Diesel engine vibration
Diesel engine vibration
(OP)
A vertical acceleration PSD of a diesel engine used as part of a generator shows a second harmonic peak with significantly more energy than the first harmonic. Given the mechanisms at work here is this possible?
If not where else should I look:
(a) that it coincides with a mode of the isolation system?
(b) some magnetic force due to the generator?
Engine runs at 25 Hz and has 4 cylinders. Generator supplies 50 Hz alternating current.
Thank you for your assistance
If not where else should I look:
(a) that it coincides with a mode of the isolation system?
(b) some magnetic force due to the generator?
Engine runs at 25 Hz and has 4 cylinders. Generator supplies 50 Hz alternating current.
Thank you for your assistance





RE: Diesel engine vibration
Does the engine have a balancer on it?
M
--
Dr Michael F Platten
RE: Diesel engine vibration
RE: Diesel engine vibration
h
The secondary inertial forces are of similar magnitude to a single unbalanced rod and piston rotating at 2X crank speed, and acting along the cylinder centerline. A pair of counter-rotating counterweights rotating at twice crank speed is needed to counter act the secondary force.
Does your engine have them?
RE: Diesel engine vibration
- Steve
RE: Diesel engine vibration
On page 221 of MECHANICAL VIBRATIONS Hartog says of a single cylnder's inertial forces - "In words: the vertical component of the inertia force consists of two parts, a " primary part" equal to the inertia action of the combined reciprocating and rotating masses as if they were moving up and down harmonically with crank-shaft frequency and amplitude r, and a "secondary part" equal to the inertia T action of a mass jyWrec moving up and down with twice the crank-shaft frequency and with the same amplitude r.
The horizontal or lateral component has a primary part only,
viz., that due to the rotating mass."
I think the "firing" forces that sneak out are via torque action/reaction.
So I would not expect firing (torque) to automatically have a vertical component except as a result of mounting scheme.
Goofy 4 cyl engine mount scheme from HArtog attached
RE: Diesel engine vibration
RE: Diesel engine vibration
I'd be very surprised to see much first order.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Diesel engine vibration
OP said vertical 2X vibration and 4 cylinder, and it was I who leaped to the conclusion inline 4.
You would expect firing frequency to have a vertical (along cylnder axis) component?
Dan T
RE: Diesel engine vibration
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Diesel engine vibration
Our issues were always at high-ish speeds and typically when 2E coupled with some other phenomenon, like whole PT bending, or some ancilliary flapping around on the FEAD bracket.
Low speed 2E (in an I4) was normally an issue for gear rattle, both for unsynchronized gears in the transmission and for cam/pump drive systems. Indeed, one I4 diesel engine we analysed had most of its sound power coming from the timing drive at some conditions.
- Steve
RE: Diesel engine vibration
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Diesel engine vibration
ya - HOO
50 Hz operation is higher still