Question

A ideal petrol engine consume 0.063 gm of fuel to produce 0.97 kJ of work. The fuel produces 43756 kJ/kg of heat. Assume specific heat for air to be constant. What can be the required compression ratio?

• A. 5
• B. 6
• C. 4
• D. 3

Answer 1

The correct option is D 3

$Q_{supplied}=m_{fuel}\times C.V.offuel$

$=0.063\times {10}^{-3}\times 43756=2.7566kJ$

${\eta }_{thermal}=\frac{W_{net}}{Q_{supplied}}=\frac{0.97}{2.7566}=0.3518$

$\Rightarrow {\eta }_{thermal}=1-\frac{1}{(n{)}^{\gamma -1}}$

$0.3518=1-\frac{1}{(n{)}^{0.4}}$

$0.648=\frac{1}{(n{)}^{0.4}}$

$1.5429=(n{)}^{0.4}$

$\Rightarrow n=2.9569$

$\therefore$ Closest answer can be 'a' i..e n = 3