• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제21회 KOSCO SYMPOSIUM 논문집
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• pp.83-91
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• 2000

A numerical study was carried out to investigate the 'unstart' process of thermally-choked combustion in model scramjet engines. The combustion mechanism of supersonic combustor will be compared with the experimental results obtained from the T3 free-piston shock tunnel at ANU (Australian National University) and the high enthalpy supersonic wind tunnel at UT (University of Tokyo). For the numerical simulation of supersonic combustion. multi-species Navier-Stokes equations were considered. and detailed chemistry reaction mechanism of $H_2$-Air were adopted. The governing equations were solved by Roe's FDS method and LU-SGS method with MUSCL scheme. In this study. it is found that the thermal choking process could result from excessive heat release due to combustion. In detail, sufficient heat release could be generated at local region of very high temperature increased by reflection of shock waves or vortex sheets. Accordingly the flow of downstream of the combustor fell to subsonic field propagated upstream along the combustor. Sometimes the subsonic flow field propagated into isolator could generate precombustion shock waves in the isolator.

• 한국안전학회지
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• 제32권3호
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• pp.8-14
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• 2017

This study examined the combustion and thermal characteristics of imported woods for building materials in Korea. Wooden specimens were confirmed by a cone calorimeter according to the KS F ISO 5660-1 standard. The combustion properties of the wooden specimens were measured in terms of the heat release rate (HRR), total heat released (THR), mass lose rate (MLR), and ignition time (time to ignition; TTI). The optical microscope was used for determine the anatomical characteristics of wood pit and structure. Also, the thermal properties were measured by thermogravimetric analysis (TGA) to determine the thermal stability of wooden specimens. The result of this experiment would be useful for fundamentals of guiding the combustion properties and thermal stability using wood application.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.341-345
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• 2005

본 논문은 액체로켓엔진용의 약 1.5MW급 터빈을 구동할 수 있고, 액체산소와 케로신을 추진제로 하는 연료과잉 영역에서 작동하는 실물형 가스발생기의 고압연소특성에 대한 것이다. 실물형 가스발생기 개발과정의 개략적인 과정, 연소시험 결과 분석에 따른 혼합비와 온도관계식, 연소가스의 물성치인 분자량 및 비열비 등에 대한 내용을 기술하였다. 혼합비에 따른 온도관계식을 고압에서 새롭게 얻을 수 있었으며 연소가스의 분자량 및 비열비를 수정하고 유량관계식을 통해 이들의 타당성을 확인하였다.

• 한국연소학회지
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• 제20권3호
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• pp.35-42
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• 2015

Investigating coal combustion in a large-scale boiler using computational fluid dynamics (CFD) requires a combination of flow and reaction models. These models include a number of rate constants which are often difficult to determine or validate for particular coals or furnaces. Nonetheless, CFD plays an important role in developing new combustion technologies and improving the operation. In this study, the model selection and rate constants for coal devolatilization, char conversion, and turbulent reaction were evaluated for a commercial wall-firing boiler. The influence of devolatilization and char reaction models was found not significant on the overall temperature distribution and heat transfer rate. However, the difference in the flame shapes near the burners were noticeable. Compared to the coal conversion models, the rate constant used for the eddy dissipation rate of gaseous reactions had a larger influence on the temperature and heat transfer rate. Based on the operation data, a value for the rate constant was recommended.

• 대한기계학회논문집B
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• 제33권12호
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• pp.968-976
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• 2009

As the global warming becomes a serious environmental problem, studies of reducing $CO_2$ emission in power generation area are in progress all over the world. One of the carbon capture and storage(CCS) technologies is known as oxy-fuel combustion power generation system. In the oxy-fuel combustion system, the exhaust gas is mainly composed of $CO_2$ and $H_2O$. Thus, high-purity $CO_2$ can be obtained after a proper $H_2O$ removal process. In this paper, an oxy-fuel combustion cycle that recovers the waste heat of a high-temperature fuel cell is analyzed thermodynamically. Variations of characteristics of $CO_2$ and $H_2O$ mixture which is extracted from the condenser and power consumption required to obtain highly-pure $CO_2$ gas were examined according to the variation of the condensing pressure. The influence of the number of compression stages on the power consumption of the $CO_2$ capture process was analyzed, and the overall system performance was also investigated.

• 한국추진공학회지
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• 제15권1호
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• pp.1-10
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• 2011

가스연소와 촉매연소 실험을 통해 열교환 연소기의 연소 및 소염한계에 대하여 레이놀즈 수에 적용하여 성능평가를 수행하였으며, 마이크로 스케일 연소 장치에 대한 적용 가능성에 대해 살펴보았다. 본 논문에서는 연소기의 특성을 살펴보기 위해 나선형 연소기의 물리적 크기와 회전수를 변화시킨 스위스롤 연소기를 제작하여 실험을 수행하였다. 또한 연소가스 분석을 통한 연소효율에 대해서도 살펴보았다. 실험 결과를 바탕으로 스위스롤 연소기의 최적 작동상태에 대해서도 분석하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.356-361
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• 2003

The objective of this study is a qualitative comparison between line-integrated OH chemiluminescence ($OH{\ast}$) image and its Abel inversion image at different phase of the oscillating pressure field. PIV(Particle Image Velocimetry) measurements were conducted under non-reacting conditions to see the global flow structure. Also NOx emission was measured to investigate the effect of fuel-air premixing on combustion instability and emission characteristics. Experiments were carried out in an atmospheric pressure, laboratory-scale dump combustor operating on natural gas. Combustion instabilities in present study exhibited a longitudinal mode with a dominant frequency of ${\sim}341.8$ Hz, which corresponded to a quarter wave mode of combustor. Heat release and pressure waves were in-phase when instability occurred. Results gave an insight about the location where the strong coherence of pressure and heat release existed. Also an additional information on active control to suppress the combustion instabilities was obtained. For lean premixed combustion, strong correlation between $OH{\ast}$ and NOx emissions was expected largely due to the exponential dependence of thermal NOx mechanism on flame temperature.

• 한국화재소방학회논문지
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• 제17권4호
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• pp.7-12
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• 2003

연소열은 인화성 물질의 화재$.$폭발 위험성을 결정하는 주요한 물성치이다. 할로겐화 유기화합물의 순연소열을 예측하기 위해서, 원자기여법에 기반을 둔 경험식들이 개발되어 왔다. 본 연구에 개발된 경험식을 Cardozo와 Hanley의 경험식들과 비교해 보았다. A.A.D.를 보면 알 수 있듯이 본 연구에서 제안된 경험식으로 계산된 값이 실험값에 가장 근접해 있음을 확인하였다. 따라서, 본 연구에서 제안된 경험식은 여타 할로겐화 유기화합물의 연소열을 예측하는데 도움을 줄 것으로 사료된다.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.295-301
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• 2006

A new combustion method of high compression ratio SI engine was studied and proposed in order to achieve high thermal efficiency, comparable to that of CI engine. Compression ratio of SI engine is generally restricted by the knocking phenomena. A combustion chamber profile and a cranking mechanism were studied to avoid knocking with high compression ratio. Because reducing the end-gas temperature will suppress knocking, a combustion chamber was considered to have a wide surface at the end-gas region. However, wide surface will lead to large heat loss, which may cancel the gain of higher compression ratio operation. Thereby, a special cranking mechanism was adapted which allowed the piston to move rapidly near TDC. Numerical simulations were performed to optimize the cranking mechanism for achieving high thermal efficiency. An elliptic gear system and a leaf-shape gear system were employed in numerical simulations. Livengood-Wu integral, which is widely used to judge knocking occurrence, was calculated to verify the effect for the new concept. As a result, this concept can be operated at compression ratio of fourteen using a regular gasoline. A new single cylinder engine with compression ratio of twelve and TGV(Tumble Generation Valve) to enhance the turbulence and combustion speed was designed and built for proving its performance. The test results verified the predictions. Thermal efficiency was improve over 10% with compression ratio of twelve compared to an original engine with compression ratio of ten when strong turbulence was generated using TGV, leading to a fast combustion speed and reduced heat loss.

• 대한기계학회논문집
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• 제13권5호
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• pp.962-978
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• 1989

본 연구에서는 저자들이 이미 발표한 난류 화염에서의 매연 농도 분포 해석을 포함한 화염 구조 및 복사 열전달의 해석에 대한 연구와 관련하여, 난류 화염에서의 생성된 매연 입자의 재연소 속도에 관한 새로운 모델을 제시한다.구체적인 방법 으로, 난류 화염에 대한 난류 지배 방정식의 매듭(closure) 문제로서 문제가 되고 있는 난류 모델과 반응 속도 모델에 대해서는 비교적 잘 정립되어 있다고 할 수 있는 축대칭 분류 유동을 선택하여, 난류 모델과 난류 연소 속도 모델을 고정하고, 난류 화염에서의 매연 생성 및 연소 모델을 검토하였다.