Terms in this set (89)
rate of doing work
heat transformed into energy
amount of work done
power developed by an internal combustion engine
power left after all friction is lost
formula for total amount of indicated horsepower an engine to produce
PLANK over 33,000
how is pressure obtained?
by admitting a mixture of vaporized gasoline and air into a cylinder, compressing and burning the mix
how to improve the pressure?
higher octane fuel, supercharging and improved scavenging
mean effective pressure, average pressure within the cylinder during the entire power stroke, from TBC to BDC
brake mean effective pressure, mep available to produce the netpower delivered at the propeller shaft
what are the types of combustion engines?
horizontally opposed, radial and inline
explain a horizontally opposed engine
flat, less drag, cylinders are across eachother working on the same crankshaft
explain a radial engine
"barell shape", odd numers of cylinders working in different orders, easy to maintain
explain an inline engine
cylinders are arranged side by side, each piston works on an individual crank throw, up to 6 cylinders only
converts reciprocating motion of the piston into rotation and transmits power from the piston to drive the propeller
diameter inside the cylinder
distance the piston moves from one end to the other (TBC-BDC)
engine turns at higher speed than the propeller, makes greater power
turns drive oil pump, magneto's, generators and dynamo's
holds all auxiliary gears, located at the rear of the engine
what are the 4 strokes
intake, compression, power and exhaust
air is picked up and mixed with fuel
piston moves up, with both valves closed
volume in cyl above piston when it is at the bottom of the compression stroke compared to the volume when it has moved up
mix is fired by a spark plug, the expanding gases create pressure which drives the piston down
piston moves up from the bottom pushing the gases out
explain the 2 stroke cycle
upwards: charging the crakcase, compression of the fuel charge and ignition
exhaust: transfer of fuel to the cylinder
provides fuel and air intake by taking in exhaust starting a repeating cycle. Found behind the engine
when forced induction is used at high altitudes to make up the defficiancy in the pressure due to lower density of the air
compresses fuel and air mixture, can increase the power at low altitudes
provide greater area of metal to absorb heat and let air through to coll it down
what are the functions of oil?
cooling, sealing, lubricating and flushing
how does sealing work
seals between piston rings and cylinder walls preventing loss of power and excessive oil consumption
what are the 2 methods of lubrication?
force feed and splash
under pressure (dry sump)
churned into mist (wet sump)
where is oil contained in a dry sump engine?
in a different tank
requirements of good oil?
viscosity, high flash point, low carbon content and low pour point
resistance to flow, ( too high will cause too much pressure)
high flash point
temperature beyond which a fluid will ignite
good resistance to deterioration and the formation of lacquer and carbon deposits
low pour point
temperature at which fluid solidifies
types of additives
detergents, oxidation, anticorrosion and pour point depressents
pour point depressents
lowers pour point
what will happen if oil gets too hot?
viscosity will be impaired
what would happen if oil is too cold?
it wont flow
thins the oil with raw fuel right before engine is stopped in order too lower viscosity so that high cranking of the torque wont happen
high cranking of the torque
resistence to turning
what is the problem with dilution systems?
fuel pump fuel system
engine drive fuel pump supplies pressure that keeps fuel flowing to the engine
gravity feed fuel system
fuel tanks are mountain on the wings
fuel selector valve
pilot chooses from what tank he wants fuel from
pump on instrument panel to put oil into engine before starting (only in cold). Too much will drown the engine
natural gas limit
antiknock value of fuel (octane higher than 100)
grade 100 LL
what will happen if you use an octane mixture too high?
how can antiknock be fixed
by adding lead
inability for fuel to burn slowly, cause by lean mixture, incorrect fuel or overheating
hot carbon particles inside cylinders
gas vaporizes and block fuel lines
1 to 18
best power mix
1 to 14
1 to 15
lowest fuel consumption
1 to 18
leanest running mix
1 to 20
too rich a mixture
fouled spark plugs and combustion chamber
too lean a mixture
rough engine operation, detonation and overheating
allows air in (unfiltered) and controls mixture
moist air, ice block fuel line, loss of power
what are the 2 ways carb icing is formed
1) drop in temperature as heat is taken from the air 2) cooling due to the low pressure area in the carburator
generates low tension current, transforms it into high tension and distributes current to individual spark plugs
distance (feet) a propeller travels forward in one revolution
cruise, high pitch, low RPM
take off and landing, low pitch, high RPM
fixed pitch propeller
adjustable pitch propeller
only adjustable before flight
controllable pitch propeller
adjustable during flight
constant speed propeller
adjusts to RPM
what are the 2 ways you can change the pitch?
mechanically and hydraulically
what are some engine instruments?
oil pressure, oil temp, cylinder head temp, carburetor air temp, outside air temp, tachometer, manifold pressure
what does the tachometer read?
revolutions per minute
what is the manifold pressure reading?
pressure of fuel/air mixture