1. Design of Intake Systems for better in-cylinder Turbulent Flow
P M V Subbarao
Professor
Mechanical Engineering Department
Introduce and Control Organized Turbulence …..
A Task unlikely to be completed in the near future ?!?!

2. A Segment of Reconstructed Turbulent Flame

3. Influence of turbulent scale & Intensity on minimum ignition energy

4. Intelligence in Engine Turbulence

5. Large Scales: Parents Vortices

6. Quick Combustion with Fuel Economy
To promote quick combustion, sufficient large-scale turbulence is needed at the end of the compression stroke.
Large scales of turbulence will result in a better mixing process of air and fuel and it will also enhance flame development.
Too much turbulence leads to excessive heat transfer from the gases to the cylinder walls, and may create problems of flame propagation .
The key to efficient combustion is to have enough turbulence in the combustion chamber prior to ignition.
This turbulence can be created by the design of the intake port

7. Schematic diagram of the experimental setup

8. Types of Intake Flows
There are two types of structural turbulence that are recognizable in an engine; tumbling and swirl.
Both are created during the intake stroke.
Tumble is defined as the in-cylinder flow that is rotating around an axis perpendicular with the cylinder axis.
Swirl is defined as the charge that rotates concentrically about the axis of the cylinder.

9. Tumble Motion
For most of the modern stratified charge and direct injection SI engines, tumble flows are more crucial than the swirl flows.
Tumble flow generates proper mixing of air and fuel, and for high flame propagation rate.
Also a well defined (single vortex) tumbling flow structure is more stable.
TR is defined as the ratio of the mean angular velocity of the vortices on the target plane to the average angular velocity of the crank.
The negative or positive magnitudes of TR indicate the direction of the overall in-cylinder tumble flow in a given plane as CW or CCW respectively.

10. The ensemble average velocity vectors during intake stroke : Flat Piston

11. Variation of tumble ratio with crank angle positions at various engine speeds

12. Pentroof Pistons

13. Variation of tumble ratio with crank angle positions

14. Valve Geometry Vs Turbulence

15. Control of Turbulence Level

16. Turbulence Level versus engine speed

17. Control of Integral Scale

18. Integral Scale Vs Speed

19. Variation of turbulent intensity with volumetric

20. Tumble based Injection systems
P M V Subbarao
Mechanical Engineering,
IIT Delhi
Tumble based Injection systems

21. Generation of Swirl during Induction
Deflector Wall Port
Shallow-Ramp Helical Port
Directed port
Steep-Ramp Helical Port

28. Measures of Swirl
Two different values are calculated to assess the swirl intensity.
Swirl number or swirl coefficient and swirl component or swirl number.
The first, the swirl number, is the ratio of angular momentum to the axial momentum:
This angular momentum is calculated in the centre of the swirl (not on the cylinder axis).

29. Selection of Valve Lift & Valve Geometry
Plain Directed
Shallow Ramp Helical
Steep Ramp Helical

30. The other is herein called the “swirl component” and is the swirl parameter relevant for experimental tests with a paddle wheel placed in the axis of the cylinder:

31. Swirl Generation through Valve Seat

32. Pistons for Swirl based systems