B.TECH - Semester 4 thermal engineering Question Paper 2019 (jun)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- Sketch the Rankine cycle on $\mathrm{p}-\mathrm{V}$ and T -s diagrams when the steam supplied to the prime mover is dry saturated.
- Explain super saturated flow of steam through nozzle.
- Define reheat factor and degree of reaction as applied to steam turbines.
- What are the factors affecting detonation?
- What is meant by stoichiometry ? Define equivalence ratio.
- Define cetane number of a fuel. How is it related to knocking tendency in Cl engines?
- Name the different types of combustion chambers used for Gas turbines. Explain the advantages of each type over others.
- What do you meant by volumetric efficiency of compressor?
- What are the functions of an inter cooler in multistage air compressor? What is meant by perfect inter cooling?
- Explain the compression process of roots rotary compressor with the help of p-V diagram. ( $10 \times 4=40$ Marks) PART - B Answer one full questions from each Module.
- (a) Describe with a neat sketch the working of a binary vapour cycle.
- (b) Steam at 28 bar and $50^{\circ} \mathrm{C}$ superheat is passed through a turbine and expanded to a pressure where the steam is dry saturated. It is then reheated at constant pressure to its original temperature of $56^{\circ} \mathrm{C}$ and exp...
- (i) work done per kg of steam (ii) Thermal efficiency with and without reheat.
- (a) Derive an expression for the critical pressure ratio for the maximum flow rate of steam through nozzle.
- (b) In a De-Laval turbine steam issues from the nozzle with a velocity of $1200 \mathrm{~m} / \mathrm{s}$. The nozzle angle is $20^{\circ}$, the mean blade velocity is $400 \mathrm{~m} / \mathrm{s}$, and the inlet and outlet angles of blades are equa...
- (i) Blade angles (ii) Tangential force on the blades (iii) Power developed (iv) Blade efficiency. Take blade velocity coefficient as 0.8 .
- (a) Explain the pre-ignition in spark ignition engines. How it is detected?
- (b) Dry exhaust gas from an oil engine has the following composition by volume $\mathrm{CO}_{2}-8.85 \% \mathrm{CO}-1.2 \% ; \mathrm{O}_{2}-6.8 \% ; \mathrm{N}_{2}-83.15 \%$. The fuel composition by mass is $\mathrm{C}-84 \% ; \mathrm{H}_{2}-14 \%$ a...
- (i) mass of carbon per Kg of dry flue gas and (ii) A/F ratio.
- (a) Discuss the methods of improving the performance of simple open cycle gas turbine plant.
- (b) A simple open cycle gas turbine plant draws an air at 1 bar absolute and $17^{\circ} \mathrm{C}$ and compresses it through a pressure ratio of 4 . The air passes to the combustion chamber and after combustion of fuel. gases enter the turbine at a...
- (i) The net power output if it has to handle 100 Kg of air per minute (ii) The thermal efficiency of the plant. Assume for both air and gas $\mathrm{C}_{\mathrm{p}}=1.025 \mathrm{~kJ} / \mathrm{kgK}$ and $\gamma=1.4$. Neglect the addition of fuel we...
- (a) Describe briefly an axial flow compressor.
- (b) A single acting two stage compressor with complete inter cooling delivers $6 \mathrm{~kg} / \mathrm{min}$ of air at 15 bar. Assuming an intake at 1 bar and $15^{\circ} \mathrm{C}$ and compression and expansion with the law $P V^{1.3}=\mathrm{C}$;...
- (i) Power required to run the compressor (ii) Free air delivered per sec. (iii) Isothermal efficiency. (iv) If clearance ratios for LP and HP cylinders are 0.04 and 0.06 , calculate volumetric efficiency and swept volume for each cylinder.
- (a) Derive the expression for work done per kg of air compressed in a reciprocating air compressor with clearance volume $\mathrm{V}_{\mathrm{c}}$.
- (b) A single stage single acting compressor delivers $15 m^{3}$ of free air per minute from 1 bar to 8 bar. The speed of compressor is 300 rpm . Assuming that compression and expansion follow the law $\mathrm{PV}^{1.3}=\mathrm{C}$. and the clearance ...