Question 61 AEL01 - Assistant Engineer - Limited

The Correct Answer is C ### Why Option C ("provide a wide range of combustion") is correct: The primary function of utilizing a **variable capacity, pressure atomizing** system in a fuel oil burner is to allow the boiler or furnace to operate efficiently and stably across a significant range of heat output (load). * **Pressure Atomizing:** This mechanism creates a fine spray (atomization) necessary for efficient combustion. * **Variable Capacity:** This critical feature means the burner can adjust the amount of fuel being sprayed and burned. Unlike fixed-capacity burners that operate only at high or low fire, variable capacity burners can modulate smoothly across their entire operating range (e.g., from 20% to 100% of maximum output). * **Wide Range of Combustion:** By varying the amount of fuel delivered while maintaining efficient atomization (often by managing pressure and utilizing internal mechanical components like flow dividers or spillback lines), the burner can accurately match the heat output to the demand, thereby providing a wide range of combustion. ### Why the other options are incorrect: **A) maintain a constant fuel temperature** Maintaining a constant fuel temperature is the function of ancillary equipment like fuel oil heaters or preheaters, which condition the fuel for proper viscosity before it reaches the burner gun. While crucial for atomization, it is not the function of the capacity-varying mechanism of the burner itself. **B) provide a constant fuel return pressure** While systems like the "return flow" or "spillback" pressure atomizing types *do* involve managing return pressure, the purpose of controlling this pressure is to regulate the flow to the nozzle (thus varying the capacity), not simply to maintain the return pressure as an end goal. The ultimate function is load matching (i.e., varying the combustion range). **D) maintain smokeless fuel oil atomization** Smokeless atomization is the goal of *all* properly functioning pressure atomizing burners (whether fixed or variable capacity). While a variable capacity burner must achieve this across its range, the *defining function* of the **variable capacity** feature is the wide range of output, not merely the quality of the atomization (which is the role of the atomizer tip and fuel pressure).