Hello! Welcome to this edition of our series on micro turbines! Today we’ll be covering micro turbines and the roles they play in the automotive world.
“Big wheels keep on turnin’…”
Now here’s the real question, when you see that lyric which song do you think of first? Having gotten that stuck in everyone’s head, let’s get on with today’s topic: micro turbines in cars.
I mentioned in the intro to the series that when I think of micro turbines my mind immediately jumps to turbochargers like those used in reciprocating engines seen in cars, trucks, boats, and small airplanes.
They are, in essence, the same, but also different. For example, a turbocharger uses exhaust gas from a reciprocating engine to drive a compressor to pull more air into the engine, while a micro turbine drives a compressor to pull air into a combustor and then also drives a generator to create electric power.
Hello and welcome to the next entry in our series on micro gas turbines! If you’re new to this series, be sure to check out our earlier blog where we: introduce the concept of the micro gas turbine; look into the history of it; and discuss some advantages and disadvantages that come with this technology.
This time, we’ll be looking at micro gas turbines in the Aviation industry (if you couldn’t guess by the title). Believe it or not, the concept and configuration of a micro gas turbine has been present in this industry for decades. We’ll get into that in a minute.
Gas turbines are certainly no stranger to the aviation industry. As a matter of fact, when many of us hear the term “gas turbine” we immediately jump to the image of a jet engine powering a massive airliner carrying us to our next adventure.
Yes, these mighty turbines are indeed a staple in the aerospace industry. But did you know that micro gas turbines are also making a rise in this industry?
Although micro gas turbines first made an appearance as an alternative to traditional piston engines in the automotive industry, they have actually been present in the aviation industry for some time.
Hello and welcome to the latest revolution in our series on rotor dynamics and bearing analysis. This month, we’ll be looking at what steps need to be taken to accurately model a rotor train, from the components on the rotors themselves to the bearings and structural components that support the entire machine. If you haven’t had a look at the other entries in this series, you can find them here: Series Preface
So what is the importance of accurately modeling a rotor-bearing system? Well we already know that an inaccurate analysis can have catastrophic consequences… If you want to know more about why, I also suggest looking at entry 2, titled “Why is Rotor Dynamics so Important?”.
While we at SoftInWay are known for helpful articles about designing various machines and answering questions about the pros and cons of retrofitting your turbomachinery and powerplants, we believe it is important to also examine the lives of some of the men and women behind these great machines that do so much for the world.
The jet engine is one of the greatest inventions of the last 100 years. It has made transcontinental travel considerably shorter. A trip that might take days on a piston driven aircraft was cut down to hours thanks to the inception of the jet engine. To this day, millions of people rely on jet engines daily for everything from themselves for vacation travel to their packages for shipping goods overnight. These engines also give the U.S. military the ability to deploy to any part of the world within 18 hours.
But who invented the jet engine? This credit changes depending on who you ask. Some might answer t was Hans von Ohain. To- others, this credit belongs to Sir Frank Whittle, OM, KBE, CB, FRS, FRAeS, RAF.
Why the discrepancy? von Ohain is known for creating the world’s first operational jet engine, and Whittle is credited with developing the turbojet earlier. While von Ohain’s first engine was the first to fly operationally in 1939, Sir Frank Whittle had been working on his design since the 1920’s. Today, we’d like to look at the life of Sir Frank Whittle, and how he created this world-changing machine. Read More
Hello and welcome to the next edition in our introductory series to rotor dynamics analysis. In this installment, we’ll be looking at the specific purposes and objectives of performing rotor dynamics analyses; as well as the differences between lateral and torsional analysis. If you haven’t read the other entries in this series, you can find them here:
In earlier posts, we’ve established what the basic definitions and concepts are; shown the consequences of improperly performing rotor dynamics analyses; as well as what standards are in place to ensure these breakdowns and catastrophes are avoided. That raises the question, what exactly are we trying to do by performing rotor dynamics analyses?
We know based on our previous articles we are trying to determine the critical speed and in turn determine if further damping and other measures need to be taken to ensure that there is a proper separation margin between the operating speed of the machine and its critical speeds. But what will this accomplish? The answer is actually 3 answers!
We want to minimize and/or eliminate unplanned failures as much as possible, especially when these machines are counted on to keep planes in the air, the lights on, and in some cases, people alive! Have a look at this article from Halloween if you want an idea of what would happen if all our turbomachinery just stopped working.
Secondly, we want a low vibration level. In addition to providing comfort in the case of an aero engine or a car’s turbocharger, lower vibration levels ensures less undue wear and tear on expensive rotor train components.
Lastly, and this correlates with the others, ensure low maintenance requirements. Naturally the machine that can do its job the longest will be the one people desire, and rotor dynamics analyses play a large role when it comes to maximizing the service intervals for turbomachinery.
Overall, the purpose of rotor dynamics analyses, is to ensure maximize machine reliability in the interest of time, money, and most importantly, safety. Now let’s get into the differences between lateral and torsional rotor dynamics.
Rotor dynamics is typically split into two distinct kinds of analyses which are constantly brought up; lateral and torsional rotor dynamics. So, what is the difference between the two?
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!
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).
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.
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.
– 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)
– 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
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
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 firstname.lastname@example.org
In our previous blogs we established that rotor dynamicsis 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:
– Bearing reaction
– Fluid-rotor interaction
– Impeller aerodynamic loadings
– Misaligned couplings and bearings
– Rubbing between rotating and stationary components
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
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.
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
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.
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:
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.
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.