• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.80-88
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• 2018

The function of a vehicle holding device (VHD) is to securely hold a launch vehicle on the launch pad and release the launch vehicle at maximum thrust after engine ignition to allow lift-off of the launch vehicle. During the release of the launch vehicle, to prevent the Ka doing a doing a doing mode, which is the vertical oscillation of the entire liquid propellant, the release of the launch vehicle should be gradual. In this study, for the gradual release of a launch vehicle, a hydraulic system comprising an accumulator and pyro valve to operate a hydraulic cylinder and control the speed of the cylinder with an orifice is introduced. Through a test, the influence of design variables on the cylinder speed is analyzed. Based on this, the design values of the hydraulic cylinder are determined. Through this study, the engineering basis for developing a VHD releasing a launch vehicle at maximum thrust is provided.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.12-17
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• 2018

A natural cavitation-type high-speed underwater vehicle with solid rocket motor is tested, and its speed and running distance are measured. The outputs from pressure sensors on the surface of the vehicle reveal a pressure-time history reflecting the development of supercavitation. Underwater cameras installed on the wall of the test pool record the entire process from the onset of supercavitation to its full development. CNU-SuperCT, based on two-dimensional inviscid theoretical analysis, is used to simulate test results. Considering CNU-SuperCT does not include the control fins of the vehicle, simulation results agree with test results very well. Additionally, pictures from underwater cameras support the test results.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.107-114
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• 2018

Korea Space Launch Vehicle (KSLV)-I flight test data and the modified 1-dimensional steady state modeling data from the critical design results of the KSLV-II liquid oxygen filling system operation are compared to validate the reliability of critical design modeling. A comparison of major flow rates and pressure values between test data and calculation results are conducted. The relative errors relative to maximum total flow rate for each cooling, filling, and replenishment mode are determined within 6.7%. Calculated pressure values at the outlet of the pump and the inlet of flow control valves are within 5.1%. The pressure at the inlet of the launch vehicle for each operation mode are within the measured pressure range.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.15-23
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• 2019

In this study, an extinguishment model of a three-dimensional solid propellant rocket was developed by combustion and fast depressurization to control the thrust of a solid rocket. Computational fluid dynamics simulation was carried out to ascertain the change in flow patterns in the combustion chamber and the extinguishment process by using a pintle. An ammonium perchloride was used as the target propellant and the dynamic behavior of its major parameters such as temperature, pressure, and burning rate was predicted using the combustion model. The dynamic behavior of the combustion chamber was confirmed by fast depressurization from an initial pressure of 7 MPa to a final pressure of 2.5 MPa at a depressurization rate of approximately -912 MPa/s.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.33-45
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• 2019

In this study, numerical simulations were performed to investigate the steady-state characteristics of a symmetric pintle nozzle by varying the position of the pintle and the altitude. The pintle nozzle shape was used in a linear pintle nozzle that had been analyzed prior to the study, and the boundary conditions of the chamber were considered to be according to the propellant burn-back characteristics. A software was used to perform a verification analysis of the square nozzle, pintle nozzle, and high-altitude conditions with an appropriate analytical technique. The pintle position had three different nozzle throat area conditions-: fully closed, half open, and fully open, and the altitude was set at 0, 5, and 20 km. The study compared the thrust, pintle drive load, and static stability at each condition.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.124-131
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• 2019

A design study of gas turbine engine simulation duct was conducted to investigate the operating characteristics and control gain tunning of the Altitude Engine Test Facility(AETF). The simulation duct design involved testing variable spike nozzle and ISO standard choking nozzle to verify the measurements such as mass flow rate and thrust. The simulation duct air flow area was designed to satisfy Ma 0.4 at the aerodynamic interface plane(AIP) at engine design condition. The test conditions for verifying the AETF controls and measurement devices were deduced from 1D analysis and CFD calculation results. The spike-cone driving part was designed to withstand the applied aero-load, and satisfy the axial traversing speed of 10 mm/s at whole operation envelops.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.5
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• pp.287-296
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• 2020

The present study aims to improve the accuracy of the maneuvering simulations based on captive model test results. To derive the hydrodynamic coefficients in a self-propelled condition, a mathematical maneuvering model using a whole vehicle model was established. Captive model tests were carried out using the Vertical Planar Motion Mechanism (VPMM) equipment. A motor controller was used to control the constant propeller revolution rate during pure motion tests. The resistance tests, self-propulsion tests, static drift tests, and VPMM tests were performed in the towing tank of Seoul National University. When the vertical drift angle changes, the gravity load on the sensors were changed. The hydrodynamic forces were deduced by subtracting the gravity load from the measured forces. The hydrodynamic coefficients were calculated using the least-square method. The simulation of the turning circle test was compared with the free-running model test result, and the error of the turning radius was 8.3 % compared to the free-running model test.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.89-100
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• 2021

This paper deals with the construction of a combustion test facility and preliminary tests for hot-firing tests of a methane engine. First, the combustion test facility for a 1 kN-class thrust chamber using liquid oxygen/gas methane as propellants was designed and built. Before hot-firing tests, the cold-flow tests of each propellant line and the ignition tests of torch igniter/afterburner were performed to verify propellant supply stability of the combustion test facility, operation of the control and measurement system, and successful ignition. Finally, a preliminary hot-firing test was conducted to measure the combustion efficiency, heat flux, and combustion stability of a thrust chamber prototype. The constructed combustion test facility will be helpfully used for basic research and development of methane engine thrust chambers.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.66-78
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• 2021

In this study, the effect of Symmetry Breaking was compared according to the equivalent ratio condition and the number of nozzles where combustion instability occurs in an annular combustor. Generally, due to the relatively short combustor length, a longitudinal instability was less likely to occur in the annular combustor, but the combustion instability sometimes happens when ducts such as transition piece in gas turbine power station are present. In this case, due to the duct, only the longitudinal instability mode is observed. The characteristics of Symmetry Breaking were investigated according to the number of five lean nozzles and the equivalent ratio combination, and as the equivalent ratio decreased, the effect of Symmetry Breaking rapidly occurred, and the instability was dramatically disappeared and the amplitude was greatly reduced. In addition, it was confirmed that as the number of lean nozzles increased, a phenomenon such as a reduction in the equivalent ratio appeared.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.14-25
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• 2021

An experimental study was conducted on the spray characteristics of the pintle injector by opening distance. The discharge coefficient of the pintle injector was investigated and the spray angle was measured by taking the spray image by test conditions. As a result of the measurement of the discharge coefficient, it was confirmed that the change in the discharge coefficient of the outer injector was not significant over the experimental conditions, but the change in the discharge coefficient of the inner injector was decreased as the flow rate increased. Measurement of the spray angle showed that the change in the spray angle was not significant in the conditions under which the spray was fully developed, but the spray was not fully developed at low flow rates. This confirmed the possibility of thrust control using the pintle injector.