This post is about one of the most useful design tools for rotordynamics of turbomachinery: The Undamped Critical Speed Map. A critical speed map can provide a great deal of insight on the potential...
A blog on what's new, notable, and next in turbomachinery
By Andrew Provo
Mar 22, 2019
I work with water a lot here at Concepts NREC. Water is frequently the fluid that flows through various types of rotating equipment we design to either release or store energy. Mankind’s fascination with manipulating the movement of water goes way back; read Mark Anderson’s blog on Early Water Handling to see just how far back it goes. Today, more advanced turbomachinery is used for both hydroelectric and hydrokinetic applications.
Working with water sometimes includes consideration for the animals that live in it. For example, Alden Research Laboratories needed a “fish-friendly” turbine, designed to minimize the pressure gradients through the turbine to avoid fish mortality (which is caused by sudden pressure changes). Contrary to what you might expect, research showed that fish passing downstream through a hydraulic turbine tend to die more from the pressure shock, rather then the impact of the blades. This observation was the inspiration for a turbine designed specifically to minimize the rate of pressure change. The design that Concepts NREC developed involved extensive use of CFD that included the inlet volute, gates, runner, and downstream diffuser to optimize the overall system to deliver low fish mortality and high-power extraction.
A lot of turbomachinery designed with water as the working fluid is big. A particularly memorable job that I worked on was designing and developing a 70 kW hydrokinetic turbine, that was installed at the Army Corps of Engineers Lock and Dam 2 on the upper Mississippi River. That’s me, standing inside the turbine. It utilized the velocity of the flow in a conventional hydroturbine’s tailrace to provide up to an additional 7% power generation capacity to the existing facility.
I am endlessly fascinated by water’s potential. From rivers to oceans, the world’s water presents us with tremendous opportunities for clean energy. Below is a diagrammatic representation of an oscillating water column power generation system. We worked on developing a variable pitch rotor to maintain the direction of rotation and maximize efficiency over both the inlet and exhaust strokes of the system.
And there are still a lot of untapped (pun intended) opportunities out there. Consider the Oak Ridge National Laboratory study on untapped hydropower potential. According to them, there are nearly 40 Gw of untapped power in America’s waterways, the vast majority of this power remains undeveloped. This is usually because the commercial and environmental cost of dam construction often makes the development of small-scale conventional hydroelectric installations (50 kW–500 kW) untenable. To help tap this enormous potential, we have been developing both run of the river and ultra-low head turbine solutions to make this power resource both economically and environmentally viable. These systems act like propellers in reverse and are much less intrusive and expensive to install in a river.
Storing energy in water also requires turbomachinery. Pumped energy storage is one method of dealing with the intermittent nature of many renewable energy systems without the environmental impact that is associated with the manufacture and disposal of large-scale battery storage. To achieve the highest possible round-trip efficiencies from pumped energy storage, very high pump and turbine efficiencies are required.
In addition to turbomachinery’s ability to utilize water as a power generating or energy storage resource, it can also be used to hold a supply of potable water for drinking and irrigation. Innovative desalination systems, based on high-efficiency turbomachinery, could be used to supply fresh drinking water to coastal locations.
Water is one of the world’s most critical assets, and moving into the future, the need for clean energy and fresh drinking water is likely to increase. I am proud to work at a company that is committed to being a partner in the global effort to responsibly utilize this precious resource.
Happy World Water Day from the team at Concepts NREC!
By Mark R. Anderson, CTO of Concepts NREC
Feb 25, 2022
With so many papers out there, I like to pass the word along when a particularly good one comes my way. My favorite paper for 2021 was titled “SELECTING A COMPRESSOR MERIDIONAL TOPOLOGY: AXIAL,...
By Dr. Dave Japikse, CEO/Chairman & Founder, Concepts NREC
Feb 11, 2022
Dave Japikse, the CEO/Chairman & Founder of Concepts NREC, speaks to e-pumps as a potential propulsion game changer, as well as ongoing rocket turbopump development and design considerations.