【作者】 滕燕；

【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， 2007， 博士

【摘要】 真空吸取作为气动自动化作业的一种方式,已在气动系统中得到了广泛的应用。射流式真空发生器是局部配置、间歇工作的真空吸取装置的核心元件。但是,普通的射流式真空发生器由于在工作时需要持续定量供气,空气消耗量很大,相应的能量消耗也很大。因此,研究开发一种既能实现真空快速响应,又能降低耗气量的流量自调式真空发生器具有重要的学术意义和实际的应用需求。围绕这一目标,论文在新型流量自调式射流真空发生器的结构、调节元件驱动技术、流场物理模型和数值分析以及试验等关键技术方面进行了深入研究并取得了相应成果。论文首次提出并实现了一种带可调锥的流量自调式射流真空发生器的新构想,通过调节可调锥的工作位置来调节真空喷管喉部的有效截面积,以实现对供气流量的调节,达到节能的目的。围绕着这一创新构想,研究并实现了流量自调式真空发生器的总体结构,包括可调锥部件、调节驱动部件、气—磁驱动部件等结构,在结构上满足了流量调节和耗气量降低的功能需求。提出并实现了直接利用真空压力获得驱动力的真空反馈—压差致动的驱动力源技术方案以及分隔式共轴环芯气—磁驱动技术方案,解决了高压腔与常压腔之间因密封需求而带来的非接触式驱动的技术问题。为了合理地确定分隔式气—磁驱动结构的设计参数,建立了气—磁驱动结构的动力学模型,通过理论分析和试验获得了该结构主要设计参数及性能参数间的匹配关系。对分隔式气—磁驱动结构进行的性能测试结果表明,所设计的气—磁驱动结构的磁驱动起动时间约为0.06 s,可以满足流量调节元件对调节时间的要求。为了获得设置可调锥后流道内流场参数,合理设计新型真空发生器的相关结构参数,对新结构真空发生器气动理论模型进行了研究,并利用计算流体力学的方法对该型真空发生器变截面流道的二维流场进行了深入的分析,获得了变截面流道结构参数以及可调锥工作状态参数对该型真空发生器流道内超音速流场的影响规律,在此基础上对变截面流道结构尺寸和可调锥工作参数进行了改进,仿真和试验结果显示出了理论分析和改进工作的相应成效。对流量自调式真空发生器进行了原理性验证和基本特性测试,试验结果表明:与普通真空发生器相比在真空产生阶段流量自调式真空发生器具有基本相同的真空响应特性,在真空维持阶段其供气流量明显降低。以真空喷管直径为2mm的流量自调式真空发生器为例,当供气压力为0.55MPa、被抽真空容积为1L时,其真空响应时间约为1.25s,真空维持阶段的供气流量比普通真空发生器节省约14.8%。试验的原型流量自调式真空发生器在真空响应时间和极限真空度方面与目前国际上具有代表性的真空发生器的相应参数大致相当,但耗气量比之有了显著降低,显示出了很好的发展应用前景。所研发的流量自调式射流真空发生器已申请了国家发明专利(专利申请号200610040832.1)。更多还原

【Abstract】 Part-picking by vacuum attraction is a kind of automatic pneumatic operating mode, which has been widely used in pneumatic systems. A jet vacuum ejector is the key component of the vacuum part-picking device which is usually locally installed and intermittently operated. However when working, a continuous constant air supply is required for the normal jet vacuum ejector, so as to lead a large air consumption and a large corresponding energy consumption. Therefore, to solve this problem, it is of great academic importance and practical utilization requirement that a new type of jet vacuum ejector with flow self-regulation is researched and developed, which should realize quick vacuum attraction response and reduce the air consumption. Focusing on this objective, in this dissertation, much research work has been made for the overall structure of the new jet vacuum ejector with flow self-regulation, actuating technology for the regulating components, physical model and numerical computation of the flow field in the jet vacuum ejector and experiment. Some research results have acquired from the research.In the dissertation, for the first time a novel idea about the jet vacuum ejector with flow self-regulation by an adjustable cone is presented and realized. By means of adjusting the working position of the adjustable cone, the effective cross section at the jet nozzle throat could be adjusted so as to realize the smooth regulation of air supply and achieve energy saving. Focusing on this creative idea, the new structure of the jet vacuum ejector with flow self-regulation is researched and implemented, which includes the structures of adjustable cone component, adjusting-actuating component and non-contacting pneumatic-magnetic driving component. The functional requirements of flow adjusting and air consumption reducing are well demanded in the structure.Two key technical schemes are presented and realized. One is the vacuum feedback-differential pressure actuating which directly utilizes the differential pressure between vacuum and atmosphere pressure to produce actuating force and another is chamber-separating pneumatic-magnetic driving with a coaxial magnetic ring- axial structure. Thus the technical problem of non-contacting driving resulted from the sealing requirement between the high pressure chamber and atmosphere pressure has been solved. Then to reasonably determine the design parameters of the pneumatic-magnetic driving structure, the dynamic model of pneumatic-magnetic driving structure is set up. Through theoretical analysis and experiment the match relationship between the main design parameters of pneumatic-magnetic driving structure and the operation functional criteria are acquired. Testing indicates that the starting time is about 0.06s and this is able to meet the adjusting time requirement of flow adjusting component.In order to obtain the physical parameters of the flow field in the new jet channel with adjustable cone and reasonably design the corresponding parameters of new jet vacuum ejector, the theoretical pneumatic kinetic model of the new vacuum ejector is studied and numerical analysis of the two-dimension flow field along the variable cross-section flow channel of the new vacuum ejector is conducted by means of the computational fluid dynamics. Thus the affection law of the structural parameters of variable cross-section flow path and the working state parameters of adjustable cone on the flow field with super-sonic velocity in the new flow channel has been obtained. On this basis, some improvements on the structural sizes and working parameters of the adjustable cone have been implemented. Then the effective results for the theoretical analysis and improvements have been shown by simulation and experiments.In order to make principle verification and basic characteristics measurement for the jet vacuum ejector with flow self-regulation, much verification testing and performance measuring have been made. The overall performance measurement indicates that compared with the normal jet vacuum ejector within the vacuum response stage the new jet vacuum ejector with flow self-regulation has the almost the same vacuum response characteristic and within the vacuum keeping stage the air supply for new one is obviously reduced. Take a new flow self-regulation ejector with a 2 mm diameter of nozzle as example, when supply pressure is 0.55 MPa and vacuum volume is 1L, its vacuum response time is about 1.25 s, air supply is reduced by 14.8 % in the vacuum keeping stage compared to the normal jet vacuum ejector. The vacuum response time and maximum vacuum of the tested prototype jet vacuum ejector with flow self-regulation are equivalent to the relative parameters of the typical jet vacuum ejectors in the world, but the air consumption is obviously reduced. Thus a good developing and applying prospect for the new one is emerged. The researched and developed jet vacuum ejector with flow self-regulation has applied for China Creative Patent (Patent applied number is 200610040832.1).更多还原