• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.88-94
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• 2002

For the pressurized propellant supply system of liquid rocket, feed pressure is determined with respect to the chamber pressure of normal combustion state. However, during ignition period the initial chamber pressure is atmosopheric. This may cause overflow, hard-start and even critical damage for the engine. This paper proposes an improved propellant feed system for the stable combustion of liquid rocket. The proposed system utilizes the cavitating venturi to provide stable mass flow rate. Cavitating venturi offers unique flow control capabilities at normal and abnormal combustion state, because flow rate is soley dependent on the upstream absolute pressure and fluid properties, but independent on th downstream condition. Experimental variables are propellant feed pressure and chamber pressure. The effectiveness of cavitating venturi increased when the ratio of actual feed pressure to the cavitating venturi design pressure is increased. It is also found that Kerosene if more effective to supply stable mass flow rate than LOx.

• International journal of advanced smart convergence
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• v.6 no.4
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• pp.1-8
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• 2017

In this work, the effects of fairly influential factors on performance of vacuum system, such as constant pressure and outgassing effect were simulated to propose the optimum design factors. Outgassing effects of selected vacuum materials on the vacuum characteristics were simulated by the $VacSim^{Multi}$ simulation tool. This investigation examined the feasibility of reliably simulating the outgassing characteristics of common vacuum chamber materials (aluminum, copper, stainless steel, nickel plated steel, Viton A). The optimum design factors for vacuum systems were suggested based on the simulation results. And, the effects of throttle valve applications on vacuum characteristics were also simulated to obtain the optimum design model of variable conductance on high vacuum system. Simulated vacuum characteristics of the proposed modelling were agreed with the observed experimental behaviour of real systems. Pressure limit valve and normally on-off control valve were schematized as the modelling of throttle valve for the constant process-pressure. Simulation results were plotted as pump-down curve of chamber and variable conductance of throttle valve. Simulated behaviors showed the applications of throttle valve sustained the process-pressure constantly, stably, and reliably.

• Journal of ILASS-Korea
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• v.2 no.1
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• pp.18-28
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• 1997

The present study is mainly aiming at numerically analyzing the combustion and emission characteristics of the diesel spray in a high-pressure environment. Computations are peformed for the peak chamber pressure with range from 4.08 MPa to 162 MPa. Numerical results indicate that the pressure increase in combustion chamber significantly influences the mechanism for droplet dynamics and mixing characteristics, spray penetration autoignition, flame lift-on height and the propagation or fuel vapor and flame. By increasing the ratio or the ambient density to injected liquid density, the fuel-air mixing rates and the burning rates increase and the $NO_x/soot$ emission level decreases.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.11
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• pp.883-889
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• 2014

Mufflers have been widely used in the exhaust system to reduce the noise. However, installing muffler may deteriorate the efficiency due to the increase of back pressure. Mufflers usually consist of partition plates and perforated holes in a expansion chamber. In this paper, the influences of the location of the partition and hole on the acoustic TL and back pressure were examined. The acoustic TL was predicted using virtual lab commercial software, while the back pressure were predicted using CFX commercial software. The results were used to set up a database for finding their trends. The optimal muffler model in user-interested frequency range could be selected by analyzing this database.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.3
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• pp.259-264
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• 2019

In this study, we experiment by making and designing of compression ignition diesel engine witch has air cooling, 2-cylinder and 2-strokes. Also, we make controller witch can control injection timing and period by arbitrary manual operation for change of injection timing. We also study experimentally in change about pressure and power of combustion chamber by increasing density of air which comes into cylinder because of increasing scavenging pressure. Through this, we confirmed that output change and scavenging pressure can develop performance of the engine by scavenging efficiency of a chamber and development of volume efficiency.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.150-161
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• 2005

A test was performed to collect the data to validate an analytic method for vent hole sizing on the nose fairing of a launch vehicle. The bake-out chamber at KARI was used to simulate the ambient pressure drop, and pressure difference data were collected for a model with various kinds of vent holes which was installed in the chamber. The characteristics of the test facility and measurement equipments were evaluated for the measurement of the transient behaviors. The measured data were processed in consideration of the characteristics of the facility and equipments, and the effects of vent hole size and configuration on the pressure variation in the model were analyzed based on the data.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.1-8
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• 2004

A cylindrical constant volume combustion chamber was used to investigate the exhaust emission characteristics of homogeneous charge, stratified pattern and inhomogeneous charge under various conditions using gas chromatography. In the case of homogeneous charge condition, the $CO_2$ concentration is proportional to excess air ratio and overall charge pressure, the $CO_2$ concentration is proportional to excess air ratio and the UHC concentration is inversely proportional to ignition time and overall charge pressure. In the case of stratified pattern, the RI(rich injection) condition shows better exhaust emission characteristics, especially $CO_2$, than that of HI (homogeneous injection) or LI (lean injection) conditions. In inhomogeneous charge conditions, when initial charge pressure is increased, $CO_2$ and UHC concentration is reduced but $O_2$ concentration is increased. And when the excess air ratio of initial charge mixture is 3.0, UHC and $CO_2$concentration show lowest values.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.6
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• pp.788-794
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• 2002

In liquid rocket engine, propellant feed rate is proportional to approximately square root of the pressure difference between injector head and combustion chamber. This ΔP depends on the engine design, but in general on the order of 50psi. However, during ignition period, especially for the pressurized feed system, combustion chamber pressure is almost atmospheric and large ΔP causes over flow of propellants which may lead to catastrophic accident due to hard start. Hard start may be prevented by applying cavitating venturi or/and two step ignition. In cavitating venturi, evaporated propellants near the venturi throat become chocked and flow rate depends on only upstream condition. In two step ignition propellants are supplied to the liquid engine in two different flow rate. First step, to avoid hard start, small amount of propellants are supplied to build up chamber pressure in safe zone, then full propellants to ensure design pressure. In this study, both cavitating venturi and two step ignition method were used for the hot test and hard start problem was completely solved.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.49-52
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• 2009

The response times of monopropellant thrusters at a pulse mode were investigated experimentally as design parameters and feed pressure conditions. Five different model thrusters as injection direction/uniformity, aspect ratio of reactor, volumes of manifold and chamber were designed. As a results, two parameters, aspect ratio and manifold volume, were directly related to response characteristics. Additionally, chugging instability at reaction chamber was observed when pressure drop across the catalyst bed was increased due to high aspect ratio or when low pressure was built at reaction chamber.

• Journal of ILASS-Korea
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• v.6 no.1
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• pp.25-34
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• 2001

Several efforts to meet the exhaust gas regulation have been undertaken by many researchers in recent years. Main researches are on development of design techniques of intake port and combustion chamber, atomisation of fuel and precise control of air-fuel ratio, post-treatment of exhaust gas and so on. Engine technology is changed from PFI to GDI to correspond with exhaust gas regulation. GDI technique makes it possible to preserve lean air-fuel ratio and control accurate air-fuel ratio. Nevertheless, It is not cleared that information of spray characteristics and atomization process are very dependent on fluctuation of pressure and change of temperature in intake stroke. In this study, a constant volume combustion chamber is manufactured to investigate various fluctuations of in-cylinder pressure for injection duration. It is taken photographs of injection process of conventional GDI injector using PMAS. Then, it was verified experimently that ambient conditions as temperature and pressure of combustion chamber have effects on process of spray growth and atomization of fuel.