• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.277-283
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• 1995

For the development of low NO$_{x}$ gas burners aimed for absorption chiller/heater unit, three proto type burners of different capacity (265000, 498000, and 664000 kcal/h) have been manufactured through a combustion method of step-by-step air injection. In order to characterize the overall features of the flame and the properties of the emission gas, the temperature of the flame and the concentration of NO$_{x}$ and CO were determined. The main factors in the design of burners (the area of primary air injection, the diameter of secondary air injection hole, fuel nozzle diameter) were observed to increase linearly with the scale-up of burner capacity. The flame temperature profiles of the burners were observed to be almost similar, irrespective of their capacity. However, as their capacity increased, the flame temperature slightly increased and the hot region of the flames moved to ward the flame tip along with the expansion to the direction of radius. From the proto type units, the amount of their NO$_{x}$ emission was determined to be around 25 - 30 vppm(3% )$_{2}$) and the CO emission was less than 19 vppm (3% $O_{2}$).TEX>).

• Journal of Power System Engineering
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• v.3 no.3
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• pp.22-28
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• 1999

The injected liquid does not break-up instantly after injection for diesel engine. There is some unbroken portion, which is the liquid core(The length of liquid core is called the break-up length) in the spray. If the liquid core is longer than the depth of the bowl in the small DI diesel engine, the liquid core impinges on the surface of the piston. Once the liquid core impinges on the surface, it cannot ignite or burn rapidly and thus prolongs burning time with a degradation in thermal efficiency. The break-up length of a diesel spray in a compressure vessel was measured by an electric resistance method, A voltage was applied between the nozzle and screen, bar, needle electrode inserted at various axial and radial positions into atomizing sprays. As a result, a current flows not only in the region of liquid core but also through the droplets of the spray. It is found that the break-up length measured with screen electrode is overestimated. The break-up length of the spray is found to be proportional to the square root of the density ratio of fuel and surrounding gas. The break-up length of the spray decreases as the injection pressure and the back pressure increase.

• 연구논문집
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• s.24
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• pp.41-48
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• 1994

This experimental study deals with the extinguishiment characteristics of an oil pool flame using the water spray. The water through the six different atomizers is ejected over the freely burning pool flame in the quiescent surrounding air. Injection direction is vertical to the surface of oil in a small tank with a diameter of 100mm and a height of 10mm. In order to estimate quantitatively the extinction, the burning rate as well as the effective water flux are measured. The effective water flux is the amount of the water which reach the pool from the nozzle. The burning rate with the water spray increases until the injection pressure increases to reach some value, which gives the maximum burning rate, while the effective water flux without the flame decreases or does not change according to increasing of the injection pressure. This maximum burning rate is greater than 2.5 times of burning rate of the fire without the water spray. As a matter of the extinguishiment, it is found that the water drops of which size is too small can not extinguish the fire because too small drops does not reach the fuel surface.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.89-94
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• 2008

Differential pressure flow meters which have a shape of triangular separate bar(TSB) were tested for investigating the flow rate characteristics of the flow meters with varying the temperature of the gas flow. Three kinds of the triangular separate bar flow meters whose aerodynamic angles are different one another are used. The mass flow rate of the flow meters are evaluated using a non-dimensional parameter which includes the gas temperature, exhaust gas pressure and differential pressure at the flow meters, and atmospheric pressure. A burner system which is similar to gas turbine was used for raising the gas flow temperature. The burner system was operated with varying the air/fuel ratio by controlling both the fuel injection rate from the fuel nozzle and air flow rate from a blower. An empirical correlation between the mass flow rate at the TSB flow meter and the non-dimensional parameter was obtained. The empirical correlation showed linear relationship between the mass flow rate and the non-dimensional parameter H. Also, the mass flow rate characteristics at the TSB flow meter was affected by the gas temperature.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.1
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• pp.38-43
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• 2004

The study was performed to understand combustion characteristics of the slinger combustor. Liquid fuel is discharged radially outwards through injection holes drilled in the high speed rotating shaft. The spray test was peformed to verify atomizing characteristics with variation of fuel nozzle rotational speed by using PDPA system. SMD was measured at different RPM and values are 70$\mu\textrm{m}$ at 5,000RPM rpm, 60$\mu\textrm{m}$ at 10,000RPM and 40$\mu\textrm{m}$ at 20,000RPM. In the results, we found out that SMD is grown smaller with increasing rotational speed. In KARI combustion test facility, Ignition and combustion tests were performed by using combustor test rig. In the test results, ignition and combustion efficiency were improved according to increasing rotational speed. The measured radial temperature distribution at the combustor exit shows stable and fairly good distribution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.107-114
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• 2017

A turbocharger is an engine supercharger that is driven by exhaust gas. It improves the output and fuel efficiency by increasing the charging efficiency of the mixture gas, which is achieved by changing the rotatory power of the turbine connected to the exhaust passage. It is important to control the supercharging for this purpose. A nozzle slide joint is one of the core parts. Austenitic stainless steel is currently used as the material for this part, and its excellent mechanical properties include high heat resistance and corrosion resistance. However, because of its poor machinability, there are many difficulties in producing products with complicated shapes. Machining is used in the production of nozzle slide joints for high dimensional accuracy after metal powder injection molding. As design variables in this study, we investigated the sintering temperature, product stress, deformation rate, radius of curvature of the punch, and angle of the chamfer punch, which are related to the strain and shapes. The goal is to suggest a forming process using Nitronic 60 that does not require machining to manufacture a nozzle slide joint for a turbocharger. Accordingly, we determined the best process environment using finite-element analysis, the signal-noise ratio, and the Taguchi method for experiment design. The relative density and hydrostatic pressure of the final product were in accordance with the results of the finite element analysis. Therefore, we conclude that the Taguchi method can be applied to the design process of metal powder injection molding.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.5
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• pp.9-17
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• 2008

Pseudo-3D spatial distribution of spray droplets is investigated by using Dual-mode Phase Doppler Anemometry (DPDA) in order to examine the disintegration and spreading behavior of spray exiting from liquid-propellant thruster injector. Spray injected from nozzle orifice with length-to-diameter ratio ($L/d_o$) of 1.67 and under the injection pressure of 27.6 bar is aligned to the vertical. Vertical and horizontal mean velocities of droplets, Sauter Mean Diameter (SMD), and volumetric flux decrease as droplets travel from center/upstream toward outer region/downstream of spray. Although the distribution of spray characteristic parameters is symmetric against the geometric axis of nozzle orifice, their absolute values are asymmetric.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.9
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• pp.577-587
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• 2016

Although the formation of oxy-fuel MILD combustion is considered one of the promising combustion technologies for high thermal efficiency, low emissions and stability have been reported as difficulties. In this paper, the effect of combustor geometry and operating conditions on the formation of oxy-fuel MILD combustion was analyzed using numerical simulation. The results show that the high temperature region and average temperature decreased due to an increase in oxygen inlet velocity; moreover, a high degree of temperature uniformity was achieved using an optimized combination of fuels and an oxygen injection configuration without external oxygen preheating. In particular, the oxy-fuel MILD combustion flame was found to be very stable with a combustion flame region at equivalence ratio 0.90, fuel velocity 10 m/s, oxygen velocity 200 m/s, and nozzle distance 33.5 mm.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.4
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• pp.174-179
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• 2004

Domestic marine diesel engine makers reduce the NOx emission mostly by applying low NOx fuel nozzle and injection timing retard. However, it is necessary to develop high efficient technology (EGR, DWI and SCR, etc.) to reduce NOx emission in order to prepare for the further reinforcement of the NOx emission limit. Also, in the near future, IMO will restrict additively THC, PM and CO with NOx. Therefore, domestic engine makers have to prepare for it and the relevant government ministries should give a sufficient support to these technology research and establish or amend the relevant law, which should include the excursion riverboat.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.491-498
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• 2010

Humidification of PEM fuel cells is necessary for enhancing their performance and lifetime. In this study, a humidification system was designed and tested; the system includes an air-supply tube (inner diameter: 75 mm) through which a nozzle can be directly inserted and a cyclonic separator for the removal of water droplets. Three types of nozzles were employed to study the influence of injection pressure, air flow rate, and spray direction on the humidification performance. To evaluate the humidification performance, the concept of humidification efficiency was defined. In the absence of an external heat source, latent heat for evaporation will be supplied by the own enthalpies of water and air. Thus, the amount of water sprayed from the nozzle is the most critical factor affecting the humidification efficiency. Water droplets were efficiently removed by a cyclonic separator, but re-entrainment occurred at high air flow rates. The absolute humidity and humidification efficiency were $21.29\;kJ/kg_{da}$ and 86.57%, respectively, under the following conditions: nozzle type PJ24; spray direction angle $90^{\circ}$; injection pressure 1200 kPa; air flow rate 6000 Nlpm.