Anna
University, Chennai Nov/Dec Important Questions
Dynamics of Machinery ME2302
V Sem MECH
Unit
I-V
1.
The
turning moment diagram for a petrol engine is drawn to a scale of 1mm to
6N-9-9m and the horizontal scale of 1mm to 1˚.The turning moment repeat itself
after every half revolution of the
engine. The area above and below the mean torque line are 305, 710,
50,350,980and 275mm2. The mass of rotating parts is 40kg at a radius of gyration
of 140mm.Clculate the coefficient of fluctuation of speed if the mean speed is
1500rpm.
2.
For
reciprocating engine, derive the expression for (i)Velocity and acceleration of
the piston (ii)Angular velocity and
angular acceleration of the connecting rod
3.
The
radius of gyration of a fly wheel is 1meter and fluctuation of speed is not to
exceed 1% of the mean speed of the flywheel. If the mass of the flywheel is
3340kg and the steam develops 150KW at 135rpm, then find, 1.Maximum fluctuation
of energy 2. Coefficient of fluctuation
of energy.
4. A machine supported symmetrically on four springs has a mass of 80 kg.
The mass of the reciprocating parts is 2.2 kg which move through a vertical
stroke of 100 mm with simple harmonic motion. Neglecting damping, determine the
combined stiffness of the spring so that the force transmitted to foundation is
1/20th of the impresses force. The machine crank shaft rotates
at 800 rpm.If under working conditions, the damping reduces the amplitudes of
successive vibrations by 30%, find (i) the force transmitted to the foundation
at resonance and (ii) the amplitude of vibration at resonance.
5.
A
four cylinder vertical engine has cranks 150mm long. The plane of rotation of
the first, second and fourth cranks are 400mm,200mm and 200mm respectively from
that of the third crank and their reciprocating masses are 50kg,60kg and 50kg
respectively. Find the mass of the reciprocating parts for the third cylinder
and relative angular position of the cranks in order that the engine may be in
complete balance.
6.
Derive
the following expression of effects of partial balancing in two cylinder
locomotive engine (i) Variation of
tractive force (ii) Swaying couple (iii)
Hammer blow.
7.
A,
B, C and D are four masses carried by a rotating shaft at radii
100mm,125mm,200mm and 150mm respectively. The planes in which the masses
revolve are spaced 600mm apart and the masses of B,C and D are 10kg,5kg and
4kgrespectively.Find the required mass A and relative angular setting of the
four masses so that the shaft be in complete balance.
8.
A vertical double acting steam engine has a
cylinder 300 mm diameter and 450 mm stroke and runs at 200 rpm. The
reciprocating parts has a mass of 225 kg and the piston rod is 50 mm diameter.
The connecting rod is 1.2 m long. When the crank has turned through 125° from
the top dead center the steam pressure above the piston is 30 kN/m2 and
below the piston is 1.5 kN/m2. Calculate
(i)
Crank-pin effort
and
(ii)
The effective turning moment on the crank shaft.
9.
Derive an expression for the natural frequency of
the free longitudinal vibration by
(i)
(i)Equilibrium method (ii) Energy method (iii)Rayleigh’s method
10.Determine
equation of motion when a liquid column vibrating in a ‘U’tube by
(i)
Newton’s method
(ii) Energy method and hence find its natural frequency
11. The barrel of a large gun recoils against a spring on firing. At the end
of the firing, a dashpot is engaged that allows the barrel to return to its
original position in minimum time without oscillation. Gun barrel mass is
400kg and initial velocity of recoils
1m.Determine spring stuffiness and critical damping coefficient of dashpot.
12.Explain the
sketches different cases of damped vibrations.
13. A mass of 10kg is suspended from one end of a helical spring, the other
end being fixed. The stiffness of the spring
is10N/mm.The viscous damping causes the amplitude to decreases to one-tenth of
the initial value in four complete
oscillations. If a periodic force of 150cos50t N is applied at the mass in the
vertical direction .Find the amplitude of the forced vibrations? What is its
value of resonance?
14.A harmonic
exiting force of 25N is acting on a machine part which is having a mass of 2Kg
and vibrating in
viscous medium. The exciting force causes resonant amplitude of 12.5mm
with a period of 0.2sec
15. An industrial machine weighting 445kg is supported on a spring with a
statical deflection of 0.5cm.If the
machine has rotating imbalance of 25kg-cm.Determine the force
transmitted at 1200rpm and the dynamic
amplitude at the speed.
16.Explain the
effect of Gyroscopic couple on a Naval ship during pitching.
17. The length of the upper and lower arms of a porter governor are 200mm
and 250mm respectively. Both the arms are pivoted on the axis of rotation. The
central load is 150N, the weight of the each ball is 20N and the friction of
the sleeve together with the resistance of the operating gear is equivalent to
a force of 30N at the sleeve. If the limiting inclinations of the upper arms to
the vertical are 30˚ and 40˚ taking friction in to account. Find the range of
speed of the governor
18.Calclate the
minimum speed of a proell governor, which has equal arms each of 200mm and are
provided on the axis of rotation. The mass of each ball is 4kg and the central
mass on the sleeve is 20kg.The extension arms of the lower links are each 60mm
long and parallel to the axis when the minimum radius of the ball is 100mm.of load.
