• Journal of the Korean Society of Combustion
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• v.22 no.3
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• pp.35-40
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• 2017

Jet aviation fuel is one of liquid fuel which are used in aircraft engines. Korean domestic jet fuel, called Jet A-1, is tested for measurement of ignition delay time by using a shock tube manufactured recently. The temperature varies from 680 to 1250 K and the pressure and equivalence ratio of Jet A-1/air are fixed 20 atm and 1.0, respectively, for this experiment. The ignition delay time data of Jet A-1 are compared with those of Jet A, which has similar properties to Jet A-1. The behavior of negative-temperature-coefficient (NTC) is observed in the temperature range 750-900 K. In addition, ignition delay time of iso-octane is measured, which is one of the surrogate components for jet aviation fuel. The experimental data are compared and validated with the previous results from the literatures. A surrogate fuel for the present Jet A-1 consists of 45.2% n-dodecane, 32.1% iso-octane, and 22.7% 1,3,5-trimethylbenzene. The predicted ignition delay time for the surrogate agrees well with the measured one for Jet A-1.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.33-39
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• 2021

Y-jet nozzle has a wide fuel flow rate range and turn-down ratio, thus, it is used in industrial boilers, furnace and agricultural atomizer. However, it has asymmetrical spray characteristics due to the nozzle design factors. Therefore, in this study, asymmetric spraying characteristics of the elliptical Y-jet nozzle was studied by using the lab-scale spray apparatus. As a result, the elliptical Y-jet nozzle had lower gas mass flow rate than circular Y-jet nozzle at same gas pressure, because of bigger shear stress due to the wider inner surface at the elliptical Y-jet nozzle. Larger SMD was measured on the elliptical Y-jet nozzle than the circular Y-jet nozzle. When SMD was measured in the X_Axis direction at the same gas mass flow rate, the elliptical Y-jet nozzle with an aspect ratio of 2:1 showed greater asymmetry than the others.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.5
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• pp.1-12
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• 2020

In this paper, the heat transfer characteristics of Jet A-1, which is used as a coolant and fuel in a regeneratively cooled thrust chamber, were experimentally studied. By varying the applied current for heating the cooling channel, the simulated specimen diameter, the specimen outlet pressure and the coolant flow rate, the wall temperatures of the specimen and the Jet A-1 temperatures at the specimen inlet/outlet were measured. It was found that the specimen diameter and the flow rate were important factors for the characteristics of heat transfer and the outlet pressure did not affect the performance of heat transfer. The results of the heat transfer experiments were compared with the previous Nusselt number empirical equations and novel Nusselt number empirical equations were finally derived.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.221-224
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• 2002

A technique of mixing enhancement in an underexpanded sonic round jet is studied with fully expanded jet Mach number 1.5. Tonal sound, jet screech can be produced at some underexpansion pressure ratio in a sonic jet. Since the jet screech excites the initial Jet shear layer to change the flow, a reflector which focuses the jet screech near the nozzle lip is designed. The reflector has an elliptic shape of which two foci are located near the nozzle lip and the jet screech source region. Jet screech tone near the nozzle lip increases with the elliptic reflector and spreading of the jet largely increases. It is concluded that mixing enhancement of the jet with the elliptic reflector is attributed to large scale structures which are initially excited by the increased jet screech.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.1
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• pp.1-11
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• 2022

In a gas turbine, fuel is exposed to a high temperature environment until it is fed to the combustor through the injector. Hydrocarbon fuels can coke under high temperature conditions, which can cause coking material to deposit on fuel lines or block the injector passages. In this study, a specimen simulating a fuel line located inside a gas turbine and Jet A-1 were heated using electric devices. Jet A-1 coking tests were performed by changing the wall temperature of the stainless steel specimen and the temperature of Jet A-1 supplied to the specimen. After the coked specimens were cut, the coking material and the inner surface were analyzed using an energy dispersive X-ray spectrometer and a field emission scanning electron microscope.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.44.1-44.1
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• 2020

Hα jets of cool chromospheric plasma are protruding into the solar corona 10-100 Mm above the photosphere. The driving mechanisms of Hα jets have been widely studied for decades. However, the detailed process is still elusive. We observed shock signatures moving along a dark jet using 1.6 meter Goode Solar Telescope at Big Bear Solar Observatory. The first shock front of the jet shows sharp --- when it moves upward, while fuzzy and granulated when it moves downward. The jet itself extends upward when the second shock front of the jet reaches the top of the jet. We find abrupt EUV brightenings when the second shock front collides with the edge of the jet. The third front and the fouth front quasi-periodically. These phenomena might be the signs of the rebound shock waves triggered by p-mode wave leakages at the bottom of the jets. Our observation suggests that the jet can be triggered by the rebound shock waves generated by the p-mode waves leaked at the bottom of the jets.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.702-704
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• 2011

For the representative of the poor performance of liquid fuel(Jet A-1), the physical properties effests of different additive ratios in the liquid fuel have been investigated. The mixed liquid fuel could be analyzed by principal factor of liquid fuel such as, density, viscosity and caloric value. This additives will be usefully applied to high energy density liquid fuel development.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.3
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• pp.393-404
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• 2017

Side jet effect on the aerodynamic characteristics of a missile was investigated using experimental and computational methods. A couple of side jets were injected toward outward downstream at mid point of missile body. Cold air jet was used in the wind tunnel test, and cold and hot jet were used in the computation. Wind tunnel test was carried out with jet and without jet, and calculation was performed for three cases ; no jet, cold air jet, and hot mixture gas jet. From the comparison of measured and calculated data for all cases, two points could be deduced. Firstly, side jet made static stability to be unstable by increasing body normal force near the side jet exit and by decreasing tail normal force. Secondly, hot mixture gas had more significant effect on the static stability of a missile-type body than cold air jet.

• Fire Science and Engineering
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• v.33 no.5
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• pp.13-18
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• 2019

In this study, the soot formation characteristics of Jet-A1 liquid fuel droplet flames were investigated by measuring the soot concentration under atmospheric conditions similar to the working environment of the Korea Space Launch Vehicle (KSLV) To obtain the desired atmospheric conditions, the oxygen concentration in the combustion chamber was maintained at 30% and the pressure was varied between 0.1 and 0.06 MPa. The full-field light extinction technique was used to measure the concentration of soot particles generated by applying the identical to 2-mm-diameter Jet-A1 fuel droplets. The soot concentration of the Jet-A1 droplet flames was the highest in the nitrogen-substituted atmosphere and the lowest in the carbon dioxide-substituted atmosphere, despite the pressure. the pressure was decreased the measured soot concentrations reduced as a function of Pⁿ.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1230-1239
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• 2018

We derive a factorization theorem for the jet mass distribution with a given $p^J_T$ for the inclusive production, where $p^J_T$ is a large jet transverse momentum. Considering the small jet radius limit ($R{\ll}1$), we factorize the scattering cross section into a partonic cross section, the fragmentation function to a jet, and the jet mass distribution function. The decoupled jet mass distributions for quark and gluon jets are well-normalized and scale invariant, and they can be extracted from the ratio of two scattering cross sections such as $d{\sigma}/(dp^J_TdM^2_J)$ and $d{\sigma}/dp^J_T $. When $M_J{\sim}p^J_TR$, the perturbative series expansion for the jet mass distributions works well. As the jet mass becomes small, large logarithms of $M_J/(p^J_TR)$ appear, and they can be systematically resummed through a more refined factorization theorem for the jet mass distribution.