Modern aircraft engines drive the development of newer, more efficient airframes. An advanced airframe design may improve the overall efficiency by 5-10%; a more efficient engine can improve things by 10-20%. Modern turbofan engines are powerful, efficient, and gigantic.

The most noticeable component of a turbofan is the large fan at the front of the engine. A large fan at the inlet makes the engine a high bypass ratio engine. The bypass ratio is the ratio of the mass flow rate of the air bypassing the engine’s core to the mass flow rate of the air entering the engine’s core.

Turbofan engines

In a turbofan engine, the outside air is sucked into the engine through the rotating fan. The air passes through a series of compressor stages where the air is squeezed. The compressed air is mixed with pressurized fuel and ignited in the combustion chamber. Hot gases expand and exit through the engine exhaust, creating thrust.

The fan

On modern airliners, the engines perform the most critical job behind closed doors (cowlings). The fast-rotating fan is the only component visible on the engine. Modern turbofan engines cover a much larger flight envelope than the aircraft they are fitted on. This is because the fan experiences a full supersonic flow during the flight.

A G650 engine powered by Rolls-Royce
Photo: Rolls-Royce

The engine fan is one of the significant components of the engine. The beauty of a fan lies in its sinuous curves, forward sweep, hooked top, and belly in the center. It is the first major component that is exposed to the outside environment. From high-speed air and rain to hail and (sometimes) live birds, fan blades take it all.

General Electric engines

Large engine manufacturers have individually mastered the art of modern fans using a variety of composites and alloys. General Electric (GE) is a world leader in Carbon Fiber Reinforced Plastic (CFRP) fans. On GE90 and GEnx engines, numerous CFRP pre-preg cloths are laid by hand, which form the foundation of fan blades. Speaking about the most powerful (active) engine to date, the GE90, Nick Kray of GE mentioned,

“Our competitors make jet engine fans from titanium and steel and even some of our own people weren’t initially so hot about using composites,” - Nick Kray, GE Aviation.

The GENx engines are also based on CRFP composites. GE has recently produced the fourth generation of the blade for the GE9X, GE’s largest engine yet. The GE9X fan blades are manufactured with stiffer carbon fibers for improved impact resistance. A unique form of glass fiber composite is used on the trailing edge to deflect impact stress from the blade.

The leading edge is manufactured with steel instead of titanium on the GE90 and GENx for a thinner, stronger, and more efficient design. The fan blades can be thinner, lighter, and fewer with efficient materials. As a comparison, the GE90 comprises 22 blades, the GEnx holds 18, and the largest of the three, the GE9X, has only 16 blades.

CFM International engines

The blades on the CFM International LEAP engines take the CFRP technology even further. With the joint venture between GE and Safran Aircraft Engines, LEAP engine blades are manufactured using woven fibers. Specialized heat-treated carbon fibers are woven into a three-dimensional mesh before being soaked in infused resin.

The interlocking design prevents delamination that discrete CFRP layers can otherwise cause. The design also allows precise control of the blades’ directional, stiffness, and aerodynamic properties. A controlled CFRP design allows manufacturers to create various aerodynamic forms on the blade. These forms are necessary to achieve varying speeds (supersonic, transonic, and subsonic) on blades.

What are your thoughts on the aerodynamic capabilities of the modern aircraft engine fan? Tell us in the comments section.