Hydraulic Machines

INTRODUCTION

Hydraulic Machines are devices that convert energy between a fluid and a mechanical system. In these machines, energy is transferred either from the fluid to the machine or from the machine to the fluid. The subject of Fluid Machines forms a core part of Mechanical Engineering, as it deals with machines widely used in power generation, water supply, irrigation, industries, and transportation.

Understanding fluid machines is essential for designing and operating equipment such as pumps, turbines, compressors, and fans, which are indispensable in modern engineering systems.

1. Definition of Fluid Machine

A fluid machine is a device in which energy is exchanged between a fluid and a mechanical system by means of fluid flow.

  • If energy is given to the fluid, the machine is called a fluid energy absorbing machine.
  • If energy is taken from the fluid, the machine is called a fluid energy producing machine.

2. Importance of Fluid Machines

Fluid machines play a vital role in engineering and society due to the following reasons:

  1. Power Generation – Hydraulic turbines convert water energy into electrical power.
  2. Water Supply and Irrigation – Pumps are used to lift and transport water.
  3. Industrial Applications – Used in chemical plants, refineries, and manufacturing units.
  4. Transportation – Compressors and turbines are used in aircraft and marine engines.
  5. Energy Utilization – Enable efficient use of natural resources like water and air.

3. Scope of the Subject Fluid Machines

The subject mainly deals with:

  • Principles of fluid flow and energy transfer
  • Construction and working of pumps and turbines
  • Performance analysis and efficiency
  • Selection of suitable machines for applications
  • Losses and methods of improvement

4. Classification of Fluid Machines

Fluid machines are broadly classified based on direction of energy transfer.

4.1 Fluid Energy Producing Machines (Turbines)

These machines extract energy from the fluid and convert it into mechanical energy.

Examples:

  • Hydraulic turbines
  • Steam turbines
  • Gas turbines

4.2 Fluid Energy Absorbing Machines (Pumps and Compressors)

These machines absorb mechanical energy and transfer it to the fluid.

Examples:

  • Pumps
  • Fans
  • Blowers
  • Compressors

5. Hydraulic Machines

Hydraulic machines are fluid machines that use liquids (mainly water) as the working fluid.

They are divided into:

5.1 Hydraulic Turbines

Convert hydraulic energy into mechanical energy.

Examples:

  • Pelton turbine
  • Francis turbine
  • Kaplan turbine

5.2 Hydraulic Pumps

Convert mechanical energy into hydraulic energy.

Examples:

  • Centrifugal pump
  • Reciprocating pump

6. Pumps

A pump is a hydraulic machine that lifts liquids from a lower level to a higher level or increases pressure of the liquid.

Functions of Pumps:

  • Water supply
  • Drainage and sewage systems
  • Oil transportation
  • Cooling systems

Classification of Pumps:

  • Positive displacement pumps
  • Rotodynamic pumps

7. Turbines

A turbine is a fluid machine that converts the kinetic and pressure energy of fluid into mechanical energy.

Uses of Turbines:

  • Generation of electricity
  • Driving pumps and compressors
  • Industrial power production

8. Principle of Energy Transfer in Fluid Machines

The working of fluid machines is based on Newton’s laws of motion and conservation of energy.

Energy transfer takes place due to:

  • Change in velocity of fluid
  • Change in pressure
  • Change in direction of flow

This energy transfer is explained using velocity triangles and Euler’s equation of turbomachinery (studied in later chapters).

9. Types of Fluid Flow in Fluid Machines

  • Steady and unsteady flow
  • Uniform and non-uniform flow
  • Laminar and turbulent flow
  • Compressible and incompressible flow

Understanding flow types is essential for efficient design and performance analysis.

10. Performance Parameters of Fluid Machines

Important parameters include:

  • Discharge – Volume of fluid flowing per second
  • Head – Energy per unit weight of fluid
  • Power – Energy transferred per unit time
  • Efficiency – Ratio of useful output to input energy
  • Specific speed – Used for selection of machines

11. Advantages of Fluid Machines

  • Continuous and smooth power transmission
  • High efficiency
  • Capable of handling large power
  • Long service life
  • Reliable operation

12. Applications of Fluid Machines

  • Hydroelectric power plants
  • Thermal power plants
  • Water supply systems
  • Irrigation canals
  • HVAC systems
  • Oil and gas pipelines
  • Marine and aircraft systems

13. Importance of Studying Fluid Machines

  • Core subject for mechanical engineers
  • Essential for power plant engineering
  • Helps in design and selection of machines
  • Foundation for advanced subjects like turbomachinery and CFD
Continue Your Study Chapter Wise
CHAPTER 1 : Properties of Fluids
CHAPTER 2 : Impact of Jets
CHAPTER 3 : Introduction to Hydraulic Turbines
CHAPTER 4 : Francis Turbine
CHAPTER 5 : Kaplan and Propeller Turbines
CHAPTER 6 : Draft Tubes
CHAPTER 7 : Performance of Hydraulic Turbines
CHAPTER 8 : Introduction to Hydraulic Pumps
CHAPTER 9 : Centrifugal Pumps
CHAPTER 10 : Performance of Centrifugal Pumps
CHAPTER 11 : Reciprocating Pumps
CHAPTER 12 : Rotary Pumps
CHAPTER 13 : Cavitation
CHAPTER 14 : Governing of Turbines
CHAPTER 15 : Losses in Hydraulic Machines