THERMAL ENGNERRING-II ASSIGNMNET-I
1.(a).Explain with help of neat diagrams a regenerative cycle. Derive also an expression for its thermal efficiency
(b).In a regenerative cycle the inlet conditions are 40 bar and 400oC.Steam is bled at 10 bar in regenerative heating. The exit pressure is 0.8 bar. Neglect the pump work, determine the efficiency of the cycle
2.(a).Define the terms HCV and LCV of a fuel and state which value is used and why in calculations affecting the performance of a power plant.
(b).A sample of fuel has the following percentage analysis by weight: Carbon=82%,Hyderogen=5%,Oxygen=4%,the remainder being inert material. Estimate the HCV AND LCV of this fuel. The following heating values may be used: Carbon=32400 KJ/kg, free hydrogen=137600 KJ/kg. Assuming tat each kg of steam produced during combustion absorbs 2332Kj.
3.(a). Establish a condition foe maximum discharge of flue gases through chimney
(b).Calculate the draught in mm of water column produced by a chimney 30 m high when the average temperature of hot gases is 225oC and the temperature of outside air is 20oC.The quantity of air supplied is 18 kg/kg of fuel.
4.What is compounding: describe various ways of compounding impulse turbine and gives their merits and demerits.
5.(a).Explain the terms over expanding and under expanding as applied to a fluid flow through a nozzle?
(b).Describe the changes which occur in a convergent divergent nozzle as the back pressure is slowly increased from the design pressure up to the pressure at entry.
6.(a).How does a modifies rankine cycle differ from rankine cycle? Write also the expression of modifies rankine cycle efficiency
(b) Compare the rankine cycle efficiency of high pressure plant operating from 80 bar and 400oC and a low pressure plant operating from 40 bar and 400 oC, if the condenser pressure in both cases is 0.07 bar.
7.(a)Define equivalent evaporation and boiler efficiency.
(b).A boiler is to provide 7000 kg/hr of stem with superstauterd by 40oC at a pressure of 20 bar. The temperature of water is 60oC,If the thermal efficacy of the boiler is 75%,how much fuel will be consumed in one hour?.The calorific value of oil used is 45000kJ/kg. Take specific heat of superheated steam as 2.093 kJ/kg K and also calculate the equivalent evaporation from and at 100 oC.
8.(a).What are the effects of super saturation on discharge and heat drop?
(b).Steam enters into a convergent divergent nozzle at 2.2 MN/m2,260oC and leaves at 0.4MN/m2.Assuming frictionless up to the throat and nozzle efficiency of 85%,determine
i.Flow rate in kg s for a throat area of 32.2cm2 ii.exit diameter in cm
iii.length of the divergent portion if the cone angle is10o
9.(a)Describe different processes of rankine cycle .Derive the expression for its efficacy and show them on P-v and T-s diagrams
(b).As impulse ranine cycle works between pressure of 30 bar and 0.04 bar, the initial condition of steam being dry saturated calculate the cycle efficiency, work ratio and specific steam consumption.
10.The following pertains to steam boiler:pressure-14 bar, capacity=5000 kg/hr, fuel consumption=675 kg/hr, CV of fuel =29680 Kj/kg ,inlet temp of water to economizer=30oC,exit temperature of water from economiser =130oC,quality of steam produced in the boiler =0.97,tenmperature of steam produced in superheater =320oC,calculate
(a).equivalent evaporation kg/hr (b) overall efficiency of the plant © boiler efficiency
(d).Economizer efficiency (e)super heater efficacy
11.(a).Derive the expression relating the critical pressure ratio to the index of expansion n ,for expansion in nozzle.
(b).find the maximum discharge and exit diameter of a convergent nozzle which receives dry saturated steam at 15 bar and discharge to an impulse turbine at 0.3 bar. Neglect friction and take throat diameter equal to 8 mm
12. an impulse turbine with a single row wheel is to develop 100 kW and the blade speed is 150 m/s. A mass of 2 kg/s is to flow trough the nozzle with exit velocity of 350 m/s. The velocity coefficient of the blade is 0.8,while the steam is to flow axially after passing through the blade ring. Find out the nozzle angle and the blade angles at exit and inlet/also calculate the diagram efficiency
13. In a two stage velocity compounded steam turbine the mean blade speed is 150m/s while the steam velocity as it issued from the nozzle is 675 m/s. The nozzle angle is 200. The exit angles of first row moving blades, fixed blades and the second row moving blades are 250, 250 and 300 respectively. The blade friction coefficient is 0.9 for all blades. Determine for a flow rate of 4.5 kg/s
(a) the power output (b) the diagram efficiency.
14.(a) What do you mean by choked flow in nozzles?
(b) Steam at 10 bar and 0.96 dryness fraction is to be discharged at a rate of 100kg/hr through a convergent divergent nozzle to a back pressure of 1.4 bar, Find suitable diameters for throat and exit assuming 10% of the overall isentropic enthalpy drop reheats the steam in the divergent portion of the nozzle.
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