# SpinOffs

## Specific Speed Performance Effects

by on Jan 18, 2019 10:35:00 AM

In my last blog, Specific Speed Demystified, I covered the mathematical definition of specific speed and how it relates to flow and work coefficient. The concept of specific speed has been a guiding principle for radial turbomachinery design for many years. Use of specific speed has been most heavily emphasized by Balje in his famous textbook and early publications.  In these works, he laid out several graphs that are still widely used today.

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## Specific Speed Demystified

by on Jan 11, 2019 9:40:00 AM

In my blog outlined the basic concept behind the flow and work coefficient. These nondimensional parameters are widely used to characterize axial and radial turbomachinery. Another widely used parameter for radial design is “specific speed”. For something with such a finite name, specific speed is perhaps the most mysterious and non-intuitive parameter in all of turbomachinery. In this blog, I'll lay the ground work for understanding specific speed.

## Flank Milling - How Hard Can It Be?

by on Jan 4, 2019 10:11:00 AM

When designing compressors, engineers often use ruled-surface blades with the goal of making a shape that’s easily manufactured on a 5-axis machine.  Theses blades can be quickly machined in one pass by aligning the side of a cutting tool to the rulings. This process is often referred to as “flank milling.”  The alternative is to make many passes with the tool tip, a process known as “point milling”. For the right application, flank milling is often favored for shorter cutting times and better surface quality, but there are some caveats.

## Engineering Resolutions for 2019

by on Dec 28, 2018 10:15:00 AM

I am an engineer and teacher, so as the year draws to a close, I like to look back on memorable events where an engineering activity went, or almost went, awry. Luckily all were caught in the nick of time.  Once the problem was adverted, my engineer’s sense of humor kicked in, and the result is the list below.  Hopefully, some of these lessons learned, or learnt, as my colleague Kevin would say, will serve as examples of what to be watchful for in the new year.

## Do You Design Turbomachinery with a Pocketknife or a Sushi Knife?

by on Dec 21, 2018 9:47:00 AM

Years ago, I got a pocketknife as a gift, and I absolutely loved it, still do. It came in handy during my college years, when I was really into camping and trekking. As the years went by, it stayed relevant to my new interests, such as motorcycle trips and surfing. It has helped me open cans, remove sea urchin spurs, and install shelves in my apartment. It has also saved me time and money on several occasions by fixing my bike. It is incredible how tightening some screws and pulling some wires can save towing costs – and a sunny day.

## The Wright Stuff for Turbomachinery

by on Dec 14, 2018 9:17:41 AM

As an engineer, you probably have at least some familiarity with the story of how two bicycle mechanics, named Orville and Wilbur Wright, invented controlled-powered flying machines at Kitty Hawk, NC. While I knew the basic story, I learned a lot more reading David McCullough’s book “The Wright Brothers,” which, I highly recommend. I could not help but make the connections to what we, in the turbomachinery industry, owe to these dedicated and industrious brothers. Their groundbreaking flight, pictured below, on December 17, 1903,  is often cited as the birth of modern aviation.

## Reverse Engineering - Going from Part to Art

by on Dec 7, 2018 9:12:37 AM

Have you ever needed to know the exact geometry of a compressor that has been running for years in your process plant? Perhaps you need to analyze how it would perform if the process fluid had to be changed to meet new government regulations. Or maybe there has been damage to the impeller and a complete mechanical analysis is required before a new one can be put into service. Eventually, everything, even well-designed turbomachinery, needs to be replaced or upgraded.

## Radial Compressor Geometry Primer - Video Blog

by on Nov 30, 2018 10:01:00 AM

Below is a 4 minute video blog from Mark Anderson, Concepts NREC's Chief Technology Officer, on the geometry of radial compressors. In it, he details the various parts of the compressor wheel, including the inducer, splitters, backsweep, etc. He also looks at open and closed (shrouded) impellers and the pros and cons of each design.

Click on the image below to launch the full-size video.

## 20 Great Gifts for Engineers from \$10 to \$2 Million

by on Nov 23, 2018 9:28:00 AM

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.

## Site Selection for Low- and No-Head Hydroelectric Pilot Plants

by on Nov 15, 2018 2:42:37 PM

According to the 2014 Oak Ridge National Laboratory study on untapped hydro-power potential, there is nearly 65 GW of untapped power in America’s waterways. The vast majority of this power remains undeveloped for many reasons, both environmental and commercial. One major impediment to the realization of this potential is the significant infrastructure required to install a conventional hydroelectric facility. The commercial and environmental cost of dam construction often makes the development of small-scale (50 kW–500 kW) hydroelectric installations untenable.

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