Steam and Gas Turbines Multiple Choice Questions on “Flame Temperature and Dissociation”.
1. Flame temperature is the __________ temperature reactants can achieve during combustion.
a) minimum
b) maximum
c) constant
d) none of the mentioned
Answer: b
Clarification: Flame temperature is the maximum temperature reactants can achieve during combustion process.
2. Incomplete combustion results in _________ flame temperature.
a) lower
b) higher
c) medium
d) none of the mentioned
Answer: a
Clarification: Incomplete combustion results in lower flame temperature. When the fuel is incompletely combusted the remains the previous combustion will be there in the combustion chamber and when the next cycle starts previous remains also start combusting and as they are at some high temperatures flame temperature gets reduced.
3. Heat transfer results in _________ flame temperature.
a) medium
b) higher
c) lower
d) none of the mentioned
Answer: c
Clarification: Heat transfer results in lower flame temperature. When heat starts transferring amount of heat present in fluid gets reduced and hence flame temperature also gets reduced.
4. __________ flame temperature is attained during stoichiometric mixture.
a) minimum
b) maximum
c) medium
d) none of the mentioned
Answer:b
Clarification: Perfect stoichiometric mixture results in achieving maximum flame temperature.
5. At the end of the combustion process flame temperature deviation is _________
a) high
b) low
c) medium
d) none of the mentioned
Answer: a
Clarification: At the end of combustion process temperature deviation is high. During the end of combustion all the fuel and oxygen gets completed and hence rate of combustion gets reduced as a result flame temperature is drastically reduced.
6. Dissociation of reactants ________ flame temperature.
a) maximizes
b) minimizes
c) remains constant
d) none of the mentioned
Answer: b
Clarification: Dissociation of reactants decreases the flame temperatures. For reactants to dissociate it requires some heat energy and as a result flame temperature is decreased.
7. During combustion entropy change between initial and final state is ____________
a) zero
b) maximum
c) minimum
d) none of the mentioned
Answer: a
Clarification: During combustion entropy change between initial and final state is zero.
8. When flame temperature _________ combustion rate decreases.
a) not related to each other
b) decreases
c) increases
d) none of the mentioned
Answer: c
Clarification: When flame temperature increases combustion rate decreases. When combustion is going to complete it uses up all the oxygen present in the chamber so that flame temperature is increased.
9. Fuel/air ratio effects flame temperature.
a) True
b) False
Answer: a
Clarification: Fuel to air ratio effects flame temperature.
10. When specific heat increases flame temperature ________
a) decreases
b) increases
c) remains constant
d) none of the mentioned
Answer: b
Clarification: When specific heat increases flame temperature increases.