B. Tech (Sixth Semester) Examination Apr-May-2022
Subject: Turbo-Machinery
Brach: Mechanical Engineering
Time: three Hours
Max Marks: 20
Minimum Marks:
Note: Attempt all the questions. All questions carry equal marks. Use of steam table and
Mollier chart is permitted.
Q1
An impulse steam turbine is supplied with steam at 35 bar, 350°C, the condenser
pressure being 0.07 bar. The first stage of the turbine is velocity compounded with two
rings of moving blades separated by a ring fixed guide blades. The isentropic drop for
this stage is 1/4 of that for the whole turbine. The nozzle angle is 20° and the nozzle
efficiency is 88%. The mean blade velocity of both the moving rings of blades is 0.2 of
the velocity of steam leaving the nozzle. The exit blade angles for both fixed and moving
blades are 30° and the blade friction coefficient for all blades is 0.9. If the internal
efficiency of the turbine is 75%, calculate the efficiency of the first stage and the
percentage of the total power developed by the turbine in this stage.
Q2
Steam expands in a turbine from 40 bar,5000 C to 0.10 bar isentropically. Assuming ideal
conditions, determine the mean diameter of the wheel,if the turbine were of (i) Single
stage, (ii) Single 50% reaction stage,(iii) Four pressure stage,(iv) One two row Curtis
stage, and (v) Four 50% reaction stages. Take the nozzle angle as 16 0 and N as 3000
rpm.
Q3
Steam at 20 bar, 4000C expands in a steam turbine to 0.1 bar. There are four stages in
the turbine and the total enthalpy drop is divided equally among the stages. The stage
efficiency is 75% and it is the same in all the stages. Determine the inter stage pressures,
the reheat factor and the turbine internal efficiency.
Q4
Determine the specific work output , specific fuel consumption and cycle efficiency
for a simple cycle gas turbine with a free power turbine given the following
specification:
Compressor pressure ratio
12.0
Turbine inlet temperature
1350K
Isentropic efficiency of compressor
0.86
Isentropic efficiency of each turbine
0.89
Mechanical efficiency of each shaft
0.99
Combustion efficiency
0.99
Combustion chamber pressure loss
6% compressor delivery pressure
Exhaust pressure loss
0.03 bar
Ambient conditions, Pa , Ta
1 bar, 288 K
Q5
centrifugal compressor is required to deliver 8kg/s of air with a stagnation pressure ratio
of 4 rotating at 15000 rpm. The air enters the compressor at 25 0C and 1 bar. Assume that
the air enters axially with velocity of 145 m/s and the slip factor is 0.89. If the compressor
isentropic efficiency is 0.89, find the rise in stagnation temperature, impeller tip speed,
diameter, work input , and area at the impeller eye.