EXPLORE THE POSSIBILITIES
Keeping a new turbine design turning
Siemens Energy uses Simcenter to reduce simulation time from 235 minutes to just 2 minutes. That's over 99% reduction per simulation
By Richard Williams
Developing a new gas power turbine is a challenging task. Rotors spin at thousands of revolutions a minute, which means if you haven't got everything right, your new design could quite literally shake itself apart.
So when it came to developing a new lightweight and efficient power turbine for a new industrial gas turbine aimed at improving emissions and creating a greener solution, engineers needed a way of simulating the dynamics of the rotor.
Bringing down emissions
Siemens Energy is on a drive toward greener power. The group is not only helping its customers meet their growing energy demands but also it is coming up with solutions that can help protect the climate. The company has developed a range of ways to accelerate decarbonization, new methods to help its customers transition toward renewable energy, and has also helped bring down the emissions of components that use more traditional fuels.
Slimming down
As part of this drive toward greener power, Dr. Zhiqiang (David) Meng, technical specialist, and Richard Bluck, head of the compressor rotor group at Siemens Energy, came up with a new gas power turbine concept featuring a lighter structure with more efficient low-blockage struts. Because, when it comes to saving energy, reducing weight is everything. However, in the world of rotors and turbines, that does bring up a whole host of challenges.
A slimmer and lighter design was key to improving the aerodynamic performance and cost of the new turbine, but a lighter design meant a more flexible structure, which can play havoc with the rotor dynamic behavior if the vibrations are not studied upfront.
Proof of concept
Meng and Bluck needed to carry out detailed simulations to prove the operational safety and efficiency of their new design and to show that the new concept had maintained the operational margin of critical speeds and stability. Not least because the new turbine had to comply with American Petroleum Institute (API) standards.
Traditionally, Siemens Energy used numerous simulation tools, but they faced the issue of the rotor dynamics being only one part of the overall system of the turbine. It had to be integrated with all the other elements to ensure it ran as expected when the complete model was assembled. The challenge Siemens Energy found, was that different departments were using different simulation tools, so integrating the separate models took time and made it difficult to reach the optimum design within a reasonable period.
Things had to change. This time, Meng and Bluck decided to use Simcenter™ 3D Rotor Dynamics software, part of the Siemens Xcelerator business platform of software, hardware and services. Simcenter 3D allowed Siemens Energy to share models with other teams and make design changes more rapidly while completing the overall product based on precise simulation. It could also support all the necessary calculations.
Simulating success
A heavy, thick stator design of traditional gas turbines provide structural support and constant stiffness but moving to a lighter, more flexible concept meant Meng and Bluck needed to know if the materials would flex. Since, if the materials flexed, they would have to consider problems associated with resonance frequencies. Different materials and designs have different resonances therefore a change in either or both can be detrimental to the stability of the final product. To ensure the turbine is functioning perfectly, Meng and Bluck had to identify the rotational speeds at which resonance occurs to avoid or limit resonance as much as possible.
Simcenter 3D enabled Meng and Bluck to use a component mode synthesis (CMS) super-element approach. While this sounds complicated, the technique enabled the team to create much smaller and lighter models that were made of modes and matrices of the component parts. Because the model is reduced in size, it allowed the rotor dynamics team to save a lot of CPU time in its simulations.
Meng and Bluck modeled the dynamic stiffness of their new spoke frame stator so it represented a flexible structure independent of the rotor. They also used 2D multi-harmonic axisymmetric modeling of the rotor and 3D FE modeling of the stator to create a complete model of both parts. The pair were also able to identify resonance frequencies and simulate amplitude vibrations.
Teamwork
Siemens Energy did not take on this project alone. The support provided to Meng and Bluck kept the project on the right track. While the team had to learn Simcenter 3D they were not only provided all the tutorials they needed but also engineers from Siemens Digital Industries Software were accessible, and the design team were quickly able to fully understand the capabilities of Simcenter 3D Rotor Dynamics and prepare highly accurate simulations.
“Siemens Digital Industries Software support was fantastic throughout the project,” said Bluck. “Not only did they help us get started with a new product, but they provided expertise whenever we needed it.”
A 99% CPU reduction
The results for this project are quite staggering. Meng and Bluck say the use of the super-element model meant that each simulation could be completed in just two minutes compared to 235 minutes when it was not used - a reduction of more than 99% in computation time, and that is per simulation. Additionally, the rotor dynamic analysis of the combined rotor and stator model showed that with the lighter and slimmer spoke frame, the power turbine still met all API requirements while delivering both cost and performance benefits.
Timely turbine
The adoption of Simcenter 3D led to the successful verification of a more efficient gas power turbine design much faster than would have been previously possible. Not only were Meng and Bluck able to make new and better calculations, but it also enhanced collaboration across teams as they were able to seamlessly share models with other departments, streamlining the process of integrating the new stator support structure design with the complete power turbine.
“Using Simcenter 3D Rotor Dynamics made it much easier to share models with other teams,” explained Meng. "We were able to make design changes much quicker and finish the overall product based on accurate simulation.”
Rotating future
As part of the project, 20 engineers at Siemens Energy have been trained in Simcenter 3D Rotor Dynamics. This not only helps with their work on rotor dynamics but also other engineering projects. Now that they are familiar with the Simcenter 3D user environment they can more easily transfer their skills to other Simcenter 3D packages that are used throughout the organization.
Introducing multiple engineering teams to Simcenter 3D is also advantageous to the rotor dynamics team since they can now call on colleagues to help meet tight deadlines. Previously, it would have taken too long for them to get up to speed on the simulation solution to make it worthwhile. Now as more engineers become familiar with Simcenter 3D, they don’t need to learn a new package because the overall environment is the same. They only need to learn the functionality that is specific to rotor dynamics, which can be picked up much more quickly.
Tomorrow's benefits
As Siemens Energy increases its use of Simcenter 3D, the company will continue to realize more benefits as it develops a more dynamic and agile team. The company expects to benefit from the increased ability of engineers to collaborate more easily, enabling them to seamlessly shift between projects. Ultimately, using Simcenter 3D will help deliver even better products faster, enabling customers to meet their efficiency and decarbonization targets sooner.
