turbomachines

Q1    Define Turbomachines. Classify turbo machines. Derive the Euler’s expression for turbo machinery.

Q2    Derive the polytropic compression efficiency through an infinitesimal compression stage.

Q3    Using buckingham π theorem show that the discharge of a centrifugal pump can be expressed as   Q=ND³ φ [ND/(gH)^1/2 , ND² /ν].

Q4    How do you differentiate between impulse and reaction turbine ? In a single stage impulse turbine the nozzle discharges the fluid on to the blades at an angle of 65⁰ to the axial direction and the fluid leaves the blades with absolute velocity of 300m/s at the angle of 30⁰ to the axial direction. If the blades have equal inlet and outlet angles and there is no axial thrust, estimate the blade angle, power produce per kg/s of fluid and blade efficiency.

Q5    With the help of neat sketches, explain all the components of a centrifugal pump. Also explain NPSH and Priming in a pump.

Q6    Explain a single stage velocity triangle with a neat sketch and derive an expression for blade efficiency.

Q7    Explain the following with expressions and figures.

   (1). Zero percent reaction stage

    (2). Fifty percent reaction stage, and

    (3). Hundred percent reaction stage.

Q8    Explain the phenomenon of surging, rotating stall and choking for centrifugal compressor.

Q9    Define degree of reaction for axial flow compressor and explain its importance. Prove that for 50% degree of reaction

Tanβ₁+tanβ₂=U/Ca.

Q10    What is similitude ? What are different types of similarities between the model and its prototype?

Q11    A model of Kaplan turbine , one tenth of actual size is tested under a head of 5m when actual head for prototype is 8.5m, the power to be developed by prototype is 9000kW. When running at 120 rpm at an overall efficiency of 85%, determine (a) speed,                   (b) Discharge and (c) Power of the model.

Q12    A centrifugal blower takes in air at 100KPa and 309K. it develops a pressure head of 750mm while consuming a power of 33 kW. If the blower efficiency is 80 % and mechanical efficiency is 86 %, determine the mass flow rate , volume flow rate and exit properties of air.

Q13    What is free vortex blade? Derive the work done and reaction ratio for a free vortex blade.

Q14    What do you understand by characteristic curves of a pump? What is the significane of the characteristic curve?

Q15    An impeller of a centrifugal pump having internal and external diameter are 150 mm and 300 mm respectively. The vane angles of impeller at inlet and outlet are 20⁰ and 30⁰ . the pump is running at 1300 rpm. The water enters the impeller radially and velocity of flow is constant. Determine the work done by impeller per unit weight of water.

Q16    The stroke and bore of a cylinder reciprocally engine running at 70 rpm are 500mm and 250 mm repectively. The 20 m long delivery pipe has a diameter of 80 mm. Determine the power saved by installing a vessel in delivery pipe, if pipe friction is 0.008.

Q17    Derive an expression to obtain the work done by axial flow pump on fluid.

Q18    A multistage gas turbine is to be designed with impulse stages and is to operate with an inlet pressure and temperature of 6 bar and 900 K and an outlet pressure of 1 bar. The isentropic efficiency of the turbine is 85%. All the stages are to have a nozzle outlet angle of 75⁰ and equal outlet and inlet blade angles. Mean blade speed of 250 m/s and equal inlet and outlet gas velocities. Estimate the max. number of stages required. Assume Cp= 1.15 KJ/Kg-K. γ=1.333 and optimum blade speed ratio.