KEY FEATURES OF A STEAM ENGINE
https://www.mesubjects.net/wp-admin/post.php?post=7839&action=edit steam tables and Mollier chart
https://www.mesubjects.net/wp-admin/post.php?post=7835&action=edit Steam properties
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KEY FEATURES OF STEAM ENGINES
Steam engine works with steam made in the boiler. It converts heat energy of steam into mechanical motion. Then it is converted into electrical energy. It is achieved with the help of a generator coupled with the steam engine.
The Rankine cycle is used in the analysis of steam engine. The Rankine cycle is a modified Carnot Cycle and is thus most efficient. Thomas Savery , Thomas Newcomen and James Watt made the best contribution in the invention and improvement of the steam engine.
Advantages of a steam engine
It made an industrial revolution. Even today steam engine is the most widely used method of electricity generation. It has high efficiency. The limitations of a steam engine are many.
The efficiency of Carnot Cycle is
η= [ (Th-Tl)/Th] x 100
The efficiency of the Rankine cycle is
η=[(h1—h2)/(h1—hl)] x 100
The efficiency of the modified Rankine cycle is
η =[(p1v1+(u1-u2)p3v2)/(h1—hl)] x 100
Mean effective pressure
he mean effective pressure is a constant pressure which acts on the piston throughout the stroke will produce the same work as is being produced under actual operating conditions.
Mean effective pressure with zero clearance volume is
pm = (p1/re)(1+lnre -pb)
Mean effective pressure with clearance volume, Vc is given by
pm = [(p1/re)(1+lnre) -pbV2-(p1-p2)Vc]/Vs
Missing quantity in a steam engine is contributed by the followings:
- Condensation of steam in the condenser
Steps to reduce the missing quantity
- Use compound compression
- Provide efficient jacket to the cylinder
Specific steam consumption
It means steam consumed per hour per indicated power produced.
Willan’s law of steam consumption
Steam consumption by a steam engine with throttled governor is directly proportional to the indicated power.
- m. = a x ip +b
Where b is the intercept on y axis at no lad condition
- m. is the stem consumption in kg/h
a and b are constants
ip is the indicated power produced per h