GATE Mechanical Engineering (ME) 2020 Shift 1 Solved Paper

Question : 57 of 65

Marks: +1, -0

The indicated power developed by an engine with compression ratio of 8, is calculated using an air-standard Otto cycle (constant properties). The rate of heat addition is

10 {kW}

. The ratio of specific heats at constant pressure and constant volume is

1.4

The mechanical efficiency of the engine is 80 per cent.
The brake power output of the engine is ________

{\kW}

(round off to one decimal place).

Your Answer:

Validate

Solution:

Thermal efficiency of Otto engine

=1-\;{1}/{(r)^{γ-1}}

Where,

r

is compression ratio

η=1-\;{1}/{(8)^{1.4-1}}

=0.5647=56.47 \%

η=\;{\;\text " I.P "\;}/{\;\text " Heat input "\;}

Indicated Power (I.P)

=η ×

Heat input

=0.5647 × 10=5.647 {kw}

Mechanical efficiency

(η_{ {m}})==\;{\;\text " Brakepowe (B.P.) "\;}/{\;\text " Indicated power (I.P.) "\;}

0.8=\;{B . P}/{5.647}

B.P.

=4.51 {kW}

Brake power is 4.51 kW.

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