2.61 Internal Combustion Engines - MIT OpenCourseWare
Transcript of 2.61 Internal Combustion Engines - MIT OpenCourseWare
![Page 1: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/1.jpg)
MIT OpenCourseWare http://ocw.mit.edu
2.61 Internal Combustion Engines Spring 2008
For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.
![Page 2: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/2.jpg)
Engine Friction and Lubrication
Engine friction – terminology – Pumping loss – Rubbing friction loss
![Page 3: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/3.jpg)
Engine Friction: terminology
• Pumping work: Wp – Work per cycle to move the working fluid through the engine
• Rubbing friction work: Wrf
• Accessory work: Wa
Total Friction work: Wtf = Wp + Wrf + Wa
Normalized by cylinder displacement → MEP – tfmep = pmep + rfmep + amep
Net output of engine – bmep = imep(g) – tfmep
Mechanical efficiency – ηm = bmep / imep(g)
![Page 4: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/4.jpg)
Friction components
1. Crankshaft friction ¾ Main bearings, front and rear bearing oil seals
2. Reciprocating friction ¾ Connecting rod bearings, piston assembly
3. Valve train ¾ Camshafts, cam followers, valve actuation mechanisms
4. Auxiliary components ¾ Oil, water and fuel pumps, alternator
5. Pumping loss ¾ Gas exchange system (air filter, intake, throttle, valves,
exhaust pipes, after-treatment device, muffler)¾ Engine fluid flow (coolant, oil)
![Page 5: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/5.jpg)
Engine Friction
Fig. 13-1 Comparison of major categories of
Image removed due to copyright restrictions. Please see: Fig. 13-1 in friction losess: fmep at different Heywood, John B. Internal Combustion Engine Fundamentals. loads and speeds for 1.6 L four-New York, NY: McGraw-Hill, 1988. cylinder overhead-cam automotive
Spark Ignition (SI) and Compression-Ignition (CI) engines.
![Page 6: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/6.jpg)
Pumping loss
Image removed due to copyright restrictions. Please see: Fig. 13-15 in Heywood, John B. Internal Combustion Engine Fundamentals. New York, NY: McGraw-Hill, 1988.
Fig. 13-15 Puming loop diagram for SI engine under firing conditions, showing throttling work Vd(pe-pi), and valve flow work
![Page 7: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/7.jpg)
Sliding friction mechanism
Image removed due to copyright restrictions. Please see: Fig. 13-4 in Heywood, John B. Internal Combustion Engine Fundamentals. New York, NY: McGraw-Hill, 1988.
Energy dissipation processes: • Detaching chemical binding between surfaces • Breakage of mechanical interference (wear)
![Page 8: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/8.jpg)
Bearing Lubrication
Image removed due to copyright restrictions. Please see: Fig. 13-2 in Heywood, John B. Internal Combustion Engine Fundamentals. New York, NY: McGraw-Hill, 1988.
![Page 9: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/9.jpg)
Stribeck Diagram for journal bearing
Image removed due to copyright restrictions. Please see: Fig. 13-3 in Heywood, John B. Internal Combustion Engine Fundamentals. New York, NY: McGraw-Hill, 1988.
![Page 10: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/10.jpg)
Motoring break-down analysis
Image removed due to copyright restrictions. Please see: Fig. 13-14 in Heywood, John B. Internal Combustion Engine Fundamentals. New York, NY: McGraw-Hill, 1988.
Fig. 13-14Motored fmep versus engine speed for engine breakdown tests. (a) Four-cylinder SI engine. (b) Average results for several four- and six-cylinder DI diesel engines
![Page 11: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/11.jpg)
Breakdown of engine mechanical friction
1 F.A. Martin, “Friction in Internal Combustion Engines,” I.Mech.E. Paper C67/85, Combustion Engines – Friction and Wear, pp.1-17,1985. T. Hisatomi and H. Iida, “Nissan Motor Company’s New 2.0 L. Four-cylinder Gasoline Engine,” SAE Trans. Vol. 91, pp. 369-383, 1982; 1st engine.
2nd engine.
M. Hoshi, “Reducing Friction Losses in Automobile Engines,” Tribology International, Vol. 17, pp 185-189, Aug. 1984.
J.T. Kovach, E.A. Tsakiris, and L.T. Wong, “Engine Friction Reduction for Improved Fuel Economy,” SAE Trans. Vol. 91, pp. 1-13, 1982
18
19
19
20
21
Mechanical Friction (%)
Rings + Piston + Rod
RodRings + Piston
Piston + Rod
Piston + Rod
Piston
Rings
Rings
Rings
Mot
orin
g r/m
inM
otor
ing
r/min
Typical
4800 r/min
4800 r/min
Full Load
Full Load
6000
4000
2000
2000
4000
Valvetrain
Crankshaft
100806040200
Rod
Figure by MIT OpenCourseWare.
![Page 12: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/12.jpg)
Valve train friction
Image removed due to copyright restrictions. Please see illustrations of "Valve Timing-gear Designs." In the Bosch Automotive Handbook. London, England: John Wiley & Sons, 2004.
Valve train friction depends on: • Total contact areas • Stress on contact areas
¾Spring and inertia loads
![Page 13: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/13.jpg)
Low friction valve train
Image removed due to copyright restrictions. Please see: Fig. 13-25 in Heywood, John B. Internal Combustion Engine Fundamentals. New York, NY: McGraw-Hill, 1988.
![Page 14: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/14.jpg)
Valve train friction reduction
Engine speed (x1000 rpm)
“Friction loss reduction by new lighter valve train system,”JSAE Review 18 (1977), Fukuoka, Hara, Mori, and Ohtsubo
Courtesy of Elsevier, Inc., http://www.sciencedirect.com. Used with permission.
![Page 15: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/15.jpg)
Piston ring pack
Image removed due to copyright restrictions. Please see: Fig. 13-17 in Heywood, John B. Internal Combustion Engine Fundamentals. New York, NY: McGraw-Hill, 1988.
![Page 16: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/16.jpg)
Hydrodynamic lubrication of the
piston ring
Image removed due to copyright restrictions. Please see: Fig. 13-18 in Heywood, John B. Internal Combustion Engine Fundamentals. New York, NY: McGraw-Hill, 1988.
![Page 17: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/17.jpg)
Friction force and associated power loss
150
100
50
0
0
800
600
400
200
TDC TDC TDCBDC BDCCrank Angle
Intake Compression Expansion Exhaust
Pow
er (N
-m/s
)Fo
rce
(N)
Figure by MIT OpenCourseWare.
![Page 18: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/18.jpg)
Piston slap
Maj
or-T
hrus
t Sid
e
Min
or-T
hrus
t Sid
e
15oBTDC 5oATDCTDC
Piston motion near TDC firing with piston-pin offset towardmajor-thrust side.
Figure by MIT OpenCourseWare.
![Page 19: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/19.jpg)
Bore distortion
1
4th Order
Cylinder Distortion
2nd Order
2nd Order
3rd Order 4th Order
2nd Order 3rd Order
2 3 4
Three orders of bore distortion.
Top deck of hypothetical engine.
Figure by MIT OpenCourseWare.
![Page 20: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/20.jpg)
Lubricants
• Viscosity is a strong function of temperature
• Multi-grade oils (introduced in the 1950’s) – Temperature sensitive polymers to stabilize
viscosity at high temperatures ¾Cold: polymers coiled and inactive ¾Hot: polymers uncoiled and tangle-up:
suppress high temperature thinning
• Stress sensitivity: viscosity is a function of strain rate
![Page 21: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/21.jpg)
Viscosity
Image removed due to copyright restrictions. Please see: Linna, Jan-Roger, et al. "Contribution of Oil Layer Mechanism to the Hydrocarbon Emissions from Spark-ignition Engines." SAE Journal of Fuels and Lubricants 106 (October 1997): 972892.
![Page 22: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/22.jpg)
Modeling of engine friction
• Overall engine friction model: – tfmep (bar) = fn (rpm, Vd, ν, B, S, ….) – See text, ch. 13, ref.6; SAE 900223, …)
• Detailed model
tfmep = ∑( fmep )components
With detailed modeling of component friction as a function of rpm, load, …
![Page 23: 2.61 Internal Combustion Engines - MIT OpenCourseWare](https://reader031.fdocuments.us/reader031/viewer/2022021120/620607b8cf456418c32f1dba/html5/thumbnails/23.jpg)
FMEP distribution
Image removed due to copyright restrictions. Please see: Patton, Kenneth J., et al. "Development and Evaluation of a Friction Model for Spark-ignition Engines." SAE Journal of Engines 98 (February 1989): 890836.
Distribution of FMEP for a 2.0L I-4 engine; B/S = 1.0, SOHC-rocker arm, flat follower, 9.0 compression ratio
C = crankshaft and sealsR = reciprocating componentsV = valve train componentsA = Auxiliary componentsP = Pumping loss