SECTION A Q1. An engine is connected to an unbalanced, rotating shaft as shown in Figure Q1. Viscoelastic shock absorbers are used to mount the engine to a frame. The engine is supported by rigid, frictionless guides that prevent it from moving in the horizontal direction. The shock absorbers can be modelled with a spring-damper system. The spring stiffness of the absorber takes on a value of k = 520 kN/m while its damping coefficient c is unknown. The entire engine-shaft assembly has a mass M of 35 kg. The equivalent mass of the shaft unbalance takes on a value of m = 1.2 kg at an offset distance r = 4 mm rotating at angular velocity w. The unbalanced rotating mass of the shaft results in a force F(t) acting in the vertical direction: F(t) = mw²r sin(wt). fremo

Elements Of Electromagnetics
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ISBN:9780190698614
Author:Sadiku, Matthew N. O.
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SECTION A
Q1. An engine is connected to an unbalanced, rotating shaft as shown in Figure Q1.
Viscoelastic shock absorbers are used to mount the engine to a frame. The engine
is supported by rigid, frictionless guides that prevent it from moving in the horizontal
direction.
The shock absorbers can be modelled with a spring-damper system. The spring
stiffness of the absorber takes on a value of k = 520 kN/m while its damping
coefficient c is unknown.
The entire engine-shaft assembly has a mass M of 35 kg. The equivalent mass of the
shaft unbalance takes on a value of m = 1.2 kg at an offset distance r = 4 mm rotating
at angular velocity w.
The unbalanced rotating mass of the shaft results in a force F(t) acting in the vertical
direction:
F(t) = mw²r sin(wt).
The force from the unbalance is causing vibration of the engine within the frame.
Whenever the shaft is rotating at its operating speed of 1500 rpm the engine is
displaced by a maximum of X = 0.3 mm.
OSSEM
a) Calculate the magnitude of the force F(t) caused by the unbalance which is acting
on the engine.
b) Calculate the damping ratio (.
c) Calculate the damping coefficient c.
d) Calculate the phase angle Y.
e) At what shaft rotation frequency (in Hz) would resonance occur in the entire
engine assembly if there were no viscous damping?
r = 4 mm
ME22002
Frictionless,
rigid guide
Tilin
k = 520 kN/m
M = 35 kg
noise Figure Q1
m = 1.2 kg
1500 rpm
c=?
Frictionless,
rigid guide
Page
2 of 10
Transcribed Image Text:SECTION A Q1. An engine is connected to an unbalanced, rotating shaft as shown in Figure Q1. Viscoelastic shock absorbers are used to mount the engine to a frame. The engine is supported by rigid, frictionless guides that prevent it from moving in the horizontal direction. The shock absorbers can be modelled with a spring-damper system. The spring stiffness of the absorber takes on a value of k = 520 kN/m while its damping coefficient c is unknown. The entire engine-shaft assembly has a mass M of 35 kg. The equivalent mass of the shaft unbalance takes on a value of m = 1.2 kg at an offset distance r = 4 mm rotating at angular velocity w. The unbalanced rotating mass of the shaft results in a force F(t) acting in the vertical direction: F(t) = mw²r sin(wt). The force from the unbalance is causing vibration of the engine within the frame. Whenever the shaft is rotating at its operating speed of 1500 rpm the engine is displaced by a maximum of X = 0.3 mm. OSSEM a) Calculate the magnitude of the force F(t) caused by the unbalance which is acting on the engine. b) Calculate the damping ratio (. c) Calculate the damping coefficient c. d) Calculate the phase angle Y. e) At what shaft rotation frequency (in Hz) would resonance occur in the entire engine assembly if there were no viscous damping? r = 4 mm ME22002 Frictionless, rigid guide Tilin k = 520 kN/m M = 35 kg noise Figure Q1 m = 1.2 kg 1500 rpm c=? Frictionless, rigid guide Page 2 of 10
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