Investigation of Speed Matching Affecting Contrarotating Fan’s Performance Using Wireless Sensor Network including Big Data and Numerical Simulation

This paper describes the investigations performed to better understand two-stage rotor speed matching in a contrarotating fan. In addition, this study develops a comprehensive measuring and communication system for a contrarotating fan using ZigBee network. The investigation method is based on three-dimensional RANS simulations; the RANS equations are solved by the numerical method in conjunction with a SST turbulence model. A wireless measurement system using big data method is first designed, and then a comparison is done with experimental measurements to outline the capacity of the numerical method. The results show that when contrarotating fan worked under designed speed, performance of two-stages rotors could not be matched as the designed working condition was deviated. Rotor 1 had huge influences on flow rate characteristics of a contrarotating fan. Rotor 2 was influenced by flow rates significantly. Under large flow rate condition, the power capability of rotor 2 became very weak; under working small flow rate condition, overloading would take place to class II motor. In order to solve the performance mismatch between two stages of CRF under nondesigned working conditions, under small flow rate condition, the priority shall be given to increase of the speed of rotor 1, while the speed of rotor 2 shall be reduced appropriately; under large flow rate condition, the speed of rotor 1 shall be reduced and the speed of rotor 2 shall be increased at the same time.

Numerical Investigation on the Stage Matching in a Multi-Stage Centrifugal Compressor

The performance of a multi-stage centrifugal compressor is commonly generated by stacking the individual stage’s performance in the industry applications, which makes the proper stage matching vital in getting favorable performance of the whole machine. Taking a two-stage centrifugal refrigeration compressor as the research object, this paper numerically investigates the two key problems in the stage matching, i.e. 1) The accuracy of overall performance generated by stacking the individual stages’ performance; 2) Effects of the inlet and outlet flow distortions on the individual stage performance and the axial thrust. It is found that the overall performance of the multi-stage centrifugal compressor predicted by the stage-stacking method generally agrees well with that predicted by the CFD analysis at the small and moderate flow rates, and the difference is getting bigger at the large flow rate. The numerical investigations also show that the effect of inlet distortion on the isentropic efficiency and the total pressure ratio exist mainly at the large flow rate. The radial distortion of the inflow has little influence on the performance, while the circumferential distortion of the inflow affects remarkably. The outlet distortion also has an important influence on the performance of upstream stage. The effect of flow distortions at the inlet and outlet on the impeller thrust is presented as well.