• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.19-27
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• 2021

In this study, a high-pressure subsacle thrust chamber was developed to verify the core technology for KSLV-II performance enhancement. The core technologies are the design of an injector for high-pressure combustion, development of a combustion stabilization device using the additive manufacturing technique, and the design and fabrication of mixing head and regeneratively cooled combustion chamber. The core technologies, which have been verified through the development of high-pressure subscale thrust chamber, will be used to develop large engine liquid rocket engine thrust chamber in the future.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.2
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• pp.46-52
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• 2009

Drilling operation is such an important machining process, which has been wildly applied to the industry, occupied over 30% of whole industry. However, there are many aspects of drilling process should be improved, such as increases of thrust force, surface roughness, and roundness, ect. In this study, we are aiming to reduce the thrust force, surface roughness, and roundness in drilling process. For this purpose, multi facet drills (MFD) of three types that are modified from standard drill (STD) are developed. The first type is multi stair drill (MSD) with shape of stair on relief plane. The second type is rough facet drill (RFD) with shape of round on relief plane. The third type is rough flute drill (RFLD) with shape of round on flute plane. For three types of MFD, we were carried out performance evaluation from the perspective of thrust force, surface roughness and roundness of machined hole. From obtained result, we could confirmed that performance of rough flute drill (RFLD) type is most excellent.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.79-85
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• 2008

Generally Solid Rocket Motor(SRM) has advantages like this - safety, simplicity and flexibility in design and manufacturing process. However, once propellant grain shape and nozzle throat area are determined, modification of thrust magnitude is nearly impossible. Recently, methods for controlling the thrust magnitude of SRM are vigorously developed. This paper predicts internal ballistic performance variation, especially thrust of SRM by means of Linear Approximation according as chamber pressure or nozzle throat area is changed. The results predicted by the proposed method are good agreement with the those of exclusive Ballistic Performance Prediction Program(SPP).

• Aerospace Engineering and Technology
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• v.3 no.2
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• pp.183-190
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• 2004

The performance analysis of a fuel pump for a liquid rocket engine has been performed numerically on its design condition. A commercial three-dimensional Navier-Stokes flow solver has been used for the computation. All of the fuel pump components - inducer, impeller, volute and secondary flow passages - are included in computation for the accurate estimation of the leakage flow rate which affects the performance and axial thrust. A pitchwise-averaged mixing plane method was used on the boundaries among the fuel pump components to save computational time. The predicted overall performance satisfied the design requirement. However, the axial thrust exceeded a permissible limit. In order to reduce the axial thrust, the secondary flow passage design has been changed. With this change, the axial thrust level has been reduced to 30% as compared with the original value.

• Tribology and Lubricants
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• v.39 no.2
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• pp.76-80
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• 2023

This paper describes an experimental investigation of the effect of cooling flow rate on gas foil thrust bearing (GFTB) performance. In a newly developed GFTB test rig, a non-contact type pneumatic cylinder provides static loads to the test GFTB and a high-speed motor rotates a thrust runner up to the maximum speed of 80 krpm. Force sensor, torque arm connected to another force sensor, and thermocouples measures the applied static load, drag torque, and bearing temperature, respectively, for cooling flow rates of 0, 25, and 50 LPM at static loads of 50, 100, and 150 N. The test GFTB with the outer radius of 31.5 mm has six top foils supported on bump foil structures. During the series of tests, the transient responses of the bearing drag torque and bearing temperature are recorded until the bearing temperature converges with time for each cooling flow rate and static load. The test data show that the converged temperature decreases with increasing cooling flow rate and increases with increasing static load. The drag torque and friction coefficient decrease with increasing cooling flow rate, which may be attributed to the decrease in viscosity and lubricant (air) temperature. These test results suggest that an increase in cooling flow rate improves GFTB performance.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.414-416
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• 2009

In order to build a transient simulation program for a high thrust liquid rocket engine(LRE), a static performance simulation program for components were made. The components were the thrust chamber (combustion chamber and supersonic nozzle), centrifugal pump (impeller and volute casing), impulse turbine, and flow control devices (control valve and orifice). Simplified mathematical models based on classical thermodynamic and inviscid theories were used to remove complexity and enhance the utility of the program. We examined the results of each program qualitatively for validate each component modeling.

• Tribology and Lubricants
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• v.10 no.4
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• pp.33-42
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• 1994

An influence of inlet pressure on the performance of sector-shaped pad thrust bearings is investigated theoretically. The optimum conditions of film thickness or the optimum positions of pivot are found through the evaluation of load capacity for all available conditions of film thickness, under the operating conditions which the thermal and pad deformation effects can be neglected. The bearing performance including the inlet pressure effects is obtained for a wide operating ranges that inertia parameter(Re$^{*}$) is up to unity, and for the various cases of pad extent angle (number of pad) and the three cases of the angle between pads. The results show that the inlet pressure has a large influence on the performance of sector-shaped pad thrust bearings. In the design of sector-shaped pad bearings, due to the inlet pressure, the optimum number of pad is varied with the operating speed and the angle between pads, and the optimum position of pivot is located toward the leading edge along with the operating speed increases.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.1
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• pp.24-33
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• 2010

Design of a Pump Jet Propulsor (PJP) was undertaken for an underwater body with axisymmetric configuration using axial/low compressor design techniques supported by Computational Fluid Dynamics (CFD) analysis for performance prediction. Experimental evaluation of the PJP was earned out through experiments in a Wind Tunnel Facility (WTF) using momentum defect principle for propulsive performance prior to proceeding with extensive experimental evaluation in towing tank and cavitation tunnel. Experiments were particularly conducted with respect to Self Propulsion Point (SPP), residual torque and thrust characteristics over a range of vehicle advance ratio in order to ascertain whether sufficient thrust is developed at the design condition with least possible imbalance torque left out due to residual swirl in the slip stream. Pumpjet and body models were developed for the propulsion tests using Aluminum alloy forged material. Tests were conducted from 0 m/s to 30 m/s at four rotational speeds of the PJP. SPP was determined confirming the thrust development capability of PJP. Estimation of residual torque was carried out at SPP corresponding to speeds of 15, 20 and 25 m/s to examine the effectiveness of the stator. Estimation of thrust and residual torque was also carried out at wind speeds 0 and 6 m/s for PJP RPMs corresponding to self propulsion tests to study the propulsion characteristics during the launch of the vehicle m water where advance ratios are close to Zero. These results are essential to assess the thrust performance at very low advance ratios to accelerate the body and to control the body during initial stages. This technique has turned out to be very useful and economical method for quick assessment of overall performance of the propulsor and generation of exhaustive fluid dynamic data to validate CFD techniques employed.

• Journal of the Korean Geotechnical Society
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• v.34 no.9
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• pp.33-42
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• 2018

When an off-road tracked vehicle travels, an engine thrust that is transmitted to the continuous track induces a shearing action on the soil-track interface. Consequently, the relative displacement known as slip displacement takes place on the soil-track interface, which develops an associated soil thrust acting as a traction force. For the loose or soft ground conditions, an excessively large slip displacement can be required for the development of the desired soil thrust which will make the tracked vehicle mobile and therefore the outer surface of the continuous track is generally designed to protrude with grousers. This paper fundamentally studied the effect of grousers on the soil thrust of off-road tracked vehicles. Based on the soil-track interaction theory, a new soil thrust assessment method that properly takes into account the effect of grousers was developed. Also, the soil thrust of off-road tracked vehicles equipped with a number of grousers was evaluated using the developed assessment method. The results showed that grousers increased the soil thrust of the continuous track, enhancing the overall tractive performance of off-road tracked vehicles. These effects were more obvious as the height of grouser increased and the spacing of grouser decreased; thus, it is concluded that the grouser which has smaller shape ratio (span of the grouser to a grouser height) significantly enhances off-road tracked vehicle's performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.6
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• pp.642-648
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• 2016

This paper deals with an analytical and experimental investigation to predict the axial thrust load that results from turbocharger operating conditions. The Axial forces acting on the turbocharger thrust bearing are caused by the unbalance between turbine wheel gas forces and compressor wheel air forces. It has a great influence on the friction losses, which reduces the efficiency and performance of high-speed turbocharger. This paper presents the calculation procedure for the axial thrust forces under operating conditions in a turbocharger. The first step is to determine the relationship between thrust forces and strains by experimental and numerical methods. The analysis results were verified by measuring the strains on a thrust bearing with the specially designed test device. And then, the operating strains and temperatures were measured to inversely calculate the thrust strains which were compensated the thermal effects. Therefore it's possible to calculate the magnitudes of the thrust forces under operating turbocharger by comparing the regenerated strains with the rig test results. It will possible to optimize the design of a thrust bearing for reducing the mechanical friction losses using the results.