SpinOffs

   

For lower thrust rocket engine designs, either a Gas Generator (GG) cycle or a Dual Expander (DE) cycle can be considered, among others. While each of these cycles has its inherent advantages and disadvantages in an overall sense, each cycle requires a different approach to the turbopump assembly (TPA) design. This blog presents a general summary of advantages and disadvantages of each of these cycles, and obviously applies when the engine thrust level is low enough that a DE cycle can even be considered (less than about 50,000 lbf of thrust). This summary is not exhaustive and focuses primarily on the TPA, but provides information to help decide which cycle to use.

How Many Pieces of Turbomachinery (Fans, Blowers, Compressors, Turbines, Pumps) Do You Have in Your House? Part 2

by Daniel V. Hinch, Corporate VP Sales and Marketing, Concepts NREC on May 14, 2021 11:00:00 AM

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:

 

  1. List every piece of turbomachinery in your home.
  2. Inside and outside (in your yard is OK).
  3. Positive displacement equipment is OK to list.
  4. Don’t include turbomachinery in your cars or any vehicle or wheeled yard equipment (that’s another list…)

How Many Pieces of Turbomachinery do You Have in Your House?  (and a Pop Quiz)

by Daniel V. Hinch, Corporate VP Sales and Marketing, Concepts NREC on Apr 16, 2021 11:00:00 AM

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.

What’s So Hard About Designing A Pump?

by Daniel V. Hinch, Corporate VP Sales and Marketing, Concepts NREC on Oct 6, 2020 11:00:00 AM

Here at Concepts NREC, we work on a wide range of turbomachinery components designed for fluids ranging from gases to liquids, including supercritical fluids like supercritical CO2 which have properties of both gases and liquids.   We do a lot of pump design, consulting work and education. In fact our annual course on Centrifugal and Axial Pump Design is consistently one of the most popular.   Many engineers in the gas compressor industries consider pump design plain vanilla, without the added complexities of Mach number effects, but there are reasons why our pump course is so popular – pump design can indeed be very difficult, with a number of complicating factors that are unique or especially critical to the pump industry.

Entropy Happens… Deal with It!

by Francis A. Di Bella, P.E. on Jul 19, 2019 9:09:00 AM

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.

In Thermodynamics: “What Goes Around-Comes Around” is a Good Thing

by Francis A. Di Bella, P.E. on Jun 28, 2019 10:07:50 AM

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.

The Tesla Turbine – A Solution Looking for the Right Problem

by Barbara Shea on May 17, 2019 8:20:44 AM

The great engineer, Dr. Nikola Tesla, is best known for his work with alternating current (AC) electricity, but, did you know that he patented a bladeless type of turbomachinery in 1913? Called the Tesla Turbine, he developed it while trying to make an engine that was light enough to power his ultimate goal of building a “flying machine”. Tesla-type turbines can also be referred to as multiple-disk, friction, shear-force, or boundary layer turbomachinery.

Getting Real – Advanced Real Gas Models

by Mark R. Anderson on May 3, 2019 10:28:59 AM

The Refprop program

The calculations in the National Institute of Standards and Technology (NIST) Refprop program are generally considered the most accurate thermo-fluid models available.  The routines are widely used in many applications. 

 

The models

Several different models are embedded in the Refprop formulation. The most important are the  Benedict-Webb-Rubin equations of state for the pressure-temperature-density relationship. 

Going Through a Phase – Modeling Phase Change with Cubics

by Mark R. Anderson on Apr 26, 2019 9:32:08 AM

When fluids undergo a phase change (see Phase Change - Make Mine a Double), it typically has a very significant effect of the flow behavior and energy level of the system.  Some examples of this are: cavitation in a pump, condensing near the exit of a steam turbine, even the everyday phenomenon of the weather is basically a never-ending phase change process of water, and its interaction with air. 

Specific Speed Demystified

by Mark R. Anderson on Jan 11, 2019 9:40:00 AM

In my blog Flow Coefficient and Work Coefficient, I 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.

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