Research On New Energy-saving Vacuum Ejector With Flow Self-regulation

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).