2. Volumetric Efficiency of Engine P M V Subbarao Professor Mechanical Engineering Department Quantification of Filling & Emptying Effectiveness….

3. Computation of Intake Process : SI Engine A I R FUEL SI Engine

4. Instantaneous Heat Transfer During Intake Process

5. Total Mass of mixture inhaled during Intake Process A I R FUEL

6. Instantaneous mass flow Rate and Cumulate Mass

7. Computation of Exhaust Process : SI Engine Combustion Products Exhaust Stroke

9. Computation of Intake Process : CI Engine A I R CI Engine

10. Volumetric Efficiency : A Global Measure of Breathing Effectiveness Volumetric efficiency a measure of overall effectiveness of engine and its intake and exhaust system as a natural breathing system. Volumetric efficiency is defined as:

11. If the air density r a,0 is evaluated at inlet manifold conditions, the volumetric efficiency is a measure of breathing performance of the cylinder, inlet port and valve. If the air density r a,0 is evaluated at ambient conditions, the volumetric efficiency is a measure of overall intake and exhaust system and other engine features. The full load value of volumetric efficiency is a design feature of entire engine system.

12. Valve Lift in General (Design) Practice : Intake Valve The maximum valve lift is normally about 12% of the cylinder bore. Inlet valve opening typically occurs at 10 to 25 0 BTC. IVO should occur sufficiently before TC which leads to early fall in cylinder pressure during the intake stroke. IVC usually falls in the range 40 to 60 0 after BC. IVC should occur sufficiently after BC, to provide more time for cylinder filing under conditions where cylinder pressure is below the intake manifold pressure at BC. IVC one of the principal factors that determines the amount of air taken in high-speed engines.

13. Valve Lift in General (Design) Practice : Exhaust Valve EVO strongly effects the engine thermal efficiency, as it affects the effective expansion ratio. The goal of EVO is to reduce cylinder pressure to close to manifold pressure as soon as possible. EVC typically falls in the range 8 to 20 0 after TC. EVC regulates the quantity of exhaust gases that flow back into the combustion chamber in SI engines. It also regulates the amount of cylinder burned gases exhausted. EVC timing should occur sufficiently far after TC so that the cylinder pressure does not rise near the end of the exhaust stroke. Late EVC favors high power at the expense of low-speed torque and idle combustion quality.