DOM

KITE COLLEGE OF PROFESSIONAL ENGINEERING AND SCIENCES

DEPARTMENT OF MECHANICAL

III B.Tech II MID Examination

Sub:  DOM                                                                                                                                                           Date:

Branch: MECH                                                       Time: 1hr                                                                                                                                        Max marks: 10

Answer any Two questions                                                                                                                              2x5=10 M                                                                                    

1. The turning moment curve for an engine is represented by the equation, T = (20 000 + 9500 sin 2θ – 5700 cos 2θ) N-m, where θ is the angle moved by the crank from inner dead centre. If the resisting torque is constant, find: 1. Power developed by the engine ; 2. Moment of inertia of flywheel in kg-m2, if the total fluctuation of speed is not exceed 1% of mean speed which is 180 r.p.m; and 3. Angular acceleration of the flywheel when the crank has turned through 45° from inner dead centre.

2. The turning moment diagram of a four stroke engine may be assumed for the sake of simplicity to be represented by four triangles in each stroke. The areas of these triangles are as follows: Suction stroke = 5 × 10–5 m²; Compression stroke = 21 × 10–5 m²; Expansion stroke =

85 × 10–5 m²; Exhaust stroke = 8 × 10–5 m². All the areas excepting expression stroke are negative. Each m² of area represents 14 MN-m of work. Assuming the resisting torque to be constant, determine the moment of inertia of the flywheel to keep the speed between 98 r.p.m. and 102 r.p.m. Also find the size of a rim-type flywheel based on the minimum material criterion, given that density of flywheel material is 8150 kg/m³ ; the allowable tensile stress of the flywheel material is 7.5 MPa. The rim cross-section is rectangular; one side being four times the length of the other.

3. Derive the equation for hartnell governor

4. A shaft carries four masses A, B, C and D of magnitude 200 kg, 300 kg,400 kg and 200 kg respectively and revolving at radii 80 mm, 70 mm, 60 mm and 80 mm in planes measured from A at 300 mm, 400 mm and 700 mm. The angles between the cranks measured anticlockwise are A to B 45°, B to C 70° and C to D 120°. The balancing masses are to be placed in planes X and Y. The distance between the planes A and X is 100 mm, between X and Y is 400mm and between Y and D is 200 mm. If the balancing masses revolve at a radius of 100 mm, find their magnitudes and angular positions.