[luckyboy]

Hello engineers,
I’m a student, studying in Tianjin University. I want to simulate the combustion of hydrogen-direct inject engine. However, I can’t use spray modeling, because parcel simulation must be select when spray modeling is selected, and in parcel simulation a liquid and its characters are needed to add. As we all know, hydrogen is gas, so there is no atomization in process of injection.
So may you help me how to inject the hydrogen into chamber? And how to setup the mass of injected hydrogen and pressure of injection? And do you have the example about gas-fuel direct injection simulation?
Thank you!

[whysoserious]

Originally Posted by luckyboy

Hello engineers,
I’m a student, studying in Tianjin University. I want to simulate the combustion of hydrogen-direct inject engine. However, I can’t use spray modeling, because parcel simulation must be select when spray modeling is selected, and in parcel simulation a liquid and its characters are needed to add. As we all know, hydrogen is gas, so there is no atomization in process of injection.
So may you help me how to inject the hydrogen into chamber? And how to setup the mass of injected hydrogen and pressure of injection? And do you have the example about gas-fuel direct injection simulation?
Thank you!

Read this paper.
"A Computational Study of the Mixture Preparation in a Direct–Injection Hydrogen Engine"

[luckyboy]

Originally Posted by whysoserious

Read this paper.
"A Computational Study of the Mixture Preparation in a Direct–Injection Hydrogen Engine"

Hello,
I have read the paper, and I have met some troubles. Can you help me?
First, in that paper, mass flow rate is used as the boundary condition for the fuel injection, but in CONVERGE, if mass flow has been selected in velocity boundary condition the box of total pressure can’t be selected in pressure boundary condition. So how to set the injection pressure?
Second, in CONVERGE, is it necessary to use Events between region cylinder and region injector for injection duration? (or is it necessary to build a region for injector?) If yes, in Regions and initialization for injector region, the temperature and the pressure is for fuel? And how to set Turbulence initialization? If no, where does the injection duration set?
I’m a new learner for converge, so there are many troubles for me. I am sorry to excuse you and please help me. Thank you!

[dprobst]

Injecting a gaseous fuel such as hydrogen should be done with an inflow boundary.
You cannot set both the massflow and pressure boundary conditions without over specifying the problem. I would suggest trying the problem with either a massflow or pressure boundary condition, depending on what data you have available to specify the problem.
Unless you are including detail of the hydrogen injector, you do not to create a region for the injector.

[luckyboy]

But how can I set injection duration if I just set pressure boundry condition? what is the pressure of inflow condition after injection, which mean injection stop?

[MFGT]

If you specify a INFLOW boundary and support a massflow.in file, you can easily define the injection duration. Thats the way i went with my master thesis (numerical simulation of CNG-H2 fueled CAI engine).

[luckyboy]

Hello,
When I simulate the hydrogen directly injection, the solver report the error:
” ncyc= 39, time= -1.522219713e-002, crank= -1.369997742e+002, dt= 1.000000000e-008, time-step limit =dt_min forced by dt_cfl
it = 1, WARNING ... extrapolating on the temperature calculation
it = 1, WARNING ... extrapolating on the temperature calculation
it = 1, WARNING ... extrapolating on the temperature calculation
it = 1, WARNING ... extrapolating on the temperature calculation
Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is -1.#IND00, and lower_energy_value is -1.#IND00 .
Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is -1.#IND00, and lower_energy_value is -1.#IND00.”
Can you tell me what cause the error?

[whysoserious]

Originally Posted by luckyboy

Hello,
When I simulate the hydrogen directly injection, the solver report the error:
” ncyc= 39, time= -1.522219713e-002, crank= -1.369997742e+002, dt= 1.000000000e-008, time-step limit =dt_min forced by dt_cfl
it = 1, WARNING ... extrapolating on the temperature calculation
it = 1, WARNING ... extrapolating on the temperature calculation
it = 1, WARNING ... extrapolating on the temperature calculation
it = 1, WARNING ... extrapolating on the temperature calculation
Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is -1.#IND00, and lower_energy_value is -1.#IND00 .
Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is -1.#IND00, and lower_energy_value is -1.#IND00.”
Can you tell me what cause the error?

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