2. Influence of Design & Operational Parameters on Volumetric Efficiency of Engine P M V Subbarao Professor Mechanical Engineering Department Clues to Improve Filling & Emptying Effectiveness….

3. Variables Effecting Volumetric Efficiency Overall volumetric efficiency is affected by following variables. Intake and exhaust manifold and port design. Intake and exhaust valve geometry: size, lift and timings. Fuel type, fuel/air ratio, fraction of fuel vaporized in the intake system, and fuel enthalpy of vaporization. In-cylinder mixture temperature, as influenced by heat transfer with cylinder wall. Ratio of exhaust to inlet manifold pressures. Compression ratio. Engine speed. The effects of many of above variables are quasi-steady in nature. Their impact is either independent of speed or adequately function of speed.

4. “ When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it in numbers, your knowledge is of a meagre and unsatisfactory kind... ”. -- Lord Kelvin

5. Experimental Analysis of Valve Geometry

6. Pseudo Flow Velocity Pseudo Flow Velocity is a parameter to study the effect of manifold geometry, valve geometry and the rate change of cylinder volume on air flow into cylinder. PFV is proportional to the ratio of rate of change of cylinder volume to instantaneous minimum valve flow area.

7. Intake System Geometry Vs Volumetric Efficiency

8. Compression Ignition Speed Vs Volumetric Efficiency CI Engine SI Engine

9. Dwell Piston Mechanism The design geometry creates a pause or dwell in the piston’s movement at the TDC and the BDC, while the crank continues to rotate for up to 20 degrees.

10. Instantaneous Displacement & Velocity of Dwell Piston

11. Piston path for Dwell four stroke cycle

12. Comparison of standard and Dwell four stroke Cycles

13. SI Engine PV diagram due piston dwell in TDC and BDC

14. Comparison of standard and Dwell four stroke cycles in PV diagram

15. Influence of Dwell on volumetric efficiency

16. Selection of Valve Timing for Better Flow

17. Selection of Maximum Valve Lift

18. Selection of Maximum Lift & Valve timings

19. Flow Kinematics through Valves

20. Valve Timing for Better Flow

21. Thermodynamic Parameters Vs Volumetric Efficiency The volumetric efficiency is a function of Intake mixture pressure p i. Intake mixture Temperature T i. Fuel/ air ratio (F/A). Compression ratio r. Exhaust pressure, p e. Where m is the mass in the cylinder at the end of intake stroke.

22. Effect of Fuel composition, Phase & Fuel/air Ratio In a SI engine, the presence of gaseous fuel and moisture in the intake system reduces the air partial pressure below the mixture pressure. For a mixture:

23. Fuel Chemistry Vs Volumetric Efficiency P a,I /p i 1.0 0.6 Equivalence Ratio 0 1.5 H2H2 CH 4 C 8 H 18

24. Compression Ratio Vs Volumetric Efficiency