Steam and Gas Turbines Multiple Choice Questions on “Divergence and Position Angles”.
1. Jet engines can be accelerated to supersonic velocities with _______ section.
a) Convergent
b) Divergent
c) Does not depend on shape of the section
d) None of the mentioned
Answer: b
Clarification: When fluid passes through divergent section maximum thrust force is provided so that jet engines can be accelerated to supersonic velocities.
2. Nozzles with high pressure ratios have ______ area divergent sections.
a) variable
b) constant
c) maximum
d) none of the mentioned
Answer: a
Clarification: When nozzles are operated at high pressure ratios it needs variable divergent sections because each pressure ratio requires a special divergent section.
3. In nozzle the gases expand _________
a) Iso-thermally
b) Iso-entropically
c) Adiabatically
d) None of the mentioned
Answer: c
Clarification: No heat loss takes place when gases are expanded in nozzle and hence it is said that gases expand adiabatically in nozzle.
4. Convergent nozzles are used in jet engines upto nozzle pressure ratio of _______
a) 0.8
b) 1.8
c) 2
d) none of the mentioned
Answer: b
Clarification: Convergent nozzles are used until the nozzle pressure ratio is 1.8. If the nozzle pressure ratio goes above 1.8 then convergent nozzle will choke.
5. Convergent divergent nozzles used in rocket engines have _________ area ratio.
a) higher
b) lower
c) optimum
d) none of the mentioned
Answer: a
Clarification: Convergent divergent nozzles used in rocket engines have high pressure ratio.
6. Over expansion occurs when exit area of nozzle is _________ than primary nozzle.
a) equal
b) smaller
c) greater
d) none of the mentioned
Answer: c
Clarification: When exit area of nozzle is greater than primary nozzle then fluid suddenly expands leading to over expansion.
7. When divergent section is added _________
a) exhaust velocity is increased
b) exhaust temperature is increased
c) exhaust pressure is increased
d) none of the mentioned
Answer: a
Clarification: When divergent section is added exhaust velocity is increased.
8. What happens when nozzle doesn’t open after the burner is on?
a) None of the mentioned
b) Thrust force decreases
c) Exit velocity increases
d) Turbine blades get overheat and fails
Answer: d
Clarification: When nozzle doesn’t open, turbine blades get overheated and fails.
9. What happens to mach number when divergence angle is 4 degrees?
a) Mach number drops from 1.10 to 0.45
b) Mach number drops from 2.10 to 1.45
c) Mach number drops from 3.10 to 2.25
d) None of the mentioned
Answer: b
Clarification: It was an experimental value obtained from CFD analysis.
10. What happens to mach number when divergence angle is 7 degrees?
a) Mach number drops from 2.5 to 1.5
b) Mach number drops from 3 to 2
c) Mach number drops from 1.5 to 1
d) None of the mentioned
Answer: a
Clarification: It was an experimental value obtained from CFD analysis.