• Journal of ILASS-Korea
• /
• v.2 no.4
• /
• pp.7-14
• /
• 1997

Laser Raman scattering method has been applied to measure equivalence ratio of methane/air mixture in injected spray. We used high power KrF excimer laser$(\lambda=248nm)$ and a high gain ICCD camera to capture low intensity signal. Raman shifts and Raman scattering cross -sections of $H_2,\;O_2,\;N_2,\;CO_2,\;CH_4\;and\;C_3H_8$ are measured precisely. Our results show an excellent agreement with those of other groups. Mole fraction measurement of $O_2\;and\;N_2$ from air shows that $O_2:N_2=0.206:0.794$. We used gas injector which was operated at 1 bar. Methane is used as a fuel. Spray region is $10mm\times37mm$ and this region is divided into 80 points. In Raman signals are obtained and ensemble averaged for each point. 3-d and contour plot of distribution of equuivalence ratio is presented. Our measured results show that the equivalence ratio of methane/air mixture in methane-rich region is reasonable. However, more study is necessary for methane-lean region because background noise level is almost same as Raman intensity of methane.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.2 no.5
• /
• pp.11-22
• /
• 1994

The pupose of this study is to measure droplet size and velocity simultaneously for a transient diesel fuel spray in a quiescent chamber at atmospheric temperature and pressure. Generally, diesel combustion phenomena is mainly governed by characteristics of injection system and fuel spray. Therefore we need to clarify these characteristics for developing more economical diesel systems. In this study, correlation between droplet size and velocity was measured at downstream distance from nozzle. Governing parameters are pump speed and fuel quantity for the detailed nature in this transient diesel fuel spray. It is observed effect to the droplet size and velocity distribution. Velocity(peak, mean, rms), number density and droplet size were investigated simulaneously using PDA in the spray. Various results are presented to illustrate the effects of operation factors and correlation between the droplet diameter and velocity.

• Journal of the Korean Society of Visualization
• /
• v.3 no.2
• /
• pp.3-13
• /
• 2005

The optical patterantor provides the high resolution and quantitative information of the spray. Fuel distribution and Sauter Mean Diameter (SMD) can be measured from fluorescence and Mie-scat-tering images. To correct the attenuation of the laser beam and signal in dense spray region, the method to find the geometric mean of the signal intensities obtained from two cameras was evaluated and verified in a solid-cone spray. In high pressure environment, the increased number density of the droplets cause multiple scattering. The optical patternation technique using a laser beam instead of a laser sheet was applied to minimize the multiple scattering problem. The pattern of a coaxial spray was changed from hollow-cone to solid-cone shape, and the spray angle was reduced as the ambient pressure increased from 0.1 to 4.0 MPa.

• Journal of ILASS-Korea
• /
• v.21 no.2
• /
• pp.88-94
• /
• 2016

In this study digital holographic microscopy system for measurements of 3-D velocities of particles in MR fluid is developed. Holograms are recorded using either a CCD camera with a double pulse laser or a high-speed camera with a continuous laser. To process recorded holograms, the correlation coefficient method is used for focal plane determination of particles. To remove noise and improve the quality of holograms and reconstructed images, a Wiener filter is adopted. The two-threshold and image segmentation methods are used for binary image transformation. For particle pairing, the match probability method is adopted. The developed system will be applied to measurements of the characteristics of unsteady 3-D particle velocities in MR fluids through the next stage of this study.

• Journal of ILASS-Korea
• /
• v.5 no.1
• /
• pp.23-29
• /
• 2000

Recently the laser sheet technique has been developed to improve our limited understanding of the in-cylinder diesel combustion. The technique is capable of high temporal and spatial resolution, so that it is proved to be an adequate combustion diagnostics to find out exhaust emission formation. The optical signals of LIS(Laser Induced Scattering) and LII(Laser Induced Incandescence) images show informations for soot concentration within the optically accessible diesel engine. The LIS and LII signal images of soot concentration provide new insight into where and when soot occurs in a diesel engine.

• Journal of ILASS-Korea
• /
• v.7 no.3
• /
• pp.31-37
• /
• 2002

In previous study, diesel-methanol stratified injection system is manufactured and applied to a D.I. diesel engine in order to realize combustion improvement using methanol, which is oxygenated fuel with large latent heat. We know that NOx and soot is reduced by stratified injection of diesel fuel-methanol. Therefore, in the present study, combustion diagnosis using optical measurement is tried to make clear effect of methanol on simultaneous reduction of NOx and soot. Two-color method is used to measure flame temperature and KL value, which is approximately proportional to the soot consentration along the optical path. Laser induced scattering method was used to measure distribution of soot at two dimensional area. Also, it is compared exhaust characteristics of NOx and soot with results of optical measurement.

• Journal of ILASS-Korea
• /
• v.9 no.4
• /
• pp.67-76
• /
• 2004

Diode laser absorption sensors are advantageous because they may provide fast, sensitive, absolute, and selective measurements of species concentration. These systems are very attractive for practical applications owing to its compactness, reasonable cost, robustness, and ease of use. In addition, diode lasers we fiber-optic compatible and thus enable simultaneous measurements of multiple species along a line-of-sight. Recent advances of room-temperature, near-IR and visible diode laser sources for telecommunication, optical data storage applications make it possible to be applied for combustion diagnostics based on diode laser absorption spectroscopy. Therefore, combined with fiber-optics and high sensitive detection strategies, compact and portable sensor systems are now appearing for variety of applications. The objectives of this research are to develop new gas sensing system and to verify feasibility of this system. Wavelength modulation spectroscopy has been demonstrated in these experiments and has a bright prospect to this diode laser system.

• 한국가시화정보학회:학술대회논문집
• /
• 2006.12a
• /
• pp.63-67
• /
• 2006

Spray characteristics of an injector employed in mono-propellant hydrazine thrusters were investigated by PIV(particle image velocimetry) and PDA(phase Doppler anemometry) techniques. The instantaneous plane images captured by PIV measurement were examined in order to judge the pass-fail criteria of spray injection performance according to the specific pressure supplied. PDA technique was also applied to measure the velocity and droplet size of spray which were not obtainable by PIV measurement. The objective of this experimental study is the evaluation of the injector performance which may be utilized for the design of brand-new injector through the clear understanding of spray characteristics.

• Journal of the Korean Society of Safety
• /
• v.11 no.4
• /
• pp.24-28
• /
• 1996

The speckle photography technique is one of the novelest velocity measurement methods. This study examines the possibility that this technique will become practically applicable. In this study, LSP is applied to the fine water mist spray. Moreover, a He-Ne gas laser is employed as the light source in order to enhance the validity of this technique. It becomes clear that this technique using a He-Ne gas laser can obtain a whole instantaneous two-dimensional velocity distribution and also apply to test the performance of fine water spray.

• Journal of the Korean Society of Visualization
• /
• v.8 no.4
• /
• pp.60-65
• /
• 2010

A focus is given to the breakup behavior of spray droplets issuing from a nonimpinging-type injector. The analysis has been carried out experimentally by means of the dual-mode phase Doppler anemometry (DPDA). Spray characteristic parameters in terms of axial velocity, mean diameter, velocity fluctuation, and span (width of the size distribution) of droplets are measured down the geometric axis of a nozzle orifice and on the plane normal to the spray stream with the injection pressure variations. As the injection pressure increases, the velocity and its fluctuation become higher, whereas the droplet sizes get smaller. It is also shown that the magnitudes of those parameters are smoothed out by dispersion when the droplets move downstream as well as outwardly. The atomization process is significantly influenced by the injection pressure rather than the traveling distance in the experimental condition presented.