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Modeling a spool compressor using a coupled fluid and solid solver with cut-cell based CFD methodology with adaptive mesh refinement.

Number: 1140

Author(s) : WAIKAR A., ROWINSKI D., KEMP G., OROSZ J., BRADSHAW C.

Summary

The novel spool compressor provides a new rotating compression mechanism with applications in residential and commercial air conditioning systems. The spool compressor features a rotor and a constrained sliding vane which create a positive-displacement compression process. An array of poppet valves allows for the discharge of the compressed fluid. The combination of the suction process, the compression process, and the discharge process exhibit a strong degree of interdependence on the fluid flow and the motion of the components. It is essential to understand this complex fluid flow and its interaction with the moving components inside the compressor to improve its design and efficiency. Computational Fluid Dynamics (CFD) has been increasingly used for the design and analysis of compressors. The spool compressor’s interconnected components undergo both translation and rotation, and the valve motion is dependent on the flow field. These factors make the process of defining the computational grid on which the governing equations are solved highly non-trivial. Furthermore, in these models, it is imperative to ensure the grid discretization yields a sufficiently small numerical error relative to the experimental, modeling, and gross error.
This paper deals with the development and application of a CFD model for a spool compressor. An automatic meshing approach is used to tackle the challenge of moving geometries. Furthermore, adaptive mesh refinement is used to dynamically change the mesh based on local velocity and temperature at each time step. Thus, the Cartesian cut-cell based meshing requires no user meshing, with the mesh concentrated in the regions of large gradients. An explicit coupled approach is used to account for the fluid-structure interaction between valves and the flow field. The displacement of each of the valves is constrained in one dimension along the valve post. The fluid is solved using a finite volume approach, whereas equations of rigid body motion are used to solve for the valve motion of an arbitrary number of discharge valves. The working fluid used for the simulation is R134a. Experimental data for mass flow rate, torque, and pressure traces at various locations is used to validate the CFD model. The results from the simulation show good agreement for the global quantities of mass flow rate and power for nearly all mesh sizes, while the instantaneous pressure traces show more sensitivity to the grid size. An appropriately fine interior mesh can resolve the internal pressure fluctuations. Furthermore, the three-dimensional flow field provides insight into valve lifts and flow across the vane tip, as well as the process efficiency.

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  • Original title: Modeling a spool compressor using a coupled fluid and solid solver with cut-cell based CFD methodology with adaptive mesh refinement.
  • Record ID : 30030268
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 26th International Compressor Engineering Conference at Purdue.
  • Publication date: 2022/07/15

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