Turbo Machinery (TM)

Q:   For a Pelton wheel with a given water jet velocity, the maximum output power from the Pelton wheel is obtained when the ratio of the bucket speed to the water jet speed is _______ (correct to two decimal places).

Q:   5 Steam flows through a nozzle at a mass flow rate of m=0.1 kg/s with a heat loss of 5 kW. The enthalpies at inlet and exit are 2500 kJ/kg and 2350 kJ/kg, respectively. Assuming negligible velocity at inlet (C1≈0), the velocity (C2) of steam (in m/s) at the nozzle exit is __________ (correct to two decimal places).

Q:   Select the correct statement for 50% reaction stage in a steam turbine.

• A:  The rotor blade is symmetric.
• B:  The stator blade is symmetric.
• C:  The absolute inlet flow angle is equal to absolute exit flow angle.
• D:  The absolute exit flow angle is equal to inlet angle of rotor blade.

Q:   A test is conducted on a one-fifth scale model of a Francis turbine under a head of 2 m and volumetric flow rate of 1 m³/s at 450 rpm. Take the water density and the acceleration due to gravity as103 kg/m³ and 10 m/s² , respectively. Assume no losses both in model and prototype turbines. The power (in MW) of a full sized turbine while working under a head of 30 m is _______ (correct to two decimal places).

Q:   Which one of the following statements is TRUE?

• A:  Both Pelton and Francis turbines are impulse turbines.
• B:  Francis turbine is a reaction turbine but Kaplan turbine is an impulse turbine.
• C:  Francis turbine is an axial-flow reaction turbine.
• D:  Kaplan turbine is an axial-flow reaction turbine.

Q:   The blade and fluid velocities for an axial turbine are as shown in the figure.
The magnitude of absolute velocity at entry is 300 m/s at an angle of 65^∘ to the axial direction, while the magnitude of the absolute velocity at exit is 150 m/s. The exit velocity vector has a component in the downward direction. Given that the axial (horizontal) velocity is the same at entry and exit, the specific work (in kJ/kg) is__________

Q:   Steam at a velocity of 10 m/s enters the impulse turbine stage with symmetrical blading having blade angle 30°. The enthalpy drop in the stage is 100 kJ. The nozzle angle is 20°. The maximum blade efficiency (in percent) is _______

Q:   At the inlet of an axial impulse turbine rotor, the blade linear speed is 25 m/s, the magnitude of absolute velocity is 100 m/s and the angle between them is 25°. The relative velocity and the axial component of velocity remain the same between the inlet and outlet of the blades. The blade inlet and outlet velocity triangles are shown in the figure. Assuming no losses, the specific work (in J/kg) is _______

Q:   Kaplan water turbine is commonly used when the flow through its runner is

• A:  axial and the head available is more than 100 m
• B:  axial and the head available is less than 10 m
• C:  radial and the head available is more than 100 m
• D:  mixed and the head available is about 50 m

Q:   In order to have maximum power from a Pelton turbine, the bucket speed must be

• A:  equal to the jet speed.
• B:  equal to half of the jet speed.
• C:  equal to twice the jet speed.
• D:  independent of the jet speed.