Conventional engine basics and performance Flashcards
What is the objective of the oil control ring
To scape away oil so it dont fucks up the cylinder
Difference between strokes and revolutions?
strokes is times the piston strokes along the cylinder ether on its way up or down, while revolutions are two strokes. Also note that one cycle is ether one or two cycles
What is break torque? explain
Literately the rotational force (torque) needed to break the rotor compared to stator.
How is engine power defined?
P=torque*angular velocity
What is BMEP?
Break mean effective pressure:
Average effective pressure of all stroke cycles (whether they are two or four cycles)
BMEP=work per cycle/swept volume.
- Note to myself: p=W/V AND F/A!
what is sfc?
It is a good measure of how well the engine is using the available energy in the fuel to
produce useful work.
- Work out/ chemical energy in
Define air/fuel ratio
Mass flow of air / mass flow of fuel
What is the equivalence ratio?
actual air/fuel ratio divided by stoiciometric air/fuel ratio
When is the quivalence ratio lean and when is it rich?
if eq<1 the combustion is lean with excess air. If eq>1 the combustion is rich with incomplete combustion
What is volumetric efficiency?
actual volume of fluid taken in divided by theoretical displacement volume
What do we use flywheels for
Smoothen out rotation. Especially for stroke engines, where the stored inertia in the wheel help get air in the first stroke
What is IMEP
Its like BMEP, but without taking in to account mechanical losses. So BMEP=IMEP*eff_mech
What factors limits engine power?
- Mechanical and thermal loads on components
- Combustion and exhaust emissions
- Air supply and gas exchange
- Mean piston speed (friction)
