【作者】 潘孝斌；

【导师】 李小宁；

【作者基本信息】 南京理工大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 在工业自动化领域,气动真空吸取技术有着广泛的应用,射流式真空发生器是分布式真空吸取系统的核心元件,它根据拉瓦尔喷管原理进行工作。在工作时,压缩气体直接由入口射向出口且必须持续供气,因而效率低、耗气量大。为了应对这一问题,一种新型的活塞式结构的气动真空发生器的研究应运而生。在论文中,针对活塞式真空发生器原理性样机在响应时间、耗气量等方面存在的不足,研究解决了如何实现快速响应低耗气的技术问题,论文的研究对实现气动真空系统节能具有重要的研究意义和工程应用价值。为了实现这个目标,文中对涉及的问题进行了深入的分析。首先,对PVG原理性样机的基本性能进行了测试,结果表明,PVG原理性样机主要在真空响应时间和耗气量这两个主要性能指标上与同级别射流式真空发生器存在较大差距。为此,在论文中通过对活塞式真空发生器主要性能指标影响因素的分析,以减少系统真空响应时间为目标,研究提出了采用低压损切换结构、真空腔室开启平衡气道、不等径活塞设计的改进措施,提出了兼具快速响应低耗气特点的活塞式真空发生器的总体结构(PVG-R),为展开进一步的理论和试验研究奠定了基础。为了分析PVG-R系统动态响应特性,以及主要结构参数和供给压力对系统主要性能指标的影响,导出了各腔室气体流动过程的能量方程,再结合质量流量方程和活塞运动方程,建立了PVG-R系统数学模型,然后进行了仿真研究。仿真结果表明,增加活塞运动行程、适当减小驱动腔直径有利于提高系统的极限真空度和减少系统响应时间;在满足系统响应时间的前提下,降低系统供给压力有利于减少系统的供给流量和耗气量。在此基础上,设计了新结构的PVG-R原型样机,对PVG-R原型样机的基本性能进行了测试。通过试验研究了主要结构参数、供给压力对系统性能指标的影响,对系统结构参数进行了优化,再结合抽气流道流场仿真分析和试验研究,确定了系统的结构参数。试验结果表明,在50L/min的供给流量下,PVG-R原型样机的极限真空度约为93kPa,高于同级别ZH1OD型射流式真空发生器91kPa和PVG原理性样机的85kPa,抽取1L真空容器真空度达80kPa时的响应时间约为3.70s,较同级别ZH1OD型射流式的4.80s和PVG原理性样机的12.60s分别减少了约22.9%和70.6%。在供给流量一定的条件下,减少了真空响应时间,也就减少了真空响应过程的耗气量。最后,为了进一步减少活塞式真空发生器在真空维持阶段的耗气量,提出并实现了阶梯式供给流量控制技术。根据活塞式真空发生器的基本工作原理,深入分析了系统结构参数、工况参数与真空响应过程的相互影响关系,找出了在不降低其它性能指标的前提下,最大限度地减少真空维持阶段供给流量的技术途径。在本文研究的PVG-R总体结构基础上,提出了PVG-RL总体结构,设计了内嵌有经济、小型的阶梯式流量控制阀的PVG-RL原型样机,进行了试验研究。试验结果表明,与同级别ZH1OD型射流式真空发生器相比,PVG-RL原型样机不仅能够迅速达到要求的真空度,而且有效地减少了工作过程中的耗气量;在真空维持阶段的供给流量最低可降至12L/min,在工作时间60s内,可节省耗气量约71.3%,实现了课题提出的快速响应低耗气活塞式真空发生器的研制目标。更多还原

【Abstract】 In the flied of industrial automation, pneumatic vacuum technology is used wildly. The vacuum ejector which based on principle of Laval nozzles is a key component in a distributed vacuum system. According to the working principle of vacuum ejector, compressed air need to be ejected directly from inlet to outlet and must be maintained for keeping a certain vacuum. The vacuum ejector has to consume large compressed air and inefficient in application. Therefore, it has great significance to research a new kind of pneumatic vacuum generator to save energy and a kind of piston vacuum generator(PVG) is emerged. Aganinst with its insufficient in vacuum response time and air consumption, the technical problem about how to meet the demands of rapid reponse and less air consumption is solved in the paper. The research of the paper is significant in pneumatic vacuum system energy saving. To achieve this goal, some interrelated technical matters are researched in this paper.Firstly, the performences of PVG principle prototype are tested. The results show that, compared with ZH10D vacuum ejector, the performances of PVG prototype is insufficient mainly in response time and air consumption. Through analysis of influence factors on main performances and for improving the system main performances, under measures are taken: few pressure loss pumping control valve, pressure balance way in vacuum cavity and two different diameters pistons. The general structure scheme of piston vacuum generator with the characteristics of rapid response and less air consumption is proposed and named as PVG-R. It established the foundation for further theoretical and experimental studies.To know dynamic response characteristics of PVG-R and the influence of main structure parameters and supply pressure on system performance, the energy equation of each cavity is deduced, and with mass flow equation and piston dynamic equation, the system mathematical model is set up and simulated. The simulation results indicate that increasing piston stroke and reducing driving chamber diameter properly would be favor to increase maximum vacuum and reduce response time, and the supply pressure should be decrease to reduce air consumption while meeting the requirement of response time.Based on these, the PVG-R prototype is designed and tested. Through the experimental research, the influence of main structure parameters and supply pressure are studied. With the flow flied simulation of pumping channel, the optimized design parameters are obtained. Experimental results show that the maximum vacuum of PVG-R prototype is about 93kPa, a little higher than ZH10D’s, and the response time is about 3.70s under the condition of flow rate 50L/min. less than ZH10D’s 4.80s and PVG prototype’s 12.60s about 22.9% and 70.6%. Under the condition of same flow rate, response time reduction is mean to air consumption reduction.Finally, in order to save air consumption of piston vacuum generator during the course of vacuum holding, the stepped flow rate control method is proposed and realized. Based on working principle of PVG-R, the relationships of system structure parameters, working parameters and system vacuum response process are deduced theoretically. And the technocal approach which can reduce flow rate as much as during vacuum holding under the condition of keep other performances. On the base of PVG-R, the PVG-RL prototype, embedded low cost and small stepped flow rate control valve, is designed and tested. Experimental results show that, compared with ZH10D, the PVG-RL prototype can not only reach required vacuum quickly, but also save air consumption greatly. Under the same working condition, the minmaum flow rate of the PVG-RL prototype can reduce to 12L/min during the vacuum holding. It can save air consumption about 71.3% in 60s and meet the requirement of the subject.更多还原