Demystifying “Pushbutton” Approaches for CFD & FEA Turbomachine Design

Demystifying “Pushbutton” Approaches for CFD & FEA Design, Analysis, Redesign, & Optimization of Turbomachines

centrifugalcompressordesignAlthough there is not just one way to design a turbomachine there sure is one way not to do it; blindly.

A misconception that I commonly see when teaching engineers about fundamentals of turbomachines, as well as when leading design workshops, is that some engineers (mostly the younger generations) envision themselves plugging numbers, pushing buttons and getting results immediately without any real brain power behind their actions.

Nowadays, software packages are an integral part of an engineer’s toolkit, but in the same way that a mechanic would not (or should not) use a screwdriver as a hammer, each software has its own applications and ways to use it.

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Innovation in Aerospace: Aircraft Compressor Design

Aerospace - croppedOur next webinar is on Thursday, April 30th! Are you an engineer involved in the Aerospace Industry and its latest development, a manager interested in improving the performance of your aircraft engines, or a student interested in the future of aerospace and the current climate of the industry? You should attend! During the webinar we will be taking a close look at the most recent trends and developments of compressors in aircraft engines with a focus on the key factors for the successful development of aircraft engines.

Key factors for successful development of aircraft engines include technological viability, performance, and re-usability. As one of the industry’s most high-technology products, aircraft engines require innovation in manufacturing and especially in design. They also face the need for continuous development in its technical capabilities in terms of achieving not only higher efficiencies and reliability but also safety and environmental legislations.

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Preliminary Design Explained

Thinker- 2-26-2015Companies utilize different principles to design new turbomachinery. A design exercise is an extremely complex task and requires knowledge of many design trade-offs. This article is intended to reveal preliminary design philosophy and clarify some mysteries in this fast solution method.

Let’s define a few terms first. Boundary conditions (BCs) are the inlet and outlet states of a working fluid. Design inputs are small number of variables that are necessary to begin the design exercise. SoftInWay identifies BCs, design mass flow rate, rotational speed, and a few dimensions as the design inputs. The Preliminary design is a tool for quickly assessing design outputs giving many sets of design inputs. The algorithm utilized in the Preliminary design tool is an inverse solver. Inverse solution in this context implies finding geometry of interest knowing a very few design inputs.

How stuff works? The whole process comes down to estimating losses in each component and then calculating fluid states and component geometry applying simple kinematics and conservation equations. Calculated geometry and states are used to find real losses from loss models. This loss model results are compared with the guessed values and the algorithm repeats until they agree. In a practical implementation, however, the solution scheme will be more comprehensive but underlying principle remains the same — design output heavily relies on the models.

Loss models are extremely important and they determine the range of applicability for an industrial code. The models are collective work of many scientists and designers. Usually, they are some empirical correlations serving large family of components and predicting real machine performance quite well. Can we trust the results? That raises a lot of concerns and skepticism. The predictions are as good as the models that describe the physical processes. Verification and validation plays vital role in the developing of the code. The industry trend is to rely on published scientific data as a first iteration and calibrate models while working on real projects. Range of applicability is determined for each empirical correlation. For example, the veteran of compressor design Ronald Aungier shows that his loss model with respect to return channel in centrifugal stage has good agreement with experiment (Figure 1). Therefore, Aungier’s model can be used for similar machines.

Figure 1 -- Loss in optimized return system design

Figure 1 — Loss in optimized return system design

Preliminary design space study — know your limits! When an aerodynamicist is given specification on a new piece of machinery, he/she does not know anything about all the details of the design. Preliminary design can quickly show achievable performance for the machine, estimate critical relationship between design inputs and outputs, and facilitate in determining trends and trade-offs. Design space is a set of many preliminary designs. Because inverse solver is fast, a designer can generate thousands of designs in the matter of eye blink. Moreover, set of mathematical statements and state-of-the art aerodynamic reasoning allows outputting three dimensional geometry for each preliminary design with properly sized components. Ultimately, exploring the design space will eliminate costly mistakes prior to detailed design is carried on.

Myths and misconceptions about preliminary design. Inverse solver does not solve potential flow problem. Inverse task does not perform boundary layer analysis. Preliminary design is not a Navier-Stoks solver. Inverse design is not a table look-up but utilizes empirical loss model in the tested and verified domain. At the same time, preliminary design is not a blade-to-blade analysis tool. Preliminary design is a good starting point for further detailed design and analysis including blade profiling, performance map generation, impeller design, structural analysis, and CFD. All the above can be accomplished within one integrated design environment such AxSTREAM.

Good luck with your challenge!

IvK

References:

  • http://www.dreamstime.com/
  • Aungier R. Centrifugal Compressors. The strategy for aerodynamic design and analysis. ASME Press. New York. 2000

SoftInWay Launches STU – An Online Turbomachinery Training Resource

This week marks the official launch of SoftInWay Turbomachinery University – a new online resource for turbomachinery design training. The site, affectionately referred to as ‘STU’, was created after the SoftInWay Learning Center received high demand and positive feedback.

SoftInWay_Turbomachinery_Universtiy_-_2015-01-27_09.19.14

The site was reconstructed and redesigned into a cohesive learning portal, packed with webinars, courses, and software trials. Users can take courses on demand and earn certifications specific to certain topics. The first course focuses on axial turbines, beginning at the basics and continuing on to streamline design and optimization. Continue reading “SoftInWay Launches STU – An Online Turbomachinery Training Resource”

TBT Webinar – Developing Reliable, High Performance, Advanced 3D Blades

It’s Throwback Thursday which means we have another one of our favorite past webinars! This week’s is called Developing Reliable, High Performance, Advanced 3D Blades. It was the first of three in a special Steam Turbine Series

Since 1884, steam turbines have been exemplary turbomachines that have improved throughout the years with modern design advances. As steam turbines became common, the competition heated up and today efficiency continues to be a hot topic. One trending technique that makes steam turbines most efficient is advanced 3D blading. Continue reading “TBT Webinar – Developing Reliable, High Performance, Advanced 3D Blades”

TBT Webinar – Design of Impulse and Reaction Turbines

This week’s TBT webinar, Design of Impulse and Reaction Turbines Webinar #2: Applications for Supercritical CO2 Cycle, discusses important considerations for using high-density working fluids with small turbine sizes. Structural constraints and performance are considered and the full design process is demonstrated.

video2This webinar covers:

  • Supercritical CO2 cycle overview
  • Estimation of impulse and reaction turbine application rationality in modern supercritical CO2 cycles taking into consideration structural requirements and performance goals
  • Comparison of CO2 and steam turbines (impulse and reaction) for the same boundary conditions
  • Detailed flow path design with AxSTREAM

Who should watch:

  • Mechanical and aerospace engineers working on conceptual turbine design
  • Operation/Overhaul/Engineering managers seeking to increase energy efficiency
  • Everyone interested in how SoftInWay Inc., and AxSTREAM can help them with creating more efficient Turbomachinery

You can find the recording here, in our video center. Not registered for our center? Not a problem, just register and you’ll be emailed access info for all of our free learning materials.

Throwback Thursday Webinar – Green Energy and ORC

It’s #ThrowbackThursday and we’re sharing one of our past webinars called “Green Energy – Turbomachinery for Organic Rankine Cycles.”iStock_000015544357Medium

Growing global demand for energy coupled with environmental concerns from the prevalence of fossil fuel usage has created a strong demand for new sources of clean energy. This demand has inspired scientists and engineers to search for and propose new solutions to generate greener, cleaner energy. One of the new methodologies which has been proposed is generating electricity from low temperature heat sources, the Organic Rankine Cycle being among the most widely used. Such popularity encouraged innovation in the area, and inspiring various design modifications in conjunction with low temperature heat sources and with a wide range of power rates. Continue reading “Throwback Thursday Webinar – Green Energy and ORC”

Free Webinar: Maximizing Turbocharger Boost with Advanced Design Features

turbochargerinengineTurbochargers, nowadays, are becoming increasingly common in the internal combustion engines of automobiles in order to improve fuel economy and meet government emission regulations. A turbocharger must provide a designed increase in pressure under load condition (design point) while generating enough power at the low end (loss mass flow region). Internal combustion engine working characteristics, however, prevent a centrifugal compressor from generating enough boost at the low end when radial turbine rotational speed is low. Continue reading “Free Webinar: Maximizing Turbocharger Boost with Advanced Design Features”

Sustainable Turbomachinery

iStock_000015544357MediumThis past Tuesday was the 44th celebrated Earth Day. On Earth Day, more than 100 countries join together to literally stop and smell the roses, appreciate the splendor and beauty of Mother Nature and take extra efforts to be more conscientious for our shared home.

Turbomachinery, though not always the first thing that comes to mind when speaking on the subject of green technology, plays an important role toward our efforts for a more sustainable environment.
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Formula 1 Racing is Turbocharged

turbochargerinengineYes, the Formula 1 races have begun. The world is three races in with the fourth Grand Prix scheduled for April 20 in China.  As the world watches in awe at the versatility and speed (let’s face it, the races are all about the cars, right?), engineers marvel at the aerodynamics, energy recovery systems, turbochargers and internal combustion engines (because we love engineering).

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