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## Homework Statement

Number of cylinders 4

Stroke cycle 4

running at 4400 rpm

Volume compression ratio 7.6:1

Cylinder diameter 78 mm

Stroke 105 mm

Brake Power 38 KW

Indicated Power 47.5 KW

Air consumption 21 kg/kg fuel

Fuel consumption 13.6 kg/l

Each kg of fuel releases 41800 kg of energy

Given R = 0.287 kJ/kgK

Find:

a. Mechanical efficiency

b. The mean effective pressure

c. The volumetric efficiency (refer to 101.3 kpa and 0 C)

d. Brake thermal efficiency

## The Attempt at a Solution

I think I solved for both parts a and d. I'll show them below.

I am however having a very hard time with parts b and c. Any help would be great.

a. Mechanical efficiency = (Brake Power / Indicated Power) x 100

= (38000 w / 47500 w) x 100

= 80 %

d. Brake thermal efficiency

Brake Thermal Efficiency = 3600 x Brake Power / Fuel consumption x calorific value

= 3600 x 38 KW / 13.6 kg/l x 41800 kg of energy

= 136800 / 568480

= 0.24 or 24%