WORK SHEET FOR MEP311

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1 EXPERIMENT II-1A STUDY OF PRESSURE DISTRIBUTIONS IN LUBRICATING OIL FILMS USING MICHELL TILTING PAD APPARATUS OBJECTIVE To study generation of pressure profile along and across the thick fluid film (converging, diverging and uniform in Michell Pad Thrust Bearing. OBSERVATIONS Length of pad (L = m Width of pad (B = m Viscosity of oil (η = Pa-s Table Pressure readings Set-1: Speed of belt (u b1 =.... m/s, h 1 =.... mm, h 2 =..... mm Experimental pressure, Pa Analytical pressure, Pa Gauge no. Set-2: Speed of belt (u b2 =.... m/s, h 1 =.... mm, h 2 =..... mm Experimental pressure, Pa Analytical pressure, Pa Gauge no.

2 Set-3: Speed of belt (u b1 =.... m/s, h 1 =.... mm, h 2 =..... mm Gauge no. Experimental pressure, Pa Analytical pressure, Pa Set-4: Speed of belt (u b2 =.... m/s, h 1 =.... mm, h 2 =..... mm Experimental pressure, Pa Analytical pressure, Pa Gauge no. Draw pressures vs. location curves for various sets of experimental and theoretical readings. ANSWER THE FOLLOWING QUESTIONS Name few mechanical systems where thrust pad bearings are used. Define Newton s law of viscous flow. At which film thickness ratio, load carrying capacity of finite pad slider bearing will be maximum. What are the effects of increase in speed and film thickness ratio over the pressure distributions in the film? What happens to build up pressure when: a. h 1 < h 2, b h 1 = h 2, c h 1 > h 2 (Verify it experimentally

3 EXPERIMENT II-1B STUDY OF PRESSURE DISTRIBUTION IN LUBRICATING OIL FILM IN JOURNAL BEARING OBJECTIVES To study the pressure distributions in lubricating oil films in journal bearing at different speeds and loads. OBSERVATIONS Length of bearing (L = m Diameter of journal (D sh = m Bore diameter of bearing (D = m Radial clearance (c = (D-D sh /2 Viscosity of oil (η = Pa-s Table Pressure readings Set-1: Load (W 1 =.... N, Speed of journal (N s1 =.... rps Experimental pressure, Pa Analytical pressure, Pa Gauge location (θ Set-2: Load (W 1 =.... N, Speed of journal (N s2 =.... rps Experimental pressure, Pa Analytical pressure,pa Gauge location (θ

4 Set-3: Load (W 2 =.... N, Speed of journal (N s1 =.... rps Experimental pressure, Pa Analytical pressure, Pa Gauge location (θ Set-4: Load (W 2 =.... N, Speed of journal (N s2 =.... rps Experimental pressure, Pa Analytical pressure, Pa Gauge location (θ Draw pressures vs. θ curves for various sets of experimental and theoretical readings. ANSWER THE FOLLOWING QUESTIONS Name few mechanical systems where oil lubricated journal bearings are used. Explain the pressure development mechanisms in journal bearing. What are the effects of increase in load and speed over pressure distribution in film around the journal? What is bearing number? Explain its physical significance. What is cavitation in journal bearing? How it influence functioning of the bearing.

5 EXPERIMENT II-2A PORTER AND PROELL GOVERNORS OBJECTIVE To study the performance characteristics of Porter and Proell governors PROCEDURE FOR PORTER GOVERNOR For various values of r, calculate F from eq.(2 and plot F v/s r curve as shown in Fig. Determine the equilibrium speeds for equal lifts of the sleeve experimentally by tachometer. Draw speed lines, using F j = (w/g ω j 2 r x, for any convenient r x :Draw F j - r x line, where ω j = ω 1, ω 2,ω 3 etc. Obtain points F 1, F 2 etc on F j - r x, line. For each speed of equilibrium ω 1, ω 2,ω 3 etc determine experimentally, find the radii of rotation r 1, r 2.etc by the intersection of speed lines with F v/s r curve as illustrated in Figure. Determine corresponding value of lift (H 2 -H 1 of the sleeve and compare with corresponding value used in experiment. Give reasons for small differences in lifts. Repeat the experiment twicei. Adding 0.5 kg weight at the sleeve ii. Adding 1 kg weight. Thus find the effect of sleeve loading on the controlling force F i.e., F v/s r curve. PROCEDURE FOR PROELL GOVERNOR For variations ω value of r, calculate F and plot F v/s r curve as shown in Figure Determine equilibrium speeds for equal lifts of sleeve experimentally. 2 Draw speed lines, using Fj = ( w / g ω j rx for any convenient r x. For each speed of equilibrium ω 1, ω 2, ω 3 etc. determined by the experiment, find the radii of rotation r 1, r 2, r 3..etc by the intersection of speed lines with F v/s r curve as illustrated in Fig. Determine the corresponding value of sleeve height H. Hence calculate the lift (H 2 -H 1 of the sleeve and compare with the corresponding value used in the experiment.

6 ANSWER THE FOLLWING QUESTIONS: Give two practical uses of governors. Define stability, controlling force, sensitiveness, isochronisms and capacity of the governor in general. Differentiate between Watt and Porter governors. Is Watt governor stable throughout its range? Is Porter governor stable for all radii of rotation? Is Proell governor stable at all speeds of rotation? Show stable and unstable regions on F v/s r curve. What is the effect of friction force at the sleeve on speed range? Compare controlling force, energy capacity and sensitivity of Watt, Porter and Proell governors. State the assumptions made in deriving the expressions for controlling force F. 1 Draw a 4-bar mechanism operated by the movement of sleeve to open or close the opening of the fuel pump or throttle valve.

7 EXPERIMENT II-3A MASS MOMENT OF INERTIA OF A ROTOR OBJCTIVE: To study gyroscopic principle and determine mass moment of inertia of the rotor. Record your reading as per following: Plot torque v/s ω s ω p and estimate I r from the slope of the line. ω s (rad/sec Weight (kg Torque (N.m Time for precession (sec No. of precession ω p (rad/sec. I r (kg m 2 Low speed High speed To check the moment of inertia of the rotor by torsion pendulum method: 1 GIw f = 2π I l Hz (SI units r 4 π d I w = for the wire or (m 4 32 d w = diameter of the wire (m I r = rotor inertia kg m 2 G = modulus of rigidity 80 G Pa f = frequency of oscillations cycles/second (Hz Number of oscillations Time Frequency of the oscillations

8 In SI units 1 GIw f = 2π I l Hz r GIw Ir = Kg m π f l Compare the two results. ANSWER THE FOLLWING QUESTIONS: What are the possible uses of the gyroscope? Will the moment of inertia change if the rotor is taken to height? Give at least two examples of gyroscopic action. Define roll, pitch and yaw motions. Define free and restrained gyros.

9 EXPERIMENT II-3B BALANCING OF ROTATING MASSES OBJECTIVE: To study the effect of rotating unbalance and balancing of rotating masses. PROCEDURE Verify the theory of unbalancing a single revolving mass by taking a known unbalance mass and at known eccentricity but at least two distinct sets of distance for each case discussed in the theory. Verify the theory of balancing of multiple revolving masses by considering at least two distinct sets of unbalance revolving masses in different planes as discussed in the theory. ANSWER THE FOLLWING QUESTIONS: Give at least two ill effects of an unbalanced rotor. Give an example each for internal and external balancing. Give an example of statically unbalanced and dynamically unbalanced rotor. Can rotating masses be balanced completely? Can reciprocating masses be balanced completely in IC engines? How a crankshaft of an IC engine balanced? How many balanced masses are needed to balance ten unbalanced masses in a rotor?

10 EXPERIMENT II-5A BALANCING OF FOUR CYLINDER INLINE ENGINE MODEL OBJECTIVE: To study the resonance conditions in a 4-cylender in-line Variable Crank Angle apparatus. PROCEDURE Set the following crank angles and observe the balanced condition of the engine for primary and secondary forces and moments near resonances. Find the resonant frequencies. Plot the graph between Force vs. Speed (rpm and Moment vs. Speed(rpm.From the graph find out the resonant frequency at which amplitude of force and moments are maximum. The FFT analyser can be used to analyze the type of vibrations and to determine the operating range of speed. a. 0 0,180 0,180 0,0 0 b. 0 0,90 0,180 0,270 0 Can the mass of the pistons be adjusted in this experimental model? ANSWER THE FOLLWING QUESTIONS: 1 Will the resonance condition change, if cantilever beam is changed? 2 How should strain gauges be fitted on the cantilever to measure transverse and torsional vibrations?

11 OBJECTIVE EXPERIMENT II-5B EPICYCLIC GEAR TRAIN MECHANISM To study epicyclic gear train and determine experimentally the input torque, holding torque and output torque. Experimental procedure Check the experimental set up. Give supply to motor from control panel. Adjust the RPM of input shaft to some fix value. Apply holding torque just to hold the drum. This must be done carefully. Take the readings of loads of the holding drum & output drum as well as take readings input & output RPM. Repeat the same procedure for next reading. Summarize your results in the following table: S. Voltage Current Speed I/P No. (DC V ( DC V shaft N 1 Speed O/P shaft N 2 Holding spring balance reading (T 1 -T 2 kg O/P Spring balance reading, (T 3 -T 4 kg Calculation: S. No. Actual gear Theoretical Input torque Holding torque Output torque ratio gear ratio (kg m (kg m ( kg m ANSWER THE FOLLOWING QUESTIONS: What is the degree of freedom of epicyclic gear trains? Why these gear trains are called epicyclic or planetary gear?

12 EXPERIMENT II-6 UNIVERSAL VIBRATION MACHINE PROCEDURE Adjust damper at particular setting. Disturb system by hand and trace the decaying vibration of rotation drum. From the decaying curves determine the natural frequency, logarithmic decrement and the damping factor. For each damper setting of Method 1 excite the system by unbalance weight attached to the disc coupled with the motor. Running motor at speed (resonant speed giving maximum amplitude, the displacement trace in rotating drum and phase angle trace on the rotating disc are taken. For speeds (at least four below and the resonant speed (giving maximum amplitude, the displacement and phase angle traces are obtained. Plot the frequency response curves H(ω v/s ω/ω n from equation (6 and phase relationship O v/s ω/ω n from equation (7 of a single degree freedom system. Find exact resonant speed. Change the damper setting and first repeat (1 and (2 of Method 1 and then repeat (3 and (4 of Method Compare the results obtained by two methods. For each damper setting of Method 1, study the vibrations of the system, to plot magnification factor, phase angle v/s frequency curves and determine damping factors.

13 OBSERVATION TABLE Damper setting No.of cycles of oscillation Initial amplitude X 0 Final amplit ude X 0 Log Decrem ent From (1 Damping factor From (2 Damping period τ d From response curve ω n Through observation and also through calculation from (3

Varuvan Vadivelan. Institute of Technology LAB MANUAL. : 2013 : B.E. MECHANICAL ENGINEERING : III Year / V Semester. Regulation Branch Year & Semester

Varuvan Vadivelan. Institute of Technology LAB MANUAL. : 2013 : B.E. MECHANICAL ENGINEERING : III Year / V Semester. Regulation Branch Year & Semester Varuvan Vadivelan Institute of Technology Dharmapuri 636 703 LAB MANUAL Regulation Branch Year & Semester : 2013 : B.E. MECHANICAL ENGINEERING : III Year / V Semester ME 6511 - DYNAMICS LABORATORY GENERAL