• Title/Summary/Keyword: 재순환율

Search Result 23, Processing Time 0.03 seconds

Numerical Study of Methane-hydrogen Flameless Combustion with Variation of Recirculation Rate and Hydrogen Content using 1D Opposed-flow Diffusion Flame Model of Chemkin (Chemkin 기반의 1차원 대향류 확산 화염 모델을 활용한 재순환율 및 수소 함량에 따른 메탄-수소 무화염 연소 특성 해석 연구)

  • Yu, Jiho;Park, Jinje;Lee, Yongwoon;Hong, Jongsup;Lee, Youngjae
    • Clean Technology
    • /
    • v.28 no.3
    • /
    • pp.238-248
    • /
    • 2022
  • The world is striving to transition to a carbon-neutral society. It is expected that using hydrogen instead of hydrocarbon fuel will contribute to this carbon neutrality. However, there is a need for combustion technology that controls the increased NOx emissions caused by hydrogen co-firing. Flameless combustion is one of the alternative technologies that resolves this problem. In this study, a numerical analysis was performed using the 1D opposed-flow diffusion flame model of Chemkin to analyze the characteristics of flameless combustion and the chemical reaction of methane-hydrogen fuel according to its hydrogen content and flue gas recirculation rate. In methane combustion, as the recirculation rate (Kv) increased, the temperature and heat release rate decreased due to an increase in inert gases. Also, increasing Kv from 2 to 3 achieved flameless combustion in which there was no endothermic region of heat release and the region of maximum heat release rate merged into one. In H2 100% at Kv 3, flameless combustion was achieved in terms of heat release, but it was difficult to determine whether flameless combustion was achieved in terms of flame structure. However, since the NOx formation of hydrogen flameless combustion was predicted to be similar to that of methane flameless combustion, complex considerations of flame structure, heat release, and NOx formation are needed to define hydrogen flameless combustion.

패각을 이용한 탈인법의 연구

  • Lee, Jong-Il;Kim, U-Hang
    • Proceedings of the Korean Environmental Sciences Society Conference
    • /
    • 2006.05a
    • /
    • pp.243-246
    • /
    • 2006
  • 수산양식장에서 양식 후 버려지는 패각을 이용하여 인의 제거실험을 하였다. 연속식 실험에서 재순환 하지 않은 경우와 비교할 때 300% 재순환에서는 제거율이 45%정도 증가하였다. 황산알루미늄을 주입한 후 인의 제거율을 비교했을 때 인 제거율이 93%로써 약 70%가 증가하였다. 이에 재순환율의 증가와 응집제의 주입으로 인의 제거율이 크게 향상됨을 알 수 있었다.

  • PDF

Numerical Investigation of Low-pollution Combustion with applying Flue Gas Recirculation in Counterflow Flames: Part I. Combustion Characteristics of Low NOx (대향류 화염에서 FGR이 적용된 저공해 연소의 수치적 해석: Part I. 저 NOx 연소특성)

  • Cho, Seo-Hee;Lee, Kee-Man
    • Journal of the Korean Institute of Gas
    • /
    • v.23 no.6
    • /
    • pp.8-16
    • /
    • 2019
  • One of the methods for low-pollution combustion, flue gas recirculation(FGR) is effective to reduce nitrogen oxides and it was applied in CH4/air premixed counterflow flames to identify the change of flame characteristics and NOx mechanisms. Considering that the mole fraction of the products varied depending on the strain rates, the major products: CO2, H2O, O2 and N2 were recirculated as a diluent to reflect the actual combustion system. With the application of the FGR technique, a turning point of maximum flame temperature under certain strain rate condition was found. Furthermore as the recirculation ratio increased, the tendency of NO was changed before and after the turning point and the analysis on thermal NO and Fenimore NO production was conducted.

A Study on the Use of Oyster Shells for Phosphorus Removal (인 제거를 위한 패각의 활용법에 관한 연구)

  • Lee, Jong-Il;Kim, Woo-Hang
    • Journal of the Korean Society of Marine Environment & Safety
    • /
    • v.14 no.2
    • /
    • pp.105-109
    • /
    • 2008
  • In our country, limiting nutrient is known as phosphorus in the most lakes. Therefore, the removal of phosphorus is a very important process in sewage treatment. However, many of the sewage treatment plants employ the conventional activated sludge process, known to remove $10{\sim}30%$ of phosphorus. Thus, additional phosphorous removal process will be needed. Oyster shells have been known to remove phosphorus in water. The removal efficiency of phosphorus was highest at smallest size of oyster shells and at the highest pH for batch test. The phosphorous removal rate with various calcium concentrations was increased by increasing calcium concentration. At the 20 mg/l of calcium, more than 90% of phosphorous was removed in two hours. The removal efficiency of phosphorous was increased greatly at 300% of recirculation rate. With 300% of recirculation rate, the removal efficiency reached 80% at pH 11. The negative effects of bicarbonate on crystallization were observed in oyster shells. The effects of bicarbonate on rate constant were also investigated by applying these results to experimental equation. The rate constant was decreased at the inverse logarithm bicarbonate concentration.

  • PDF

Numerical Investigation of Low-pollution Combustion with applying Flue Gas Recirculation in Counterflow Flames: Part II. Analysis of NOx formation mechanism (대향류 화염에서 FGR이 적용된 저공해 연소의 수치적 해석: Part II. NOx 생성기구 분석)

  • Cho, Seo-Hee;Kim, Gyeong-Mo;Lee, Kee-Man
    • Journal of the Korean Institute of Gas
    • /
    • v.24 no.4
    • /
    • pp.39-47
    • /
    • 2020
  • Flue gas recirculation(FGR) is an effective combustion technique for reducing nitrogen oxides(NOx) and is applied in various fields of low-pollution combustion. Continuing the previous study, a numerical analysis was conducted to identify changes of flame characteristics and NOx formation mechanism with applying FGR technique in CH4/air premixed counterflow flames. NOx emitted was divided into four main reaction paths(thermal NO, prompt NO, N2H and N2O), showing relatively the production rate of NO with the recirculation ratio. As a result, thermal NO contributed greatly to the overall NO whereas the effect of N2H was minimal. In addition, emission index of NO was compared as the recirculation ratio increased by modifying the UC San Diego mechanism to examine the contribution of thermal NO.

Optimum Drying Conditions of On-Farm Red Pepper Dryer (고추건조기의 최적운전조건)

  • Lee, Dong-Sun;Keum, Dong-Hyuk;Park, Noh-Hyun;Park, Mu-Hyun
    • Korean Journal of Food Science and Technology
    • /
    • v.21 no.5
    • /
    • pp.676-685
    • /
    • 1989
  • Optimal operating conditions of on-farm red pepper dryer were searched by using the simulation-optimization algorithm combining the drying and quality deterioration models of red pepper with Box's complex method. Determination of control variables such as air temperature, air recycle ratio and air flow rate was based on a criterion of minimizing energy consumption under the constrainst conditions that satisfied the specified color retention of carotenoids. As quality constraint was stricter, energy consumption increased and total drying time decreased with lower recycle ratio and higher air flow rate Product mixing during drying was found to be able to improve the energy efficiency and product quality. Currently used air flow rate was assessed to be increased for the optimal operation. Two stage drying at the fixed optimal air flow rate was proven to be useful means for further saying of energy consumption. In the optimal bistaged drying, the second stage began at about one third of the total drying time and low air temperature in the first stage Increased to a high value and air recycle ratio increased slightly in the second stage. Optimal control variable scheme could be explained by the dryer performance and the carotenoids destruction kinetics in red pepper drying.

  • PDF

An Experimental Study of the Variable Sonic/supersonic Ejector Systems (가변형 음속/초음속 이젝터 시스템에 관한 실험적 연구)

  • Lee Jun Hee;Kim Heuy Dong
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.29 no.5 s.236
    • /
    • pp.554-560
    • /
    • 2005
  • A new method to improve the efficiency of a hydrogen fuel cell system was introduced by using variable sonic/supersonic ejectors. To obtain the variable area ratio of the nozzle throat to ejector throat which controls the mass flow rate of the suction flow, the ejectors used a movable cylinder inserted into a conventional ejector-diffuser system. Experiments were carried out to understand the flow characteristics inside the variable ejector system. The secondary mass flow rates of subsonic and supersonic ejectors were examined by varying the operating pressure ratio and area ratio. The results showed that the variable sonic/supersonic ejectors could control the recirculation ratio by changing the throat area ratio, and also showed that the recirculation ratio increased fur the variable sonic ejector and decreased for the variable supersonic ejector, as the throat area ratio increases.

An Experimental Study on Effects of EGR Rate upon Exhaust Emissions in Small High-Speed Diesel Engines (소형 고속 디젤기관의 배기 배출물에 미치는 배기 재순환율의 영향에 관한 실험적 연구)

  • 임재근;배명환;김종일
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.16 no.4
    • /
    • pp.60-77
    • /
    • 1992
  • The effects of exhaust gas recirculation(EGR) on the characteristics of exhaust emissions and specific fuel consumption have been investigated using an eight-cylinder, four cycle, direct injection diesel engine operating at several loads and speeds. The experiments in this study are conducted on the fixed fuel injection timing of $38^{\circ}$ BTDC regardless of experimental conditions. In conclusion, it is found that $NO_{x}$ emission is markedly reduced with the drop of burnt gas temperature at high speeds and loads especially as the EGR rate increases, while the soot particulate rises with EGR rate and load at a given engine speed, especially high loads. The reduction of exhaust emissions within the Korea heavy duty diesel engine emission standards can be roughly achieved by the optimal EGR rate without degarding the specific fuel consumption, based on the correlations between exhaust emissions.

  • PDF

An Experimental Study on the Variable Sonic Ejector System (가변형 음속 이젝터 시스템에 관한 실험적 연구)

  • Lee, Jun-Hee;Jung, Sung-Jae;Kim, Heuy-Dong;Koo, Byoung-Soo
    • Proceedings of the KSME Conference
    • /
    • 2004.04a
    • /
    • pp.2035-2040
    • /
    • 2004
  • A cone cylinder is used to obtain variable operation conditions for the sonic ejector-diffuser system. The cone cylinder is designed to move upstream and downstream to change the ejector throat area ratio, thus obtaining variable mass flow rates. The present study investigates the effects of ejector throat area ratio and operating pressure ratio on the entrainment of secondary stream for the variable sonic ejector system. In experiment, the ejector throat area is varied in the range from ${\psi}=11.88$ to 66.69, and the operating pressure ratio from $p_{0p}/p_a=1.25$ to 9.0. The results show that the variable sonic ejector system is suitable for a required entrainment ratio of secondary stream by altering the ejector throat area ratio and operating pressure ratio.

  • PDF

Study on Engine Performance and Characteristics of Exhaust Gas Properties according to various EGR Feeding Methods in LPLi Engine (EGR 유입방식에 따른 LPLi 엔진 성능 및 배기 배출물 특성에 관한 연구)

  • 곽호철;명차리;박심수;천동필
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.11 no.4
    • /
    • pp.7-14
    • /
    • 2003
  • Recently, LPG has been considered as more environmental friendly fuel than liquid fuels for vehicles. However because LPLi engine has the strong point that not only increases the volumetric efficiency and cold startability, but also decreases unburned hydrocarbon exhaust emission in warm-up condition, much attention has moved to development of the Liquid Phase LPG injection (LPLi) system from the mixer type LPG engine. To reduce exhaust NOx, this study investigated the effect of EGR with LPLi engine and determined optimized EGR feeding position and distribution. In addition, engine stability, performance, and exhaust emission level were evaluated.