• 한국전산유체공학회:학술대회논문집
• /
• 2001.05a
• /
• pp.144-148
• /
• 2001

Characteristics of high temperature rocket nozzle flow is discussed along with the aspects of computational analysis. Three methods of nozzle flow analysis, frozen-equilibrium, shifting-equilibrium and non-equilibrium approaches, were discussed those were coupled with the methods of computational fluid dynamics. A chemical equilibrium code developed for the analysis of general hydrocarbon fuel was coupled with three approaches of nozzle flow analysis, and a test was made for a bell nozzle at typical operation condition. As a results, the characteristics of the approaches were discussed in aspects of rocket performance, thermal analysis and computational efficiency.

• Journal of Advanced Marine Engineering and Technology
• /
• v.28 no.2
• /
• pp.163-184
• /
• 2004

Vortex flow fundamentals have been investigating for about hundred years and many distinguished features had been discovered and comprehensively studied over that time. Due to unique hydrodynamic features vortex flows are now widely used in many industrial applications, including energy and power systems. combustion chambers. fuel sprayers. heat exchangers. clean-up systems. drying chambers. Up to recently aerospace engineers employed vortex flow only in combustion systems to stabilize a flame zone or in advanced heat exchangers to enhance heat transfer processes. This paper provides an overview of some recently developed aerothermal vortex technologies applied to aerospace engineering.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1993.10a
• /
• pp.55-61
• /
• 1993

An experimental investigation was conducted in order to determine the flammability limit of the solid fuel ramjet using the backward facing step flow combustion of the plexiglass grain. In order to get the different step height ratio, the grain was drilled straight forward or stepwise. The Phoenics computer code was adopted in order to compare. the flow patterns of the some sample tests using a non-reacting cold turbulent flow model. The stepwise grain give some loading advantage; specially thin and long shape grain design.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.3 no.2
• /
• pp.18-24
• /
• 1999

Liquid ramjet combustor is closely connected with complex phenomena due to a series of processes such as intake air, spray, mixing, and combustion. The present numerical experiments were peformed to investigate these flow characteristics for two and three dimensional liquid ramjet combustor. Grid system was made with three domains: intake region where air is supplied and fuel is injected, combustor and nozzle region, and exit atmosphere region. The numerical results showed that two and three dimensional flow patterns in recirculation region of combustor were significantly different each other and spray model was necessary to predict correctly the chemical reaction flow characteristics. Numerically examined for two different location of fuel injector, one is located on the bottom position of curved intake and the other is located on the top position. We found that bottom position of fuel injector is better than top position because fuel influx to the recirculation region which is need to sustain chemical reaction is more than the latter.

• International Journal of Aeronautical and Space Sciences
• /
• v.13 no.3
• /
• pp.386-397
• /
• 2012

The stability and structure of bluff-body stabilized hydrogen flames were investigated numerically and experimentally. The velocity of coflowing air was varied from subsonic velocity to a supersonic velocity of Mach 1.8. OH PLIF images and Schlieren images were used for analysis. Flame regimes were used to classify the characteristic flame modes according to the variation of the fuel-air velocity ratio, into jet-like flame, central-jet-dominated flame, and recirculation zone flame. Stability curves were drawn to find the blowout regimes and to show the improvement in flame stability with increasing lip thickness of the fuel tube, which acts as a bluff-body. These curves collapse to a single line when the blowout curves are normalized by the size of the bluff-body. The variation of flame length with the increase in air flow rate was also investigated. In the subsonic coflow condition, the flame length decreased significantly, but in the supersonic coflow condition, the flame length increased slowly and finally reached a near-constant value. This phenomenon is attributed to the air-entrainment of subsonic flow and the compressibility effect of supersonic flow. The closed-tip recirculation zone flames in supersonic coflow had a reacting core in the partially premixed zone, where the fuel jet lost its momentum due to the high-pressure zone and followed the recirculation zone; this behavior resulted in the long characteristic time for the fuel-air mixing.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.16 no.3
• /
• pp.301-306
• /
• 2010

DME(Di-Methyl Ehter, $CH_3OCH$) is currently attracting worldwide attention due to its environmentally friendly characteristics. Until now it was researched as a major alternative fuel of diesel automobile because it is a clean fuel producing low soot. Therefore, in this study, in order to investigate the effect of DME mixing on number density and size of soot particle, DME has been mixed in opposed-flow ethylene diffusion flame with the mixture ratios 5%, 14% and 30%. A laser extinction/scattering technique has been adopted to measure the volume fraction, number density, and size of soot particles. The experimental results showed that the soot concentration of mixture flames with the mixture ratios 5% and 14% produces soot more, even though that of 30% was decreased. This means that even though DME has been known to be a clean fuel for soot formation, the mixing of DME in diffusion flame of ethylene, where acetylene maintains high concentration in soot formation regions, could produce enhanced production of soot.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.4
• /
• pp.63-69
• /
• 2006

Experimental tests have been done with swirl injector and helical grain configuration to increase the regression rate of hybrid rocket solid fuel. Two types of injector were designed to evaluate the swirl effect of oxidizer stream on the increase in the regression rate. Results showed Type II injector with swirl number of 3.61 induced the better regression rate than Type I injector. Meanwhile, fuels with two different pitch number of 6 and 100 were used to analyzes the flow characteristics on the enhancement of regression rate. Test with fuels of pitch 6 showed better increase in the regression rate than in the pitch 100 when no swirler was imposed. This is due to the generation of strong turbulences in the oxidizer stream along the pitch 6 configuration. However, the regression rate could be increased further in the fuel with pitch 100 than with pitch 6 when swirl flow was imposed by Type II injector. This result implied that the fuel with pitch 100 could take a role of sustainer of the imposed swirl by swirler II instead of turbulence generator.

• Journal of Hydrogen and New Energy
• /
• v.27 no.1
• /
• pp.49-62
• /
• 2016

In this study, a solid oxide fuel cell (SOFC) system model including balance of plant (BOP) for building electric power generation is developed to study the effect of operating conditions on the system efficiency and power output. SOFC system modeled in this study consists of three heat-exchangers, an external reformer, burner, and two blowers. A detailed computational cell model including internal reforming reaction is developed for a planer SOFC stack which is operated at intermediate temperature (IT). The BOP models including an external reformer, heat-exchangers, a burner, blowers, pipes are developed to predict the gas temperature, pressure drops and flow rate at every component in the system. The SOFC stack model and BOP models are integrate to estimate the effect of operating parameters on the performance of the system. In this study, the design of experiment (DOE) is used to compare the effects of fuel flow rate, air flow rate, air temperature, current density, and recycle ratio of anode off gas on the system efficiency and power output.

• Korean Chemical Engineering Research
• /
• v.59 no.4
• /
• pp.481-486
• /
• 2021

In a hypersonic vehicle to solve the heat problem generated during flight, a cooling technology is being developed which uses the endothermic effect that appears during the decomposition reaction of the mounted fuel. In this study, the decomposition reaction of n-dodecane fuel was performed using HZSM-5 as a catalyst, and the catalyst was coated on metal foam to maximize the endothermic effect of the catalytic decomposition reaction and suppress coke formation. The reactor was a stainless steel flow reactor with a outer diameter of 1.27 cm, and the reaction temperature was 550 ℃, the reaction pressure was 4 MPa, and the flow rate was 12 ml per minute. As a result of the catalytic decomposition reaction using a catalyst coated with HZSM-5 on the metal foam, the heat sink was 2887 kJ/kg as a maximum, the gas phase conversion rate was 34%, and the amount of coke produced on the metal foam decreased by about 56% as the catalyst was coated compared to the uncoated catalyst.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.2
• /
• pp.32-38
• /
• 2004

This study was performed to investigate the behavior of liquid and vapor phase of fuel mixtures with different piston cavity diameters in a optically accessible engine. The conventional engine was modified as Central Injected DI gasoline engine with swirl motion. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze spray behavior and fuel distribution inside of cylinder using exciplex fluorescence method. Piston cavity geometries were set by Type S, M and L. The results obtained are as follows. In the spray formation after SOI, the cone angle and width of the spray were decreased at late injection timing. With a fuel injection timing of BTDC $180^{\circ}C$, fuel was not greatly affected in a piston cavity but generally distributed as homogeneous mixture in the cylinder. With a fuel injection timings of BTDC $90{\circ}C$ and $60^{\circ}C$, fuel mixture was widely distributed in near the cavity center. As a injection timing was late in the compression stroke, residual width of fuel mixture was narrow in proportion to piston cavity.