Sooin Jeong

Rotor Blade Sweep Effect on the Performance of a Small Axial Supersonic Impulse Turbine

In this paper, a computational study was conducted in order to investigate the rotor blade sweep effect on the aerodynamics of a small axial supersonic impulse turbine stage. For this purpose, three-dimensional unsteady RANS simulations have been performed with three different rotor blade sweep angles (-15°, 0°, +15°) and the results were compared with each other. Both NTG (No tip gap) and WTG (With tip gap) models were applied to examine the effect on tip leakage flow. As a result of the simulation, the positive sweep model (+15°) showed better performance in relative flow angle, Mach number distribution, entropy rise, and tip leakage mass flow rate compared with no sweep model. With the blade static pressure distribution result, the positive sweep model showed that hub and tip loading was increased and midspan loading was reduced compared with no sweep model while the negative sweep model (-15°) showed the opposite result. The positive sweep model also showed a good aerodynamic performance around the hub region compared with other models. Overall, the positive sweep angle enhanced the turbine efficiency.

An Experimental Study on the Flow Characteristics ofa Supersonic Turbine Cascade as Pressure Ratio

In this paper, a small supersonic wind tunnel was designed and built to study the flow characteristics of a supersonic impulse turbine cascade by experiment. The flow was visualized by means of a single pass Schlieren system. The supersonic cascade with 3-dimensional supersonic nozzle was tested over a wide range of pressure ratio. Highly complicated flow patterns including shocks. nozzle-cascade interaction and shock boundary layer interactions were observed.

A Numerical Study on a Supersonic Turbine Performance Characteristics with Different Nozzle-Rotor Axial Gap Spacings

ABSTRACT In this study, 3-dimensional URANS simulation was performed t o analyze the effect of the nozzle-rotor axial gap spacing of a supersonic impulse turbine on turbine performance. The computations were conducted for four different axial gap cases corresponding to about 6%, 10%, 20% and 30% of the blade height, respectively. The results show a good agreement with previous studies and the turbine efficiency decreases drastically in certain range. It is examined that the turbine performance characteristics could change depending on the influ ence of leading edge shock to the nozzle outlet. It is also found that the entropy rise distribut ions along the span differ from each other. 초 록 본 연구에서는 초음속 충동형 터빈의 노즐과 1단 로터 사이 축 간극 거리를 달리하며 3차원 비정상 유동해석을 수행하고 초음속 터빈의 성능 특성을 분석하였다. 계산결과는 기존의 초음속 터빈 효율 경향과 잘 일치하였으며 특정 축 간극 구간에서 효율의 급격한 감소를 보이고 그 이후에는 큰 변화가 없는 구간이 존재함을 확인하였다. 로터 앞전에서 발생하는 충격파의 영향이 노즐 끝단에 전달이 되는 정도에 따라 터빈 내의 여러 성능 특성이 달라짐을 살펴보았고 터빈 스팬 별 손실 특성에서 축 간극이 커질수록 허브 영역에서의 손실이 증가하고 미드스팬 이상의 영역에서 손실이 감소함을 보였다.Key Words:Turbopump(터보펌프), Supersonic Turbine(초음속 터빈), Nozzle-rotor Axial Gap(노즐-로터 축 간극), Unsteady Flow(비정상 유동), Turbine Performance(터빈 성능)Received 13 March 2015 / Revised 11 May 2015 / Accepted 14 May 2015

A Numerical Study on the Performance Characteristics of a Partial Admission Axial Supersonic Turbine with Swept Rotor Blades

ABSTRACT In this study, we performed three-dimensional CFD analysis to investigate the effect of the rotor blade sweep of a partial admission supersonic turbine on the stage performance and the flow field. The computations are conducted for three different sweep cases, No sweep(NSW), Backward sweep(BSW), and Forward sweep(FSW), using flow analysis program , FLUENT 6.3 Parallel. The results of the BSW model show reduced mass flow rates of tip leakage and increased total-to-static efficiency. The strength of leading edge bow shock was decreased a little with BSW model. And the BSW model also shows a good performance around the hub region compared to other models.초 록 본 연구에서는 액체로켓엔진의 터보펌프용 초음속 터빈 로터 블레이드에 스윕 각도 ±15°를 적용하여 전방스윕(FSW), 후방스윕(BSW)모델의 유동형태 및 성능을 기준모델(NSW)과 비교하여 스윕 적용의 효과를 살펴보았다. 3차원 Navier-Stokes 유동해석에는 상용 코드인 FLUENT 6.3 Parallel을 사용하였다. BSW 모델은 기준 모델(NSW)에 비해 팁 간극으로 빠져나가는 누설 손실량을 줄이는데 효과가 있었고 정효율 증가에도 영향을 미쳤다. BSW 모델은 앞전 충격파의 강도를 다소 완화 시키고 허브 부근의 영역에서 다른 모델에 비해 좋은 성능을 보인다.Key Words: Supersonic Turbine(초음속터빈), Liquid Rocket Engine(액체로켓엔진), Turbopump(터보펌프), Blade Sweep(날개스윕), Turbine Performance(터빈성능)