scholarly journals Numerical Study of Radical Reaction in Kerosene Auto-ignition

Author(s):  
Lan Li ◽  
Qi-sheng Chen
Fuel ◽  
2022 ◽  
Vol 309 ◽  
pp. 122046
Author(s):  
Run Zou ◽  
Jinxiang Liu ◽  
Huichao Jiao ◽  
Nana Wang ◽  
Jingjing Zhao

2018 ◽  
Vol 20 (7) ◽  
pp. 734-745 ◽  
Author(s):  
Anthony Robert ◽  
Jean-Marc Zaccardi ◽  
Cécilia Dul ◽  
Ahmed Guerouani ◽  
Jordan Rudloff

Two main abnormal combustions are observed in spark-ignition engines: knock and low-speed pre-ignition. Controlling these abnormal processes requires understanding how auto-ignition is triggered at the “hot spot” but also how it propagates inside the combustion chamber. The original theory regarding the auto-ignition propagation modes was defined by Zeldovich and developed by Bradley who highlighted different modes by considering various hot spot characteristics and thermodynamic conditions around the hot spot. Two dimensionless parameters ( ε, ξ) were then defined to classify these modes and a so-called detonation peninsula was obtained for H2–CO–air mixtures. Similar simulations as those performed by Bradley et al. are undertaken to check the relevancy of the original detonation peninsula when considering realistic fuels used in modern gasoline engines. First, chemical kinetics calculations in homogeneous reactor are performed to determine the auto-ignition delay time τi, and the excitation time τe of E10–air mixtures in various conditions. These calculations are performed for a Research Octane Number (RON 95) toluene reference fuel surrogate with 42.8% isooctane, 13.7% n-heptane, 43.5% toluene, and using the Lawrence Livermore National Laboratory (LLNL) kinetic mechanism considering 1388 species and 5935 reactions. Results point out that H2–CO–air mixtures are much more reactive than E10–air mixtures featuring much lower excitation times τe. The resulting maximal hot spot reactivity ε is thus limited which also restrains the use of the detonation peninsula for the analysis of practical occurrences of auto-ignition in gasoline engines. The tabulated ( τi, τe) values are then used to perform one-dimensional Large Eddy Simulations (LES) of auto-ignition propagation considering different hot spots and thermodynamic conditions around them. The detailed analysis of the coupling conditions between the reaction and pressure waves shows thus that the different propagation modes can appear with gasoline, and that the original detonation peninsula can be reproduced, confirming for the first time that the propagation mode can be well defined by the two non-dimensional parameters for more realistic fuels.


2018 ◽  
Vol 8 (12) ◽  
pp. 2667
Author(s):  
Antonio Mariani ◽  
Andrea Unich ◽  
Mario Minale

The paper describes a numerical study of the combustion of hydrogen enriched methane and biogases containing hydrogen in a Controlled Auto Ignition engine (CAI). A single cylinder CAI engine is modelled with Chemkin to predict engine performance, comparing the fuels in terms of indicated mean effective pressure, engine efficiency, and pollutant emissions. The effects of hydrogen and carbon dioxide on the combustion process are evaluated using the GRI-Mech 3.0 detailed radical chain reactions mechanism. A parametric study, performed by varying the temperature at the start of compression and the equivalence ratio, allows evaluating the temperature requirements for all fuels; moreover, the effect of hydrogen enrichment on the auto-ignition process is investigated. The results show that, at constant initial temperature, hydrogen promotes the ignition, which then occurs earlier, as a consequence of higher chemical reactivity. At a fixed indicated mean effective pressure, hydrogen presence shifts the operating range towards lower initial gas temperature and lower equivalence ratio and reduces NOx emissions. Such reduction, somewhat counter-intuitive if compared with similar studies on spark-ignition engines, is the result of operating the engine at lower initial gas temperatures.


2009 ◽  
Vol 83 (3) ◽  
pp. 407-423 ◽  
Author(s):  
W. P. Jones ◽  
S. Navarro-Martinez

2019 ◽  
Vol 200 ◽  
pp. 112092 ◽  
Author(s):  
Yongxiang Zhang ◽  
Jianqin Fu ◽  
Jun Shu ◽  
Mingke Xie ◽  
Jingping Liu ◽  
...  

2019 ◽  
Vol 21 (1) ◽  
pp. 101-121 ◽  
Author(s):  
Jose M Desantes ◽  
Jose M Garcia-Oliver ◽  
Ricardo Novella ◽  
Leonardo Pachano

The role of nozzle diameter on diesel combustion is studied by performing computational fluid dynamics calculations of Spray A and Spray D from the Engine Combustion Network. These are well-characterized single-hole sprays in a quiescent environment chamber with thermodynamic conditions representative of modern diesel engines. First, the inert spray evolution is described with the inclusion of the concept of mixing trajectories and local residence time into the analysis. Such concepts enable the quantification of the mixing rate, showing that it decreases with the increase in nozzle diameter. In a second step, the reacting spray evolution is studied focusing on the local heat release rate distribution during the auto-ignition sequence and the quasi-steady state. The capability of a well-mixed-based and a flamelet-based combustion model to predict diesel combustion is also assessed. On one hand, results show that turbulence–chemistry interaction has a profound effect on the description of the reacting spray evolution. On the other hand, the mixing rate, characterized in terms of the local residence time, drives the main changes introduced by the increase of the nozzle diameter when comparing Spray A and Spray D.


2021 ◽  
pp. 146808742110601
Author(s):  
Magnus Kircher ◽  
Emmeram Meindl ◽  
Christian Hasse

A combined experimental and numerical study is conducted on knocking combustion in turbocharged direct-injection spark-ignition engines. The experimental study is based on parameter variations in the intake-manifold temperature and pressure, as well as the air-fuel equivalence ratio. The transition between knocking and non-knocking operating conditions is studied by conducting a spark timing sweep for each operating parameter. By correlating combustion and global knock quantities, the global knock trends of the mean cycles are identified. Further insight is gained by a detailed analysis based on single cycles. The extensive experimental data is then used as an input to support numerical investigations. Based on 0D knock modeling, the global knock trends are investigated for all operation points. Taking into consideration the influence of nitric oxide on auto-ignition significantly improves the knock model prediction. Additionally, the origin of the observed cyclic variability of knock is investigated. The crank angle at knock onset in 1000 consecutive single cycles is determined using a multi-cycle 0D knock simulation based on detailed single-cycle experimental data. The overall trend is captured well by the simulation, while fluctuations are underpredicted. As one potential reason for the remaining differences of the 0D model predictions local phenomena are investigated. Therefore, 3D CFD simulations of selected operating points are performed to explore local inhomogeneities in the mixture fraction and temperature. The previously developed generalized Knock Integral Method (gKIM), which considers the detailed kinetics and turbulence-chemistry interaction of an ignition progress variable, is improved and applied. The determined influence of spark timing on the mean crank angle at knock onset agrees well with experimental data. In addition, spatially resolved information on the expected position of auto-ignition is analyzed to investigate causes of knocking combustion.


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