Turbocharging of I.C. Engines

1. Turbocharging of I.C. Engines P M V Subbarao Professor Mechanical Engineering Department Going for Artificially Breathing Engines….

2. A Turbocharged Engine The Primary Objective:

3. Matching of Turbocharger with Engine • I.C. Engines are semi-control volumes. • Can accept or deliver flow across the boundary intermittently. • Turbocharger is a combination of two pure control volumes. • They need to continuously accept and deliver flow across boundary. • Demands a special engineering art called as tuning. • An art of tuning CVs with CM. • Fluid Dynamic Turning. • Thermodynamic Tuning.

4. Turbocharger Turbine :A device to utilize waste microscopic kinetic energy of exhaust gasr. Compressor :A device to increase microscopic kinetic energy of intake air.

5. Practical Implementation of Duty of A Compressor

6. Thermo-fluid Dynamics of Impeller Radial Flow Impeller Mixed Flow Impeller

7. Flow Through Compressor

8. Gas Dynamics of An Impeller re ri

9. pce pi T0ce=T0e pe p0i T01 Thermodynamic View of an isentropic Compressor Only Impeller can consume Power !!! p0ce=p0e Only Impeller can consume Power !!! T s

10. Power Input to An Irreversible Impeller Power input factor, y Typical values for the power input factor, y : 1.035 – 1.11.

11. p0ce=p0e Impeller Losses Overall Losses T0es=T0e p0i T0i Irreversible Compressor T s

12. Work consumed by A compressor = Increase in Stagnation Enthalpy of gas For an irreversible compressor of given pressure rise, the actual temperature rise is more than isentropic temperature rise. Define, isentropic Efficiency of A Compressor:

13. ce ti Engine Pti, Tti pce, Tce i Т C te pi, Ti Pte, Tte The Problem of Fluid Dynamic Tuning

14. Turbocharged engine with Reservoirs

15. Thermodynamic Tuning B C Engine Pc, Tc Pb, Tb A Т C D Pa, Ta Pd, Td

16. Compressor Sizing • A compressor is sized based on two pieces of information, boost pressure and airflow. • The minimum boost pressure needed to achieve the required volumetric efficiency is to be evaluated. • The airflow is directly related to the engine speed and is thus calculated based on what part of the speed range is desired to experience a power increase. • Once the boost pressure and airflow are known, they are used to size the compressor. • A compressor works best at a particular combination of airflow and boost pressure.

17. A comparison of this optimal combination of boost pressure and airflow for a given compressor to the Engine anticipated combination of boost pressure and airflow determines the suitability of the compressor for the system. The First Law of Tuning

18. Three constraints on Compressor Sizing • Generation of required Boost Pressure (ratio). • Isentropic efficiency must be better than 60%. • Mass flow rate must be higher than average engine mass flow rate at Full load. • Flexible parameters: • Compressor geometry : radial to Mixed. • Compressor Speed : low to high.

19. Engineering Shape of A Compressor 130000rpm 120000rpm 105000rpm 90000rpm 75000rpm 65000rpm

20. Engine in the House of Compressor

21. The Power needs of Compressor

22. ce ti Engine Pti, Tti pce, Tce i Т C te pi, Ti Pte, Tte The Turbine to Drive the Compressor

23. Irreversible Adiabatic Flow Through Turbine : SSSF ti h teactual teiso s Ideal work wiso = h0ti –h0teiso Actual work wact = h0ti – h0teact Internal Efficiency of a turbine

24. Thermodynamics of Turbine Sizing

25. Turbine Sizing • The selection of the turbine size is a bit simpler than the sizing of the compressor. • Important to note that the turbine size effects boost threshold, turbo lag and fuel consumption . • Boost threshold is the engine speed at which there is sufficient exhaust gas flow to generate positive (intake) manifold pressure, or boost. • This is the time between the demand for an increase in power and the turbocharger(s) providing increased intake pressure, and hence increased power. • The selection is basically just a balancing act. • There are no complicated maps or processes used to select the turbine size.