🔍 Key Concepts

• Boiler combustion process and the role of air in complete vs. incomplete combustion • Effects of too little air on flame stability and furnace conditions • Relationship between combustion quality and stack temperature and superheater temperature

💭 Think About

• Think about what happens to the flame if there is not enough air to burn the fuel properly. Does the fire become hotter and cleaner, or unstable and irregular? • Which of the listed options sounds like a symptom of poor, unstable combustion right in the furnace rather than a downstream temperature effect? • Consider which answer is most directly related to the behavior of the flame itself, not just temperatures in other parts of the system.

✅ Before You Answer

• Identify which options refer to temperature effects (superheater or stack) and which refer to flame behavior in the furnace • Recall that insufficient air usually causes incomplete combustion, smoke, and unstable burning rather than clean, steady high-temperature operation • Before choosing, ask: "Which choice best describes an irregular, weak, or unstable flame in the furnace?"