Beijing Key Laboratory of New Energy Vehicle Powertrain Technology

Laboratory of, China

Beijing Key Laboratory of New Energy Vehicle Powertrain Technology

Laboratory of, China
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Liu J.,Beijing Jiaotong University | Liu J.,Beijing Key Laboratory of New Energy Vehicle Powertrain Technology | Zhang X.,Beijing Jiaotong University | Zhang X.,Beijing Key Laboratory of New Energy Vehicle Powertrain Technology | And 5 more authors.
Fuel | Year: 2015

A dual fuel combustion model comprising a modified turbulent flame speed closure (TFSC) model and a partially premix reactor model is developed and incorporated into the KIVA-3V code to simulate the combustion processes within the dual fuel engine. Numerical results are validated by the cylinder pressures, heat release rates and emissions of the corresponding experimental data. The effects of engine speeds on the combustion process of dual fuel engines are investigated and the spatial and temporal distributions of the in-cylinder temperature and pollutions are compared. The results reveal that most of the pilot fuel vapor remains within the bowl, and the combustion of the pilot fuel forms a high temperature region. Moreover, some of pilot fuel vapor enters the squish volume, and forms a high temperature region above the piston top. NO formation region follows the development of the high temperature field, which is generated by the combustion of the pilot diesel. At low engine speed, the piston crevices are largely responsible for the creation of the unburned CH4 emissions. However, at high engine speed, bulk gas partial oxidation in the cylinder center region is the major source of the CH4 emissions. The flame quench zone in the squish volume close to the cylinder walls is the main source of the CO emission at low engine speed. However, the bulk gas partial oxidation zone in the cylinder center region is the major source of the CO emission at high engine speed.


Liu J.,Beijing Jiaotong University | Liu J.,Beijing Key Laboratory of New Energy Vehicle Powertrain Technology | Zhang X.,Beijing Jiaotong University | Zhang X.,Beijing Key Laboratory of New Energy Vehicle Powertrain Technology | And 8 more authors.
International Journal of Hydrogen Energy | Year: 2015

In this study, the chemical, thermal and diffusion effects of H2 and CO addition on the characteristics of methane laminar flame are examined numerically by using the CHEMKIN 2.0 code with a modified GRI-Mech 3.0 mechanism. The results reveal that a better agreement between the measured and predicted laminar flame speed is obtained by using the modified mechanism. The effect of H2 addition to flame speed is mainly due to chemical effect at lean and stoichiometric conditions. However, with the addition of CO, around 75% of the increase in laminar flame speed is due to thermal effect. Soret diffusion of H have an obviously effect on laminar flame speed, lowing it around the peak segment. Furthermore, the combined Soret effect of H and H2 basically accounts for the total Soret diffusion effect. With the addition of H2 and CO, the lean flammability limit is extended to a leaner mixture at atmospheric pressure. A linear correlation between the laminar flame speed and the relative amount of H2 was found in tertiary CH4/CO/H2 mixtures. However, this linear correlation is undermined when CO mole fraction is over than 45%. © 2015 Hydrogen Energy Publications, LLC.

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