Papers from the Space Propulsion Conference in Seville (May-2018)

As in previous editions, the 2018 Space Propulsion Conference held in Seville (Spain) last May was once again a meeting place for users of EcosimPro/ESPSS. The customary user workshop was held as usual to present new features and upcoming developments as well as to gather suggestions from users. The technical sessions included several papers based on using ESPSS, showing its usefulness and confirming the users’ ongoing interest in this software. Examples of the papers given include the following: design of a round-trip mission to the moon with a hybrid propulsion rocket (DLR), research into two-phase cryogenic flows and their application to liquid propulsion rockets (Ariane Group), the passivation of helium remaining in orbiting satellite propulsion systems (OHB), implementation of a two-phase pipe in ESPSS (VKI), and the development of an innovative system for regulating xenon for electrical propulsion (Air Liquide). The articles mentioned here along with many other papers on space propulsion are available in the “Papers” section of this website.

Modelling the integration of axial turbomachinery in the engine performance with PROOSIS

Available the presentation related to the ASME TURBO 2018 GT2018-76494 paper: Direct Integration of Axial Turbomachinery Preliminary Aerodynamic Design Calculations in Engine Performance Component Models. The authors are I. Kolias, A. Alexiou, N. Aretakis, K. Mathioudakis from the Laboratory of Thermal Turbomachines of the National Technical University of Athens, Greece.

More aeronautics papers and presentations in the Papers area.

Visit us at the ASME 2018 TURBO EXPO in Oslo, Norway, from June 12-14 (Booth #719)

The ASME 2018 TURBO EXPO will be held in Oslo, Norway on June 12, 13 and 14. We will be exhibiting in Booth 719 of exhibition space all three days.

We will be presenting our product PROOSIS (Propulsion Object Oriented Simulation System) along with its toolkits for modelling gas turbine performance. We will also be presenting toolkits for modelling other aircraft systems, like the ECS, fuel system, etc. Today, PROOSIS is used by world leaders in the field to design new engines and perform numerous design, validation and health monitoring studies, among others.

We invite you to make an appointment to talk with us at the expo and enjoy a demonstration of how these products work. You can setup a meeting by email at:

Visual library documentation

EcosimPro/PROOSIS can generate automatic library documentation, so in this blog we’ll show the various different views we can have of the components. The library we’ll use is TURBOJET from the STANDARD workspace. We can generate automatic documentation from this library if we choose the library and the option: “Documentation->Generate Documentation”, which opens a browser with the following header:

Visual library documentation

From here we can browse through the different components, ports, classes, functions, enumeratives and global variables in the TURBOJET library. Let’s take a closer look at what’s under the Components heading. If we click on Components, it takes us to another page with this header:

Visual library documentation

It gives us three different views to see the components: one in alphabetical order, another with a inheritance tree in text mode and the last with the inheritance tree in graph mode. In the first we see a table with each component, its icon and a description:

Visual library documentation

If we click on the [+] sign it takes us directly to the source code for this component (only if available). If we choose the “Inheritance Tree” option, we see:

Visual library documentation

in which we see the inheritance hierarchy among components. For example, GasChannel is inherited from GasInGasOut and Afterburner is in turn inherited from GasChannel. If we want to see this information in graph mode, we can choose the “Inheritance Graph” view, which displays a graph like this:

Visual library documentation

Each bubble represents a component. When a bubble has an arrow pointing to another bubble, it means it is Inherited from that component. For example, we see that GasChannel points to GasInGasOut, indicating that the former is inherited from the latter, and so on  for the rest of the components. It’s a useful view because it shows us all the inheritance relationships of all the components in the library at a glance.

Moreover, the user can interact with the graph by moving the bubbles around with the mouse into new arrangements; when one bubble is moved, the others move automatically to make way for it. We recommend users to reach this view and “play” with this high-level overview of the library.

Improved File Comparing

EcosimPro and PROOSIS have joined file comparing options to make it easier to spot differences between results from simulations, experiments, partitions, etc. This change shows the comparison options in the context menu of the different elements in the “Files” tab and the “Items” tab:

Comparing Tools

When comparing files, EcosimPro and PROOSIS try to make the best comparison they know in terms of the file type. In other words, they compare files as if they were text, unless they are post-process files with an h5 extension (HDF5 format) in which they make a detailed binary comparison:

Comparing Tools

The binary comparison of post-process files is useful for analyzing the differences between the results from two simulations by comparing each communication interval (CINT) or each step in integration (STEP). It is a powerful, flexible comparison that shows exactly what happened.

Moreover, instead of detecting the best comparison, file comparing can be done to make a graphic comparison of the post-process files or to force a text comparison of the chosen files. The next dialog shows the files that hang from the elements to be compared to choose which files to compare by selecting on from the left side, another from the right, and how to compare them by dropping down the options from the “Compare” button:

Comparing Tools

If two post-process files are compared on the monitor, it makes a graphic comparison of any variables that exist in both files and both have the same type, such as shown in the screen shot below:

Comparing Tools

Release of Service Pack for EcosimPro 5.10.2 and PROOSIS 3.10.2

A new Service Pack has just been released for our products EcosimPro and PROOSIS to solve bugs detected by users. In all, more than 70 glitches in the bugs database have been corrected, in areas like:
– Schematics editor
– Generation of S-Functions in Simulink
– Partitions
– Automatic tester
– Deck generation
– Etc.
We strongly recommend to install this new version to get the best user experience and performance.

All users with active maintenance contracts will receive an email containing instructions on how to download the new release. If for some reason you don’t receive one, please contact us

New equations solvers

EcosimPro and PROOSIS are in constant development and take special care that their numerical solvers work as efficiently and robustly as possible. The latest versions of EcosimPro and PROOSIS include several performance enhancements, one of which is the linear equations solver. The graph  below shows that the new linear box solver is up to 50% faster than in previous versions while maintaining the same numerical results. Of course, not all the model has linear boxes, and depending on the number and size of linear boxes, the influence of this improvement will be more noticeable in some cases than others in cutting down on simulation time. Electrical models usually benefit the most from this improvement.

Figure 1 Linear box solver performance (higher is better):

Linear box solver performance

In addition to the improved linear box solver, there are improvements to how memory is managed in the CVODE and IDAS solvers included in EcosimPro and PROOSIS as well as optimizing the Jacobian calculation during the solving process, leading to substantial improvements in some simulations.

Figure 2 Performance of the Priming_complex ESPSS experiment using IDAS and CVODE. EcosimPro 5.6.1 vs EcosimPro 5.10.0 (Lower relative values are better):

Performance of the Priming_complex ESPSS experiment using IDAS and CVODE

EcosimPro and PROOSIS have not only improved the existing solvers, but have also added the following to give the user even more flexibility when simulating:

  • RK45: ODE solver, explicit, variable-step, equivalent to Matlab’s ode45. It converges faster than RK4.
  • BACKEULER: ODE solver, implicit and fixed-step. Useful to solve “stiff” problems in situations needing a fixed step.
  • BACKEULER_SPARSE: ODE solver, implicit and fixed-step. Useful to solve “stiff” problems in situations needing a fixed step. This solver is more efficient than BACKEULER and is meant to make use of the structure of the model by reducing the number of times the waste function is called.

New attribute editor

One of the main new features in the new version of EcosimPro 5.10 and PROOSIS 3.10 is the new Attribute Editor included in the schematic diagrams. This new tool replaces the old attribute editor and gives the end user much more flexibility and speed in handling data on the components, since it now works much like the standards followed by modern spreadsheets.

Fig. A view of the new editor:

A view of the new editor

Listing all the features of the new editor is a task that involves detail, so here we’ll focus on the three main ones:

  • The ability to view one or more editors at the same time
  • Non-blocking editors that can work in the diagram or in the application.
  • Editing multiple components of multiple types

So, with the new EcosimPro/PROOSIS, you can work with several editors open at once, including in different schematic diagrams. The end user can easily compare data, copy them from one editor to another, export them, and all while performing operations such as compiling a schematic diagram, editing a symbol, or launching the monitor to simulate an experiment.

Fig. Multiple editors in the same schematic diagram:

Multiple editors in the same schematic diagram

However, the main feature of the new editor is the ability to manage different components of the same schematic diagram all in one single table. In other words, users can choose whatever components they want and edit all of them at the same time. The system automatically manages the information and groups the data by name, type and unit. The end result is a spreadsheet that makes it easy to find, compare, and edit the values of dozens of components.

Fig. Multiple components in one single editor:

Multiple components in one single editor

And all with multiple aids in editing and filtering the data to make it easier and quicker to find variables based on their category, value, component type, name, etc.

Attribute Editor Elements

In short, the new Attribute Editor is a completely new tool, extraordinarily versatile and powerful, designed and built in answer to our users’ requests. And we will keep enhancing it.

Exporting models using FMI standard

Functional Mockup Interface (FMI) is a standard for exchanging dynamic models between simulation tools. In this standard, an FMU or Functional Mockup Unit is the unit of exchange, i.e., the model that implements the FMI interface, its binaries or source code and a file that describes the capabilities of the FMI standard as well as information on the model such as the input and output variables. Version 2.0 of the standard defines two ways of exporting models to be used by tools that can understand the FMI interface:

  • Model Exchange: equations and events are exported so that a third party can solve them using a global integrator. This part of the standard is not supported by EcosimPro or PROOSIS.
  • Co-simulation: The model is exported as a black box that has a series of inputs and outputs and its own integrator able to synch with a master in charge of managing the simulation and exchanging data among the different FMUs. This part of the standard is the one supported by both EcosimPro and PROOSIS.

EcosimPro 5.6 and PROOSIS 3.8 introduced the ability to export models following the “FMI 2.0 for Co-simulation” standard, which lets any use model in EcosimPro and send it for use by third-party tools such as Matlab-Symulink, Dymola, ANSYS, Simulation X, AMESim, etc.

Exporting EcosimPro-PROOSIS models using FMI

What’s new to EcosimPro 5.10 and PROOSIS 3.10 is the ability to use FMI 2.0 models for co-simulation that are already generated using EcosimPro 5.6 or greater, PROOSIS 3.8 or greater or any other tool able to export models with the FMI 2.0 interface for co-simulation (AMESim, ANSYS, Dymola, Simulation X, etc.). This new feature can be used to complete a co-simulation diagram much like the one below using PROOSIS or EcosimPro as master simulators:

Exporting EcosimPro-PROOSIS models using FMI

Generating an FMU in EcosimPro or PROOSIS entails creating a model, generating a simple experiment in which to integrate until the next communication interval (CINT), and then generating a deck with the FMI 2.0 co-simulation interface, as shown in the screen shot below:

Exporting EcosimPro-PROOSIS models using FMI

The deck creation wizard also lets you choose the variables that will be FMU inputs and outputs. Once the wizard is done, it will have created an FMU ready to send to a third party:

Exporting EcosimPro-PROOSIS models using FMI

To control an FMU from EcosimPro and PROOSIS, they both include the COMM_FMI library to create components that interact with the FMU and to use them subsequently in other, more complex models or create power co-simulation experiments written in EL, such as the following experiment that load four FMUs containing a turbojet model and are simulated in parallel:

For more details on how to generate FMUs or use FMUs with EcosimPro or PROOSIS, we encourage you to read the chapter on FMI in the EcosimPro and PROOSIS manual.

Modeling Cryogenic Pumps

The simulation team here at Empresarios Agrupados has been doing more work for the ITER experimental fusion reactor. Over this period of time, a prototype of the cryogenic distribution system in ITER (FEDCS) was developed. It includes the auxiliary cold box (ACB) of the cryogenic pumps, the distribution lines that carry the coolant from the ACB to the cold valve box (CVB), the CVB, including its control, and one of the cryogenic pumps of the torus. The final model, which will include all the cryogenic pumps, and has a twofold purpose:

  • Verification of the ITER distribution system (FEDCS) that supplies coolant to the cryogenic pumps.
  • Assistance in the development of the control system, providing information on the system dynamics.

The cryogenic pumps are used in high-vacuum applications and consist of an internal surface (cryogenic panels) cooled to low temperatures where the gases and vapors condense. The gas molecules are immobilized on these surfaces, thus reducing the pressure within the system. In the specific case of ITER, the cryogenic pumps serve two purposes: firstly, they are used downstream from the mechanical pumps to reduce the pressure in the vacuum vessel down to adequate pressure conditions and, secondly, they adsorb the gases from the plasma during reactor operation.

Cryogenic Pumps

Because of the intrinsic difficulty involved in trapping helium particles, the surfaces need to be cooled to a very low temperature (4.5 K). In addition, every so often deuterium and tritium particles are adsorbed with the helium particles. Those particles will subsequently be recovered and treated in the tritium plant so they can be put back into the system. Therefore, the pumps operate in a constant cooling-pumping-heating cycle and are within a temperature range of between 4.5K during the pumping, and 470K during one of the regeneration scenarios.

The FEDCS control system has to operate the clients dynamically in such a way that they comply with the operating requirements of the plasma, taking the correct regeneration of the pumps into account at the same time. Having a dynamic model available has two main advantages: first, it can be used to verify the behavior of the FECDS elements that operate together and second, it can be used to design and verify the complex control system required for correct operation.