Design of Inlet Guide Vane (IGV) for Centrifugal Compressors

All centrifugal compressor designers want to achieve the highest efficiency as well as wide operating range. With this in mind, the inlet guide vane (IGV) is a convenient and economic option for various applications.

IGVs are a series of blades circumferentially arranged at the inlet of compressor, driven electronically or pneumatically.By adjusting the orientation of IGVs, the air flow enters the impeller at a different direction therefore changing the flow behavior while affecting the passing mass flow rate (throttling). This can effectively reduce the power consumption to increase the compressor’s overall efficiency while avoiding surge to provide a better off design working range.

The designer needs to optimize blade profile and positioning of the IGV for efficient operation of a compressor, which can be a tedious job if one does not have a handy tool. Figure 1 shows an example of IGV working on different angles.

Example IGV Characteristic Curve
Figure 1. Example IGV Characteristic Curve

In AxSTREAM, people are able to add IGV component before the centrifugal compressor impeller which can provide different ways to edit its profile such as:

  1. Directly accessing variables in the project (grid)
  2. Meridional coordinates (in viewer, 1D/2D streamline module)
  3. Axial profiler and blade design

Figure 2 shows the interface of adding an axial IGV to your compressor.

Figure 2 How to Insert Axial IGV in AxSTREAM

After setting all data information like tip/hub diameters, number of blades, clearance, stacking mode for 3D blade, etc., you will be able to see the flow path and 3D models in a graphic interface, as shown in Figure 3.

Figure 3 Flow Path and 3D Model of Centrifugal Compressor with Axial IGV

Then you can include  theIGV into the calculation both in a 1D/2D module or 3D CFD module. You can also create numerical experiments, comparing design and off-design performance with different IGV profiles and angle setting.

If you want to also take into account of diffuser design, you can do so with different combination of IGV/diffuser parameters. You could also run several tens of design simultaneously in batch mode and automatically obtain the optimized design.

Contact us at Sales@Softinway.com for a demo of more AxSTREAM features for centrifugal compressor design.

References:

http://manualarchive.ingersollrandproducts.com/manuals/manuals/instructionbook/Misc_Manuals/principles_operation.pdf

http://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=2718&context=icec

http://manualarchive.ingersollrandproducts.com/manuals/manuals/instructionbook/Misc_Manuals/principles_operation.pdf

Gas Turbine Cooling Technology

Turbine Cooling Scheme Designed in AxSTREAM NET
Figure 1. Turbine Cooling Scheme Designed in AxSTREAM NET

People are pushing turbine inlet temperature to extremes to achieve higher power and efficiency. Material scientists have contributed a lot to developing the most durable material under high temperatures such as special steels, titanium alloys and superalloys. However, turbine inlet temperature can be as high as 1700˚C [1] and cooling has to be integrated to the system to prolong blade life, secure operation and achieve economic viability.

A high pressure turbine can use up to 30% of the compressor air for cooling, purge, and leakage flows, which is a huge loss for efficiency. It is worth it only if the gain of turbine inlet temperature can outweigh the loss of cooling. This applies to both aviation engines and land based gas turbines.

The history of turbine cooling goes back 50 years and has evolved to fit different environments. The diversity of turbine cooling technology we see today is just the tip of the iceberg. As time goes on and technology advances, people are able to achieve higher cooling efficiency at lower coolant usages. For different goals and needs, different constructs can be applied but the detailed cooling design must balance with the whole system and make the most of technological advances in the areas. For example, if the flow path is optimized, mechanical design is modified, or if new material is employed, the cooling design needs to change accordingly. One thing worth mentioning is that manufacturing of hot section components and turbine cooling design have an interdependent cause and effect, outpacing and leading each other to new levels. Merging of disciplines and additive manufacturing will, in the future, bring more flexibility to turbine cooling design.

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