Turbo Expo 2014 took place in Dusseldorf, Germany in June under the auspices of the ASME’s International Gas Turbine Institute (IGTI). Mike Ireland, ASME Managing Director ASME Research & Technology Development, introduced the keynote session by calling Turbo Expo the “flagship conference for ASME”, and as such, this year’s event enjoyed a highest ever attendance at over 3000 people, up from 2400 in 2013. A further record was set with had 1,229 papers presented in 329 sessions. The exhibit featured 118 vendors.
Life cycle costs
We tend to hear all about turbine problems, catastrophic failures, and the teething issues on the latest and greatest machines. This can leave a false impression on turbine reliability and lifespan. But the reality is that many gas turbines (GTs) remain in operation for an awful long time. Charles Soothill, Senior Vice President of Technology, Alstom Switzerland, highlighted the very first GT, a 4 MW model in Neuchatel, Switzerland in 1939 that stayed in service until 1997.
“With more renewables, which are being given priority onto the grid, gas plants are running less and so we are seeing even greater lifecycle cost pressure,” said Soothill. “Further, more startups create lifecycle fatigue damage.”
According to his estimates, GT lifecycle costs amount to twice equipment first costs. Steam turbines, on the other hand, have similar lifecycle to first costs. He pointed to Alstom’s work with additive manufacturing techniques such as selective laser melting as a means of replacing the casting of blades.
Gas generation plants
This theme of total lifecycle costs continued throughout the keynotes. Pratyush Nag, Director of Engineering, Product Line Manager, Siemens, began his talk by summarizing the prediction for the worldwide power-generation mix. Gas moving from a current 23 percent share of the energy mix will reach 25 percent by 2030. That number, though, is made to look worse than it is due to the fact that there will be a 50 percent rise in electricity demand during that period.
Meanwhile, coal will fall from 40 to 35 percent and oil from 4 to 2 percent. The fossil fuel market share will decline from 67 to 62 percent which will be mainly compensated by renewables which are expected to soar from 4 to 13 percent. However, gas generation power plants are still expected to be the mainstay to compensate for the volatility in renewable power generation. This led into a discussion of how to keep the existing GT fleet running longer despite changing operating conditions.
Nag stated how users are evaluating overall lifecycle costs for their business case evaluations that don’t just cover power output, but include reliability and availability on the grid. This is exerting an influence on warranty terms. “To reduce lifecycle costs, we have to make progress in system integration, clearance controls, coatings and process simulations, maintenance services,” said Nag.
Gain in power and efficiency
Siemens has developed thermal barrier coatings (TBCs) and sensors to better monitor hot gas path components and thereby lower lifecycle costs. In addition, Hydraulic Clearance Optimization (HCO) shifts the rotor against the flow direction to optimize turbine clearances during steady state operation. The axial shift of the rotor is performed automatically by hydraulic pistons behind the compressor thrust bearing. A gain in power and efficiency due to the conical shape of the turbine is higher than the potential losses on the compressor side. Nag said it produces a power boost of several MW on some Siemens machines and that over 100 units already have it in operation.
Karsten Muhlenfeld, Director Engineering, Rolls-Royce, rounded out the keynotes by discussing aero engines. He said the money is no longer in the sale of engines. OEMs, therefore, have to be up to the challenge in a market filled with an abundance of aftermarket challengers.
“While it is important to build new engines, it is more important to service them well,” said Muhlenfeld. “We now make the biggest turnover out of servicing engines, more than 55 percent of our total turnover.”