• The KSFM Journal of Fluid Machinery
• /
• v.16 no.3
• /
• pp.10-17
• /
• 2013

The organic Rankine cycle has been widely used to convert the renewable energy such as the solar energy, the geothermal energy, or the waste energy etc., to the electric power. Some previous studies focused to find what kind of refrigerant would be a best working fluid for the organic Rankine cycle. In this study, R245fa was chosen to the working fluid, and the cycle analysis was conducted for the output power of 30kW or less. In addition, properties (temperature, pressure, entropy, and enthalpy etc.) of the working fluid on the cycle were predicted when the turbine output power was controlled by adjusting the mass flowrate. The configuration of the turbine was a radial-type and the supersonic nozzles were applied as the stator. So, the turbine was operated in partial admission. The turbine efficiency and the optimum velocity ratio were considered in the cycle analysis for the low partial admission rate. The computed results show that the system efficiency is affected by the partial admission rate more than the temperature of the evaporator.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.11 s.254
• /
• pp.1131-1138
• /
• 2006

Aerodynamic shape design of a partial admission turbine using CFD has been performed. Two step approaches are adopted in this study. Firstly, two-dimensional blade shape is optimized using CFD and genetic algorithm. Initially, the turbine cascade shape is represented by four design parameters. By controlling the design parameters as variables, the non-gradient search is analyzed for obtaining the maximum efficiency. The final two-dimensional blade proved to have a more blade power than the initial blade. Secondly, the three-dimensional CFD analysis including the nozzle, rotor and stator has been conducted. To avoid a heavy computational load due to an unsteady calculation, the frozen rotor method is implemented in steady calculation. The frozen rotor method can detect a variation of the flow-field dependent upon the blade's circumferential position relative to the nozzle. It gives a better idea of wake loss mechanism starting from the lip of the nozzle than the mixing plane concept. Finally, the combination of two and three dimensional design method of the partial admission turbine in this study has proven to be a robust tool in development phase.

• Journal of Advanced Marine Engineering and Technology
• /
• v.22 no.3
• /
• pp.396-404
• /
• 1998

A numerical analysis is presented for the transient behavior of a rotating turbines blades. The response due to partial admission during start-up and resonance pass is considered, Modal analysis and numerical integation method are used for solving the problems A theory for determining the material and aerodynamic damping values of turbine blades is presented. The damping values of the various modeling of blaes-uniform beam and tapered twisted beam-are calculated and the influence on blades response is investigated. The effect of angular velocity on transient response are also shown.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.601-602
• /
• 2002

Numerical simulation using well-known commercial software Fine/Turbo is applied to the analysis of the aerodynamic performance for the supersonic turbine system with partial admission nozzle. Calculation was performed for coupled system of nozzle and blades using mixing plane method. In addition, calculations were also performed for the blades alone to investigate the effect of the performance variation with blade profile. These computational results are compared with the experiments. The agreement between the prediction and the experiment was found to be satisfactory..

• Solar Energy
• /
• v.19 no.4
• /
• pp.1-10
• /
• 1999

The phenomena of energy separation through the vortex tube was investigated experimentally, to see the effect of nozzle area ratio and partial admission rate on the energy separation and cooling capacity. The experiment was tarried out with various nozzle area ratios from 0.031 to 0.232 and partial admission rate from 0.176 to 0.956 by varying input pressure($0.2{\si\m}0.5$ MPa) and cold air mass fraction($y=0.1{\sim}1.0$). From the experimental result, we found the optimum nozzle area ratio and the effective partial admission rate for the available use and best cooling performance in given operation condition. While the maximum drop of cold air temperature was observed at around y=0.3 and $S_n=0.155$, the maximum cooling capacity was observed at around y=0.6 and $S_n=0.094$.

• The KSFM Journal of Fluid Machinery
• /
• v.7 no.6 s.27
• /
• pp.28-37
• /
• 2004

An experimental study is conducted to investigate flow characteristics on a small axial-type turbine which is applied as the rotating part of air tools. It operates in a partial admission due to consumption restriction of the high pressure air. In this operating condition, it is necessary to understand flow characteristics for obtaining the high specific output power. Tested turbine consists of two stages and the mean radius of flow passage is less than 10mm. A 6 bar pressure air is used to operate the turbine. The experimental results show that flow angles depend on the measuring location along the circumferential direction, but its discrepancy is alleviated along the axial direction. Absolute flow velocities show three times difference according to the measuring location at the exit of the first rotor due to the partial admission, but they show similar value at the exit of the second rotor by the velocity diffusion. From the measured flow angles and velocities, a ratio of output power obtained by the first and second rotor is estimated. It shows that the output power obtained by the second rotor is about $11\%$ to that by the first rotor at 60,000 RPM. It is effective therefore to improve the first rotor for increasing the turbine output power.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2001.11a
• /
• pp.11-14
• /
• 2001

3-D compressible flow analysis was conducted by using mixing plane method for turbine system which is consisted of partial admission nozzle and rotor. Computational results are shown oblique shock wave in blade leading and trailing edge and also shown flow separation along suction surface of blade due to abrupt blade curvature. But computational results are well agree with 1-D calculation results and experimental data.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.8 no.3
• /
• pp.53-60
• /
• 2004

In order to investigate the nozzle - rotor interactions and the effect of partial admission, the flows in supersonic turbine rotor cascades with a nozzle have been computed. Extensive computations of partial admission supersonic turbines provide the shock structures and flow patterns in the nozzle and rotor. The governing equations were discretized with Euler implicit method in time and 2nd-order upwind scheme of FVM in space. The $\kappa$-$\varepsilon$ turbulence model was utilized to describe the turbulent flow field. 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.

• The KSFM Journal of Fluid Machinery
• /
• v.5 no.4 s.17
• /
• pp.11-18
• /
• 2002

A turbopump system composed of two pumps and one turbine is considered. The turbine composed of a nozzle and a rotor is used to drive the pumps while gas passes through the nozzle and potential energy is converted to kinetic energy, which forces the rotor blades to spin. In this study, an aerodynamic design of turbine system is investigated with some pre-determined design requirements (i.e., pressure ratio, rotational speed, required power, etc.) following Liquid Rocket Engine (L.R.E.) system specifications. For simplicity of turbine system, impulse-type rotor blades for open-type L.R.E. have been chosen. Usually, the open-type turbine system requires low mass flow-rate compared to close-type system. In this study, a partial admission nozzle is adopted to maximize the efficiency of the open-type turbine system. A design methodology of turbine system was introduced. Especially, partial admission nozzle was designed by means of simple empirical correlations between efficiency and configuration of the nozzle. Finally, a turbine system design is presented for a 10 ton thrust level of L.R.E.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.11 no.4
• /
• pp.10-18
• /
• 2007

A tested micro axial-type turbine consists of two stages and its mean radius of rotor flow passage is 8.4 mm. This turbine could be applied to a driver of micro power system, and its rotational speed in the unloaded state reaches to 100,000 RPM. The performance of this system is sensitive depending on the blade angles of the rotor and stator because it is operated in a low partial admission rate, so a performance test is conducted through measuring the specific output power and the net specific output torque with various blade angles on the nozzle, stator and rotor. The experimental results show that the net specific output torque is varied by 15% by changing the rotor blade angle, and the optimal incidence angle is about $10.3^{\circ}$.