Question

Please answer all

PROBLEM 1

A three-litre four-stroke diesel engine develops 12 kW per m3 of free air inducted per minute. The volumetric efficiency is 82 % at 3600 rpm referred to atmospheric condition of 1 bar and 27 oC. A rotary compressor which is mechanically coupled to the engine is used to supercharge the engine. The pressure ratio and the isentropic efficiency of the compressor are 1.6 and 75 % respectively. Calculate the percentage increase in brake power due to supercharging. Assume mechanical efficiency of the engine to be 85 % and air intake to the cylinder to be at the pressure equal to delivery pressure from compressor and temperature equal to 5.6 less than the delivery temperature of the compressor. Also assume that cylinder contains volume of charge equal to swept volume.  

PROBLEM 2

A mechanically coupled supercharger is run by a four-stroke four-cylinder square diesel engine with a bore of 120 mm as per the arrangements in Figure Q2 overleaf. Air enters the compressor at 25 oC and the compressor pressure ratio is 1.7. From the compressor, the air is passed on to a cooler where 1250 kJ/min of heat is rejected. The air leaves the cooler at 67 oC. Some air from the compressor is bled after the cooler to supercharge the engine. The volumetric efficiency is 85 % based on intake manifold pressure and temperature. The other details about the engine are: bp is 55 kW, speed is 3500 rpm and mechanical efficiency m η is 85 %. The isentropic efficiency of the compressor is to be 85%. Determine

i. imep of the engine, in bar

ii. The actual air consumption rate of the engine, in kg/min

iii. The air handling capacity of the compressor, in kg/min

PROBLEM 3

A quality governed four-stoke, single cylinder gas engine has a bore of 146 mm and a stroke of 280 mm. At 475 rev/min and full load the net load on the friction brake is 433 N, and the torque arm is 0.45 m. The indicator diagram gives a net area of 578 mm2 and a length of 70 mm with a spring rating of 0.815 bar per mm.

Calculate the ip, bp, and mechanical efficiency.  

PROBLEM 4

A fuel mixture of 60 % by mass of methane and 40 % by mass of ethanol is burned completely with theoretical air. What is the mass flow rate of air if the mass flow rate of fuel is 10 kg/s?

PROBLEM 5

Propane gas (C3H8) is reacted with air such that the dry product gases are 11.5% CO2, 2.7% O2 and 0.7% CO.

a) What is the % theoretical air supplied?

b) What is the dew point temperature, if the total pressure of the products is 100 kPa

(selasi knust)

Answer 1

3rd question answer

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