Aspark ignition engine burns a fuel of calorific value 45mjkg. it compresses the air-ful mixture in accordance with pv^1.3=constant. the pressure developed in the cylinder during 30% and 70% of the compression stroke is 1.5 bar and 2.75 bar, respectively. the relative efficiency of the engine with respect to the air standard efficiency is 50%. determine the (i) compression ratio (ii) fuel consumption per hour per kw of power generated

i). Compression ratio = 3.678

ii). fuel consumption = 0.4947 kg/hr

Explanation:

Given  :

Fuel calorific value = 45 MJ/kg

We know, engine efficiency is given by,

where is compression ratio =

            =

where is compression volume

            is swept volume

Now it is given that swept volume at 30% of compression, 70% of the swept volume remains.

Then,

and at 70% compression, 30% of the swept volume remains

    ∴      

We know,

∴  

Therefore, compression ratio is = 3.678

Now efficiency,

  , this is the ideal efficiency

Therefore actual efficiency,

Therefore total power required = 1 kW x 3600 J

                                                    = 3600 kJ

∴ we know efficiency,

Therefore fuel required =

                                        = 0.4947 kg/hr      

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