Combustion Process and Starting Aids Flashcards
Air is composed of what?
79% nitrogen
21% oxygen
What is the auto ignition temp of diesel?
500 - 700 F
For every 1 psi of pressure developed, the air temp will increase?
2 F
What is minimum compression pressure needed?
300 PSI
Ratio 16:1 will give about 350 PSI
What are the four basic stages of combustion?
Ignition Delay, Flame Propagation, Direct Combustion, Post Combustion
What is combustion knock?
Result of the ignition delay, the longer the delay the greater the knock
Black smoke can be the result of what?
A lack of air for metered amount of fuel
An excess amount of fuel for amount of air engine can max supply
Air pollution
Is the presence of enough contamination in the atmosphere to injure human, plant or animal life
What are three major pollutants from an internal combustion engine?
Hydrocarbons (HC), Carbon monoxide (CO), and Oxides of nitrogen (NOx)
Particulates may include
Lead, Sulphur compounds, and carbon
Oxides of nitrogen are formed when?
When cylinder temperatures exceed about 2500 F
Open Combustion Chamber design
Direct injection. Fuel is injected directly on top of the piston into the heated air. Injection pressures must be 2200 PSI or higher
What are the two common methods of inducing air turbulence?
Shape of piston crown
Intake port design
How is turbulence created in a two stroke engine?
The Inlet ports on the liner are usually cut on an angle to create a spiralling of air
What are advantages of an open combustion chamber design?
Simple design, Good mixing of air and fuel, higher combustion pressures, better fuel economy, easier starting
Disadvantages of an open combustion chamber design?
Fuel must be well atomized and of good quality, requires high pressure fuel injection system, requires fuel to be mixed thoroughly with air
Pre-combustion chamber design
Fuel is injected into pre-combustion chamber. Injection pressures range from 400-2000 PSI. Hardened piston inserts may have to be used to protect piston
What are advantages of a pre-combustion design?
Low emissions, Smooth combustion, requires less atomization of fuel, will burn a wide range of fuel
Intake manifold heaters
Use a coiled heating element to preheat intake air. Commonly used on small displacement engines with open combustion chambers
Glow plugs
heating element used to help increase the temp in a pre-combustion chamber
What are the two types of coolant heaters?
Immersion type
Circulating type
What is the purpose of fuel heaters?
Heat the fuel prior to filtration when ambient temperatures approach the cloud point.
Starting fluids generally contain what two hydrocarbons?
Diethyl ether
Heptane
What 3 factors are necessary for combustion in a diesel engine?
Correct amount of air
Correct amount of fuel at the proper time
Sufficient heat for ignition
What are the 4 methods used to assist in starting a diesel engine at low ambient temperatures?
Heat the intake air
Heat the engine coolant
Heat the engine oil
Heat the fuel
