Propane rolling piston compressor indication diagram measurement and performance analysis

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Under the working conditions of 46, 10, 41, 18, 35 °, it is also necessary to measure the performance of the compressor. The performance test of the refrigeration compressor is carried out according to the relevant provisions of GB5773-2004.

Due to the special nature of the R290, a gas alarm device is also required, which enables a grading alarm and a forced shutdown depending on the amount of leakage.

2 The raw voltage signal collected by the data processing data acquisition device is as shown. This voltage signal has been amplified by the amplifier, including the compression chamber pressure signal, the intermediate pressure signal, the suction chamber pressure signal, the corner and dead center signals, and the valve displacement signal. Although the data acquisition program filters the noise of the acquisition process, there are still some data that deviate significantly from normal values. To this end, the data on the acquired equidistant points is smoothed by the five-point three-dimensional method.

3 Rolling piston compressor indication diagram analysis method The slide of the rolling piston compressor divides the volume between the cylinder and the piston into two parts. When the crankshaft drives the piston to move, a part of the volume is enlarged, the working medium is sucked, and the other part is reduced in volume, and the working medium is compressed or discharged. When the piston rotates to the exhaust port or the trailing edge of the oblique cut of the cylinder, the high pressure gas in the vent hole and the oblique cut expands into the suction chamber in the cylinder. In the early stage of expansion (see a), the suction chamber in the cylinder communicates with the suction port. The gas expansion of the clearance volume on the one hand raises the gas pressure of the suction chamber, and on the other hand, the gas sucked into the suction chamber flows back through the suction port.

In the later stage of expansion (see b), since the recirculation area is small or has been zero, the gas flowing from the clearance volume to the compression chamber only increases the pressure and temperature of the compression chamber. In this process, the volume change of the suction chamber or the compression chamber behind it (i.e., the compression chamber after 360° rotation) is small, and can be approximated to constant volume compression.

In addition to the high-pressure gas expansion in the clearance volume, the internal thermal process, the cooling coefficient and the indicating efficiency of the rolling piston compressor are also the suction resistance and the suction air flow pulsation, the exhaust resistance and the exhaust gas flow pulsation, and the gas in the suction pipe. And the heat transfer of the suction pipe, the heat transfer of the gas in the suction chamber and the cylinder, the heat transfer of the gas in the compression chamber and the cylinder, and the leakage loss of each gap.

The diagram of the rolling piston compressor is significantly different from that of the reciprocating compressor (see). The first reason is that the clearance volume expansion process line is substantially vertical, and the second is that the internal pressure suddenly jumps when the working chamber volume approaches the stroke volume.

Compressor volumetric efficiency can be attributed to. It can be seen that the compressor speed pulsation is large, resulting in a nonlinear relationship between the compressor angle and time. For the rolling piston compressor of R22, the measured angle of rotation is 12° compared to the ideal case. The maximum advance angle is 14.5°. For the rolling piston compressor of R290, the measured angle of rotation is the maximum retardation angle compared with the ideal case. The maximum advance angle of 13.5° is 115°. This diagram will be used for the conversion of p-maps and indicator maps.

The performance comparison of R22 and R290 compressors is shown in Table 1. It can be seen from Table 1 that R290 is close to the R22 compressor, the cooling capacity and the input power drop, and the theoretical unit volume cooling capacity and the unit volume adiabatic work are very close (above, in the figure: long time, long time s respectively for suction At the end of the gas process, there is no suction chamber pressure affected by the expansion of the high pressure gas in the clearance volume, the compression chamber pressure at the beginning of the compression process in the clearance volume and the compression chamber pressure; the nominal suction pressure of the compressor is the nominal compressor The exhaust pressure is the actual effective volume of the compressor; the surface area 1 is the theoretical work of the compressor adiabatic compression; the area 2 is the pressure loss of the compressor suction process; the area 3 is the pressure loss of the exhaust process; the area 4 is the clearance volume high pressure Return loss caused by gas expansion; area 5 is the heat loss caused by leakage and heat transfer during the suction process; area 6 is the clearance volume. The clearance volume caused by the high pressure gas expansion process filling the suction chamber and the subsequent compression chamber Charge loss; area 7 is the heat loss during compression.

The heat loss during the compression process is the clearance volume. The pressure loss of the clearance volume caused by the gas filling process of the suction chamber and the subsequent compression chamber is compared with the indication map divided into five parts. Divided into 7 parts, the clearance volume pressurization loss and the clearance volume return loss are separated from the heat loss in the compression process and the heat loss in the suction process, respectively, as opposed to the loss of the clearance volume from the inhalation process. The heat loss is separated and subdivided into two parts. In this way, the heat loss is divided more finely, which is helpful to clarify the specific cause of the heat loss.

The starting point volume is the area enclosed by the isentropic line I of the actual effective volume Va of the compressor and the ideal intake and exhaust pressure lines, which is the theoretical work of the adiabatic compression of the compressor, and can be performed by the compressor. It can be seen that the end of the compression process is the same as the angle of rotation at the beginning of the exhaust process. During the compression and exhaust process, the working fluid pressure in the cylinder of R22 compressor has obvious high frequency pulsation. The high frequency pulsation does not exist in the R290 compressor. The frequency of the low frequency pulsation during the inhalation process also changes, and the sound velocity of the refrigerant changes. Basically proportional.

The R22 and R290 compressor indication diagrams are as shown. It can be seen from b that the pressure loss during the exhaust of the R290 compressor is significantly smaller than that of the R22 compressor. The relative indicated efficiency loss distribution for the R22, R290 compressors is as shown. It can be seen that the heat loss of the R290 compressor is greater than that of the R22 compressor, which is related to the lower viscosity of the R290 gas and the higher thermal conductivity, which is related to the higher solubility of the experimental lubricant to R290. In order to reduce the leakage loss of the R290 compressor, it is necessary to further control the clearance tolerance. Since the vent hole diameter of the compressor used herein is small compared to the same displacement compressor, the exhaust resistance loss is relatively large, which makes the clearance volume loss relatively small. 2 Experimental R290 compressor, its performance can be improved by reducing the motor power, changing the diameter of the vent hole and controlling the gap.

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