Mechanical Engineering Answers

1, Oil with a viscosity coefficient of 15 poise is filled between parallel plates spaced 5 mm apart. When the lower plate is fixed and the upper plate moves at a speed of 5 m/s. what is the shear stress (Pa) generated on the plate surface?

2, When 1200N of lead is suspended from the bottom of cube (wood) of 1 m on a side and placed in water, how many cm is the height of the piece of wood that rises above the water ? (the specific gravity of wood block is 0.4, the specific gravity of lead is 12, and the bottom of the wood block is kept horizontal.

Draw neat iron – iron carbide equilibrium diagram and indicate phases clearly.

a) Explain various invariant reactions with help of microstructures.

b) Consider a hypo eutectoid steel (C0 = 0.012 + 0.78 [X/106]) and hyper eutectoid steel ((C0 = 0.78 + 0.012 [X/106]) compositions and estimate pro-eutectoid phase fractions, for the given compositions.

c)Also estimate compositions of ferrite, Fe3C and phase fractions just below eutectoid temperature.

Note: Also calculate your compositions from the given equation (X is your sl. number) and indicate it. For each subsections (a,b,c) please draw a separate Fe-Fe3C diagram.

The crankpin of an engine sustains a maximum load of 35 kN due to steam pressure. If the allowable

bearing pressure is 7 N/mm2

, find the dimensions of the pin. Assume the length of the pin equal to 1.2

times the diameter of the pin.

The crankpin of an engine sustains a maximum load of 35 kN due to steam pressure. If the allowable

bearing pressure is 7 N/mm2

, find the dimensions of the pin. Assume the length of the pin equal to 1.2

times the diameter of the pin.

A surface condenser for a non reheat turbine exhausts 6 kg/sec of steam at 6.8 KPaa (tsat = 38.5C) with circulating water entering at 27C and a terminal temperature difference 4C. Overall coefficient of heat transfer is 3.6 KW/m2-C and water velocity is assumed to be 2.13 m/sec. Tube type ¾ in 18 BWG (OD = 17 mm; t = 1.3 mm). Tube sheet thickness is 12 mm. Assuming two tube passes design and 2210 KJ/kg of heat rejection, determine the actual length and total number of tubes required by the condenser. 

A steam turbine receives 362,500 kg/h of steam throttled at 8.7 MPa and 410OC. steam leaves the high pressure turbine shell at 2 MPa with 7.58 degrees of superheat. Reheated steam is at 1.9 MPa and 410OC. Condensate is at 78OC. For a generator output of 100 MW at 94% efficiency, calculate (a) the combined thermal efficiency, (b) the actual condition of exhaust steam, (c) the thermal efficiency of the ideal engine, (d) the combined engine efficiency, and (e) the ideal thermal efficiency of the cycle without pressure drop through reheater