a) Using engine efficiency and tailpipe emission trends, discuss briefly why Sl engines operate near stoichiometric charge conditions. 

b) How is SCR (selective catalytic reduction) different to LNT (lean NOx trap)? (5 marks) R 1.00 7 = 1.4

c) Using the thermal efficiency of Otto and Diesel cycles, briefly discuss why diesel engines usually have better fuel economy than petrol engines. 0.8 Diesel cycle o=1 Otto cycle) 

Transcribed Image Text:

1.0- = 1.4 0.8 Diesel cycle (Otto cycle) 0.6 0.4 Increasing load 0.2 1 5 13 17 21 25 Compression ratio.r, 1.0- = 1.4 0.8 Diesel cycle (Otto cycle) 0.6 0.4 Increasing load 0.2 1 5 13 17 21 25 Compression ratio.r,

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