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Simulating Radial Inflow Turbine - Mass Flow Rate at Inlet not matching outlet

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Old   March 8, 2019, 11:53
Default Simulating Radial Inflow Turbine - Mass Flow Rate at Inlet not matching outlet
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Hey, i am currently trying to simulate a radial inflow turbine using ansys cfx. I first meshed the rotor and stator in turbogrid. I setup 3 domains in cfx, S1 for the stator, R1 for the rotor and S2 for the outlet. My boundary conditions are total pressure at inlet, total temperature and static pressure at outlet. I have 2 interfaces, stage mixing between S1 and R1. Frozen Rotor between R1 and S2. Simulating real gas (R123) with RGP file. There is currently a difference of around 5% between the mass flow rate at the inlet and mass flow rate at the outlet. (~0.41kg/s inlet, ~0.43/0.44 kg/s outlet)R1.jpg

Radial.jpg

inlet.jpg

outlet.jpg

INTERFACE1.jpg
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Old   March 8, 2019, 11:54
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Could not add more than 5 attchments to last post. INTERFACE2.jpg
Had to cut out timesteps from 38-300 as the file was too largeOUTFILE.txt

Last edited by mobangi12; March 8, 2019 at 13:14. Reason: Added OUT file
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Old   March 8, 2019, 15:06
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Has the simulation fully converged?

Have you looked at the imbalances for all domains?
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Old   March 8, 2019, 15:52
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Hey thanks for your reply, the solution was fully converged. I had a few that ran for 1000+ iterations with the same result. I have a theory that its something to do with the fact that i have 22 stator blades and 15 rotor blades. So for each rotor blade there are 22/15 stator blades. Not too sure though. And these ar my imbalances, they dont look too large.

+--------------------------------------------------------------------+
| Normalised Imbalance Summary |
+--------------------------------------------------------------------+
| Equation | Maximum Flow | Imbalance (%) |
+--------------------------------------------------------------------+
| U-Mom-R1 | 9.8032E+01 | -0.0084 |
| V-Mom-R1 | 9.8032E+01 | -0.0023 |
| W-Mom-R1 | 9.8032E+01 | 0.0000 |
| P-Mass-R1 | 2.9154E-02 | 0.0032 |
| U-Mom-S2 | 9.8032E+01 | 0.0000 |
| V-Mom-S2 | 9.8032E+01 | 0.0000 |
| W-Mom-S2 | 9.8032E+01 | 0.0000 |
| P-Mass-S2 | 2.9154E-02 | 0.0001 |
| U-Mom-S1 | 9.8032E+01 | 0.0009 |
| V-Mom-S1 | 9.8032E+01 | -0.0008 |
| W-Mom-S1 | 9.8032E+01 | -0.0075 |
| P-Mass-S1 | 2.9154E-02 | -0.1077 |
+----------------------+-----------------------+---------------------+
| H-Energy-R1 | 1.2675E+04 | 0.0032 |
| H-Energy-S2 | 1.2675E+04 | 0.0000 |
| H-Energy-S1 | 1.2675E+04 | -0.1099 |
+----------------------+-----------------------+---------------------+

================================================== ====================
Wall Force and Moment Summary
================================================== ====================
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Old   March 8, 2019, 16:06
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Do i maybe need to model 3 nozzles and 2 rotors as opposed to my 1 nozzle and 1 rotor at the moment? Would this affect my solution?
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Old   March 8, 2019, 16:17
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Are you using appropriate expressions to evaluate mass flow at the inlet/outlet?

e.g. massFlow()@S1 Inlet*22
massFlow()@S2 Outlet*15
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Old   March 8, 2019, 16:53
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found a way to fix it

Last edited by mobangi12; March 8, 2019 at 21:40.
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cfx, interface, mass flow, radial turbine, real gas model

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