(1) aunit1l3terminologia del rendimiento

7/27/2019 (1) Aunit1l3terminologia Del Rendimiento

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Lesson 3: Engine Performance Terminology

Objective:

The student will be able to define essential engine performance

terminology and calculate engine displacement, compression ratio,

and horsepower.

References:

Glossary of Terms LEXQ8150

Introduction:

To understand diesel engine design and performance, it is necessary

to know the terminology and math calculations that apply to diesel

engines.


2/21

Unit 1 1-3-2 Engine Fundamentals

Lesson 3

This presentation will review engine performance and engine

performance terminology.

Fig. 1.3.1

There are many factors that determine the performance of an engine.

The operating conditions that an engine is exposed to and the specific

application an engine is placed in can affect the performance of the

engine. Many of the determining factors for performance, however,

are determined by the manufacturer of the engine.

Some of the basic specifications that a manufacturer makes on an

engine that affect performance of the engine are:

Bore

StrokeDisplacement

Compression Ratio

The performance of an engine is typically rated by comparing power

output and/or efficiency of the engine. These evaluations can be

measured in several different ways. The basis for these

measurements and the manufacturers specifications must be known

in order to better understand the effects that all of these factors and

measurements have on engine performance.


3/21


Lesson 3

BDC

TDC

STROKE

BORE

CRANKSHAFT

AT TDC

CRANKSHAFT

AT BDC

Fig. 1.3.2

Top Dead Center (tdc)

Top dead center (tdc) is a term used to describe the position of thepiston when the piston is at its highest point in the cylinder. This

occurs when the crankshaft and the connecting rod are fully extended

and straight with one another. Many events in the operation of the

engine are identified by crankshaft position, measured in degrees

either before or after tdc.

Bottom Dead Center (bdc)

Bottom dead center (bdc) is a term used to describe the position of

the piston when the piston is at its lowest point in the cylinder. This

occurs when the crankshaft and the connecting rod are fully retractedand straight with one another.

Bore (B)

Bore is a term used to describe the diameter of a single cylinder in an

engine. Bore is typically measured in millimeters or inches.

Stroke (L)

Stroke is a term used to describe the distance that a piston travels in

the cylinder of the engine. The stroke is measured as the difference

between the position of the piston at BDC to TDC. The amount of

stroke is determined by the design of the crankshaft. The stroke is

equal to exactly twice the throw of the crankshaft. Stroke is typically

measured in millimeters or inches.


4/21


Lesson 3

17 TO 1

DIESEL ENGINE

Fig. 1.3.3

Engine Displacement

The bore, the stroke, and the number of cylinders all determine the

displacement of an engine. The displacement of an engine is simply

the amount of volume displaced by all cylinders in an engine during

one complete rotation. The displacement of an engine can becalculated using the following formula:

Displacement = x r2 x L x n

Where...

= 22/7

r2 = radius x radius

radius = 1/2 bore

L = stroke

n = number of cylinders in the engine

Compression Ratio

The compression ratio of an engine is determined by the cylinder

displacement and the combustion chamber volume. In order to

calculate the compression ratio use the following formula:

CR = Total Cylinder Volume / Combustion Chamber Volume

Typical compression ratios of diesel engines range from 11:1 to

22:1. This is significantly higher than the compression ratio of a

typical gasoline engine. Diesel engines utilize higher compression

ratios to increase the pressure within the combustion chamber.

Higher pressures will cause an increase in the temperature of the air

and fuel in the combustion chamber. This high temperature

(approximately 1000F) will cause the diesel fuel to ignite without

the use of a spark plug.


5/21

Work

Work is defined as a force that is applied over a distance.

W = F x D

Power

Power is defined as the rate at which work is performed

P = F x D / t

or

P = W / t

Where t is the time that the work is performed in.

The standard measure of power in the metric system is the kilowatt

(kW), and in the english system the standard measure of power is the

horsepower (HP).

1 HP = 0.746 kW

1 kW = 1.340 HP

The term horsepower was originally derived by James Watt, a

scottish inventor. Watt observed the ability of a horse in coal mine

hoisting coal. He defined 1 HP to be equal to the ability of a horse to

raise 33,000 lb of coal a distance of 1 ft in 1 minute.

There are several different types of power that are often discussed.

Indicated horsepower (IP) is the power that an engine is

theoretically able to produce. This is found by multiplying the

displacement of the engine by the mean effective pressure in the

cylinder in pounds per square inch and dividing it by 33,000.

Brake engine horsepower (BP) is the power that is found by

physically testing an engine on a dynamometer. A dynamometer

is a device that is coupled to an engine for the purpose ofmeasuring the torque and the horsepower output of the engine.

Friction power (FP) is the power that an engine requires in order

to overcome the frictional losses of bearings, gears, and other

moving parts of the engine. Friction power increases as the size

and/or the speed of an engine increases.

BP = IP - FP


Lesson 3


6/21

Torque

When the engine is running, the combustion that takes place causes

the pistons to move downward in the cylinder. This downward piston

motion pushes on the connecting rods and causes the crankshaft to beturned. The resulting twisting force produced by the crankshaft is

called torque.

The torque and the horsepower that an engine produces are related to

one another with the following equation:

HP = T x RPM / 5252

NOTE: This formula can not be used with metric units. Convert

the metric units to english units before performing the

calculation.

Where...

T = Torque (measured in ft lb)

5252 = 33,000 / 2 (constant)

The constant of 5252 is derived by dividing the 33,000 lb in Watts

horsepower formula by the angular value of one rotation of the

crankshaft in radians, 2.

Torque is measured in foot-pounds (ft lb) in the english system and inNewton-meters (Nm) in the metric system.

1 ft lb = 1.3558 Nm

1 Nm = 0.7376 ft lb

Friction

A certain amount of force is required in order to slide the surfaces of

two objects against one another. The resistance to this motion is

called friction. As the load is increased, friction is increased. For

example it requires more effort to slide a heavy object than it does to

slide a light object. The condition of the two surfaces in contact also

makes a difference. This is why the lubrication system in an engine

is so important. The oil film between the moving parts of an engine

keep the friction between the two surfaces very low. This not only

gives the engine a long service life, but also creates less drag on the

engine, reducing the amount of frictional power. This allows the

engine to produce more brake power.


Lesson 3


7/21

Inertia

Sir Isaac Newtons first law of motion states that an object in motion

tends to stay in motion and an object at rest will tend to stay at rest,

until acted upon by an outside force. This phenomenon is due toobjects possessing inertia. The amount of inertia an object has is

directly proportional to the amount of mass that the object has. For

example a car has more inertia than a bicycle. This is why it is

harder to move or stop a car than a bicycle.

Efficiency

The efficiency that a particular engine has is expressed as a

percentage of the actual power to the theoretical power of an engine.

The actual power produced by an engine is always less than the

theoretical power. There are several ways to describe the efficiencyof an engine.

Volumetric efficiency is defined as how capable an engine is of

filling the cylinder with air on the intake stroke compared to the

cylinder being completely filled with air at atmospheric pressure.

Because air must be sucked into the cylinder with the downward

motion of the piston, the engine is never able to fill the cylinder

100%.

Brake power is the amount of usable power that an engine

actually produces. Indicated power is the amount of theoreticalpower that an engine should be able to produce. Mechanical

efficiency is the ratio of brake power to indicated power.

BP / IP = Mechanical Efficiency

Thermal efficiency is the degree to which an engine is able to

successfully convert the energy in the fuel into heat energy to

cause the pistons to turn the crankshaft.

Fuel efficiency is defined in several different ways. The most

common of which is kilometers per liter (km/L) or miles per

gallon (mpg), which would be used to describe the fuel efficiencyof an engine in an over the road application such as in a truck.

Fuel efficiency for marine or industrial applications may be

expressed in liters per hour (Lph) or gallons per hour (gph) at

rated speed.

Fuel efficiency may also be expressed in brake specific fuel

consumption (bsfc). Bsfc is defined as the amount of fuel used

per unit of power and time. The bsfc of an engine is expressed in

either g / (kW hr) or lb / (hp hr).


Lesson 3


8/21


Lesson 3

12,000 FT.9.3 PSI

8,000 FT.

10.9 PSI

4,000 FT.

12.7 PSI

3657 M.64.12 kPa

2438 M.

75.15 kPa

1219 M.

87.50 kPa

101.35 kPa SEA LEVEL SEA LEVEL 14.7 PSI

EARTH'S SURFACE

WEIGHT OF

AIR ONEARTH'SSURFACE

Fig. 1.3.4

As an example, due to increased pressure at sea level the air is more

dense than the air on top of a mountain. The dense air allows for

more air molecules to flow into the cylinder. This allows for the fuel

to be more completely burned in a diesel engine, which produces

more power. This is why engines perform better in lower altitudes,

the air is more dense.

Ambient air temperature also plays a role in how much air can flow

into an engine. The lower the temperature of the air, the more dense

the charge of air is that enters the cylinders. The greater the density

of the air, the more power that can be produced efficiently in theengine.

Humidity is also an important factor in diesel engine combustion.

Humidity is a relative measure of the amount of moisture that is

suspended in the air. The suspended moisture has a cooling effect on

the air as it enters the engine. Therefore, the greater the humidity of

the air, the colder the air, the denser the air, the more power that can

be produced efficiently in the engine.

Atmospheric Conditions

In order to produce the desired levels of power, diesel engines require

a large volume of air. Therefore the atmospheric pressure, the

ambient air temperature, and the relative humidity of the air play alarge role in the performance characteristics of the engine.

It is the atmospheric air pressure that is present that forces the air into

the engine. Atmospheric pressure is the pressure that is exerted on

the earths surface due to the weight of the atmosphere (the air

surrounding the earth). Atmospheric pressure is greatest at sea level

because there is more air above the air at sea level than there is above

the air at the top of a mountain. Refer to figure...


9/21

Unit 1, Exercise 1.3.1

Define the following terms:

TDC - Top Dead Center: The highest position that a piston reaches in the cylinder.

BDC - Bottom Dead Center: The lowest position that a piston reaches in the cylinder.

Bore: The diameter of each cylinder in an engine.

Stroke: The distance travelled by the piston from BDC to TDC.

Displacement: The circular area of one cylinder multiplied by its stroke multiplied by the

number of pistons. This is also sometimes referred to as the swept volume.

Compression Ratio: The ratio of total cylinder volume to combustion chamber volume.

Work: A force applied over some distance.

Power: The rate at which work is performed.

Horsepower: A unit of standard measure for power in the english system.

Kilowatt: A unit of standard measure for power in the metric system.

Torque:The amount of twisting force that is produced by an engine.

Indicated Horsepower: The amount of power that an engine is theoretically able to produce.

Brake Engine Horsepower: A measurement of the actual power that is available for useful work

from an engine.

Dynamometer: A device used to measure the torque and horsepower output of an engine.

Mechanical Efficiency: The ratio of brake power to indicated power. Gives an idea of how

much power is lost due to friction in the engine.

Thermal Efficiency: The degree to which an engine is able to convert the energy in the fuel into

heat energy to cause the pistons to turn the crankshaft.

Volumetric Efficiency: The capability of an engine is of filling the cylinder with air on the intake

stroke compared to the cylinder being completely filled with air at

atmospheric pressure.

Unit 1 1 Engine Fundamentals

Lesson 3, Exercise 1.3.1


10/21


11/21



Write the equations for calculating the following:

Displacement: Displacement = x r2 x L x n

Where...

= 22/7

r2 = radius x radius

radius = 1/2 bore

L = stroke

n = number of cylinders in the engine

Horsepower: HP = T x RPM / 5252

Using the Glossary of Terms, define the following:

Force: The action of one body on another tending to change the state of motion of the body

acted upon.

Heat: Form of energy, the addition of which, causes substances to rise in temperature; energy

associated with random motion of molecules.

British Thermal Unit (BTU): The amount of heat required to raise 1 lb of water from ice to

water at standard atmospheric pressure.

Brake Mean Effective Pressure (BMEP): Mean effective pressure acting on the piston which

would result in the given brake horsepower output, if

there were no losses due to friction, cooling, and

exhaust. This is equal to the mean indicated pressure

multiplied by the mechanical efficiency of the engine.


12/21



Unit 1, Exercise 1.3.1

Define the following terms:

Bore:

Stroke:

TDC - Top Dead Center:

BDC - Bottom Dead Center:

Displacement:

Compression Ratio:

Work:

Atmospheric Pressure:

Power:

Mechanical Efficiency:

Horsepower:

Thermal Efficiency:

Kilowatt:

Indicated Horsepower:

Friction:

Torque:

Brake Engine Horsepower:

Dynamometer:

Volumetric Efficiency:

Inertia:

Fuel Efficiency:


13/21


Lesson 3, Exercise 3.1

Write the equations for calculating the following:

Displacement:

Horsepower:

Using the Glossary of Terms, define the following:

Force:

Heat:

British Thermal Unit (BTU):

Brake Mean Effective Pressure (BMEP):


14/21

Unit 1- 1 Engine Fundamentals

Instructor Copy Quiz 1.3.1

CATERPILLAR ENGINE FUNDAMENTALS

Unit 1 Quiz

Circle the best answer or fill in the blanks. Name .

1. The crankshaft in a Caterpillar 3406B is:

A. hardened at the journals only

B. totally hardened

2. Which engines require MSHA certification?

A. MarineB. Underground Mining

C. On-Highway Truck

3. Which of the following Caterpillar on-highway truck engines are considered medium duty

(mid-range) class?

A. C-10

B. 3306C

C. 3126B

D. 3406C

4. What three factors are necessary to create combustion?

air fuel heat

5. How does the 4 stroke diesel engine combustion process differ from 4 stroke gasoline

engines?

Ignition process - diesel uses compression, gasoline uses spark to ignite fuel

6. Name the 4 cycles of Caterpillar diesel engine operation.

intake compression

power exhaust


15/21



7. Four strokes of the piston equal how many revolutions of the crankshaft?

A. 1

B. 2

C. 4D. 8

8. During the four-stroke cycle, the piston is moving toward TDC (Top Dead Center) during

what two strokes?

A. Compression and exhaust

B. Intake and power

C. Intake and exhaust

D. Compression and power

9. What does this formula represent?

RPM x Torque

5252

A. BTU

B. % Torque Rise

C. Horsepower

D. Thermal Efficiency

10. 317 kilowatts is equivalent to how many horsepower?

A. 400

B. 425

C. 236

11. In a Caterpillar 3406 engine, when piston #1 is at TDC compression, piston #6 is at:

TDC exhaust

12. Horsepower is defined as:

A. work done in a given period of time.

B. twisting effort of the crankshaft in an engine.

C. the displacement of an engine in liters.

D. the energy derived from burning dried horse manure


16/21



13. Engine displacement is defined as:

A. weight of the engine.

B. length of the engine when it is installed.

C. total volume that is displaced by all pistons making one stroke each.D. moving the engine from one place to another.

14. Compression ratio is defined as:

A. ratio of compression pressure to firing pressure.

B. ratio of volume in a cylinder with the piston at Bottom Dead Center compared to

volume at Top Dead Center.

C. ratio of crankcase pressure to atmospheric pressure.

D. ratio of turbocharger boost pressure to exhaust backpressure.

15. Explain the difference between "Flywheel Horsepower" and "Wheel Horsepower".

Flywheel horsepower is measured at the flywheel, wheel horsepower is measured at the

wheels of a vehicle (drivetrain losses will make wheel hresepower less)

16. What section of a Service Manual has step-by-step procedures for setting intake and

exhaust valves on a Caterpillar engine?

Testing and adjusting

17. An industrial engine application that requires the engine to operate at rated load and speed

up to 100% of the time is considered:

A. A Rating

B. B Rating

C. C Rating

D. D Rating

E. E Rating

18. Which components in a diesel engine convert reciprocating motion to rotary motion?

A. Camshaft and crankshaft

B. Connecting rod and crankshaft

C. Piston and crankshaft

D. Crankshaft and flywheel


17/21




for a short time is considered:

A. A Rating

B. B RatingC. C Rating

D. D Rating

E. E Rating

20. A "parent bore block" is:

A. a cylinder block with removable wet cylinder liners.

B. usually used in heavy duty engine designs.

C. a cylinder block with cylinders bored by your father.

D. a cylinder block where the cylinders are bored directly into the cylinder block

material.


18/21


Student Copy Quiz 1.3.1

CATERPILLAR ENGINE FUNDAMENTALS

Unit 1 Quiz

Circle the best answer or fill in the blanks. Name____________________________

1. The crankshaft in a Caterpillar 3406B is:

A. hardened at the journals only

B. totally hardened

2. Which engines require MSHA certification?

A. MarineB. Underground Mining

C. On-Highway Truck

3. Which of the following Caterpillar on-highway truck engines are considered medium duty

(mid-range) class?

A. C-10

B. 3306C

C. 3126B

D. 3406C

4. What three factors are necessary to create combustion?

________________ _________________ _________________

5. How does the 4 stroke diesel engine combustion process differ from 4 stroke gasoline

engines?

________________________________________________________

________________________________________________________

6. Name the 4 cycles of Caterpillar diesel engine operation.

_____________________ _____________________

_____________________ _____________________


19/21



7. Four strokes of the piston equal how many revolutions of the crankshaft?

A. 1

B. 2

C. 4D. 8

8. During the four-stroke cycle, the piston is moving toward TDC (Top Dead Center) during

what two strokes?

A. Compression and exhaust

B. Intake and power

C. Intake and exhaust

D. Compression and power

9. What does this formula represent?

RPM x Torque

5252

A. BTU

B. % Torque Rise

C. Horsepower

D. Thermal Efficiency

10. Define Torque Rise in a diesel engine.

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

11. In a Caterpillar 3406 engine, when piston #1 is at TDC compression, piston #6 is at:

______________________________________________________________

12. Horsepower is defined as:

A. work done in a given period of time.

B. twisting effort of the crankshaft in an engine.

C. the displacement of an engine in liters.

D. the energy derived from burning dried horse manure


20/21



13. Engine displacement is defined as:

A. weight of the engine.

B. length of the engine when it is installed.

C. total volume that is displaced by all pistons making one stroke each.D. moving the engine from one place to another.

14. Compression ratio is defined as:

A. ratio of compression pressure to firing pressure.

B. ratio of volume in a cylinder with the piston at Bottom Dead Center compared to volume

at Top Dead Center.

C. ratio of crankcase pressure to atmospheric pressure.

D. ratio of turbocharger boost pressure to exhaust backpressure.

15. Explain the difference between "Flywheel Horsepower" and "Wheel Horsepower".

_____________________________________________________________

_____________________________________________________________

16. What section of a Service Manual has step-by-step procedures for setting intake and exhaust

valves on a Caterpillar engine?

_____________________________________________________________


up to 100% of the time is considered:

A. A Rating

B. B Rating

C. C Rating

D. D Rating

E. E Rating

18. Which components in a diesel engine convert reciprocating motion to rotary motion?

A. Camshaft and crankshaft

B. Connecting rod and crankshaft

C. Piston and crankshaft

D. Crankshaft and flywheel


21/21




for a short time is considered:

A. A Rating

B. B RatingC. C Rating

D. D Rating

E. E Rating

20. A "parent bore block" is:

A. a cylinder block with removable wet cylinder liners.

B. usually used in heavy duty engine designs.

C. a cylinder block with cylinders bored by your father.

D. a cylinder block where the cylinders are bored directly into the cylinder block material.

(1) aunit1l3terminologia del rendimiento

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