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CFD simulation and improvement of high-speed twin screw compressors for chillers.

Number: 1171

Author(s) : WANG B., WU X., WANG C., ZHANG Z., MA K., XING Z.

Summary

Twin screw compressors are widely adopted in chiller systems due to their high efficiency, reliability, and low maintenance. Increasing the speed of the compressor can reduce the manufacturing cost and the leakage. However, higher speed brings efficiency decay and noise increase. In our tests, increasing the speed of the original machine directly from 3000 rpm to 5000 rpm reduced the adiabatic efficiency by 7.5% with significant noise. To improve the performance of the twin-screw refrigeration compressor at a high speed of about 5000 rpm, 3D transient full-scale CFD simulations were performed with high-quality moving grids. The simulated results were validated by experiment results. The general non-reflection boundary condition (NRBC) and a damping method were adopted to speed up simulations. The pressure distribution inside the compressor chamber can be distinctly discovered and help guide the compressor design. The design parameters of the rotor, such as rotor configuration, wrap angle, and length ratio, were studied. With more lobes, the discharge pulsation can be reduced with slight performance improvement. The length ratio was optimized, and the relevance of the rotor tip velocity was discovered. Improvement can be made with a higher wrap angle at high speed, and the suction delay can also increase the efficiency at the same level. In addition, a parametric study of the design of the suction and discharge ports was carried out. It was found that a small depth of radial suction space can make the intake flow more directional and increase efficiency. Enlarging the suction port by using an unmatched wrap angle was also found to increase the efficiency. A parametric study of the discharge port with different built-in volume ratios was also performed, and a slightly enlarged port was found to be helpful for reducing the resistance. Utilizing the CFD method, additional improvement potential of screw compressors for chillers at higher speeds can be continually uncovered.

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Pages: 10

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Details

  • Original title: CFD simulation and improvement of high-speed twin screw compressors for chillers.
  • Record ID : 30033057
  • Languages: English
  • Subject: Technology
  • Source: 2024 Purdue Conferences. 27th International Compressor Engineering Conference at Purdue.
  • Publication date: 2024/07/18

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