Fluid Mechanics Interview Questions with Answers For Mechanical Students
1. How Gravitation can be eliminated by Pump?
Cavitation means bubbles are forming in the liquid.
· To avoid Cavitation, we have to increase the Pump size to One or Two Inch;
To increase the pressure of the Suction Head, or
· Decrease the Pump Speed.
2. Types of pumps?
– Positive Displacement
– rotary lobe pump, progressive cavity pump, rotary gear pump, piston pump, diaphragm pump, screw pump, gear pump, Hydraulic pump, vane pump
– Centrifugal Pumps
– end suction pumps, in-line pumps, double suction pumps, vertical multistage pumps, horizontal multistage pumps, submersible pumps, self-priming pumps, axial-flow pumps, regenerative pumps.
3. Why Cavitation will occur in Centrifugal Pump and not in Displacement Pump?
The formation of cavities (or bubbles) is induced by flow separation, or non-uniform flow velocities, inside a pump casing. In centrifugal pumps the eye of the pump impeller is smaller than the flow area of pipe. This decrease in flow area of pump results in increase in flow rate. So pressure drop happened between pump suction and the vanes of the impeller. Here air bubbles or cavities are formed because of liquid vapour due to increase in temperature in impeller. This air bubbles are transmitted to pump which forms cavitation.
4.Which pump is more efficient Centrifugal pump or Reciprocating pump?
Because flow rate is higher compared to reciprocating pump. Flow is smooth and it requires less space to install. Lower initial
cost and lower maintenance cost.
5. What are two types of clearance in a turbine?
Radial – clearance at the tips of the rotor and casing.
Axial – the fore-and-aft clearance, at the sides of the rotor and the casing.
6. What is the function of a thrust bearing?
Thrust bearings keep the rotor in its correct axial position.
7. Pascal law ? Applications?
– Pascal’s law or the Principle of transmission of fluid-pressure states that “pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure ratio (initial difference) remains the same.
Application- Hydraulic jacks, Car lifts, Fork Lifts
8. Difference between single acting and double acting pump?
– In single-acting machines the compression takes place on only one side of the piston; double-acting machines use both sides of the cylinder for compression. The flow is continuous in double acting and in single acting the flow is not continuous unless there is a surge vessel.
9. What is a stage in a steam turbine?
In an impulse turbine, the stage is a set of moving blades behind the nozzle. In a reaction turbine, each row of blades is called a “stage.” A single Curtis stage may consist of two or more rows of moving blades.
10. What is a diaphragm?
Partitions between pressure stages in a turbine’s casing are called diaphragms. They hold the vane-shaped nozzles and seals between the stages. Usually labyrinth-type seals are used. One-half of the diaphragm is fitted into the top of the casing, the other half into the bottom.
11. What are the two basic types of steam turbines?
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