Study on Laminar Lifted Jet Flames in Co-flow Air for Diluted Methane

Narayan P. Sapkal,Won June Lee,Jeong Park,Oh Boong Kwon 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.5

The laminar lifted jet flames in co-flow air for methane diluted with helium and nitrogen have been investigated experimentally. Such jet flames could be lifted in both buoyancy-dominated and jet momentum dominated regimes (even at nozzle exit velocities much higher than stoichiometric laminar flame speed). Chemiluminescence intensities of OH* radical (good indicators of heat release rate) and the radius of curvature for tri-brachial flame were measured using an intensified charge coupled device (ICCD) camera and digital video camera at various conditions. It was shown that, an increase in OH concentration causes increase of edge flame speed via enhanced chemical reaction in buoyancy dominated regime. In jet momentum dominated regime, an increase in radius of curvature in addition to the increased OH* concentration stabilizes such lifted flames.

Laminar Lifted Methane Jet Flames in Co-flow Air

Narayan P. Sapkal,Won June Lee,Jeong Park,Byeong Jun Lee,Oh Boong Kwon 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.12

The Laminar lifted methane jet flames diluted with helium and nitrogen in co-flow air have been investigated experimentally. The chemiluminescence intensities of OH* and CH₂O* radicals and the radius of curvature for tri-brachial flame were measured using an intensified charge coupled device (ICCD) camera, monochromator and digital video camera. The product of OH* and CH₂O* is used as a excellent proxy of heat release rate. These methane jet flames could be lifted in buoyancy and jet dominated regimes despite the Schmidt number less than unity. Lifted flames were stabilized due to buoyancy induced convection in buoyancy-dominated regime. It was confirmed that increased OH* and CH₂O* concentration caused an increase of edge flame speed via enhanced chemical reaction in buoyancy dominated regime. In jet momentum dominated regime lifted flames were observed even for nozzle exit velocities much higher than stoichiometric laminar flame speed. An increase in radius of curvature in addition to the increased OH* and CH₂O* concentration stabilizes such lifted flames.

유용에너지에 의한 이중관열 교환기의 성능 해석

권오붕 釜山水産大學校 1985 釜山水産大學 硏究報告 Vol.25 No.1

The concept of available energy is taken into acucont in this analysis. The rational efficiencies of parallel-flow and counterflow in double-pipe heat exchanger, are obtained as a function of number-of-transfer unit ??, heat capacity ratio C, dimensionless temperatures ?? and ??. The efficiency of counterflow heat exchanger is higher than that of parallel-flow heat exchanger under the same condition. The larger the values of ?? and ?? are, the higher the efficiency of double-pipe heat exchanger becomes. The larger the values of C and ?? are, the lower the efficiency becomes.

化學熱파이프 작동유체의 열특성

權五鵬 釜山水産大學校 1984 釜山水産大學 硏究報告 Vol.24 No.1

Several working fluids of chemical heat pipe were investigated and the methanation-reforming reaction was considered to be the most feasible one for the chemical heat pipe system. For the selected methanation-reforming reaction, the ratios at equilibrium state were calculated and carbon formation could be avoided by use of 5:1 H₂to CO ratio. In this case, conductivities, viscosities and specific heats of equilibrium components were calculated. In the case of conductivity, the highest values are given by endothermic components and lowest values by exothermic components; equilibrium components have the conductivities that lie in between. The revers is true in the case of specific heat. In the case of viscosity, all three values of endothermic, exothermic and equilibrium components are almost the same at given temperature.

MgCl₂ 溶液中에서 SUS 304 鋼 鎔接部의 SCC억제에 관한 연구

임우조,권오봉 釜山水産大學校 1986 釜山水産大學 硏究報告 Vol.26 No.1-2

SUS 304 鋼 鎔接部에 대해 여러가지 濃度의 비등 염화 마그네슘 溶液中에서 SCC 억제를 위한 방법으로서 電氣防蝕法을 실시하여, 一定負荷에서 濃度 條件에 따른 限界 防融電流密度를 究明하였다. 중요한 結果를 要約하면 다음과 같다. 1) SCC 억제를 위한 限界 防融電流密度 以下로 防蝕할 때 용접열 영향부의 龜裂初期 潛伏時間은 모재보다 용접열 사이클로 인한 銳敏化 및 軟化 현상에 의해 빨라진다. 2) 일정한 防蝕電流密度下에서 용접열 영향부의 SCC 억제는 MgCl溶液의 限界濃度에 의해 제어될 수 있다. 3) 용접열 영향부의 限界防融電流密度는 MgCl₂溶液의 濃度에 비례해서 증가한다. The anti-stress corrosion cracking method by current density of cathodic protection was studied for stress corrosion cracking of SUS 304 stainless steel weldments in the environment of various MgCl₂boiling solution(wt%). Main results obtained are as follows: 1) Under the conditions below the critical current density of cathodic protection for anti-stress corrosion cracking, the latent time of crack initiation of weld heat affected zone occurs more rapidly than that of base metal because of the phenomenon of sensitizing and softening caused by weld heat cycles. 2) Under the constant current density of cathodic protection, the anti-stress corrosion cracking of weld heat affected zone can be controlled by critical concentration of MgCl₂solution. 3) The critical current density of cathodic protection of weld heat affected zone increases in proportion to concentration of MgCl₂solution.

H₂-공기와 CO-공기 예혼합 화염 사이의 후류상호작용에 있어서 H₂O 첨가 효과

박정(Jeong Park),권오붕(Oh Boong Kwon),김태형(Tae Hyung Kim),박종호(Jong Ho Park) 한국연소학회 2015 한국연소학회지 Vol.20 No.1

Numerical study was conducted to clarify effects of added H₂O for the downstream interaction between H₂-air and CO-air premixed flames in counterflow configuration. The reaction mechanism adopted was Davis model which had been known to be well in agreement with reliable experimental data. The results showed that both lean and rich flammable limits were reduced in increase of strain rate. The most discernible difference between the two with and without having H₂O and/or H₂ addition into H₂-air and CO-air premixtures was two flammable islands for the former and one island for the latter at high strain flame conditions. Even a small amount of H₂, in which H₂-air premixed flame cannot be sustained by itself, participates in CO oxidation, thereby altering the CO-oxidation reaction path from the main reaction route CO + O₂ → CO₂ + O with a very long chemical time in CO-air flame to the OH-related reaction routes including CO + OH → CO₂ + H with very short chemical times. This intrinsic nature alters flame stability maps appreciably. The results also showed that chemical effects of added H₂O help lean flames at relatively low strain rate be sustained, and suppress the flame stabilization at high strain rates.

H₂-공기와 CO-공기 예혼합 화염 사이의 후류상호작용에 있어서 H₂O 첨가 효과

박정,권오붕,김태형,박종호,Park, Jeong,Kwon, Oh Boong,Kim, Tae Hyung,Park, Jong Ho 한국연소학회 2015 한국연소학회지 Vol.20 No.1

Numerical study was conducted to clarify effects of added $H_2O$ for the downstream interaction between $H_2$-air and CO-air premixed flames in counterflow configuration. The reaction mechanism adopted was Davis model which had been known to be well in agreement with reliable experimental data. The results showed that both lean and rich flammable limits were reduced in increase of strain rate. The most discernible difference between the two with and without having $H_2O$ and/or $H_2$ addition into $H_2$-air and CO-air premixtures was two flammable islands for the former and one island for the latter at high strain flame conditions. Even a small amount of $H_2$, in which $H_2$-air premixed flame cannot be sustained by itself, participates in CO oxidation, thereby altering the CO-oxidation reaction path from the main reaction route $CO+O_2{\rightarrow}CO_2+O$ with a very long chemical time in CO-air flame to the OH-related reaction routes including $CO+OH{\rightarrow}CO_2+H$ with very short chemical times. This intrinsic nature alters flame stability maps appreciably. The results also showed that chemical effects of added $H_2O$ help lean flames at relatively low strain rate be sustained, and suppress the flame stabilization at high strain rates.

Large Deformation Formulation of a Hypoelasto-plastic Constitutive Model for Soils

Oh, Se-Boong,Lee, Seung-Hyun,Kwon, Oh-Kyun 한국지반공학회 2003 지반 : 한국지반공학회지 Vol.19 No.4

A constitutive equation was implemented in order to model the behavior in overall ranges from small to large strains, which is based on anisotropic hardening rule and total stress concept. The constitutive model was implemented in ABAQUS code in which large deformation analysis can be performed accurately and efficiently. The formulation includes (1) finite strain plasticity on the basis of Jaumann stress rate, (2) implicit stress integration and (3) consistent tangent moduli. A large deformation analysis was performed with the constitutive model using ABAQUS program. In the analysis of an actual embankment, it was found that the proposed model was formulated accurately and efficiently. 미소변형에서 대변형에 이르는 전변형도 영역의 거동을 모델하기 위하여 비등방 경화규칙과 전응력개념에 의거한 구성관계를 이용하였다. 이러한 구성관계는 ABAQUS 코드에 구현되었으며 대변형해석시 정확도와 수렴속도를 확보하도록 하였다. 이 정식화는 Jaumann 응력속도에 의거한 유한 변형도 소성론, 내재적 응력적분, 일관된 접선계수를 포함한다. ABAQUS를 이용한 대변형해석을 통하여 알고리즘의 정확도 및 수렴도 해석을 할 수 있었다.

벽면에서의 입자 충돌(衝突)에 의한 열전달 수치 모델

권오붕 ( Oh Boong Kwon ),( M. M. Chen ) 한국어업기술학회 1995 수산해양기술연구 Vol.31 No.3

고압실 형상에 따른 환형 제트펌프의 특성

권오붕 ( Oh Boong Kwon ),오병화 ( Byung Hwa Oh ),김명관 ( Myong Kwan Kim ),신현옥 ( Hyeon Ok Shin ),정석권 ( Seok Kwon Jeong ) 한국어업기술학회 1999 수산해양기술연구 Vol.35 No.4