Page 301 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

Pm

LAN
Brake horse power (BHP) - The output power of the engine present on the engine flywheel is called Brake
K
x
IHP =
Horsepower (BHP). 4500
This is represented by the following formula
Pm LAN
Pm
2πNT
IHP = 4500 LAN K x K
x
IHP =
BHP =
4500
4500
Here, Pm LAN
IHP = x K
2πNT
N = rotating speed of the crankshaft (in rpm) and 2πNT
4500
BHP =
BHP =
T = generated torque. FHP = IHP 4500 BHP− 4500
Frictional horsepower (FHP) - The power lost due to friction in an engine is called frictional horsepower. The
2πNT
formula is as follows BHP =
4500
FHP = IHP − BHP
BHP
IHP −
FHP =
Mechanical efficiency = BHP x100
Mechanical efficiency - The ratio of brake horse power (BHP) and INDICATED horse power (IHP) in the engine
IHP
is called mechanical efficiency. It is expressed as a percentage. Its formula is as follows
BHP
FHP =
IHP −
BHP
BHP
Mechanical efficiency = /VsPm = W IHP x100
x100

Mechanical
efficiency =
IHP
Indicated mean effective pressure: When we consider an imaginary Pressure which when remaining constant
BHP

x100
Mechanical
efficiency =
will give the same work done for some change in volume like that of actual cycle. than the imaginary constant
Pm =
IHP
W/Vs
Ar
Pm =e
W/Vs the of a
pressure is known as indicated mean effective pressure of cycle. diagram
Area of height =
Work done by IMEP is: Length of the diagram
Pm = W/Vs

the
diagram
Area
Area of height = Area of of the diagram
Vs = swept volume. Area of height = Length of the diagram
of

the
diagram
Length
Fuel consumption: Fuel consumption measures the amount of fuel a car consumes to go a specific distance. It
is expressed in liters per hundred kilometers. Area of the diagram
Area of height =

diagram

Length
of

the
Specific fuel consumption - How much fuel required to generate 1 KW OR 1 BHP power for 1 hour
Unit of SFC-- g/kWh or g/BHP h
Type of SFC
1 ISFC - Indicated specific fuel consumption
2 BSFC - Brake specific fuel consumption
Measurement of Thermal efficiency, Volumetric efficiency, Relative efficiency, Air consumption, Lubricating
oil consumption
Measurement of Thermal Efficiency: Thermal efficiency is a measure of how well an appliance converts input
heat energy into useful work or output energy. It is calculated as a percentage using the formula. It applies to
engines, power plants, and other systems that involve converting heat into work.
For example: In the context of engines, it refers to the ratio of the mechanical work produced by the engine to the
heat energy contained in the fuel consumed.
Measurement of Volumetric Efficiency: Volumetric efficiency is a measure of how effectively an engine can
draw and utilize the air-fuel mixture into its combustion chamber compared to its theoretical maximum. The
theoretical maximum volume is determined by engine displacement, atmospheric pressure and temperature.
Actual conditions during engine operation, however, affect how much air-fuel mixture can actually be drawn into
the combustion chamber.
Measurement of Relative Efficiency: “Relative efficiency” which can be used in different contexts, but refers
to comparing the efficiency of a process to another. Relative efficiency may refer to comparing the efficiency of
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CITS : Automotive - Mechanic Diesel - Lesson 87