• 대한기계학회논문집B
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• 제22권12호
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• pp.1691-1701
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• 1998

Fly ash produced in coal combustion is a fine-grained material consisting mostly of spherical, glassy, and porous particles. A study on the formation mechanism of the fly ash from coal particles in the pulverized coal power plant is investigated with a physical, morphological, and chemical characteristic analysis of fly ash collected from the Samchonpo power plant. This study may contribute to the data base of domestic fly ash, the improvement of combustion efficiency, fouling phenomena and ash collection in the electrostatic precipitator. The physical property of fly ash is determined using a particle counter for the measurement of ash size distribution. Morphological characteristic of fly ash is performed using a scanning electron micrograph. The chemical components of fly ash are determined using an inductively coupled plasma emission spectrometry(ICP). The distribution of fly ash size was bi-modal and ranged from 12 to $19{\mu}m$ in mass median diameter. Exposure conditions of flue gas temperature and duration within the combustion zone of the boiler played an important role on the morphological properties of the fly ash such as shape, particle size and chemical components. The evolution of ash formation during pulverized coal combustion has revealed three major mechanisms by large particle formation due to break-up process, gas to particle conversion and growth by coagulation and agglomeration.

• 조명전기설비학회논문지
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• 제24권5호
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• pp.152-159
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• 2010

가공전력선이 통과하는 지역에서 발생된 연소화염은 계통 섬락사고의 원인이 되고 있다. 본 논문에서는 연소화염에 의한 전력선의 절연내력 저하특성과 화염의 형상변화를 알아보기 위해, 직류 및 교류 전압 인가시 전력선을 모의한 대기압 공기 갭에 대한 섬락특성과 화염의 소화특성을 조사하였다. 실험 결과, 화염에 의한 섬락현상은 비교적 작은 갭에서 발생되었으며, 수평배치형 침대침 갭에서 교류 섬락전압의 상대값은 평균 37.3[%]인 것으로 나타나 화염이 없는 경우에 비해 크게 저하하였다. 갭 길이가 증가함에 따라 전극간 섬락이 발생되기 전에 침전극로부터 발생된 코로나풍에 의해 화염은 소화되는 현상이 나타났다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.150-155
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• 2010

액체로켓 분사기는 추진 성능과 연소 안정성, 그리고 열유속 특성을 지배하는 가장 중요한 요소이다. 그러나 분사기 근방에서 일어나는 고압 연소 현상에 대한 근본적인 이해의 부족으로 분사기의 개발 과정은 대부분 경험적 설계방법과 고비용의 연소시험에 의존해 왔다. 본 연구는 액체로켓 연소 모델링과 관련된 최근 연구 동향들을 토대로 시작되었다. 층류화염편 기반의 난류연소모델을 초임계 압력 조건에서 나타나는 실제유체 거동을 고려할 수 있도록 확장하였으며, 극저온 질소분사, 상압 조건하의 난류제트화염, 그리고 고압의 기체수소/액체산소 동축 분사기에 적용하여 해석모델의 효용성을 확인하였다.

• 대한기계학회논문집
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• 제11권2호
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• pp.271-278
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• 1987

본 논문에서는 공기밸브형 진동연소기에 관한 이해를 더 증진시키기 위해서 기본적인 공기밸브형 진동연소기를 제작해서 압력진동 및 발생되는 소음특성, 작동주 파수, 그리고 연소특성에 관해 실험적 고찰을 행했다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.341-350
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• 2011

마이크로 크기의 단일 마그네슘 입자의 연소 해석을 위해 간단하면서도 점화와 연소과정 전체를 모사한 모델을 사용하여 각각의 주요 파라메터별 영향을 도출하는 연구를 수행하였다. 계산에 사용된 모델은 액적 연소의 경우와 유사하게 보존 및 이송 방정식들을 사용하여 모사되었으며 입자의 온도가 1200 K에 도달하면 점화단계를 종료하고 준정상연소 단계로 전환되었다. 선행 연구를 참고하여 주요 파라메터를 선정하였으며 주요 파라메터로는 초기 입자크기, 대류 열전달의 유무, 외기 온도, 압력 등이 선정되었고, 간단한 열역학적 모델임에도 불구하고 정량적으로 실험 데이터와 유사하게 각각의 파라메터의 영향을 평가할 수 있음을 확인하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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• pp.123-132
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• 2002

A numerical study was conducted to investigate the combustion phenomena of normal start and unstart processes based on ISL's RAMAC 30 experiments with different diluent amounts and fill pressures in a ram accelerator. The initial projectile launching speed was 1.8 km/s which corresponded to the superdetonative speed of the stoichiometric $H_2/O_2$ mixture diluted with 5 $CO_2$ or 4 $CO_2$. Experiments with same condition except for projectile surface material demonstrated that ignition was successful with an aluminum projectile, but no combustion was observed in case of a steel projectile. In this study, it was found that neither shock nor viscous heating was sufficient to ignite the mixture at a low speed of 1.8 km/s, as was found in the experiments using a steel projectile. However, we could succeed in igniting the mixtures by imposing a minimal amount of additional heat to the combustor section and simulate the normal start and unstart processes found in the experiments with an aluminum projectile. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations coupled with a Baldwin-Lomax turbulence model and detailed chemistry reaction equations of $H_2/O_2/CO_2$ suitable for high-pressure gaseous combustion were considered. The governing equations were discretized by a high order accurate upwind scheme and solved in a fully coupled manner with a fully implicit, time accurate integration method. The numerical results matched almost exactly to the experimental results. As a result, it was found that the normal start and unstart processes depended on the strength of gas mixture, development of shock-induced combustion wave stabilized by the first separation bubble, and its size and location.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.451-454
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• 2006

This paper describes the results of cold flow test and hot firing tests of an uni-element coaxial swirl injector and hot firing tests of a subscale combustor, as to the development effort of coaxial swirl injector for high performance liquid rocket engine combustor. A major design parameter for coaxial swirl injector is the recess number of a bi-swirl injector. The results of hot firing tests of the uni-element injector combustor and the sub-scale combustor are analyzed to investigate the effect of the recess number influencing on the combustion performance and pressure fluctuation. The test results of a cold flow test of the unielement combustor shows that it was shown that the change in recess number has significant effect on mixing characteristics and efficiency, while the effect of recess number on atomization characteristic is not The results of a series of firing tests using unielement and subscale combustor show that the recess length significantly affects the hydraulic characteristics, the combustion efficiency, and the dynamics of the liquid oxygen/kerosene bi-swirl injector. As a point of combustion performance, combustion efficiencies are 90% for unielement combustor and 95% for subscale combustor. The difference in the characteristic velocities between the unielement combustor and the subscale combustor may be caused by the difference in thermal loss to the combustor wall and the relative lengths of the combustion chamber. For a mixed type coaxial swirl combustor, the pressure drop across the injector increases as recess number becomes larger. The low frequency pressure fluctuation observed in unielement combustor can be related to the propellant mixing characteristics of the coaxial bi-swirl injector. The effect of the recess number on the pressure fluctuation inside the combustion chamber is more significant in un i-element combustor than the subscale combustor, of which the phenomena are also observed in time domain and frequency domain.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.146-153
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• 2011

American NREL (National Renewable Energy Laboratory) reported that BDF20 could reduce PM, CO, SOx, and cancerogenic matters by 13.6%, 9.3%, 17.6%, and 13% respectively, compared to diesel fuel. BDF20 has been being tested on garbage trucks and official vehicles at Seoul City, which is positive on air environment, but negative on combustion by higher viscosity in winter season. This study investigated the combustion characteristics by applying pilot injection for improving the deterioration of combustibility caused by the higher viscosity of the BDF20 with the combustion flames taken by a high-speed camera and the cylinder pressure diagram. A 4-cycle single-cylinder diesel engine was remodeled to a visible 2-cycle engine taking the flame photographs, which has a common-rail injection system. The test was done laboratory temperature at $5{\sim}6^{\circ}C$. The results obtained are summarized as follows, (1) In the case of without pilot injection, the flame propagation speed was slowed and the maximum combustion pressure became lower. The phenomena became further aggravated as the fuel viscosity gets higher. (2) In the case of with pilot injection, early stage of combustion such as rapid ignition timing and flame propagation was activated since intermediate products formed by pilot injection act as a catalyst for combustion of main fuel.

• 조명전기설비학회논문지
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• 제16권1호
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• pp.27-34
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• 2002

본 연구에서는 불평등 전계인 침대침 갭을 수평배치하였을 때, 고전압 전극 부근에 설치한 화염에 의한 교류 및 직류 섬락전압 특성을 조사하였다. 화염에 의해 섬락이 발생할 때, 코로나 개시전압과 섬락극성을 조사하기 위해 전압 및 전류파형을 측정하였으며, 인가전압의 상승에 따른 코로나풍과 쿨롱력에 의한 화염의 형상이 왜곡되고 요동되는 현상을 관찰하였다. 실험 결과, 화염이 전극의 중간위치에 있을 때 화염에 의한 교류 섬락전압은 화염이 없는 경우에 비해 평균 62.7[%] 저하된 것으로 나타났으며, 화염의 높이에 따른 섬락전압의 특성에서 화염의 높이 h=5, h=7 및 h=9[cm]인 경우 교류 섬락전압의 평균값은 화염이 없을 때에 비해 각각 34.2[%], 27.3[%] 및 21.4[%] 저하된 것으로 나타났다.

• 대한기계학회논문집B
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• 제21권2호
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• pp.213-223
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• 1997

Premixed flame is better than diffusion flame to accomplish a high loading combustion. Since the turbulent characteristics of unburned mixture has a great influence on the flame structure, it is general that many researchers realize a high loading combustion with strengthening turbulent intensity of unburned mixture. Because turbulent premixed flame reacts efficiently on the condition of distributed reaction region, we made high turbulent premixed flame in the doubled impingement field. We investigated turbulent characteristics of unburned mixture with increasing shear force and visualized flames with direct and Schlieren photographs. And the combustion characteristics of flame was elucidated by instantaneous temperature measurement with a thermocouple, by ion currents with a micro electrostatic probe, by radical luminescence intensity and local equivalence ratio. Extremely strong turbulent of small scale is generated by impingement of mixture, and turbulent intensity of unburned mixture increased with the mean velocity. As a result of direct photographs, visible region of flame became longer due to increasing central direction flux. But as strengthed turbulent intensity, visible region of flame turned to shorter and reaction occurred efficiently. As strengthened turbulent intensity of mixture with increasing flux of central direction, maximum fluctuating temperature region moved to radial direction and fluctuation of temperature became lower. The reason is influx of central direction which caused flame zone to move toward radial direction, to maintain flame zone stable and to make flame scale smaller.