Reference no: EM131992325

(SECTION-A)

Note-Attempt All Questions.

(1) Sensitiveness of a governor is define as

a) range  of speed/mean speed         b) mean speed/range of speed

c) range of speed × mean speed      d) none of these

(2) In case of free vibration with viscous damping. The damping force is proportional to

a) The displacement                         b) The velocity

c) the acceleration                           d) the natural frequency

(3) A governor will be stable if the radius of rotation of the ball -

a)  increases as the  equilibrium  speed decreases

b)  increases as the equilibrium  speed increases

c)  decreases as the equilibrium  speed increases

d)  none of these

(4) What is the number of nodes in a shaft carrying three rotor?

a) zero                                            b) 2

c) 3                                                d) 4

(5) In which one of the following is a fly wheel generally employed

a) lathe                                       b) electric motor

c) punching machine                       d) gear box

(6) The equation of motion for a damped viscous vibration is 3x¨ + 9x? + 27x =0.

The damping factor is-

a) 0.25                                             b)  0.50

c)  0.75                                            d)  1.00

(7) Gyroscopic couple on the air-craft is-

a)  Iωω_p                                             b) Iω2 ω_p

c) I²ωω_p                                           d) Iωω2

(8) The flywheel absorb energy during those periods of crank rotation when-

a) The twisting moment is greater than the resisting moment

b) The twisting moment is equal to the resisting moment

c) The twisting moment  is less than the  resisting moment

d) The load on the engine falls

(9) What is the condition for dynamic balancing of a shaft-rotor system?

a) ∑M =0 and ∑F=0                       b) ∑M=0

c) ∑F =0                                     d) ∑M + ∑F =0

(10) The critical speed of a rotating shaft depends upon :

a)  mass                                        b) stiffness

c) mass and  stiffness                      d) mass, stiffness and eccentricity.

(SECTION-B)

Attempt any Eight  Questions.

1. Prove maximum fluctuation of energy ΔE=2EC_S. where: E=KE of flywheel corresponding to mean speed.

C_S= Coefficient of fluctuation of speed

V= Linear velocity of rim of flywheel at mean radius M=Mass of flywheel.

2. A flywheel of a machine having weight of 4500 N and radius of gyration of 2m has cyclic fluctuation of speed  from 125  rpm to  120 rpm assuming g = 10 m/sec² . What  is the maximum fluctuation of energy?

3. What are the conditions for a body to be in equilibrium under the action of two forces, three forces and two forces and a torque?

4. The turbine rotor of a sea vessel having a mass of 1050 kg rotates at 1200 rpm clockwise while looking from the stern. The vessel pitches with an angular velocity of

1.2 rad/s. What will be the gyroscopic couple transmitted to the hull when the bow rises? The radius of gyration of the rotor is 300 mm.

5. In a flywheel the safe stress is 25.2 MN/m² and the  density is 7  g/cm³. Then what  is the maximum peripheral velocity?

6. Explain the primary and secondary unbalanced forces in reciprocating engine.

7. Prove that the maximum variation of tractive force is equal to ±√2 (1-C) m_R x ω2 x r where C is the fraction of the mass of reciprocating parts which is to be balanced.

8. Explain the controlling force and controlling force curve.

9. Explain D' Alembert's principle.

10. What do you mean by lubrication and explain objective of lubrication.

SECTION - C

Attempt any Two Questions

1. a) A shaft is rotating at a uniform angular speed. Four masses m₁,m₂ ,m₃ and m₄ of magnitudes 300kg, 450kg, 360kg and 390kg respectively are attached rigidly to the shaft. The masses are rotating in the same plain.  The  corresponding radii of rotation are 200 mm,150 mm,250 mm, and 300 mm respectively. The angle made by these masses with horizontal are 0⁰,45⁰,120⁰ and 255⁰ respectively. Find:

(i) The magnitude of balancing mass.

(ii) The position of the balancing mass if its radius is 200mm.

b) Write a short note on critical speed of a shaft.

2. a) Calculate the minimum speed maximum speed and range of speed of a porter governor, which has equal arms each 200mm long and pivoted on the axis of rotation. The mass of each ball is 4kg and the central mass on the sleeve is 20kg. The radius of rotation of the ball is 100 mm when the governor begins to lift and 130 mm when the governor is at maximum speed.

b) Define and explain the term: governor effort and governor power.

3.                

a) Prove that the ratio of tension in tight and slack side of a band and block brake is given by-

T1/T0 = (1 + µTan8/1-µTan8)

b) The radius of gyration of flywheel is 1m and the fluctuation of speed is not to  exceed 1% of the mean speed of flywheel. The mass of the flywheel is 3340  kg  and the steam engine develops 150kw at 135 r.p.m., then find:

(i) Maximum fluctuation of energy

(ii) Co-efficient of fluctuation of energy.