Compressor Design: Influence of the Impeller Exit Blade Angle

by Dimitri Deserranno on Jan 19, 2018 8:46:55 AM

During the compressor design process, one of the key optimization steps is to adjust the impeller exit blade angle with the goal of achieving the desired pressure ratio, efficiency and range.


When we consider the fundamental relationship of impeller work, using Euler’s turbomachinery equation for specific work (Figure 1), we can see how the impeller blade exit angle has a direct impact on the impeller work through changes in the impeller exit absolute tangential velocity, CƟ2. Based on this equation, you might think that having pure radial blades is best, since radial blades allow for more work to be performed (for a fixed impeller exit radius), leading to higher pressure ratios. Unfortunately, there is a downside….

A New Application for Air Brake Dynamometers?

by Francis A. Di Bella, P.E. on Jan 12, 2018 10:33:46 AM

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.

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