braking capacity, a test rig is set, which can collect vibration, noise and pressure pulsation signal synchronously. In the test system, different from the original medium, the medium is clear water which does not change the initial conditions of cavitation and is more conducive to observe the development process of cavitation. In addition, clear water is easy to be replaced, so that the test difficulty is reduced. First, we test the external characteristics and conduct the signal acquisition. The pressure in reducer casing is maintained at 0.1 MPa by booster pump, and the drive motor runs at 800, 900, 1000, 1100 and 1200 r/min respectively. Then the high-speed photography is carried out, and the acquisition of rotation rate, torque, temperature, pressure, noise and vibration acceleration signals is performed, followed by a cavitation performance test and its relevant signal acquisition. Next, pressure inside the chamber is reduced to 0.08, 0.06, 0.04, 0.03, 0.02 and 0.01 MPa respectively. Under these 6 different pressure conditions, the experiment steps were the same as those in 0.1 MPa condition. On the base of broadband vibration acceleration and broadband noise level, the principle of calculating the mean sequence of each working condition is used to analyze vibration and noise of hydraulic retarder of 0° blade dip angle quantitatively, as well as the cavitation characteristics signals of pressure fluctuation. Accordingly, the vibration, noise and pressure pulsation signal and the cavitation threshold in characteristic frequency band are determined. In order to facilitate the study of cavitation development degree under the working conditions, this paper introduces the concept of "relative torque" and "change rate"which can ease the difficult of quantification of the test data. The different cavitation stages are divided into 3 types: the non-cavitation stage, the nascent stage and the serious stage. The non-cavitation stage is the stage in which the hydraulic retarder unit is in normal operation and the relative torque change rate is less than 2.0%. The lower rotation rate and the higher pressure allow the cavitation to be suppressed so that the high-speed camera does not capture the obvious empty bubble. At nascent stage, the relative torque change rate is between 2.0% and 5%. As the rotation rate increases and the pressure in the cavity of the hydraulic reducer decreases, the local pressure of the flow field decreases below the saturated vapor pressure. As a result, bubble begins to generate and initial cavitation occurs, and the volume of vacuoles is small and the vacuoles are destroyed immediately. The relative torque change rate at serious stage is greater than 5%. At this stage, the pressure in most areas of the reducer cavity is less than the saturated vapor pressure. As most of the flow path is occupied by the bubbles, the cavities generate at the outer edge. The flow of liquid spreads to the roots of the blades and cavitation fully develops. In order to verify the effectiveness of the quantitative analysis method proposed in this paper, hydraulic retarder of 15° blade dip angle is selected. And through high-speed photography test, the results show that the proposed method of determining the threshold is able to distinguish cavitation state of hydraulic retarder. The cavitation threshold method is universal for this series of hydraulic reducers. The research provides a theoretical basis for the optimization of the structure of the hydraulic reducer.关键词
振动/噪声/信号分析/液力减速器/空化/压力脉动Key words
vibrations/noises/signal analysis/hydraulic retarder/cavitation/pressure fluctuation分类
机械制造引用本文复制引用
董亮,刘嘉伟,刘厚林,肖佳伟,赵宇琪..液力减速器空化特征信号量化分析方法与验证[J].农业工程学报,2017,33(22):53-60,8.基金项目
国家自然科学基金(51509111) （51509111）
中国博士后科学基金资助项目(2017M611721) （2017M611721）
西华大学流体及动力机械教育部重点实验室开放课题资助项目(szjj2017-094) （szjj2017-094）
江苏高校优势学科建设工程资助项目(PAPD) （PAPD）
