Improvement of totally enclosed piston compressor to reduce energy consumption and noise

1introduction

　　Compressors are the heart of refrigerators. As people's requirements for refrigerators increase, the energy-saving, low-noise, and environmental protection of compressors will inevitably become the focus of attention of various refrigerator manufacturers. This article introduces the beneficial improvements made by the fully enclosed piston compressor for refrigerators in reducing energy consumption and noise. Since 1996, Gasibela has conducted research on compressor energy consumption, noise and environmental protection issues. Through the exploration and practice in recent years, some experience has been accumulated in this area, and I hope to learn from relevant experts and colleagues.

2Selection of refrigerant

　　With the development of CFC alternative technology in the world, our company started to replace R12 in 1996. Since the ODP value of R134a is 0 and the GWP value is 1000-2900, R134a is incompatible with mineral oil, and polyester oil should be selected. It has strong hygroscopicity and poor thermal stability, and is easily decomposed at 200°C. Water, acid and carbon dioxide corrode metals and put forward higher requirements for the dryness of the system.The ODP value of R600a (isobutane) is 0, and the GWP value is close to 0. It is compatible with mineral oil. The physical properties are slightly different from R12. The refrigeration performance is better than R12. The compressor COP value calculated by the thermal cycle is theoretically higher than R600a. R12, therefore, our company extensively absorbs and draws on international advanced experience, based on its own advantages and actual conditions, the first choice is R600a (isobutane) as the refrigerant.

3Design improvements

Improve the compressor’s air delivery efficiency, that is, reduce energy consumption, and reduce energy consumption. The design of the compressor always keeps improving the compressor’s air delivery coefficient, which can reduce the size and weight of the compressor, and at the same time, it can also reduce the compression. The power consumption of the machine, so as to achieve the purpose of energy saving. At the end of exhaust, when the piston starts to move in the opposite direction, a certain clearance is inevitably left at the top of the cylinder head.During the expansion of the top clearance in the cycle, part of the piston stroke loses the suction effect, so there is a volume coefficient λv in the actual cycle; at the same time, the pressure fluctuations during suction and exhaust, the temperature rise during the suction process, gas leakage and other factors , There are also pressure coefficient λp, leakage coefficient λl, temperature coefficient λT on the gas transmission coefficient.

　　The actual gas transmission coefficient λ can be expressed as λ=λvλpλlλT where λ―――gas transmission coefficient; λv――volume coefficient; λp――pressure coefficient; λl――leakage coefficient; λT――temperature coefficient For small refrigeration compressors for refrigerators, the volume coefficient is the most influential, followed by the temperature coefficient. Therefore, the focus of the improvement of the compressor is to increase the volume coefficient. Reducing the clearance volume, improving the suction and exhaust valve types, such as the use of infinite suction valves, concave valve plates, etc., will improve the efficiency of the compressor. However, the improvement of these performances depends on the perfect technology. Guarantee can be realized. In addition, reducing the exhaust pressure loss and enhancing the cooling of the cylinder wall is also beneficial to the improvement of compressor efficiency.

　　The optimization of the air valve The air valve controls the compressor's suction, compression, exhaust and expansion process. The "tremor" and "delayed closing" in the opening and closing of the valve plate will affect the air delivery of the compressor and increase the compressor. The noise and vibration can damage the valve plate and affect the life of the compressor, so the design of the valve is particularly important. In the design, the structural parameters of the air valve and the movement law of the valve disc must be solved reasonably to minimize the resistance loss. Due to the Mach number of the valve clearance, the force of the gas on the valve changes with the change of the refrigerant. Therefore, for the compressor using R600a as the refrigerant, the structural size of the valve must be re-adjusted in order to reasonably solve the problem. Problems in valve movement. Generally, the suction pressure of the refrigerant is always lower than the discharge pressure, and the suction pressure of R600a is much lower than that of R12, so the lift of the valve plate can be increased. By increasing the lift of the valve plate, the time section of the air valve is increased to reduce the speed of the air flow and reduce the power loss.

　　While reducing noise and improving compressor efficiency, the increase in noise is inevitable, which is a problem that cannot be ignored. These noises include continuous noise and discontinuous noise, periodic and non-periodic noise, which can be attributed to fluid noise, mechanical noise and electromagnetic noise. The most important of these is the optimized adjustment of the suction muffler flow path.