any more information please contact my email id: radhebharvad508@gmail.com

1. Reciprocating Engine
Theory Of Operation

2. Reciprocating Engine Theory Of
Operation
• Engine Operating Principles

3. Reciprocating Engine Theory Of
Operation
• Operating Cycles
• Two-Stroke
– Requires only one upstroke and one downstroke of
the piston to complete the required series of events
in the cylinders.
– Completes the operating cycle in one revolution of
the crankshaft.
• What are the sequence of events that take
place to convert the chemical energy into
mechanical energy?

4. Reciprocating Engine Theory Of
Operation
• Intake
• Compression
• Ignition
• Power
• Exhaust

5. Reciprocating Engine Theory Of
Operation
• Two-Stroke

6. Reciprocating Engine Theory Of
Operation
• Four-stroke
• Four strokes required
to complete the events.
• Two revolutions of the
crankshaft (720°) are
required to complete
the four strokes.

7. Reciprocating Engine Theory Of
Operation
• Engine Power And Efficiency
– Work = Force x Distance
– Horsepower = ft-lb per min or ft-lb per sec
33,000
550

8. Reciprocating Engine Theory Of
Operation
• Piston Displacement
• The greater the piston displacement the greater
the horsepower an engine will develop.
• The volume displaced by a piston is its
displacement.
• Expressed in cubic inches.

9. Reciprocating Engine Theory Of
Operation
• Piston Displacement
• PD = Area of cross section of cylinder
multiplied by total distance the piston moves.
• V=AxH

10. Reciprocating Engine Theory Of
Operation
• Compression Ratio
• Comparison of the volume of space in a
cylinder when the piston is at the bottom of the
stroke to the volume of space when the piston
is at the top of the stroke.
• The higher the engine compression ratio, the
higher the engine efficiency (horsepower
output) will be.

11. Reciprocating Engine Theory Of
Operation
• Manifold Absolute Pressure (MAP)
• Average absolute pressure of the fuel/air
charge in the intake manifold.
• Measured in units of inches of mercury (Hg).
• Dependent mostly on ambient air pressure,
engine speed, and throttle setting.
• Supercharging increases MAP.

12. Reciprocating Engine Theory Of
Operation
• Compression Ratio & Manifold Pressure.
• Determines the pressure in the cylinder when
both valves are closed.
• Pressure of charge before compression is
determined by the manifold pressure.
• Pressure at the height of compression is
determined by manifold pressure times the
compression ratio.

13. Reciprocating Engine Theory Of
Operation
• Absolute & Gauge Pressure.
• Absolute Pressure
– Identifies the pressure measurement as one
that is based on a comparison of the
pressure in the manifold with pressure at
absolute zero.
• Gauge Pressure
– Compares the pressure being measured
against ambient pressure.

14. Reciprocating Engine Theory Of
Operation
• Indicated Horsepower
• Horsepower calculated from the indicated
mean effective pressure and the other factors
which affect the power output of an engine.
• The power developed in the combustion
chamber without reference to the friction
losses within the engine.

15. Reciprocating Engine Theory Of
Operation
• Brake Horsepower (BHP)
• The power delivered from the engine to the
propeller for useful work.
• Total horsepower lost due to friction is
subtracted from indicated horsepower.
• The measurement of an engine’s BHP involves
the measurement of torque.
– Torque = Force times distance

16. Reciprocating Engine Theory Of
Operation
• Friction Horsepower
• Indicated horsepower minus brake
horsepower.

17. Reciprocating Engine Theory Of
Operation
• Friction And Brake Mean Effective Pressure
• Indicated Mean Effective Pressure
– Pressure used to create frictionless power.
• Friction Mean Effective Pressure
– The pressure used to overcome internal
friction.
• Brake Mean Effective Pressure
– The pressure used to produce useful work.

18. Reciprocating Engine Theory Of
Operation
• Thrust Horsepower
• The result of the engine and propeller working
together.
• The ratio of thrust horsepower and brake
horsepower delivered to the propeller shaft will
never be equal.
• Determines the performance of the enginepropeller combination.

19. Reciprocating Engine Theory Of
Operation
• Efficiencies
• Thermal Efficiency
– The ratio of useful work done by an engine
to the heat energy of the fuel it uses,
expressed in work or heat units.
• Mechanical Efficiency
– The ratio that shows how much of the
power developed by the expanding gases in
the cylinder is actually delivered to the
output shaft.

20. Reciprocating Engine Theory Of
Operation
• Efficiencies
• Volumetric Efficiency
– A comparison of the volume of fuel/air
charge inducted into the cylinders to the
total piston displacement of the engine.