Two-stage centrifugal unit and intermediate vapor compensation control method thereof

Abstract

The invention discloses a two-stage centrifugal unit and an intermediate vapor compensation control method of the two-stage centrifugal unit. The two-stage centrifugal unit comprises a two-stage centrifugal compressor, an evaporator, a condenser, an economizer and a gulp valve. The control method comprises the following steps that 1, the second-stage suction vapor superheat degree at a second-stage vapor suction port is acquired, or the second-stage exhaust vapor superheat degree at a second-stage vapor exhaust port is acquired; 2, whether the second-stage suction vapor superheat degree is lower than a preset lower limit value of the suction vapor superheat degree or not is judged, or whether the second-stage exhaust vapor superheat degree is lower than a preset lower limit value of the exhaust vapor superheat degree or not is judged; and 3, if the second-stage suction vapor superheat degree is lower than the preset lower limit value of the suction vapor superheat degree or the second-stage exhaust vapor superheat degree is lower than the preset lower limit value of the exhaust vapor superheat degree, the opening degree of the gulp valve is controlled to be smaller. According to the control method, high-efficiency vapor compensation to the middle of the compressor can be guaranteed to the maximum extent, and meanwhile, the situation that the reliability of the operation of thetwo-stage centrifugal unit under the variable working conditions is influenced due to liquid entrainment in the vapor is prevented.

Description

technical field [0001] The invention relates to the technical field of refrigeration, in particular to an intermediate gas supply control method of a double-stage centrifugal unit and a double-stage centrifugal unit. Background technique [0002] Double-machine centrifugal compressors usually use two-stage throttling and intermediate air supply to carry out system circulation. However, if the intermediate air supply is filled with liquid, it is easy to damage the impeller or cause oil leakage due to seal leakage. [0003] In related technologies, it is usually considered to adjust the air supply valve to an appropriate opening to operate, and to use the shock resistance characteristics of the unit itself to operate. However, for the frequency conversion unit, due to its operating conditions and unit load changes, the operating parameters of the unit itself change complicatedly. Under some special loads such as low-frequency operation, the exhaust superheat of the unit itself...

AI Technical Summary

Problems solved by technology

However, for the frequency conversion unit, due to its operating conditions and unit load changes, the operating parameters of the unit itself change complicatedly. Under some special loads such as low-frequency operation, the exhaust superheat of the unit itself is not high, which will further increase If this risk is increased, it is not conducive to the reliability of the unit operation

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