• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.28-34
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• 2001

Great attentions are paid to HSDI diesel engine for passenger cars because of its high thermal efficiency. The most interesting research in HSDI diesel engine developments is focused on applying common rail system as a fuel injection equipment. In this study, a series of tests are carried out to investigate the effect of injection pressure variation on the smoke and fuel concluded in a small HSDI diesel engine with common rail system. As a result of this study it is concluded that there is an optimum rail pressure dependent on combustion system such as nozzle type, combustion chamber geometry.

• Journal of ILASS-Korea
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• v.9 no.2
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• pp.1-8
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• 2004

This work was performed to investigate the distribution of the fuel droplet size around the bluff-body and the combustion characteristics. The geometry of the bluff-body influenced the spray shape and the combustion characteristics. Diameters of the bluff-body in this experiment are 6, 8, and 10 mm and the impingement $angles({\theta})\;are\;30^{\circ},\;60^{\circ},\;and\;90^{\circ}$. The measurement points were at the distances of 20 and 30 mm axially from the nozzle. The SMD and Rosin-Rammler distribution was acquired by image processing technique (PMAS), and the mean temperatures were measured by thermocouple. The results obtained are as follows; In the condition of ${\theta}=60^{\circ}$, the values of SMD are not greatly varied compared to the other conditions. As the impingement angle of bluff-body was increased, the high temperature region was wider along radial direction. When the air-fuel ratio was increased, the CO concentration was decreased.

• Journal of the Korean Society of Combustion
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• v.14 no.4
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• pp.48-53
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• 2009

This paper describes the forced flame response in a turbulent premixed gas turbine combustor. The fuel was premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. To impose the inlet flow velocity, a siren type modulation device was developed using an AC motor, rotating and static plates. Measurements were made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The test results showed that flame length as well as geometry was strongly dependent upon modulation frequency in addition to operating conditions such as inlet velocity. Convection delay time between the velocity perturbation and heat release fluctuations was calculated using phase information of the transfer function, which agreed well with the results of flame length measurements. Also, basic characteristics of the flame nonlinear response shown in the current test conditions were introduced.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.49-53
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• 2003

In this study, the geometric design parameters of ejector system were investigated. The critical parameters were primary nozzle area ratio, 2nd-throat cross sectional area and 2nd-throat L/D ratio. At every geometry cases, primary pressure and secondary pressure were measured simultaneously according to secondary mass flow rate. From the results, the ejector starting pressure, unstarting pressure and minimum secondary flow pressure were found and we got the effect of geometric parameters to ejector performance and the way to optimal design of ejector system for chemical lasers operating. Also the experiments of changing secondary flow temperature were carried out.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.147-150
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• 2003

The purpose of this research was to develope components of micro solid propellant thruster. Micro solid propellant thruster had four basic components: combustion chamber, nozzle, solid propellant and micro heater for ignition. A performance of micro heater and characteristic of solid propellant was investigated. Micro heater was fabricated by conventional MEMS process and Platinum layer was used for heating element. Effect of geometry parameters on micro heater was tested. The temperature responses of heater with respect to each parameters was compared for a given electrical power. The characteristic of solid propellant(HTPB/AP) was investigated to obtain burning velocity in small chamber. Additionally, a capacity of filling propellant with high viscosity in small chamber was checked to guarantee for the micro fabrication.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.1
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• pp.74-92
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• 2000

A numerical analysis has been conducted to study the transient flowfield during the transition from the booster to sustainer phase in an integrated rocket ramjet (IRR) propulsion system. Emphasis is placed on the unsteady inlet aerodynamics, fuel/air mixing in an entire ramjet engine during the flow transient phase. The computational geometry consists of the entire IRR engine, including the inlet, the combustion chamber, and the exhaust nozzle. Turbulence closure is achieved using a low-Reynolds-number two-equation model. The governing equations are solved numerically by means of a finite-volume, preconditioned flux-differencing scheme over a wide range of Mach umber. Various important physical processes are investigated systemically, including terminal shock train.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.213-220
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• 1998

The conventional discrete-ordinates method (DOM) is modified and developed for the analysis of two-dimensional axisymmetric cylindrical enclosure with curved wall. The objective of the present work is to extend the capability of the conventional DOM into a general axisymmetric geometry like nozzle-shaped enclosure, by adopting the arbitrary control angle as was done in the finite-volume method (FVM), while keeping the same two-dimensional solution procedure as in the conventional DOM. The present method is validated by applying it to three different benchmark problems of axisymmetric enclosure containing absorbing, emitting and scattering medium. Results presented in this work not only support the solution accuracy, but also moderate efficiency in the numerical calculation of axisymmetric radiation problem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.387-395
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• 2013

Recently, several circumferential cracks were found in the control rod drive mechanism (CRDM) nozzles of U.S. nuclear power plants. According to the accident analyses, coolant leaks were caused by primary water stress corrosion cracking (PWSCC). The tensile residual stresses caused by welding, corrosion sensitive materials, and boric acid solution cause PWSCC. Therefore, an exact estimation of the residual stress is important for reliable operation. In this study, finite element simulations were conducted to investigate the effects of the tube geometry (thickness and radius) on the residual stresses in a J-groove weld for different CRDM tube locations. Two different tube locations were considered (center-hole and steepest side hill tube), and the tube radius and thickness variables ($r_o/t$=2, 3, 4) included two different reference values ($r_o$=51.6, t=16.9mm).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.627-630
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• 2009

Ejector system can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an configuration and operating conditions for an ejector in the condition of sonic and subsonic. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Numerical simulation was adopted for an optimal geometry design and satisfying the required performance. Also, some ejectors with a various of nozzle throat and mixing chamber diameter were manufactured precisely and tested for the comparison with the calculation results.

• Journal of ILASS-Korea
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• v.11 no.4
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• pp.251-265
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• 2006

To prevent the ozonosphere from being destroyed by Halon, it is an urgent task to find out Halon replacement. As one of the replacements water mist have showed broad applications by its advantages: little pollution to environment (not destroying the ozone layer or bring green house effect), extinguishing fire quickly, consuming a small quantity of water and having little damage to the protected objects. The methods of generating water mist strongly influence fire suppression effectiveness, which determine the cone angle, drop size distribution, flux uniformity, and momentum of the generating spray. The traditional water mist nozzle included pressure jet nozzles, impingement nozzles and twin-fluid nozzles. All of them have more or less disadvantages for fire suppression. Therefore, many research institutes and corporations are taking up with innovations in mist generation. This article provided some recent studies in State Key Laboratory of Fire Science (SKLFS) of University of Science and Technology of China. SKLFS have investigated new methods of generating water mist (i.e. effervescent atomization and ultrasonic atomization). and self developed a series of nozzles and developed advanced DPIVS (Digital Particle Image Velocimetry and Sizing) technique. Characteristics of water mist (the distribution of droplet sizes, flux density, spray dynamics and cone angle) produced by these nozzles were measured under different conditions (work pressure, nozzle geometry, etc.) using LDV/APV and DPTVS systems. A series of experiments were performed to study the fire suppression effectiveness in different fire scenario (different kindsof the fuel, fire size and ventilation conditions). The fire extinguishing mechanisms of water mist was also discussed.