Name of the College : Noorul Islam College of Engineering
University : Anna University
Degree : B.E
Department : Mechanical Engineering
Subject Code/Name : ME 1203 – Gas Dynamics & Jet Propulsion
Document Type : Question Bank
Website : niceindia.com
Download Model/Sample Question Paper :https://www.pdfquestion.in/uploads/niceindia.com/3021-ME_1203_GAS_DYNAMICS_AND_JET_PROPULSION.pdf
NICE Gas Dynamics & Jet Propulsion Question Paper
1. What is the basic difference between compressible and incompressible fluid flow? :
Compressible :
1. Fluid velocities are appreciable compared with the velocity of sound
2. Density is not constant
3. Compressibility factor is greater than one.
Related : Noorul Islam College of Engineering ME1305 Applied Hydrolics & Pneumatics B.E Question Bank : www.pdfquestion.in/3020.html
Incompressible :
1. Fluid velocities are small compared with the velocity of sound
2. Density is constant
3. Compressibility factor is one.
2. Explain the meaning of stagnation state with example :
The state of a fluid attained by isentropically decelerating it to zero velocity at zero elevation is referred as stagnation state.
(e.g.) Fluid in a reservoir (or) in a settling chamber :
3. Distinguish between static and stagnation pressures :
In stagnation pressure state, the velocity of the flowing fluid is zero whereas in the static pressure state, the fluid velocity is not equal to zero.
4. Differentiate between the static and stagnation temperatures :
The actual temperature of the fluid in a particular state is known as “static temperature” whereas the temperature of the fluid when the fluid velocity is zero at zero elevation is known as “stagnation temperature”.
5. What is the use of mach number? :
Mach number is defined as the ratio between the local fluid velocity to the velocity of sound.
6. Name the four reference velocities that are used in expressing the fluid velocities in non-dimensional form? :
i. Local velocity of sound a = gRT
ii. Stagnation velocity of sound
iii. Maximum velocity of sound
iv. Critical velocity of sound / fluid
7. What are the different regions of compressible flow :
The adiabatic energy equation for a perfect gas is derived in terms of fluid velocity © and sound velocity (a). This is then plotted graphically on the c- a co-ordinates, a steady flow ellipse is obtained.
The various regions of flow are :
(i) Incompressible region (M » 0)
(ii) Subsonic region (M < 1)
(iii) Transonic region
(iv) Supersonic region (M > 1 and M < 5)
(v) Hypersonic region
8. Define mach angle and mach wedge :
Mach angle is formed, when an object is moving with supersonic speed. The wave propagation and changes are s mooth. When an object is moving with hypersonic speed the changes are abrupt is shown in Fig. Hence for a supersonic flow over two – dimensional object “mach wedge” is used instead of “mach cone”.
9. What is meant by isentropic flow with variable area? :
A steady one dimensional isentropic flow in a variable area passages is called “variable area flow”. The heat transfer is negligible and there are no other irreversibilities due to fluid friction, etc.
10. Sketch the isentropic and adiabatic expansion process in P-V and T-S diagram} :
11. Represent the adiabatic flow through a diffuser on T-S diagram. Label the different states, the initial and final points :
12. Air from a reservoir is discharged through a nozzle. Show the variation of pressure along the axis of the nozzle :
13. What is impulse function and give its uses? :
Impulse function is defined as the sum of pressure force and intertia force. Impulse function F = Pressure force rA + intertia force rAc2
Since the unit of both the quantities are same as unit of force, it is very convenient for solving jet propulsion problems. The thrust exerted by the flowing fluid between two sections can be obtained by using change in impulse function.
14. What is chocked flow? : State the necessary conditions for this flow to occur in a nozzle:
When the back pressure is reduced in a nozzle, the mass flow rate will increase. The maximum mass flow conditions are reached when the back pressure is equal to the critical pressure. When the back pressure is reduced further, the mass flow rate will not change and is constant. The condition of flow is called “chocked flow”.
15. Shock waves cannot develop in subsonic flow? : State the reason:
Shocks are introduced to increase the pressure and hence it is a deceleration process. Therefore, shocks are possible only when the fluid velocity is maximum. In a subsonic flow, the velocity of fluid is less then the critical velocity and hence deceleration is not possible. Thus, shock waves cannot develop in subsonic flow.