• Title/Summary/Keyword: flammability limit

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Emission Reduction Characteristics of Three-way Catalyst with Engine Operating Condition Change in an Ultra-lean Gasoline Direct Injection Engine (초희박 직접분사식 가솔린 엔진용 삼원촉매의 운전조건에 따른 배기저감 특성)

  • Park, Cheol Woong;Lee, Sun Youp;Yi, Ui Hyung;Lee, Jang Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.9
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    • pp.727-734
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    • 2015
  • Recently, because of the increased oil prices globally, there have been studies investigating the improvement of fuel-conversion efficiency in internal combustion engines. The improvements realized in thermal efficiency using lean combustion are essential because they enable us to realize higher thermal efficiency in gasoline engines because lean combustion leads to an increase in the heat-capacity ratio and a reduction of the combustion temperature. Gasoline direct injection (GDI) engines enable lean combustion by injecting fuel directly into the cylinder and controlling the combustion parameters precisely. However, the extension of the flammability limit and the stabilization of lean combustion are required for the commercialization of GDI engines. The reduction characteristics of three-way catalysts (TWC) for lean combustion engines are somewhat limited owing to the high excess air ratio and low exhaust gas temperature. Therefore, in the present study, we assess the reaction of exhaust gases and their production in terms of the development of efficient TWCs for lean-burn GDI engines at 2000 rpm / BMEP 2 bar operating conditions, which are frequently used when evaluating the fuel consumption in passenger vehicles. At the lean-combustion operating point, $NO_2$ was produced during combustion and the ratio of $NO_2$ increased, while that of $N_2O$ decreased as the excess air ratio increased.

Effect of Pressure and Stoichiometric Air Ratio on NOx Emissions in Gas-Turbine Dump Combustor with Double Cone Burner (이중원추형 모형연소기에서 압력과 공기비에 따른 NOx 배출특성)

  • Nam, Dong-Hyun;Nam, Hyun-Su;Han, Dong-Sik;Kim, Gyu-Bo;Cho, Seung-Wan;Kim, Han-Suk;Jeon, Chung-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.3
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    • pp.251-257
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    • 2012
  • This work presents an experimental investigation of NOx emissions according to inlet air temperature (550-660 K), stoichiometric air ratio (${\lambda}$, 1.4-2.1), and elevated pressure (2-5 bar) in a High Press Combustor (HPC) equipped with a double cone burner, which was designed by Pusan Clean Coal Center (PC3). The exhaust-gas temperature and NOx emissions were measured at the end of the combustion chamber. The NOx emissions generally decreased as a function of increasing ${\lambda}$. On the other hand, NOx emissions were influenced by ${\lambda}$, inlet air temperature and pressure of the combustion chamber. In particular, when the inlet air temperature increased, the flammability limit was extended to leaner conditions. As a result, a higher adiabatic temperature and lower NOx emissions could be achieved under these operation conditions. The NOx emissions that were governed by thermal NOx were greatly increased under elevated pressures, and slightly increased at sufficiently low fuel concentrations (${\lambda}$ >1.8).

A Study on the Characteristic of Conversion Efficiency for Three-way Catalyst in Hydrogen-Natural Gas Blend Fueled Engine (수소-천연가스 혼합연료 엔진의 삼원촉매 전환효율 특성 연구)

  • Park, Cheol-Woong;Yi, Ui-Hyung;Kim, Chang-Gi;Lee, Janghee
    • Journal of the Korean Institute of Gas
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    • v.20 no.6
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    • pp.23-30
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    • 2016
  • The conventional natural gas engine realized lean combustion for the improved efficiency. However, in order to cope with exhaust gas regulations enforced gradually, the interest has shifted at the stoichiometric mixture combustion system. The stoichiometric mixture combustion method has the advantage of a three-way catalyst utilization whose purification efficiency is high, but the problem of thermal durability and the fuel economy remains as a challenge. Hydrogen-natural gas blend fuel (HCNG) can increase the rate of exhaust gas recirculation (EGR) because the hydrogen increases burning speed and lean flammability limit. The increase in the EGR rate can have a positive impact on heat resistance of the engine due to the decreased combustion temperature, and further can increase the compression ratio for efficient combustion. In this study, to minimize the exhaust emission developed HCNG engine with stoichiometric combustion method, developed three-way catalyst was applied to evaluate the conversion characteristics. The tests were carried out during the steady state and transient operating conditions, and the results were compared for both the conventional and proto-three-way catalyst of HCNG engine for city buses.

Dispersion Characteristics of Hydrogen Gas by the Effect of Leakage Hole Size in Enclosure Space (누출공 크기에 따른 밀폐공간 내 수소 가스의 확산 특성)

  • Choi, Jinwook;Li, Longnan;Park, Chul-Woo;Lee, Seong Hyuk;Kim, Daejoong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.5
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    • pp.26-35
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    • 2016
  • As a potential clean energy resource, the production and consumption of hydrogen gas are expected to gradually increase, so that hydrogen related studies are also increasing. The thermal and chemical properties of hydrogen result in its high flammability; in particular, there is a high risk if leaks occur within an enclosed space. In this study, we applied the computational fluid dynamics method to conduct a numerical study on the leakage behavior of hydrogen gas and compared these numerical study results with an experimental study. The leakage hole diameter was selected as an important parameter and the hydrogen gas dispersion behavior in an enclosed space was investigated through various analytical methods. Moreover, the flammable regions were investigated as a function of the leakage time and leakage hole size. We found that the growth rate of the flammable region increases rapidly with increasing leakage hole size. We also investigated the relation between the mass flow rate and the critical time when the hydrogen gas reaches the ceiling. The analysis of the monitoring points showed that the hydrogen gas dispersion behavior is isotropic and independent of the geometry. We found that the concentration of gas in an enclosed space is affected by both the leakage flow rate and amount of gas accumulated in the enclosure.