Applied Thermodynamics - Dec 2013

Mechanical Engg. (Semester 4)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) Define the therms: i) Stoichiometric air; ii) Enthalpy of combustion iv) Enthalpy of formation; v) Adiabatic flame temperature.(10 marks) 1 (b) The volumetric composition of dry fuel gases obtained by the combustion of an unknown hydrocarbon is 12.7% CO₂, 0.9% CO, 3.9% O₂ and 82.5% N₂ Determine: i) Composition of the fuel; ii) Theoretical air required for complete combustion ; iii) Percentage of excess air required.(10 marks) 2 (a) With the help of P-V and T-S diagrams, derive an equation for theoretical air standard efficiency of a semi diesel (dual) cycle in terms of compression ratio, cut off ratio and explosion ratio, with suitable assumptions.(10 marks) 2 (b) In an air standard diesel cycle the compression ratio is 15 and the fluid properties at the beginning of compression are 100kPa and 300K. For a peak temperature of 1600K calculate i) the percentage of stroke at which cut off occurs; ii) the cycle efficiency and iii) the work output/kg.(10 marks) 3 (a) Describe the following as applied to I.C engine i) Morse test ii) Heat balance sheet.(8 marks) 3 (b) During a test on a single cylinder 4 stroke oil engine the following observation were made Bore=30cm, stroke=45 cm, duration of trail =1hr , total fuel consumption=7.6 kg calorific value of fuel=45,000kJ/kg. Total revolution made=12000, mean effective pressure 6 bar, net brake load=1.47 kN. Brake drum diameter 1.8m rope diameter 3cm. Mass of jacket cooling water circulated=550kg water enters at 15°C water leaves at 60°C. Total air consumption 360kh room temperature 20°C, exhaust gas temperature 300°C, calculate: i) Indicated and break power ii) Indicated thermal efficiency iii) Mechanical efficiency ; iv) Draw the heat balance sheet on minute basis(12 marks) 4 (a) Why Carnot cycle is not used as a reference cycle for steam power plant?(3 marks) 4 (b) Sketch the flow diagram and corresponding T-S diagram,of a reheat vapour cycle and derive an expression for reheat cycle efficiency(7 marks) 4 (c) A 40MW steam power plant working on Rankine cycle operates between boiler pressure of 4MPa and condenser pressure of 10 kPa. The steam leaves the boiler and enters the steam turbine at 400°C. The isentropic efficiency of steam turbine is 85%. determine : i) The cycle efficiency ii)The quality of exhaust steam turbine and iii) Steam flow rate in kg/hr considering pump work.
Properties of steam