1. Breathing abilities are limited by throat size….
Sizing of Valves
P M V Subbarao
Professor
Mechanical Engineering Department
Breathing abilities are limited by throat size….

2. The Driving Force for Flow Through Intake System

3. How to Size the Valves ????
Exhaust Pipe

4. Geometrical Nomenclature for Valves
The instantaneous valve flow area depends on valve lift and the geometrical details of the valve head, seat and stem.
There are three separate stages to the flow area development as valve lift increases.

5. Stages of Valve Lifting

6. Instantaneous minimum Available Flow area: Low Lift
For low lift valves, the minimum available flow area corresponds to a frustum of right circular cone.
The conical face between valve and seat is, perpendicular to the seat, defines the flow area.
The minimum area is:

7. Instantaneous minimum Available Flow area : Intermediate Lift
For the second stage, the minimum area is still the slant surface of a frustum of a right circular cone.
However, this surface is not perpendicular to the valve seat.
The base angle of the cone increases from (900-) toward that of a cylinder.
For this stage:
Dm is mean diameter of seat :

8. Instantaneous minimum Available Flow area : High Lift
When the valve lift is sufficiently large, the minimum flow area is no longer between the valve head and seat.
It is the port area minus the sectional area of the valve stem.
Then,

9. Valve Lift Vs Flow Area Curves

10. Stream Tube formed by Flow Through Valves
Equivalent Converging-Diverging Nozzle Configurations:
Mild Separation.
Severe Separation

11. Capacity of A Valve Passage
Mass flow rate through any cross section of area A