Vibration and Forces - Static and dynamic loading and balancing in engine

Page 4

Index

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1. Engine vibration and critical speed
2. Force and Moments in slow speed diesel engine
3. Vibration damper and detuner
4. Static and dynamic loading and balancing in engine
5. Primary and secondary forces and couple
6. Torsional vibration
7. Axial vibration details
8. Purifier vibration reasons
9. Important element in ship vibration

10. Engine Dynamics

Static and dynamic loading and balancing in engine

Static loads:- These are loads caused by the weight of engine components & the bolt loads.

Dynamic loads:- These are loads caused by the cylinder gas fluctuating pressure & inertia loads of the reciprocating & rotary masses.

Static Balancing:-

(a) It implies that the shaft is stationary or stop at a different position, if rotated when supported between centres.

(b) The sum of all moments taken about its centre of rotation should be zero at any angular position.

(c) It is done by placing counter weight to balance the moments so that their sum becomes zero.

Dynamic balancing:-

(a) It is the balancing of the unbalanced inertia forces together with their moments.

(b) An inertia forces is set up due to the reciprocating masses of the connecting rod crank mechanism, and due to unbalanced rotating masses. Both forces cause foundation vibration.

(c) The Forces due to reciprocating masses of the connecting rod. Crank Mechanism either tries to tear the engine off the foundation or to press it against the foundation, depending on the direction of action.

(d) Unbalanced rotating masses act along the crank web. They are constant at any angle on the crankshaft at a given engine speed. They tend to shift the engine off the foundation or overturn it.

(e) Moment caused by these two inertia forces:-

(i). The rotating masses causes moments to act in the vertical and horizontal planes.

(ii). The reciprocating masses causes moment only in vertical plane.

(iii) Primary and secondary forces are set up due to the inertia forces caused by reciprocating masses.

(iv) The vibration is these forces are in the form of sine waves simple harmonic motion.