Bissoy.com
Doctors Medicines MCQs Q&A

Consider the following statements: 1. The distinguishing features of a radial flow reaction turbine are – (i) only a part of the total head of water is converted into velocity head before it reaches the runner and (ii) the flow through water completely fills all the passages in the runner. 2. Kaplan turbine is essentially a propeller working in reverse, and its blades are so mounted that all the blade angles can be adjusted simultaneously by means of suitable gearing even as the machine is in operation 3. A draft tube is pipe of gradually increasing cross-sectional area which must be airtight, and under all conditions of operation, its lower end must be submerged below the level of the discharged water in the tailrace. Which of the above statements are correct? 

Consider the following statements: 1. The distinguishing features of a radial flow reaction turbine are – (i) only a part of the total head of water is converted into velocity head before it reaches the runner and (ii) the flow through water completely fills all the passages in the runner. 2. Kaplan turbine is essentially a propeller working in reverse, and its blades are so mounted that all the blade angles can be adjusted simultaneously by means of suitable gearing even as the machine is in operation 3. A draft tube is pipe of gradually increasing cross-sectional area which must be airtight, and under all conditions of operation, its lower end must be submerged below the level of the discharged water in the tailrace. Which of the above statements are correct?  Correct Answer 1, 2 and 3

Reaction Turbine:

  • The principal feature of a reaction turbine that distinguishes it from an impulse turbine is that only a part of the total head available at the inlet to the turbine is converted to velocity head, before the runner is reached.
  • Also, in the reaction turbines the working fluid, instead of engaging only one or two blades, completely fills the passages in the runner.
  • The pressure or static head of the fluid changes gradually as it passes through the runner along with the change in its kinetic energy based on absolute velocity due to the impulse action between the fluid and the runner.
  • The pressure at the exit of the runner of a reaction turbine is generally less than atmospheric pressure, so the water at exit cannot be directly discharged to the tail race. The draft tube is a conduit which connects the runner exit to the tail race. The primary function of the draft tube is to reduce the velocity of the discharged water to minimize the loss of kinetic energy at the outlet. This permits the turbine to be set above the tail water without any appreciable drop of available head.

 

Axial flow reaction turbine:

An axial flow turbine is a turbine in which the water flows parallel to the axis of the rotation of the shaft.

A reaction turbine is a turbine in which the head at the inlet is sum of the pressure energy and kinetic energy and during the flow of water through the runner a part of pressure energy is converted into kinetic energy.

The shaft of the turbine is vertical in axial flow reaction turbine.

There are two important types of axial flow reaction turbine:

1. Kaplan Turbine:

When the vanes on the hub are adjustable, then the turbine is known as Kaplan turbine.

2. Propeller Turbine:

When the vanes on the hub are not adjustable, then the turbine is known as propeller turbine.

 

Draft Tube: The draft tube is a conduit that connects the runner exit to the tailrace where the water is being finally discharged from the turbine. It is used with reaction turbines only.

The draft tube has two purposes as follows

i) It permits a negative or suction head to be established at the runner exit, thus making it possible to install the turbine above the tailrace level without loss head.

ii) It converts a large proportion of velocity energy rejected from the runner into useful pressure energy.

A draft tube is made divergent so as to reduce the velocity at the outlet to a minimum. Therefore, a draft tube is basically a diffuser and should be designed properly with the angle between the walls of the tube to be limited to about 8 degrees so as to prevent the flow separation from the wall and to reduce accordingly the loss of energy in the tube.

[ alt="F1 S.S Madhu 10.01.20 D8" src="https://storage.googleapis.com/tb-img/production/20/01/F1_S.S_Madhu_10.01.20_D8.png" style="width: 310px; height: 231px;">

Related Questions

Consider the following statements in connection with hydraulic turbines: 1. The Kaplan turbine is a radial flow turbine in which the guide vane angles as well as the runner vane angles are adjustable. 2. Francis and Kaplan turbines are provided with draft tubes which carry water from exit of runner to tail water to increase the gross head across the turbine. 3. The parts of turbines susceptible to cavitation are the guide vanes and runner vanes – drastically reducing the turbine efficiency. 4. The specific speed of a 4-jet Pelton turbine will be 28 if the specific speed of a single-jet Pelton turbine is 14. Which of the above statements are correct?
In the following question, two statements are numbered as A and B. On solving these statements, we get quantities A and B respectively. Solve both quantities and choose the correct option. Quantity A: Pipe A takes thrice the time taken by Pipe B to fill a tank. Together they can fill the tank in 15 hours, tank A and B is opened together for 4 hours and then Pipe A is closed and after 2 more hours Pipe B is closed and an outlet Pipe C is opened which when working alone can empty the tank in 10 hours. Calculate the time taken by C to empty the tank. Quantity B: A pipe A can fill the tank in 10 hours another pipe B can fill the tank in 15 hours and with the help of third pipe C they can fill the tank in 5 hours. Pipe A is opened for 4 hours then it is closed, pipe B is closed 3 hours before filling of tank and tank C is opened the whole time. Calculate the time taken to fill the tank
In the following question, two statements are numbered as A and B. On solving these statements, we get quantities A and B respectively. Solve both quantities and choose the correct option. Quantity A: Pipe A takes thrice the time taken by Pipe B to fill a tank. Together they can fill the tank in 15 hours, tank A and B is opened together for 4 hours and then Pipe A is closed and after 2 more hours Pipe B is closed and an outlet Pipe C is opened which when working alone can empty the tank in 10 hours. Calculate the time taken by C to empty the tank. Quantity B: A pipe A can fill the tank in 10 hours another pipe B can fill the tank in 15 hours and with the help of third pipe C they can fill the tank in 5 hours. Pipe A is opened for 4 hours then it is closed, pipe B is closed 3 hours before filling of tank and tank C is opened the whole time. Calculate the time taken to fill the tank.
Which of the following statement(s) is/are incorrect? (i) A turbine is called an impulse turbine if at the inlet of the turbine total energy is only kinetic energy (ii) A turbine is called a reaction turbine if at the inlet of the turbine the total energy is kinetic energy and pressure energy (iii) The inward flow reaction turbine having radial discharge at the outlet is known as Kaplan turbine
In a reaction turbine, the fixed blades and moving blades are of the same shape but reversed in direction. The angle of the discharging tip is 20°. The mean blade velocity is 200 m/s. The axial velocity of flow of steam is half of the mean blade velocity. Determine the inlet angles of blades.
The conditions regarding selection from a list of suitable candidates to be called for interview after a written examination for appointment of management-level persons to a multi-national company providing accounting services and sales are mentioned below. Candidates: a) Must have a Bachelor's degree in Basic Science with 65% or more marks or BE with 55% or more marks. b) Must have passed the examination with 70% or more marks. c) Age must be between 25 to 30 years as of 1/4/18. d) Must have 3 years of experience in an Accounting Institution and must have a Diploma in Accounting with 60% or more marks. e) Must be currently getting CTC of Rs. 6 lakh or more per annum. If the candidate: 1) If he fulfills all the other conditions other than A above, he will be designated as Junior Accountant. 2) If he fulfills all the other conditions other than (d) and (e) above, he can be designated as Trainee-Accountant. If he fulfills all the above conditions including 5 years of experience, he can be designated as a Senior Accountant. He can be designated as Manager (Accounts) if he fulfills all the above criteria including educational qualifications of CA/ ICWA/ MBA (Finance). Study all the above information and answer the following question. Varun has passed the CA exam and has a bachelor's degree in basic science and a diploma in accountancy, having scored 75% or more in the written examination during his entire career and also in the written examination. His age is 27 years and with 4 years of experience in Accountancy, he has a CTC salary of 18 lakhs per annum. To which of the following positions can he be referred? Select from the given options.
Steam issues from the nozzle with a velocity of 1000 m/s in a De Laval turbine. The nozzle angle is 20°, mean blade velocity is 350 m/s. The inlet and outlet angles of the blades are equal. The mass of the steam flowing through the turbine per second is 0.3 kg. Calculate the tangential force on the blades. Take blade velocity coefficient as 0.8.
A tank has an inlet pipe and an outlet pipe. If the outlet pipe is closed then the inlet pipe fills the empty tank in 8 hours. If the outlet pipe is open then the inlet pipe fills the empty tank in 10 hours. If only the outlet pipe is open then in how many hours the full tank becomes half-full?
In a single row impulse turbine, the absolute velocity of steam leaving the turbine is 900 m/s. The nozzle angel is 20°. The mean blade speed is 300 m/s. The inlet blade angle is equal to the outlet blade angle. Determine the angle made by the discharging steam with the tangent of the wheel at the exit of moving blade. Neglect friction on turbine blades.
Pipe A takes 10 hours more than Pipe B to fill a tank. Pipe C(which is equally efficient as Pipe A and Pipe B together), fills the same tank in 12 hours. In how many hours will Pipe A, Pipe B and Pipe C fill the tank if Pipe A is accompanied by B and C on alternate hours.