Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech III THERMAL ENGINEERING - II Previous Question Paper (July/August - 2023 - R13)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
Compare and contrast the boiler Mountings and Accessories.
Answer
Boiler mountings are essential safety devices installed on the boiler for its proper and safe functioning, such as safety valves, water level indicators, and pressure gauges. In contrast, boiler accessories are auxiliary components installed to improve the overall efficiency and performance of the boiler plant, such as economizers, air preheaters, and superheaters.
While mountings are mandatory for safe operation, accessories are optional and chosen based on the desired plant economy and efficiency requirements.
What is meant by Reheating and its advantages?
Answer
Reheating is a process in a steam power plant where the steam is expanded in a high-pressure turbine, then withdrawn and reheated in the boiler (reheater) before being expanded further in a low-pressure turbine. This process allows the steam to remain in a dry state for a longer duration during expansion.
The primary advantages are:
- It increases the thermal efficiency of the cycle by allowing a higher mean temperature of heat addition.
- It significantly reduces the moisture content of the steam in the final stages of the turbine, which minimizes erosion of the turbine blades and improves the internal efficiency of the turbine.
- It allows for a higher overall work output from the turbine for a given mass flow rate of steam.
Write the classification of nozzles.
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Explain super saturated flow of steam in steam nozzles.
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Define i) Blade efficiency and ii) Stage efficiency.
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Explain velocity diagram of Parsons Reaction turbine with all notations.
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Discuss the merits and demerits of surface condensers over jet condensers.
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What are the different types of combustion chambers in gas turbines?
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Write equation for Thrust power and propulsive power.
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Explain thrust augmentation used in jet and rocket propulsion.
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Part B
What are the advantages and disadvantages of regenerative cycle over simple Rankine cycle?
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Discuss the working of fusible plug with the help of line diagram.
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Distinguish between water-tube and fire-tube boilers and state under what circumstances each type would be desirable.
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With the help of line diagram, explain the working of super critical boiler.
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Derive the equation for critical pressure ratio in nozzles.
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An impulse turbine of 1 MW has steam entering at 20 bar 300℃ and steam consumption of 8 kg per kW hour. Steam leaves at 0.2 bar and 10% of total heat drop is lost in overcoming friction in diverging portion of nozzle. If throat diameter of each nozzle is 1 cm then, determine (i) the number of nozzle required (ii) exit diameter of each nozzle. Solve using mollier chart/diagram.
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A group of convergent-divergent nozzles are supplied with steam at a pressure of 2 N/m2 and a temperature of 325℃. Supersaturated expansion according to the law PV1.3 = constant, occurs in the nozzle down to an exit pressure of 0.36 MN/m2. Steam is supplied at the rate of 7.5 kg/s. Determine the required throat and exit areas.
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What do you understand by nozzle? Discuss different types of nozzles.
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Draw the line diagram and velocity triangles and explain the working details of impulse turbine.
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Steam leaves the nozzle of a single stage impulse turbine at 850 m/s. The nozzle angle is 18° and the blade angles are 29° at the inlet and outlet. The friction coefficient is 0.9. Calculate blade velocity and steam mass flow rate in kg/hr to develop 300 W power.
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In a reaction turbine 6 kg/s steam is admitted at 15 bar dry saturated in the first stage. Turbine has eight pairs on mean diameter of 50 cm and run at 3000 rpm with mean blade speed to steam velocity ratio of 0.8. There occurs tip leakage of steam at all rows amounting to 10% of total and efficiency of working steam is 85%. Considering blade outlet angles for both fixed and moving blades to be 20°, determine the following analytically. i) The output from turbine in hp ii) The pressure of steam leaving turbine, iii) The mean blade height.
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Explain the working of single stage reaction turbine. Sketch pressure and velocity variations along the axis of the turbine. Show the expansion on h-s chart.
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What are the different types of Condensers? Classify.
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Describe the factors which influence the efficiency of a condensing plant.
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Explain the effect of regeneration, inter cooling, and reheating on the performance of gas turbine power plant.
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A gas turbine plant receives air at 1 bar and 290K and compresses it to 5bar. If the temperature of air after compression is 1000K. Find the thermal efficiency of the turbine. Take γ=1.4 for air.
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Showing the basic components, explain the working of turbojet engine.
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Describe working of semi-closed gas turbine cycle with the help of a neat sketch.
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State the fundamental difference between the jet propulsion and rocket propulsion.
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Derive the expressions for thermal efficiency, thrust and thrust power.
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