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

TBT Webinar: Centrifugal Compressor Design: Can You Really Avoid Choke and Surge?

It’s Throwback Thursday and we are sharing another of our past webinars! This week’s is called Centrifugal Compressor Design: Can You Really Avoid Choke and Surge?

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Surge and choke are inherent, sophisticated phenomena in centrifugal compressor operation. They limit the operational range of any centrifugal compressor and cause severe damage to the machine if it is in surge condition. Several books cover the development of centrifugal compressor surge and choke models that can be applied in compressor control systems in order to avoid surge and choke; while these methods focus retroactively, there are some proactive methods that can be applied during the design phase of the machine. Continue reading “TBT Webinar: Centrifugal Compressor Design: Can You Really Avoid Choke and Surge?”

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”

POWER-GEN 2014 – What you’ll see from SoftInWay

Powergen 2014December is already upon us, which mean Power-Gen International is right around the corner. As we finalize preparations, we’d like to share a sneak peek at what we’ll be showing at this year’s conference. SoftInWay has just released a new version of its design, analysis, and optimization software. AxSTREAM V 3.3 consists of enhancements and fully new features to improve the turbomachinery design process. These updates are the result of our client requests and collaborations. Here’s a look at a partial list of the new features:

  • Users can now design radial turbines at the conceptual design phase in rotor + stator + volute configurations.
  • They can calculate the influence of the heating working fluid through the compressors walls and the option to add radial heat exchangers in the flow path.
  • AxSTREAM V 3.3 has a new fluid toolbox allowing the creation of fluid files using NIST-defined pure and mixed fluid, as well as model combustion gases using custom fuels.
  • Users can calculate both the interference diagram for various rotation speeds and the stress in sections while accounting for root, shroud, disk, lashing wires, and even splitter blades.
  • There is a new library of attachments in AxSTRESS to allow shorter design time due to existing root and the opportunity to update blade geometry while maintaining predefined attachments.

Stop by booth #4854 to learn more about these features! SoftInWay CEO, Dr. Leonid Moroz, will also be speaking at the conference on Wednesday, Dec. 10th at 1:30. He will be presenting his latest paper, “A New Concept to Designing a Combined Cycle Cogeneration Power Plant,” written with SoftInWay Director of Engineering, Dr. Boris Frolov, and Mechanical Engineer, Dr. Maksym Burlaka.

Interested in scheduling an appointment with us at Power-Gen? Contact us at info@softinway.com. We’ll see you there!

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.

TBT Webinar – Supercritical CO2 Cycle – Advanced Power Conversion Technology

It’s Throwback Thursday and we’re sharing another webinar!

Are you looking for ways to increase your energy cycle efficiency?

Do you want to enhance your thermal or nuclear electricity generation project with advanced power conversion technologies?

Are you interested in expanding into the Supercritical CO2 Cycle business?

If you answered ‘yes’ to any of these questions, watch “Supercritical CO2 Cycle – Advanced Power Conversion Technology,” which we recorded and put in our resource center! Learn more about technological advantages and most effective solutions in S-CO2 Cycle Turbine design!

During this 1-hour webinar you’ll learn about:

  • Overall S-CO2 Cycle Overview
  • Heat balance simulation in modern software
  • Most common modern turbomachinery design challenges
  • Leveraging AxSTREAM to help you with S-CO2 Cycle design

Who should watch:

  • Engineering managers interested in developing S-CO2 Cycle turbomachinery
  • Mechanical and aerospace engineers working on CO2 Cycle / Super Critical Carbon Dioxide Brayton Cycle and looking for optimization strategies
  • Scientists and developers in the field of alternative energy sources (research and study)
  • Everyone interested in how SoftInWay Inc. and AxSTREAM can help you with advanced Turbomachinery Design

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”

Come home. Book your ticket for the Turbo & Pump Symposia

The 43rd Turbomachinery and 30th Pump Symposia are quickly approaching. The 3-day event will begin on September 22nd in Houston, Texas at the George R. Brown Convention Center. The Symposia are organized in order to promote professional development, technology transfer, peer networking and information exchange among industry professionals. The event serves as a premier training and networking opportunity for professionals in both the turbomachinery and pump industries.

2013 Symposia
Source: Texas A&M Engineering Experiment Station

In ancient Greece, a symposium was a drinking party. Hosted by Socrates and philosophers alike, they were used to celebrate and discuss matters most vital to the universe. The “symposium” was a source of pride for the ancient aristocrats. Continue reading “Come home. Book your ticket for the Turbo & Pump Symposia”