Exam Details
| Subject | Thermal Engineering - I | |
| Paper | ||
| Exam / Course | Diploma in Mechanical Engineering (DMEVI)& B.Tech. MECHANICAL ENGINEERING 1-4 (BTMEVI) | |
| Department | School of Engineering & Technology (SOET) | |
| Organization | indira gandhi national open university | |
| Position | ||
| Exam Date | December, 2016 | |
| City, State | new delhi, |
Question Paper
What are secondary fuels List some important secondary fuels.
What is the function of a safety valve in a boiler State the minimum number of safety valves to be used on a boiler.
Define the following as related to steam turbines (any two)
Speed ratio
Blade velocity coefficient
Diagram efficiency
Stage efficiency
Explain the difference between an impulse turbine and a reaction turbine.
3. The following readings were obtained during a boiler trial of 6 hours duration
Mean steam pressure =12 bar
Mass of steam generated 40000 kg
Mean dryness fraction =0.85
Mean feed water temperature= 30°C
Coal used =4000 kg
Calorific value of coal 33400 kJ/kg
Calculate:
Factor of equivalent evaporation
Efficiency of the boiler
4. In a stage of an impulse turbine provided with single row wheel, the mean diameter of the blades is 1 m. It runs at 3000 rpm. The steam issues from the nozzle at a velocity of 350 m/sec and the nozzle angle is 20°. The rotor blades are equiangular. The blade friction is 0·86. Calculate "the mean blade speed, if the axial thrust on the end bearing of a rotor is 120 N. Also calculate the mass flow rate in the turbine.
5. A turbojet engine consumes air at the rate of 60·2 kg/s when flying at a speed of 1000 km/hr. Calculate
Exit velocity of the jet when the enthalpy change for the nozzle is 230 kJ/kg and the velocity coefficient is 0.96.
Fuel flow rate in kg/s when the air-fuel ratio is 70 1.
Thrust specific fuel consumption.
Thermal efficiency of the plant when the combustion efficiency is 92% and the calorific value of the fuel used is 42000 kJ/kg.
Propulsive efficiency.
6. At a stage In a reaction turbine, the mean blade ring diameter is 1 m and the turbine runs at a speed of 50 rev/sec. The blades. are desired for 50% reaction with exit angle 30° and inlet angle 50°. The turbine is supplied with steam at the rate of 600000 kg/hr and the stage efficiency is 85%. Determine the power output of the stage.
7. A surface condenser deals with 13625 kg of steam per hour at a pressure of 0·09 bar. The steam enters 0'85 dry and the temperature at the condensate and air extraction pipes is 3Goe. The air leakage amounts to 7.26 kg/hour. Determine
the surface required, if the average heat transmission rate. is 3.97 kJ/cm^2 per second;
the cylinder diameter for the dry air pump, if it is to be single acting at 60 rpm with a stroke to bore ratio of 1·25 and volumetric efficiency of 0.85.
8. A single cylinder, compression ignition engine with a brake thermal efficiency of 30% uses high speed diesel oil having a calorific value of 42000 kJ/kg Determine BSFC in kg/kWh.
Explain the working differences between propeller-jet, turbojet and turbo-prop.
State the fundamental differences between jet propulsion and rocket propulsion.
10. A closed cycle ideal gas turbine operates between temperature limits of 800°C and 30°C, and produces a power of 100 kW. The plant is designed such that there is no need for a regenerator. A fuel of CV 45000 kJ/kg is used. Determine
the mass flow rate of air through the plant
the rate of fuel consumption.
Assume Cp= 1 y 1.4.
What is the function of a safety valve in a boiler State the minimum number of safety valves to be used on a boiler.
Define the following as related to steam turbines (any two)
Speed ratio
Blade velocity coefficient
Diagram efficiency
Stage efficiency
Explain the difference between an impulse turbine and a reaction turbine.
3. The following readings were obtained during a boiler trial of 6 hours duration
Mean steam pressure =12 bar
Mass of steam generated 40000 kg
Mean dryness fraction =0.85
Mean feed water temperature= 30°C
Coal used =4000 kg
Calorific value of coal 33400 kJ/kg
Calculate:
Factor of equivalent evaporation
Efficiency of the boiler
4. In a stage of an impulse turbine provided with single row wheel, the mean diameter of the blades is 1 m. It runs at 3000 rpm. The steam issues from the nozzle at a velocity of 350 m/sec and the nozzle angle is 20°. The rotor blades are equiangular. The blade friction is 0·86. Calculate "the mean blade speed, if the axial thrust on the end bearing of a rotor is 120 N. Also calculate the mass flow rate in the turbine.
5. A turbojet engine consumes air at the rate of 60·2 kg/s when flying at a speed of 1000 km/hr. Calculate
Exit velocity of the jet when the enthalpy change for the nozzle is 230 kJ/kg and the velocity coefficient is 0.96.
Fuel flow rate in kg/s when the air-fuel ratio is 70 1.
Thrust specific fuel consumption.
Thermal efficiency of the plant when the combustion efficiency is 92% and the calorific value of the fuel used is 42000 kJ/kg.
Propulsive efficiency.
6. At a stage In a reaction turbine, the mean blade ring diameter is 1 m and the turbine runs at a speed of 50 rev/sec. The blades. are desired for 50% reaction with exit angle 30° and inlet angle 50°. The turbine is supplied with steam at the rate of 600000 kg/hr and the stage efficiency is 85%. Determine the power output of the stage.
7. A surface condenser deals with 13625 kg of steam per hour at a pressure of 0·09 bar. The steam enters 0'85 dry and the temperature at the condensate and air extraction pipes is 3Goe. The air leakage amounts to 7.26 kg/hour. Determine
the surface required, if the average heat transmission rate. is 3.97 kJ/cm^2 per second;
the cylinder diameter for the dry air pump, if it is to be single acting at 60 rpm with a stroke to bore ratio of 1·25 and volumetric efficiency of 0.85.
8. A single cylinder, compression ignition engine with a brake thermal efficiency of 30% uses high speed diesel oil having a calorific value of 42000 kJ/kg Determine BSFC in kg/kWh.
Explain the working differences between propeller-jet, turbojet and turbo-prop.
State the fundamental differences between jet propulsion and rocket propulsion.
10. A closed cycle ideal gas turbine operates between temperature limits of 800°C and 30°C, and produces a power of 100 kW. The plant is designed such that there is no need for a regenerator. A fuel of CV 45000 kJ/kg is used. Determine
the mass flow rate of air through the plant
the rate of fuel consumption.
Assume Cp= 1 y 1.4.
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