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 to believe that the physicist must have a life beyond the world of super conductivity and high-temperature-resistant alloys. They look big and capable. And in actual fact, Stamm, the son of a metalworker, initially completed a precision engineering apprenticeship after leaving school. ‘Stammi’, as he is affectionately called by his handball team mates, was destined to take on his father’s business one day. But things turned out differently: his father had to close the metal working shop, so his son and chosen successor gained the relevant entrance qualifications 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 during his final year project at university. He investigated the magnetic behaviour of alloys whose linear expansion remains unchanged with temperature fluctuations. They were also the subject ofhis doctoral studies, which he completed in 1988 in a special research field. It was at this very time, when Stamm was also investigating the phenomena of superconductivity at temperature sapproaching minus 270 degrees Celsius, that he first established professional contact with Siemens. When he eventually started working at the Mülheim development centre of the electrical company in 1991, the temperature level also suddenly began to rise: his job was to develop and classify materials for gasturbines. At the time, the turbine blades directly behind the combustion chamber had to withstand temperatures of around 930 degrees Celsius.

Yet it was already clear that there would be a trend towardsever higher temperatures. ‘That is the crucial factor for improving the efficiency of a gas turbine,’ explains Stamm. Today’s turbines reach hot gas temperatures of up to around 1,500 degrees 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 have to be taken into consideration. Accordingly, Stamm opted for layers of insulation applied to the base material of the turbine blades. ‘It wasn’t my idea; people had been researching it 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-resistant ceramic material based on gadolinium zirconate. A bonding layer underneath it ensures that it adheres to the base material. It is this layer that makes it possible to achieve a lifetime of 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 layer could be significantly improved by adding up to two per cent rhenium, an element in group 7 of the periodic table. In 2006 Stamm received the ‘Inventor of the Year’ award from Siemens in recognition of his work.

Stamm’s protective layers are also used in the turbine in Block 4 of the gas-fired power station in Irsching. This gas and steamblock-type thermal power station is representative of the conflicting priorities of modern energy policy like no other. When it was commissioned in 2011, it held the world record forefficiency: more than 60 per cent of the energy within the natural gas could potentially be converted into power. ‘Potentially’ is the keyword here, because the plant is now only used as a reserve power station. Like virtually all other gas-firedpower stations in Germany, it is being forced out of the market by the increasing number of renewable energies. ‘That is quite annoying,’ says Werner Stamm, pondering the situation.

Research is also suffering as a result of the mothballed gasfired power stations. Even though it may be possible to further improve their efficiency, Stamm is constantly asked: ‘Why go to the effort?’ All the same, he is convinced that further improving the efficiency of stationary gas turbines will pay off in the long term. ‘We are gradually moving towards a temperature level of up to 1,600 degrees.’ Furthermore, gas-fired powerstations would be operated within part-load ranges much more often 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 challenges for the field of material research. ‘In future we must conduct even more precise research into how the change inload affects the lifetime,’ says Stamm.

In this regard, the joint research carried out within the FVV is not the only buttress for Werner Stamm, but it is a very important one. Over the years he has presided over several research projects concerned with investigating thermo-mechanical fatigue. ‘I kind of fell into it,’ explains Stamm. His first project about 25 years ago was an investigation into corrosion, which was carried out at the TU Darmstadt. FVV working groups and meetings would now be unthinkable without Stamm’s presence. Yet it is not just the work-related content that Stamm appreciates, but also the way in which people interact with each other: ‘It’s OK to ask stupid questions,’ says Stamm, providing an example. He is referring to fundamental questions, 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 dizzy heights of physics when he meets up with his former handball team mates, who still call him ‘Stammi’. They no longer actively play, but the camaraderie remains. His love of craftsmanship has also remained, and he recently organised an exhibition for 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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