Method for predicting the flow rate of reaction gas in fuel cell and System thereof

본 발명은 연료전지의 스택에 공급되는 반응가스의 유량이 연료전지의 각 단위전지마다 균일하게 되도록 반응가스의 유량을 예측하는 방법에 관한 것이다. 본 명세서에서 개시하는 반응가스의 유량 예측 방법은 (a)연료전지의 매니폴드 격자의 입구(inlet)와 출구(outlet)에서의 반응가스의 압력 변화 값(ΔPman)을 도출하는 단계; (b)상기 연료전지의 각 단위전지에 공급되는 반응가스에 대한 소비되는 반응가스의 비(흐름율, mass flow rate)와 각 단위전지의 두 극의 입구와 출구 간 반응가스의 압력 변화 값(압력 강하 값, pressure drop)의 상관관계로부터 상기 흐름율을 산출하는 식을 도출하는 단계; 및 (c)상기 각 단위전지에서의 흐름율이 일치하는 경우에는 일치된 흐름율을 이용하여 상기 각 단위전지에 유입되는 반응가스의 유량으로 예측하고, 일치하지 아니하는 경우에는 상기 (a)단계로 회귀하여 상기 각 단위전지에서의 흐름율이 일치할 때까지 재 예측 제어하는 단계를 포함하여 본 방법 발명이 해결하고자 하는 과제를 해결한다

Calculation of three-dimensional boundary layer near the plane of symmetry of an automobile configuration

The finite-difference three-dimensional boundary layer procedure of Chang and Patel is modified and applied to solve the boundary layer development on the automobile surface. The inviscid pressure distribution needed to solve the boundary layer equations is obtained by using a low order panel method. The plane of symmetry boundary layer exhibits the strong streamline divergence up to the midbody and convergence thereafter. The streamline divergence in front of the windshield helps the boundary layer to overcome the sever adverse pressure gradient and avoid the separation. The relaxation of the pressure right after the top of the wind-shield, on the other hand, makes the overly thinned boundary layer to readjust and prompts the streamlines to converge into the symmetry plane before the external streamlines do. The three-dimensional characteristics are less apparent after the midbody and the boundary layer is similar to that of the two-dimensional flow. The results of the off-plane-of-symmetry boundary layer are also presented

Comparison of Various Turbulence Models for the Calculation of Turbulent Swirling Jets

Comprehensive numberical computations have been made for four turbulent swirling jets with and without recirculation to critically evaluate the accuracy and universality of several exising turbulence models as well as of the modified k-.epsilon. model proposed in the present study. A numerical scheme based on the full Navier-Stoke equations ha been developed and used for this purpose. Inlet conditions are given by experiments, whenever possible, to minimize the error due to incorrect initial conditions. The standard k-.epsilon. model performs well for the strongly swirling jets with recirculation while it underpredicts the influence of swirl for weakly swirling jets. Rodis swirl correction and algebraic stress model do not exhibit universality for the swirling jets. The present modified k-.epsilon. model derived from algebraic stress model accounts for anisotropy and streamline curvature effect on turbulence. This model performs consistently better than others for all cases. It may be because these flows have a strong dependence of stresses on the local strain of the mean flow. The predictions of truculence intensities indicate that this model successfully reflect the curvature effect in swirling jets, i.e. the stabilizing and destabilizing effects of swirl on turbulence transport

Transonic Flow Analysis for Wing-Body-Tail Combination Using Small Disturbance Equation

Transonic flow field analysis of wing-body-tail combination was attempted by modifying the existing code, known as WIBCO, written for the analysis of wing-body combination, which was based on small disturbance equation.The results obtained from the new code were both phsical and reasonable when compared to the results obtained from the original code. The directions and ideas to modify the code with more flexibility to calculate various combinations have been pointed out

Comparative Study between the Centered Scheme and the Upwind Scheme for a Shock-Wave/Turbulent-Boundary-Layer Interaction

A comparative study of three different centered schemes (Beam-Warming, SIAF and LU-SGS) and an upwind scheme in computing the shock-wave/turbulent-boundary-layer interaction phenomena is made over a two-dimensional compression corner. The Baldwin-Lomax mixing length model is adopted to dosed the turbulent shear stress in the mass-averaged, two-dimensional compressible Navier-Stokes equations. Computations are performed for a Mach number of 2.90 with the Reynolds number Reδ (based on the incoming boundary layer thickness) of 1.6×106 for α=16 ramp. The upwind scheme is found to yield oscillation-free solutions around the shock while all of the centered schemes give oscillatory solutions. The present study leads us to believe that any centered difference scheme using scalar artificial dissipation should be suspect in predicting the shock-wave/turbulent-boundary-layer interaction problem