Mechanical Engineering Answers

A circle of diameter d= 9 in. is scribed on an

unstressed aluminum plate of thickness t = 3/4

in. Forces acting in the plane of the plate later

cause normal stresses Sx = 12 ksi and sz= 20

ksi.

For E = 10x106 psi and n = 1/3, determine the

change in:

a) The length of diameter AB,

b) The length of diameter CD,

c) The thickness of the plate, and

d) The volume of the plate.

The tension on the tight side of the flat belt is 800N and the coefficient of friction between

the belt and the pulley is 0.3. The angular speed N, angle of lap and the diameter D of the

pulley are 300rpm, 150o and 30cm respectively. Without the addition of centrifugal tension,

determine;

(a) Initial tension of the belt.

(b) Power transmitted at this speed in kilowatts.

Calculate a suitable diameter for a solid shaft to transmit power of 200kW when

running at 180rev/min if the maximum shear stress in the shaft must not exceed

85N/mm2

Assume 5 ft3/s of Hydrogen at 15 psia and 80 oF are compressed during an irreversible adiabatic  process to 90 psia and 522 oF. For a non-flow process determine a) k, b) V2, c) W, d) ΔU and e) ΔS.

6. The working substance for a Carnot cycle is 8 lb m of air. The volume at the beginning of isothermal

compression is 9 ft 3 and the pressure is 300 psia. The ratio of expansion during the addition of heat is

2 and the temperature of the cold body is 90 o F. Find: a) Q A and Q R (BTU), b) V 3 and P 3 , c) V 4 and P 4 , d) mean effective pressure (psia).

5. For an ideal Diesel cycle with the over-all value of k=1.33, rk=15, rc=2.1, P 1 = 14.2031 psia, find P 2 and

mean effective pressure.

4. There are supplied 320 KJ/cycle of Diesel engine operating on 250 g of air P 1 =97.91 KPa, T 1 =48.9C.

At the end of compression, P 2 =3930KPa. Assume that air and the product within the cycle have air

properties. Determine compresion ratio, cut-off ratio, Wnet, thermal efficiency, and mean effective

pressure.

3. An ideal Diesel engine operates on 1.5 lb of air with a suction state at 14.1 psia and 100 o F. The

pressure at the end of compression is 475 psia and the cut –off is 6% of the stroke from head –end

dead - center. Using air properties (R=53.34 ft-lbf/lbm-R, k=1.4, Cp =.24, Cv=.1714 Btu/lbm-R),

determine compression ratio, percentage clearance, Qa, Qr, Thermal Efficiency, mean effective

pressure.

2. An ideal Otto engine, operating on the hot-air standard with k=1.34, has a compression ratio of 5. At

the beginning of compression the volume is 12 m 3 , the pressure is 95 kPaa and temperature is 38 oC.

During constant – volume heating, 370 kJ are added per cycle. Compute T 3 , P 3 , T 4 , Qa, Qr, Wnet,

thermal Efficiency, and mean effective pressure.

An Otto cycle with a compression ratio of 7.5 operates from the suction conditions of 14.2 psia, 85 o F.

Find the pressure and temperature at the end of compression, a) if cold air (k=1.4) is the working

substance, b) if hot air (k=1.32) is the working substance.