What design feature allows for convenient ducting directly to the impeller inducer vanes?

The design feature that allows for convenient ducting directly to the impeller inducer vanes is the single-entry impeller. In a single-entry impeller system, the flow of air enters from one direction and is directed straight into the inducer vanes, facilitating a more streamlined pathway for the airflow. This design simplifies ducting arrangements and optimizes airflow into the impeller, which is crucial for increasing efficiency in gas turbine engines. The direct approach enhances the performance of the engine by enabling smoother and more consistent airflow, reducing turbulence and pressure drops.

In contrast, options like double-entry impeller or twin-scroll impeller involve more complex branching paths or synchronized flow entries that do not provide the same straightforward ducting arrangement. A dual-port impeller similarly complicates the flow entry, focusing on dividing the intake into two separate paths rather than allowing one efficient pathway to the inducer vanes. Thus, the single-entry impeller uniquely stands out for its ability to facilitate direct airflow to the impeller inducer vanes.