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15° © respectively. If 8.4m? of free air id delivered by the compressor at 70 bar per
minute and work done is minimum, calculate 1) L P and I P delivery pressure 2)
Ratio of cylinder volume and 3) Total indicated power, assume n= 1.2 (6)
a.Explain the working of roots blower and obtain the expression for its efficiency. (4)
b. An axial flow compressor draws air at 20°C and delivers at 50°C. Assuming 50%
reaction, calculate the velocity of flow if the blade velocity is 100m/s, Take work
factor as 0.85. Assume 01 = 100, Bi=40°. Also calculate the number of stages. (6)
A centrifugal compressor draws in air at temperature of 27°C running at 18000rpm. The
outer diameter of blade tip is 550mm, slip factor is 0.82, and isentropic total head
efficiency 150.76. Calculate i) the temperature rise of air passing through the compressor
ii) the static pressure ratio. Assume the velocities of air at inlet and outlet
is same. Take Cp =1.005kJ/kgK. (10)
a. What is meant by the term FAD in compressors? How FAD is found? (4)
b. Obtain an expression for minimum work to be done on a two-stage reciprocating
compressor with perfect intercooling. (6)
a. Explain the working of a screw compressor. Give their applications. (5)
b. A single acting reciprocating air compressor with air entering at 1087 and leaving at
Tbar following pv'*= constant. Free air delivered is 5.6m7/min and mean piston
speed is 150m/min. Take stroke to bore ratio of 1.3 and clearance volume to be 1/58
of swept volume per stroke. The suction temperature and pressure are atmospheric.
Determine i) the volumetric efficiency ii) Speed of rotation and iii) Stroke and bore.

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