Blade runner

A laser sensor for more efficient turbine blade construction could help the aerospace industry develop low-weight jet engines with non-metallic parts.

Developed by Technical University of Dresden (TU Dresden) and the German Aerospace Centre (DLR), the system measures the clearance between the tips of the turbine blade and the casing, and the vibrations caused by the blades breaking the sound barrier as they rotate.

Tip clearance is a particularly important parameter in turbine design, because it has a very strong influence on efficiency. The lower the clearance — that is, the smaller the distance between the tip of the blade and the case — the more efficient the turbine.

But because of the expansion of the materials as they heat up, and the mechanical movement of the blades as they spin, the clearance varies constantly by a matter of micrometres.

Traditionally, tip clearance is measured using electrical sensors on the turbine casing to monitor the change in capacitance as the size of the gap between the two metal bodies fluctuates. However, this form of measurement can be imprecise; moreover, it only works with metal.