| Abstract:The development of the national economy promotes concrete pump developing towards high efficient, high pressure, high flow and low impact. And people are concerned on the quality of pumps. As an important cause of noise and vibration, hydraulic shock has became a research hotspot of concrete pump, which would shorten the life of the hydraulic system. This thesis deals with the hydraulic shock in the pumping system of the concrete pump. Reasons that induce the hydraulic impact on switching conditions are investigated, methods that control hydraulic impact are proposed, and simulations and experiments are used to verify the proposed methods.1. Properties, development trends and current research of concrete pumping system are reviewed. Mechanism of hydraulic shock and resultant dangers are analyzed. Research aims for this thesis are specified by reviewing the mechanical of hydraulic impact and methods of its controlling over domestic and international research fields of hydraulic shock.2. Based on operational principles of concrete pumping system, it is found that the major causes for hydraulic impact of pumping system in concrete pump is that the mismatch between the electro-hydraulic valve in pumping system and pumping system itself while reversing and the instantaneous change of load on the hydraulic cylinder. The load characteristics of concrete pumping system are analyzed.3. The theoretical analysis and calculation about hydraulic shocks is maden. The simulation model of concrete pumping system is built by using AMEsim. The effects of reversing time, input flow, pipe parameters and load on the hydraulic shock are investigated and the sensitive factors are found.4. Methods to control the hydraulic impact are put forward and its feasibility as well as effectiveness has been verified. The hydraulic pumping system is improved according to the control method; the control effect of different hydraulic impact control methods is analyzed through AMEsim simulation. The simulating results show that the pumping system which uses double reversing valves and an accumulator produces least hydraulic shock while reversing.5. Tests are conducted on a concrete pump prototype; the simulations are verified correct through the tests. The change of the pressure in the pump inlet and the rod chamber of the pumping cylinder before and after improving the hydraulic system is compared and analyzed. The tests results show that he pumping system which uses double reversing valves and an accumulator produces least hydraulic shock while reversing. |
PDF Full Text Request