🔍 Key Concepts

• Turndown ratio (firing range) definition for burners and why it matters in boiler operation • Basic operation principles of steam assist, rotary cup, return flow (spill return), and straight-through atomizers • How fuel and atomizing medium flow can be varied in each type to maintain proper atomization at different firing rates

💭 Think About

• For each atomizer type, ask yourself: over a wide range of boiler loads, which design can keep fuel properly atomized without flame instability? • Which atomizer type allows the easiest and widest adjustment of fuel flow while still maintaining good spray quality? • Which designs are more limited to a narrower, more stable operating band because of how they introduce and mix fuel and atomizing medium?

✅ Before You Answer

• Be clear on what turndown ratio means: highest stable firing rate divided by lowest stable firing rate. • For each option, think about whether fuel flow and/or atomizing medium flow can be modulated independently. • Recall which atomizer type is typically used when a boiler must operate efficiently over a very wide load range (from low to high firing).