PDM Analysis Ltd is pleased to announce the release of the new version V5.9 of software SCORG.
SCORGTM is a unique software for the design and analysis of positive displacement machines such as screw compressors, expanders, pumps and motors. Read the article to familiarise yourself with our upgrades and see how you can take advantage of them while designing and analysing your machines.
Upgraded Batch Commands Utility
We believe that this is a major step towards expanding and using SCORG for rigorous design evaluations and performance optimisation through automation.
Batch commands have been arranged into three categories:
- Project level commands – you can execute tasks such as creating a new project from an existing one or setting the path to a project on which you want your batch process to work.
- Calculation level commands – in the previous version you could create a set of commands such as geometric or thermodynamics calculations and then you would have to launch the SCORG GUI and run it using execute batch commands through the GUI. Now you can do it in a completely silent mode. The GUI is not presented to the user. Also, you are able to arrange a different set of commands in a sequence and those commands will be executed on the specified project.
- Parameterisation – using a new keyword “paramchange” any of the variables in the spf file which directly defines the setup of the selected project can be changed. You can switch one or multiple parameters at the time, e.g. gap size, wrap angle, operating pressure or grid generation parameters.
SCORG V5.9 comes with a sample script to learn the use of commands and the Help documentation has further details of the batch command utility.
Figure 1: Batch Commands Utility
CAD Export of Rotors, Bore and Geometry Domains
The next development is the CAD model export utility. It could be very useful when you are designing the compressor or the expander because the ports defined by the cut out on the helix are not easy to be created on the CAD model. If you have a utility that can directly export the given shape and size of the port it becomes a reference for the CAD design. Further, the parameterisation available in SCORG makes it easy to try several designs and export their CAD quickly.
In the current implementation, we have three formats that can be exported STL, STEP and IGES.
Another typical use of CAD export is conjugate heat transfer. The rotor geometry which is generated from SCORG exactly aligns with the mesh that is generated for the fluid part. If you are doing a parametric study with the conjugated transfer, it becomes very handy to export the CAD data directly from SCORG and use it in your conjugate heat transfer analysis.
In the webinar recording, you can see an example for a 3/5 compressor the gate rotor is not visible. The discharge port can be seen and the local temperature of the gas which is much higher as compared to the solid temperature is visible. On the solid side, the time step size was artificially modified, it was incremented to get us to a steady state within the time steps that were solved for the transient flow solution.
ANSYS Forte Export
The same CAD export utility has been extended to the ANSYS Forte solver. It is an automatic mesh solver based on Cut-Cell Cartesian Remeshing.
Using this feature of SCORG, you will be able to generate the assembly of rotors, bore volume and the suction and discharge ports and pipe that can be directly used for the CFD model setup in ANSYS Forte solver.
You can watch the webinar recording to see an example of a piston-cylinder case 2D cross-section that has been taken in the circular cylinder. You do not need the SCORG generated mesh for the application because this works with the Cut-Cell Cartesian Remeshing. For the user getting the CAD data from SCORG can be useful.
The assembly of the hook and claw is shown as an example. This typical grid generation is currently not available in SCORG so users which are exploring this kind of geometry can take advantage of ANSYS Forte export.
Figure 2: ANSYS Forte – Export
Bearing Selection Utility
One of the main tasks for designers of screw machines is to select bearings that will enable the reliable operation of a machine during its required lifecycle. In order to assist designers with this challenging task, in V5.9 we introduced bearing selection utility. In it, based on the forces earlier calculated in SCORG, you can select rolling element bearings from the database of available bearings. It is then probable to assess how the change in operating conditions such as pressures or operational speed or composition of the gas being compressed would affect the bearing life.
Improvements in Thermodynamic Chamber Modelling
One of the significant improvements in chamber modelling is the correction of the sealing line using the Savitzky-Golay filter. Usually, when you import a profile from 3D CAD, approximations that are done in a CAD or measuring errors can produce a noisy sealing line. You can use this filter for correcting that sealing line and set up the value as it suits best for you.
Figure 3: Correction of sealing line using Savitzky-Golay filter
The reliability and efficiency of screw machines are greatly dependant on the size of operational clearances in the machine, especially in the case of oil-free machines. Accurate calculation of operational clearances is ever more important in order to ensure that your machine produces expected delivery reliably. In V5.9 we have introduced the facility to calculate operational radial clearances using the conjugate heat transfer. That is based on years of research in this area. It enables the users of SCORG to evaluate limits in operating conditions for a particular machine both in deterioration of performance and reducing clearances that can cause catastrophic failure of a machine. The conjugate transfer feature allows you to calculate operational appearances in the machines.
Integration with GT-SUITE v2021
With the new release, the GT-SUITE screw machine model files have been updated to v2021 and a dedicated tutorial is available. The updated models now include the option to call on an integrated subassembly for power loss calculations depending on whether there are hydrodynamic or rolling element bearings present.
The user may calculate the thermodynamics of screw machines using either SCORG Thermodynamics or with the GT-SUITE solver. In the case of GT-SUITE, it is possible to model screw expanders which is currently unavailable in SCORG but is under development for the next release.
It is also feasible to model two-stage machines with GT-SUITE based on the geometrical information provided by SCORG. Examples are also available upon request for optimising screw machines in GT-SUITE as well as for two-stage compression and expansion calculations.
The new Script language introduced in V5.9 also allows the optimisation procedures available in GT-SUITE v2021 to be used in conjunction with SCORG thermodynamics for full optimisation of screw machines.
For more information, you can watch the webinar recording:
PDM Analysis Ltd would like to thank users of SCORG for their commitment to our unique software for the design and analysis of positive displacement machines and their comments and suggestions for improvements.
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