rr322103 aerospace propulsion ii

Code No: RR322103 Set No. 1

III B.Tech II Semester Supplementary Examinations, Aug/Sep 2006AEROSPACE PROPULSION-II

(Aeronautical Engineering)Time: 3 hours Max Marks: 80

Answer any FIVE QuestionsAll Questions carry equal marks

1. What do you understand by free vortex turbine stage design?Derive the following relationship

Cw.r = constant [16]

2. (a) Explain the following with respect to an axial turbine blade design:

i. Secondary loss parameter

ii. Correction factor for trailing edge thickness.

(b) Write a note on forced convection air cooling of axial turbines. [5+5+6]

3. What are the various assumptions made while analyzing an ideal ramjet engine?Explain the conditions occurring at the exit of diffuser section and combustionchamber. [16]

4. A preliminary performance analysis is to be made of a two dimensional ramjetengine which is to be installed in the wing of a supersonic airplane. The engineis operating at sub-critical Mach number M0 = 2.5 at 50000 ft altitude and themaximum total temperature due to combustion is 40000R. The ramjet engine is tobe equipped with a diverging diffuser. Calculate

(a) M2,

(b) P2/P0,

(c) P6/P0,

(d) The gross thrust coefficient CFg,

(e) the weight ratio of air flow into the engine and

(f) the TSFC.

Assume that the Mach number M2 at the entrance to the constant area combustionchamber is 0.2, k=1.4=constant, the lower heating value of the fuel is 19300 Btu/lb,A1 = 10ft

2 and the flow is frictionless and neglect the effect of the fuel flow on thethrust. [16]

5. Explain the various performance parameters affecting the selection of a rocket mo-tor. [16]

6. Classify the composition of solid propellants with examples. Explain the proce-dure for preparation of solid propellants and precautions to be taken during thepreparation. [16]

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7. (a) Explain the desirable characteristics of a typical rocket thrust chamber.

(b) Write down the relative merits and demerits of liquid propellants over solidpropellants. [8+8]

8. What do you understand by electromagnetic thrusters? Explain the working prin-ciple and various types with the help of suitable diagrams. [16]

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1. Explain the significance of flow coefficient and blade loading coefficient with thehelp of - diagram for 50% reaction turbine stage. [16]

2. Following data refers to a single stage turbine:

Mass flow, m = 20 kg/s

Isentropic efficiency t = 0.89

Inlet temperature T01 = 1100 K

Temperature drop (T01- T03) = 145 K

Inlet pressure p01 = 4 bar

Flow coefficient = 0.8

Swirl angle 3 = 10 degrees

Nozzle eux angle 2 = 58023

Mean blade speed = 340 m/s

Rotational speed N = 250 rev/s

Draw velocity diagram and calculate blade height and tip/root radius ratio atstations 1, 2 and 3.

Where 1 is nozzle inlet, 2 is nozzle exit and 3 is rotor exit. [16]

3. (a) Derive the relationship for overall efficiency of an ideal ramjet engine.

(b) How actual ramjet engine cycle deviates from an ideal ramjet engine cycle?Explain. [7+9]

4. Explain the preliminary concepts in supersonic combustion. [16]

5. (a) In a given rocket engine, a mass flow of propellant equal to 87.6 lbm/sec ispumped into the combustion chamber, where the temperature after combus-tion is 60000R. The combustion products have mixture value of R = 2400ft.lb/(slug).0R and = 1.21. If the throat area is 0.5 ft2, calculate the pres-sure in the combustion chamber.

(b) A rocket using hydrogen-oxygen as the fuel oxidizer combination has a specificimpulse of 360 sec. Calculate the ratio of propellant mass to initial massrequired to achieve a burnout velocity equal to escape velocity from the earth.

[8+8]

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6. What do you understand by thrust vector control? Explain briefly the variousmethods to control the thrust vector of a solid rocket motor. [16]

7. Explain the salient features of a liquid propellant rocket motor with turbo-pumpfeed system with the help of a schematic diagram. Write down its advantages anddisadvantages. [16]

8. Determine the flight characteristics of an electrical propulsion rocket with:Is = 2000 secF = 0.5 lbDuration = 4 weeks = 2.42 x 106 secPayload weight = 20000 lbPower plant weight ratio = 0.1 kW/lb. [16]

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1. Explain the elementary theory of axial flow turbine with the help of velocity dia-grams. [16]

2. Plot the velocity diagrams for the tip and hub for a free vortex turbine design andalso show the nozzle and turbine angles for the blading at three sections for thefollowing given data:

Aircraft speed = 960 km/hr

Air flow = 6 kg/s

Altitude = 6000m

Compressor efficiency = 0.83

Turbine efficiency = 0.85

Turbine inlet temperature = 10000C

Ram efficiency = 100%

Assume reasonable hub-tip ratio, a maximum outer diameter of 375mm and amaximum rotor tip speed of 360m/s. Velocity diagrams are required for only thepitch line energy condition in the turbine. It is suggested that flow in the turbinebe subsonic throughout. [16]

3. Define and derive the relationship for gross thrust coefficient of a ramjet engine.Explain the behavioural characteristics of gross thrust coefficient with the relatedparameters with the help of plots for a fixed geometry ramjet engine. [16]

4. A preliminary performance analysis is to be made of a two dimensional ramjetengine which is to be installed in the wing of a supersonic airplane. The operatingsupercritical flight Mach number is M0 = 3.3 at 50000 ft altitude and the maximumtotal temperature due to combustion is 40000R. The ramjet engine is to be equippedwith a two dimensional oblique shock diffuser which has a wedge angle of 300 anda lip angle of 650. Assume that weight rate of air flow is 348 lb/sec. Calculate

(a) M2,

(b) P2/P0,

(c) P6/P0,

(d) The gross thrust coefficient CFg and

(e) the TSFC.

1 of 2


Assume that the Mach number M2 at the entrance to the constant area combustionchamber is 0.2, k=1.4=constant, the lower heating value of the fuel is 19300 Btu/lb,A1 = 10ft


5. (a) Consider a rocket with kerosene-oxygen as the fuel oxidizer combination. Theratio of initial weight before blast-off to the final weight at burnout is 5.5.Calculate the burnout velocity.

(b) The mass flow through a rocket engine is 25 kg/sec. If the exit area, velocityand pressure are 2m2, 4000 m/s and 2 x 104 N/m2 respectively, calculate thethrust at a standard altitude of 50 km. [8+8]

6. Explain the following with respect to solid rocket motor:

(a) Erosive burning

(b) Thrust termination

(c) Chuffing

(d) Hazard properties of solid propellants. [4x4=16]

7. What are the various types of propellant tanks in case of liquid rocket motors? Ex-plain the role, desirable characteristics, advantages and disadvantages of propellanttanks. [16]

8. (a) List down various losses affecting the electric thruster efficiency.

(b) How will you select a particular electrical propulsion system for various spaceflight applications/ mission? [6+10]

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1. What factors affect the choice of blade profile, pitch and chord of turbine blades?Explain. [16]

2. Plot the velocity diagrams for the tip and hub for a free vortex turbine design andalso show the nozzle and turbine angles for the blading at three sections for thefollowing given data:

Aircraft speed = 960 km/hr

Air flow = 6 kg/s

Altitude = 6000m

Compressor efficiency = 0.83

Turbine efficiency = 0.85

Turbine inlet temperature = 10000C

Ram efficiency = 100%

Assume reasonable hub-tip ratio, a maximum outer diameter of 375mm and amaximum rotor tip speed of 360m/s. Velocity diagrams are required for only thepitch line energy condition in the turbine. It is suggested that flow in the turbinebe subsonic throughout. [16]

3. What are the various assumptions made while analyzing an ideal ramjet engine?Explain the conditions occurring at the exit of diffuser section and combustionchamber. [16]

4. A preliminary performance analysis is to be made of a two dimensional ramjetengine which is to be installed in the wing of a supersonic airplane. The design flightMach number is M0 = 3.0 at 50000 ft altitude and the maximum total temperaturedue to combustion is 40000R. The ramjet engine is to be equipped with a divergingdiffuser. Calculate

(a) the area ratio of the diffuser A2/A1,

(b) the area ratio for converging exhaust nozzle A6/A7,

(c) the weight ratio of air flow into the engine,

(d) the pressure ratio P6/P0,

(e) The gross thrust coefficient CFg and

(f) the TSFC.

1 of 2


Assume that the Mach number M2 at the entrance to the constant area combustionchamber is 0.2, k=1.4=constant, the lower heating value of the fuel is 19300 Btu/lb,A1= 10ft


5. (a) Derive the equation relating mass ratio and propellant mass fraction.

(b) Explain the following with respect to rocket motor:

i. Internal efficiency

ii. Combustion efficiency

iii. Propulsive efficiency

iv. Overall efficiency. [4x4=16]

6. (a) Write notes on the following with respect to solid rocket motor:

i. Pyrotechnic Igniters

ii. Mechanical deflection method for thrust vector control

(b) How thrust termination is accomplished in solid rocket motor?. [5+5+6]

7. (a) Explain the salient features of a hybrid rocket with the help of a sketch.

(b) How exhaust properties of a liquid rocket motor affect the communicationsystem? [8+8]

8. Explain the working principle of an electrical rocket with the help of a schematicdiagram. Write down the merits and demerits of an electric rocket motor over asolid propellant rocket motor. [16]

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rr322103 aerospace propulsion ii

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