00:01
Hello students we'll start our video.
00:05
To solve this question we'll have to make a graph.
00:08
So this is our diagram.
00:11
This is pressure volume.
00:15
This is pavc, rvvc.
00:20
This is ignition, here compression, exhaust.
00:25
This is intake and here it is expansion.
00:29
This is our positive work and this whole is negative work.
00:33
This is expansion ratio, this is compression ratio and this whole is full load.
00:40
So now we'll be talking about heat losses.
00:45
In the theoretical cycle, heat loss is considered as null.
00:52
On the other hand, in real auto cycle, heat losses are quite sensitive.
01:00
One of the characteristics of thermal engine is that cylinder is cold, to ensure good functioning of the piston.
01:09
The drawback is that the certain heat part of fluid is transmitted to the walls.
01:16
The line of compression and expansion are not therefore adiabatic, but polytropic with an exponent n different from k, as the fluid experiences a loss of heat energy and it is evidently for expansion, n is greater than k and for compression.
01:44
So, non -instaneous combustion.
01:49
In the theoretical cycle, it is assumed that combustion taking place at the constant volume, it is therefore instantaneous in real auto cycle.
02:00
On the contrary, combustion lasts a certain time.
02:04
If the ignition takes place exactly at the pms, the combustion will occur while the piston moves away from the set point and the value of pressure will be lower than expected with the corresponding loss of useful work.
02:22
It is therefore necessary to anticipate the ignition of gasoline so that the combustion may take place.
02:33
For the most part, when the piston is in the vicinity of the pms, it produces rounding of theoretical line 2 to 3 of introduction of thermal heat or thermal energy.
02:49
This yielding of curve implies a loss of useful work represented by the area b.
02:56
However, this loss of work results in a quantity that is much smaller than which would be had.
03:04
Without advancing the ignition.
03:07
Opening time to exhaust valve in the theoretical cycle, auto cycle, it is also assumed that the subtraction of heat occurred instantaneously in the pmi...