JNTU B.Tech III THERMAL ENGINEERING Previous Question Paper (May/June - 2019 - R15)

Compare and contrast Preignition and knocking.

Explain the significance of turbulence in IC engines.

What are the techniques available for the measurement of frictional power?

Give the composition of exhaust gas of an IC engine.

Define volumetric efficiency of reciprocating compressor and what are the factors affecting that?

Differentiate between fan and blower in different aspects.

Explain the working principle of steam nozzle.

Give the complete details of Wilson line.

Explain the features of De Laval turbine.

What is the role of degree of reaction in Reaction turbine?

Explain different stages of combustion in SI engine. With the help of p-ϕ diagrams both theoretical and actual.

Explain the various factors that influence the flame speed.

Explain the phenomenon of knock in CI engines and compare it with SI engine knock.

Bring out clearly the process of combustion in CI engines and also explain the various stages of combustion.

Define air fuel ratio and briefly state its effect on power output, fuel consumption and combustion pressure.

A single- cylinder, four- stroke Diesel engine works in the following data: Cylinder bore = 15Cm, Stroke = 25Cm, Speed = 250rpm, Area of indicator diagram = 6 cm2, Length of the indicator diagram = 9 cm, Spring constant = 7.5 bar/ cm, Brake specific fuel consumption = 0.24kg/kWh, CV of fuel = 42000kJ/kg. Diameter of brake wheel = 70Cm, Rope diameter = 3.5cm, Brake load = 40kg (392.4N). Calculate: i) Brake power ii) Indicated mean effective pressure iii) Indicated power iv) Mechanical efficiency, and v) Indicated thermal efficiency.

Compare and contrast bmep and imep.

The following data results refer to a test on a single cylinder, two - stroke cycle engine: Indicated mean effective pressure = 550 kPa, Cylinder diameter = 21 cm, Piston stroke = 28cm, Brake torque = 628 Nm, Fuel consumption = 8.16 kg/h, Calorific value of fuel = 42700 kJ/kg. Calculate: i) Mechanical efficiency, ii) The indicated thermal efficiency, iii) The brake thermal efficiency, and iv) Brake – specific fuel consumption in kg/ kWh.

Derive equation for indicated work for a single acting compressor with clearance.

A single-stage, single-acting reciprocating air compressor receives air at 1.013 bar, 27°C and delivers it at 9.5 bar. The compressor has a bore = 250 mm, and stroke = 300 mm and it runs at 200 rpm. The mass flow rate of air is 200 kg/ h. Calculate the volumetric efficiency of the compressor.

Explain different methods for improvement of thermal efficiency of gas turbine.

Calculate required air - fuel ratio in a gas turbine plants, whose turbine and compressor efficiencies are 85 and 80% respectively, maximum cycle temperature is 875°C. The working fluid can be taken as air (Cp=1.8kJ/kg.K, γ= 1.4) which enters the compressor at 1 bar and 27°C. The pressure ratio is 4. The fuel used as calorific value of 42000 kJ/kg. There is loss of 10% of calorific value in combustion chamber.

Draw the line diagram and explain the working details of Volex high pressure boiler and its working ranges.

Derive the equation for discharge through an isentropic nozzle.

Explain the significance of critical pressure ratio and degree of under cooling in steam nozzle.

A convergent – divergent nozzle is supplied steam at a pressure of 10 bar, dry, saturated the exit pressure is 1 bar. The friction losses are equivalent to 5% of heat drop in the convergent portion. For a throat diameter of 1.47 cm, determine the mass flow rate and the exit diameter of the nozzle. Also, find the semi cone angle of the divergent portion if its length is 2.85 cm.

Derive an expression for maximum blade efficiency for an impulse turbine in terms of blade speed ratio.

In a single stage impulse turbine, the steam jet leaves the nozzles at 20° to the plane of the wheel at a speed of 670 m/s and it enters the moving blade at an angle of 35° to the drum axis. The moving blades are symmetrical in shape. Determine the blade velocity and diagram efficiency.

Prove the necessary condition in terms of blade angles for 50% reaction turbine.

A reaction turbine runs at 600 rpm and consumes 18000kg/h of steam. The exit angle of the fixed and moving blades are 25°. The axial velocity of flow is 0.75 times the blade velocity. Determine the drum diameter and blade height of a particular stage where steam pressure is 2 bar and it is 0.95 dry. Assume the power developed to be 15 kW and the tip leakage of steam as 7%.