Numerical Modelling of a Suction Reed Valve from a Reciprocating Compressor using Fluid Structure Interaction: Master’s Thesis in Process Engineering and Combustion Technology
Authors
Hansen, Rasmus Frost ; Fornitz, Kasper Holst
Term
4. semester
Education
Publication year
2018
Submitted on
2018-06-07
Pages
79
Abstract
Dette projekt, foreslået af Nidec Global Appliance Germany GmbH, undersøger, om computersimulering kan gøre udviklingen af hermetisk lukkede stempelkompressorer hurtigere. Fokus er på den dynamiske respons af sugeventilen, som lader gas strømme ind i kompressoren i hver cyklus. Der opbygges to modeller. For det første en forenklet klumpet parametermodel baseret på ustationære (tidsvarierende) ventilstrømningsligninger, implementeret i MATLAB. For det andet en todimensionel plan CFD/FSI-model i ANSYS Fluent, hvor CFD (beregningsfluiddynamik) kobles med FSI (fluid-struktur-interaktion). Et dynamisk net bruges til at beskrive stempelbevægelse og ventilens forskydning. Da der ikke var eksperimentelle data, sammenlignes begge modeller med resultater fra simuleringsprogrammet KV-DYN. En direkte sammenligning mellem CFD/FSI-modellen og den klumpede model udføres ikke, da den klumpede model er stærkt forenklet. Den klumpede model kan genskabe nogle træk ved kompressorcyklussen og i mindre grad sugeventilens dynamik. CFD/FSI-modellen beskriver de ustationære strømningsfænomener i ventilkanalerne og gennem kompressorcyklussen. Med yderligere forbedringer kan modellerne anvendes i designfasen af kompressorer.
This thesis, proposed by Nidec Global Appliance Germany GmbH, investigates whether computer simulation can speed up the development of hermetically sealed reciprocating compressors. It focuses on the dynamic response of the suction valve, which lets gas enter the compressor during each cycle. Two models are built. First, a simplified lumped-parameter model based on unsteady (time-varying) valve flow equations is implemented in MATLAB. Second, a two-dimensional planar CFD/FSI model is created in ANSYS Fluent, where CFD (computational fluid dynamics) is coupled with FSI (fluid-structure interaction). A dynamic mesh is used to represent piston motion and valve displacement. Because no experimental data were available, results from both models are compared with the KV-DYN simulation program. A direct comparison between the CFD/FSI model and the lumped model is not attempted, since the lumped model is highly simplified. The lumped model reproduces some aspects of the compressor cycle and, to a lesser extent, the suction valve’s dynamics. The CFD/FSI model resolves unsteady flow in the valve channels and across the compressor cycle. With further improvements, these models could be used in the design phase of compressors.
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