A conventional spark-ignition engine operating with gasoline will not run smoothfy (due to incomplete combustion) with an equivalence ratio leaner than about = 0.8. It is desirable to extend the...

A conventional spark-ignition engine operating with gasoline will not run smoothfy (due to incomplete combustion) with an equivalence ratio leaner than about = 0.8. It is desirable to extend the smooth operating limit of the engine to leaner equivalence ratios so that at part-throttle operation (with intake pressure less than 1 atmosphere) the pumping work is reduced. Leaner than normal operation can k a~hie~ed by adding hydrogen gas (H,) to the mixture in the intake system. The addition of H, makes the fuel-air mixture easier to bum.

(a) The fuel composition with "mixed" fuel operation is H₂
+ C₈H₁₈--one mole of hydrogen to every mole of gasoline, which is assumed the same as is~octan~. What is the stoichiometric air/fuel ratio for the "mixed" fuel?

(b) The lower heating value of H₂
is 120 MJ/kg and for isooctane is 44.4 MJ/kg What is the heating value per kilogram of fuel mixture?

(c) Engine operation with isooctane and the mixed (H₂
+ C₈H₁₈) fuel is Compared in a particular engine at a part-load condition (brake mean effective pressure of 275 kPa and 1400 revfmin). You are given the following information about the engine operation:

Estimate approximately the inlet manifold pressure and the pumping mean effective pressure with (H₂
+ C₈H₁₈) fuel. Explain your method and assumptions clearly. Note that mechanical efficiency q, is defined as