Series on Micro Gas Turbines And How They Can Make the World Greener

If you’re familiar with turbomachinery, then you probably know the pivotal role they play in our lives. If you’re not, no biggie! Have a look at this blog where I discuss a world without turbomachinery. But where do microturbines fit in? I can’t speak for anyone else, but my mind immediately jumps to turbochargers in small-displacement car engines. There is, however, a whole slew of information, history, and applications for microturbines beyond being a component in your car.

The best place to start, is to establish just what a microturbine is and isn’t. Granted the prefix in the word is a dead giveaway, but just how small is a micro gas turbine?  In terms of power output, a micro gas turbine puts out between 25 and 500 kW. The size of these machines varies; some systems can be the size of a refrigerator, while others can fit on your desk. For reference, some of these machines are smaller than your average corgi!

Micro Gas Turbine and Corgi
Figure 1: A micro gas turbine with a pencil for scale (left) and your average corgi (right). Not very aerodynamic, but awfully cute. Source

In terms of components, microturbines typically consist of a compressor, combustor, turbine, alternator, generator, and in most machines, a recuperator. While incorporating a recuperator into a microturbine system comes with its own set of challenges, the benefits are often well worth it as efficiency when recuperated hovers around 25-30% (with a waste heat recovery/cogeneration system, efficiency levels can reach up to 85% though).

Figure 3: A commercial airliner's turbofan engine the common image that is conjured when one thinks of turbines in transportation
Figure 3: A commercial airliner’s turbofan engine; the common image that is conjured when one thinks of turbines in transportation.
History

When and how did the concept of micro gas turbines come about? After the advent of the jet engine in World War II and the prominence of turbochargers being used on piston-driven propeller planes during the war, companies started to see where else gas turbine technology could be utilized. Starting in the 1950’s automotive companies attempted to offer scaled down gas turbines for use in personal cars, and you can read our blog covering that more in-depth here. You can probably guess by the number of gas turbine-powered cars on the road today, that it wasn’t very successful.

Fast forward to the 1970s, companies started to take an interest in micro turbines for stationary power generation on a small, portable scale. Allison developed microturbine-powered generators for the military that showed substantially lower fuel consumption in initial testing. In the 80’s, GRI supported the AES program where they attempted to develop a 50kW turbine for aviation applications, using a heat recovery system to improve efficiency through a cogeneration system. More recently, companies like Capstone have worked with GRI on new projects to introduce microturbines to different industries where they could be useful, using the latest advancements in technology to ensure higher efficiencies and reliability of designs past. To discuss the current state of affairs for microturbines however, it might be good to list some of their present advantages and drawbacks, and then explore where in the world they could be most useful.

Micro Turbine Compressor
Figure 4: A micro turbine compressor model.

 

Advantages and Disadvantages of Microturbines

As with just about any other type of technology, microturbines have their own set of advantages and disadvantages as a result of their design that are seen in their different applications.

Advantages: 

  • – Lower emissions
  • – Lower noise level than comparable reciprocating engines
  • – Fewer moving parts with results in less maintenance needs
  • – Lower vibration levels
  • – Ligherweight, compact systems
  • – Diverse fuel selection (jet fuel, kerosene, diesel, natural gas)

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Disadvantages:

  • – Very low efficiency without recuperator/waste heat recovery system
  • – High work requires high speeds (30-120 krpm) for small diameters
  • – Poor throttle response
  • – Expensive materials required for manufacturing
  • – More sensitive to adverse operating conditions

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A Micro Gas Turbine
Figure 5: A Microturbine
Potential Transportation Industry Applications

There are a number of different industries which microturbines can be found both in and outside of the transportation. Throughout the upcoming months, we’ll be taking a closer look at:

  • – The Aviation Industry
  • – The Automotive Industry
  • – The Marine Industry
  • – The Rail Industry

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Each of these industries has at least one application where micro gas turbine technology has the potential to conserve fuel and lower emissions without compromising power. In the next entry, we’ll look at the current state of the aerospace industry and where/how micro gas turbines can improve upon existing technology.

If you want to learn more about designing a micro gas turbine, or about the tools our engineers and thousands of others around the world rely on for their turbomachinery designs, reach out to us at info@softinway.com

Basic Definitions and Fundamental Concepts of Rotating Equipment Vibrations

Hello and welcome or welcome back to the January 2020 edition of our Rotor Dynamics Blog series! Here are the other entries in the series for those who are just joining us:

  1. Series Preface
  2. What is Rotor Dynamics? And Where is it Found?
  3. Why is Rotor Dynamics so Important?
  4. What API Standards Govern Rotor Dynamics Analysis?

In our previous blogs we established that rotor dynamics is a branch of applied mechanics in mechanical engineering and is concerned with the behavior of all rotating equipment, but let’s have a closer look at some of the factors that affect the behavior of rotating equipment.

Here’s a non-exhaustive list of the different static and dynamic forces and phenomena that can act on a rotor train:

  • – Unbalance
  • – Gravity
  • – Bearing reaction
  • – Inertia
  • – Seals
  • – Fluid-rotor interaction
  • – Impeller aerodynamic loadings
  • – Misaligned couplings and bearings
  • – Rubbing between rotating and stationary components

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Rotor Train Schematic
Rotor Train Schematic

As you can see there’s no shortage of different forces and factors which must be considered to ensure the smooth operation of your turbomachinery and other rotating equipment. While some of these factors are very familiar such as gravity, some factors like rotor unbalance have numerous causes. Here’s another (non-exhaustive) list of different factors that can cause rotor unbalance: Read More

Part Two: A Company Snapshot of 2019 – Looking Back and Looking Forward

Part 1

Software Upgrades:

2019 was a year of innovation and exploration for our engineering team as we worked with our customers to develop capabilities both in and outside the realm of turbomachinery. Our dedicated structural and rotor dynamics engineers worked with some of our AxSTREAM RotorDynamics customers to continually develop capabilities to perform torsional forced response analyses in reciprocating compressors. On the thermal-fluid modeling front, our engineers added capabilities to AxSTREAM NET, enabling it to be used for multiphase flows in heat exchangers, rocket engine nozzles, and refrigeration systems, as well as continued development of capabilities for analyzing secondary flows and leakages from turbomachinery flowpaths.

 

Rocket Nozzle Modeling in AxSTREAM NET
Rocket Nozzle Modeling in AxSTREAM NET (left) and CAD Model (right)

Perhaps one of the biggest buzzwords of the last decade (and for years to come!), SoftInWay’s engineers underwent a project to further streamline the turbomachinery design process leveraging Artificial intelligence (AI). While AxSTREAM ION™ had already made it possible to automate processes in AxSTREAM and enable interaction with external CAD/CAM programs and other commercial/in-house codes, AxSTREAM.AI™ takes it one step further. By utilizing machine learning to iterate designs continually and training the program to recognize feasible and infeasible designs, AxSTREAM.AI™ is able to develop components in just several hours, as opposed to month-long or year-long projects. Read More

A Company Snapshot of 2019 – Looking Back and Looking Forward

Part 2

In what feels like the blink of an eye, 2019 has come to a close (well, almost). In the last decade, we have seen technology make leaps and bounds with advancements in everything from electric vehicles and propulsion, to artificial intelligence, to the microsatellite industry, and supercritical carbon dioxide (sCO2) power cycles. We’ve even seen the rise of the elusive and mysterious impossible burger. For engineers working in the field of technology as well as the SoftInWay team, it has been an exciting year full of new developments and growth; and we’d love to share a recap of our year with you, our readers!

So what has SoftInWay been up too this year?

Liquid Propulsion Systems Seminar:

Earlier in the year, we hosted a liquid rocket engine design/development seminar in Huntsville Alabama, AKA Rocket City USA. We had a good turnout from companies in the area that included Teledyne Brown, ATA Engineering, as well as other businesses large and small that call the Rocket City home. This event allowed us to show off our latest software development in the aerospace industry, AxSTREAM.SPACE, and how quickly and simply an engineer can design a turbopump for a liquid rocket engine as well as design/optimize the cooling channels in the engine’s nozzle, and perform the rotordynamics analyses for the turbopump.

Turbo Expo:

Read More

What API Standards Govern Rotor Dynamics Analysis?

Hello and welcome to this December edition of the Intro to Rotor Dynamics Blog; and if you’re re-reading this, welcome back! Here are the other entries in this series if you want to retrace our steps thus far:

Series Preface

What is Rotor Dynamics? And Where is it Found?

Why is Rotor Dynamics so Important?

So now that we’ve covered the basic definition of rotor dynamics and established the consequences of inaccurate/incomplete analyses, let’s look at what standards govern rotor dynamics.

In general, there are several different codes and standards that rotor dynamics engineers look to in order to make machines compliant. The standard they look at for compliance depends on the location of the company, as well as the kind of machine, what industry the company/machines are present in, and what the machine’s application is.  With so many different applications, there are many different places to consult in order to make a compliant machine.

So, what are the governing bodies on rotor dynamics and vibration analyses as well as the balancing of rotating machines? Well, there are several

  • – First, you have the American Petroleum Institute, commonly known as API.
  • – Next, there’s the International Organization for Standardization, known as ISO.
  • – There’s also ANSI, the American National Standards Institute.
  • – Lastly, each company may have internal rules and standards, with their own calculations and tests that are more stringent than the requirements put forth by the other governing bodies.

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So where would you find the rules relating to rotor dynamics in the API’s and the ISO’s long lists of standards and regulations? I’m glad you asked.

Governing Bodies for Rotordynamics

API Standards

Read More

Why is Rotor Dynamics so Important?

[:en]Welcome back for the 3rd installment of our introduction to rotor dynamics! If this is your first time having a look at this series, hello! Feel free to have a look at the previous installments if you want to play catch-up or get a refresher.

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Otherwise, let’s get into a question I’m sure a few of you have been asking. Why is rotor dynamics analysis so important?

Steam Turbine View and Train Lateral Model
Steam Turbine View and Train Lateral Model in AxSTREAM RotorDynamics

Let’s start with a basic premise. As we’ve previously established, rotor dynamics is the behavior of rotating equipment and the analyses of said behavior. Rotating equipment tends to be very expensive to design, develop, and manufacture, so from a financial standpoint, it is prudent to ensure that the behavior of the equipment as it operates does not jeopardize itself or any other. A machine like an aero engine cost hundreds of thousands or even millions of dollars for a team to design, analyze and refine the flowpath, therefore, an analysis which costs a fraction of that money and also ensures the rotor-train is properly supported is a prudent use of time and engineering resources. Read More

A World Without Turbomachinery

[:en]In just about every corner of the globe, machines are used and needed for the modern world and its people to function in normal everyday life. But what if these machines were to just…disappear? How badly would it disrupt modern society? Our young protagonist is about to find himself in the midst of such a scenario as he comes to realize he’s taken residence in an apartment building located inside a little neighborhood known as…the twilight zone.  

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I open my eyes slowly and rejoin the world, in all of its silence. Hold on, it’s Thursday, the alarm was supposed to wake me up! I roll over to check the time, and the screen is just a blank, black façade. That’s odd. The alarm clock isn’t working. The fan isn’t on either. The power must be out. What could have happened to shut off the power? Read More

What is Rotor Dynamics? And Where is it Found?

Welcome to this next edition of our “Introduction to Rotor Dynamics” series! In this edition we’ll be covering the definitions of rotor dynamics, and how it is an important factor in the lifetime of a rotating machine. So, for starters, what is rotor dynamics?

Well, if you read our preface which can be found here, you probably knew the answer already; or if you’ve been working in this field, you probably also have a good answer. For those of you new to rotor dynamics, however, it’s a branch of applied mechanics in mechanical engineering and is concerned with the behavior of all rotating equipment; considering phenomena like vibration, resonances, stability, and balancing. It accounts for many effects: from bearings, seals, supports, loads and other components that can act on the rotating system.

Is rotor dynamics vibration analysis?

Yes partially, but there is much more that needs to be considered as you can guess from the above definition. Vibration analysis simply isn’t enough, because the rotors in these machines spin at such high RPMs and are so heavily loaded. Something as simple as the bearing’s position and stiffness, or a slight asymmetry from blade creep can affect a rotor’s behavior.

Where can rotor dynamics be found and analyzed?

The short answer is, there are numerous machines where rotor dynamics can be considered.  In fact, it’s probably easier to list the numerous applications where rotor dynamics doesn’t exist.

A 3D model of a gas turbine rotor train
Figure 1: A 3D Model of a Gas Turbine Rotor Train.

Below is a very short list of some examples where rotor dynamics can be considered: Read More

New Series on Rotordynamics: Preface

Welcome to our latest blog series on rotor dynamics! In this series we’ll be covering fundamentals and a general overview of the engineering discipline that is rotor dynamics, including some basic definitions, why it’s important, the different calculations, and the overall objectives and purposes for these calculations.

Axial Compressor Rotor

In the months ahead, you can expect to learn more about: Read More