• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.4
• /
• pp.77-84
• /
• 2001

Measurements of local CO, $CO_2$, $O_2$, $N_2$, $C_3$H$_{8}$, NOx concentrations and flame temperature are made for partially premixed flame with and without acoustic excitation. The CO, $CO_2$, $O_2$, $N_2$, and $C$_3$H_8$ concentrations are determined by thermal conductivity detection (Gas-chromatograph) and NOx concentrations are determined by chemiluminescent detection (NOx analyser). To measure local sample concentration, sampling probe was made by quartz with inlet diameter of 0.25mm. In the case of excitation, the visual shape of the flame is changed from laminar flame to turbulent-like flame. The flame length is also reduced, and the flame width becomes broad. In the observation of emission concentration without acoustic excitation, meanwhile, the $CO_2$ and NOx concentrations peak at flame front where the mixture meets with surrounding air, and the CO concentration is increasing at maximum position of CO2 concentration and peaks at the centerline of the burner. In the case of acoustic excitation, the $CO_2$ concentration is widely occurred at nozzle of the burner and is higher relative to unexcitation. The CO concentration is much reduced, but NOx concentration is more increasing. And flame temperature is higher relative to unexcitation. These are caused by enhancing of mixing with surrounding air due to excitation. However, in the case of acoustic excitation, the total NOx concentration is reduced because of the shortened flame length which affects residence time.e.

• Journal of Korean Ophthalmic Optics Society
• /
• v.7 no.1
• /
• pp.1-8
• /
• 2002

Various kinds of aerosols such as a mixture of hairspray resin and its solvents, a perfume, a soap water, and ask in-lotion were sprayed onto the contact lens which was mounted on the eye-model made of wood, varying the parameters as the distance between nozzle and contact lens and the spraying time duration. In the case of both the hairspray and the perfume including an ethanol as solvents, the shape of contact lenses has changed tremendously Jess than 1 minute after the exposure to the aerosol particles and then it continued until the lens surfaces were completely flipped over. Driving force for the lens distortion seems to be the expansion coefficient difference between the inner and outer surface of lens, which was caused by the heat of vaporization of ethanol included in the aerosol and subsequent temperature decrease induced on the lens surface.

• Journal of ILASS-Korea
• /
• v.25 no.1
• /
• pp.8-14
• /
• 2020

Recently, 1-D model-based engine development using virtual engine system is getting more attention than experimental-based engine development due to the advantages in time and cost. Injection rate profile is the one of the main parameters that determine the start and end of combustion. Therefore, it is essential to set up a sophisticated model to accurately predict the injection rate as starting point of virtual engine system. In this research, procedure of 1-D model setup based on AMESim is introduced to predict the dynamic behavior and injection rate of diesel injector. As a first step, detailed 3D cross-sectional drawing of the injector was achieved, which can be done with help of precision measurement system. Then an approximate AMESim model was provided based on the 3D drawing, which is composed of three part such as solenoid part, control chamber part and needle and nozzle orifice part. However, validation results in terms of total injection quantity showed some errors over the acceptable level. Therefore, experimental work including needle movement visualization, solenoid part analysis and flow characteristics of injector part was performed together to provide more accuracy of 1-D model. Finally, 1-D model with the accuracy of less than 10% of error compared with experimental result in terms of injection quantity and injection rate shape under normal temperature and single injection condition was established. Further work considering fuel temperature and multiple injection will be performed.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.23 no.5
• /
• pp.19-26
• /
• 2019

Paraffin fuels usually have low combustion efficiency due to discharged unburnt droplets from the nozzle. Therefore, optimization of the post-chamber is becoming an important factor for performance. In this study, combustion experiments were conducted by changing either the length or diameter of the post-chamber to reveal the combustion behavior of paraffin fuel for hybrid rocket. As a result, the combustion efficiency improved due to the increase of the residence time as the post-chamber length increased. On the other hand, it is found that the influence of the diameter change was not significant compared with the case of variable post-chamber length.

• Textile Coloration and Finishing
• /
• v.34 no.3
• /
• pp.185-196
• /
• 2022

In this study, carbon fiber and coated glass fiber are applied to warp and weft fiber in order to reduce the amount of carbon fiber used in carbon fiber fabrics, which are often used for reinforcement of building structures. A low-cost thermoplastic resin was coated on glass fibers to prepare a shape-stabilizing glass fiber. A unidirectional carbon fiber sheet was manufactured using the prepared coated glass fiber and carbon fiber. In order to identify whether it can be used for reinforcing architectural and civil structures, it was attached to a concrete specimen and its mechanical properties were analyzed. The optimum manufacturing conditions for the coated glass fiber were 0.3 mm in diameter of the coating nozzle, the coating temperature was 190 ℃, and the coating speed was 0.3 m/s. 14 mm was optimal for the weft spacing of the coated glass fiber. The flexural strength of the concrete reinforced with the manufactured unidirectional carbon fiber sheet was slightly lower than that of the concrete reinforced with carbon fiber fabric, but it was confirmed that the reinforcement effect was better when the amount of carbon fiber was considered.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.9 no.6
• /
• pp.732-742
• /
• 1985

Measurements of mean velocity and turbulence characteristics are obtained with a linearized constant temperature hot-wire anemometer in a two-dimensional turbulent jet discharging parallel to a flate. Wall static pressure distribution is also measure. The Reynolds number based on the jet nozzle width (D) is about 42,000 and the step height is 2.5D. The reattachment length is found to be 7.5D by using both wool tuft and oil methods. Upstream of the reattachment point, there exist double coherent structures and mean velocity, Reynolds stresses and triple product profiles are asymmetric about jet center line due to the influence of streamline curvature and recirculating flow region. Near the reattachment point, wall static pressure and turbulence quantities change its shape rapidly because of the large eddies by the solid wall. Especially, turbulence intensity has a maximum value in the reattachment regin, then decreases slowly in the redeveloping wall jet ragion. Downstream of X/D=14, a single large scale eddy structure is formed. Far downstream affer the reattachment(X/D.geq.18) mean velocity profile, the decay of maximum velocity and the variation of jet half width are nearly similar to those of plane wall jet, but the Reynolds stresses are higher than those of the latter.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.789-794
• /
• 2000

The Paper studies the flow and heat transfer characteristics to a jet impinging at different oblique angles, to a plane surface by numerical methods. The flowfield and heat transfer rate associated with the oblique Impingement of an axisymmetric jet are of interest as a result of its presence in numerous technological Problems. For the computation of heat transfer rate, the standard ${\kappa}-{\varepsilon}$ and ${\kappa}-{\varepsilon}-\bar {{\upsilon}'^ 2}$ turbulent model were adapted. The accuracy of the numerical calculations was compared with various experimental data reported in the literature. ${\kappa}-{\varepsilon}-\bar {{\upsilon}'^ 2}$ model showed better agreement with experimental data than standard ${\kappa}-{\varepsilon}$ model in prediction of the turbulent intensity and the heat transfer rate. In the case of computation of flowfield, the study carries on the ${\alpha}=45$ deg, h/D=4.95. The jet Reynolds number based on the nozzle diameter(D), was 48,000. For the computation of heat transfer rate, the Re=20,000, the jet orifice-to-plate spacings(L/D) are 4, 6 and 10, and the angle between the axis of the jet orifice and the plate surface is set at 30, 45, 60, or 90 deg. For the smaller spacings, the near-peak Nusselt numbers are not significantly effected by the initial decreases in the Jet angle. The overall shape of the local Nusselt number x-axis profile is influenced by both the jet orifice-to-plate spacing and the jet angle.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.2
• /
• pp.31-37
• /
• 2017

This paper investigates the effect of the rotational motion of a driving fluid generated by a rotational motion device at the inlet of a driving nozzle for a gas-liquid ejector, which is the main device used for ozonated ship ballast water treatment. An experimental apparatus was constructed to study the pressure and suction flow rate of each port of the ejector according to the back pressure. Experimental data were acquired for the ejector without rotational motion. Based on the data, a finite element model was then developed. The rotational motion of the driving fluid could improve the suction efficiency of the ejector based on the CFD model. Based on the CFD results, structure optimization was performed for the internal shape of the rotation induction device to increase the suction flow rate of the ejector, which was performed using the kriging technique and a metamodel. The optimized rotation induction device improved the ejector efficiency by about 3% compared to an ejector without rotational motion of the driving fluid.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.2
• /
• pp.1-10
• /
• 2022

Exhaust gases emitted from internal combustion engines contain nitrogen oxides (NOx) and sulfur oxides (SOx), which are major air pollutants causing acid rain, respiratory diseases, and photochemical smog. As a countermeasure, scrubber systems are being studied extensively. In this study, the pressure drop characteristics were analyzed by changing the exhaust gas inflow velocity using a scrubber for a 700 kW engine as a model. In addition, the fluid flow inside the scrubber and the behavioral characteristics of the droplets were studied using CFD, and the design compatibility of the cleaning device was verified. Flow analysis was performed using inertial and viscous resistances by applying porous media to the complex shape of the scrubber. The speed of the exhaust passing through the outlet nozzle from the inlet was determined through the droplet behavior analysis by spraying, and the flow characteristics for the pressure drop were studied. In addition, it was confirmed through computational analysis whether there was a stagnation section in the exhaust gas flow in the scrubber or the sprayed droplets were in good contact with the exhaust gas.

• Journal of the Korean Ceramic Society
• /
• v.46 no.6
• /
• pp.574-582
• /
• 2009

$UO_2$ microsphere particles, core material of HTGR(High Temperature Gas Reactor) nuclear fuel, were prepared using by the GSP(Gel Supported Precipitation) method which is a modified-method of the wet sol-gel process. The spherical shape of initial liquid ADU droplets from the vibration nozzle system was continuously kept till the conversion to the final $UO_2$ microsphere. But the size of a final $UO_2$ microsphere was shrunken to about 25% of an initial ADU droplet size. Also, we found that the composition of dried-ADU gel particles was constituted of the very complicated phases, coexisted the U=O, C-H, N-H, N-O, and O-H functional groups by FT-IR. The important factors for obtain the no-crack $UO_2$ microsphere during the thermal treatment processes must perfectly wash out the remained-$NH_4NO_3$ within the ADU gel particle in washing process and the selections of an appropriate heating rate at a suitable gas atmosphere, during the calcining of ADU gel particles, the reducing of $UO_3$ particles, and the sintering of $UO_2$ particles, respectively.