Auto Engines Aren't Designed to Take Full Power for More Than a Few Minutes...

Discussion in 'Ford' started by rv6ejguy, Jun 28, 2014.

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  1. Oct 3, 2017 #101

    wsimpso1

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    Sort of. You are not controlling the clutch directly, you are now in a system with coupled operating variables. Engine speed determines if you have engagement. Seems elegant until you are maneuvering in a harbor and find that you have only too much power and coasting as options. I think I would rather have beta pitch available, and I am used to that with boats.

    Theoretically you can raise the engagement speed with attendant risks. That exposes you to how to do a restart if you run a tank dry and engine speed drops to disengagement speed before you figure it out. Much faster to restart if it windmills through injector purge instead of going through that with the starter motor at cranking speed. It also exposes you to many more cycles on not just the clutch, but on the isolator system. You want to redesign the centrifugal clutch, isolator, be the fabricator, test engineer, test pilot, etc? You can, I will held your beer and watch.

    Billski
     
    Last edited: Oct 3, 2017
  2. Oct 3, 2017 #102

    tspear

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    The more I read about the complexity of TV and associated bearing/thrust issues; the more I like the idea of a series hybrid.
    Disconnect the engine from the prop/thrust in the mechanical sense. Likely weight a little bit more, and I would guess it also eliminates a lot of failure modes (introduces a few too, but they are much more isolated so easier to solve).

    Tim
     
  3. Oct 3, 2017 #103

    wsimpso1

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    Thread Drift Alert! We already have threads on this topic, do we not? Ah well, so be it.

    In order to avoid one problem that has been solved repeatedly since the 1930's Tim is proposing that we solve the same problem anyway... here is why.

    At the engine-generator set, you will have an engine with all of its forcing vibrations, a coupling to take power to the generator, and the generator with its own winding sets and AC drivers and resultant forcing functions. The engine and generator rotating parts have inertia, with the engine's crankshaft, the coupling system, and the e-machine's armature each having some sort of springiness to them. You still have to design the system to go between the engine and generator to isolate the generator torsionally and avoid most TV modes and be sturdy enough when transitioning through any TV modes that remain.

    Since these are airplanes we are discussing, we must recognize that WEIGHT IS THE ENEMY. The e-machines and their power electronics weigh (at least for now) way more than a well done gearbox and the generator-motor power electronics generally have higher losses than a decently done gearbox. This is not an improvement...

    This "solution" requires that we solve the same problem while making everything else about our power system more difficult. To me, that is not much of a solution.

    Billski
     
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  4. Oct 3, 2017 #104

    tspear

    tspear

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    Billski,

    I should have said in my mind it is easier. Based on the other threads, I know it really is not.... :D

    Tim
     
  5. Oct 3, 2017 #105

    BBerson

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    I was mostly wondering if Ford sells engines engineered for applications other than vehicles?

    Probably won't buy any more Lycoming engines.
     
    Last edited: Oct 3, 2017
  6. Oct 3, 2017 #106

    Himat

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    And since when where airplanes not vehicles?;)
    If not for vehicles I think of engines for stationary generator sets, that at small sizes use adapted available “multipurpose” engines and at large sizes uses purpose built engines. The large ones commonly look like they are closely related to big ship engines.
     
  7. Oct 5, 2017 #107

    TXFlyGuy

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    Here is another question...during these tests, what oil does the manufacturer use? Synthetic? And, what gasoline, 87 Octane? 93 Octane?

    The owners manual in my wife's new Ford Fusion (2.0 engine) says the testing was done with Premium (93 Octane) gasoline.
     
  8. Oct 5, 2017 #108

    BBerson

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    If a stock "multipurpose" engine is fitted to a stationary generator set and has some torsional vibration resonance problems, could the genset maker work with Ford to install a special crankshaft?
    I know Ford would NOT work with any airplane experimenter, so forget that. The question is: do genset manufacturers normally need to modify a "multipurpose" engine for that particular use regarding TV?
     
  9. Oct 5, 2017 #109

    Himat

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    I would think only if it was a substantial business for Ford.

    If the genset makers have to modify “multipurpose” engine for that particular application? I would think no, because it would drive cost up. On the other side, those making “industrial engines” do probably work together with their large customers to make the engines easy adaptable.
     
  10. Oct 6, 2017 #110

    pictsidhe

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    You fix TV with the coupling between the engine and whatever it is driving, not by messing with the crank.
     
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  11. Oct 6, 2017 #111

    pictsidhe

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    Many engines will now adjust ignition timing depending on octane. Higher octane will then often give more power and mpg. Easy figures boost...
     
  12. Oct 6, 2017 #112

    wsimpso1

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    Engine oil, antifreeze, and filters on test are the production part numbers as used in factory fill. Oil and filter changes are performed per normal mileage intervals with the same part numbers. If oil life computation (using time, oil temperature and engine rpm)is used with an engine (virtually all have this feature now), then oil is changed according to that calc.

    Fuel is per the operating manual.

    During the time I was at Ford and at FCA, there was a strong ethic of testing the engines, powertrains, and whole vehicle in the state that the customer would use them.
     
  13. Oct 6, 2017 #113

    wsimpso1

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    Anyone hooking an engine to other equipment has potential issues that must be managed:

    Axial and radial misalignment;
    Engine vibration modes;
    Downstream element vibration modes;
    Control of engine and downstream elements.

    Dyno labs use coupling devices between engines and the big electric motors, and sometimes they take beating because the springs have inadequate capacity or there was a resonance set up. Same issues as with a PSRU/prop or with an automatic trans.

    When engines are sold to genset producers by engine makers, the genset maker has the responsibility to come up with an acceptable product. They work with businesses that make couplings to find the right torque capacity and spring rates to avoid resonance, provide clean controlled power, etc. I strongly suspect that while the engine part number will be unique to the genset customer and contract, and may indeed be a unique combination of part numbers, all of the internal parts will be regular production part numbers for those engines.

    Special crankshafts? Doubtful. The vibration characteristics of the cranks are a function of geometry and Young's modulus (ratio of material elastic deformation vs applied stress). Geometry is fixed by engine design and all steels have an E of 30 Mpsi. Cast irons can have lower Young moduli, and some irons have different damping character too, but CI cranks are generally not used in automotive engines anymore.

    Billski
     
  14. Oct 6, 2017 #114

    wsimpso1

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    The usual way of doing this is a knock sensor. Some folks call it a microphone, but it is actually a tuned accelerometer with a mass on it, making it sensitive to a particular frequency specific to knock in that engine. Orientation and position of the things was always a matter for development. The engine knocks and the sensor sends a signal to the processor, which instantly retards spark timing a couple degrees and decrements the advance number in the cell applicable to the that engine rpm/throttle position/engine top water temp/etc that the engine was running at that moment. Then periodically, all of the advance tables are incremented until again knock is sensed and bumped back down. In that way, the engine controller was continually looking to advance timing for efficiency and would correct when knock was sensed.

    As far as I know, the knock sensors had disappeared from production engines and their control schemes. They are still used in development. Always seemed like an elegant way of doing things...

    Billski
     
  15. Oct 6, 2017 #115

    wsimpso1

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    Yep, they tune the transmitted vibe and resonance modes with the coupling. Axial and radial misalignments are also handled using couplings as well.
     
  16. Oct 6, 2017 #116

    rv6ejguy

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    A few points:

    GM is still using nodular cast iron cranks in many engines, including performance engines. The damping effects are often beneficial compared to steel as wsimpso1 mentioned.

    Knock sensors are still fitted to quite a number of production engines.

    Never assume everything will be all right when altered or coupled to drive some different device when it comes to TV inside an engine. Gensets, propellers, gearboxes, jet pumps, lighter flywheels, different harmonic balancers, etc. can all have detrimental effects. I've seen a number instances over the years of broken cranks in short order after things are changed, when normally, cranks never break in the stock configuration and application. Remember, since it's coupled, it's a system, not individual parts.

    garycrank.jpg

    This 4340 billet crank lasted less than 2 hours after installation along with a solid crank pulley.
     
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  17. Oct 6, 2017 #117

    BBerson

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    Lots of info here.
    I thought generators were direct rigidly connected, at least the small Onan I took apart was, I think.
    For a direct drive prop on a crankshaft is there a tunable coupling?
     
  18. Oct 7, 2017 #118

    TXFlyGuy

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    This is a concern, for sure. While our "system" has flown successfully, it has been modified. New prop and gearbox. These are untested as of today. A lighter version of these are flying with the LS3.

    Our prop is 10" larger in diameter, and the gearbox is heavy duty, rated for in excess of 600hp.
     
  19. Oct 8, 2017 #119

    wsimpso1

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    That is a surprise, as everyone else has pretty much gone steel.... I'll put that one away for reference.

    I knew that they had been gone from production at Ford and FCA back when everything was NA. Went looking for them and my sample showed they are not in NA engines, but are in every turbocharged engine and every direct injection engine I checked. I did not check on flex fuel engines. I wonder why they eliminated knock sensors from NA, but put them back in for GTDI and turbos. Are turboed engines more sensitive on spark timing?

    Absolutely agree. Did they omit the harmonic dampener front pulley? Rotec Munich has a bunch of their vibe measurement systems at each of the automakers for a reason...

    Billski
     
  20. Oct 8, 2017 #120

    rv6ejguy

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    GM has developed Nodular iron cranks to a high degree. Used in production LS1, LS2, LS3 and LS6 V8s and many other engines.

    Yes, turbo engines have much more of a battle balancing spark timing with MAP/RPM to stay just short of detonation.

    Yes, the example engine traded the stock harmonic damper for a lightweight aluminum pulley and this is the 3rd crank failure I've heard of in less than 5 hours of run time.
     
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