Heat Engines and Combustion Types

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Questions and Answers

What is the primary function of an engine?

To convert thermal energy into nuclear energy

To convert mechanical energy into heat energy

To convert heat energy of fuels into mechanical energy (correct)

To convert electrical energy into chemical energy

Which type of engine is a steam engine?

External Combustion Engine (correct)

Internal Combustion Engine

Heat Engine

Combustion Engine

What is the purpose of a piston ring?

To reduce the cylinder volume

To connect the piston to the crankshaft

To increase the compression ratio

To form a seal between the piston and the cylinder wall (correct)

What is the classification of a tractor with both wheels and tracks?

Combination wheel type and track type Signup and view all the answers

What is the term for the distance the piston travels in one direction?

Stroke Signup and view all the answers

What is the ratio of cylinder volume to clearance volume?

Compression ratio Signup and view all the answers

What is the purpose of the crankcase?

To lubricate the engine's components Signup and view all the answers

What is the application of internal combustion engines in agriculture?

For all types of agricultural power applications Signup and view all the answers

What is engine efficiency a measure of?

The ability of an engine to convert fuel into useful work Signup and view all the answers

How many events take place inside the combustion chamber in the operation of internal combustion engines?

Four events Signup and view all the answers

What is the formula to calculate the efficiency of an ideal Otto cycle?

e = 1 -- ( V<del>C</del> / V<del>B</del> ) ^k-1^ Signup and view all the answers

Which type of engine gives a higher theoretical efficiency?

Otto cycle engine Signup and view all the answers

Why is the compression ratio of Otto-cycle engine limited?

Due to the fuel characteristics Signup and view all the answers

How many movements of the piston are required to complete the cycle in a two-stroke cycle engine?

Two movements Signup and view all the answers

Which type of engine typically uses higher compression pressures than Otto-cycle engine?

Diesel engine Signup and view all the answers

How many power strokes are there in a four-stroke cycle engine per two revolutions of the crankshaft?

One power stroke per 2 rev. of crankshaft Signup and view all the answers

What is the characteristic of the valve mechanism in a small engine?

absent Signup and view all the answers

What is the fuel consumption of a large engine compared to a small engine?

more Signup and view all the answers

How does the stability of rpm vary with the size of the flywheel?

high with large flywheel Signup and view all the answers

How does the lubrication system work in a small engine?

independent of oil circuit Signup and view all the answers

What is the characteristic of oil consumption in a small engine?

little Signup and view all the answers

What is the characteristic of the self-weight and size of a small engine?

light and small Signup and view all the answers

Study Notes

Heat Engines

Heat engines are mechanical devices that convert heat energy of fuels into mechanical energy.
External combustion engines (ECE) ignite and burn fuel outside a cylinder, and the heat energy is applied indirectly to a piston by an intermediate medium, usually water vapor.
Steam engines are an example of external combustion engines.
Internal combustion engines (ICE) ignite and burn fuel inside a cylinder, and the resulting explosion causes an instantaneous application of pressure to a piston.

Applications of Internal Combustion Engines

Used as stationary power sources for milling, grinding, water pumping, generation of electricity, etc.
Used as power units of portable farm equipment such as sprayers, threshers, and self-propelled machines such as tractors, combines, and harvesters.

Classification of Tractors

2-wheel tractor (hand tractor)
Compact 4-wheel tractor
Combination wheel type and track type
Tract type or crawler
Combination wheel type and tract type

Main Engine Components

Cylinder
Piston rings
Cylinder block
Piston pin
Cylinder head
Valves
Crankcase
Piston
Intake manifold
Exhaust manifold
Connecting rod
Crankshaft
Flywheel

Physical Nomenclature

Bore (d): the diameter of the engine cylinder
Stroke (l): distance the piston travels in one direction
Piston displacement (Pd): volume displaced by the piston in one stroke
Clearance volume (Cv): the space inside the cylinder when the piston is at top dead center position
Cylinder volume: the sum of piston displacement and clearance volume (Pd + Cv)
Compression ratio (Cr): ratio of cylinder volume to clearance volume
Engine efficiency: a measure of the ability of an engine to convert fuel into useful work

Engine Cycles and Principles of Operation

Four events repeatedly take place inside the combustion chamber in a definite order: intake, compression, power, and exhaust.
Classification of engines: 4-stroke cycle and 2-stroke cycle engines.

Comparison of 4-stroke Cycle and 2-stroke Cycle Engines

4-stroke cycle engines require four movements of the piston to complete the cycle.
2-stroke cycle engines require two movements of the piston to complete the cycle.
4-stroke cycle engines have smaller power, require valve mechanism, have complicated construction, consume less fuel, and have good durability.
2-stroke cycle engines have larger power, do not require valve mechanism, have simple construction, consume more fuel, and have good durability.

Types of Engines

Four-stroke cycle spark ignition engine
Four-stroke cycle compression ignition engine
Two-stroke cycle spark ignition engine
Two-stroke cycle compression ignition engine

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Description

Learn about the difference between external and internal combustion engines, and how they convert heat energy into mechanical energy.