GATE 2025 AG – Question 52
A four-stroke diesel engine has 6.0 L displacement,2300 rpm,75% mechanical efficiency and 800 kPa indicated mean effective pressure. Brake-specific fuel consumption is 320 g/(h·kW),and fuel calorific value is 44.6 MJ/kg. Find fuel-equivalent power in kW, to two decimals.
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Correct answer: 273.00 to 274.00
Explanation
A four-stroke engine has one power cycle per two revolutions. Indicated power is $P_i=p_mV_dN/120=800000(.006)(2300)/120=92000$ W. Brake power is $.75(92)=69$ kW. Fuel consumption is $.320(69)=22.08$ kg/h. Fuel energy rate is $22.08(44.6)/3.6=\mathbf{273.55}$ kW. Mechanical efficiency must be applied before using brake-specific consumption.