Investigation Into The Noise Characteristics In Integrated Electro-hydraulic Power Unit

At present, the traditional hydraulic power unit constitutes of electric motor asprime motor is mainly discrete structure, which consists of motor, coupling, pump andtank. Many defects such as complex structure, low efficiency, high noise, potentialexternal leakage in the traditional hydraulic power unit limit its use and development. Anovel design which called the Integrated Motor-vane Pump Hydraulic Power Unit(IMHU) was put forward in this thesis. The electric motor, port-plate centrifugal pump,vane pump, tank and other accessories are combined as a whole unit. IMHU possessmany advantages such as the compact in dimension, lower noise and no externalleakage. It is an important development direction in hydraulic power unit at present.In this thesis, Computational Fluid Dynamic (CFD), theoretical analysis andexperimental analysis methods combined were to used investigate the noisecharacteristics in IMHU. It was found that the port-plate centrifugal pump increased inthe inlet channel has the obvious effects on improving the inlet pressure of the mainpump. By the CFD technology, the structural parameters of the port-plate centrifugalpump were optimized to further increase the inlet pressure more, improve the suctionperformance of the main pump and avoid cavitation. At the same time, the internalhydrodynamic supporting structure was optimized by CFD. A new test rig was set upand used to measure the internal pressure distribution and noise of the secondgeneration motor vane pump prototype in IMHU. The research results presented in thisthesis have showed the importance reference value for design and manufacture of theintegrated electro-hydraulic power unit.The main content of this thesis:In chapter1, the background and significance of this thesis is presented. Thehistory and current research progress on electro-hydraulic power unit are reviewed. Theresearch works and current progresses on hydraulic power unit noise was speciallysummarized. Lastly, the main research subjects are presented.In chapter2, a design of the Integrated Motor-vane Pump Hydraulic Power Unit(IMHU) was proposed, and its working principle was expounded. The basic theory of acoustics was presented in this thesis. Lastly, reasons of noise generating in IMHU wereanalyzed.In chapter3, the flow field of the inlet channel including port-plate centrifugalpump and hydrodynamic supporting structure of IMHU was simulated by usingFLUENT software. The results showed that the effects on improving inlet pressure ofmain pump were best under the centrifuge tube diameter of φ13mm and centrifugetube number of5. The hydrodynamic supporting structure had a significant auxiliarysupport effect on motor rotor. When the internal angleβwas greater than1o, the axialhigh pressure area was larger than the low pressure.In chapter4, a new test rig was set up and used to measure the internal pressuredistribution and noise of the second generation motor vane pump prototype in IMHU.Experimental results showed that the inlet pressure value of the second generationmotor vane pump prototype was obviously bigger than its internal pressure value, andthe internal pressure near the back pump cover was higher than the pressure at othersites. Compared with the motor-pump combination with the same power, the noise levelof this prototype is lower obviously, and under the output pressure of14MPa, its noiselevel decrease by12dB. In additional, the noise of the second motor vane pumpprototype is mainly for the low frequency noise, and its cavitation was eliminatedcompletely.At the end, some conclusions in this thesis are summarized and the futureresearch proposals are suggested.