• 대한기계학회논문집B
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• 제26권11호
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• pp.1531-1541
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• 2002

The NOx emission characteristics of C$H_4$-Air coflow jet flames were numerically and experimentally investigated. NOx was measured using a chemiluminescent detection and calculated by the parabolic -type equation solver with a detatiled NOx chemistry. The fuel flow rate( $Q_{F}$), the diameter of mixture nozzle and the equivalence rate(Ф) were varied to discuss the EINOx of each flames at the various combustion conditions. The NOx emission index(EINOx) was introduced to quantify the NOx emission from the parametrically varied flames. The results show that Prompt EINOx increases on a logarithmic profile with increasing ${\Phi}$ and keeps nearly constant for the variation of $Q_{F}$. Thermal EINOx reaches the maximum value at around ${\Phi}$ =1.5 and then slowly decrease for ${\Phi}$ >1.5. In addition, Thermal EINOx increases with increasing $Q_{F}$, but nearly indifferent to the variation of the mixture nozzle diameter. Total EINOx also shows a peak at around ${\Phi}$ =1.5, followed by a relatively sharp decrease for 1.5< ${\Phi}$ <2.5 and increase slowly for 2.5 < ${\Phi}$ < $\infty$ The present Total EINOx trend is well explained by a combination of above Thermal and Prompt EINOx trend with the variation of ${\Phi}$ n of ${\Phi}$.

• 한국안전학회지
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• 제17권3호
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• pp.43-49
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• 2002

The NOx emission characteristics of double-concentric diffusion flames and normal diffusion flames fueled with CH$_4$ were studied. Experimental and numerical investigations were carried out for double-concentric diffusion flame with varying central air flow rate and normal diffusion flame. The Emission indices of NOx(EINOx) were measured by chemiluminescent method and calculated by numerical model based on detailed chemistry. From the comparison between double-concentric diffusion flames and normal diffusion flames, the results show that EINOx of double-concentric diffusion flames are lower than normal diffusion flame, because of Prompt EINOx was decreased. EINOx of double-concentric diffusion flames increase with central air flow rate increasing.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제22회 KOSCI SYMPOSIUM 논문집
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• pp.147-155
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• 2001

The NOx emission characteristics of jet flames fueled with $H_2$ and $CH_4$ were studied. Experimental and numerical investigations were carried out for various flames with varying equivalence ratio, fuel flow rate and nozzle diameter. The Emission indices of NOx(EINOx) were measured by chemiluminescent method and calculated by simulation using detailed chemistry. The results show that EINOx of $CH_4$ and $H_2$ flames have different trends in terms of equivalence ratio and fuel flow rate but have the same trends in terms of nozzle diameter. These differences can be explained by the following Thermal and Prompt trends in both flames. Thermal EINOx trends can be describe in function of residence time in the high-temperature region weighted by the maximum flame temperature and Prompt EINOx trends can be described in function of flame surface area of each combustion conditions.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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• pp.35-44
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• 2000

It was numerically studied that NOx emission characteristics of confined $CH_{4}$ jet flames with the variation of the diameter of inner fuel nozzle, the flow rate of $CH_{4}$ and equivalence ratio. Parabolic type equations were adopted in the calculation and GRI-2.1I mechanism was used for the chemical reaction. NOx emission index (EINOx) was introduced to evaluate NOx emission quantitatively in parametrically varied flames and the contribution of Thermal and Prompt NO mechanism was discussed. The results showed that Total EINOx varied sensitively with the variation of the flow rate of$CH_{4}$ but it was not sensitive to the variation of the diameter of inner fuel nozzle. Thermal EINOx showed the similar tendency to total EINOx and Prompt EINOx showed insensitivity to the variation of the diameter of inner fuel nozzle and the flow rate of $CH_{4}$.

• 한국안전학회지
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• 제16권4호
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• pp.82-87
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• 2001

The NOx emission characteristics of jet flames fueled with It was studied. Experimental and numerical investigations were carried out for various flames with varying equivalence ratio, fuel flow rate and nozzle diameter. The Emission indices of NOx(EINOx) were measured by chemiluminescent method and calculated by simulation using detailed chemistry. The results show that the numerical results represent well the trends of EINOx experimentally observed. EINOx of H$_2$ flame steeply increase at small equivalence ratio, gently increase and steady at more than equivalence ratio is 4.0. EINOx trends of H$_2$ flame can be describe in function of residence time in the high-temperature region weighted by the maximum flame temperature.

• 한국연소학회지
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• 제6권1호
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• pp.36-43
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• 2001

The NOx emission characteristics of jet flames fueled with $H_2\;and\;CH_4$ were studied. Experimental and numerical investigations were carried out for various flames with varying equivalence ratio, fuel flow rate and nozzle diameter. The Emission indices of NOx(EINOx) were measured by chemiluminescent method and calculated by numerical model based on detailed chemistry. The results show that EINOx of $CH_4\;and\;H_2$ flames have different trends in terms of equivalence ratio and fuel flow rate but have the same trends in terms of nozzle diameter. These differences can be explained by the following Thermal and Prompt trends in both flames. Thermal EINOx is quite sensitive to the residence time in the high-temperature region weighted by the maximum flame temperature. Prompt EINOx is mainly influenced by flame surface area of each combustion conditions.

• 한국연소학회지
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• 제17권4호
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• pp.30-37
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• 2012

The flame lengths and NOx emission characteristics of syngas $H_2$/CO turbulent non-premixed jet flames were investigated. The flame length which is the main parameter governs NOx emission was studied for various syngas compositions. The flame length was compared with previous correlation between Froude number and flame height and it shows that they have good agreements. It was confirmed that the turbulent jet flames herein investigated are in the region of buoyancy-momentum transition. NOx emission was reduced with increased Reynolds number and CO contents in syngas fuel and with decreased fuel nozzle diameter which is attributed by decreased flame residence time. Previous EINOx scaling based on flame residence time of $L_f^3/(d_f^2U_f)$ satisfies only the jet flame in momentum-dominated region, not buoyancy-momentum transition region. The simplified flame residence time ($L_f/U_f$) was adopted in modified EINOx scaling. The modified scaling satisfies the jet flames not only in momentum-dominated region but in buoyancy-momentum transition region. The scaling is also satisfied with $H_2$/CO syngas jet flames.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.55-58
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• 2012

EINOx scaling for $H_2/CO$ non-premixed turbulent jet flame was conducted. NOx concentration and flame length were measured simultaneously with varying flow conditions. Flame length increases with Reynolds number which means the flames in buoyancy-momentum transition region. We assessed the previous Chen & Driscoll's scaling with present results. However, the scaling cannot satisfy the present results. We proposed new scaling which is addressed the simplified flame residence time. The new scaling satisfies the results of $H_2/CO$ syngas flame as well as pure hydrogen flames.

• 대한기계학회논문집B
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• 제34권3호
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• pp.275-282
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• 2010

동축공기 수소 난류 확산화염에서 선회류가 NOx에 미치는 영향을 연구하였다. 공기와의 혼합을 증가시키기 위해 동축공기관에 스월러의 각도를 30, 45, 60, $90^{\circ}$로 바꾸어가며 화염길이와 질소산화물 배출수준을 측정하였다. 연료 속도를 85.7~160.2 m/s, 동축공기 속도는 7.4~14.4 m/s로 조절하였다. 실험을 통해 동축 공기 속도 증가에 따라 화염길이와 질소산화물 배출수준은 증가하였고, 회전류 증가에 따라 감소함을 관찰하였다. EINOx에 미치는 동축공기와 회전류 영향을 상사하기 위하여 far-field 개념의 유효직경($d_{F,eff}$)을 도입하여 동축공기와 선회류에 의한 혼합효과를 표현하였다. 질소산화물 배기배출지표는 화염체류시간(${\sim}{\tau_R}^{1/2.8}$)과 전체 신장률(${\sim}{S_G}^{1/2.8}$)에 영향을 받았다.

• 한국연소학회지
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• 제4권1호
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• pp.131-139
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• 1999

A Numerical Analysis of NOx production in Hydrogen-Air flame is performed using the quasi-laminar reaction modelling. As results, in low global strain rate region, $U_F/D_F\;{\leq}\;50,000$, the quasi-laminar reaction modelling reproduces the experimentally observed EINOx half power scaling that the ratio of EINOx and flame residence time, $L_f^3(D_F^2U_F)$, is proportional to the square root of global strain rate. Thus, it suggests that turbulence-chemistry interaction has a minor impact on the trend of NOx production in low global strain rate region. However, the quasi-laminar reaction modelling predicts the higher temperature and NOx than experimentally observed. This overprediction may be due to the lack of radiation and quasi-laminar reaction modelling.