Research

In good hands

Gas-fired power stations are flexible and eco-friendly, especially when they can be operated at very high emperatures. That is why physicist Werner Stamm has been working on particularly temperature-resistant materials for turbines for more than a quarter of a century.

The hotter the gas, the more effective the combustion

Looking at the hands of Werner Stamm would lead one tobelieve that the physicist must have a life beyond the worldof superconductivity and high-temperature-resistant alloys.They look big and capable. And in actual fact, Stamm, the sonof a metalworker, initially completed a precision engineeringapprenticeship after leaving school. ‘Stammi’, as he is affectionatelycalled by his handball teammates, was destinedto take on his father’s business one day. But things turned outdifferently: his father had to close the metalworking shop,so his son and chosen successor gained the relevant entrancequalifications and studied physics in Duisburg.

Werner Stamm inspects a gas turbine he helped to develop at the Mainz-Wiesbaden power station.

Stamm was already specialising in extreme temperatures duringhis final year project at university. He investigated the magneticbehaviour of alloys whose linear expansion remains unchangedwith temperature fluctuations. They were also the subject ofhis doctoral studies, which he completed in 1988 in a specialresearch field. It was at this very time, when Stamm was alsoinvestigating the phenomena of superconductivity at temperaturesapproaching minus 270 degrees Celsius, that he firstestablished professional contact with Siemens. When he eventuallystarted working at the Mülheim development centre of theelectrical company in 1991, the temperature level also suddenlybegan to rise: his job was to develop and classify materials for gasturbines. At the time, the turbine blades directly behind the combustionchamber had to withstand temperatures of around 930degrees Celsius.

Yet it was already clear that there would be a trend towardsever higher temperatures. ‘That is the crucial factor for improvingthe efficiency of a gas turbine,’ explains Stamm. Today’sturbines reach hot gas temperatures of up to around 1,500degrees Celsius. This rise in temperature would be very difficultor even impossible to achieve with a homogeneous material,at least when other factors such as lifetime and cost haveto be taken into consideration. Accordingly, Stamm optedfor layers of insulation applied to the base material of theturbine blades. ‘It wasn’t my idea; people had been researchingit for 50 years,’ says Stamm. Nonetheless, he developed acoating technique for series production, which is multi-patented:it involves the base material being coated with two very thinlayers. The outer layer is made of a high-temperature-resistantceramic material based on gadolinium zirconate. A bondinglayer underneath it ensures that it adheres to the base material.It is this layer that makes it possible to achieve a lifetimeof 25,000 operating hours, as specified by customers.Stamm spent a long time working on the ideal material mix,ultimately discovering that the lifetime of the bonding layercould be significantly improved by adding up to two per cent rhenium, an element in group 7 of the periodic table. In2006 Stamm received the ‘Inventor of the Year’ award fromSiemens in recognition of his work.

Stamm’s protective layers are also used in the turbine in Block4 of the gas-fired power station in Irsching. This gas and steamblock-type thermal power station is representative of the conflictingpriorities of modern energy policy like no other. Whenit was commissioned in 2011, it held the world record forefficiency: more than 60 per cent of the energy within thenatural gas could potentially be converted into power. ‘Potentially’is the keyword here, because the plant is now only usedas a reserve power station. Like virtually all other gas-firedpower stations in Germany, it is being forced out of the marketby the increasing number of renewable energies. ‘That isquite annoying,’ says Werner Stamm, pondering the situation.

Research is also suffering as a result of the mothballed gasfiredpower stations. Even though it may be possible to furtherimprove their efficiency, Stamm is constantly asked: ‘Why goto the effort?’ All the same, he is convinced that further improvingthe efficiency of stationary gas turbines will pay off inthe long term. ‘We are gradually moving towards a temperaturelevel of up to 1,600 degrees.’ Furthermore, gas-fired powerstations would be operated within part-load ranges much moreoften in future. As such, the level of efficiency not only has tobe optimised for a certain load point, but across a wide range.Such a flexible operation model is also not without its challengesfor the field of material research. ‘In future we mustconduct even more precise research into how the change inload affects the lifetime,’ says Stamm.

In this regard, the joint research carried out within the FVVis not the only buttress for Werner Stamm, but it is a very importantone. Over the years he has presided over several researchprojects concerned with investigating thermo-mechanicalfatigue. ‘I kind of fell into it,’ explains Stamm. His first pro-ject about 25 years ago was an investigation into corrosion,which was carried out at the TU Darmstadt. FVV workinggroups and meetings would now be unthinkable withoutStamm’s presence. Yet it is not just the work-related contentthat Stamm appreciates, but also the way in which peopleinteract with each other: ‘It’s OK to ask stupid questions,’ saysStamm, providing an example. He is referring to fundamentalquestions, the very questioning of existing knowledge itself.‘Such an approach helps us all to move forward; after all,physics is the same for everybody.’

Gas-fired power stations must become more flexible

The man from Mülheim likes to come down from the dizzyheights of physics when he meets up with his former handballteammates, who still call him ‘Stammi’. They no longer activelyplay, but the camaraderie remains. His love of craftsmanshiphas also remained, and he recently organised an exhibitionfor a neighbour whose hobby is building Stirling engines –reciprocating engines with external combustion.

Photo Credit: FVV | Rui Camilo

The people behind modern research

This article is from our 60th anniversary book »PRIMEMOVERS«. Technology journalists Johannes Winterhagen and Laurin Paschek provide on 200 pages an insight into the work of 24 leading people from industry and research who are passionately pursuing their ideas for greater efficiency and fewer harmful emissions from combustion engines and turbomachinery. The book can be ordered at the price of 39,90 Euros from the VDMA-Verlag GmbH. It is available in English and German.

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Dr. Werner Stamm

Werner Stamm was born in Mülheiman der Ruhr, a place to which he is still very much attached. Upon leaving school he initially completeda precision engineering apprenticeship. After a spell at a college of further education, followed by military service, which he spent in a signal battalion, he studied physics at the University of Duisburg. In 1988 Stamm was awarded a doctorate for the work he conducted in the low-temperature physics laboratory at the University of Duisburg. At the same time, he also worked in a special research field. After spending some time in Japan and working in the field of cleanroom technology for a Fraunhofer Institute, he joined Siemens in 1991, developing gas turbines in Mülheim an der Ruhr. Stamm still works there today as a development engineer.

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