Abstract
Hermetic digital scroll compressor has been widely used as a small-scale organic Rankine cycle application in the heating, ventilation, and air conditioning systems. A clunking noise issue is recently found in an air conditioning outdoor unit, and the main cause of the noise is experimentally identified to be the impact of the scrolls in the compressor unit during the switching process. The semi-active control methods are thus designed to greatly reduce the noise level by using additional valves to adjust the pressure changing rate within the modulation chamber. The response time for the impact of the scrolls can then be controlled by the added valves. The additional release valve with a smaller diameter pipe parallel to the main valve is tested firstly for its performance. Slower flow rate is produced and the pipe can extend the response time and decrease the speed of the impact process by reducing the pressure changing rate. The use of a discharge valve is also tested for controlling the pressure changing rate inside the chamber. The discharge valve with an opposite effect to the release valve is found useful for solving the noise issue. Both noise and vibration results confirm that the impact noise in the frequency range of interest can be reduced by using the proposed semi-active control methods.
Highlights
As a small-scale organic Rankine cycle application, hermetic digital scroll compressor has been widely used in the air conditioning due to its advantages of reliability, efficiency, and low cost compared to the inverter type compressor.[1,2,3]
This paper conducted a series of experimental tests for the additional valves designed for the noise control of the digital scroll compressor in an air conditioning unit
The use of a discharge valve was found useful for noise reduction
Summary
As a small-scale organic Rankine cycle application, hermetic digital scroll compressor has been widely used in the air conditioning due to its advantages of reliability, efficiency, and low cost compared to the inverter type compressor.[1,2,3] several models of the digital scroll compressors used in an air conditioning outdoor unit may generate unacceptable levels of clunking noises during operations.Figure 1 shows the schematic of a simplified digital scroll compressor according to the corresponding model designs.[4,5,6] A solenoid valve is used to control the two working states of the compressor, namely loaded and unloaded. When the valve is opened, the modulation chamber holds the pressure at the same level as the suction pressure chamber, and the spring mechanism component within the compressor pushes the up-scroll upwards and separates from the rotating low-scroll. Due to the high pressure difference between the lowpressure suction chamber and the high-pressure modulation chamber, the pressure differential force overcomes the spring force and the up-scroll is pushed downwards and coincides with the low-scroll.
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