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radial inflow turbine based on Brian Parrelli advice

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Old   January 9, 2017, 17:28
Default radial inflow turbine based on Brian Parrelli advice
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Ahmad Hari
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Hi all,

Based on Mr. Brain advice, I simulated a radial inflow turbine with stator vanes and rotor blades, not only rotor blades as last time.

The input conditions at the stator inlet in the 1D code are:

Ptot, in = 350 KPa
Ttot, in = 300 KPa
Pstat, out = 100 KPa
Rotational speed = 39632 rpm
mass flow rate = 0.3 kg/s


My turbine has 20 stator vanes and 10 rotor blades. So, I selected two stator vanes and 1 rotor blade for simulation.

However, compared to Rital and other software, the results in Ansys CFX are different ! For example: the total to total efficiency in Rital is 86% while it is 38% in Ansys CFX. The mass flow rate in Rital is 0.3 kg/s while it is 0.615 kg/s in Ansys CFX. Same thing for the power output and velocity traingles !

I have no idea what mistakes I made. So, I attached screenshots of the 1D results (from Rital), and the setting and results from Ansys CFX.

Any kind of recommendation is highly appreciated as I'm run out of time and very exhausted!
Attached Images
File Type: jpg 1. results of the 1D code.jpg (60.2 KB, 11 views)
File Type: jpg 2. inlet and outlet conditions.jpg (21.3 KB, 11 views)
File Type: jpg 3. stator setting.jpg (34.5 KB, 10 views)
File Type: jpg 4. Rotor setting.jpg (189.0 KB, 10 views)
File Type: jpg 5. Mixing plane (stage) setting.jpg (77.0 KB, 10 views)
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Old   January 9, 2017, 17:29
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Ahmad Hari
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Continue attachments
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File Type: jpg 6. solver control.jpg (94.0 KB, 4 views)
File Type: jpg 7. setting R134a.jpg (154.6 KB, 5 views)
File Type: jpg 8. CFD Post results.jpg (53.1 KB, 5 views)
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Old   January 9, 2017, 17:55
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Glenn Horrocks
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Have you done the basic error checks discussed in the FAQ? https://www.cfd-online.com/Wiki/Ansy..._inaccurate.3F
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Old   January 10, 2017, 09:21
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Quote:
Originally Posted by ghorrocks View Post
Have you done the basic error checks discussed in the FAQ? https://www.cfd-online.com/Wiki/Ansy..._inaccurate.3F
Ye I have .. I tried coarse and fine meshing while keeping all other parameters the same. The results are pretty much the same for both grid size

The change in the total to efficiency is 2.5%
The change in the mass flow rate is 0.4%
The change in the shaft power is 2.5%
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Old   January 10, 2017, 09:36
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The first image indicates an incidence angle at the rotor inlet while your ANSYS CFX setup indicates flow normal to the inlet. Those are different cases.

Can you try modifying the inlet flow direction in ANSYS CFX to match the 1-D setup ?
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Old   January 10, 2017, 10:19
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Hi Opaque,

That's correct there is an incidence angle at the rotor inlet in the 1D simulation. When it comes to Ansys CFX, I only set Mixed plane (Stag) between exit of the stator and inlet of the rotor with pitch ratio = 1. I guess this all what I can play with in Ansys CFX. I have nothing to do with rotor inlet when mixing plane is applied.

I set the flow normal to the inlet at the stator inlet not the rotor inlet.
Is it possible to set the incidence angle at the rotor inlet at Ansys CFX?
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