Professional Engineering

Ratan Tata, chairman of Tata Group, officially declared open the Bladon Jets engineering centre in Coventry recently. At the same time he unveiled a masterclass of manufacturing technology that Bladon Jets engineers have brought together to produce micro gas turbines destined for generating sets and hybrid electric cars and vans.

Tata is one of several organisations giving financial support to Bladon Jets. Jaguar Land Rover, part of Tata Motors, is providing technical support – the microturbine also powers Jaguar’s C-X75 concept car.

“What I have seen here vindicates the faith I had in what seemed like a tremendous idea,” said Ratan Tata. “It is far more sophisticated and impressive than I ever imagined. I think this company has a great future, and I feel very proud to be a small part of it.”

The single-shaft microturbine comprises only 49 parts. It has a four-stage axial compressor and a centrifugal compressor, an annular reverse-flow combustion chamber and a radial inflow turbine. Maximum speed is 100,000rpm.

At this level of technology, support comes in many guises, and several businesses provide Bladon Jets with technical expertise. Rolls-Royce, for example, which has made very small gas turbines too, has been supportive.

One of the most remarkable components that investors and supporters alike could inspect was the engine’s nickel superalloy nozzle guide vane (NGV) assembly, together with the compressor/turbine, both central to the micro gas turbine. 

The highly complex, one-piece NGV is manufactured by Materials Solutions of Worcester, a small company focusing on additive layer manufacturing (ALM). Materials Solutions, founded in 2006, is a specialist in metal powder bed ALM using EOS 200W argon laser machines to produce functional parts – so-called “make to print”. The firm has developed processes to deliver materials with mechanical properties equivalent to those of cast or forged parts.

The Bladon Jets NGV demonstrates the fine art of ALM, namely high-value, thin-wall engineered components that might otherwise be extremely difficult to make or, if they can be made, would require heavy machining.

The size of component that Materials Solutions can comfortably handle is determined by the capacity of its EOS machines. The NGV is just within the limits of the machine, namely 250mm in diameter and 200mm high. It would be very difficult to manufacture this complex part by any other means.

The entire microturbine design is generated in CAD and this forms the basis of several manufacturing processes. In addition to the NGV’s design features, which are transferred to Materials Solutions, the CAD model is a driver for parts inspection on the co-ordinate measuring machine, as well as offering data for A&M EDM of Smethwick. This company makes the tools that generate individual compressor and turbine blades on blisks (disks that contain either compressor or turbine blades). The CAD model is the driver for an electro-discharge machine (EDM).

Materials Solutions can receive CAD data in multiple formats but makes a virtue out of the fact that it is not an engineering design resource and has no interest in the function of the shapes it builds. It does, however, assist customers’ designers with their designs for the manufacturing process. It is rare that a part, as designed for machining, will be optimal for building by the ALM process.

Carl Brancher, chief executive of Materials Solutions, says: “We frequently find break lines between components need to move and possibly we can make complete assemblies, obviating the need for machined faces and fastening systems. We can make castings designs, but with far thinner walls. As such we have two deliverables: manufactured parts and technical capability.