WORKING AND CONSTRUCTION OF CENTRIFUGAL COMPRESSOR

In this type of compressor, air enters axially and leaves radially.

CONSTRUCTION :

The arrangement of centrifugal compressor consists of rotating Impeller , a casing and a diffuser. The impeller consists of a disc on which radial blades are attached. The impeller is surrounded by casing. The diffuser is another important part of the compressor, which is used to convert kinetic energy of air into pressure energy. The air coming out from the diffuser is collected in the casing and taken out from the outlet of the compressor. The Impeller of a centrifugal compressor can be run at the speed of 20,000 to 30,000 rpm.

WORKING :

When the power is given to compressor, the impeller rotates, and it sucks the air. This air enters axially with low velocity. The velocity and pressure of the air passing through the impeller are partially increased. Then the air is entered into diffuser. In the diffuser, kinetic energy is converted into pressure energy. So, the pressure of air is further increased . Finally, the air at high pressure is delivered to the receiver. Nearly half of the total pressure rise is achieved in the impeller and remaining half in the diffuser. The change of pressure. The change of pressure and velocity of air passing through the impeller and diffuser.

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THROTTLE GOVERNING OF STEAM TURBINES

Steam Pressure at inlet to a steam turbine is reduced by throttling process to maintain the speed of the turbine constant at part load and hence this method of governing is called "Throttle Governing". Construction : Throttle governing system consists of a centrifugal governor, a lever , an oil pump , a pilot piston , control valve , a relay piston and a throttle valve. The throttle valve is moved by a relay piston. The relay piston is actuated by pilot piston control valve. There are two piston valves covering ports in the pilot piston control valve without any overlap. These piston valves are operated by lubricating oil supplied by a gear pump at 2 to 4 bar. The oil returns to the drain from this chamber. Working : When the turbine works on full rated load, the throttle valve will remain open. When the load is decreased, the energy output of the turbine becomes in excess and the turbine shaft speed increases. Hence, governor sleeve will lift. The upward movement of the

ELECTRICAL COMPARATORS AND ITS WORKING

Electrical Comparators are used as a means of detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a roll. The object to be checked is place

Advantages And Disadvantages Of Air Refrigeration System :

Advantages Of Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content.

Mechinopedia For Mechanical Engineers

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