• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1992.04a
• /
• pp.335-340
• /
• 1992

유압 시스템(System)은 원동기의 기계적 에너지를 유압펌프가 작동유를 압력 에너지의 형태로변환 시켜 이것을 유합 실린더(Cylinder)등의 엑츄에이터(Actuator)가 다시 기계적 에너지로 변환시켜 부하 를 구동하게한다. 상용차(NT-1, KH 등)용 파워스티어링(Power Steering)에 장착되는 Vane Type Oil Pump (이하 VOP)가 바로 이와같은 역할을 담당하고 있다. 본 연구에서는 VOP의 성능과 관련되어지는 주요 제원(Parameter)인 미끄럼부에서의 틈새, 작동유점도, 압력변화, 회전수 등을 다양하게 변화시키는 모의실험(Simulation)을 통하여각각의 조건하에서얻어지는 누설 유량과 체적효율을 수치적 으로 예측하고 이것을 주요제원을 고려하여 해석해서 정량적인 값을 얻는 것을 목적으로한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1999.10a
• /
• pp.6-6
• /
• 1999

액체 로켓 엔진은 추진기관 공급 시스템으로 작동이 된다. 추진기관 공급 시스템에는 유공압장치 및 각종 배관, 필요한 압력과 유량을 연소실과 가스발생기로 공급하는 시스템, 엔진의 점화 및 정지, 발사체의 사용 목적에 따라 부과되는 기능을 수행하기 위한 장비들이 포함된다. 공급시스템은 크게 가압가스를 이용하는 방법과 터보펌프를 이용하는 방법의 두 가지로 나눌 수 있다. 잘 알려진 바와 같이 일반적으로 추력이 큰 로켓엔진의 경우에는 터보 펌프식이, 추력이 크지 않은 경우에는 가압가스 방식이 이용된다. 일반적으로 가압가스 방식은 연소실 압력이 커질수록 추진제 탱크의 압력도 커지므로, 그 두께가 두꺼워져서 비효율적이 된다. 따라서 연소실 압력이 비교적 크지 않은 추력이 약 10t 내외에서 많이 사용되고, 시스템이 터보 펌프식보다 구조가 매우 간단하므로, 작동의 신뢰도는 매우 높다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.7
• /
• pp.510-517
• /
• 2016

Supersonic jet technology using high pressures has been popularly utilized in diverse industrial and engineering areas related to working fluids. In this study, to consider the effects of a shock wave caused by supersonic jet flow from a high pressure pipe, the SST turbulent flow model provided in the ANSYS FLUENT v.16 was applied and the flow characteristics of the pressure ratio and Mach number were analyzed in accordance with the working fluids (air, oxygen, and hydrogen). Before carrying out CFD (Computational Fluid Dynamics) analysis, it was presumed that the inlet gas temperature was 300 K and pressure ratio was 5 : 1 as the boundary conditions. The density function was derived from the ideal gas law and the viscosity function was derived from Sutherland viscosity law. The pressure ratio along the ejection distance decreased more in the lower density working fluids. In the case of the higher density working fluids, however, the Mach number was lower. This shows that the density of the working fluids has a considerable effect on the shock wave. Therefore, the reliability of the analysis results were improved by experiments and CFD analysis showed that supersonic jet flow affects the shock wave by changing shape and diameter of the jet, pressure ratio, etc. according to working fluids.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.725-730
• /
• 2011

A 2-way solenoid valve regulates to maintain the pressure of ullage volume of propellant tanks when the command is given by control system for the liquid-propellant feeding system of space launch vehicle. The simulation model of solenoid valve for pressurization is designed with AMESim to verify the designs and evaluate the dynamic characteristics and pneumatic behaviors of valve. To validate a valve simulation model, the simulation results of their operating durations of valve by AMESim analysis are compared with the results of experiments. Using the model, we analyze performance of valve; opening/closing pressure, operating time on various design factors; shape of control valve seat, basic valve seat, rate of sealing diameter. This study will serve as one of reference guides to enhance the developmental efficiency of ventilation-relief valves with the various operating conditions, which shall be used in Korea Space Launch Vehicle-II.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.2
• /
• pp.128-134
• /
• 2013

A 2-way solenoid valve regulates to maintain the pressure of ullage volume of propellant tanks when the command is given by control system for the liquid-propellant feeding system of space launch vehicle. The simulation model of solenoid valve for pressurization is designed with AMESim to verify the designs and evaluate the dynamic characteristics and pneumatic behaviors of valve. To improve the accuracy of the model, numerical flow analysis by using FLUNET code. The simulation results of their operating durations of valve by AMESim analysis are matched up with the results of experiments and validate valve model. Using the model, we analyze performance of valve; opening/closing pressure, operating time on various design factors of basic valve and control valve; geometrical size of valve seat, ratio of basic valve and sealing area.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.11a
• /
• pp.393-396
• /
• 2006

This paper presents the characteristics of the performance parameters of dual mode(ramjet-scramjet combined) engine, inlet and combustor for wide range of flight Mach number, resulted from the analysis of its operating limitations. The transitional-critical flight Mach number from ramjet to scramjet and the performance of two types of combustors, such as constant pressure- and constant area- combustor, are conceptually evaluated.

• 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.

• Aerospace Engineering and Technology
• /
• v.13 no.2
• /
• pp.160-166
• /
• 2014

The shutoff valve of a Liquid Rocket Engines (LRE) controls the flow of propellant between turbo-pump and combustion devices of LRE using pilot pressure and spring force. The shutoff valve is closed when the pilot pressure is removed from the diaphragm type actuator. During designing process of life cycle is when should be analyzed according to the characteristics of forces with respect to the opening and closing of diaphragm actuator. A valve has been designed to adjust the control pressure which is required to open a poppet and to determine the working fluid pressure at which a valve starts to close. During flow capacity test under room temperature as a part of life cycle tests, the leakage in diaphragm was occurred due to the leakage of sheet welding sections. The operating cycle of the diaphragm type actuator is about 61 times with 22 MPa of pilot pressure.

• Fire Science and Engineering
• /
• v.30 no.1
• /
• pp.1-5
• /
• 2016

Cases of cardiac arrests due to cardiovascular ailments have increased recently., portable Current portable resuscitators which can be automatically supply oxygen operated by the pressure of supplied oxygen without manual or electronic actuators are now widely used in emergency worldwide. However, reductions in Pressure drop characteristics through the extended use of this type of resuscitator, however, is are not well-known described. This paper describes the reduction in pressure loss drop performance of the various holes in within the flow control disc of with various hole size of the portable resuscitators using on breathing resistance through the CFD simulation, and suggests the an optimum optimal design of the hole shapes for the minimization of alteration in order to minimize this pressure drops.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.10 no.3
• /
• pp.60-66
• /
• 2006

Notable are the burning rate characteristics of solid propellant burning at extremely high pressure(10000-20000 psia). The burning rate test using closed bomb shows the discontinuous increment around 4000 psia so that the exponent of burning rate(n) is almost double, from 0.4 to 0.8. The pressure-increasing rate of the test motor is about 300 times as high as that of the motor operating at the conventional pressure, less than 2000 psia, is, therefor the burning rate is augmented about 5-50 times. The performance prediction reflecting the pressure-change-rate effect are fairly comparable with the test data at various test conditions.