Gas Turbine Design

During testing of a gas turbine rig a problem was discovered with some transfer tubes. These tubes convey services like oil and instrumentation across the gas flow path. Wakes were found to be generated by the tubes, causing interference with acoustic measurements and consequent risk of fatigue failure. The challenge to Assystem was to deliver components that would fix the problem in a two-week window between rig builds. Assystem had to develop a cost effective concept, make and fit the solution without change to existing components or disassembling the rig, whilst ensuring the components were strong enough to withstand the rigours of a gas turbine environment.

The Assystem solution combined a 'standard engineering fix' with the latest manufacturing processes. Tall chimneys suffer from similar vibration problems. In high winds vortices shed from a chimney can cause it to oscillate and eventually fail. To avoid this a spiral wrap is used that changes the behaviour of the airflow. Assystem employed this technique combined with the use of Selective Laser Sintering to manufacture a set of vortex disrupting components. Each transfer tube was clad in a SLS jacket with a spiral strake running round it.

In SLS the design model is sliced into a series of layers 0.002 inch thick. A bed of powder is laid down and the laser traces out the first model layer solidifying the desired shape. An additional layer of powder is then spread over the first and the next model layer selected and melted, successive layers being built up until the component is formed.

The components were designed, made and delivered to the customer in under a week!