The Power of Mechanical Engineering

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The Power ofMechanical Engineering
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Mechanical Engineering

• The word engine and ingenious are derived
  from the Latin root ingenerate which means to
  create .
• Thus early engineers were the people who
  contrived, invented and created new things.
• Although many mechanisms had purely peaceful
  applications, such as for flight, irrigation or
  building, the word engineer originally meant
  military engineer because it was derived from
  the term engines of war. These were machines
  such as catapults, floating bridges and assault
  towers.
• After the Industrial Revolution a new
  classification of engineering dealing with tools
  and machines emerged, namely Mechanical
  Engineering.

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Professional EngineeringBodies

• In 1818 the Institution of Civil Engineers was
  founded. At that time the word civil was used
  to distinguish them from Military Engineers and
  included all the fields of engineering.
• The Institution of Mechanical Engineers was
  founded in 1847 by the railway pioneer George
  Stephenson and others.

• The Institute of Electrical Engineers was founded
  later in 1871.

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POWER
I SELL HERE, SIR, WHAT ALL THE WORLD DESIRES TO
HAVE POWER
On the eve of the Industrial Revolution
ENGINEERING POWER would be the primary agent of
change.
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Types of Power
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Types of Power
Mechanical Power
including Motive Power
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What is POWER
Let us look first at ENERGY
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ENERGY
Conservation of Energy Energy may be
transformed from one form to another, but it is
never created or destroyed.
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ENERGY
Forms of Energy
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ENERGY(Mechanical Engineering)
Potential
Kinetic
Thermal
Forms of Energy
Chemical
Electrical
Nuclear
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ENERGY

• Ball falls freely under the influence of gravity.
• It accelerates downwards, its initial potential
  energy is converted into kinetic energy.
• On impact with hard surface the ball deforms,
  converting the kinetic energy into elastic
  potential energy.
• As the ball springs back, the energy converts
  back firstly to kinetic energy and then as the
  ball regains height into potential energy.

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ENERGYUnit of Energy is the Joule(in
mechanical energy the 1 Joule 1 Nm)
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Energy Transfer
Because energy is conserved, it is important to
remember that by definition of energy the
transfer between the system and adjacent
regions is WORK. A familiar example is mechanical
work.
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TORQUE
Torque is a form of work associated with Motive
Power
Torque (T), also called a moment or couple,
is thought of as Rotational Force or Angular
Force which causes a change in rotational motion.
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TORQUE
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Mechanical Power
Fuel Energy Systems
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Steam Power
Early Inventions
The principles behind this device were not well
understood, and its full potential was not
realised for well over a millennium.
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Steam Power
Hero was known for his amazing mechanical
ingenuity in the ancient world. His other
inventions and interests included

• An early vending machine

• Mechanisms for the Greek theatre

• Study of optics

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Early ReciprocatingSteam Engines
Vacuum Engines
These early steam engines, or fire engines as
they were known were at first called names such
as atmospheric and condensing engines. But
as they worked on the vacuum principle they are
more generally known as Vacuum Engines. They were
used mainly for the raising of water. Early
engineers involved in the development of this
type of steam engine included Thomas Savery
fire engine (1698) Thomas Newcomer
atmospheric engine (1712) James Watt improved
Newcomer engine (1769)
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Early ReciprocatingSteam Engines
Thomas Newcomer
Born in Dartmouth in 1663 he was an ironmonger by
trade and Baptist lay preacher by calling. The
Dartmouth area was noted for its tin mining.
Flooding was a major problem, limiting the depth
at which the mineral could be mined. Newcomer
perfected a practical steam engine for pumping
water, the Newcomer steam engine. Consequently,
he is often referred to as a father of the
Industrial Revolution.
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Early ReciprocatingSteam Engines
Operation of the Newcomer Atmospheric Engine
These engines operated by admitting low pressure
steam into an operating chamber or cylinder. The
inlet valve is then closed and the steam cooled
(through the cold water header tank supply),
condensing it to a smaller volume and thus
creating a vacuum in the cylinder. The upper end
of the cylinder being open to atmosphere pressure
operates on the opposite side of the piston,
pushing the piston to the bottom of the cylinder.
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Early ReciprocatingSteam Engines
James Watt (1736 1819)
James Watt was a Scottish inventor and engineer
whose improvements to the steam engine were
fundamental to the change brought by the
Industrial Revolution.
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Early ReciprocatingSteam Engines
James Watts Steam Engine
Watt experimented with Newcomers engine and
showed that about 80 of the heat of the steam
was consumed in heating the cylinder, because the
steam in it was condensed by cold water. His new
design caused the steam to condense in a separate
chamber apart from the piston. This greatly
improved the efficiency of the engine making it a
more economical device. His commercial engines
were manufactured in partnership with Matthew
Boulton.
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Early ReciprocatingSteam Engines
High Pressure Engines
Around 1811 Richard Trevithick was required to
update a Watt pumping engine in order to adopt it
to one of his new Cornish boilers. This
development lead to the high pressure engine
which operated at around 40 psi (2.8 bar) and now
provided much of the power for the downward
stroke of the piston.
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Double Acting Reciprocating Steam Engines
The next major advance in high pressure steam
engines was to make them double-acting. In the
single-acting high pressure engine the cylinder
is vertical and the piston returns to the start,
or bottom, of the stroke by the momentum of the
flywheel.
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Double Acting Reciprocating Steam Engines
Steam Distribution
The complete cycle of the double-acting engine
occupies one rotation of the crank and two piston
strokes the cycle also comprises of four events

• Admission
• Expansion
• Exhaust
• Compression

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Steam Engines
Other Types of Steam Engines
Double and triple expansion, usually know as
COMPOUND engines have been developed over the
years. These types of engine make greater use of
the steam pressure at various stages in the
compound cycle. These multiple expansion engines
have been used on railways and in ships.
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Steam Engineson the Railways
George Stephenson (1781 1848)
An English mechanical engineer who built the
first public railway line in the world to use
steam locomotives and he is known as the Father
of Railways. The original railway developed by
Stephenson was the Stockton and Darlington. He
went on to build the Bolton and Leigh and
Liverpool and Manchester railways, all of which
used steam engines for the motive power.
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Steam Engineson the Railways
George Stephensons first locomotive was named
Active, later to be renamed Locomotion.
However, his most famous locomotive was the
ROCKET which he entered for the competition to
decide who would build the LMR, a competition he
won.
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Steam Powerat Sea
Isambard Kingdom Brunel (1806 1859)
Best known for the creation of the Great Western
Railway, a series of famous steamships, and
numerous important bridges, hence revolutionising
public transport and modern day engineering.
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Steam Turbines
Today most steam engines have been replaced by
steam turbines or other motive power systems.
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, resulting in lower maintenance
requirements and less wear on the machinery.
Most common use of the type of machine would be
on ships and in the generation of electricity.
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Internal Combustion (IC) Engines
The Internal Combustion Engine is an engine in
which the combustion of fuel and an oxidiser
(typically air) occurs in a confined space called
a combustion chamber.
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Internal Combustion (IC) Engines
Nicolas Otto (1832 1891)
One of the most important landmarks in engine
design comes from Nicolas Otto who in 1876
invented the first practical four-stroke internal
combustion engine called the Otto Cycle Engine.
He also invented the first magneto ignition
system for low voltage ignition in 1884. It is
from his designs that the modern IC engine has
evolved.
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Internal Combustion (IC) Engines
Four Stroke Petrol Engine
Engines based on the four-stroke cycle or Otto
cycle have one power stroke for every four
strokes (up-down-up-down) and are used in cars,
larger boats and many light aircraft. They are
generally quieter, more efficient and larger than
their two-stroke counterparts.
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Internal Combustion (IC) Engines
Two Stroke Petrol Engine
Engines based on the two-stroke cycle use two
strokes (one up, one down) for every power
stroke. Since there are no dedicated intake and
exhaust strokes, an alternative must be used to
scavenge the cylinders. Spark ignition
two-strokes are small and light for their power
output.
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Internal Combustion (IC) Engines
Rudolf Diesel (1858 1913)
A German engineer who in 1892 invented the Diesel
engine basing it on the hot bulb engine and the
ideal cyclic process developed by the young
Frenchman Sadi Carnot (1796 1832). He received
a patent for his engine in 1893. The Diesel cycle
uses compression ignition the fuel ignites upon
being injected into the highly compressed air in
the combustion chamber. By contrast, petrol
engines utilise the Otto cycle, in which fuel and
air are mixed before entering the combustion
chamber and then ignited by a sparking plug.
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Internal Combustion (IC) Engines
Four-Stroke Diesel Cycle
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Internal Combustion (IC) Engines
Felix Wankel (1902 1988)
A German mechanical engineer who was the inventor
of the Wankel Rotary Engine. His engine uses a
rotor instead of reciprocating pistons. This
design delivers smooth high-rpm power from a
compact, lightweight engine.
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Gas Turbine(also know as the Jet Engine)
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Gas Turbine(also know as the Jet Engine)
Jet Engine Operation
A jet engine is an engine that discharges a fast
moving jet of fluid to generate thrust. Jet
engines have evolved from the more general Gas
Turbine cycle which were modelled on the Brayton
constant pressure cycle developed by George
Brayton (1830 1892), an American engineer.
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Measuring Power
Dynamometer
A dynamometer is a machine used to measure torque
and rotational speed from which power produced by
an engine, motor or other rotating prime mover
can be calculated.
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Measuring Power
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Famous Mechanical Engineers/Inventors