Analysis of Turbulent Flame in SI Engine P

Analysis of Turbulent Flame in SI Engine P M V Subbarao Professor Mechanical Engineering Department Higher surface area flameswith least Volume…. .

Empirical Correlations to Select Combustion Parameters T in K & p in atm.

The Real Growth Kernel to Flame

Description of Turbulent Flow in Engine Cylinder

Identification of Structures in Turbulent Cylinder Flow

Quantitative Description of Turbulence • The instantaneous velocity U(q) in the cylinder at any crank angle q during a cycle i is expressed as: Where • • Where n is the number of strokes in an engine cycle, U(q) the phase averaged velocity. u(q, i) the fluctuating velocity. Similarly the turbulence intensity u' can be determined by

Ensemble Mean Velocity in Engine Cylinder During a Cycle

Structure of Turbulence in Engine Cylinder

Turbulent Flames of Methane- Air Mixtures

Damkohler’s Conjecture : 1940 • Damkohler intuitively identified two distinct limiting regimes: • A turbulent flame regime, where small size eddies interact with the transport mechanisms within the flame. • A turbulent flame regime, where large size eddies interact with thin flame.

Qualitative Description of Turbulent Flow : Lessons from Nature A Hurricane : THE VORTEX

Description of in Turbulent Flows The size of energy-containing (larger) eddies may be Estimated as: The Structure of Vortex The vortical structures visualized by isosurfaces of vorticity and Laplacian of pressure. where, ω = ∇×u is the vorticity.

Vortical Description of In-Cylinder Flow • A general engine flow, at middle third of the intake stroke has an intensity of roughly 10 ×Sp , where Sp , is the average piston speed. • The size of largest vortex is found to be roughly B/6 , where B is the bore. • This means that this vortex has cycle time of (a time scale) of roughly, B/ 60 ×Sp. • This time scale is 1/60 th of time it takes the piston to complete the intake stroke. • What is the use of this knowledge? • It tells us that there is a vortex which complete a one full period of mixing, in a time shorter than (about 1/60) the time of the intake stroke.