Numerical study on auto-ignition development and knocking characteristics of a downsized rotary engine under different inlet pressures

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.

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Numerical Study of Auto-Ignition and Combustion in Supersonic Hydrogen-Air Mixing Layer

Fluid Mechanics and Its Applications - IUTAM Symposium on Combustion in Supersonic Flows ◽

10.1007/978-94-011-5432-1_10 ◽

1997 ◽

pp. 119-134 ◽

Cited By ~ 2

Author(s):

A. Stoukov ◽

M. Gorokhovski ◽

D. Vandromme

Keyword(s):

Numerical Study ◽

Mixing Layer ◽

Auto Ignition ◽

Air Mixing ◽

Ignition And Combustion

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Combustion of Hydrogen Enriched Methane and Biogases Containing Hydrogen in a Controlled Auto-Ignition Engine

Applied Sciences ◽

10.3390/app8122667 ◽

2018 ◽

Vol 8 (12) ◽

pp. 2667

Author(s):

Antonio Mariani ◽

Andrea Unich ◽

Mario Minale

Keyword(s):

Equivalence Ratio ◽

Numerical Study ◽

Chemical Reactivity ◽

Combustion Process ◽

Pollutant Emissions ◽

Ignition Process ◽

Effective Pressure ◽

Indicated Mean Effective Pressure ◽

Auto Ignition ◽

Combustion Of Hydrogen

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.

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Numerical Study of Effect of Compression Ratio on Controlled Auto-Ignition Combustion

2013 International Conference on Computational and Information Sciences ◽

10.1109/iccis.2013.306 ◽

2013 ◽

Author(s):

Mingfei Xiao ◽

Jiansheng Lin ◽

Yusen Jin

Keyword(s):

Compression Ratio ◽

Numerical Study ◽

Auto Ignition

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Numerical Study on Flow Field in a Peripheral Ported Rotary Engine Under the Action of Apex Seal Leakage

Journal of Fluids Engineering ◽

10.1115/1.4049117 ◽

2020 ◽

Author(s):

Baowei Fan ◽

Yuanguang Wang ◽

Jianfeng Pan ◽

Yaoyuan Zhang ◽

Yonghao Zeng

Keyword(s):

Velocity Field ◽

Flow Field ◽

Combustion Chamber ◽

Numerical Study ◽

Particle Image Velocimetry Data ◽

Calculation Model ◽

Flow Area ◽

Rotary Engine ◽

Unidirectional Flow ◽

Rotary Engines

Abstract Apex seal leakage is one of the main defects restricting the performance improvement of rotary engines. The aim of this study is to study the airflow movement in a peripheral ported rotary engine under the action of apex seal leakage. For this purpose, a 3D dynamic calculation model considering apex seal leakage was firstly established and verified by particle image velocimetry data. Furthermore, based on the established 3D model, the flow field in the combustion chamber under the four apex seal leakage gaps (0.02, 0.04, 0.06 and 0.08 mms) and the three engine revolution speeds (2000, 3500, and 5000 RPMs) was calculated. By comparing with the flow field under the condition without leakage, the influences of the existence of apex seal leakage on the velocity field, the turbulent kinetic energy and the volumetric efficiency in the combustion chamber were investigated. Thereinto, the influences of the existence of apex seal leakage on the velocity field is that at the intake stroke, a vortex formed in the middle of the combustion chamber under the condition without apex seal leakage, was intensified by the apex seal leakage action. At the compression stroke, irrespective of the condition with or without apex seal leakage, all vortexes in the combustion chamber are gradually broken into a unidirectional flow. However, there is an obvious "leakage flow area" at the end of combustion chamber due to the existence of apex seal leakage.

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