Which component ensures uniform delivery of air to the compressor inlet?

The correct choice is the inlet duct, as it plays a crucial role in ensuring that air is delivered uniformly to the compressor inlet of a gas turbine engine. The design and shape of the inlet duct are specifically engineered to manage airflow into the compressor. By optimizing the duct shape and minimizing turbulence, the inlet duct promotes a steady flow of air, which is essential for the efficient operation of the compressor.

Uniform air delivery to the compressor is important because variations in airflow can cause inefficiencies and may lead to aerodynamic issues such as stalls. A well-designed inlet duct helps to smooth out the air entering the compressor, making certain that all compressor blades receive a consistent amount of air ideally suited for compression, which increases overall engine performance.

Other components mentioned, while integral to the gas turbine engine function, do not primarily serve this purpose. For instance, the compressor casing supports the compressor structure but does not directly influence airflow delivery. Compressor blades perform the actual compression of air but rely on the inlet duct's design for effective air management. The exhaust manifold channels exhaust gases away from the engine, serving a different function altogether.