Noise Reduction of Rolling Piston Type Rotary Compressor

This paper refers to the noise reduction of the rolling piston type rotary compressor. In general. as the rolling piston increases its speed under the high compression ratio condition. the noise level increases steeply. We resume that this happens because a certain shock wave is produced in the comPression space. Then we could simulate the Phenomenon by the numerical analysis ( CACE method ) of unsteady one-dimensional flow. As the countermeasure of the shock wave, we formed escape grooves in a wall of the discharge port at an upstream side of the crank angle from the discharge port, and then we could reduce the noise level of the rolling piston type rotary compressor. INTRODUCTION The rolling piston type rotary compressor has been widely used for air conditioners and refregerators. In recent years. in regard to the development of variable-speed rotary compressors, the noise reduction has become a very important problem. The noise reduction of rotary compressors has been examined bY various authors from different Points of view. GenerallY, the following facts have been considered as main causes of the noise .tn<zHlJ 1) The jet flow which is produced when the discharge gas is let out of cylinder chamber 2) The vibration caused by the collision and the sliding between compressor parts 3) The electromagnetic force 550 In some test conditions of compressors, a phenomenon occurred. It could not be explained well by the above causes. It is the phenomenon that the noise and the vibration increase before the discharge valve is forced to open, and before the discharge gas is let out of the cylinder chamber. After having investigated the vibration timing and the pressure pulsation in the cylinder comPression space. we could make sure that the shock wave occurred in the cylinder compression space and that the high frequency pressure pulsation which was caused by the shock wave excited compressor parts. As a result of the countermeasure for the shock wave, we could reduce the noise level of the compressor. ANALYSIS OF NOISE AND VIBRATION Test Compressors And Test Procedures Fig.l and Fig.2 show the constructions of the test compressors. Fig.l shows the construction of the rolling piston type test compressor ( open type one). and we call this one MODEL A. MODEL A is driven by motors or engines. The stroke volume of MODEL A is 79:8( cc/rev ). Table 1 shows the test conditions of MODEL A. Fig.2 shows the construction of the hermetic test compressor, and we call this one MODEL B. MODEL B is used in air coditioners and has the following specifications. Stroke volume : 39.0 ( cc/rev ) Nominal output : 1700 ( w ) And MODEL B was tested by the conditions of table 2. The noise was measured in an anechoic room. In the case of MODEL A. the noise level was measured at a distance of 1 meter from the compressor shell surface. In the case of MODEL B, it was measured at a distance of 50 em from the shell surface. These tests can measure the noise and the vibration of the compresors. At the same time, it is possible to measure the crank angle. the valve displacement and the pressure of the compression space in the cylinder. And signals from the sensors were measured with various B&K instruments and the data were analyzed bY FFT analyzer ( HP5451C ) . Test Results And Discussions Fig.3 shows the test results of MODEL A on the A-3 condition. From Fig.3 we found that there was the high frequency pressure pulsation on the pressure of the compression space in the cylinder. and that