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RISS 인기검색어
- 검색키워드
- 저자 : Ashoke De (검색결과 2 건)
- 무료
- 기관 내 무료
- 유료
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Rahul Kumar Soni,Ashoke De 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3
The strut-based injector has been found to be one of the most promising injector designs for a supersonic combustor, offering enhanced mixing of fuel and air. The mixing and flow field characteristics of the straight (SS) and Tapered strut (TS), with fixed ramp angle and height at freestream Mach number 2 in conjunction with fuel injection at Mach 2.3 have been investigated numerically and reported. In the present investigation, hydrogen (H 2 ) and ethylene (C 2 H 4 ) are injected in oncoming supersonic flow from the back of the strut, where jet to freestream momentum ratio is maintained at 0.79 and 0.69 for H 2 and C 2 H 4 , respectively. The predicted wall static pressure and species mole fractions at various downstream locations are compared with the experimental data for TS case with 0.6 mm jet diameter and found to be in good agreement. Further, the effect of jet diameter and strut geometry on the near field mixing in strut ramp configuration is discussed for both the fuels. The numerical results are assessed based on various parameters for the performance evaluation of different strut ramp configurations. The SS configuration for both the injectant has been found to be an optimum candidate;also it is observed that for higher jet diameter larger combustor length is required to achieve satisfactory near field mixing.
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Alok Mishra,Gaurav Kumar,Ashoke De 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5
Most of the turbulence models in practice are based on the assumption of a linear relation between Reynolds stresses and mean flow strain rates which generally provides a good approximation in case of attached and fully turbulent flows. However, this is seldom the need in most of the engineering problems; the majority of the engineering problems observe flow separation or flow transition. Recent developments in non-linear turbulence models have proven significant improvement in prediction of separated flow due to better resolution of anisotropy in modeled Reynolds stress. The domain of application of this improved RANS model can be extended to flow transitions as well, where the resolution of anisotropy in Reynolds stress is required. For a validation of such kind, a two-dimensional numerical study has been carried out over NACA 0021 with k-w SST model with non-linear correction at Re = 120000 for various angles of attack which experiences the formation of a laminar separation bubble (LSB). A correct prediction of LSB requires an accurate resolution of anisotropy in Reynolds stresses. For comparison with other linear models, the simulations are also performed with k-k l -w (a 3-equation linear transition model), k-w SST (a 2-equation linear model) and Spalart-Allmaras (a 1-equation model). The performance of these models is assessed through aerodynamic lift, drag, pressure and friction coefficients. It is found that the non-linear k-w SST and k-k l -w transition model provide comparable quality of prediction in lift and drag coefficients (in spite of the fact that non-linear k-w SST involves solving less number of transport equation than the transition model) as observed in the experiments whereas k-w SST and SA models under predict the drag coefficient value at low angle of attack due to inability to capture the separation induced transition. It is also observed that the location of laminar separation bubble is captured accurately when non-linear or transition model is used as opposed to the SA or linear SST models, which lack in the ability to predict the same.
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