• Journal of computational fluids engineering
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• v.17 no.3
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• pp.53-58
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• 2012

Steady flow simulations through a high pressure turbine guide vanes were carried out. The main objective of the present work is to study the performance of turbulence models on the steady flow prediction from aerodynamic and aerothermal points of view. Three turbulence models were compared, namely SST, k-${\omega}$ and ${\omega}$-Reynolds stress models. The laminar results were also compared. The comparison was done with emphasis on the isentropic Mach number and heat transfer coefficient along the blade, and total pressure loss in the wake region. The calculated isentropic Mach number showed reasonable agreement with experimental data along the blade surface for all three turbulent models. For the total pressure loss in the wake region, ${\omega}$-Reynolds stress model showed the best agreement with the experimental data. However, unless using an appropriate transition model, the heat transfer coefficients of all three turbulent models showed poor agreement with experimental data.

• International Journal of Fluid Machinery and Systems
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• v.9 no.2
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• pp.107-118
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• 2016

This paper focuses on the single stage and multistage performance characteristics of centrifugal mixed flow submersible borewell pump. This study reveals that the performance of single stage pump is higher than that of multistage pumps. The head, input power and efficiency of single stage pump are higher than the per stage head, per stage input power and efficiency of multistage pumps. This study is divided into three parts. In the first part, five prototype pumps were made in single stage and multistage construction and the performance tests were conducted. In the second part, numerical validation has been done for different turbulence models and grid sizes. k-Omega SST model has been selected for the performance simulation and was validated with the performance of the test pump with static pressure tappings. In the third part, single and three stage pump performance were simulated numerically and compared with experimental results. The detailed analysis of pressure and velocity distributions reveals the difference in performance of single and three stage pump, due to non-uniform flow and difference in averaged flow velocities at the subsequent impeller inlets except the 1st stage impeller inlet.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.5
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• pp.10-18
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• 2011

A new film cooling method to protect the pylon injector from aerodynamic heating for a scramjet combustor is proposed and verified with numerical methods. The conditions for the Mach 8 flight at an altitude of 35km are considered. Air is considered as a coolant. Three-dimensional Navier-Stokes equations with $k-{\omega}$ SST turbulence model are used. A downward injection of coolant from the top of the pylon gives higher cooling effects with less mass flow rate of coolant than the upward coolant injection from bottom of the pylon. Also, the downward injection shows little flow separation due to the favorable pressure gradient and does not disturb the flowfields near pylon injector, which results in reduction of pressure losses.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.3
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• pp.9-15
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• 2010

Numerical investigation was carried out on axisymmetric over-expanded rocket nozzle to predict flow fields of transitional shock separation patterns. The unsteady, compressible N-S equations with k-$\omega$ SST for turbulence model closure were solved using a fully implicit finite volume scheme. Computed results were in good agreement with previous experimental works. It was found that strong side-loads were generated during the transition of RSS to FSS due to the development of a vortex ring in the inviscid jet core region. Hysteresis phenomenon exhibited by the shock-separation patterns was also found during the start-up and shut-down processes.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.1
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• pp.20-28
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• 2010

The mixing characteristics of pylon injection in a Scramjet combustor and effects of film cooling to protect pylon from air-heating were investigated. Three-dimensional Navier-Stokes equations with $k-{\omega}$ SST turbulence model were used. Fuel hydrogen and air were considered as coolants. There were remarkable improvements of penetration and mixing rate with the pylon injection. There was also over-heating on the front surface of the pylon without film cooling. The coolant injected parallel to the front surface of the pylon protects the pylon from over-heating.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.678-681
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• 2010

In the present work, a numerical study is conducted to investigate the effect of the transient nozzle pressure ratio (NPR) on the flow fields inside the nozzle. The unsteady, compressible, axisymmetric, Navier-Stocks equations with SST $k-{\omega}$ turbulence model are solved using a fully implicit finite volume scheme. In order to simulate the start-up and shut-down processes of the engine, NPR is varied from 2.0 to 10.0. It is observed that the interaction patterns and the hysteresis phenomenon strongly depend on the time variation of NPR, leading to significantly different characteristics in the lateral forces.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.679-681
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• 2017

Numerical analysis was carried out by applying the concept of E-D(expansion-deflection) nozzle to dual bell nozzle. We used the CEA code to calculate the chemical composition of the nozzle and to analyze the freezing flow of 8 species. The turbulence model was chosen as the $k-{\omega}$ SST. We applied the concept of E-D nozzle to the dual bell nozzle and performed the calculated transition altitude and performance. As a result of the interpretation, the application of the E-D nozzle concept led to the formation of over-expansion conditions, which resulted in an increase in the transition altitude.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.211-214
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• 2011

In the present work, a computational study was conducted to investigate characteristic of lateral force on the flow fields inside the propulsion nozzle with step. The unsteady, compressible, axisymmetric, Navier-Stocks equations with SST k-${\omega}$ turbulence model are solved using a fully implicit finite volume scheme. In order to simulate the shut-down process of the engine, NPR is varied from 100.0 to 10.0. It is observed that the separation point and Mach-disk strongly depend on the variation of NPR, and adjusting the step lead to significantly different characteristics in the lateral forces.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.167-171
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• 2012

A computational analysis of nozzle flow is conducted to investigate effects of the flight altitude on thrust performance. Reynolds-averaged Navier-Stokes equation with k-${\omega}$ SST(Shear Stress Transport) turbulence model is employed to simulate the nozzle flow in various altitude conditions, where continuum mechanics is to be valid. Thrust performance of the nozzle is exceedingly poor upto 10 km of flight altitude because of the irreversible phenomena such as shock and/or flow separation occurring inside the nozzle, whereas it is restored to the nominal value as the altitude is attained higher than 30 km.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.47-55
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• 2018

In order to determine whether three-dimensional effects exist in a pintle nozzle of axisymmetric shape, a three-dimensional numerical analysis was performed. The compressibility correction was implemented with the k-${\omega}$ SST turbulence model to predict the complex flow separation transition in acceptable accuracy. Recirculation zones were observed at both the front end and rear faces of the pintle, and the flow through the pintle nozzle conveyed complex shock wave structures. Three-dimensional effects that resulted from the reasonable flow separation location were noted, and a trace of the transient pressure increase was observed, mismatched by a two-dimensional axi-symmetric analysis.