Mechanism of Steam Engines Part 12

Tham khảo tài liệu 'mechanism of steam engines part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | STEAM TURBINES 149 twelve pressure stages. Fig. 170 is a section of three wheels and diaphragms near the rim. Fig. 171 is a view of one of the diaphragms showing the openings which serve as nozzles for the second and all succeeding stages. 111. Combined Pressure-stage and Velocity-stage Turbines. In this class of turbines of which the Curtis built by the General Electric Company is a familiar example there are two or more pressure stages as described in no and each of these pressure stages consists of two velocity stages. Fig. 172 is a section of a Curtis Turbine having four Diaphragm Dm it Fig. 173. pressure stages as indicated at the top of the drawing. Each one of the wheels has two rows of buckets with stationary guide vanes between giving two velocity stages at each wheel. Fig. 173 shows the form of the buckets and nozzles. The following taken from the General Electric Company s instruction book will explain the flow of steam in the Curtis turbine Steam ỈS admitted into the turbine casing through the first stage MECHANISM OF STEAM ENGINES 150 nozzle which is of the expanding type and changes pressure energy into velocity energy. The steam pressure on the entrance side of the nozzle is equal to the boiler pressure less the small drop due to steam pipe friction. The steam pressure on the exit side of the nozzle is that of the first stage usually much less than half the initial pressure depending on the total number of pressure stages load etc. The steam in passing through the nozzle receives a high velocity energy equal to the drop of pressure energy and is directed by the nozzle into the first row of buckets in the first pressure stage. The steam in passing through the moving buckets of each stage does so at constant pressure but with loss of velocity. The direction of the steam is reversed on leaving the first row of buckets but the steam is redirected by a set of intermediate buckets. It then enters the second row of buckets on the first stage wheel in its .

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