The presentation is regarding various Thermal Machines that produce power or convert one form of energy into other. The presentation covers basics regarding the same which will be beneficial for beginners to understand the concepts
transforms the chemical energy of a fuel into thermal energy and uses this energy to produce mechanical work • It is classified into two types- (a) External combustion engine (b) Internal combustion engine Milind Pelagade 2
the products of combustion of air and fuel transfer heat to a second fluid which is the working fluid of the cycle. •Example:- •steam turbine, closed cycle gas turbine Internal combustion engine: •In this engine, the combustion of air and fuels take place inside the cylinder and are used as the direct motive force. •Example •Petrol Engine, Diesel Engine Milind Pelagade 3
• Four Stroke Cycle Engines Cycle of operation (No of Strokes per cycle) • Otto Cycle Engines (Combustion at constant volume) • Diesel Cycle Engines (Combustion at constant Pressure) • Semi Diesel Engines (Dual Combustion Engines) Thermodynamic Cycle or Method of Heat addition: • Petrol Engines • Diesel Engines Types of Fuel Used : • Ignition Method • Spark Ignition (SI) • Compression Ignition (CI) Gas Engines Milind Pelagade 4
extracts energy from a fast-moving flow of water, steam, gas, air, or other fluid and converts it into useful work. ➢ A turbine is a turbo-machine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. ➢ Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Milind Pelagade 13
the turbine, the blades are displaced, which produces rotational energy. • When the turbine shaft is directly coupled to an electric generator mechanical energy is converted into electrical energy. Milind Pelagade 14
is fired through a narrow nozzle at the turbine blades to make them spin around. • The blades of an impulse turbine are usually bucket-shaped so they catch the fluid and direct it off at an angle. • the fluid is forced to hit the turbine at high speed thus moving the wheel to generate electricity. Milind Pelagade 16
head, low flow power plants • Nozzles are direct forceful, high speed streams of water against a rotary series of spoon-shaped buckets, also known as impulse blades, which are mounted around the circumferential rim of a drive wheel also called a runner. • As the water jet hit the bucket-blades, the direction of water velocity is changed to follow the contours of the bucket. • Water impulse energy exerts torque on the bucket and wheel system, spinning the wheel; the water stream itself does a "u- turn" and exits at the outer sides of the bucket. • Pelton wheels operate best with Drop height 50 - 2000 m. Milind Pelagade 17
and exhaust of water takes place at atmospheric pressure hence no draft tube is required. • It has simple construction. • It can work on high heads and low discharge. • Limitations:- • It requires high head for operation. • Turbine size is generally large. • Its efficiency decreases quickly with time. • Due to high head it is very difficult to control variations in operating head. Milind Pelagade 19
turbine for hydro-power, when the available water source has relatively high hydraulic head at low flow rates. • Pelton wheels are made in all sizes. For maximum power and efficiency, the wheel and turbine system is designed such that the water jet velocity is twice the velocity of the rotating buckets. • There exist in multi ton Pelton wheels mounted on vertical oil pad bearing in hydroelectric power. Milind Pelagade 20
increase the pressure of air from low pressure to high pressure by using some external energy • In doing so it reduces the volume of the air/gas/fluid • Compressors are like pumps; both increase the pressure on a fluid, and both can transport the fluid through a pipe. • As gases are compressible, the compressor also reduces the volume of a gas. • Many compressors are staged, that is, the fluid is compressed several times in steps or stages, to increase discharge pressure. Milind Pelagade 21
system which compresses the air by the displacement of a mechanical linkage reducing the volume • A positive displacement compressor is one which operates by drawing in a discrete volume of gas from its inlet then forcing that gas to exit via the compressor's outlet. Milind Pelagade 23
crankshaft • They can be either stationary or portable, can be single or multi-staged, and can be driven by electric motors or internal combustion engines • In certain applications, such as air compression, multi-stage double-acting compressors are said to be the most efficient compressors available, and are typically larger, and more costly than comparable rotary units. • This type of compressor can compress a wide range of gases, including refrigerant, hydrogen, and natural gas. • However, it suffers from higher losses due to clearance volumes, resistance due to discharge and suction valves, weighs more, is difficult to maintain due to having a large number of moving parts, and it has inherent vibration Milind Pelagade 24
gas. • It can compress gases and refrigerant of a wide range of molecular density. • High efficiency and flexibility. • Cheap and rugged design. • Disadvantages of Reciprocating Compressor:- • The size of compressor is very large for a given capacity. • Part of the work input is lost due to frictional resistance between the piston and cylinder. • Pulsating of fluid flow. The operation can be made smooth by using a flywheel. • High vibration and noise. • Piston rings and valves are extremely sensitive to the dirt present in the fluid. Milind Pelagade 26
power generation plant in which the prime mover is driven by steam. Steam is produced by heating Water is heated, it turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated. Milind Pelagade 28
Less space is required ⚫ The initial cost is less ⚫ Plant can be located near the load center ⚫ Turbine can work at 25% overload continuously ⚫ A portion of steam can be used in various industries Milind Pelagade 34
are high ⚫ Pollution of atmosphere is one of the major problems ⚫ Water is required in huge quantity ⚫ Handling of coal and disposal of ash are difficult tasks ⚫ It requires long time for installation ⚫ Efficiency falls quickly below 75% Milind Pelagade 35
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