Bengal Engineering and Science University 2006 B.E Electrical Engineering Thermal Power Plant - Question Paper
The ques. paper is with the attachment in pdf format. Ex/BBSUS/ME-806/2/ 06
B.E. (EE) Part-IV 8th Semester Examination, 2006
(Elective-Ill) (ME-806/2)
Time : 3 hours Full Marks : 100
Use separate answerscript for each half. Answer SIX questions, taking THREE from each half.
The Questions are of equal value. Use of Steam table & Mollier Diagram allowed.
FIRST HALF
1. a) Define 'net heat rate' for a power plant. Estimate the net heat rate for a coal
fired unit which has an overall efficiency of 40%. If the unit supplies 210 MW net power to the grid, what will be its auxiliary consumption and auxiliary efficiency if the boiler thermal efficiency is 92%, the cycle efficiency is 50%, turbine mechanical efficiency is 94% and generator efficiency is 96%?
b) Why a Deaerator is required in a steam power plant? How does it differ from a feed water heater?
2. a) Discuss the process of 'natural circulation' in a drum type boiler and mention
the factors on which it depends. What is 'circulation ratio'? For a boiler the furnace walls are 18 m high and they receive saturated water from down comer at 90 bar. Assuming a circulation ratio of 12, calculate the pressure head of natural circulation .
b) Briefly discuss, with the help of a suitable diagram, the balanced draught system for a boiler.
3. a) Why steam temperature control is important in a power boiler and what are
the factors that affect the superheat steam temperature? Briefly discuss different types of desuperheaters generally employed in a power plant boiler.
b) With a neat schematic, describe the control philosophy for a spray desuperheater.
4. a) Mention the shortcomings of a single-element drum level control system
and state how they are overcome in a three-element drum level control system. Give a neat sketch of three-element control.
b) With a neat diagram describe the hot well level control for a steam power plant.
5. Write short notes on any three :
i) B.M.S
ii) Sliding pressure control for steam power plant
iii) Cross-limited combustion control iv) Gas bypass control of steam temperature v) Forced
circulation in boilers.
SECOND HALF
6. a) When does reheating of steam become necessary? Explain the effect of re heat
on cycle output and efficiency.
b) Steam at 150 bar and 500C is supplied to a steam turbine. It expands to 40 bar and 300C. It is then reheated to 480C and expands to 8 bar and 280C. The steam coming out from the second expansion of the turbine is further reheated to 480C and expands to a condenser pressure of 0.06 bar. The steam entering into the condenser is dry saturated. Assume pressure loss in the first and second heater as 1 bar and 0.5 bar respectively. Obtain the following:
i) thermal efficiency of the cycle and power developed if the flow of steam is 8.5 kg/sec, through the turbine and ii) the isentropic efficiencies of the expansion stages.
Neglect pump work.
8. a) Draw a schematic diagram of a bubbling fluidized bed boiler and explain how it operates. State its advantages, b) Discuss in detail, the advantages of a CFB boiler.
9. a) An input-output curve, of a 12MW power station is expressed as follows :
I = (12 + 8L + 0.3L2)xl06, where I is in kJ/hour and L is in MW.
i) Find the load at which the maximum efficiency occurs, without plotting any curve.
ii) Find the increase in input required to augment station output from 5 kW to 7 kW by means of the input output-curve and also by incremental rate curve.
b) The following data relates to a 12MW power station :
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Cost of plant Interest, insurance and taxes Depreciation Cost of primary distribution Interest, Insurance, taxes and depreciation Cost of coal including transportation Operating cost Plant maintenance cost i) Fixed ii) Variable Installed plant capacity Maximum demand Annual load factor Consumption of coal Determine the following : i) Cost of power generation per kW per year ii) Cost per kWh generated iii) Total cost of generation per kWh. |
Rs. 1100 per kW 5% per annum 4% Rs. 6,00,000 5% Rs. 40 per tonne Rs. 4,50,000 Rs. 22,000 per annum Rs. 25,000 per annum 12MW 11MW 0.65 25,000 tonnes |
10. Write short notes on any three of the following :-
a) Different systems of solid injection in Diesel Engine power plant.
b) Pressurized Water Reactor (PWR)
c) Disposal of bled steam condensation
d) Advantages and disadvantages of gas turbine over diesel and steam power plants
e) Characteristic features of a Boiling Water Reactor (BWR).
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Attachment: |
| Earning: Approval pending. |
