SpinOffs

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.

In the mid 1980’s, while serving in the Canadian Air Force, I had the good fortune, on one of my many adventures, to fly into Sondrestrom Air Base in Greenland. The Base is at the head of a beautiful fjord, so the scenery during the flight to Sondrestrom was magnificent. We arrived in the early summer on a beautiful clear day. I got out of the plane and wandered around the base while the aircraft was being serviced. One feature that caught my eye was all of the bright yellow ropes and stanchions that were strung from building to building. I couldn’t figure out what they were for, so I stopped one of the locals and asked, “Why the Yellow Ropes?”  Now, for those who are not students of the geography of Greenland, Sondrestrom is north of the Arctic Circle, and, apparently, the weather is not always as bright and clear as it was that day! As a matter of fact, one of the meteorological phenomena in the area was virtually instantaneous whiteouts, caused by snowstorms funneling up the fjord. Several people had been caught out between buildings and become disoriented during a blinding storm, a dangerous thing during the long darkness of winter. To eliminate this danger, they had put up the yellow ropes to safely guide people to their destination.

Space launch vehicles can exhibit self-excited longitudinal oscillations, also known as “Pogo” — so named because the phenomenon vibrates the rocket up and down in a manner similar to bouncing on a pogo stick. The vibrations severely impair the astronauts’ ability to pilot or respond to emergencies and can cause structural failure of the vehicle. NASA first became aware of the disastrous consequences from Pogo during the Gemini-Titan program. The issue continued to plague the agency through the Saturn V Moon launch missions.

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:

A challenge in the engineering profession is that we, too often, look at complex problems as requiring complex solutions. As an example, a customer recently asked Concepts NREC to perform a very complex full-scale test. After a few rounds of clarifying questions, it became apparent the purpose of the test was to validate an analytical model. With this additional insight, we recommended a partial scale test that would achieve the same outcome, for a fraction of the price and time. The customer was delighted with this simpler (and cheaper) solution to their problem.

The testing of turboshaft engines is necessary to ensure that post-repair performance meets or exceeds requirements for safe aircraft operation.  Testing typically involves several phases such as:  seal break-in; transient response; performance check and control system validation.  Dynamometers are used to simulate the load imposed during operation during testing.