1. Introduce to Steam Engine
A steam engine is a heat engine that performs
mechanical work using steam as its working fluid.
In simple terms, the steam engine uses the
expansion principle of chemistry, where heat
applied to water evaporates the water into steam,
and the force generated pushes a piston back and
forth inside a cylinder
2. Main part of steam engines
Boiler
Piston
Slide valve
Cylinder
Flywheel
Connecting Rod
3. Fire-tube boiler – hot gas is passed through tubes immersed in
water, the same water also circulates in a water jacket
surrounding the firebox and, in high-output locomotive boilers,
also passes through tubes in the firebox itself (thermic syphons
and security circulators)
Fire tube boilers were the main type used for early high-
pressure steam (typical steam locomotive practice), but they
were to a large extent displaced by more economical water tube
boilers in the late 19th century for marine propulsion and large
stationary applications.
Main part of steam engines
5. Piston
A piston is made of cast iron and acts as a sliding round plug
inside of the cylinder. It is secured to the piston rod by a nut.
• The piston rod is round, made of steel, the top end is
secured to the piston, the bottom end to the crosshead. To
prevent steam from blowing out of the cylinder around the
rod, metallic type packing is installed around the rod in the
stuffing box.
6. Slide Valve
This valve is fixed on the steam chest. Its function is
to admit the steam from steam chest to the
cylinder.
Slide valve also exhausts the steam from the
cylinder at the proper moment.
The valve gets to and fro motion from the eccentric
fitted on the crankshaft.
7. Working principle of Steam Engine
Heat engine that converts heat to work.
Required components: – Fuel as source of heat
(e.g. wood, coal, gas, solar, nuclear)
Working fluid (e.g. water)
Closed cycle including compressor and expansion
unit – Mechanical part to do work (e.g. turbine)
8. Thermodynamic Cycle
In the study of converting heat (thermo) into
mechanical (dynamic) action or work, many cycles
have been proposed to describe the relationship
between the heat you provide and the work you get
out.
The goal is to maximize the efficiency of the cycle, i.e.
To increase the ratio [work out/heat in].
9. Classification of steam engine
Based on axis of engine:
Orientation of cylinder axis :
I. Horizontal steam engine
II. Vertical steam engine
Based on speed of engine
. I. High speed engine- speed of 250rpm and above
II. Medium speed engine- speed 100 to 250 rpm
III. Slow speed engine- speed 100rpm and below
Based on type of steam action:
I. Double acting steam
II. Single acting steam engine
10. Advantage of steam engine
1. A steam engine (or external combustion engine) can be used at
any time because steam can be produced at any time.
2. A steam engine (or external combustion engine) can be used
to run trains for going from one place to another place.
3. A steam engine (or external combustion engine) is much more
powerful than a wind-mill or water-mill.
4. A steam engine (or external combustion engine) can use
virtually any combustible material for fuel-wood, coal, oil, old
furniture, …anything that can be put into the firebox.
11. Disadvantage of steam engine
1. A steam engine is huge and heavy. (That is an external
combustion engine is huge and heavy).
2. A steam engine is unsafe to use. (That is, An external
combustion engine is unsafe to use).
3. A steam engine does not start at once. (That is, An external
combustion engine does not start at once). Before a steam
engine can start, we have to build a coal fire to get steam.
This process takes a long time and hence a steam engine
cannot be started at a moment’s notice.
12. Application of steam engine
Refrigeration
Air Conditioning
Heat Pumps
Geothermal Pumps
![Thermodynamic Cycle
In the study of converting heat (thermo) into
mechanical (dynamic) action or work, many cycles
have been proposed to describe the relationship
between the heat you provide and the work you get
out.
The goal is to maximize the efficiency of the cycle, i.e.
To increase the ratio [work out/heat in].](https://image.slidesharecdn.com/346007230-250812155125-58145acb/85/Solid-mechanics-_-Mechanical-engineering-8-320.jpg)
