期刊
JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING
卷 35, 期 -, 页码 1015-1024出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.jngse.2016.09.016
关键词
HCCI (homogeneous charge compression ignition); Exhaust gas recirculation (EGR); Boosting; Auto-ignition reactivity; Natural gas
资金
- Ministry of Education (MOE)
- National Research Foundation of Korea (NRF) through the Human Resource Training Project for Regional Innovation and the Industrial Strategic technology development program - Ministry of Trade, Industry & Energy (MI, Korea) [10053151]
- Korea Evaluation Institute of Industrial Technology (KEIT) [10053151] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
In this study we computationally investigate the effects of exhaust gas recirculation (EGR) and boosting to clarify the auto-ignition mechanisms of homogeneous charge compression ignition (HCCI) in naturalgas -fueled engines. CHEMKIN-PRO is used to perform the thermodynamic and chemical kinetics analysis. To set the boundaries of the operating range, intake air pressures are varied from naturally aspirated operation to boost pressure (0.3 MPa) and EGR ratios are varied from 0% to 50% at an equivalence ratio of cp = 0.4, intake air temperature of Tin = 430 K, and engine speed of 1200 rpm. Natural gas has a single stage heat release, which results in a high temperature heat release (HTHR). The HTHR is composed of two parts, the thermal ignition preparation and thermal ignition range, in which fuel series reactions, H2O2 loop reactions, and H2-O2 system reactions occur. The reaction paths and contribution ratios that occur within the transient temperature can be described by a contribution matrix. We found that when the EGR ratio is increased, auto-ignition is retarded with a longer duration of combustion. The absolute heat release rate (HRR), forward and reverse reaction rates of reactions, and transient temperature during the thermal ignition stage are decreased, as are misfires. When the intake air pressure is increased, the rates of important reactions also increase rapidly. The auto-ignition points are advanced by a crank angle degree (CAD) of 6. In the combined case of 50% EGR and 0.2 MPa boosting, all reactions are sped up and the absolute heat release rate (HRR) is higher than in the naturally-aspirated (NA) condition. However, R1 is extremely sensitive to intake air pressure. In the case of NA (no EGR and 0.1 MPa), auto ignition occurred at a higher temperature (approximately 40 K). The absolute HRR decreased while increasing the boost and EGR ratio, and the forward and reverse reaction rates of most reactions increased. (C) 2016 Elsevier B.V. All rights reserved.
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