SpinOffs

In the world of aerodynamics, there are several branches and sub-branches of different types of aerodynamics. In the big picture the field of aerodynamics can be broken down into external and internal aerodynamics.   External aerodynamics is thought of external flow around an isolated body, with the typical example being flow around an aircraft wing section, or perhaps around an automobile. There is typically a far field ambient condition, with an isolated body moving through the field (or you can view it as the fluid moving over the body). Internal aerodynamics is thought of as a flow moving through some confined space or passage, with a prime example being flow through turbomachinery, such as a compressor or turbine. There are other ways to classify aerodynamic flow, such as subsonic flow (Mach No. <0.8, including low Mach No. incompressible flow, say Mach No. <0.3), transonic flow (around Mach No. = 1, say 0.8 to 1.2), supersonic flow (Mach No. > 1.2), and even hypersonic flow (Mach No. >5). Turbomachinery design encompasses the first three types of flow regimes, subsonic through supersonic. So in general, turbomachinery aerodynamics is predominately internal flow, over a range of Mach Numbers.    

It’s always interesting to look at the topics of my favorite engineering conferences and see what’s in vogue in a given year. What jumped out at me this year at the ASME TurboExpo was the hot topic of hydrogen.

Low reaction stages are often used as control stages of steam turbines, ORC turbines,  drive and rocket turbopump turbines. Some of the benefits of low reaction stages vs higher reaction stages are:    Smaller radial size (and weight) for the given power and rotation speed  Compatibility with use of partial admission, which is used to accommodate low volumetric flow, with the needed low pressure gradients in the rotor blades to reduce leakage penalties  Both above factors allow increasing of nozzle and rotor blade heights  Smaller radial size provides lower disk rim speeds and disk stresses  Low reaction generally means lower axial thrust of the rotor  Velocity stage configurations are possible for low reaction designs (Curtis stage for example, Fig.1). Velocity stages allow further reduction in radial size and increasing blade heights 

In my last blog I wrote about visiting a local middle school to give a talk on ‘What is Turbomachinery, and How Does It Work?’   The quiz at the end of the talk was for the students to list all the turbomachinery in their home. I had a few examples in mind to get the list started but was impressed with how long of a list we were able to generate after the students thought about it for a while. Since then the list has grown to include 40 items.   I will present those 40 below, but first let me repeat the assignment and the ground rules to see if you can think of more:   List every piece of turbomachinery in your home. Inside and outside (in your yard is OK). Positive displacement equipment is OK to list. Don’t include turbomachinery in your cars or any vehicle or wheeled yard equipment (that’s another list…)

On occasion I’m invited to a local middle school to give a talk to one of the science classes about ‘What Is Turbomachinery, and How Does It Work?’.   I teach in several of the turbomachinery design courses we give at Concepts NREC, and while I’m comfortable in those courses, presenting at this level was different. I originally found it a challenge to come up with a good presentation that would keep the students' attention, while still providing some science education as requested by the science teacher that invited me. Derivation of the Euler turbomachinery equation was probably out. The attention getters that seemed to work best to get the conversation going included bringing our turbocharger cut-away (definitely the biggest hit of anything I brought), along with other interesting impeller samples. From there getting into the purpose of various types of turbomachinery (compressor vs turbine vs pump) and a very high level discussion of energy transfer to/from a fluid, seemed to flow. Getting them thinking about some of the physical aspects of turbomachinery operation (Just how fast is 100,000 rpm?) also seemed to keep their attention.

If there’s one thing good about sitting in snarled traffic in Boston, it’s that you get to see some very original bumper stickers. The most recent bumper sticker I saw was probably the strangest one, no doubt created by some engineering professor who doesn’t see that the glass is half full, but that it has a safety factor of 2! Nevertheless, the bumper sticker stated the obvious when one thinks about it: ENTROPY HAPPENS! And then, to emphasize the point, the artist has the letters slowly “evaporating,” demonstrating graphically that entropy proceeds from order to chaos.

I recently got back from my favorite annual conference: ASME’s Turbo Expo. This year, someone thought it would be a good idea to hold it in Phoenix, Arizona…in the summertime.  While that’s not the choice I would have made, I did enjoy the conference very much and thought it was well worth attending. 

When discussing the efficiency of transforming one form of energy to another, circularity is the way to go. Anyone who has spent even a little time studying engineering thermodynamics knows that the continuous transformation of energy from a heat energy source to produce mechanical or electrical power must contend with components that operate in a cycle. The key word here being “continuous”. The combustion of any carbon-hydrogen bond material (i.e., fossil fuels), or the liberation of heat energy from any number of materials when placed in a piston-cylinder, would not be very useful if the piston is not returned to its initial “precombustion” position. It is literally the difference between the one-time launching of an object from the cylinder or the continuous production of rotary shaft power; power that can be used to propel a vehicle forward or turn an electric generator. It is the cyclic operation of the fluid in the thermodynamic cycle that enables heat engines and refrigeration cycles to provide continuous power, or cooling, that is needed for the safety, security, comfort and all the other “hierarchy of needs” that was so well formulated by the renowned humanist psychologist, Dr. Abraham Maslow.

Wow, Concepts NREC had a lot going on at this year's ASME Turbo Expo 2019 in Phoenix, AZ! We held our North American CAE User Group Meeting, spoke to over 200 people at our booth, chaired several sessions and presented two papers. In case you were not able to go, here are the abstracts from the two papers:

Summer is almost here, at least in my hemisphere, so here are some of the best places around the world people in the turbomachinery industry might find interesting! Know of another? Share your favorite!