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장병화(Byunghwa Jang),성연모(Yonmo Sung),오창용(Changyong Oh),김승태(Seungtae Kim),전유택(Yootaek Jeon) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
Oscillating combustion characteristics was experimentally investigated to reduce NOx emissions and improve thermal efficiency in a 1MWth industrial burner for reheating furnaces. Natural gas was used as fuel. This study was carried out for a range of oscillating frequencies(1~5 Hz) and duty ratios(10%~40%). Furnace temperature and gas species concentrations were measured for with- and without oscillating flames. The NOx reduction efficiency for flames with oscillating combustion in comparison to flames without oscillating combustion increases with decreasing oscillating frequency and increasing duty ratio. The maximum NOx reduction efficiency was 32% in 1 Hz-40% oscillating flames. For the temperature measured at the furnace top-wall, the maximum temperature with oscillating flames was reduced at main flame regions, however, the overall temperature after main flame regions is higher than that of the flames without oscillating combustion.
화염의 이온화전류 분석을 이용한 공연비 측정에 관한 연구
김대해(Daehae Kim),장병화(Byunghwa Jang),김세원(Sewon Kim),이창엽(Changyeop Lee) 한국에너지기후변화학회 2015 에너지기후변화학회지 Vol.10 No.2
An experimental study has been conducted to measure the air fuel ratio of a flame. In this study, ion current in flame was measured and correlated with flue gas oxygen concentration. A flat type metal fiber burner has been used to generate premixed and uniform flame. The burner was attached at the bottom of cylindrical furnace to ignore the buoyancy effect. An ionization probe was designed and fabricated in order to measure the ion current in flame, and an air cooling system was prepared to maintain the temperature of electrode bars inside the probe. The experiment has been carried out in two conditions. The first experimental condition was used to analyze the ion current characteristics in various experimental parameters such as flue gas O₂ concentration, interval distance between electrode bar tips and distance between ionization probe and burner tip. And the effect of interval distance between electrode bar tips on ion current was focused in the second experiment. This study shows that it is possible to correlate ion current signal intensity with air fuel ratio of a premixed flame and this simple equipment measuring ion current can be used to control the air fuel ratio of a combustion system to increase the energy efficiency.
분할화염형 저공해 연소기의 NOx 및 CO 배출특성에 대한 실험적 연구
이창엽(Changyeop Lee),장병화(Byunghwa Jang),유미연(Miyeon Yoo),맹새롬(Saerom Maeng),소성현(Sunghyun So) 한국에너지기후변화학회 2017 에너지기후변화학회지 Vol.12 No.2
An experimental study has been performed to examine nitrogen oxides(NOx), carbon monoxide(CO) emission characteristics of a burner used for the industrial boiler. Divided Multi flames those are heavily weighted fuel lean/rich region were formed on the developed burner. It can reduce emission concentration of pollutant such as NOx because of low flame temperature and equivalence ratio control. In the experimental condition, excess air ratio of overall combustion zone was 1.21 for the clear combustion and it was fixed during the experiment. However, each small flames were classified into two types, fuel rich flame(excess air ratio was 0.7) and fuel lean flame(excess air ratio was 1.56). However, extreme fuel lean/rich condition caused flame instability and CO emission increase. In this study, mixing chambers were used to maintain the flame stable. As a result, CO emission was decreased to near zero when the temperature of combustion air was 80°C, as well as NOx emission was slightly decreased.
Graphene / 구리 복합소재의 코팅을 이용한 흐름 열전달 향상에 관한 연구
유진호(You Jin Ho),최원석(Choi Won Seok),장병화(Jang ByungHwa),박찬우(Park Chan Woo) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
In the present study, the effect of graphene coating on boiling heat transfer is being investigated under a flow of saturated R134a. Micro heater is located in the narrow channel and coated surface is attached to copper block on the heater. Cu?graphene composite martial is coated by sintering method. The boiling performance of a graphene coated surfaces are compared with those of carbon nanotubes and bare copper plate. Boiling inception occurred at a much lower heat flux and lower superheat than the others. At the nucleation process, the graphene/Cu coating sustained the best boiling performance. These trends are attributed to the effectiveness of graphene at initiating and sustaining the nucleation process. Better nucleate boiling heat transfer was also believed to result from the surface area enhancement because of an increase in the number of active nucleation sites and the presence of more small pores which are beneficial to the initiation of boiling heat transfer. In addition, graphene mesh structure provides an ideal environment for bubble nucleation. It is also believe that the high thermal conductivity of graphene assists the utilization of surface area by augmenting conduction heat transfer along the coating.