1.) Explain what type of mechanism and application use a marine ste.pdf

1.) Explain what type of mechanism and application use a marine steam engine and why?
2.) Explain the history behind a marine steam engine? and compare how it is used in today
society?
Solution
1 a)
Basic operation of a simple reciprocating steam engine
Components of steam engines
There are two fundamental components of a steam engine: the boiler or steam generator, and the
motor unit, itself often referred to as a "steam engine." The two components can either be
integrated into a single unit or can be placed at a distance from each other, in a variety of
configurations.
Other components are often present; pumps (such as an injector) to supply water to the boiler
during operation, condensers to recirculate the water and recover the latent heat of vaporization,
and superheaters to raise the temperature of the steam above its saturated vapor point, and
various mechanisms to increase the draft for fireboxes. When coal is used, a chain or screw
stoking mechanism and its drive engine or motor may be included to move the fuel from a
supply bin (bunker) to the firebox.
Heat source
The heat required for boiling the water and supplying the steam can be derived from various
sources, most commonly from burning combustible materials with an appropriate supply of air in
a closed space (called variously combustion chamber, firebox). In some cases the heat source is a
nuclear reactor or geothermal energy.
Cold sink
As with all heat engines, a considerable quantity of waste heat is produced at relatively low
temperature. This must be disposed of.
The simplest cold sink is simply to vent the steam to the environment. This is often used on
Steam locomotives, but is quite inefficient. Steam locomotive condensing apparatus can be
employed to improve efficiency.
Steam turbines in power stations often use cooling towers which are essentially one form of
condenser.
Sometimes the "waste heat" is useful in and of itself, and in those cases very high overall
efficiency can be obtained; for example combined heat and power uses the waste heat for district
heating.

Boilers
Boilers are pressure vessels that contain water to be boiled, and some kind of mechanism for
transferring the heat to the water so as to boil it.
The two most common methods of transferring heat to the water according are:
Once turned to steam, some boilers use superheating to raise the temperature of the steam
further. This allows for greater efficiency.
Motor units
A motor unit takes a supply of steam at high pressure and temperature and gives out a supply of
steam at lower pressure and temperature, using as much of the difference in steam energy as
possible to do mechanical work.
A motor unit is often called "steam engine" in its own right. They will also operate on
compressed air or other gas.
Simple expansion
This means that a charge of steam works only once in the cylinder. It is then exhausted directly
into the atmosphere or into a condenser, but remaining heat can be recuperated if needed to heat
a living space, or to provide warm feedwater for the boiler.
Double acting stationary engine
Schematic Indicator diagram showing the four events in a double piston stroke
In most reciprocating piston engines the steam reverses its direction of flow at each stroke
(counterflow), entering and exhausting from the cylinder by the same port. The complete engine
cycle occupies one rotation of the crank and two piston strokes; the cycle also comprises four
events—admission, expansion, exhaust, compression. These events are controlled by valves
often working inside a steam chest adjacent to the cylinder; the valves distribute the steam by
opening and closing steam ports communicating with the cylinder end(s) and are driven by valve
gear, of which there are many types. The simplest valve gears give events of fixed length during
the engine cycle and often make the engine rotate in only one direction. Most however have a
reversing mechanism which additionally can provide means for saving steam as speed and
momentum are gained by gradually "shortening the cutoff" or rather, shortening the admission
event; this in turn proportionately lengthens the expansion period. However, as one and the same
valve usually controls both steam flows, a short cutoff at admission adversely affects the exhaust
and compression periods which should ideally always be kept fairly constant; if the exhaust
event is too brief, the totality of the exhaust steam cannot evacuate the cylinder, choking it and
giving excessive compression ("kick back").
In the 1840s and 50s, there were attempts to overcome this problem by means of various patent
valve gears with separate variable cutoff valves riding on the back of the main slide valve; the
latter usually had fixed or limited cutoff. The combined setup gave a fair approximation of the

ideal events, at the expense of increased friction and wear, and the mechanism tended to be
complicated. The usual compromise solution has been to provide lap by lengthening rubbing
surfaces of the valve in such a way as to overlap the port on the admission side, with the effect
that the exhaust side remains open for a longer period after cut-off on the admission side has
occurred. This expedient has since been generally considered satisfactory for most purposes and
makes possible the use of the simpler Stephenson, Joy, and Walschaerts motions. Corliss, and
later, poppet valve gears had separate admission and exhaust valves driven by trip mechanisms
or cams profiled so as to give ideal events; most of these gears never succeeded outside of the
stationary marketplace due to various other issues including leakage and more delicate
mechanisms.[5][6]
Compression
Before the exhaust phase is quite complete, the exhaust side of the valve closes, shutting a
portion of the exhaust steam inside the cylinder. This determines the compression phase where a
cushion of steam is formed against which the piston does work whilst its velocity is rapidly
decreasing; it moreover obviates the pressure and temperature shock, which would otherwise be
caused by the sudden admission of the high pressure steam at the beginning of the following
cycle.
Lead
The above effects are further enhanced by providing lead: As was later discovered with the
internal combustion engine, it has been found advantageous since the late 1830s to advance the
admission phase, giving the valve lead so that admission occurs a little before the end of the
exhaust stroke in order to fill the clearance volume comprising the ports and the cylinder ends
(not part of the piston-swept volume) before the steam begins to exert effort on the piston.[7]
Compounding engines
As steam expands in a high pressure engine its temperature drops; because no heat is released
from the system, this is known as adiabatic expansion and results in steam entering the cylinder
at high temperature and leaving at low temperature. This causes a cycle of heating and cooling of
the cylinder with every stroke which is a source of inefficiency.
A method to lessen the magnitude of this heating and cooling was invented in 1804 by British
engineer Arthur Woolf, who patented hisWoolf high pressure compound engine in 1805. In the
compound engine, high pressure steam from the boiler expands in a high pressure (HP) cylinder
and then enters one or more subsequent lower pressure (LP) cylinders. The complete expansion
of the steam now occurs across multiple cylinders and as less expansion now occurs in each
cylinder so less heat is lost by the steam in each. This reduces the magnitude of cylinder heating
and cooling, increasing the efficiency of the engine. To derive equal work from lower pressure
steam requires a larger cylinder volume as this steam occupies a greater volume. Therefore, the

bore, and often the stroke, are increased in low pressure cylinders resulting in larger cylinders.
Double expansion (usually known as compound) engines expanded the steam in two stages. The
pairs may be duplicated or the work of the large LP cylinder can be split with one HP cylinder
exhausting into one or the other, giving a 3-cylinder layout where cylinder and piston diameter
are about the same making the reciprocating masses easier to balance.
Two-cylinder compounds can be arranged as:
With two-cylinder compounds used in railway work, the pistons are connected to the cranks as
with a two-cylinder simple at 90° out of phase with each other (quartered). When the double
expansion group is duplicated, producing a 4-cylinder compound, the individual pistons within
the group are usually balanced at 180°, the groups being set at 90° to each other. In one case (the
first type of Vauclain compound), the pistons worked in the same phase driving a common
crosshead and crank, again set at 90° as for a two-cylinder engine. With the 3-cylinder
compound arrangement, the LP cranks were either set at 90° with the HP one at 135° to the other
two, or in some cases all three cranks were set at 120°.
The adoption of compounding was common for industrial units, for road engines and almost
universal for marine engines after 1880; it was not universally popular in railway locomotives
where it was often perceived as complicated. This is partly due to the harsh railway operating
environment and limited space afforded by the loading gauge (particularly in Britain, where
compounding was never common and not employed after 1930). However although never in the
majority it was popular in many other countries.[5]
Multiple expansion engines
An animation of a simplified triple-expansion engine.
High-pressure steam (red) enters from the boiler and passes through the engine, exhausting as
low-pressure steam (blue) to the condenser.
1890s-vintage triple-expansion marine engine that powered the SS Christopher Columbus.
Model of a triple expansion engine
SS Ukkopekka triple expansion steam engine
It is a logical extension of the compound engine (described above) to split the expansion into yet
more stages to increase efficiency. The result is the multiple expansion engine. Such engines use
either three or four expansion stages and are known as triple and quadruple expansion engines
respectively. These engines use a series of double-acting cylinders of progressively increasing
diameter and/or stroke and hence volume. These cylinders are designed to divide the work into
three or four, as appropriate, equal portions for each expansion stage. As with the double
expansion engine, where space is at a premium, two smaller cylinders of a large sum volume
may be used for the low pressure stage. Multiple expansion engines typically had the cylinders
arranged inline, but various other formations were used. In the late nineteenth century, the

Yarrow-Schlick-Tweedy balancing 'system' was used on some marine triple expansion engines.
Y-S-T engines divided the low pressure expansion stages between two cylinders, one at each end
of the engine. This allowed the crankshaft to be better balanced, resulting in a smoother, faster-
responding engine which ran with less vibration. This made the 4-cylinder triple-expansion
engine popular with large passenger liners (such as the Olympic class), but was ultimately
replaced by the virtually vibration-free turbine (see below).
The image to the right shows an animation of a triple expansion engine. The steam travels
through the engine from left to right. The valve chest for each of the cylinders is to the left of the
corresponding cylinder.
The development of this type of engine was important for its use in steamships as by exhausting
to a condenser the water can be reclaimed to feed the boiler, which is unable to use seawater.
Land-based steam engines could exhaust much of their steam, as feed water was usually readily
available. Prior to and during World War II, the expansion engine dominated marine applications
where high vessel speed was not essential. It was, however, superseded by the British invented
steam turbine where speed was required, for instance in warships, such as the pre-dreadnought
battleships, and ocean liners. HMS Dreadnought of 1905 was the first major warship to replace
the proven technology of the reciprocating engine with the then-novel steam turbine.
Uniflow (or unaflow) engine
Schematic animation of a uniflow steam engine.
The poppet valves are controlled by the rotating camshaft at the top. High pressure steam enters,
red, and exhausts, yellow.
This is intended to remedy the difficulties arising from the usual counterflow cycle mentioned
above which means that at each stroke the port and the cylinder walls will be cooled by the
passing exhaust steam, whilst the hotter incoming admission steam will waste some of its energy
in restoring working temperature. The aim of the uniflow is to remedy this defect by providing
an additional port uncovered by the piston at the end of its half-stroke making the steam flow
only in one direction. By this means, thermal efficiency is improved by having a steady
temperature gradient along the cylinder bore. The simple-expansion uniflow engine is reported to
give efficiency equivalent to that of classic compound systems with the added advantage of
superior part-load performance. It is also readily adaptable to high-speed uses and was a
common way to drive electricity generators towards the end of the nineteenth century, before the
coming of the steam turbine.
The inlet valves may be driven by a double cam system whose phasing and duration is
controllable; this allows adjustments for high torque and power when needed with more
restrained use of steam and greater expansion for economical cruising.
Uniflow engines have been produced in single-acting, double-acting, simple, and compound

versions. Skinner 4-crank 8-cylinder single-acting tandem compound[8] engines power two
Great Lakes ships still trading today (2007). These are the Saint Mary’s Challenger,[9] that in
2005 completed 100 years of continuous operation as a powered carrier (the Skinner engine was
fitted in 1950) and the car ferry,SS Badger.[10]
In the early 1950s, the Ultimax engine, a 2-crank 4-cylinder arrangement similar to Skinner’s,
was developed by Abner Doble for the Paxton car project with tandem opposed single-acting
cylinders giving effective double-action.[11]
Turbine engines
A rotor of a modern steam turbine, used in a power plant.
A steam turbine consists of an alternating series of one or more rotating discs mounted on a drive
shaft,rotors, and static discs fixed to the turbine casing, stators. The rotors have a propeller-like
arrangement of blades at the outer edge. Steam acts upon these blades, producing rotary motion.
The stator consists of a similar, but fixed, series of blades that serve to redirect the steam flow
onto the next rotor stage. A steam turbine often exhausts into a surface condenser that provides a
vacuum. The stages of a steam turbine are typically arranged to extract the maximum potential
work from a specific velocity and pressure of steam, giving rise to a series of variably sized high
and low pressure stages. Turbines are only effective if they rotate at very high speed, therefore
they are usually connected to reduction gearing to drive another mechanism, such as a ship's
propeller, at a lower speed. This gearbox can be mechanical but today it is more common to use
an alternator/generator set to produce electricity that later is used to drive an electric motor. A
turbine rotor is also capable of providing power when rotating in one direction only. Therefore, a
reversing stage or gearbox is usually required where power is required in the opposite direction.
Steam turbines provide direct rotational force and therefore do not require a linkage mechanism
to convert reciprocating to rotary motion. Thus, they produce smoother rotational forces on the
output shaft. This contributes to a lower maintenance requirement and less wear on the
machinery they power than a comparable reciprocating engine.
The Turbinia - the first steam turbine-powered ship
The main use for steam turbines is in electricity generation (about 80 percent of the world's
electric production is by use of steam turbines) and to a lesser extent as marine prime movers. In
the former, the high speed of rotation is an advantage, and in both cases the relative bulk is not a
disadvantage; in the latter (pioneered on the Turbinia), the light weight, high efficiency and high
power are highly desirable.
Virtually all nuclear power plants and some nuclear submarines, generate electricity by heating
water to provide steam that drives a turbine connected to an electrical generator for main
propulsion. A limited number of steam turbine railroad locomotives were manufactured. Some

non-condensing direct-drive locomotives did meet with some success for long haul freight
operations in Sweden, but were not repeated. Elsewhere, notably in the U.S., more advanced
designs with electric transmission were built experimentally, but not reproduced. It was found
that steam turbines were not ideally suited to the railroad environment and these locomotives
failed to oust the classic reciprocating steam unit in the way that modern diesel and electric
traction has done.
Rotary steam engines
It is possible to use a mechanism based on a pistonless rotary engine such as the Wankel engine
in place of the cylinders and valve gear of a conventional reciprocating steam engine. Many such
engines have been designed, from the time of James Watt to the present day, but relatively few
were actually built and even fewer went into quantity production; see link at bottom of article for
more details. The major problem is the difficulty of sealing the rotors to make them steam-tight
in the face of wear and thermal expansion; the resulting leakage made them very inefficient.
Lack of expansive working, or any means of control of the cutoff is also a serious problem with
many such designs. By the 1840s, it was clear that the concept had inherent problems and rotary
engines were treated with some derision in the technical press. However, the arrival of electricity
on the scene, and the obvious advantages of driving a dynamo directly from a high-speed engine,
led to something of a revival in interest in the 1880s and 1890s, and a few designs had some
limited success.
Of the few designs that were manufactured in quantity, those of the Hult Brothers Rotary Steam
Engine Company of Stockholm, Sweden, and the spherical engine of Beauchamp Tower are
notable. Tower's engines were used by the Great Eastern Railway to drive lighting dynamos on
their locomotives, and by the Admiralty for driving dynamos on board the ships of the Royal
Navy. They were eventually replaced in these niche applications by steam turbines.
Jet type
Invented by Australian engineer Alan Burns and developed in Britain by engineers at Pursuit
Dynamics, this underwater jet engine uses high pressure steam to draw in water through an
intake at the front and expel it at high speed through the rear. When steam condenses in water, a
shock wave is created and is focused by the chamber to blast water out of the back. To improve
the engine's efficiency, the engine draws in air through a vent ahead of the steam jet, which
creates air bubbles and changes the way the steam mixes with the water.
Unlike in conventional steam engines, there are no moving parts to wear out, and the exhaust
water is only several degrees warmer in tests. The engine can also serve as pump and mixer. This
type of system is referred to as "PDX Technology" by Pursuit Dynamics.
Rocket type
The aeolipile represents the use of steam by the rocket-reaction principle, although not for direct

propulsion.
In more modern times there has been limited use of steam for rocketry—particularly for rocket
cars. The technique is simple in concept, simply fill a pressure vessel with hot water at high
pressure, and open a valve leading to a suitable nozzle. The drop in pressure immediately boils
some of the water and the steam leaves through a nozzle, giving a significant propulsive force.
It might be expected that water in the pressure vessel should be at high pressure; but in practice
the pressure vessel has considerable mass, which reduces the acceleration of the vehicle.
Therefore, a much lower pressure is used, which permits a lighter pressure vessel, which in turn
gives the highest final speed.
There are even speculative plans for interplanetary use. Although steam rockets are relatively
inefficient in their use of propellant, this very well may not matter as the solar system is believed
to have extremely large stores of water ice which can be used as propellant. Extracting this water
and using it in interplanetary rockets requires several orders of magnitude less equipment than
breaking it down to hydrogen and oxygen for conventional rocketry.[12]
2) The History of the Steam Engine
The history of steam engines dates back to the 1st century AD when the “aeolipile” was
described by the Hero of Alexandria for the first time. More than 1500 years later, the primitive
forms of turbines driven by the power of steam were explained by Taqi al-Din in 1551 as well as
Giovanni Branca in 1629. These were either small steam jacks or escapement devices. They were
mainly used by inventors to demonstrate that the power of steam shouldn’t be underestimated.
There was a significant industrial challenge that miners faced during the 1700's and this was
related to the extraction of water from deep mines. At this time, the true power of steam was
showcased as the energy was used to pump up the water from deep within the mines. With this,
the potential power of steam was discovered, leading to the invention of a full fledgedsteam
engine. Steam-powered electrical power plants in the modern world came later. The basic
principle on which the initial steam engines worked on was “condensation of water vapor to
create a vacuum”.Thomas Savery and the First Industrial Engines Thomas Savery was the first
person to invent a steam pump for the purpose of pumping out water in 1698. He called it “water
by fire". The steam pump patented by him worked by boiling water until it was completely
converted into vapor. The steam was then collected in a tank extracting every droplet of vapor
from the original tank, thereby creating a vacuum in the original container. It was this vacuum
that was employed to produce an adequate amount of energy to pump water out from the mines.
This turned out to be a temporary solution as the energy could draw out water from the depth of
only a few meters. Another drawback of this pump was that the steam pressure was being used to
remove the water that was being drawn inside the tank. The pressure was too much for the
boilers and there were several explosions as the boilers were not strong enough.

· Thomas Savery: A biography of Thomas Savery with information about his engine.
· Steam Engine Development: The article highlights the steam engine development
covering Savery’s contributions and the atmospheric engines.
Low Pressure Engines
The high consumption of coal which was common in Newcomen’s steam engine was reduced
through innovations in engine design by James Watt. The low pressure engine’s cylinder
contained heat insulation, a separate condenser, and a pumping out mechanism for condensed
water. In this manner, the low pressure engine was successful in reducing fuel consumption by
more than 50%.
· Watt’s Low-Pressure Steam Engine: The Deutsches Museum offers some information on
this early engineering marvel.
Ivan Polzunov and the First Two-Cylinder Steam Engine
Ivan Polzunov was a Russian inventor who built the first steam engine in his country. Polzunov’s
two cylinder steam engine was more powerful than the English atmospheric engines. It had a
power rating of 24 kw. Polzunov’s model of a two cylinder steam engine is presently displayed
the Barnaul Museum.
· Ivan Polzunov: The article provides information on how this Russian scientist built the
two-cylinder steam engine.
· Two Cylinder Steam Engine: Here’s a picture of a two cylinder steam engine from the
1880s.
Engine Developed by Thomas Newcomen
In 1712, Thomas Newcomen invented an effective and practical steam engine. The steam engine
designed by him consisted of a piston or a cylinder that moved a huge piece of wood to drive the
water pump. The engine did not use steam pressure to exert any pressure on the piston but it was
the wooden piece that was heavier towards the main pump. It was gravity that pulled down the
pump side of the wooden piece. The Newcomen engine remained in use for more than 50 years
but they turned out to be inefficient as a lot of energy was required for the engine to run
effectively. The cylinder was required to be heated as well as cooled every time, which used up
most of its energy causing a huge amount of wastage.
· Newcomen’s Steam Engine: The BBC provides information on the steam engine by this
man with an illustration.
· Thomas Newcomen’s Steam Engine: Come here to learn all about the steam engine
created by Thomas Newcomen.
James Watt’s Improvements
Finally, it was James Watt who revolutionized the steam engine by making use of a separate
condenser in the original design. He came up with a separate condenser in 1765. The design saw

itself take shape on a successful steam engine only 11 years later. The biggest issue with its
implementation was the technology of creating a huge piston so as to preserve a moderate
amount of vacuum. The technology saw great progress. When the financial backing became
available, the engine was finally introduced in railways and ships. There were over 60,000 cars
powered by steam during the years from 1897 to 1927 in the United States.
· James Watt: A well written and lengthy biography of James Watt.
· James Watt (1736-1819): The Corrosion Doctors provide another account of the man’s
life and achievements.
· Steam Engine: A description of how James Watt improved the steam engine.
· James Watt & the Steam Engine: Samuel Smiles explains how James Watts dedicated his
life to perfect the steam engine.
High Pressure Engines
It was during 1800 that Richard Trevithick invented engines with steam backed by high pressure.
These turned out to be more powerful compared to all the engines invented previously but it was
the engine design presented by Oliver Evans that became a success. It used the concept of steam
for powering an engine rather than condensing steam and creating a vacuum. Evans came up
with the first non-condensing and high-pressure steam engine in 1805. The engine was stationary
and it was capable of producing 30 RPM (revolutions per minute). This engine was used for the
first time to run a saw. The high pressure engines were backed up by huge cylindrical tanks filled
with water that was heated by placing a heat source right below it in order to produce adequate
steam.
In time, these steam engines were used in power boats and railways in 1802 and 1829
respectively. Almost half a century later, the first steam-powered automobiles were invented.
Charles A. Parsons came up with first steam turbine in 1880. By the 20th century, the steam
engine was widely used in automobiles and ships.
· High Pressure Steam Engines: The University of Houston offers information on these
engines.
· Modern High Pressure Steam Locomotives: Come here to learn more about these
machines.
The Cornish Steam Engine
Richard Trevithick attempted to update the pumping engine made by Watt. It was modified to
adapt to the Cornish boilers which Trevithick had designed. The efficiency of Cornish Steam
Engines was subsequently improved by William Sims, Arthur Woolf, and Samuel Groase. The
updated Cornish Steam Engines had insulated engine, pipes, and boilers for improved efficiency.
· Richard Trevithick: Here’s a biography of this industrial genius.
· Beam Engines: The Cornish World Heritage provides information on the development of

steam engines in the mining industry in those times.

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