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R-134a를 사용한 자동차용 스크롤 압축기의 스크롤 형상변화가 성능에 미치는 영향
이건호,김학수,조금남,유정열,Lee, Geonho,Kim, Haksoo,Cho, Keumnam,Yoo, Jungyul 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.11
The present study investigated the effects of geometric parameters considered on the performance of an automotive scroll compressor by assuming ideal, semi-real and real gases for R-134a. The geometric parameters were center thickness of scroll, height of scroll and the size of discharge port. Fourth-order Runge-Kutta method was applied to solve the thermodynamic equations, leaking rate equation and the equation of motion of discharge valve for ideal, semi-real, and real gases. The volumetric and adiabatic efficiencies for semi-real and real gases differed little, but those for ideal gas differed by 18% and 25% compared with those for real gas at 2,000rpm. The volumetric efficiency changed little as the design angle of scroll (${\gamma}$) changed, but the adiabatic efficiency at ${\gamma}$ of $34^{\circ}$ was higher by 2.4% than that of $147^{\circ}$ for 2,000rpm. The volumetric and adiabatic efficiencies at scroll height of 29.8mm were higher by 1.7% and 2.8% than those of 65.8mm. The volumetric efficiency changed little as the size of discharge port changed, but the adiabatic efficiency increased a little as the size of discharge port decreased.
자유 낙하하는 실린더 주위의 층류 유동에서 St-Re 관계
남궁각(Kak NamKoong),최형권(HyoungGwon Choi),유정열(JungYul Yoo) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.9
In the FSI (Fluid-Structure Interaction) problems, two different governing equations are to be solved together. One is for fluid and the other for structure. Furthermore, a kinematic constraint should be imposed along the boundary between the fluid and structure. We use the combined formulation (Hesla, 1991) which incorporates both the fluid and structure equations of motion into a single coupled variational equation so that it is not necessary to calculate the fluid force on the surface of structure explicitly when solving the equations of motion of the structure. Before treating complex FSI problems, laminar flow around a freely-falling cylinder is considered. The Navier-Stokes equations are solved using a P2P1 Galerkin finite element formulation with ALE (Arbitrary Lagrangian-Eulerian) algorithm and Newton’s equations of motion for cylinder are solved. The adaptive mesh refinement technique is also adopted which uses stress error as a posteriori error estimator together with an efficient variable-reordering and element-reordering method for unstructured finite element meshes. The numerical simulation results reveal the effect of vortex shedding on the motion of a falling cylinder. The cylinder falls oscillating in the spanwise direction and rotating about the center. A correlation of St-Re relationship for a freely-falling cylinder is to be proposed from the numerical data of the present study.