If you are familiar with the Boeing 777-300ER, you will notice that its jet engine is huge, the GE90-115B. In fact, its diameter is as big as the cabin of a Boeing 737! The Boeing 747’s engines were not this large. You will also notice that the jet engines of the A321neo, the PW1100G and the CFM LEAP, are bigger than the previous CFM56 and IAE V2500 found on the older variants of the plane. These engines are large that they are closer to the ground.
If these engines are getting larger and more powerful, how are they able to become more efficient? So at this point, you might be wondering why jet engines are getting bigger and bigger as they evolve?
When you look at commercial jets, you’ll notice the engines are called turbofans. But before we dive into why these engines are getting bigger, let’s get a quick rundown of what a turbofan engine is.
What is a Turbofan Engine?
A turbofan, or fanjet, is the go-to engine for most airplanes these days. The name “turbofan” is a blend of turbojet, its older relative, and the added fan stage. So, you’ve got a gas turbine engine that burns fuel to create mechanical energy. This energy then powers a ducted fan that pushes air out the back of the engine.
Unlike a turbojet, where all the air goes through the combustion chamber and turbines, a turbofan lets some air bypass these parts. So, think of a turbofan as a turbojet that’s also powering a ducted fan. Both are working together to push the plane forward.
Increasing Bypass Ratio
Nowadays, aircraft makers are focusing on upping the bypass ratio in their engines. The bypass ratio is basically how much air goes around the engine’s core compared to the air that goes through it. Bigger engines with larger fan blades and higher bypass ratios are the trend, but they try to keep the engine’s core size pretty much the same. This setup lets more air flow through the big fan blades without needing to burn extra fuel. That means you’re saving on fuel.
For example, the Rolls Royce XWB engines have a bypass ratio of 9.6:1, and the GE9X for the Boeing 777X is at 9.9:1. In simpler terms, for the GE9x, 9.9 kg of air goes around the core for every 1 kg of air that goes through it. The Pratt & Whitney PW1100G engine on the A320neo family has an even higher bypass ratio of 12.5:1.
Challenges of Increasing the Engine Size
Making engines bigger isn’t a walk in the park. One big hurdle is finding materials that can handle faster rotation and bigger forces. Engineers have come up with super-strong titanium alloys and composite materials that can take the heat. Inside the engine, they use some pretty advanced reduction gears to make sure the fan blades don’t spin too fast, especially when the engine is cranked up.
So, there you have it. Turbofan engines are getting bigger for a reason, and it’s all about making flights more fuel-efficient while keeping things safe and sound.
First love never dies. I fell in love with airplanes and aviation when I was a kid. My dream was to become a pilot, but destiny led me to another path: to be an aviation digital media content creator and a small business owner. My passion for aviation inspires me to bring you quality content through my website and social accounts. Aviation is indeed in my blood and blog!
