Table of Contents
Gas properties
AGA-8 calculates density, but viscosity models vary by composition; which theory does BOSpulse use for dynamic viscosity?
When using the AGA-8 (GERG-2008) equation of state, the viscosity can be either specified explicitly as a piece-wise linear function of the temperature, or calculated by BOSpulse. In the latter case the per-component gas viscosity is calculated with Sutherland’s law. The component values are combined by means of the Herning and Zipperer method to obtain the viscosity of the compound gas.
Reciprocating compressor modelling
What type of element are you using to connect the recip cylinder boundary condition to the gas passages? Can you explain your gas passage modelling?
We use pipe elements to model gas passages. We adjust the acoustic length to obtain the correct acoustic dimensions and volumes. The acoustic dimensions and pipe volumes tend to be the two most important parameters when modelling a gas passage. BOSpulse comes with an example model, named “API618Assessment”, that features a model of a compressor including the gas passage. The construction of this model is explained in more detail in this series of webinars.
Does the Ariel import bring in values for simulated valve numbers?
No, unfortunately detailed valve data are not available in the Ariel data files. When importing such a file into BOSpulse, the compressor valves will be modelled as ideal valves.
Multiple cases, parameter studies and batch analysis
How is a batch analysis set up for several gas cases, load steps and compressor combinations (e.g. A, B, C alone and in parallel)?
You can do that manually, through the script interface or through the Ariel compressor import interface.
With three or more compressors, using variable phases creates too many runs. Any thoughts on how to handle that situation?
Yes indeed, the size of the parameter space will increase very rapidly with the number of compressors. To restrict the parameter space, you could vary each phase shift in a crude way, say with four or maybe eight steps. After that, you could apply a custom parameter schedule to zoom in on the locations in the parameter space that lead to the largest pulsations or shaking forces.
An alternative approach might be to analyse each compressor separately in a different scenario (set one compressor active, and unload or deactivate the other compressors). Then you could combine the results from the different scenarios, either by using a virtual case, or by means of some spreadsheet manipulations. In the latter case you can use the custom report function to get the results from each scenario into a spreadsheet.
How are mechanical natural frequency and a DA2 study run for multiple cases, such as two or three pumps running at the same time?
You can perform a (multi-dimensional) parameter study and/or use virtual cases to combine results from multiple scenarios.
How are mitigation options (restriction orifices, volumes, chokes) tested in the model?
You typically do so by means of multiple scenarios in which you modify certain aspects of a model. You can also deactivate certain parts of a model in a scenario.
Pumps and liquid service
How is pulsation from rotary lobe and progressing cavity pumps in sludge service assessed and mitigated?
You can model rotary lobe and other positive displacement equipment in BOSpulse by means of a periodic flow boundary condition. This requires that you know the flow profile within one time period. The new BOSpulse release supports non-Newtonian liquids.
Analysis types and structural modelling
Can you show a worked example of a FIP analysis?
Yes. I can also explain how the new Junction Activation parameter works. The pressure source amplitudes are based on an analytical model described in literature. Note that BOSpulse assumes that pulsations are only significant if they excite natural acoustic modes in a system.
Can BOSpulse model piping together with steel structures?
Yes, you can include supports and beam elements in a piping model. These will be accounted for when performing a structural analysis by means of the ANSYS interface. You can also export the beam elements to CAESAR II.
How do pulsation analysis and transient response analysis relate in BOSpulse?
BOSpulse focuses on periodic flow conditions. We have another application, named BOSfluids, that focuses on steady state and general transient flow conditions.
Results and reporting
What has changed in reporting in this release?
You can select multiple data sets when generating a custom report. You also get information about unfiltered peak-peak pressure pulsations if you have specified an allowable limit for them.
Does the new release include a waterfall diagram with peak hold spectra along a selected piping section or branch?
Maybe a Profile Plot is what you are looking for?
Will BOSpulse run on a Windows 7 HP workstation?
Will BOSpulse run on a Windows 7 HP workstation?
Probably not, but you could try it. A trial version of BOSpulse can be downloaded from our website. You can also try running BOSview (also available from our website). If that program runs correctly, then BOSpulse probably will too. We develop our applications for Windows 11, as that is the operating system currently supported by Microsoft.