Ruoyu Deng

Numerical Study on the Characteristics of Dual-Mode Scramjet Isolator

As one of the most promising propulsive systems in the future, the dual-mode scramjet engine has drawn the attention of many researches. Detailed flow features concerned with the isolator play an important role in the dual-mode scramjet system. The 2D numerical method has been used for the dual-mode scramjet with wind tunnel. To validate the ability of the numerical model, numerical results have been compared with the experimental results. Overall pressure distributions show quite good match with the experimental results. Back pressure has been studied for maximum pressure rising. According to the results, pressure distribution of supersonic inlet section is not influenced by back pressure. The shock train is pushed towards upstream as the back pressure increases. The maximum value of back pressure without inlet unstart goes up rapidly and then keeps constant when the isolator length increases. The optimal length of isolator section (L/H th ) is 8.7 in this model.

Numerical Visualization of the Pseudo-Shock Waves using LES

The interaction between a normal shock wave and a boundary layer along a wall surface in internal compressible flows causes a very complicated flow. This interaction region containing shock train and mixing region is called as pseudo-shock waves. Pseudo-shock waves in the divergent part of a rectangular nozzle have been investigated by using large-eddy simulation (LES). LES studies have been done for the complex flow phenomena of three-dimensional pseudo-shock waves. The LES results have been validated against experimental wall-pressure measurements. The LES results are in good agreement with experimental results. Pseudo-shock length and corner separation have been studied in three-dimensional LES model. Comparison of centerline pressure measurement and 3D visualization measurement has been discussed for the corner separation position. It has been concluded that the pseudo-shock length should be measured by using 3D visualization measurement.

Flow Rate Prediction of Pneumatic Pipe System Using Concept of Conductance

* Dept. of Mechanical Engineering, Andong Nat’l Univ. (Received January 23, 2014 ; Revised March 10, 2014 ; Accepted March 12, 2014)Key Words: Conductance(컨덕턴스), Friction Factor(마찰계수), Penumatic Pipe(공압관), Flow Coefficient(유량계수), Fanno Flow(Fanno 유동)초록: 컨덕턴스는 유동저항의 반대되는 개념으로써, 광범위하게 유동지표로써 현재 사용되고 있다. 하지만, 유동 컨덕턴스 연구들은 지금까지 매우 드물며, 압축 공기의 표준화 장치에 대한 체계적인 연구가 필요하다. 본 연구에서는 2차 방정식 난류모델을 이용한 압축성 N-S 방정식을 적용하여 수치해석적(CFD) 연구를 수행하였다. 본 CFD 결과는 기존의 실험 데이터를 통해 검증되었으며 공압 배관의 입구 및 출구에서의 컨덕턴스와 마찰 계수의 값은 유량을 평가하기 위해 사용되었다. 본 결과는 컨덕턴스가 공압 배관의 입구 및 출구에서의 압력 비율에 의존한다는 것을 보여준다.Abstract: Conductance is a concept contrary to flow resistance and is extensively used as a flow index on how easily fluid is transported through a pneumatic pipe or fluid device. However, research on flow conductance is very rare to date, and a systematic investigation is needed for the standardization of pneumatic devices. In the present study, a computational fluid dynamics method was applied to solve the compressible Navier–Stokes equations with two-equation turbulence models. The present CFD results were validated with existing experimental data. The conductance values and friction factors at the inlet and outlet of a pneumatic pipe were used to assess the flow rates. The present results showed that the conductance depends on the pressure ratio at the inlet and outlet of a pipe.