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1. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
UNIT V (RAMJET PROPULSION)
PART A (Short Answer Questions)
1. How can you define a ramjet engine?
Ans. Ramjet engine is mechanically the least complicated air-breathing jet engine for thrust production
for flying vehicles. It does not have any rotating components like compressor and turbine. Necessary
pressure rise takes place solely due to design of supersonic air intake and shock waves.
2. State the operating principle of a ramjet engine.
Ans. The ramjet engine produces power by increasing the momentum of the working fluid by induction of
energy by combustion of fuel, so that the momentum of the exhaust jet exceeds that of the incoming air,
on a continuous basis. In contrast to the other air-breathing engines, the working cycle is accomplished
without additional components of compression and expansion, and also without any need for enclosed
combustion.
3. Draw a neat and labeled diagram of ramjet engine.
Ans.
4. Name the various components of a ramjet engine.
Ans. Diffuser, Burner and Nozzle.
5. Differentiate between ramjet and scramjet engine.
Ans. A ramjet is an air breathing jet engine in which combustion takes place in subsonic airflow.
A scramjet is a variant of a ramjet air breathing jet engine in which combustion takes place in
supersonic airflow.
6. State the advantages and disadvantages of ramjet.
Ans. Advantages: i) Ramjet engine is very simple and does not have any moving part.
ii) Cost is low.

2. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
iii) Less maintenance.
iv) There is no upper limit for flight speed.
v) Light weight compared to turbojet engine.
Disadvantages : i) Since the take off thrust is zero, it is not possible to start a ramjet engine without an
external launching device.
ii) The combustor required flame holder to stabilize the combustion due to high speed
of air.
iii) It has low thermal efficiency.
iv) It is very difficult to design a diffuser which will give good pressure recovery over a
wide range of speeds.
7. Differentiate between subsonic and supersonic inlets.
Ans. Inlets are broadly divided into subsonic and supersonic, depending upon the flight Mach number of
the vehicle. They may be further subdivided into external compression inlets in which the flow
compression takes place in the free stream and internal compression inlets wherein the flow compression
takes place inside of the inlet flow passage.
8. Name the modes of operation of operation of a supersonic inlet.
Ans. Critical, Subcritical and Supercritical modes in which a supersonic inlet works.
9. What do you mean by shock swallowing?
Ans. Shock swallowing is the condition of supersonic inlet in which shock waves moves inside the
diffuser section and thereby high deceleration takes place consequent to high pressure rise.
10. What is the purpose of flame holders in ramjet combustors?
Ans. The purpose of flame holders in ramjet combustors is to stabilize the flame and prevent extinguishing
of the flame inside the combustion chamber for a continuous combustion.
11. What is called a shock wave?
Ans. A shock wave is a special kind of pressure wave with a steep pressure rise. It may also be described
as a compression wave front in a supersonic flow field and the flow across the wave front results in abrupt
change of fluid properties.
12. Differentiate between normal and oblique shock.
Ans. When the shock wave gets positioned at right angle to the flow direction, it is known as a normal
shock wave and when the shock wave gets positioned at an angle to the flow direction other than right
angle, it is known as an oblique shock wave.
13. What is the operating cycle of a ramjet engine?
Ans. The operating cycle of a ramjet engine is similar to turbojet engine except that the complete
compression of the intake air is achieved by the ram effect of the inlet diffuser, thus avoiding the

3. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
mechanical compressor. Since the compressor is eliminated, its prime mover, the turbine is also
eliminated.
14. State the purpose of a diffuser.
Ans. The purpose of a diffuser is to decelerate the flow thereby an increase in pressure due to ram effect.
15. How does the ramjet engine produce power?
Ans. The air is diffused to sufficiently low velocity so that it is possible to add the required heat in the
combustion chamber and thereby produce power by expanding the hot exhaust gases through nozzle for
production of thrust power.
16. Ramjet engine is mechanically the least complicated air-breathing jet engine for thrust production in
flying vehicles. Justify
Ans. Since the rotating components are eliminated in ramjet engines, it consists of only three major
components – Diffuser, Burner and nozzle. Hence, Ramjet engine is mechanically the least complicated
air-breathing jet engine for thrust production in flying vehicles.
17. What does it happen when air is decelerated from high Mach number to a low subsonic Mach number?
Ans. When air is decelerated from high Mach number to a low subsonic Mach number, it causes a
pressure rise ratio of even more than 34.
18. Draw T-s diagram of an ideal ramjet cycle.
Ans.
19. Write the energy balance equation across a ramjet combustor.

4. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
Ans.
20. What do you mean by thrust specific fuel consumption?
Ans.
The specific fuel consumption used in a jet engine is the Thrust Specific Fuel Consumption (TSFC), since
the output of a jet engine is in the form of thrust.
PART B (Long Answer Questions)
1. Describe construction, principle and operation of a ramjet engine with a neat diagram showing various
components.
Ans. Ramjet engines consist of intakes, combustors and nozzles. The entire compression process is
accomplished in the intake of the ramjet. Intakes therefore form a very important component of ramjets.
After the intake, the compressed air goes into the combustor. The combustion products are then expanded
through the nozzle to generate thrust.
Ramjet intakes are usually of the supersonic, variable ramp geometry. The ramp position will be
adjusted depending upon the operating condition. The intake usually employs 2-3 oblique shocks followed
by a normal shock for decelerating the flow. After the normal shock, the flow that is subsonic is further
decelerated using a diffuser.
Unlike other jet engines like turbojets, turbofans etc, there are no rotating components in ramjets. The
temperatures in the combustion chamber are therefore much higher than the conventional jet engines.
Maximum temperatures as high as 3000K are common in ramjets. Ramjet combustors are similar to the
afterburners used in turbojet engines.

5. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
Combustors have flame holders for stabilizing the flame within the combustor. The length of the
combustor depends upon the fuel used, the injector characteristics and the flame holders. Though flame
holders are essential to ensure stable combustion, they also lead to total pressure losses. Designers would
need to optimize the blockage due to flame holders.
A discussion of a ramjet engine can be simplified by assuming that the ramjet is stationary, and that air
approaches the engine at a velocity equal to the vehicle speed. As air enters the inlet, adiabatic
compression causes an increase in temperature and a decrease in velocity. The air is further heated by
combustion of the fuel which also increases the mass flow, typically between 5 and 10%. The high-
temperature compressed gases then are expanded in the nozzle and accelerated to high velocity. The thrust
developed by the engine is the net rate of change of momentum of the gases passing through the engine
and is equal to the mass flow rate of the air plus burned fuel times the jet velocity minus the flow rate of
air times the air velocity. The effective net thrust on the vehicle will be somewhat less than the engine
thrust because of skin friction drag on the air flowing around the ramjet vehicle.

6. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
2. Explain how moving parts are eliminated in a ramjet engine. In what way it is different from a
scramjet engine?

7. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I

8. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
3. A ramjet engine is designed to operate at a Mach number of 2 to 8 km altitude. A divergent conical
inlet diffuser is employed and is designed such that a normal shock is formed at the entrance of the
diffuser and the Mach number at the exit of the diffuser is 0.2. Heat added in the combustion chamber
is such that the total temperature of the gases at inlet to the choked nozzle is 2000 K. Find the area

9. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
ratio required for the diffuser. Also find out the heat to be added in the combustion chamber per kg of
gas flow through the nozzle and the Mach number at the inlet to the nozzle. Assume that the internal
flow id frictionless.
Ans.
4. Briefly explain the working of a pulsejet engine. In what way it is different from a ramjet engine?
Ans.

10. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
5. “The ramjets engines are more suitable for supersonic flight.” Substantiate the statement. Explain why
ramjet engines are not that suitable for hypersonic flights.
Ans.
6. A ramjet is flying at Mach 1.818 at an altitude 16.750 km altitude (Pa = 9.122 kPa, Ta= -56.50
C =
216.5 K., sonic speed, a = 295 m/s). The flow is assumed to enter the intake of the ramjet through a
normal shock standing at the intake face. No pre-entry loss or friction loss inside the engine is
assumed to exist. Combustion delivery temperature is 1280 K and the fuel –air ratio is 1:40. The area
at the intake face is A1= 0.0929 m2
and at the Combustion chamber, A3= 0.1858 m2.
Calculate : (a) Mass flow rate through the engine (b) Throat area in the nozzle, A5
(c) Combustion related pressure drop in the combustion chamber
(d) If the nozzle expands to ambient pressure –find the thrust produced
(e) If the nozzle expands only in a convergent nozzle –find the thrust produced
(f) Calculate the propulsive efficiencies for (d) and (e)
(g) Calculate TSFC in both the cases
(h) Complete and draw the cycles for the cases –(i) with C-D nozzle and
(ii) Convergent nozzle
7. Explain difference between subsonic and supersonic inlets. Also describe modes of operation of
supersonic inlets with neat diagrams.

11. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
Ans.

12. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I

13. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I

14. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I

15. VMKV ENGINEERING COLLEGE
DEPARTMENT OF AERONAUTICAL ENGINEERING
QUESTION BANK – IV SEMESTER – REGULATION 2015
SUBJECT - PROPULSION - I
8. Describe the working of a ramjet engine. Depict various thermodynamic processes occurring on h-s
diagram.
Ans. Refer Q. No. 1 and 2 of Part B.
9. Explain ram effect. Explain how ram effect is achieved in turbojet and ramjet engines.
Ans. Refer Q. No. 1 and 2 of Part B.
10. A 0.5 m diameter ramjet engine having a diverging conical inlet diffuser and a converging exhaust
nozzle is designed to operate at a flight Mach number 1.7 at 8 km altitude. The total temperature of
gases at entrance to the exhaust nozzle is 2000 K. The fuel has a heating value of 45 MJ/Kg. Assuming
that there is no pressure loss, that the air enters the combustion chamber with a Mach number 0.2, that
at the design condition a normal shock forms at the entrance to the diffuser and that the nozzle is
choked, calculate (i) cross-sectional area at the exit of the diffuser (ii) exit area of the nozzle (iii) mass
flow rate of air (iv) fuel air ratio (v) loss in total pressure (vi) effective jet velocity (vii) thrust. Neglect
the variation of γ and Cp.