Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech III THERMAL ENGINEERING – II Previous Question Paper (March/April - 2021 - R16)
Answer any five questions. All questions carry equal marks.
Main
Explain about the construction details of Lamount boiler with a neat sketch.
Answer
A LaMont boiler is a high-pressure, forced-circulation water-tube boiler. Its construction consists of a centrifugal pump that forces water through the boiler tubes to ensure continuous circulation, preventing the formation of steam bubbles on the tube surfaces which could lead to overheating. The main components include a feed pump, an economizer, an evaporator, a superheater, and a steam separator drum.
Water from the feed pump passes through the economizer to the steam separator drum. The circulating pump draws water from the bottom of the drum and forces it through the evaporator tubes, which are arranged in the furnace walls to absorb heat. The resulting steam-water mixture returns to the drum, where the steam is separated and sent to the superheater. The sketch would show the closed-loop circulation path starting from the drum, through the circulating pump, into the radiant and convective heating surfaces, and back to the drum.
A steam power plant is working based on Rankine cycle, in which the steam enters the turbine at 50 bar and 500 C and expanded up to 0.01 bar. If the mass flow rate of steam is 20 kg/s, then calculate (i) quality of steam at the exit of the turbine (ii) cycle efficiency (iii) net work output (iv) capacity of the plant.
Answer
Given: P1 = 50 bar, T1 = 500 C, P2 = 0.01 bar, m = 20 kg/s.
From steam tables:
At 50 bar, 500 C: h1 = 3433.8 kJ/kg, s1 = 6.977 kJ/kgK.
At 0.01 bar: hf = 19.18 kJ/kg, hfg = 2432.9 kJ/kg, sf = 0.071 kJ/kgK, sfg = 8.150 kJ/kgK.
(i) Quality of steam (x2): Since s1 = s2, 6.977 = sf + x2(sfg), 6.977 = 0.071 + x2(8.150), x2 = 0.847.
(ii) Cycle efficiency: h2 = hf + x2(hfg) = 19.18 + 0.847(2432.9) = 2079.8 kJ/kg. Work done by turbine Wt = h1 - h2 = 3433.8 - 2079.8 = 1354 kJ/kg. Pump work Wp = vf(P1 - P2) = 0.001(5000 - 1) = 5 kJ/kg. Net work Wnet = 1354 - 5 = 1349 kJ/kg. Heat supplied Qs = h1 - hf_at_P1 = 3433.8 - 1154.7 = 2279.1 kJ/kg. Efficiency = Wnet / Qs = 1349 / 2279.1 = 0.5919 or 59.19%.
(iii) Net work output: Pnet = m * Wnet = 20 * 1349 = 26980 kW.
(iv) Capacity of the plant: The capacity is 26.98 MW.
Define and derive the terms equivalent evaporation and boiler horse power.
Answer
Sign in to view the complete answer paper.
Determine the throat area, exit area and exit velocity for a steam nozzle to pass a mass flow of 0.3 kg/s when inlet conditions are 10 bar and 250 C and the final pressure is 2 bar. Assume expansion is isentropic and that the inlet velocity is negligible. Use
Answer
Sign in to view the complete answer paper.
Explain different types of compounding of impulse turbine and give examples.
Answer
Sign in to view the complete answer paper.
A Delavel turbine is designed to operate to generate 40 MW of power. The steam enters the blades at nozzle angle of 20° with an absolute velocity of 300 m/s. If the blade velocity is 75 m/s, then calculate (i) blade work (ii) blade efficiency (iii) mass flow rate of steam.
Answer
Sign in to view the complete answer paper.
Explain about the working and construction details of Low-level jet condenser and High-level jet condenser.
Answer
Sign in to view the complete answer paper.
Define and derive the degree of reaction and show that its value is 0.5 for Parson turbine.
Answer
Sign in to view the complete answer paper.
What is super saturation of steam nozzles and discuss its effect on performance.
Answer
Sign in to view the complete answer paper.
Derive the condition for maximum blade efficiency of impulse turbine.
Answer
Sign in to view the complete answer paper.
What are the sources of air leakage in the steam condensers? How to control the leakage?
Answer
Sign in to view the complete answer paper.
A gas turbine is operated between the minimum temperature of 298 K and a maximum temperature of 1500 K. Then calculate (i) optimum pressure ratio (ii) net work output (iii) work ratio (iv) back work ratio and (v) capacity of the plant, if mass of air is 8 kg/s.
Answer
Sign in to view the complete answer paper.
What are the desirable characteristics for the good combustion chamber for the gas turbine? Explain.
Answer
Sign in to view the complete answer paper.
Describe the working of turbojet engine with a diagram and discuss its thermodynamic analyses.
Answer
Sign in to view the complete answer paper.
Explain different thrust augmentation techniques used for air breathing engines.
Answer
Sign in to view the complete answer paper.
Describe the solid propellant rocket with a diagram.
Answer
Sign in to view the complete answer paper.