cairo 2nd petrol lecture 8
TRANSCRIPT
![Page 1: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/1.jpg)
Mechanical EngineeringThermodynamics
Lecture (8) Internal Combustion Engines (ICE)
Lecturer : Dr. Esmail Bialy
2nd year Petrol dept.2011-2012
![Page 2: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/2.jpg)
![Page 3: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/3.jpg)
Air and Fuel will expand due to combustion, pushing the piston downwards.
![Page 4: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/4.jpg)
If we connected the piston to a crank mechanism, we can convert the reciprocating motion into rotation.
![Page 5: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/5.jpg)
Air and fuel need intake system to get into the cylinder.
![Page 6: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/6.jpg)
Combustion products need exhaust system to be pushed out the cylinder.
![Page 7: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/7.jpg)
![Page 8: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/8.jpg)
![Page 9: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/9.jpg)
Intake valve is oppened.
![Page 10: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/10.jpg)
The Intake valve is closed, when the piston reached the BDC ( Bottom dead center).
![Page 11: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/11.jpg)
Both valves are closed
![Page 12: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/12.jpg)
Now ignition starts to begin the heat addition process.
![Page 13: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/13.jpg)
![Page 14: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/14.jpg)
Exhaust valve begins opening.
![Page 15: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/15.jpg)
![Page 16: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/16.jpg)
Engine Volume.
Vcylinder= ¼π d2l.
Where, d: cylinder diameter (bore) L: cylinder length (stroke)
Vcylinders= ¼π d2l * z where, z: number of cylinders
V˚Stroke = ¼π d2l * z * N/60ζ
Where, N: number of crank shaft revolutions per minute (rpm)
ζ: =2 for 4-stroke engines= 1 for 2-stroke engines
![Page 17: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/17.jpg)
Engine Performance Parameters.
a- Power:
1- Brake Power: the measured power output of the engine
BP= T * ωWhere, T: Torque (N.m)ω: radial speed (rad/s) and ω= 2πN/60
2- Indicated Power: is the theoretical power of a reciprocating engine if it is completely frictionless in converting the expanding gas energy (piston pressure × displacement) in the cylinders.
IP= BP + FP
3- Friction Power FP: increases proportionally with N2
![Page 18: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/18.jpg)
Engine Performance Parameters.
b- Thermal efficiency:
1- Brake thermal efficiency: ηb= BP/Q˚add
Where, Q˚add: rate of heat added to engine per second due
to fuel burning
2- Indicated thermal efficiency :ηI= IP/Q˚add
Q˚add=m˚f * C.VWhere,m˚f : consumed fuel flowrate (kg/s)C.V: fuel heating value: heat released per each
kg of completely burned fuel (kJ/kg)
![Page 19: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/19.jpg)
Engine Performance Parameters.
c- mean effective pressure:
1- Brake mean effective pressure: Bmep= BP/ V˚Stroke Where, BP : brake powerV˚Stroke :engine cylinders volume
2- Indicated mean effective pressure :
Imep= IP/ V˚Stroke
Mean effective pressure: a valuable measure of an engine's capacity to do work that is independent of engine displacement.
![Page 20: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/20.jpg)
Engine Performance Parameters.
d- specific fuel consumption:
1- Brake specific fuel consumption: Bsfc= m˚f /BPWhere, BP : brake powerm˚f : consumed fuel flowrate (kg/s)
2- Indicated specific fuel consumption :
Isfc= m˚f /IP
![Page 21: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/21.jpg)
Engine Performance Parameters.
e- Engine efficiencies:
1- Mechanical efficiency : ηm= BP/IPηm= ηb/ηI
2- Volumetric efficiency :V˚Stroke )actual = ηv ¼π d2l * z * N/60ζ
![Page 22: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/22.jpg)
Brake power calculation:BP=ηb*Q˚add
=ηb m˚f C.V=ηb m˚a F/A C.V=ηb ρa V˚Stroke F/A C.V=ηb ηv ρa F/A C.V ¼π d2l * z * N/60ζ
Q˚add=m˚f * C.VF/A = m˚f / m˚a
m˚a= ρa V˚Stroke
BP=ηb ηv ρa F/A C.V ¼π d2l * z * N/60ζ
![Page 23: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/23.jpg)
Example (6-3):
An eight-cylinder, four stroke diesel engine develops 900 kW
of brake power at 600 rpm. The cylinder size is 37 cm bore by 46
cm stroke and the engine uses 4.5 kg of fuel per minute. Upon
complete combustion, the fuel releases heat energy of 45 MJ/kg.
The indicated mean effective pressure is 660 kPa. Calculate the
indicated, brake and mechanical efficiencies.
![Page 24: Cairo 2nd Petrol Lecture 8](https://reader036.vdocument.in/reader036/viewer/2022062405/5564ed0ad8b42ab34e8b4c36/html5/thumbnails/24.jpg)