1. INTERNAL COMBUSTION ENGINES LECTURER PROF.Dr. DEMIR BAYKA

2. EXHAUST EMISSIONS AND CONTROL EMISSIONS FROM SI ENGINES EMISSIONS FROM CI ENGINES CO 2 : 11.2 - 11.6 % CO 2 : 4 - 12 % CO : 0.2 - 4 (8) % CO : 100 - 2000 ppm HC : 3000 ppm (C 1 ) HC : 200 - 1500 ppm (C 1 ) NO X : 1000 - 5000 ppm NO X : 1000 - 3000 ppm O 2 : 0 - 3 % O 2 : 3 - 16 % S : 600 ppm OF MASS S : 0.5 % OF FUEL OF FUEL MASS SOOT : 0.2 - 0.5 % OF FUEL MASS (HIGHER IN OLDER ENGINES)

3. OTHER EMISSIONS FROM MOTOR VEHICLES : 1) PISTON BLOW-BY GASES [CONTAINS FUEL VAPOR (HC), OIL VAPOR (HC)] 2) FROM VENTS IN THE FUEL TANK [CONTAINS FUEL VAPOR (HC)] 3) CARBURETTOR : FUEL VAPOR

4. SI ENGINES

5. DEPOSITS ABSORB HC (b) COMBUSTION SI ENGINES

6. (c) EXPANSION SI ENGINES

8. LEAN MIXTURES GIVE LOW CO & HC CONCENTRATIONS AND MODERATE NO x CONCENTRATIONS

9. CI ENGINES NO x IS FORMED IN THE HIGH TEMPERATURE ZONES (CLOSE TO STOICHIOMETRIC REGIONS) SOOT FORMS IN THE RICH UNBURNED FUEL CONTAINING THE CORE OF THE FUEL SPRAYS. HC FORM AT THE QUENCH REGIONS AND LATEST INJECTION

10. QUIZ No: 17 2000 Liste the un-wanted emisions from diesel engines.

11. NO X FORMATION NO X ---> NO & NO 2 PREDOMINANT DUE TO OXIDATION OF NITROGEN (FROM MAINLY AIR AND PERHAPS FROM FUEL) THE FOLLOWING REACTIONS ARE CONSIDERED :

12. IS STRONGLY DEPENDANT ON TEMPERATURE NEAR SPARK PLUG AWAY FROM SPARK PLUG

13. CO FORMATION IN SI ENGINES IS VERY MUCH DEPENDENT ON AIR/FUEL RATIO AS THE MIXTURE BECOMES RICHER IT RISES STEEPLY DUE TO INCOMPLETE COMBUSTION CO FORMATION

14. THE EQUILIBRIUM REACTIONS “FREEZE” DURING EXPANSION AND SO CO CONCENTRATION IS HIGHER THAN THAT PREDICTED BY EQUILIBRIUM CALCULATIONS NEAR SPARK PLUG AWAY FROM SPARK PLUG

15. HC FORMATION DURING EXHAUST STROKE

16. HC FORMATION MAIN SOURCES 1) FLAME QUENCING AT THE WALLS 2) CREVICES 3) ABSORBTION AND DESORBTION IN ENGINE OIL 4) POOR COMBUSTION QUALITY 5) DEPOSITS ON COMBUSTION WALLS (ABSORBTION AND DESORBTION)

17. EXHAUST GAS TREATMENT 1. CATALYTIC CONVERTERS OXIDIZING(HC,CO) REDUCING (NO X ) THREE WAY CATALYSTS 2. THERMAL REACTORS (HC,CO) 3. TRAPS & FILTERS (PARTICULATES)

18. CATALYTIC CONVERTERS * REQUIRED EXHAUST GAS TEMPERATURE IS 250 - 400 C * CATALYTIC MATERIAL : NOBLE METALS * LARGE CONTACT SURFACE AREA 1) HONEYCOMB STRUCTURE 2) PELLETS * THERMAL INSULATION : CERAMIC MATERIAL

19. CATALYTIC CONVERTERS HONEYCOMB STRUCTURE No OF PASSAGEWAYS/cm 2 = 30 - 60 HONEYCOMB SIZE :  1/2 ENGINE DISPLACEMENT VOLUME

20. CATALYTIC CONVERTERS PELLET TYPE

21. CO & HC OXIDATION OXYGEN IS REQUIRED OXYGEN IS SUPPLIED IN THE EXHAUST GAS UP TO 5 % IN SI ENGINES UP TO 16 % IN CI ENGINES CATALYSTS NOBLE METAL (PLATINUM PALLADIUM) BASE METAL OXIDES CATALYTIC CONVERTERS

22. PHYSICAL STRUCTURE FINE DISPERSION OF NOBLE METALS OVER INERT SUPPORT (HIGHLY POROUS ALUMINA) OF 20  m THICKNESS PARTICLE SIZE : < 50 nm (50X10 -9 m)

23. CONVERSION EFFICIENCY

24. INCREASES WITH EXHAUST TEMPERATURE FROM 20 TO 100 % AS TEMPERATURE GOES UP FROM 250 TO 400 C

25. EFFECTIVENESS OF THE CATALYTIC FILTER DECREASES AS THE CATALYST IS DEGRADED BY : 1) POISONING (LEAD IN FUEL, PHOSPHORUS IN OIL) 2) SINTERING (HIGH TEMPERATURES) OTHER FACTORS THAT DECREASE THE EFFECTIVENESS : 1) HIGH CONCENTRATIONS OF CO & HC AT LOW TEMPERATURES 2) SO 3 - SO 2 -------------FORMATION OF H 2 SO 4

26. NO X REDUCTION THIS IS DONE BY USING CO AND H 2 IN THE PRESENCE OF A CATALYST CO & H 2 ARE AVAILABLE THROUGH RICH MIXTURE OPERATION (NH 3 MAY BE PRODUCED DURING REDUCTION) CATALYST MATERİAL : RUTHENIUM (Ru) RHODIUM (Rh)

27. THREE WAY CATALYTIC FILTERS THESE FİLTERS REQUIRE NEAR STOICHIOMETRIC MIXTURES THEY REQUIRE MULTIPOINT INJECTION SYSTEMS WITH OXYGEN SENSORS (LAMDA SENSORS) IN THE EXHAUST PIPE AND CLOSED FEEDBACK CONTROL OF THE AIR/FUEL RATIO IN A NARROW BAND (± 0.05) A REDUCTION AND OXIDATION FILTER ARE PLACED IN THE SAME HOUSING

28. PARTICULATE TRAP FILTER THESE FILTERS ARE EXPENSIVE AND DIFFICULT TO MAINTAIN