GEnx engine: Big, successful, and on a growth trajectory

The GEnx fan measures nearly three meters in diameter. You can tell just from its dimensions that this engine is built for big challenges. GE Aerospace developed the GEnx as the successor to the successful CF6. It is based on the proven architecture of the GE90. Two versions were created: The GEnx-1B powers the Boeing 787 Dreamliner, while the GEnx-2B was developed for the Boeing 747-8, the final version of the legendary “Queen of the Skies.”

On October 26, 2011, the GEnx entered commercial service for the first time; 15 years later, more than 2,800 GEnx engines are in service. While production of the Boeing 747-8 has now ended, manufacturing of the Dreamliner and its GEnx-1B engines is in full swing. Boeing delivers about eight aircraft to customers each month, and the company forecasts that this figure will nearly double over the next five years.

“The GEnx is one of our most important programs with GE Aerospace. Over the next 30 years, it will replace the CF6 engine as the ‘workhorse’ of widebody aircraft,” says Josef Moosheimer, head of GEnx program management at MTU Aero Engines. “The engine is very popular with airlines and operates reliably.” MTU’s program share is 6.65 percent. A key component in this engine is the turbine center frame (TCF).

What the turbine center frame does in the engine

The turbine center frames serve as a duct for the hot gas flowing from the high-pressure turbine into the low-pressure turbine, and it fulfills a variety of functions. It routes the flow of hot gases exiting the high-pressure turbine at temperatures exceeding 1,000 degrees Celsius to the low-pressure turbine while keeping aerodynamic losses to a minimum. Both turbines need to be provided with cooling air, which is supplied through the turbine center frame. As the supporting structure, the TCF houses the rear bearing of the high-pressure spool, thus playing a crucial role in maintaining the clearances in the high-pressure turbine. At the same time, it is essential to ensure seamless oil delivery and scavenging through the hot structure. Moreover, the TCF must be capable of withstanding extreme loads that could act on it—in the event of a fan blade out, for example.

This means that during operation, the TCF is exposed to high temperatures and significant mechanical stress. Given its wide range of functions, the TCF must also meet exacting requirements on manufacturing precision and circumferential symmetry.

MTU brings global expertise to the GEnx engine

Every finished GEnx turbine center frame is the product of collaborative effort across several MTU locations. Program management and manufacturing of the TCF’s flow path hardware (FPH) are based in Munich; this manufacturing process is currently being fully automated. The technology featured in this project is also expected to be used in the future for components of the GE9X, the engine for the Boeing 777X.

The hub strut case, in turn, is manufactured at MTU Aero Engines Polska, and all TCF modules are assembled there before being delivered to GE’s assembly line.

As the GEnx fleet ages and is used more, another aspect of the engine’s lifecycle is becoming increasingly important: maintenance. MTU Maintenance Hannover has now handled its 2,000th GEnx turbine center frame. MTU’s role in the GEnx program is also growing in the U.S. MTU Maintenance Fort Worth is scheduled to begin offering complete engine overhauls by the end of the decade; the Fort Worth site will be supported by MTU Maintenance Hannover for module repairs.

“The program has a very promising future ahead of it. MTU Maintenance Hannover recently introduced a repair solution that greatly reduces turnaround time and optimizes costs for customers,” says Yannic Düring, Senior Manager Customer Accounts at MTU for the GEnx/GE9X program.