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.