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

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

3. The Real Growth Kernel to Flame

4. Description of Turbulent Flow in Engine Cylinder

5. Identification of Structures in Turbulent Cylinder Flow

6. 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

7. Ensemble Mean Velocity in Engine Cylinder During a Cycle

8. Structure of Turbulence in Engine Cylinder

9. Turbulent Flames of Methane- Air Mixtures

10. 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.

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

12. 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 iso-surfaces of vorticity and Laplacian
of pressure.
where, ω = ∇×u is the vorticity.

13. 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 1/60th 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.