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关键词： 摩擦离合器  

ISBN: (纸本)9787122389961

摘要： 本书以湿式离合器为研究对象，全面、系统地对其进行分析，主要内容包括：对湿式离合器的多种工作特性和工作原理的概述；接合分离过程的转矩和压力的计算；其内部湿式摩擦副温度场的数值仿真和有限元仿真；润滑油在摩擦副表面流动特性，即流场的分析；不同种类摩擦片磨损情况的预判；控制系统的建模及缓冲控制系统的设计；最后再对各个方面的研究做了实际的试验测试，即有关试验台系统的搭建过程。书中采用多种分析和数值仿真类大型软件，分析所用图表较多，内容丰富，涵盖的研究领域较广，可供机械类研究人员和从业人员获取所需知识。

关键词： Oil film   Oil groove structure   Drag torque   Heat dissipation performance   Wet clutch  

摘要： Purpose - This paper aims to design a single and double throat oil groove structure, which can reduce the drag torque of the wet clutch. Design/methodology/approach - A three-dimensional simulation model was established herein using the computational fluid dynamics method. The influence of oil groove structure on the oil film flow field and the drag torque is obtained by a simulation. Findings - Compared with the traditional radial oil groove, the results show that the single throat oil groove structure reduces the drag torque by about 24.59%;the double throat oil groove reduces the drag torque by about 47.27%. As the speed difference increases, the average temperature rise of the oil film of the double throat oil groove is 4 degrees C lower than that of the single throat oil groove, indicating that it has good heat dissipation performance. The analysis results were verified by experimental results. Originality/value - In this paper, the radial oil groove is taken as the reference object, and the structure of the oil groove is designed and improved. The simulation analysis and experiment verify the rule of the influence of the oil groove structure on the drag torque, which provides a new design idea for reducing the drag torque of wet clutch.

关键词： High-speed axial compressor   Casing treatment   Instability inception   Blade loading distribution  

摘要： Flow instability phenomena, such as surge and rotating stall, limit the operating range of compressors. Casing treatment is a commonly used technique to extend the operating range, and some corresponding physical explanations have been proposed for the effects of casing treatment on the flow field in compressors. While there is also a situation that a casing treatment that is effective for one compressor may be useless for another, as a result, which limits the practical application of casing treatments. Based on the knowledge that the radial distribution of blade loading has a great influence on the type of instability inception, a hypothesis is put forward: casing treatment could change the type of instability inception by altering the loading distribution, and the resulting influence on the occurrence of instability may be one of the reasons to explain some unsuccessful tests of casing treatment. This hypothesis is then verified experimentally and numerically in a transonic axial flow compressor operating at a specific speed where the loading of both rotor tip and stator hub is close to each critical value. The results present that casing treatment can alter the type of instability inception by redistributing the blade loading, and thus leads to an earlier part-span stall in the hub region for this compressor. The main concluding remarks in this paper could be practically beneficial for the design of casing treatment in compressors. (C) 2021 Elsevier Masson SAS. All rights reserved.

摘要： Dear Editor, With interest we read the article on the role of proprotein convertase subtilisin/kexin type 9 (PCSK9) in dyslipidaemia in patients with axial spondylarthritis by de Armas-Rillo et al. [1]. The authors found that PCKS9 was downregulated in these patients and, in addition, observed a positive correlation between PCSK9 levels and disease activity. PCSK9 is a plasma protein that is a central regulator of plasma low-density lipoprotein (LDL)-cholesterol (LDL-C) concentration, and induces LDL receptor degradation and thereby hypercholesterolaemia, thus facilitating atherosclerosis development. The role of PCSK9 in inflammatory disorders is well worth investigating; it has long been known that these...

关键词： Friction clutch   Groove shape   Transient heat   Temperature field  

摘要： To examine the influence of the groove shape of a friction disk on the transient temperature field in the engagement process of aviation wet friction clutch, a transient thermal analysis model of friction clutch was established, and the application method of thermal boundary conditions, including the calculation of convective heat transfer coefficient and heat flux density, was studied. The transient heat loading process was established by the partition method of friction disk and steel disk. The temperature characteristics of wet clutch friction pairs with different groove shapes during the engagement process were analyzed and tested on an SAE#2 testing machine. Results show that when the clutch is engaged, the temperature of the friction pair composed of two-way parallel groove, three-way parallel groove, and waffle groove friction disk increases continuously at first and finally decreases slightly;the highest temperature of the friction disk and steel disk is at the ring near the outer ring of the friction disk;and the waffle groove friction disk is more suitable for aviation wet friction clutch.

关键词： 摩擦离合器  

ISBN: (纸本)9787122389961

摘要： 本书主要内容包括对湿式离合器的多种工作特性和工作原理的概述；接合分离过程的转矩和压力的计算；其内部湿式摩擦副温度场的数值仿真和有限元仿真；润滑油在摩擦副表面流动特性，即流场的分析；不同种类摩擦片磨损情况的预判；控制系统的建模及缓冲控制系统的设计；最后再对各个方面的研究做了实际的试验测试，即有关试验台系统的搭建过程。

关键词： biogeography   David Lack   demography   density dependence   fecundity   life‐   history   population regulation   productivity   seasonality  

摘要： One enduring priority for ecologists has been to understand the cause(s) of variation in reproductive effort among species and localities. Avian clutch size generally increases with increasing latitude, both within and across species, but the mechanism(s) driving that pattern continue to generate hypotheses and debate. In 1961, a Ph.D. student at Oxford University, N. Philip Ashmole, proposed the influential hypothesis that clutch size varies in direct proportion to the seasonality of resources available to a population. Ashmole's hypothesis has been widely cited and discussed in the ecological literature. However, misinterpretation and confusion has been common regarding the mechanism that underlies Ashmole's hypothesis and the testable predictions it generates. We review the development of well-known hypotheses to explain clutch size variation with an emphasis on Ashmole's hypothesis. We then discuss and clarify sources of confusion about Ashmole's hypothesis in the literature, summarise existing evidence in support and refutation of the hypothesis, and suggest some under-utilised and novel approaches to test Ashmole's hypothesis and gain an improved understanding of the mechanisms responsible for variation in avian clutch size and fecundity, and life-history evolution in general.

关键词： Automated manual transmission   electro-pneumatic clutch actuator   gain-scheduled control   parameter tuning   PID control  

摘要： This study proposes a gain-scheduled controller with direct tuning for the position control of a pneumatic clutch actuator that is installed in heavy-duty trucks. Pneumatic clutch actuators are highly nonlinear systems and cannot be easily controlled. Industries require a simple controller design that is easy to understand and requires few trial-and-error calibrations. Therefore, we adopted a gain-scheduled proportional integral derivative (PID) control law, which is a well-known and easy-to-understand nonlinear control method. In this approach, a gain scheduler is expressed using polynomials composed of coefficient parameters and controlled object states. The unknown coefficient parameters of the polynomials are directly tuned from the controlled object input/output data without having to use a controlled object model. The proposed controller design procedure is simple and does not require system identification or trial-and-error tuning. The effectiveness of the proposed method is verified by an experiment using an actual vehicle. The experimental results confirm the effectiveness of the proposed method for the position control of pneumatic clutch actuators.

关键词： Magnetorheological (MR) fluid   hybrid multi-plate clutch   torque model   fluid coupling mode   mechanical friction mode  

摘要： Recently, there has been a rising demand for high-performance clutches in mechanical systems owing to the development of industrial technologies. This paper, therefore, proposes a hybrid multi-plate Magnetorheological (MR) clutch that has both fluid coupling and mechanical friction modes. To reduce impact when the plates are in contact with each other, a fluid coupler's operating mode was used at the beginning of the clutch operation. For this, torque modeling in each mode was induced based on the Bingham model of the MRF. Using the induced torque modeling and ANSYS Maxwell's magnetic field analysis results, the design procedure for a multi-plate clutch was implemented. Based on the design results, a hybrid multi-plate MR clutch was manufactured. Finally, the performance of the manufactured MR clutch was evaluated using a torque tester. The assessment confirmed that the proposed torque modeling and simulation results mostly matched the test results.

关键词： 电磁离合器轴承   密封结构   试验   措施  

摘要： 针对电磁离合器轴承在市场使用要求,根据密封结构特点结合实际产品使用中遇到的问题以及改善前与改善后密封件结构对比情况,阐述了一种提高汽车电磁离合器轴承密封性能的措施,并用试验验证该措施的有效性,提高了产品的可靠性。