Overview
The air inlet section supplies airflow to the engine free of ice and unwanted objects. The primary function of the air inlet section is to move the air into the fan and compressor section for engine operation. The air inlet section also moves the airflow to the compressor section and supplies the engine attachment point for the airframe.
The air goes from the nacelle inlet through the air inlet section to the engine. The flow pattern of the air inlet section decreases the unwanted objects and weather elements to go into the compressor section. A high by-pass pressure ratio (4.2:1) gives a high engine thrust with decreased drag, and prevents icing conditions. The air inlet section attaches to the compressor section and the by-pass duct. The structural component of the air inlet section divides the fan airflow and sends it to the compressor and the bypass ducts.
The air inlet section measures the inlet total air temperature, an important parameter for engine performance.
The engine inlet has the following primary functions:
- Makes a large part of the engine thrust
- Moves the airflow to the engine compressor section
- Supplies an engine attachment for the engine
01/04/16
Fan Inlet Housing Assembly
The fan inlet housing assembly attaches the nacelle inlet. The housing is attached to the forward flange of the front frame which connects with the compressor section and the outer fan duct.
The fan inlet housing assembly has the following components:
Fan Rotor Assembly
The fan rotor assembly attaches to the fan stub shaft, which aligns the fan rotor in the fan inlet housing. The fan stub shaft attaches to the low-pressure (LP) turbine shaft and connects directly to the LP turbine rotor. It attaches to the spinner assembly.
The fan rotor has 22 low-aspect-ratio, wide chord, titanium blades engaged in a titanium disk. If a dangerous load occurs, a frangible support controls the fan movement in radial and axial directions.
The high-pressure at the fan hub decreases the inlet distortion transmitted to the compressor, which increases the stable compression system performance. The high hub-pressure ratio helps the compressor obtain better performance and higher cabin bleed pressures. This also causes temperature increase which prevents icing in bad weather conditions.
Fan Inlet Housing
The fan inlet housing aligns the nacelle inlet with the fan stator and attaches the electronic control unit (ECU) and T2 sensor. The fan inlet housing is an aluminum ring that attaches to the forward flange of the front frame. The fan inlet housing is made of aluminum honeycomb aramid (Kevlar) fiber material wound with a Teflon sleeve that would contain the blade during a failure. It has a thick abradable layer on the inner surface to let the frangible support move if necessary. The composite strength of the fan inlet housing is sufficient to contain the damage from the compressor rotor blades or damage from abradable rotor tips.
Fan Stator Assembly
The fan stator assembly has 53 vanes installed in the hub with grommets. The grommets prevent vibration from airflow. The stator vanes remove the rough flow from the air and control the airflow directly to the bypass duct and the compressor.
Front Frame
The front frame assembly is the primary structural component of the engine. The front frame divides the fan airflow into 80% through the bypass duct and 20% through the compressor. The front frame assembly forward flange attaches and aligns the fan containment housing assembly. The front frame assembly aft flange attaches and aligns the compressor case with the forward fixed bypass duct. The one-piece front frame assembly has eight struts in the core section and the fan bypass areas. The design of the front frame makes a flow path inlet which decreases possible foreign object damage (FOD) to the engine assembly. The inner section has attachment points for the inner hub of the stator assembly and No. 1, 2 and 3 bearing housing assembly. The front frame has attachment points for the accessory gearbox, forward engine mount, waterwash manifold and sensors.
