The Mechanism Discuss of Periodic Sound in Rolling Piston Compressor under Low Operating Frequency in Air-conditioner System

With the popularization of the inverter-driven air-conditioner and the requirement of comfort and energy saving, the operating frequency of inverter-driven air-conditioner is lower and lower, even to 1Hz. But when the air-conditioner operates under the frequency of 10Hz, a periodic sound will appear in the air-conditioner outdoor unit, which should be researched and solved. According to the experiment test and theoretical analysis, it is found that the periodic sound is the excited resonance when the valve opens. The resonator is composed by the discharge port of top-flange and discharge cavity which is made up by cylinder, roller, top-flange and bottom-flange. In one cycle the characteristic of the periodic sound is that the sound will be only taken place when the valve opens and the frequency of the sound will be higher and higher with the crank angle increasing. According to the experimental testing about different type compressor and air-conditioner outdoor unit, it is found that this sound exists in every kinds of rolling piston compressor. Using proper muffler and increasing the thickness of the valve could both reduce this periodic sound.