SpinOffs

Wind power generation is rapidly growing worldwide, and with that growth, demand for wind turbine design engineers is also growing.  However, an engineer who has experience designing turbines in most applications, will often have trouble translating their hard-won skills for general turbine design, into the wind turbine design. Why? 

As one might expect, the temperature of a substance typically increases as energy is added to it. This is the case with most substances in all phases. The exception is when a substance crosses to a different phase, which usually involves no temperature change. The energy difference between these phases is called the “energy of formation”.  

Most turbomachines need to operate across a range of fluid flow rates and speeds. This is obvious in transportation applications where gas turbine engines and turbochargers need to operate at all of the speeds, altitudes and temperatures that the vehicles they power will encounter. In industrial and refrigeration applications, turbomachines need to have a wide operating range to make them appealing to end users who want efficiency under many operating conditions.

I think we can all agree that designing turbomachinery is hard. There are just so many moving parts (pun intended) in the design process, and they are all interconnected.  When you change the blade shape, it changes the aerodynamics, and could impact manufacturability. Everything you change has a cascading effect across many different areas, because all of the areas are linked; just like a Rubik's^® cube! Only, in turbomachinery design, you are not always trying to get all of the sides to be one color. Heck, even a 3-year old can do that. 

Frequently, there is a need to reconstruct 2D and 3D geometry from reported or measured surface data points. In most cases, the provided surface data include significant amounts of noise for various reasons, including quality of the scanned blade, deviations produced by the measurement system, curve digitization errors, data digital rounding and truncation, and errors in reporting the data.  This noise hampers quality surface reconstruction and masks the understanding of the design intent of the profiles.  It also affects the accurate representation of the geometry, manufacturing complexity, and aero performance which forms the basis on which a design engineer can execute any design improvements.

In the mid 1980’s, while serving in the Canadian Air Force, I had the good fortune, on one of my many adventures, to fly into Sondrestrom Air Base in Greenland. The Base is at the head of a beautiful fjord, so the scenery during the flight to Sondrestrom was magnificent. We arrived in the early summer on a beautiful clear day. I got out of the plane and wandered around the base while the aircraft was being serviced. One feature that caught my eye was all of the bright yellow ropes and stanchions that were strung from building to building. I couldn’t figure out what they were for, so I stopped one of the locals and asked, “Why the Yellow Ropes?”  Now, for those who are not students of the geography of Greenland, Sondrestrom is north of the Arctic Circle, and, apparently, the weather is not always as bright and clear as it was that day! As a matter of fact, one of the meteorological phenomena in the area was virtually instantaneous whiteouts, caused by snowstorms funneling up the fjord. Several people had been caught out between buildings and become disoriented during a blinding storm, a dangerous thing during the long darkness of winter. To eliminate this danger, they had put up the yellow ropes to safely guide people to their destination.

Many energy recovery, drive cycles (Organic and Steam Rankine cycles) and rocket propulsion cycles require the use of a turbine that operates at low volumetric flow and high-pressure ratio. Additional requirements include low cost, reduced weight, and reduced axial length (for robust rotor dynamics).

Many gas turbines with radial compressors utilize a radial-to-axial inlet duct upstream of the first compressor stage. Aside from the fact that flow in the duct generates aerodynamic losses, the flow profiles at the duct exit, delivered to the inlet of the first impeller, also affects the performance of the compressor. 

High-efficiency, low-cavitation pumps often require a screw type inducer to treat the inflow to the main radial/mixed flow pump blades. Efficiency and head rise, split between inducer and main pump, are questions explored during the design process. Another important design consideration is the tolerance to cavitation. Finding the best solution, when there is often a trade-off between two or more operational conditions, is difficult. We have found that multi-objective optimization, for single or multiple operating points, is the best tool to use.

Thanks to early pioneering efforts by Dr. David Japikse and his team, Concepts NREC has been at the forefront of turbomachinery design optimization for the past 15 years.