Techspace Aero invents tomorrow’s rotor

Research on weight reduction has led Techspace Aero (Safran group) to develop an innovative new rotor for low-pressure compressors, the bladed drum, or BluM®. This lightweight component was developed within the scope of work on new-generation low-pressure compressors (LPC), or boosters, a specialty at Techspace Aero. We asked Eric Marot, Blisk & BluM project manager, to give us the low-down on this low-pressure component.

Techspace Aero is working on a new rotor design for the low-pressure compressor, the Bladed druM. What are its advantages compared to current versions?

All engine-makers are already very familiar with integrally-bladed disks, better known as blisks, in which the blades are generally machined out of the same piece of material as the disk, to form a one-piece rotor stage. The advantage is considerable weight savings. So we simply adapted this technology, generally used in high-pressure compressors, to the low-pressure compressor. The Bladed druM, or BluM, has proven to be a very promising solution.

How would you describe this technique?
In today's jet engines, the low-pressure compressor is based on a cylindrical drum comprising circular channels in which the blades are slotted. With the BluM, we maintain the basic drum concept, simple and inexpensive to manufacture, and then use friction welding to attach the blades. The friction welding process, which is starting to be more widely used in aircraft engines, is both accurate and strong, because it maintains the mechanical properties of titanium. Furthermore, it provides a significant reduction in rotor weight, of about 20%.

What is the current development status of this new rotor?
We first investigated the friction welding technique to make sure that it could be used on our compressor. It took a year to carry out the tests and check our results. That involved welding several hundred samples, and then several dozen blades, to check the accuracy and repeatability of the process. The results were very convincing, so we started construction of a full-scale prototype to check the overall production feasibility. The drum is now ready, and we will shortly start blade welding, with tests on an engine test rig slated for next year. The current development timetable provides for the incorporation of this new compressor rotor design in the new-generation engines that will enter service towards 2020.