• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.285-289
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• 2017

Laser-induced breakdown spesctroscopy (LIBS) is a technique that complements the disadvantages of conventional laser-based combustion diagnosis techniques such as weak signal strength, complex equipment configuration, and low accuracy. In this study, basic research was carried out to measure the combustion gas temperature of scramjet engines using LIBS. Spray flames were generated from Jet A-1 fuel used in scramjet engines and gas temperatures were measured at the top of the flames with a calibrated thermocouple. The LIBS signals were acquired at the same points as the temperature measurement positions of the thermocouple. The LIBS spectra were analyzed to obtained a calibration curve between the LIBS signal and the reference temperature measured at the thermocouple. Therefore, it was confirmed that the combustion gas temperature can be measured in-situ using LIBS.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.802-806
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• 2004

For the protection of the local air quality and the global atmosphere, the emissions of trace species including nitric oxides (NO and NO$_2$) from gas turbines are regulated by local governments and by the International Civil Aviation Organization. In-situ measurements of such species are needed not only for the development of advanced low-emission combustion concepts but also for providing emissions data required for the sound assessment of the effects of the emissions on environment. We have been developing a laser absorption system that has a capability of simultaneous determination of NO and NO$_2$concentrations in the exhaust jets from aero gas turbines. A diode laser operating near 1.8 micrometer is used for the detection of NO while a separated visible tunable diode laser operating near 676 nanometers is used for NO$_2$. The sensitivities at elevated temperature conditions were determined for simulated gas mixtures heated up to 500K in a heated cell of a straight 0.5 m optical path. Sensitivity limits estimated as were 30 ppmv-m and 3.7 ppmv-m for NO and NO$_2$, respectively, at a typical exhaust gas temperature of 800K. Experiments using the simulated exhaust flows have proven that $CO_2$ and $H_2O$ vapor - both major combustion products - do not show any interference in the NO or NO$_2$ measurements. The measurement system has been applied to the NO/NO$_2$ measurements in NO and NO$_2$ doped real combustion gas jets issuing from a rectangular nozzle having 0.4 m optical path. The lower detection limits of the system were considerably decreased by using a multipass optical cell. A pair of off-axis parabola mirrors successfully suppressed the beam steering in the combustion gas jets by centralizing the fluctuating beam in sensor area of the detectors.

• Current Industrial and Technological Trends in Aerospace
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• v.8 no.2
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• pp.24-30
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• 2010

Space solar sails are a form of spacecraft propulsion using the radiation pressure of light from a star or laser to push enormous ultra-thin mirrors to high speeds. With respect to it, U.S.A, Japan, E.U. and Russia, etc. have performed a substantial research and the space flight test. On May 2010, JAXA succeeded in launching the world's first interplanetary solar sail spacecraft "IKAROS" to Venus. Currently, solar sail propulsion is aimed chiefly at accomplishing a number of non-crewed missions in any part of the solar system and beyond. This paper presents the technology trend of advanced countries on the development of the solar sails as a new propulsion method for the space investigation and travel.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.12
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• pp.923-929
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• 2003

As for the marine propulsion shafting system using 4 stroke diesel engine, it is common to apply a reduction gear box between diesel engine and shafting to increase propulsion efficiency, which requires inevitably a certain elastic coupling to avoid chattering and hammering inside of gear box. In this study, the optimum method of rectifying propulsion shafting system in case of 750 ton fishing vessel is theoretically studied in a view of dynamic characteristics of torsion. After the replacement of diesel engine and gear box, the torsional vibration get worse and so some countermeasures are needed. The elastic coupling is modified from a present rubber coupling of block type having relatively high torsional stiffness to a rubber coupling haying two serially connected elements. Torsional vibration damper was installed at crankshaft free end additionally and moment of inertia of flywheel was adjusted. The dynamic characteristics of shafting system was improved by these modification. The theoretical analysis of torsional vibration are compared to measurement results using two laser torsion meters during the sea trial.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.205-210
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• 2004

The pulse detonation engine (PDE) has recently expected as a new aerospace propulsion system. The PDE system has high thermal efficiency because of its constant-volume combustion and its simple tube structure. We measured thrust of single-tube pulse detonation rocket (PDR) by two methods using the PDR-Engineering Model (full scale model) for ground testing. The first involved measuring the displacement of the PDR-EM by laser displacement meter, and the second involved measuring the time-averaged thrust by combining a load cell and a spring-damper system. From these two measurements, we obtained 130.1 N of time-averaged thrust, which corresponds to 321.2 sec of effective specific impulse (ISP). As well, we measured the heat flux in the wall of PDE tubes. The heat flux was approximately 400 ㎾/$m^2$. We constructed the PDR-Flight Mode] (PDR-FM). In the vertical flight test in a laboratory, the PDR-FM was flying and keeping its altitude almost constant during 0.3 sec.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.5
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• pp.10-19
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• 2012

To eliminate the onset of combustion instabilities and develop effective approaches for control, flame structure is very important. In this study, we conducted experiments under various operating conditions with a model gas turbine combustor to examine the relation of combustion instability and flame structure by OH chemiluminescence and laser diagnostics of He-Ne laser absorbtion system. The swirling LNG($CH_4$)/air flame was investigated with overall equivalence ratio of 1.2 and dump plane fuel-air mixture velocity 25 ~ 70 m/s. We founded that the combustion instability phenomenon occurs at lower mixing velocity and higher mixing velocity conditions. We also concluded that fluid dynamical vortex frequency has major effects on the combustion instability characteristics at lower mixing velocity condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.381-384
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• 2011

Wave drag reduction due to the repetitive laser induced energy deposition over a flat-nosed cylinder is experimentally conducted in this study. Irradiated laser pulses are focused by a convex lens installed in side of the in-draft wind tunnel of Mach 1.94. The maximum frequency of the energy deposition is limited up to 80. Time-averaged drag force is measured using a low friction piston which was backed by a load cell in a cavity as a controlled pressure. Stagnation pressure history, which is measured at the nose of the model, is synchronized with corresponding sequential schlieren images. With cylinder model, amount of drag reduction is linearly increased with input laser power. The power gain only depends upon the pulse energy. A drag reduction about 21% which corresponds to power gain of energy deposition of approximately 10 was obtained.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.367-376
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• 2012

To eliminate the onset of combustion instabilities and develop effective approaches for control, flame structure is very important. In this study, we conducted experiments under various operating conditions with a model gas turbine combustor to examine the relation of combustion instability and flame structure by OH chemiluminescence and laser diagnostics of He-Ne laser absorbtion system. The swirling LNG(CH4)/air flame was investigated with overall equivalence ratio of 1.2 and dump plane fuel-air mixture velocity 25 ~ 70 m/s. We founded that the combustion instability phenomenon occurs at lower mixing velocity and higher mixing velocity conditions. We also concluded that fluid dynamical vortex frequency has major effects on the combustion instability characteristics at lower mixing velocity condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.285-288
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• 2009

In order to understand spray characteristics with inflowing air from the compressor in the APU gas turbine combustor, we performed spray visualization test by using ND-Yag Laser sheet beam. The sector combustor which size is 1/6 of the real combustor was manufactured. Turbo blower is used as an air supplying device to simulate gas turbine air flow condition. In the case of 75 m/s combustor inlet air flow condition, spray angle way increased and dispersed widely than without airflow condition.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.55-65
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• 2005

Mixing performance between fuel and oxidizer is a significant parameter of combustion efficiency and stability in an air-turbo ramjet combustor. Two types of petal mixer were experimented to research the mixing performance. Mixing performance and fuel distribution images were obtained for petal mixers. Planar laser-induced fluorescence(PLIF) was used to obtain 2-D fuel distribution. The obtained images were processed in order to make use of the image information to a quantitative level. The results of analyzing the fluorescence images could be useful to find better mixing performance between mixers.