1. General Instructional Support For All Fuels
The combustion processes and control strategies employed by the gaseous fueled
engine differ significantly from the diesel or gasoline engine. Instruction
in the following should give the student a foundation of knowledge that will
enhance their ability to diagnose and repair these engines.
Instruction should include:
1. Physical properties and comparison of hydrocarbon fuels
- molecular structure
- vapor density
- auto-ignition temperature
- octane number
- heat of combustion in Btu/lb. (high and low heating values)
- density
- energy density (Btu/gallon)
- flammability limits
- flash points
- boiling points
2. Gas Laws
- differential pressure theories
- mass/volume
- absolute pressures
- pressure measurements units - e.g. psia; psig; in.Hg; in.H2O, etc.
- metric equivalents
3. Combustion process and factors that influence combustion
- exhaust constituent formation (chemistry of combustion)
- comparison of the Otto cycle to diesel
- comparison of stoichiometric A/F ratio to lean-burn
- diesel verses dual-fuel (e.g. diesel and natural gas or LPG)
- theoretical air/fuel ratios of different automotive fuels (stoichiometry)
- surface ignition verses pre-ignition
- auto-ignition/knock
- ignition systems
4. Air fuel metering strategies/systems
- mechanical fuels systems
- speed density systems
- mass air flow sensors
- gas mass sensors
- actuators
- oxygen sensors - standard and wide range
- air induction strategies
- charge air systems
- closed loop/feedback system
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