• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.10-13
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• 2010

Low pressure combustion tests for TDM(Technology Demonstration Model) of 75 tonf thrust chamber were performed. It has design chamber pressure of 60 bar, propellant mass flow rate of 243.6 kg/s. Due to the limitation of the current firing test facility in Korea, the combustion tests were conducted to verify the operation and the combustion performance at low pressure condition (30 bar, 121.8 kg/s). All the tests had been successfully executed without the damage of the hardware. These test results can be used as fundamental data to predict the combustion performance at design point condition for 75 tonf thrust chamber.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.10-20
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• 2019

Recently, fluidic thrust vector control has become a core technique to control multifarious air vehicles, such as supersonic aircraft and modern rockets. Fluidic thrust vector control using the shock vector concept has many advantages for achieving great vectoring performance, such as fast vectoring response, simple structure, and low weight. In this paper, computational fluid dynamics methods are used to study a three-dimensional rectangular supersonic nozzle with a slot injector. To evaluate the reliability and stability of computational methodology, the numerical results were validated with experimental data. The pressure distributions along the upper and lower nozzle walls in the symmetry plane showed an excellent match with the test results. Several numerical simulations were performed based on the shear stress transport(SST) $k-{\omega}$ turbulence model. The effect of the momentum flux ratio was investigated thoroughly, and the performance variations have been clearly illustrated.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2325-2334
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• 2023

To study the lubrication performance of tilting-pad thrust bearing (TPTBs) during start-up in nuclear pump, a hydrodynamic lubrication model of TPTBs was established based on the computational fluid dynamics (CFD) method and the fluid-structure interaction (FSI) technique. Further, a mesh motion algorithm for the transient calculation of thrust bearings was developed based on the user defined function (UDF). The result demonstrated that minimum film thickness increases first and then decreases with the rotational speed under start-up condition. The influence of pad tilt on minimum film thickness is greater than that of collar movement at low speed, and the establishment of dynamic pressure mainly depends on pad tilt and minimum film thickness increases. As the increase of rotational speed, the influence of pad tilt was abated, where the influence of the moving of the collar dominated gradually, and minimum film thickness decreases. For TPTBs, the circumferential angle of the pad is always greater than the radial angle. When the rotational speed is constant, the change rate of radial angle is greater than that of circumferential angle with the increase of loading forces. This study can provide reference for improving bearing wear resistance.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.60 no.1
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• pp.80-86
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• 2024

We analyzed the performance of hubless rim propellers based on the number of blades, maintaining a fixed pitch ratio and expanded area ratio, using computational fluid dynamics (CFD). Thrust coefficient, torque coefficient and efficiency according to the number of blades were analyzed. In addition, the pressure distribution on the discharge and suction sides of the blade was analyzed. As the advance ratio increases, the thrust coefficient decreases. The highest thrust was shown when the advance ratio was lowest. For the three, four, five and six-blades, the torque coefficient tended to decrease as the advance ratio increased. In the case of seven and eight-blades, the torque coefficient tended to increase as the advance ratio increased. The maximum efficiency was found when the advance ratio was 0.8. When the three-blade, it showed high efficiency at all advance ratios. A high pressure distribution was observed at the leading edge of the discharge blade, and a low pressure distribution was observed at the trailing edge. Applying a hubless rim-driven thruster with the three-blade can generate higher thrust and increase work efficiency.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.3
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• pp.103-110
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• 2003

The present work was conducted to achieve the better understanding of the performance analysis technique for the expander type air turbo ramjet engine. For this purpose, the performance analysis was carried out using a small engine(8.0kN thrust) with two types of fuels. From this analysis, at the same input condition, the thrust of methane-fueled engine was 25% lower than that of hydrogen. In addition, the case of methane shows the inapplicable engine performance cycle.(i.e., The compressor work exceeds the turbine output power) These results come mainly from the different heating value of each fuel and specific heat. This analysis also shows that, to build a same performance cycle as the hydrogen case, the methane-fueled engine requires increased air and fuel flow rates, increased turbine expansion ratio, and decreased compressor pressure ratio.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.2
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• pp.144-149
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• 2014

A ground firing test for hot-fire performance evaluation according to the characteristic length($L^*$) variation of thrust chamber was carried out for the hydrazine thruster which may be employed in space launch vehicles. A scrutiny into the performance characteristics of each thruster is made in terms of thrust, specific impulse, response characteristics, and characteristic velocity at steady-state firing mode with propellant inlet pressure of 2.41 MPa (350 psia). Through the test results, it has been verified that performance of characteristic velocity and specific impulse degrades as the characteristic length deviates from that of the standard model. Thus, it is confirmed that the thrust chamber configuration of standard model was suitably designed for the requirement specified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.189-196
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• 2018

Propeller performance measurement system for high altitude UAV was designed and applied to the wind tunnel test for 2 propeller models with a diameter around 1 m. Mechanical power of the propeller was directly measured by using the torque sensor installed on the rotating axis. The thrust of whole operation body including the propeller was measured by thrust road cell. The guide rail system was suggested to reduce the weight influence of operation body on the thrust road cell. The influence of each measured variables on the aerodynamic coefficients was studied with the repeatability and uncertainty analysis. This analysis result shows that the accuracies of the road cell and the wind velocity were major factors for the thrust coefficient. Propeller performance with typical RPM was measured with various wind speeds and the test results was summarized by performance coefficients for 5 different RPM.

• The KSFM Journal of Fluid Machinery
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• v.9 no.2 s.35
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• pp.39-43
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• 2006

The magnitude of the axial force acting on turbopump bearings has a great influence on the operational reliability and service life of a turbopump. In the turbopump under current investigation the cavity vanes are introduced to the pump shroud casing to control the axial thrust of the turbopump. To investigate the effect of the cavity vanes, 3D computational flow analyses for a propellant pump stage including an inducer, impeller, volute and secondary flow passages are performed with and without the vanes. The results show that the cavity vanes are very effective in reducing the magnitude of axial thrust without notable changes on the overall performance of the turbopump.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1523-1531
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• 2017

In general, the thrust vector control should be fast and stable in the initial launch phase. Two types of conventional controllers, one is for pitch angle control and the other is for pitch rate control, are designed based on the equation of motion without aerodynamics and are compared in the viewpoints of the stability margin and the time response performance. Also analyzed are the rejection capabilities to cope with high aerodynamic disturbances caused by high angle of attacks in initial booting phase. Additionally, time response features at actuator saturation are investigated. Based on those results, we suggest a controller structure which is more suitable for thrust vector control of missiles at initial booting phase.

• Tribology and Lubricants
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• v.22 no.4
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• pp.173-181
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• 2006

In the present study, we developed a numerical analysis software to predict performance of tilting-pad thrust bearings. The finite element method was adopted to compute lubricant film pressure and temperature. Three-dimensional heat transfer equations were solved simultaneously for the lubricant film, pad, and runner. Groove temperature was assumed with two different models. From application of the software to a thrust bearing, it has been seen that the three-dimensional analysis predicts higher temperature than the average temperature analysis. It has also been found that the groove model with a hot-oil-carry-over factor predicts higher temperature.