[jabuor]

Hi everyone,
I am working in my valveless pulsejet simulation and I can't get the expected results: It seems that combustions does not occur, thus there are not pulses...
I will explain what I have been doing for my set up, so if someone has any clue what the mistake might be, please comment below.

I have done a 2D problem.
Solver: Pressure-Based, transient, velocity relative, 2D Space Planar.

Models: Energy, k-e realizable, Radiation P1, Species Non-Premixed combustion (c3h8: propane)

BC: 2 fuel inlet: inlet mass-flow 0.1kg/s each;
inlet: pressure inlet 0 pascal Gauge Total Pressure;
outlet: pressure outlet 0 pascal Gauge Total Pressure;
wall: stationary and with 20W/m^2*K of heat transfer
coefficient (convection)
Methods: Coupled
Controls: I left the flow courant number predefined (200) and I lowered 0.2 every under-relaxation factor except the mean mixture fraction and variance.

Initialization: Standard, compute from all-zones in order to establish a mean mixture fraction of 1, temperature of 1600K and a 5m/s x-velocity. It was thought to start a simulation from a previous combustion.

Calculation: time step size: 0.0001s, Max iteration/Time Step: 20

I think the mesh is not a problem. As it is a big surface I will update 3 differents pics so you can give your opinion:
https://ibb.co/9G06PpD
https://ibb.co/Nj18dv8
https://ibb.co/F3TsgTW

I am also sharing the animations I have obtained of temperature and velocity so you can see how the propane is mixing properly but (VIDEOS UPDATED OF LAST SIMULATION)
https://drive.google.com/drive/folde...9h?usp=sharing

Pease, if you could help me it will mean so much as it is part of an important personal project Thanks in advance to everyone taking their time

[jabuor]

I am simulating again but with the only change on the combustion parameters. Now I have chosen species transport and selected the Finite-Rate/Edddy-Dissipation on Turbulance-Chemestry Interaction.

The inicialization is the same but now I have patched most of the combustion chamber in order to decrease the pressure (-5000 Pa) and create compression. I attach the pictures of the patching.

https://ibb.co/F0NT0kC
https://ibb.co/C0WkgH0

[vinerm]

How are you modeling the density of the mixture?

[jabuor]

Originally Posted by vinerm

How are you modeling the density of the mixture?

In the species transportation method I picked the propane-air mixture but I did not model any density, probably predefine. But as I read in different pulsejet posts it is normally used non-premixed combustion models and in those I think you can't model the density of the mixture. I really don't know what I am doing wrong.

[vinerm]

Until and unless you use real gas models, user has control over density method to be used. You need to use ideal-gas for pulse jet.

[jabuor]

For the non-premixed combustion the density was selected from the pdf created. So I believe I have to change pdf to real-gas-soave-redlich-kwong. I will try again Thank you

[vinerm]

If density is also coming from pdf table, then let it be as it is. Real gas is not easy to converge.

[jabuor]

Originally Posted by vinerm

If density is also coming from pdf table, then let it be as it is. Real gas is not easy to converge.

okey... So I believe that was not the problem. What should I do?
UPDATE: the last simulation I obtained combustion and pulsation but in the inlet area and the gases were not eject from the outlet. I used hybrid initialization and PISO scheme. Also I diminish the initial temperature of the whole pulsejet to 1000K and I set 0.01kg/s for the inflow mass of fuel.
You can see the animations of temperature and velocity in the videos of the link: https://drive.google.com/drive/folde...4ToB7br-_4Re9h