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Loic De Francqueville – One of the best experts on this subject based on the ideXlab platform.

  • LES prediction and analysis of knocking Combustion in a spark ignition engine
    Proceedings of the Combustion Institute, 2015
    Co-Authors: A Robert, Stéphane Richard, Olivier Colin, Lionel Martinez, Loic De Francqueville
    Abstract:

    Highly boosted spark ignition (SI) engines are more and more attractive for car manufacturers in terms of efficiency and CO2 emissions. However, thermodynamic conditions encountered in these engines promote the occurrence of abnormal Combustions like knock or super-knock, which are experimentally difficult to analyse due to the risks of engine damages. The Reynolds averaged Navier–Stokes (RANS) method mainly used in industry for piston engines is not the most appropriate as knock does not always affect the mean cycle captured by RANS. Using an accurate LES compressible code and improved versions of ECFM-LES (Extended Coherent Flame Model) and TKI (Tabulated Kinetics of Ignition) models allowing a full uncoupling of flame propagation and auto-ignition reaction rates, this work demonstrates for the first time that LES is able to describe quantitatively knocking Combustion in a realistic SI engine configuration. Contrary to previous studies (Fontanesi et al., 2013 [5]) (Lecocq et al., 2011 [4]), a quantified knock analysis is conducted based on a specific post-processing of both numerical and experimental data. LES is able to predict the in-cylinder pressure variability, the knock occurrence frequency and the mean knock onset crank angle for several spark timings. A 3D analysis also demonstrates that knock occurs at random locations, mainly at the exhaust valves side. Knock intensity is found proportional to the fresh gases mass burned by autoignition at low knock intensities, while an exponential increase at the highest intensities suggests the influence of additional factors like the knock location in the cylinder or complex behaviour of knocking Combustion.

Jun Deng – One of the best experts on this subject based on the ideXlab platform.

  • comparative analysis of thermokinetic behavior and gaseous products between first and second coal spontaneous Combustion
    Fuel, 2018
    Co-Authors: Yang Xiao, Jun Deng
    Abstract:

    Abstract To investigate the entire process of first and second coal spontaneous Combustion, a 15-t experimental furnace for coal spontaneous Combustion and synchronous thermal analyzer coupled with Fourier transform infrared spectroscopy were employed. The process of experimental tests was as follows: First, coal temperature was increased from 31.0 °C (room temperature) to 452.7 °C without intervention. Second, the coal sample was cooled to approximately 90.0 °C in an anaerobic atmosphere. Third, air was supplied until the sample reached 418.0 °C. Finally, the coal was cooled again to 100.0 °C in an anaerobic atmosphere. The variations of temperature, mass, heat energy intensity, and gaseous products were investigated. The results indicated that the temperature change rate first increased and then decreased during the first and second coal spontaneous Combustion. Compared with the first coal spontaneous Combustion, the rates of temperature and mass loss change with a heating rate of 2.5 °C/min were higher at the Combustion stage of the second coal spontaneous Combustion, but the variations of the exothermic reaction rate and mass loss with other heating rates (5.0, 10.0, and 15.0 °C/min) were lower. The differences among CO, CO2, alkanes, and alkenes during the first and second coal spontaneous Combustions were insignificant until 300.0 °C. However, the emission of CO and CO2 during the second coal spontaneous Combustion was significantly higher than during the first coal spontaneous Combustion, whereas the release of alkanes and alkenes was substantially weaker when the temperature was higher than 300.0 °C. Moreover, the amount of H2O during the first coal spontaneous Combustion was higher than that during the second coal spontaneous Combustion.

A Robert – One of the best experts on this subject based on the ideXlab platform.

  • LES prediction and analysis of knocking Combustion in a spark ignition engine
    Proceedings of the Combustion Institute, 2015
    Co-Authors: A Robert, Stéphane Richard, Olivier Colin, Lionel Martinez, Loic De Francqueville
    Abstract:

    Highly boosted spark ignition (SI) engines are more and more attractive for car manufacturers in terms of efficiency and CO2 emissions. However, thermodynamic conditions encountered in these engines promote the occurrence of abnormal Combustions like knock or super-knock, which are experimentally difficult to analyse due to the risks of engine damages. The Reynolds averaged Navier–Stokes (RANS) method mainly used in industry for piston engines is not the most appropriate as knock does not always affect the mean cycle captured by RANS. Using an accurate LES compressible code and improved versions of ECFM-LES (Extended Coherent Flame Model) and TKI (Tabulated Kinetics of Ignition) models allowing a full uncoupling of flame propagation and auto-ignition reaction rates, this work demonstrates for the first time that LES is able to describe quantitatively knocking Combustion in a realistic SI engine configuration. Contrary to previous studies (Fontanesi et al., 2013 [5]) (Lecocq et al., 2011 [4]), a quantified knock analysis is conducted based on a specific post-processing of both numerical and experimental data. LES is able to predict the in-cylinder pressure variability, the knock occurrence frequency and the mean knock onset crank angle for several spark timings. A 3D analysis also demonstrates that knock occurs at random locations, mainly at the exhaust valves side. Knock intensity is found proportional to the fresh gases mass burned by autoignition at low knock intensities, while an exponential increase at the highest intensities suggests the influence of additional factors like the knock location in the cylinder or complex behaviour of knocking Combustion.

Yang Xiao – One of the best experts on this subject based on the ideXlab platform.

  • comparative analysis of thermokinetic behavior and gaseous products between first and second coal spontaneous Combustion
    Fuel, 2018
    Co-Authors: Yang Xiao, Jun Deng
    Abstract:

    Abstract To investigate the entire process of first and second coal spontaneous Combustion, a 15-t experimental furnace for coal spontaneous Combustion and synchronous thermal analyzer coupled with Fourier transform infrared spectroscopy were employed. The process of experimental tests was as follows: First, coal temperature was increased from 31.0 °C (room temperature) to 452.7 °C without intervention. Second, the coal sample was cooled to approximately 90.0 °C in an anaerobic atmosphere. Third, air was supplied until the sample reached 418.0 °C. Finally, the coal was cooled again to 100.0 °C in an anaerobic atmosphere. The variations of temperature, mass, heat energy intensity, and gaseous products were investigated. The results indicated that the temperature change rate first increased and then decreased during the first and second coal spontaneous Combustion. Compared with the first coal spontaneous Combustion, the rates of temperature and mass loss change with a heating rate of 2.5 °C/min were higher at the Combustion stage of the second coal spontaneous Combustion, but the variations of the exothermic reaction rate and mass loss with other heating rates (5.0, 10.0, and 15.0 °C/min) were lower. The differences among CO, CO2, alkanes, and alkenes during the first and second coal spontaneous Combustions were insignificant until 300.0 °C. However, the emission of CO and CO2 during the second coal spontaneous Combustion was significantly higher than during the first coal spontaneous Combustion, whereas the release of alkanes and alkenes was substantially weaker when the temperature was higher than 300.0 °C. Moreover, the amount of H2O during the first coal spontaneous Combustion was higher than that during the second coal spontaneous Combustion.

Jian Li Zhao – One of the best experts on this subject based on the ideXlab platform.

  • thermogravimetric analysis of Combustion characteristics and kinetic parameters of pulverized coals in oxy fuel atmosphere
    Journal of Thermal Analysis and Calorimetry, 2009
    Co-Authors: Shengli Niu, Kuihua Han, Jian Li Zhao
    Abstract:

    Temperature programmed Combustions (TPC) of Yang-Quan anthracite, Liao-Cheng lean coal and Li-Yan bituminous coal in oxy-fuel atmosphere were conducted in a thermogravimetric analyzer and characteristic parameters were deduced from the TG-DTG curves. The results showed that Combustion got harder to progress as the coalification degree increasing. Within range of 40%, effect of heightening O2 concentration favored the Combustion process, but beyond this zone, the effect leveled off. The model-fitting mathematical approach was used to evaluated the kinetic triplet (f (α), E, A) through Coats–Redfern method. The calculation showed that D3-Jander was the proper reaction model and the evaluations of E and A validated the experimental results.