• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2177-2183
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• 1994

The rapid expansion or condensible gas such as moist air of steam gives rise to nonequilibrium condensation. As a result of irreversibility of condensation process in the supersonic cascade flow of low pressure steam turbine, the entropy of the flow is increased, and the efficiency of the turbine is decreased. In the present study, to investigate the flow of moist air in 2-dimensional cascade made as the configuration of the tip section of the last actual steam turbine moving blade, the static pressure at both sides of pressure and suction of blade are measured by static pressure taps and the distribution of Mach number on both surfaces of the blade are obtained by using the measured static pressure. Also, the flow field is visualized by a schlieren system. From the experimental results, the effects of the stagnation temperature and specific humidity on the flow properties in a 2-dimensional stationary cascade of a practical steam turbine blade are clearly identified.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.66-72
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• 2005

In this paper, a small supersonic wind tunnel is designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The flow is visualized by means of a single pass Schlieren system. The supersonic cascade with 2-dimensional supersonic nozzle was tested for various blade leading edge shapes and gaps between the nozzle and cascade. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions are observed.

• International Journal of Aeronautical and Space Sciences
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• v.5 no.2
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• pp.9-17
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• 2004

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

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.839-847
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• 2004

In this study, the flow characteristics within supersonic cascades are numerically investigated by using Fine Turbo, a commercial CFD code. Cascade flows are computed for three different inlet conditions. : a uniform supersonic inlet condition, a linear nozzle and a converging-diverging nozzle located in front of cascades. The effect of inlet conditions is compared and flow characteristics including shock patterns and shock-boundary layer interaction are analyzed. Also the effect of design parameters such as pitch-chord ratio, blade angle and blade surface curvature on the flow within supersonic cascades are studied.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.11
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• pp.3022-3030
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• 1995

The irreversibility of condensation process in the supersonic flow of steam turbine cascade causes the entropy to increase and the total pressure loss to be generated. In the present study, in order to investigate the moist air flow in two dimensional steam turbine cascade made as the configuration of the last stage tip section of the actual steam turbine moving blade, the static and total pressures along suction side of the blade are measured by pressure taps and Pitot tube. The flow field is visualized by a Schlieren system. The effects of stagnation temperature and the degree of supersaturation on energy loss and entropy change in the flow are clearly identified.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.99-108
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• 2004

In this paper, a small supersonic wind tunnel is designed and built to study the flow characteristics of a supersonic impulse turbine. The flow is visualized by means of a single pass Schlieren system. The supersonic cascade with 2-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 are observed.

• Journal of computational fluids engineering
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• v.10 no.2
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• pp.54-59
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• 2005

For the improvement of aerodynamic performance of the turbine blade in a turbopump for the liquid rocket engine, the optimization of turbine profile shape has been studied. The turbine in a turbopump in this study is a partial admission of impulse type, which has twelve nozzles and supersonic inflow. Due to the separated nozzles and supersonic expansion, the flow field becomes complicate and shows oblique shocks and flow separation. To increase the blade power, redesign ol the blade shape using CFD and optimization methods was attempted. The turbine cascade shape was represented by four design parameters. For optimization, a genetic algorithm based upon non-gradient search hue been selected as an optimizer. As a result, the final blade has about 4 percent more blade power than the initial shape.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.1
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• pp.1-7
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• 2005

The inlet boundary condition of computations about the supersonic turbine flow is commonly applied as far-field inlet boundary condition with specified velocity. However, the inflow condition of supersonic turbine is sometimes affected by the shocks or expansion waves propagated from leading edges of blade. These shocks and expansion waves alter the inlet boundary condition. In this case, the inlet boundary condition can not be specified Therefore, in this paper, numerical analyses for three different inlet conditions - fa-field inlet boundary condition, inlet boundary condition with a linear nozzle and inlet boundary condition with a converging-diverging nozzle - have been performed and compared with experimental results to solve the problem. It is found that the inlet condition with a linear nozzle or a converging-diverging nozzle can prevent changing of inlet boundary condition, and thus predict more accurately the supersonic flow within turbine cascade than a far-field inlet boundary condition does.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.99-103
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• 2003

An analysis of the flow within supersonic turbine cascades is necessary to design and manufacture turbo-pump system. Because of the differences between the specified inlet boundary value and the computed inlet value caused by the far field inlet boundary condition, the computations at desired inlet conditions can not be achieved. So, this paper studied the problem occurred when far field inlet conditions were specified as inlet boundary conditions. And the numerical analyses using Fine Turbo, CFD Program, has been performed and compared with those of experiments when a converging-diverging nozzle or a linear nozzle was located in front of cascades instead of the far field inlet condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.391-397
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• 2004

The performance characteristics of partial admission supersonic turbines are analyzed by using the commercial CFD program FLUENT6.0. The governing equations were discretized with Euler implicit method in time and 2nd-order upwind scheme of FVM in space. The k-$\varepsilon$ turbulence model was utilized to describe the turbulent flow field. In order to investigate the nozzle--rotor interactions and the effect of partial admission, the flows in supersonic turbine rotor cascades with a nozzle are computed. Extensive computations of partial admission supersonic turbines provide the shock structures and flow patterns in the nozzle and rotor. It is clearly shown that the nozzle flow is highly affected by the shocks or expansion waves propagated from the rotor leading edge. And the rotor flow is also affected by the shocks or wakes originated from the nozzle.