Parson's Reaction Turbine and Components

Parsons Reaction Turbine and Components Points : Parsons Reaction Turbine and Components, Casing, Guide Mechanism, Turbine Runner, Draft tube A parson’s turbine is the simplest type of reaction steam turbine, and is commonly used. It has the following main components. 1. Casing It is an airtight metallic case, in which the steam from the boiler, under a high pressure and temperature, is distributed around the fixed blades (guides’ mechanism) in the casing. The casing is designed in such a way that the steam enters the fixed blades with a uniform velocity. 2. Guide Mechanism It is a mechanism, made up with the help of guide blades, iii the form of wheel. This wheel is, generally, fixed to the casing; that is why these guide blades are also called fixed blades, The guide blades are properly designed in order to:
(a) allow the steam to enter the runner with out shock. This is done by keeping the relative velocity at inlet of the runner tangential to the blade angle.
(b) allow the required quantity of steam to enter the turbine. This is done by adjusting the openings of the blades.
The guide blades may be opened or closed by rotating the regulating shall, thus allowing the steam to flow according to the need. The regulating shaft, thus allowing the steam to flow according to the need. The regulating shaft is operated by means of a governor whose function to govern the turbine (i.e., to keep to speed constant at varying loads). 3. Turbine Runner The turbine runner of a Person’s reaction turbine essentially consist of runner blades fixed to a shaft or ring, depending upon the tube of turbine. The blades, fixed to the runner, are properly designed in order to allow the steam to enter and leave the runner without shock. The surface of the turbine runner is made very smooth to minimize the frictional losses. The turbine runner is, generally, cast in one piece. But some times, it is made up of separate steel plates welded together. 4. Draft tube The steam, after passing through the runner, flows into the condenser through a tube called draft tube. It may be noted that if this tube is not provided in the turbine then the steam will move freely and will cause steam eddies.