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Anna University Chennai 2003 B.Tech Marine Engineering INE HEAT ENGINES AND APPLIED THERMODYNAMICS - Question Paper

Saturday, 02 March 2013 10:20Web

Time : 3 hours Maximum : 100 marks

ans ALL ques..
PART A — (10x2 = 20 marks)

1.Define enthalpy of a gas.
2.With reference to thermodynamic vapour cycle discuss the term Efficiency Ratio.
3.With reference to the reciprocating steam engine discuss the term diagram factor.
4.Explain the difference ranging from indicated and brake power for steam engines.
5.Write 2 differences ranging from impulse and reaction turbines.
6.In a reaction turbine, when the degree of reaction is zero, there is
(a)no heat drop in the moving blades
(b)no heat drop in the fixed blades
(c)maximum heat drop in the moving blades
(d)maximum heat drop in the fixed blades.
7.Reheating in a gas turbine
(a)increases thermal efficiency
(b)increases compressor work
(c)increases turbine work
(d)decreases thermal efficiency.
8.Define free air delivery with reference to air compressor.
9.Explain the term perfect intercooling regarding air compressors.
10.In a compressed air system the overall efficiency is
(a)the ratio of shaft output of the air motor to the shaft input to the compressor
(b)the ratio of shaft input to the compressor to the shaft output of the air motor
(c)the product of the shaft output of the air motor and the shaft input to the compressor
(d)none of the above.

PART B — (5x16 = 80 marks)

11.A steam turbine for a Turbo alternator, receives steam at 17 bar (absolute) and 330 deg. C and it exhausts at 0.07 bar (absolute)
(i)Draw a TS diagram and discuss the cycle. (5)
(ii)Calculate the network done per kg of steam flow. (3)
(iii)Calculate the Rankine efficiency of the cycle. (4)
(iv)Give 4 reasons why superheated steam is usually used for driving Steam Turbines. (4)
12.(a)A tanker uses a steam engine driven, reciprocating stripping pump for cargo operations. Dry saturated steam is supplied at 16 bar. The pressure at realease is 2.0 bar. The condenser pressure is 0.3 bar. presume the pressure drop to take place at a constant quantity. Neglect clearance and pump work. All pressures are absolute. Steam flow rate is 1000 kg/hr.
(i)find the power output of the engine (6)
(ii)find the efficiency of the replaced Rankine Cycle (6)
(iii)Explain why the Rankine cycle is replaced in true practice for Steam engines. (4)
Or
(b)(i)A single cylinder double acting steam engine is used for the anchor windlass of a large tanker. Piston diameter is 300 mm. Stroke is 450 mm. Mechanical efficiency is 84%. Steam is supplied at 14 bar. Back pressure is 0.25 bar. Cut off is 40% of stroke. Diagram factor is 0.73. compute the brake power developed when the engine is running at 120 rpm. (10)
(ii)Explain the subsequent terms (1) Mean effective pressure (2) Cut off quantity (3) Dead centre. (3x2 = 6)
13.(a)(i)Given that steam is expanded in a nozzle from a pressure of p1 to a
pressure p2, derive an expression for calculating the mass of steam
discharged through the Nozzle. presume initial velocity of steam is
zero. (13)
(ii)What is the meaning of the term critical pressure ratio? (3)
OR
(b)(i)An impulse steam turbine is fitted with nozzles with an angle of
20 deg. The steam velocity, after the nozzles is 1100 m/s. The blade velocity is 350 m/s. The blade velocity coefficient is 0.78. Mass flow of steam is 0.7 kg/s. presume blading to be symmetrical. compute the subsequent (1) Blade inlet angle (2) Driving force on the wheel (3) Axial thrust on wheel (4) Power developed by the turbine.
(4 ? three = 12)
(ii)Briefly compare the various methods of compounding used for steam turbines. (4)
14.(a)(i)In a gas turbine installation, the air is compressed in a single stage
compressor from one bar to 6.25 bar and from an initial temperature
of 20 deg Celsius. The air after compression is heated in a chamber
to a temperature of 750 deg Celsius. The hot air is expanded in the
turbine and then reheated to a temperature of 750 deg Celsius. The
hot air is once again expanded in secondturbine. obtain the power
that can be developed per kg of air. All pressures are absolute
values. presume compression and expansion to be isentropic. (14)
(ii)Give 2 uses of gas turbine on board ships. (2)
Or
(b)(i)Describe with a layout diagram, an open cycle marine gas turbine plant. (8)
(ii)Give 4 points of comparison ranging from an open cycle and a closed cycle gas turbine plant. (4)
(iii)Give 4 points of comparison ranging from gas turbine and I.C Engine.
(4)
15.(a)Starting air compressors used in ships are usually of multi stage reciprocating kind. With respect to this,
(i)Write 4 advantages of multi–stage compression. (4)
(ii)A starting air compressor is of 2 stages, single acting, and reciprocating kind. It draws in air at one bar. The temperature in the E/R is 32 deg C. Final discharge pressure is 35 bar. After the intercooler the air is at 42 deg C and 5.6 bar pressure. If the compressor is to compress three cu.m of air at the inlet conditions per minute, estimate the work done by the compressor. All pressures are absolute values. (12)
Or
(b)(i)Derive an expression for calculating the work done by a Single stage Reciprocating Air compressor neglecting clearance quantity.
(12)
(ii)What is the effect of clearance quantity on work done and volumetric efficiency? (4)