The structure of small-scale turbulence and its effect on combustion in spark ignition engines

摘要: Abstract This paper reviews measurement and analysis of mixture motion in internal combustion engines during the intake compression processes. Particular attention is paid to influence engine variables such as speed, load ratio, on flow field at or near inner (top) dead centre. The arbitrary procedures for defining a time varying “mean flow” each cycle are discussed. A spectral procedure, using Fourier transforms, proposed which may be employed estimate contribution turbulence parameters from cycle-to-cycle variations mean flow. Recent photographs taken turbulent spark ignition then provide useful insight into structure flame within engine, appear indicate existence coherent small scale structures, containing highly dissipative vortex tubes diameter η (the Kolmogorov microscale) with characteristic spacing λ Taylor microscale), by Tennekes. evidence seems support recent theories propagation based structure. model, relatively rapid along laminar burning between further developed. resulting model takes thickness reaction zone account does not include any specific empirical coefficients. After incorporation simple simulation analysis, predicted durations compared experimental data. It found that yields promising results. Finally, an analytical expression derived duration constant volume values velocity intensity process. For this case duration, Δθ, crank angle degrees given where, ƒ(p r ) function overall pressure ratio p2/p1 engine. u1⪡ ut', first term, approximately represents front travel across cylinder, almost independent speed simplified can readily used study design operating duration.