This set of Rocket Propulsion Multiple Choice Questions & Answers (MCQs) focuses on “Thrust Chambers – Injectors”.
1. The carburetor of an internal combustion engine has a similar function as __________
a) injector
b) thrust chamber
c) nozzle
d) propellant tank
View Answer
Explanation: Injector in rocket engine and carburetor in an internal combustion engine functions in a similar manner. Injector meters, injects and atomizes the liquid propellants into the combustion chamber.
2. The process by which liquids are broken into small droplets is called __________
a) atomization
b) vaporization
c) disintegrator
d) pulverization
View Answer
Explanation: Atomization is the process through which the liquid is broken into tiny droplets. One of the functions of injector is atomization.
3. _________ helps in the distribution of propellant from the injector inlet.
a) Injector hole pattern
b) Turbopump
c) Preburner
d) Gas generator cycle
View Answer
Explanation: By varying the injector hole pattern, it is possible to get different types of propellant distribution from the injector inlet. It is related to feed passages and internal manifolds within the injector.
4. A large complex manifold of an injector allows ________ and ________
a) high flow velocities; good distribution of flow over the chamber cross-section
b) low flow velocities; good distribution of flow over the chamber cross-section
c) high flow velocities; poor distribution of flow over the chamber cross-section
d) low flow velocities; poor distribution of flow over the chamber cross-section
View Answer
Explanation: For larger manifolds, the injector flow will be lesser and the distribution of flow over the chamber cross-section will be uniform. This can be seen by considering two passages of varying cross-sections and constant mass flow rate of propellants through it.
5. A small manifold volume of an injector results in ________ and ________
a) less dribble; heavier injector
b) more dribble; heavier injector
c) less dribble; lighter injector
d) more dribble; lighter injector
View Answer
Explanation: Dribble flow is remaining flow after the valve closes. For a smaller manifold volume of an injector, the amount of dribble flow will be lesser. Since the injector is small, only a small mass of material is used for injector manufacturing and hence it leads to a lighter injector.
6. The flow through injector manifold after the main valves are shut is called as ______
a) dribble flow
b) main flow
c) bleed flow
d) pipe flow
View Answer
Explanation: Dribble or dripping flow is the flow after the main valves are shut. This uneven flow is undesirable and needs to minimize.
7. To make a sharp, abrupt start to fuel injection _________ is used.
a) pop valve
b) check valve
c) safety valve
d) anti-dribble valve
View Answer
Explanation: Pop valve is used for that purpose. It sharply opens to allow full flow. This type of valve opens only when a certain pressure has been attained.
8. Which of the following can cause afterburning?
a) Complete combustion
b) Dribbling flow
c) Sloshing in propellant tank
d) Use of cold gas propellant system
View Answer
Explanation: Dribbling flow can cause afterburning. The dribble flow may lead to an excess in fuel and this might end up in secondary reactions after passing the combustion chamber and result in afterburning.
9. Non-impinging injector is also called as _________ injector.
a) showerhead
b) multiple-hole
c) doublet
d) like-on-like
View Answer
Explanation: A showerhead injector is also called as a non-impinging injector. The propellant usually comes out normal to the face cross-section of the injector.
10. Which of the following injectors requires large chamber volume for good combustion?
a) Sheet injector
b) Showerhead injector
c) Impinging-stream-type injector
d) Multiple-hole injector
View Answer
Explanation: Sheet injector requires large chamber volume for good combustion. It is a spray-type injector that can give cylindrical, conical and many other kinds of spray sheets.
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