INFLUENCE OF THE STIFFNESS ON THE FLUID-STRUCTURE INTERACTION PROBLEM IN A RADIAL DIFFUSER WITH MOVING FRONTAL DISK

André Luís Severino Abrego¹; Ricardo Lopes Ferreira¹; José Luiz Gasche¹

¹ State University of São Paulo, College at Ilha Solteira

doi:10.20906/CPS/COB-2015-0729

Resumo

Hermetic reciprocating compressors are widely used in small and medium size vapor compression refrigeration systems. One of the main parts of this type of compressor is the automatic valve system used to control the suction and discharge processes. The experimental or analytical/numerical study of these processes is very complex, mainly because the occurrence of the fluid-structure interaction problem during the operation of the valves and due to the geometric complexity of the whole system. Thus, simplified models as radial diffusers have been used to represent the valve system. However, the previous works have further simplified the model by considering radial diffusers with fixed frontal disks. In this work, we have improved the radial diffuser model in which the real fluid-structure interaction problem has been experimentally studied by considering moving frontal disks. The flow was characterized by measuring the distance between the disks, the pressure acting on the frontal disk surface, and the Reynolds number of the flow. Tests for constant mass flow rates were accomplished for Reynolds number in the range of 2,000 to 20,000 in increments of 2,000. Three radial diffuser systems with stiffness equal to 1.2, 1.5 and 2.0 N/mm have been tested for a diameter ratio of 1.3. The effective force and flow areas were calculated for all tests. The results also show the relation between the Reynolds number and equilibrium positions, depending on the stiffness of the system. In addition, the effective force area decreases for lower Reynolds numbers. On the other hand, the discharge coefficient increases for increasing Reynolds numbers and the influence of the system stiffness is not much significant. The results can be used for validating numerical CFD codes developed to solve the FSI problem in refrigeration compressor valves.

Palavras-chave: Reciprocating compressors; Radial diffuser; Compressor valves