Performance Effects of Axial Turbines & Compressors Due to Roughness Variations

As turbomachinery technology continues to advance in efficiency as well as overall power, many engineers want an estimate on how long these manufactured machines will operate.  Specifically, in high-temperature and high-flow turbomachinery applications, one of the main sources of performance degradation can be attributed to increases in surface roughness.  Gas turbine and compressor blades in particular experience a substantial amount of surface degradation over their lifetime.

gas turbine blade
Figure 1 – Gas Turbine Blade and Annulus Surface Wear (Source PowerMag)

There are many mechanisms that contribute to surface degradation in airfoils and annulus surfaces.  Foreign particles adhering to the material surface (or fouling) is generally caused by any increase in contaminants such as oils, salts, carbon, and dirt in the airflow.  Corrosion occurs when there is a chemical reaction between the material surface and the environment that causes further imperfections on the machine surfaces.  Additional mechanical factors such as erosion and abrasion will play a part in a machine’s surface degradation as well.

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Discussion – Alien Signal or Radio Noise: Leveraging Turbomachinery

The Internet practically exploded early yesterday morning with talk of an extraterrestrial discovery after a signal was detected by a Russian telescope. The star in question, HD 164595 located a vast 95 light years away, sent out a strong radio spike that was picked up and sparked a boom of excitement. According to an article published by National Geographic, however, this signal may not be what it was first interpreted as.

Astronomers have pointed their radio telescopes towards the stars for over half a century, hoping to catch a glimmer of life beyond this planet. Short of a futuristic rocket ship, these telescopes seem to be the best bet for catching a peak of something out of this world. That is a main causStarse as to why this discovery is so tantalizing to both scientists and the rest of us earthlings. However, after further investigation, neither the Allen Telescope Array, commanded by the SETI (the Search for Extra-Terrestrial Intelligence) Institute, nor the Green Bank Telescope, used by the Breakthrough Listen project, turned up additional signals or observations.

Another issue that has risen according to this article is that the signal did not repeat and could have been caused by something else. A source on Earth, such as a faulty power supply, military transmission, or arcing electrical fence for example. Another possible explanation could be that gravity from another object in space amplified a weaker signal. That being said, it would appear that HD 164595 is similar in many ways to our sun. It is composed of the same ingredients, is approximately the same age and has at least one planet in its orbit. This would suggest that theoretically, it would be plausible for life to exist within this system.

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Rotor Dynamics – Importance of Fundamental Understanding & Software tools

Rotor and bearings are the most critical components of any rotating machinery. Rotor lifetime and reliability depend, first of all, on the level of rotor vibrations. In order to meet highest requirements of reliability each step of the rotor design should be based on accurate Rotor Dynamics prediction.

Rotor dynamics is the branch of engineering that studies the lateral and torsional vibrations of rotating shafts, with the objective of predicting the rotor excessive vibrations. Rotor Dynamics is different from structural vibrations analysis because of gyroscopic moments, cross-coupled forces, critical speeds, whirling effect, etc. These difference makers are all due to the rotation of the rotor assembly.


Understanding of basic rotor dynamics phenomena and the various types of problems is absolutely mandatory when designing and developing rotor-bearing systems for various applications. Fundamental approach for Rotor Dynamics analysis generally is based on the following steps:

  1.  Predict critical speeds.
  2. Determine design modifications to change critical speeds.
  3. Predict natural frequencies of torsional vibration.
  4. Predict amplitudes of synchronous vibration caused by rotor unbalance.
  5. Predict threshold speeds and vibration frequencies for dynamic instability.
  6. Determine design modifications to avoid dynamic instabilities.
  7. Calculate balance correction masses and locations from measured vibration data.

Another factor that determines accuracy of Rotor Dynamics calculation is rotor system simplification and the adequate modelling for rotor parts such as Impeller/disks, Sleeves, Balance pistons, Seals, Thrust collars, Couplings, Addition of Stiffening Due to Shrink Fits and Irregular Sections etc. (more…)

Product Development: Rescale existing turbomachine design vs full design process

When deciding on a new product line, manufacturers of turbomachines and their engineering teams must often decide whether to rescale a product that they already manufacture or to begin a full design process for a completely new machine. For example, a producer of 5 MW axial turbines wants to start manufacturing 10 MW turbines, does it make sense to create a brand new design from scratch or to simply scale up the 5 MW turbine they already produce to a similar 10 MW version? To answer this question, many considerations have to be taken into account, the general answer however is, that it is almost always a better idea to start a new design.

Improved Design Technology

Many manufacturers wrongly believe that by simply scaling their current product that they will save not only on design costs, but that they can leverage their existing manufacturing capabilities to stamp out a similar product. What is not factored in however is the progress of design technology and theory since their original machine was first conceptualized. The result from a simple scaling process will simply be a less optimized and efficient machine for any use as compared to a new configuration using the latest in design software. Increasing software sophistication and computing power are constantly pushing the boundaries of efficiency while minimizing operating costs. Simply put, your competitors will have designed a superior product compared to yours.


        AxSTREAM 3D Blade Design Software

Improved Materials

When was your current machine designed? Many older machines were created using materials that by today’s standards are simply not capable of operating at the extreme conditions  (mostly temperatures) required today to attain the energy efficiency requirements set up by ever increasing regulations. Depending on materials used, the optimal blading structure, bearings, etc. geometries would be significantly unique. If one were to simply scale up their current product, they would either be using old materials or have inefficiently designed machine components for a different material. In either case, their scaled machine will be inferior to a configuration that was conceptualized and optimized from scratch.

Scaling Factors

Another very significant aspect of machine resizing is that it is not a straight forward process; if you want to double your power generation in a turbine for example you are not going to be doubling the blade size or mean diameter, for example, even when considering the same boundary conditions (inlet pressure and temperature, as well as, outlet pressure, rotation speed, and so on). For each specific set of conditions, fluid, rotation speed, mass flow rate, etc. a unique flow occurs inside the different blades. Changing one parameter will lead to changes in the flow and therefore result in inefficiencies, as it is what happens in off-design conditions (the machine is not operating at its maximum performance). This is why flow similarity parameters become relevant.

Machine Purpose and Type

One of the obvious questions to ask is, what is the purpose of my new machine and how much larger (or smaller) will I need it to be? If the new machine is intended for use with a completely different fluid, a new design will be optimal as different fluids interact in unique ways with varied rotor and stator configurations.

The machine type that you are considering is also critical to the decision. Different turbomachines do not scale in similar fashion with increase in size. For instance, radial turbines are usually not as efficient as axial turbines when one starts to approach the 2 MW range. In this instance the ideal solution is for a complete redesign since a smaller scale version that the manufacturer may have had would not be configured to operate at higher power ranges efficiently.


Turbocharger Design and Industry Usage Discussion

An opportunity to discuss turbocharger usage and design with Softinway engineer Ursula Shannon in a question and answer format:

What are some of the major current turbocharger design challenges?

When it comes to turbocharger design, there are two challenges that engineers generally face. “Turbo lag” and turbo boost power at varying engine RPMs. “Turbo lag” is the time that it takes for the engine to produce enough exhaust to start the turbocharger “working”. This can vary greatly depending on engine size, turbocharger geometry, exhaust output etc. Ideally, engineers want to reduce this “Turbo lag” by as much as possible in any given situation, as during that time, the exhaust is “wasted” in a sense. Finding the most efficient configuration with all of the parameters in mind can be a very challenging scenario from a design perspective.

The turbo boost design challenge is one of efficiency at variable exhaust outputs. A smaller charger for example will start to boost at lower engine speeds while a larger one will start to boost at engine speeds. The trade off however is that a smaller turbo will start to create what is known as back pressure at higher speeds, and this results in a loss of potential power. A larger turbocharger, will be able to create more overall boost at higher speeds, however the “Turbo Lag” is more pronounced as more engine exhaust is required. Minimizing these trade offs is another key challenge in turbocharger design.

Finally, the process of turbocharger design process itself is complex, and requires highly specialized software such as our own here in Softinway (AxSTREAM).

Turbocharger blog 3

AxSTREAM Turbocharger Design Software ( Flowpath Design and Optimization )

turbocharger blog 2

AxSTREAM Turbocharger Design Software (Compressor 1D Design and Analysis)

What are some design changes do you see coming to turbochargers in the future?

As I mentioned some of the challenges engineers face in turbocharger design, currently many technologies and methods are being developed to alleviate some of the issues faced.

Two stage turbochargers are good example of trying to offer a solution to the boost powers at varying engine outputs, using a smaller turbocharger that operates at low RPMs and a larger turbocharger that operates at higher RPMs.

Electronic energy storage setups are currently being developed and used in European race cars which uses the output side of the turbocharger as a sort of generator which stores energy in a battery from turbocharger operations and acts as a boost during a turbocharger’s lag period.


Improving Turbine and Compressor Design Matching

Compressor-Turbine-MatchingOne of the most prominent steps of complete gas turbine design is turbine-compressor matching. There are three major components to a gas turbine: compressor, combustor, and turbine. Although all of the components are designed individually, each of the components needs to correspond within the same operating condition range since all are integrated into one cycle. Consequently, an optimal design of each component must fit the requirement of other component’s optimal parameters. Corresponding operating points for each component must be found at equilibrium with the engine, thus the overall performance of gas turbine can be reached within the defined range of parameters.

The idea behind component “matching” process is to find flow and work compatibility between corresponding components. Based on the mechanical constraints, gas generator speed and firing temperature of a gas turbine have limitations depending on: ambient temperature, accessory load and engine geometry. The match temperature chosen should be the ambient temperature which reach both upper limits at the same time.  Pressure ratio needed to allow a certain gas flow is also one of the most prominent parameters that has to be taken into consideration. Designers need to make sure that the gas flow through the power turbine from gas generator satisfy the pressure ratio needed for compressor power requirements. Gas generator can easily show an altered match temperature due to some conditions i.e: reduction in compressor efficiency (due to fouling, etc), change of thermodynamic properties of combustion product, gas fuel with lower or higher hearing value, etc. Match parameters of an engine could also be altered by changing the flow characteristics on the first turbine nozzle.Turbine-Compressor

Using characteristic map/curve as well as thermodynamic relationships of turbine and compressor, calculations can be performed to identify the permitted operating range. It must be taken into consideration that all calculated value must match the value from map data.

Trying to find the fastest solution for this step? SoftInWay’s turbine-compressor matching feature in AxSTREAM could help you cut engineering time and simplify the process. Combining performance maps of turbine and compressor, making it easier for the user to determine points of joints operations.

Take a look into AxSTREAM’s to learn more about this.

Turbine Compressor Matching Compatibility Mode Document

The Economic Optimization of Renewable Energy

Global warming has been a very popular topic these days. With up-trend of clean technology and realization that strict climate policy should be implemented, demand of renewable energy sky-rocketed as conservative plants popularity falls. Number of coal power plants have significantly dropped since its peak era, being known as the largest pollutant contributor as it produces nitrogen oxide and carbon dioxide, the technology is valued less due to its impact on nature. Renewable energy comes from many sources: hydropower, wind power, geothermal energy, bio energy and many more. The ability to replenish and having no limit in usage and applications make renewable energy implementations seems attractive. Aside from that, they also produce low emission, sounds like a win-win solution for everyone. Theoretically, with the usage of renewable energy, human-kind should be able to meet their energy need with minimal environmental damage. With growth rate ranging from 10% to 60% annually, renewable energy are getting cheaper through the technology improvements as well as market competition. In the end, the main goal is still to generate profit, though these days taking impact on nature into the equation is just as important. Since the technology is relatively new, capital cost still considerable higher compared to some cases with more traditional (–and naturally harmful) implementations. So the question is: how to maximize the economic potential of a renewable energy power generation plant?

The Economic Optimization of Renewable Energy

Living up to the maximum potential of any power generation plant starts in the design process. Few examples for solar power plant: designers should take into consideration type and quality of panels, it’s important to see the economic-efficiency tradeoff before jumping into investment; looking into the power conversion is also one of the most important steps, one should take into consideration that it would be worthless to produce more energy than the capacity that are able to be transferred and put to use, though too low energy generation would mean less gross income.

Another example, for a geothermal power plant, many studies have shown that boundary conditions on each components play a big role in determining the plant’s capacity and efficiency. High efficiency is definitely desired to optimize the potential of a power plant and minimized the energy loss. Though, should also be compared to the economic sacrifice; regardless of how good the technology is, if it doesn’t make any economic profit, it would not make sense for one to invest in such technology. Low capital cost but high operating expenses would hurt the economic feasibility in the long run, whereas high capital cost and low operating expense could still be risky since that would mean a higher lump sum of investment upfront, which might or may not breakeven nor profitable depending on the fluctuation of energy market.

Modern technology allows investors and the engineering team to make this prediction based on models developed by the experts. SoftInWay just recently launched our economic module, check out AxCYCLE to optimize your power plant!


[1] Optimal design of geothermal power plants 

[2] Strategies in tower solar power plant optimization

Variable Speed Compressor for HVAC and Refrigeration.

Even though energy consumption for HVAC and refrigeration system is considerably smaller than most technology applications, energy savings is still desired for many reasons: cleaner technology, saving cost, fuel economy and many more. Improvements in insulation, compressor efficiency and optimization of the cycle can be implemented to achieve better performance. Installation of variable speed drives is one way to optimize the potential of HVAC system.


Although has been implemented to various HVAC components, variable-speed drive is considerably still one of the “newer” advancements in the compressor industry. These devices are able to precisely control the motor speed and trim/balance systems. Variable speed control compressor gives end-users the comfort of matching the speed to what is needed at the time; giving precise temperature control with less cycling and longer run times. With longer run times, the technology also helps to remove moisture and relative humidity during the summer; or on the other hand during the winter by increasing the speed of compressor, system are able to deliver hotter air.

Compared to fixed compressor, where there are only two options for end-users to set: maximum capacity or completely off; variable speed drives gives the end-user an ability to adjust power output to compressor. The technology also comes with the benefit of less energy wasted from off and on cycle, precise load matching and low amp gradual compressor motor startup; therefore, improving the efficiency on certain conditions.


Coupling variable speed drives to centrifugal compressor alter the behavior of the component. Although, not always requiring smaller energy (i.e at or near full load) compared to fixed speed compressor, installation of VSD could really benefit the users in terms of power consumption (i.e at part lift), to optimize even further implementation of both compressor types would benefit both conditions.

Want to learn more? Design your most efficient compressor using AxSTREAM


Variable Speed Air Compressor

Reduction In Power Consumption Of Household Refrigerators By Using Variable Speed Compressors

The Impact of Variable-Speed Drives on HVAC Components

Heat pump and refrigeration cycle


Turbo pump design parameters for Liquid Propulsion

turbo3aLiquid propellant rocket is known as the most common traditional rocket design. Although the first design was launched back in 1926, liquid propellant rocket remains a popular technology which space exploration companies and institutions study for further improvement.

The implementation of this particular technology is based on a simple idea: fuel and oxidizer are fed through a combustion chamber where both liquids will met and burned to produce launching energy. In order to inject propellant to combustion chamber, a turbo-pump is used to create required pressure . The turbo-pump design and operating parameters contribute to the optimization of both turbo-pump and engine system performance. The pump needs to be designed to avoid cavitation while operates pushing the liquid to combustion chamber.

There are three different cycles which are often used in liquid propellant rocket: the staged combustion, expander and gas generator cycle. Configuration of the turbo-pump strongly relies on the cycle and engine requirements –thus the best design must be selected from options available for the particular cycle’s optimal parameters. For example for staged combustion cycle, where turbine flows is in series with thrust chamber, the application allows high power turbo-pumps; which means high expansion ratio nozzles can be used at low altitude for better performance. Whereas, for implementation of gas-generator cycle, turbine flows are linked in parallel to thrust chamber, consequently, gas generator cycle turbine does not have to work the injection process from exhaust to combustion chamber, thus simplified the design and allows lighter weight to be implemented.

Some parameters are interdependent when it comes to designing a turbo-pump, i.e: turbo-pump cycle efficiency, pump specific needs, pump efficiencies, NPSH, overall performance, etc. Often in practice, pump characteristics will determine the maximum shaft speed at which a unit can operate. Once it’s determined turbine type, arrangements, and else can be selected. Another thing that must be taken into consideration while designing a turbo-pump is how it affect the overall payloads.

Schematic of a pump-fed liquid rocket
Schematic of a pump-fed liquid rocket

Turbo-pump design affect payload in different ways:

  1. Component weight
  2. Inlet suction pressure. As suction pressure goes up, the tank and pressurization system weight increased and reduce the payload.
  3. Gas flowrate, since increase in flowrate decrease the allowable-stage burnout weight, which would decrease payload weight.

All those has to be taken into consideration while trying to select an optimal design of turbo-pump, since it crucially affects overall performance of the engine.

Want to learn more how to design a turbo-pump? Check out AxSTREAM as your design, analysis and optimization tool!


Turbopumps for Liquid Rocket Engines
Design of Liquid-Propellant Rocket Engines
Principal of Operation – Liquid-propellant rocket
Staged combustion cycle
Gas-generator cycle


Re-inventing the wheel (or perhaps our education system)?

I hope everyone is having a great week. I wanted to write about our education system, as it relates to Turbomachinery, and perhaps some challenges that educators / students face, and some ideas for how things can be improved.

As computation technologies have evolved over the last 30-40 years, it seems that a large number of education institutions are still behind.

Part of my job at SoftInWay, is to make sure that local  & global Universities involved in Turbomachinery have the most advanced software tools, so that the students graduating from undergraduate, as well as Masters and PhD level programs, have some kind of relevant skills to develop / optimize Turbomachinery, as well as know how to use relevant software tools.

From talking to Academia from different countries, it seems that professors (perhaps due to bureaucracy of their positions) are often faced with several challenges / decisions:

1. No budget for software tools thus forced to use free tools

2. Desire to create their own software, to eventually spin off and start a company

3. Lack of deep technical program, thus only picking macro topics as they relate to turbomachinery as general thermodynamics, etc. (which is important also).

What’s the problem with all of these approaches: When students graduate, and want to go into the field of Turbomachinery, a large portion of these students think that “Turbomachinery Design” can be done with CFD.

Looking at the last 5-10 years of CFD as it relates to Turbomachinery, people have been in several “camps”, with the most known names (such as products from Ansys, or CD Adapco (now owned by Siemens), Numeca, and some free open source CFD codes.  Additionally, there has been a plethora of free or academic codes written by 100s of wide-eyed graduates students in hoping of making the next big software company.

Why does this cripple the education system, industry and the general concept of innovation? First of all, in all of these packages, you are going on the assumption that you already have a geometry of the turbomachinery and generally know what the machine looks like. Granted, some advertise that by “partnering” with other vendors they can do 1D or inverse design, when looking at these options closely, they are still very weak.   At the same time, there are lessor known CFD packages (from example our Turbomachinery specific CFD module AxCFD that we offer) that while hasn’t been aggressively marketed, comes at 30% of the cost, and has not only faster computation speed, but is fully integrated in a complete turbomachinery design platform. While this is a great option for students, very few know about it, and we are always stuck with a thought “people need to understand the complete process of design, not just CFD, so let’s focus on teaching that, and sharing that message”.

In addition to working with Universities, another part of my job at SoftInWay is hiring, so what have i learned from looking at 1000s of resumes from masters and PhD students?

If you start to dig deeply, about what candidates have learned about turbomachinery design, how well do they understand, for example, compressor aerodynamics, or gas turbine cooling, quite often the answers come up short. This creates a steep learning curve, not just for our company, but also for major manufacturers and service providers.

We believe, that instead of the next generation of students, trying to re-invent the wheel, and spend their 2,3,4,5,6 years of education  on equations and writing code, for a problem that has been solved, they should use a holistic approach, to advance, Power Generation, Transportation, Propulsion and Advance the clean energy space.

We have created a range of free resources for students in an online university format ( and encourage everyone to dig deeply, and together we can create a greener world, for the future generations.

Additionally, our turbomachinery development platform AxSTREAM (r), is the only platform in the world which is wholly integrated and developed in-house, including thermodynamic cycle design, 1D,2D,3D turbomachinery design, analysis and optimization, rotor dynamics and bearing design, stress analysis, advanced optimization and visualization, etc.

** Feel free to fact check this by looking at your current software simulation tools, and see how many modules or features or “tools” are borrowed from other companies.  How can one ever learn and understand how things work and talk to each other, if knowledge is not developed, but rather borrowed.

If  you are a student, or a professor at a college or university, and are interested in improving your turbomachinery program, and giving your students the extra skills (fundamentals and software), to really develop innovations, please write me a message !

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