SpinOffs

Valentine’s Day is February 14, and while some cynics refer to it as a “Hallmark holiday”, most people commemorate the day in some way. One of the biggest challenges is finding a card that perfectly captures the way you feel about someone, while also reflecting who you are.  Well, Concepts NREC has created some turbomachinery-themed Valentine’s Day cards for engineers. These fall into the Art end of our Art-to-Part Solution.

Gifts for Engineers can usually be segmented into a few categories: Things you have to put together, science fiction, gaming, new technology, and witty phrases printed on stuff. A Google search of the term "Best Gifts for Engineers" will quickly validate this claim.

Credit for the first gas turbine engine used in flight is given to Dr. Frank Whittle.  Dr. Whittle maintained a steadfast commitment to developing gas turbine-powered aircraft in the midst of World War II when England was being attacked by Germany’s conventional aircraft bombers. While the gas turbine aircraft wasn’t developed early enough to impact WW ll, the interest in increasing the speed of aircraft continued to spur development for use in commercial as well as military planes. The advancements in gas turbines, combined with rapid advances in several technologies, including rocketry, computers and material sciences, contributed to the dawn of the Space Age.

Gas turbines (or GTs) are important in the power generation sector due to their high efficiency, cleaner emissions and faster startup than old coal-powered plants. These power generators can range from small, local power supplies to huge units, large enough to power a city.  Even with the surge in renewable energy sources, there will always be a need for power when the sun goes down, on a windless day or when power peaks are expected. GTs fill this power gap. GTs are very power dense, meaning they can produce a lot of power in a relatively small footprint. This is very useful in a city, offshore, or where vast landmasses are unavailable. 

The 2018 ASME Turbo Expo in Lillestrøm, Norway was, as always,  a smorgasbord of papers and presentations on the latest and greatest ideas in turbomachinery and gas turbines. Two of our favorites were from Mark R. Anderson and Felipe F. Favaretto, Concepts NREC employees. Coincidence? I think not. Felipe presented, “Development of a Meanline Model for Preliminary Design of Recirculating Casing Treatment In Turbocharger Compressors”:

Turbine inlet temperature is one of the most critical parameters in the Brayton cycle of gas turbine engines. One way to increase the cycle efficiency is to increase the turbine inlet temperature, as illustrated in Figure 1. Here, a typical Brayton cycle T-S diagram chart visualizes the impact of higher turbine inlet temperatures on higher efficiency. Indeed, the area between the solid curves through points 0-3-4-8 represents the useful power generated by the turbine. The cycle efficiency can be calculated by dividing this area by the total area below curve 3-4, being the heat input. The dash lines convey the cycle with increased turbine inlet temperature, and the new cycle efficiency is the area in 0-3’-4’-8 curves divided by the area below curve 3’-4’. It is easy to see how a higher turbine inlet temperature increases cycle efficiency. Because of pursuing higher efficiency in modern gas turbine engine design, turbine inlet temperature has been pushed to a level that most material cannot withstand without effective cooling. Figure 2 shows the increasing trend of turbine inlet temperature since the 1940’s. Since the 1970’s, the turbine inlet temperature has been above material capability through the introduction of turbine cooling techniques.

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. 

My gym has been crowded with a lot of new people these past couple of weeks. It happens every year in January as people try to stick to their New Year’s Resolution to exercise more. I don’t mind the crowds; they are usually gone by February. One newcomer that did catch my engineering eye, was the new exercycle. It is a bicycle seat with a single, large and bulky looking wheel. The large wheel seems out of place next to some of the other machines that tend to have a much more streamlined appearance. The wheel is spun by the rider much like a typical bicycle and serves to absorb the power from the rider. The exercise cycle is called an Airdyne.

How did I get from not knowing (or caring) anything about home-built aircraft to owning a gas turbine powered helicopter? As you might imagine, it’s complicated.

New engine development is a costly endeavor and making the right decisions early in the engine design is extremely important. It requires multi-disciplinary consideration of the engine thermodynamic cycle coupled with preliminary aerodynamic design of key engine components. This includes evaluation of size, weight and cost parameters, with constraints imposed by aero, structural, geometrical, manufacturing, and material requirements.