SpinOffs

Yes, you read that right. Learnt. It’s in the dictionary; look it up if you don’t believe me. I believe it’s one of those words that came over on the Mayflower and found its way into Webster’s early version of spell-check. I was exposed to this word through a group of Englishmen in the Engineering group here. One of those Englishmen, Colin Osborne, has been a significant contributor to our robust “Lessons Learnt” database throughout his decades-long career here at Concepts NREC. If you don’t have a “Lessons Learnt” database at your company, I suggest you start one right away.

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.

Historically, testing has played a critical role in the turbomachinery design process and multiple rounds of “design, test, analyze, repeat” were not uncommon.  Today however, the industry seems to be drifting away from development testing. Often, the only scheduled test in a development program is the performance validation test of the first assembled system. I believe this trend exists for three main reasons:

There is obviously a huge amount of interest in Supercritical Carbon Dioxide (sCO₂) within the energy industry. One reason is because sCO₂ Brayton power cycles operate in the same way as other Brayton cycles, but with a much higher power density. This has the potential for greatly reducing the size and cost of equipment. Additionally, efficiencies can reach as high as 40% for an sCO₂ system, compared to about 33% for a typical heat recovery system. 

If you are a turbomachinery engineer, you know you can spend days, weeks, or even months analyzing various design iterations, looking for the optimal choice for the application.  When you go to present your final design for review, you want it to look as good as you know it is. Choosing the best post-processor for CFD results can not only save time in creating the desired views, but also show solutions at their best.  Without proper post-processing, your solution can lose that "je ne sais quoi" that made it the best design for the application. In other words - it has to look as good as you know it is.