What are the two basic types of all inlet ducts?

The two basic types of all inlet ducts are indeed classified as single entrance and divided entrance. Single entrance ducts allow air to enter the engine from one distinct point, providing a straightforward pathway for airflow into the compressor. This design is typically simpler and can be lighter since it requires fewer components.

Divided entrance ducts, on the other hand, facilitate air intake from two separate sections. This configuration can improve airflow characteristics for certain engine designs by allowing for a more uniform distribution of air to the compressor, which can enhance performance and efficiency, particularly in high-speed or high-thrust applications.

Understanding these two duct types is crucial for anyone studying gas turbine engines, as the design and type of inlet duct significantly influence engine efficiency, performance, and overall aerodynamic characteristics. This foundational knowledge is paramount when analyzing how different engine configurations perform under various operational conditions.