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Transient simulation (Problem with massflow and Pressure) |
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August 22, 2011, 10:58 |
Transient simulation (Problem with massflow and Pressure)
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#1 |
New Member
Christian F
Join Date: Mar 2011
Posts: 8
Rep Power: 15 |
Hello everybody,
i am simulating a rotary piston engine. The Simulation is working but the problem is the following: At the beginning the pressure inside of the cylinder is 0 bar (reference pressure is 1 bar). At the inlet the pressure is 3 bar. While the piston is moving, air is flowing from the intlet in the cylinder and the pressure rises. When the pressure in the cylinder is reaching the 3 bars (The maximum pressure) the pressure an massflow increase from the inlet into the cylinder should go down, but i am reaching even 3.5 bars until the massflow goes down. As you can see in the diagram the pressure for a certain time step is not changing anymore after some iteration steps. So i am only reaching the 3 bars after some timesteps (which is of course different to the reality). In a steady state analysis for a certain Piston positon i am reaching the 3 bars after about 30 iteration steps. So what do i have to do to get the simulation closer to the reality? Thanks. |
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August 22, 2011, 11:00 |
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#2 |
New Member
Christian F
Join Date: Mar 2011
Posts: 8
Rep Power: 15 |
I am sorry i forgot to upload the picture
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August 22, 2011, 11:40 |
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#3 |
Senior Member
Join Date: Jul 2011
Location: Berlin, Germany
Posts: 173
Rep Power: 15 |
How big is the time step used and how did you set up your inlet boundary(pressure and mass flow)?
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August 22, 2011, 12:46 |
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#4 |
New Member
Christian F
Join Date: Mar 2011
Posts: 8
Rep Power: 15 |
Inlet: -Total Pressure (3 bar)
- Total Temp 25C° Timestep: -1/60000 s (1.666e-5 s) -> Engine is rotating with 10000 rpm so in one timestep the piston is moving 1° |
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August 22, 2011, 22:42 |
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#5 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,871
Rep Power: 144 |
http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F
You would need to include more details if you want us to be more specific. |
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