• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.5
• /
• pp.79-87
• /
• 2002

Acoustic responses to pressure oscillations in axisymmetric combustion chamber are numerically investigated to examine the qualitative trend of acoustic instability in liquid rocket engine. Chamber operating condition and excitation frequency of oscillating pressure are selected as exciting parameters of acoustic instability. Artificial perturbation is simulated by total-pressure oscillation with sine wave at chamber inlet. Many approximations and simplifications are introduced without losing the essence of acoustic pressure response. First, steady-state solution for each operating condition is obtained and next, transient analysis is conducted. Depending on operating condition and excitation frequency, the distinct response characteristics are brought. Weak-strength flames and high-frequency excitation tend to cause sensitive acoustic pressure response leading to unstable pressure field. These results are analyzed based on the correlation with acoustic pressure responses from the previous works adopting laminar flamelet model.

• Journal of Aerospace System Engineering
• /
• v.14 no.5
• /
• pp.91-99
• /
• 2020

A liquid rocket engine goes through many tests to prove its performance before liftoff. It means the tests for setting ignition and start-up conditions or a test on design condition, which verifies the design performance. However, the development process requires verification of performance under off-design conditions through tests involving different operating conditions, which affects the duration of engine development. The off-design performance test is performed by altering the conditions of the propellant supplied to the engine in conjunction with the engine performance test that varies the opening of the control valves in the engine. This paper is based on the results of the engine tests performed at the KSLV-II engine test facilities in the Naro Space Center and describes the operations of the test facility for off-design condition test that changes the inlet conditions of the turbo-pump due to changes in the pressure and temperature of the propellant supplied to the test engines.

• Journal of Power System Engineering
• /
• v.7 no.4
• /
• pp.25-30
• /
• 2003

Hydrocyclone has been widely used for the solid-Liquid separation in many industrial sites because of its comparatively preferable applications that can be applied to wide-range panicle sizes. If seawater with impurities flows through pumps or heat exchanger, it might cause an decrease in efficiency of cooling system. In this paper, we have suggested solid methods of separating impurities from seawater in the cooling system by using a Hydrocyclone. The effects of design factors as solid concentration, cyclone inlet pressure, flow rate and diameter of underflow on the seperating performance of the Hydrocyclone were investigated. The results from the study are summarized as follows: 1) In proportion to the increase of solid concentration, the efficiency of solid-liquid separation is improved. 2) According as the cyclone inlet pressure increases the efficiency of separation is improved. Conclusively, this research suggested that the Hydrocyclone will be used as a pre-treatment system of cooling water in ships, and eventually prevent unexpected accidents in engine systems.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.399-404
• /
• 2010

Test results including the variation of propellant-inlet pressure, pulsed thrust, and environment vacuum with the accompanying thermal responses are presented for the pulse-mode operation of a set of monopropellant hydrazine thrusters producing $0.95lb_f$ of nominal steady-state thrust at an inlet pressure of 350 psia. The test data are reduced into the impulse bit, specific impulse, and force centroid that are the factors typically characterizing pulse-mode performance of small rocket engines. With a scrutiny to the performance parameters, their comparison to the reference criteria of 1 lbf standard monopropellant rocket engine are successfully made.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.631-636
• /
• 2001

The internal flow in the rocket pump inducer of LE-7 engine for H-II rocket was predicted at design and off-design flow rates using CFD code, CFX- Tascflow. In this numerical study, the performance curve of inducer coressponding to flow rates variation and the internal flow in the front of blade leading edge show good agreement between the calculations and the measurements. Backflow is appeared at suction side of leadinge edge tip, and this region is extended to upstream as flowrate decrease. Because of backflow, pressure loss coressponding to meridinal coordinate occupy 50% from inlet domain to leading edge. By this phenomena, pressure loss in front of blade leading edge take a great effect to inducer performance.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.2
• /
• pp.196-201
• /
• 2012

This study represents numerical study on the thermal and fluid flow characteristics of exhaust gas in a motorcycle muffler. The engine generates 125cc of displacement. Numerical analysis with computational fluid dynamics(CFD) was carried out to investigate the exhaust gas that flow into a motorcycle muffler. The STAR-CD S/W used to analyze three dimensional steady state and transient in a muffler. The Navier-Stokes Equation is solved with SAMPLE and PISO method in cartesian coordinates system. As the numerical result, it could be confirmed pulsating pressure generated from inlet of muffler become closer to the atmospheric pressure through baffle. Also the numerical result was almost identical to experimental result and, through the comparison, the reliability of numerical result was confirmed.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.5
• /
• pp.36-43
• /
• 2012

In this work the mixing and flow characteristics of a vane-type static mixer were investigated numerically for the reduction of NOx in the SCR-system of the diesel engines. The mixer was located in the 57 times pipe diameter away from the inlet. The analysis were performed by changing such various parameters as vane shape, angles, blockage ratio and location of the vane. The flow structure through the mixer was characterized by uniformity index and pressure drop. The results show that uniformity index and pressure coefficient are substantially influenced by the vane shape, angle, blockage ratio and position of the vane of the mixer.

• Korean Journal of Chemical Engineering
• /
• v.35 no.11
• /
• pp.2164-2171
• /
• 2018

Heavy duty diesel vehicles deteriorate urban air quality by discharging a large volume of air pollutants such as soot and nitrogen oxides. In this study, a newly introduced auxiliary device a fuel activation device (FAD) to improve the combustion efficiency of internal engines by utilizing the cavitation effect was closely investigated by the fluid flow mechanism via a numerical analysis method. As a result, the FAD contributed to fuel atomization from the injection nozzle at lower inlet pressure by reducing the pressure energy. The improved cavitation effect facilitated fuel atomization, and ultimately reduced pollutant emission due to the decrease in fuel consumption. The axial velocity along the flow channel was increased 8.7 times with the aid of FAD, which improved the primary break-up of bubbles. The FAD cavitation effect produced 1.09-times larger turbulent bubbles under the same pressure and fuel injection amount than without FAD.

• The KSFM Journal of Fluid Machinery
• /
• v.18 no.2
• /
• pp.22-28
• /
• 2015

The primary design goal of a compressor is focused on improving efficiency. Secondary objective is to widen the operating range of compressor. This paper presents a numerical and experimental investigation of the influence of the bleed slot on the operating range for the 1.2 MW class centrifugal compressor installed in a turbocharger. The main design parameters of the bleed slot casing are upstream slot position, inlet pipe slope, downstream slot position and width. The DOE(design of experiment) method was carried out to optimize the casing design. Numerical analyses were done by the commercial code ANSYS-CFX based on the three dimensional Reynolds-averaged Navier-Stokes equations. Results showed that efficiency and pressure ratio increased as the downstream slot position and width were smaller and the upstream position was located away from the impeller inlet. Experimental works were also done with and without the bleed slot casing. The simulation results were in good agreement with the test data. Enhancement of both the surge margin up to 26.5% and the pressure ratio with the optimized bleed slot design were achieved, compared with the surge margin of only 6.6% without the bleed slot casing.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.4
• /
• pp.61-67
• /
• 2018

High-frequency signals are analyzed at the inlet/outlet pipeline and pump casing during cavitation tests of the LOx pump for liquid rocket engines. Root-mean square values of all data are investigated with respect to cavitation number. The values of synchronous, harmonic, and cavitation instability frequencies are also calculated. Pressure pulsations of the inlet and outlet pipelines are affected by cavitation instabilities. The 3x component (i.e., the blade-passing frequency of the inducer) is predominant in the outlet pulsation sensor. This seems to be related to the fact that the number of impeller blades is a multiple of the number of the inducer blades. The cavitation instability is also measured at the accelerometer of the pump casing.