Archive for May, 2009

Unit-I

• Discuss the composition, specific properties and main applications of the following materials: a) Mild steel (Low carbon steel) (b) High carbon steel (c) High speed steel (d) Stainless steel.

OR

• Describe the mechanical properties of materials: (a) Tensile strength (tensile stress) (b) Hardness (c) Fatigue strength (d) Modulus of elasticity (e) Toughness.

Unit-II

• Explain the following properties of any measuring instruments: (a) Hysteresis (b) Sensitivity (c) Response time (d) Precision and accuracy.

OR

• With the help of a simple diagram explain various parts of a lathe machine and also enumerate various operations which can be performed on it.

Unit-III

• What is Newton’s law of viscosity. A plate rquires 2 N force per unit area or 2 N/m² to move with a velocity of 60 cm/s over a fixed plate. The distance between two plates is 0.03 mm. Determine the fluid viscosity between the plates.

OR

• Derive the Bernoulli’s equation from Euler’s equation for an ideal flow. The water is flowing through a pipe having diameters 20 cm at inlet section 1 and 10 cm at outlet section 2. The rate of flow through pipe is 35 litres/s. The section 1 is 6 m above datum and section 2 is 4 m above datum. If pressure at section 1 is 39.24 N/cm², find the intensity of pressure at section 2.

Unit-IV

• Explain the First Law of Thermodynamics with suitable examples. In a gas turbine the gas enters at the rate of 5 kg/s with a velcity of 50 m/s and enthalpy of 900 kJ/kg and leaves the turbine with a velocity of 150 m/s and enthalpy of 400 kJ/kg. The loss of heat from the gases to the surroundings is 25 kJ/kg. Assume for gas R = 0.285 kJ/kg-K and Cp = 1.004 kJ/kg-K and the inlet section conditions to be at 100 kPa and 27ºC. Determine the power output of the turbine and diameter of the inlet pipe.

OR

• Give the two statements of Second Law of Thermodynamics. Which is the more effective way to increase the efficiency of a Carnot engine: To increase T1 keeping T2 constant or To decrease T2 keeping T1 constant. where T1 is the source temperature and T2 is the sink temperature.

Unit-V

• Show that the efficiency of the Otto cycle depends only on the compression ratio. In a SI engine working on the ideal Otto cycle, the compression ratio is 5.5. The pressure and temperature at the beginning of compression are 1 bar and 27 ºC respectively. The peak pressure is 30 bar. Determine the pressure and temperatures at the salient points, the air-standard efficiency and the mean effective pressure. Assume ratio of specific heats to be 1.4 for air.

OR

• What is the basic difference between an Otto cycle and a Diesel cycle? Derive the expression for the efficiency and mean effective pressure of the diesel cycle.