Simulation and Analysis of Transient Flow of Rolling Rotor Compressor Using Dynamic Grid Technology

Design and Calculation Application Dynamic Grid Technology Simulation Analysis of Transient Flow of Rolling Rotor Compressor Huang Si, Yang Guozhen, Su Lijuan (South China University of Technology, Guangzhou 510640, China) CD dynamic mesh technology for physical deformation and mesh recombination, for cooling type The instantaneous dynamic flow field of the rolling rotor compressor was numerically simulated. The compressed ideal gas can be calculated as the working medium, satisfying the fluid control equation and the gas state equation, and the turbulence model adopts the standard k-e mo type. The harmonic law of the main performance parameters of the compressor changes with time is obtained. Flow field distribution and pressure distribution were observed, and vortex formation in the rolling rotor compressor was observed. movement. Increase or decrease.

1 Introduction Rolling rotor compressors are widely used in air conditioners, heat pumps and refrigerators in recent years due to their small size, simple structure, stable operation and low noise. The utility model utilizes the rotation of the eccentric rotor in the cylinder in combination with the sliding baffle to periodically change the volume of the crescent-shaped cavity, thereby realizing a cycle of inhalation, compression, exhaust and clearance expansion, as shown.

The flow heat transfer process of the rolling rotor compressor is very complicated. Many scholars have done a lot of work for this purpose. The energy analysis of each thermal process is carried out and the heat transfer mathematical model of the compressor is established. The sliding speed of the sliding baffle is approximately: V =e(6)e-rotor eccentricity, mm take e=w eccentric rotor speed n=15ormn rotation period is T=0.04S select time step Afe=000005S set inlet and outlet as pressure boundary conditions, ambient temperature and solid boundary The temperature is set to a constant temperature of 25 ° C. 32 calculation domain definition and dynamic grid settings in the selection of the flow space from the air inlet to the exhaust port as a calculation domain. Since the rotation of the eccentric rotor about the axis O and the translation of the sliding baffle along the guiding groove are synchronous, the deformation and displacement of the calculation domain and the mesh with time are very significant, and the existing CFD technology can only achieve this by using the moving mesh. Dynamic simulation under conditions.

The method of moving the mesh is: when the rotor rotates less, each side of the mesh around the rotor is seen as a spring, with slight deformation of the rotor; when the deformation is large, the mesh around the rotor deforms beyond a certain limit. At the time, the overall grid needs to be reorganized. The pre-processed GabtE computational domain of the FLUENT flow software is used for unstructured meshing, as shown.

Calculating the change of the domain dynamic mesh with time defines the eccentric rotor and the sliding baffle as the moving boundary, and eccentrically rotates the size direction. The initial mesh of the computational domain is a relatively regular deformation and recombination that is constantly changing, as shown by (d).

The 33 numerical solution is solved in FLENT using the finite volume method, and the pressure term is PRESTO! The format is discrete, the diffusion term is discretized by the central difference scheme, the other terms are discretized by the second-order upwind style, and the pressure-velocity coupling equation is solved by the PIS) algorithm.

4 calculation results and analysis, 4 respectively give the compressor intake and exhaust mass flow with time curve. It can be seen from the figure that after a period of starting time 哟 1/4 rotation period, the gas mass flow rate is in the range of 0~015kg), the cycle changes with time, that is, the flow enters a relatively stable stage. . When the rotor is at the position of 9=0°, the mass flow rate of the inlet and outlet is 0 (point 1 in the figure), indicating that the exhaust of the previous cycle is over, the next cycle of suction is about to start; when the rotor is at the position of 9=90°, The compressor simultaneously performs the intake, compression and exhaust processes, and the mass flow value reaches half of the maximum value (point 2 in the figure). When the rotor is at the position of 0=180°, the intake and exhaust volumes of the compressor reach the maximum value ( Point 3) When the rotor is in the 0=270 position, the compressor completes compression, while the intake and exhaust processes are performed. The inlet and outlet mass flow values ​​reach half of the maximum midpoint. 4) The flow curve of 4 is available. Calculate the maximum and minimum mass flow difference of one cycle of the compressor: 25kg/range change, obvious vortex motion, increase or decrease in the suction zone (left side of the cylinder) and the right side of the exhaust pipe. From the change in static pressure distribution, during a rotor rotation cycle, the cycle of compressor suction, compression, exhaust, and clearance expansion is shown. Since the ambient and solid boundary temperatures are set to constant temperature, the calculated gas temperature difference of the compressor is between 1 and 2 ° C, so it can be approximated as an isothermal cycle.

The gas static pressure distribution of the compressor at different rotor positions 5 Conclusion The dynamic simulation of the dynamic flow field of the rolling rotor compressor is realized by CD moving grid technology, and the harmonic law of the compressor flow value changes with time is obtained. The average mass flow rate of the cycle is approximately equal to the peak difference of 06 times; the application of the moving grid technology can capture the obvious vortices in the process of suction, compression and exhaust of the rolling rotor compressor, and the generation and movement of these vortices can be observed. The process of increasing or decreasing these results can be provided for the optimal design and operation of the rolling rotor compressor.

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