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Effect of orientation on friction power of an I.C.E.

  1. Apr 17, 2007 #1
    hello all...

    A part of my final year project involves the determination of frictional power of an I.C.Engine(for this we used a 4cyl isuzu si engine) using a typical motoring test(using a 3ph ind motor and the engine was stripped of all its accessories liek alternator water pump), and finding out if there would be a reduction in frictional power if we mounted the engine in diff orientation(horizontal like a flat 4 or a boxer only all cyl were inline).

    Well we were able to get a reduction of between 9-1.4% reduction in friction with variation in speeds(the % diff reduces with increase in speed).

    Now to what exactly can we attribute this reduction in fp?

    Would be extremely grateful if anyone could explain this to me.

    Thanks.
     
  2. jcsd
  3. Apr 17, 2007 #2

    FredGarvin

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    Out of curiosity, did you happen to notice any deviations in power as well?

    The first thing that comes to mind for this is possibly an improvement was made to the lubrication system either in terms of delivery or drainage. Can you elaborate a bit more on the orientation that you saw the improvement with?
     
  4. Apr 17, 2007 #3
    Well we actually never ran the engine, we were basically conducting a motoring test that is using a motor to run the engine using a belt drive.

    About the orientation:
    The standard position of an engine would be vertical that is the piston would reciprocate up and down.
    We rotate the engine by 90 degrees so that the piston reciprocates horizontally rather than vertically.
     
  5. Apr 17, 2007 #4

    brewnog

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    Sounds like you're reducing losses to auxilliary systems by stopping the oil pump strainer from sucking. Or something like that anyway.
     
  6. Apr 17, 2007 #5
    Yes there were no auxiliary systems connected when we ran the tests in both the orientation.Could there be a difference in the crank train or valve train losses if the engine reciprocated in the horizontal plane?
    What about the piston assembly?
    What could the reduction be attributed to is my question, since we did get a reduction in power consumption of the motor when in the horizontal orientation.
     
  7. Apr 17, 2007 #6

    Mech_Engineer

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    Is the engine's oil pan filled with oil? If you tip and engine that was meant to run vertically on it's side, the oil will fill into the block and cause some losses due to the viscous oil that the crankshaft is having to run through.

    There isn't really any fundamental reason why an engine would run more efficiently on a horizontal plane versus a vertical one; however, an engine designed to run in a specific orientation will not have proper oil delivery in the opposite case. It's also very possible an engine tipped on it's side will leak a significant amount of oil through it's valve cover breathers, but that wouldn't really cause a loss in power until the engine ran out of oil.
     
  8. Apr 17, 2007 #7

    brewnog

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    But it's entirely possible that it could cause an increase in apparent power if the losses to the oil pump were reduced by lack of oil feed.
     
  9. Apr 18, 2007 #8

    Mech_Engineer

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    Perhaps, but it depends on how fast the engine if running (RPM). It sounds to me like their test jig involves an electric motor that is rotating the crankshaft on the engine and measuring required torque to do so. If this is indeed the case unless the engine is being turned exceptionally quickly the oil pump would present a negligible required torque compared to say the pistons and the cylinder walls.
     
  10. Apr 18, 2007 #9

    brewnog

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    I disagree, frictional losses from piston walls and bearings increase exponentially with engine speed, where the losses to an oil pump can be considerable at low speeds; compare the work required to pump oil with the work required to pump air, it's definitely to the order of a percent or so of the gross engine power. This explanation also ties in with the difference being less at higher speeds. Besides, the frictional losses to piston walls and bearings are there regardless of orientation.

    However, I still don't think this stacks up. I'm struggling to think of any other reason why an engine assembly will take less power to motor when run in a different orientation.

    Windtalker:
    Was the engine still being lubricated in both instances?
    What speed were you motoring the engine at?
    What else changed between your tests?
     
  11. Apr 19, 2007 #10
    I'm confused here, do you mean you turned the engine shaft with an external motor using a belt, without actually having combustion inside the engine ?
    Just if that is the case, perhaps the differences have to do with the way the belt provides torque to the shaft, provided you turned the shaft but not the belt also, versus the difference in required torque while turning the shaft for different angles that I'd expect to exist.
     
    Last edited: Apr 19, 2007
  12. Apr 19, 2007 #11

    brewnog

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    That's a clever thought; perhaps the motored drive was putting a different load on the crankshaft bearings (and gear train) when you turned the engine on its side, causing more friction to be witnessed?
     
  13. Apr 20, 2007 #12
    Yes this is exactly our test jig.



    @brewnog
    Well the engine was not being lubricated using a pump although it has considerable amount of lube oil inside it.

    The engine was being motored between 250-1800rpm.

    I dont see any other changes being made in between the tests.


    Also the frictional power that is the power input to the motor reduced when in horizontal plane.


    @Aero Stud:

    The engine itself was turned without making any changes to the motor or the belt except for alignment purposes.

    Combustion was not taking place inside the motor.
     
    Last edited: Apr 20, 2007
  14. Apr 23, 2007 #13
    Hello all..

    Id like to ask another question here,we have seen single cylinder engines on many bikes being put in the horizontal axis,what advantage or savings in power could this possibly bring.(honda c series, mobex regina see here http://en.wikipedia.org/wiki/Single_cylinder_engine)
    I think the balancing of forces of the vertical motion of the piston need not be done here..so will tht contribute in any way to a reduction in frictional power??
     
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