• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.290-297
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• 2016

A two-phase Large Eddy Simulation(LES) has been conducted to investigate breakup and atomization of a liquid jet in a cross turbulent flow in a rectangular duct. Gas-droplet two-phase flow was solved by a coupled Eulerian-Lagrangian method which tracks every individual particles. Effects of liquid breakup models, sub-grid scale models, and a order of spatial discretization was investigated. The penetration depth in cross flow was comparable with experimental data by varying breakup model and LES scheme. SMD(Sauter Mean Diameter) distribution downstream of jet was analyzed.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.54-61
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• 2007

Propellant pressurization system in liquid rocket propulsion system plays a role supplying pressurant gas at a controlled pressure into the ullage space of propellant tanks. The most important design parameter for such propellant pressurization system is the temperature of pressurant gas fed from pressurant tank. Such pressurant is gaseous state, of which density is very sensitive to the temperature of pressurant. Generally for the propulsion system, which requires high thrust and is consisted of cryogenic propellant the pressurant is stored at high density and high pressure to reduce the weight of pressurant tanks, which are placed inside of cryogenic propellant tank. That is called cryogenic storage pressurization system. This study investigates the temperature variation of pressurant at the time when the pressurant is coming out of pressurant tank experimentally as well as numerically. Fluids used in this study are air and liquid oxygen as outer fluid and gaseous nitrogen and gaseous helium as pressurant respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.59-70
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• 2021

An experimental study was conducted to observe the spray characteristics for different flow rates and rotating speeds of a rotating fuel nozzle of a slinger combustor. The water spray ejected from the nozzle orifice was visualized using a high-speed camera and a light source. It was confirmed that the atomization was improved, as the flow rate decreased and rotating speed increased. The characteristic maps for the spray characteristics and performance parameters showed that the aerodynamic Weber number and the liquid-air momentum flux ratio were associated with the liquid primary breakup, and the liquid-air momentum flux ratio and Rossby number were closely correlated with the liquid ejection mode.

• Journal of Mushroom
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• v.10 no.1
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• pp.3-8
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• 2012

In this study, to produce Flammulina velutipes mushroom liquid spawn efficiently and effectively the effects of explosive aeration (supplying air with tiny bubbles) of the liquid culture medium on carbon dioxide concentration and residual sugar content in the medium on carbon dioxide concentration and residual sugar contentin the medium were measured. Carbon dioxide concentrations were measured at the outlet of the incubator. On the third day the explosive aeration greatly increased mycelial growth of the liquid spawn, and carbon dioxide concentration also greatly increased but decreased after 5 days. Free sugar contents in the liquid culture consistantly decreased up to 7 days and thereafter was not detected. The weight of the mycelia were maintained similar levels after 3 days. Total nitrogen content in the liquid medium constantly decreased during the 11days of explosive aeration. The content of free sugars in 7 days of culture was the lowest level, thus the inoculum incubated for 6~7 days was thought to be the most effective. Carbon dioxide concentration measurement at the outlet of the container during the liquid spawn incubation required low cost but was efficient to estimate the degree of mycelial growth to be used as a simple indicator.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.485-496
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• 2015

The present study presents experimental results on the characteristics of emission spectra of kerosene/air swirl flames. The aviation fuel Jet A-1, which is used for the liquid rocket engines of the Korea Space Launch Vehicle, is used with three different swirlers to investigate the swirl strength effects. The emission spectra from the flames are measured with a spectrometer as the swirl strength and combustion air temperature are varied. Chemiluminescence intensities of $OH^*$, $CH^*$ and $C_2{^*}$ are identified from the spectra. The chemiluminescence intensities from the kerosene flames show sensitivity to the swirl strength and are affected by changes in the combustion air temperature. Among the three radicals of interest, $C_2{^*}$ show the most significant changes in chemiluminescence intensity with the swirl strength and equivalence ratio. The intensity ratios $I_{OH^*}/I_{CH^*}$ and $I_{C_2{^*}}/I_{CH^*}$ are adequate for indicating changes in the equivalence ratio with the air and fuel mass flow rates, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.39-45
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• 2006

In liquid rocket engine turbopump, it is difficult to evaluate turbine performance for high pressure, high temperature circumstance. Turbine test is often done by using air at similarity condition so that the turbine can be tested at lower risk. This paper describes an air similarity test program of liquid rocket engine turbopump turbine. A test facility has been built to evaluate aerodynamic performance of turbines. The test facility consists of high pressure air supply system, mass flow rate measuring nozzle, test section, hydraulic break, exit orifice for pressure control, instrumentation and control system. This paper also presents how to decide the similarity conditions of the turbine test and describes how to control test conditions. Relative standard deviation of measurement parameter was less than 1% and measured turbine efficiency corresponded with analysis result within 2%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.12
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• pp.48-58
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• 2006

The spray and combustion characteristics of liquid jet in cross flow with variation of injection angle are numerically studied. Numerical analysis was carried out using KIVA code, which may be used to generate numerical solutions to spray and chemical reactive fluid problem in three space dimensions and modified to be suitable for simulating liquid jet ejected into the cross flow. Wave model and Kelvin- Helmholtz(KH) /Rayleigh-Taylor(RT) hybrid model were used for the purpose of analyzing liquid column, ligament, and the breakup of droplet. Penetration length increases as flow velocity decreases and injection velocity increases. Numerical error increases as inflow velocity increases. The results of flame propagation contour in combustion chamber and local temperature distribution, combustion emissions were obtained.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.9
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• pp.948-954
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• 2008

Membrane bioreactor(MBR) processes have been widely applied to wastewater treatment for last decades due to its excellent capability of solid-liquid separation. However, membrane fouling was considered as a limiting factor in wide application of the MBR process. Excess aeration into membrane surface is a common way to control membrane fouling in most MBR. However, the excessively supplied air is easily dissipated in the reactor, which results in consuming energy and thus, it should be modified for effective control of membrane fouling. In this study, cylindrical tube was introduced to MBR in order to use the supplied air effectively. Membrane fibers were immersed into the cylindrical tube. This makes the supplied air non-dissipated in the reactor so that membrane fouling could be controlled economically. Two different air supplying method was employed and compared each other; nozzle and porous diffuser which were located just beneath the membrane module. Transmembrane pressure(TMP) was monitored as a function of airflow rate, flux, and ratio of the tube area and cross-sectioned area of membrane fibers(A$_m$/A$_t$). Flow rate of air and liquid was regulated to obtain slug flow in the cylindrical tube. With the same flow of air supply, nozzle was more effective for controlling membrane fouling than porous diffuser. Accumulation of sludge was observed in the tube with the nozzle, if the air was not suppled sufficiently. Reduction of membrane fouling was dependent upon the ratio, A$_m$/A$_t$. For diffuser, membrane fouling was minimized when A$_m$/A$_t$ was 0.27, but 0.55 for nozzle.

• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.481-487
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• 2009

In this of study, effects of input air velocity(0.05~0.22 m/sec) and molten carbonate salt temperature ($870{\sim}970^{\circ}C$) on flow regime transition have been studied by adopting a drift-flux model of air holdup and a stochastic analysis of differential pressure fluctuations in an air-molten sodium carbonate salt two-phase system(molten salt oxidation process). Air holdup where the flow regime transition begins was determined by air holdup-drift flux plot. The air holdup value which the flow regime transition begins was increased with increasing molten carbonate salt temperature due to the decrease of viscosity and surface tension of molten carbonate salt. To characterize the flow regime transition more quantitatively, differential pressure fluctuation signals have been analyzed by adopting the stochastic method such as phase space portraits and Kolmogorov entropy, The Kolmogorov entropy decreased with an increasing of molten carbonate salt temperature but increased gradually with an increase in an air velocity, however, it exhibited different tendency with the flow regime and the air velocity value which flow regime transition begins was same to the results of drift-flux analysis.

• Journal of Digital Convergence
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• v.10 no.5
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• pp.283-288
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• 2012

This study was undertaken to investigation the spray characteristics of the twin fluid atomization nozzle system. The light oil was injected at the normal temperature and injection pressure was 5 bar - 10 bar by 1 bar and volume flow was 0.5, 1.0 and 2,0 mmH2O(X10-2). We measured the SMD of sprayed droplet to study spray characteristics. The following conclusions were reached from the results of these study. 1. The more injection pressure increased, the more SMD decreased. 2. The more measuring distance between pressure nozzle tip and analyser beam increased, the more SMD increased. 3. SMD of the blower-air-added injection system were shown, increasing volume flow decreased respectively. The result of this study indicated the blower-air-added injection system induced beneficial changes in SMD. And it will be considered important indicator for spray characteristics design and performance evaluation of twin fluid atomization nozzle system.