• 한국대기환경학회지
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• 제29권3호
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• pp.307-316
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• 2013

The sensitivity of ozone to $NO_x$ and volatile organic compounds (VOCs) emission rates under different ventilation rates and $NO_2-to-NO_x$ emission ratios in a street canyon is investigated using a chemistry box model. The carbon bond mechanism IV (CBM-IV) with 36 gaseous species and 93 chemical reactions is incorporated. $NO_x$ and VOCs emission rates considered range from 0.01 to $0.30ppb\;s^{-1}$ with intervals of $0.01ppb\;s^{-1}$. Three different ventilation rates and three different $NO_2-to-NO_x$ emission ratios are considered. The simulation results show that the ozone concentration decreases with increasing $NO_x$ emission rate but increases with increasing VOCs emission rate. When the emission ratio of VOCs to $NO_x$ is smaller than about 4, the ozone concentration is lower in the street canyon than in the background. On average, the magnitude of the sensitivity of ozone to $NO_x$ emission rate is significantly larger than that to VOCs emission rate. As the $NO_x$ emission rate increases, the magnitude of the sensitivity of ozone to $NO_x$ and VOCs emission rates decreases. Because the ozone concentration is lower in the street canyon than in the background, the increased ventilation rate enhances ozone inflow from the background. Therefore, the increase in ventilation rate results in the increase in ozone concentration and the decrease in the magnitude of the sensitivity of ozone to $NO_x$ and VOCs emission rates when the emission ratio of VOCs to $NO_x$ is smaller than about 4. On the other hand, the increase in $NO_2-to-NO_x$ emission ratio results in the increase in ozone concentration because the chemical ozone production due to the $NO_2$ photolysis is enhanced. In the present experimental setup, the contribution of the change in $NO_2-to-NO_x$ emission ratio to the change in the sensitivity of ozone to $NO_x$ emission rate is larger than that of the change in ventilation rate.

• 한국수소및신에너지학회논문집
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• 제28권2호
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• pp.220-224
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• 2017

Nitrogen dioxide ($NO_2$) is an important urban pollutant in Korea. Expecially, diesel vehicles are responsible for the most traffic rated nitrogen oxide ($NO_X$) emission, including nitric oxide (NO) and nitrogen dioxide ($NO_2$). Though nitrogen oxide ($NO_X$) emission from vehicle was applied a strict enforcement of emission standard, the specific $NO_2$ fraction in $NO_X$ ($NO_2/NO_X$) from various types of diesel vehicles was not understood. In order to investigate the fraction of $NO_2/NO_X$, the vehicle emission study was carried out at the facility of Transport Pollution Research Center (TPRC), National Institute of Environmental Research (NIER), Korea. Three different types of diesel vehicles(VAN, SUV, passenger) were tested on the NIER driving mode. The result of $NO_2/NO_X$ ratio was over 0.1 for all test vehicles and the highest $NO_2$ emission was observed at the van vehicle. The observation was showed that the emission trend of $NO_2/NO_X$ for passenger and SUV vehicles were inversely proportional. Also, as the emission standard has been strengthen, the emission rate of $NO_2$ has been decrease.

• 한국수소및신에너지학회논문집
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• 제11권1호
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• pp.1-9
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• 2000

The goals of this research are to understand the $NO_x$ emission in direct injected diesel engine with premixed hydrogen fuel. Hydrogen fuel was supplied into the test engine through the intake pipe. Amount of hydrogen-supplemented fuel was 70 percent basis heating value of the total fuel. The effects of exhaust gas recirculation(EGR) on $NO_x$ emission were studied. The exhaust gas was recirculated to the intake manifold and the amount of exhaust gas was controlled by the valve. The major conclusions of this work include: (i) the tested engine was run without backfire under 70 percent hydrogen fuel supplemented; (ii) the peak cylinder pressure was decreased with increase of EGR ratio due to the decrease of oxygen concentration in an intake pipe; and (iii) $NO_x$ emission was decreased by 77% with 30% EGR ratio. Therefore, it may be concluded that EGR is effective method to lower $NO_x$ emission in hydrogen fueled diesel engine.

• 한국환경농학회지
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• 제26권1호
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• pp.1-6
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• 2007

본 연구에서는 바이오가스의 연소엔진을 이용한 에너지 전환시에 발생되는 $NO_x$와 CO의 배출특성을 분석하고 나아가 배출계수를 산정하고자 하였다. 바이오가스의 주성분인 메탄을 70%로 한 합성가스를 이용하여 실험한 결과 연소엔진의 표준상태에서 $NO_x$와 CO가 각각 4 ppm과 100 ppm의 배출농도를 나타내었고, 이는 1.29g/MMBtu와 30.86 g/MMBtu의 배출계수 값을 산정할 수 있었다. 바이오가스의 주성분인 메탄을 60%로 한 약간의 과잉공기의 상태에서는 $NO_x$와 CO가 각각 2 ppm과 200 ppm의 배출농도를 나타내었고, 이는 정격 조건에 비해 투입열량이 적어져 연소온도의 저하로 인하여 열적 반응에 의해 생성되는 $NO_x$는 줄고, CO는 증가함을 알 수 있었다. 미국 EPA의 배출계수를 비교하기 위하여 투입된 연료의 열량을 기준으로 비교해 볼 때 본 연구의 결과가 $NO_x$의 경우 근사한 값을 보여 주었고, 이는 국내 바이오 가스 연소시의 오염배출계수로 잘 적용 가능함을 보여 주었다. 본 연구에서 사용한 가스엔진이 오염배출 측면에서 대기 환경보전법상의 배출 허용기준 내에서 가동됨을 알 수 있었고, 가동조건에 따라 연소온도를 증가시킴으로서 CO의 발생을 저감시킬 수 있으리라 사료된다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.177-179
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• 2012

This work presents an experimental investigation to study $NO_x$ emissions under stoichiometric air ratio and elevated pressure (2~10bar) in a High Press Combustor(HPC) equiped with double cone burner which was designed by Pusan Clean Coal Center(PC3). Exaust gas temperature and $NO_x$ emissions were measured at the end of the combustion chamber. The $OH^*$ radical concentration and $NO_x$ emission were decreased as a function of increasing ${\lambda}$ generally. On the other hand, $OH^*$ radical concentration and $NO_x$ emission increased with ${\lambda}$ pressure of the combustion chamber. $NO_x$ emissions which were governed by thermal $NO_x$, were highly increased under the elevated pressure, but slightly increased at sufficiently low fuel concentrations (${\lambda}>2.0$).

• 대한기계학회논문집B
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• 제31권6호
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• pp.539-546
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• 2007

An experimental study was performed to investigate the characteristics of chemiluminescence in a radiant burner, varying the excess air ratio from 0.91 to 1.67 at firing rate 80.5 to 134.2 kW/m2 on $OH^*,\;CH^*,\;{C_2}^*$ in LNG-Air premixed flames. The signals from electronically excited states of $OH^*,\;CH^*,\;{C_2}^*$ were detected using a Intensified Couple Charged Detector (ICCD) camera. The measurements of exhausted emission were made to investigate the correlation between chemiluminescence and emissions. The chemiluminescence intensity was increased with increase of firing rate like characteristics of $NO_x$ emission. $NO_x$ also increased with increase of firing rate and excess air ratio. It is found that offset of firing rate is more dominant excess air ratio $NO_x$ emission. The maximum chemiluminescence intensity occurs near the stoichiometric excess air ratio or lean conditions in case of high firing rate and the maximum intensity occurs rather than rich conditions in case of relatively low firing rate. Amount of $NO_x$ emission is maximum at near stoichiometric excess air ratio, which is chemiluminescence intensity is maximum.

• 에너지공학
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• 제23권4호
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• pp.130-140
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• 2014

공정효율 및 배기배출물 개선을 위해 로터리 킬른 버너 개발에 대한 연구는 지속적으로 이루어져 왔다. 본 연구에서는 COG(Coke Oven Gas)를 연료로 사용하는 철광석 소결용 로터리 킬른의 다공노즐버너 개발을 위해 일차공기 노즐 직경, 버너 당량비, 버너 중앙노즐과 주위노즐의 당량비 변화에 따른 화염 및 배기배출 특성에 대한 수치해석 연구를 수행하였다. 일차공기 노즐 직경이 증가함에 따라 각 동일 당량비에서 화염길이는 길어지고 $NO_x$ 배출도 증가하였으며, 버너 당량비가 증가함에 따라 화염길이와 $NO_x$ 배출이 증가하는 결과를 보였다. 버너 중앙노즐의 당량비 변화에 따라 $NO_x$ 배출에는 차이를 보였으며, 화염길이 및 킬른 내부 온도에는 큰 차이가 없었다. 본 연구를 통해 $D_2/D_1$가 1.33, 버너 당량비가 1.25이고 버너 중앙 노즐이 Rich인 조건이 킬른 내부 온도분포 및 $NO_x$ 배출량 기준을 만족하는 적절한 설계조건임을 제시하였다.

• 대한기계학회논문집B
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• 제37권5호
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• pp.481-488
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• 2013

10 %의 암모니아가 첨가된 메탄 연료의 비예혼합 확산화염에서, 산소/이산화탄소 및 산소/질소의 산화제 내에 산소 비율의 변화에 따른 질소산화물($NO_x$)의 생성 특성을 실험 및 수치해석적으로 조사하였다. 동축류 제트 화염의 실험에서, 산소/이산화탄소의 산화제인 경우, 측정된 $NO_x$은 산소 비율의 증가에 따라 약간 증가하는 경향을 보였다. 반면에, 산소/질소의 산화제인 경우, $NO_x$은 0.7의 산소 비율에서 최대로 측정되었으며, 산소 비율에 따라 비단조적인 경향을 보였다. 결과적으로, 암모니아가 첨가된 메탄 화염에서 배출되는 $NO_x$는 일반 공기의 조건보다 순산소 연소 조건의 경우가 더 크게 측정되었다. 한편, 다양한 산화제의 조건에 대하여 $NO_x$ 생성 특성을 분석하기 위해서, 동일한 화학반응 메커니즘을 적용하여 1 차원 및 2 차원의 수치해석을 수행하였다. 그 결과, 산소/질소의 산화제에서 2 차원의 수치해석 결과가 실험적으로 측정된 $NO_x$의 배출 특성을 비교적 잘 예측하였다.

• 한국수소및신에너지학회논문집
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• 제17권1호
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• pp.75-81
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• 2006

Lean premixed combustion is a well known method for low $NO_x$ gas turbine combustor. But lean combustion is usually accompanied by flame instability. To overcome this problem, the hydrogen ($H_2$) was added to main fuel methane to increase flammable limit. In this paper, the effects of hydrogen addition on lean premixed combustion of methane ($CH_4$) were investigated numerically. Results showed that the extinction stretch rate increases and the extinction temperature constant with relatively small amount of $H_2$ addition. The flame temperature and NO emission increase with $H_2$ addition at the same stretch rate and equivalence ratio but it could increase the range of lean extinction and extinction equivalence ratio limit. Eventually, the $H_2$ addition case showed almost same or lower NO emission than no addictive $CH_4$ case in the extinction condition.

• 한국분무공학회지
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• 제25권4호
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• pp.178-187
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• 2020

The current emission regulations, US Tier-4 and EU Stage-V, are only able to satisfy the regulations when all currently mass-produced emission reduction technologies such as EGR, DOC, DPF, and SCR are applied. Therefore, in this study, for the application of the Urea-SCR system to non-road diesel engines, the database was established by measuring the NO, NO2 concentration and calculating the NO2/NOx ratio based on the catalyst temperature and exhaust mass flow rate. Also, based on the measured NO2/NOx ratio data, a mathematical model was proposed to predict the NO2/NOx ratio at SCR catalyst, and the suitability of the model was verified through steady-state and transient mode. As a result of comparing the NO2/NOx ratio measured at the DOC outlet under the steady-state condition to two model values separately, the R2 was 0.9811 for the 3D map model and 0.9303 for the mathematical model. And in the case of the NO2/NOx ratio measured at the DPF outlet, the R2 was 0.9797 for the 3D map model and 0.935 for the mathematical model. It was confirmed that the R2 with the model value of the 3D Map of the mathematical model in the transient mode is 0.957, which shows high reliability.