.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "examples/engine/multizone.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. note:: :class: sphx-glr-download-link-note :ref:`Go to the end ` to download the full example code. .. rst-class:: sphx-glr-example-title .. _sphx_glr_examples_engine_multizone.py: .. _ref_multizone_engine: ================================= Simulate a multi-zone HCCI engine ================================= Ansys Chemkin offers some idealized internal combustion (IC) engine models commonly used for fuel combustion and engine performance research. The Chemkin IC engine model is a specialized transient 0-D *closed* gas-phase reactor that mainly performs combustion simulation between the intake valve closing (IVC) and the exhaust valve opening (EVO), that is, when the engine cylinder resembles a closed chamber. The cylinder volume is derived from the piston motion as a function of the engine crank angle (CA) and engine parameters such as engine speed (RPM) and stroke. The energy equation is always solved and there are several wall heat transfer models specifically designed for engine simulations. .. note :: For additional information on the Chemkin IC engine models, use the ``ansys.chemkin.core.manuals()`` method to view the online **Theory** manual. The multi-zone homogeneous charged compression ignition (HCCI) model is mainly intended to address the temperature variation inside the cylinder caused by the wall heat transfer and the imperfect mixing of the in-cylinder gas mixture. In addition, the multi-zone HCCI engine model allows the introduction of non-uniform temperature and/or the equivalence ratio distribution of the gas mixture at the IVC. This example shows how to set up and run the Chemkin multi-zone HCCI engine model. Many engine model-specific features, such as basic engine parameters, exhaust gas recirculation, and wall heat transfer, are applied to the engine simulation. This example also shows how to create initial distributions of zone size, temperature, and composition. .. GENERATED FROM PYTHON SOURCE LINES 57-59 .. code-block:: Python :dedent: 1 .. GENERATED FROM PYTHON SOURCE LINES 61-63 Import PyChemkin packages and start the logger ============================================== .. GENERATED FROM PYTHON SOURCE LINES 63-87 .. code-block:: Python from pathlib import Path import matplotlib.pyplot as plt # plotting import numpy as np # number crunching import ansys.chemkin.core as ck # Chemkin from ansys.chemkin.core import Color # Chemkin homogeneous charge compression ignition (HCCI) engine model (transient) from ansys.chemkin.core.engines.HCCI import HCCIengine from ansys.chemkin.core.logger import logger # check working directory current_dir = str(Path.cwd()) logger.debug("working directory: " + current_dir) # set verbose mode ck.set_verbose(True) # set interactive mode for plotting the results # interactive = True: display plot # interactive = False: save plot as a PNG file global interactive interactive = True .. GENERATED FROM PYTHON SOURCE LINES 88-93 Create a chemistry set ====================== The mechanism to load is the GRI 3.0 mechanism for methane combustion. This mechanism and its associated data files come with the standard Ansys Chemkin installation in the ``/reaction/data`` directory. .. GENERATED FROM PYTHON SOURCE LINES 93-105 .. code-block:: Python # set mechanism directory (the default Chemkin mechanism data directory) data_dir = Path(ck.ansys_dir) / "reaction" / "data" mechanism_dir = data_dir # create a chemistry set based on the GRI mechanism MyGasMech = ck.Chemistry(label="GRI 3.0") # set mechanism input files # including the full file path is recommended MyGasMech.chemfile = str(mechanism_dir / "grimech30_chem.inp") MyGasMech.thermfile = str(mechanism_dir / "grimech30_thermo.dat") MyGasMech.tranfile = str(mechanism_dir / "grimech30_transport.dat") .. GENERATED FROM PYTHON SOURCE LINES 106-108 Preprocess the chemistry set ============================ .. GENERATED FROM PYTHON SOURCE LINES 108-112 .. code-block:: Python # preprocess the mechanism files ierror = MyGasMech.preprocess() .. GENERATED FROM PYTHON SOURCE LINES 113-124 Set up the fuel-air mixture ============================ You must set up the fuel-air mixture inside the engine cylinder right after the intake valve is closed. Here the ``x_by_equivalence_ratio()`` method is used. You create the ``fuelmixture`` and the ``air`` mixtures first. You then define the *complete combustion product species* and provide the *additives* composition if there is any. Finally, you set the ``equivalenceratio`` value to create the fuel-air mixture. In this case, the fuel mixture consists of methane, ethane, and propane as the simulated natural gas. Because HCCI engines generally run on lean fuel-air mixtures, the equivalence ratio is set to 0.8. .. GENERATED FROM PYTHON SOURCE LINES 124-158 .. code-block:: Python # create the fuel mixture fuelmixture = ck.Mixture(MyGasMech) # set fuel composition fuelmixture.x = [("CH4", 0.9), ("C3H8", 0.05), ("C2H6", 0.05)] # setting pressure and temperature is not required in this case fuelmixture.pressure = 1.5 * ck.P_ATM fuelmixture.temperature = 400.0 # create the oxidizer mixture: air air = ck.Mixture(MyGasMech) air.x = [("O2", 0.21), ("N2", 0.79)] # setting pressure and temperature is not required in this case air.pressure = 1.5 * ck.P_ATM air.temperature = 400.0 # create the unburned fuel-air mixture fresh = ck.Mixture(MyGasMech) # products from the complete combustion of the fuel mixture and air products = ["CO2", "H2O", "N2"] # species mole fractions of added/inert mixture. # can also create an additives mixture here add_frac = np.zeros(MyGasMech.kk, dtype=np.double) # no additives: all zeros # mean equivalence ratio equiv = 0.8 ierror = fresh.x_by_equivalence_ratio( MyGasMech, fuelmixture.x, air.x, add_frac, products, equivalenceratio=equiv ) # check fuel-oxidizer mixture creation status if ierror != 0: print("Error: Failed to create the fuel-oxidizer mixture.") exit() # list the composition of the unburned fuel-air mixture fresh.list_composition(mode="mole") .. GENERATED FROM PYTHON SOURCE LINES 159-164 Specify pressure and temperature of the fuel-air mixture ======================================================== Since you are going to use the ``fresh`` fuel-air mixture to instantiate the engine object later, setting the mixture pressure and temperature is equivalent to setting the initial temperature and pressure of the engine cylinder. .. GENERATED FROM PYTHON SOURCE LINES 164-167 .. code-block:: Python fresh.temperature = 447.0 fresh.pressure = 1.065 * ck.P_ATM .. GENERATED FROM PYTHON SOURCE LINES 168-183 Add EGR to the fresh fuel-air mixture ===================================== Many engines have the configuration for exhaust gas recirculation (EGR). Chemkin engine models allow you to add the EGR mixture to the fresh fuel-air mixture entered the cylinder. If the engine you are modeling has EGR, you should have the EGR ratio, which is generally the volume ratio between the EGR mixture and the fresh fuel-air ratio. However, because you know nothing about the composition of the exhaust gas, you cannot simply combine these two mixtures. In this case, you use the ``get_egr_mole_fraction()`` method to estimate the major components of the exhaust gas from the combustion of the fresh fuel-air mixture. The ``threshold=1.0e-8`` parameter tells the method to ignore any species with a mole fraction below the threshold value. Once you have the EGR mixture composition, use the ``x_by_equivalence_ratio()`` method a second time to re-create the ``fresh`` fuel-air mixture with the original ``fuelmixture`` and ``air`` mixtures along with the EGR composition you just got as the *"additives"*. .. GENERATED FROM PYTHON SOURCE LINES 183-200 .. code-block:: Python egr_ratio = 0.3 # compute the EGR stream composition in mole fractions add_frac = fresh.get_egr_mole_fraction(egr_ratio, threshold=1.0e-8) # recreate the initial mixture with EGR ierror = fresh.x_by_equivalence_ratio( MyGasMech, fuelmixture.x, air.x, add_frac, products, equivalenceratio=equiv, threshold=1.0e-8, ) # list the composition of the fuel+air+EGR mixture for verification fresh.list_composition(mode="mole", bound=1.0e-8) .. GENERATED FROM PYTHON SOURCE LINES 201-207 Set up the HCCI engine reactor ============================== Use the ``HCCIengine()`` method to create a multi-zone HCCI engine named ``MyMZEngine`` and make the new ``fresh`` mixture as the initial incylinder gas mixture at IVC. Set the ``nzones`` parameter to the number of zones in your multi-zone HCCI engine model. .. GENERATED FROM PYTHON SOURCE LINES 207-214 .. code-block:: Python # create a five-zone HCCI engine numbzones = 5 MyMZEngine = HCCIengine(reactor_condition=fresh, nzones=numbzones) # show initial gas composition inside the reactor MyMZEngine.list_composition(mode="mole", bound=1.0e-8) .. GENERATED FROM PYTHON SOURCE LINES 215-222 Set basic engine parameters =========================== Set the required engine parameters as shown in the following code. These engine parameters are used to describe the cylinder volume during the simulation. The ``starting_ca`` argument should be the crank angle corresponding to the cylinder IVC. The ``ending_ca`` is typically the EVC crank angle. .. GENERATED FROM PYTHON SOURCE LINES 222-246 .. code-block:: Python # cylinder bore diameter [cm] MyMZEngine.bore = 12.065 # engine stroke [cm] MyMZEngine.stroke = 14.005 # connecting rod length [cm] MyMZEngine.connecting_rod_length = 26.0093 # compression ratio [-] MyMZEngine.compression_ratio = 16.5 # engine speed [RPM] MyMZEngine.rpm = 1000 # set other parameters # simulation start CA [degree] MyMZEngine.starting_ca = -142.0 # simulation end CA [degree] MyMZEngine.ending_ca = 116.0 # list the engine parameters MyMZEngine.list_engine_parameters() print(f"engine displacement volume {MyMZEngine.get_displacement_volume()} [cm3]") print(f"engine clearance volume {MyMZEngine.get_clearance_volume()} [cm3]") print(f"number of zone(s) = {MyMZEngine.get_number_of_zones()}") .. GENERATED FROM PYTHON SOURCE LINES 247-268 Set up the engine wall heat transfer model ========================================== By default, the engine cylinder is adiabatic. You must set up a wall heat transfer model to include the heat loss effects in your engine simulation. Chemkin support three widely used engine wall heat transfer models. The models and their parameters follow. - ``dimensionless``: [ ] - ``dimensional``: [ ] - ``hohenburg``: [ ] There is also the in-cylinder gas velocity correlation (the Woschni correlation) that is associated with the engine wall heat transfer models. Here are the parameters of the Woschni correlation: ``[ ]`` You can also specify the surface areas of the piston head and the cylinder head for more precision heat transfer wall area. By default, both the piston head and the cylinder head surfaces are flat. .. GENERATED FROM PYTHON SOURCE LINES 268-282 .. code-block:: Python heattransferparameters = [0.035, 0.71, 0.0] # set cylinder wall temperature [K] t_wall = 400.0 MyMZEngine.set_wall_heat_transfer("dimensionless", heattransferparameters, t_wall) # in-cylinder gas velocity correlation parameter (Woschni) # [ ] gv_parameters = [2.28, 0.308, 3.24, 0.0] MyMZEngine.set_gas_velocity_correlation(gv_parameters) # set piston head top surface area [cm2] MyMZEngine.set_piston_head_area(area=124.75) # set cylinder clearance surface area [cm2] MyMZEngine.set_cylinder_head_area(area=123.5) .. GENERATED FROM PYTHON SOURCE LINES 283-289 Set zonal properties ==================== By default, all zones in the multi-zone HCCI engine model have the same properties. You can artificially stratify the temperature and/or the equivalence ratio distribution in the cylinder at the IVC by utilizing the ``set_zonal`` methods of the ``HCCI`` object. .. GENERATED FROM PYTHON SOURCE LINES 289-315 .. code-block:: Python # zonal temperatures [K] ztemperature = [447.5, 447.5, 447, 447, 447] MyMZEngine.set_zonal_temperature(zonetemp=ztemperature) # zonal volume fractions zvolumefrac = [0.3, 0.25, 0.2, 0.2, 0.05] MyMZEngine.set_zonal_volume_fraction(zonevol=zvolumefrac) # wall heat transfer area fractions zht_area = [0.0, 0.15, 0.2, 0.25, 0.4] MyMZEngine.set_zonal_heat_transfer_area_fraction(zonearea=zht_area) # zonal equivalence ratios zphi = [equiv, equiv, equiv, equiv, equiv] MyMZEngine.set_zonal_equivalence_ratio(zonephi=zphi) # zonal EGR ratios zegrr = [0.3, 0.3, 0.3, 0.35, 0.35] MyMZEngine.set_zonal_egr_ratio(zoneegr=zegrr) # set fuel "molar" composition MyMZEngine.define_fuel_composition([("CH4", 0.9), ("C3H8", 0.05), ("C2H6", 0.05)]) # set oxidizer "molar' composition MyMZEngine.define_oxid_composition([("O2", 0.21), ("N2", 0.79)]) # set products MyMZEngine.define_product_composition(["CO2", "H2O", "N2"]) # set EGR composition in mole fractions zadd = [add_frac, add_frac, add_frac, add_frac, add_frac] MyMZEngine.define_additive_fractions(addfrac=zadd) .. GENERATED FROM PYTHON SOURCE LINES 316-342 Set output options ================== You can turn on the adaptive solution saving to resolve the steep variations in the solution profile. Here additional solution data points are saved for every 20*solver internal steps. You must include the ``set_ignition_delay()`` method for the engine model to report the ignition delay crank angle after the simulation is done. If ``method="T_inflection"`` is set, the reactor model treats the inflection points in the predicted gas temperature profile as the indication of an auto-ignition. You can choose a different auto-ignition definition. .. note:: - Type ``ansys.chemkin.core.show_ignition_definitions()`` to get the list of all available ignition delay time definitions in Chemkin. - The ``set_ignition_delay()`` method is required for the engine model to report the ignition delay time for each zone as well as the cylinder averaged ignition delay time derived from the cylinder averaged temperature profile. - By default, time/crank angle intervals for both print and save solution are 1/100 of the simulation duration, which in this case is :math:`dCA=(EVO-IVC)/100=2.58`\ . You can make the model report more frequently by using the ``ca_step_for_saving_solution()`` or the ``ca_step_for_printing_solution()`` method to set different interval values in the crank angle. .. GENERATED FROM PYTHON SOURCE LINES 342-352 .. code-block:: Python # set the number of crank angles between saving solution MyMZEngine.ca_step_for_saving_solution = 0.5 # set the number of crank angles between printing solution MyMZEngine.ca_step_for_printing_solution = 10.0 # turn on adaptive solution saving MyMZEngine.adaptive_solution_saving(mode=True, steps=20) # specify the ignition definitions MyMZEngine.set_ignition_delay(method="T_inflection") .. GENERATED FROM PYTHON SOURCE LINES 353-357 Set solver controls =================== You can overwrite the default solver controls by using solver-related methods, such as those for tolerances. .. GENERATED FROM PYTHON SOURCE LINES 357-375 .. code-block:: Python # set tolerances in tuple: (absolute tolerance, relative tolerance) MyMZEngine.tolerances = (1.0e-12, 1.0e-10) # get solver parameters atol, rtol = MyMZEngine.tolerances print(f"Default absolute tolerance = {atol}.") print(f"Default relative tolerance = {rtol}") # turn on the force non-negative solutions option in the solver MyMZEngine.force_nonnegative = True # show solver and output options # show the number of crank angles between printing solution print( f"Crank angles between solution printing: " f"{MyMZEngine.ca_step_for_printing_solution}" ) # show other transient solver setup print(f"Forced non-negative solution values: {MyMZEngine.force_nonnegative}") .. GENERATED FROM PYTHON SOURCE LINES 376-381 Display the added parameters (keywords) ======================================= Use the ``showkeywordinputlines()`` method to verify that the preceding parameters are correctly assigned to the engine model. .. GENERATED FROM PYTHON SOURCE LINES 381-383 .. code-block:: Python MyMZEngine.showkeywordinputlines() .. GENERATED FROM PYTHON SOURCE LINES 384-387 Run the simulation ================== Use the ``run()`` method to start the multi-zone HCCI engine simulation. .. GENERATED FROM PYTHON SOURCE LINES 387-396 .. code-block:: Python runstatus = MyMZEngine.run() # check run status if runstatus != 0: # Run failed. print(Color.RED + ">>> Run failed. <<<", end=Color.END) exit() # Run succeeded. print(Color.GREEN + ">>> Run completed. <<<", end=Color.END) .. GENERATED FROM PYTHON SOURCE LINES 397-401 Get the ignition delay crank angle from the solution ==================================================== Use the ``get_ignition_delay()`` method to extract the cylinder averaged ignition delay crank angle (CA) after the run is completed. .. GENERATED FROM PYTHON SOURCE LINES 401-406 .. code-block:: Python # get ignition delay "time" delay_ca = MyMZEngine.get_ignition_delay() print(f"Ignition delay CA = {delay_ca} [degree].") .. GENERATED FROM PYTHON SOURCE LINES 407-413 Get the heat release crank angles ================================= The engine models also report the crank angles when the accumulated heat release reaches 10%, 50%, and 90% of the total heat release. Use the ``get_engine_heat_release_cas()`` method to extract these heat release crank angles (CA). .. GENERATED FROM PYTHON SOURCE LINES 413-420 .. code-block:: Python hr10, hr50, hr90 = MyMZEngine.get_engine_heat_release_cas() print("Engine Heat Release Information:") print(f"10% heat release CA = {hr10} [degree].") print(f"50% heat release CA = {hr50} [degree].") print(f"90% heat release CA = {hr90} [degree].\n") .. GENERATED FROM PYTHON SOURCE LINES 421-447 Postprocess the solution =====================_== The postprocessing step parses the solution and packages the solution values at each time point into a mixture. There are two ways to access the solution profiles: - The raw solution profiles (value as a function of time) are available for time, temperature, pressure, volume, and species mass fractions. - The mixtures permit the use of all property and rate utilities to extract information such as viscosity, density, and mole fractions. You can use the ``get_solution_variable_profile()`` method to get the raw solution profiles. You can get solution mixtures using either the ``get_solution_mixture_at_index()`` method for the solution mixture at a given time point or the ``get_solution_mixture()`` method for the solution mixture at a given time. (In this case, the mixture is constructed by interpolation.) .. note :: - For engine models, use the ``process_engine_solution()`` method to postprocess the solutions. - Use the ``getnumbersolutionpoints()`` method to get the size of the solution profiles before creating the arrays. - Use the ``get_ca()`` method to convert the time values reported in the solution to crank angles. .. GENERATED FROM PYTHON SOURCE LINES 449-468 Postprocess the solution profiles in selected zone ================================================== The solution of the multi-zone HCCI engine model contains the results of the individual zones plus the cylinder averaged results. This means that if there are n zones in the multi-zone engine model, there are (n+1) solution records: n zonal results and the cylinder averaged results. To process the result of the zone number :math:`j`\ , :math:`(1 \leq j \leq n)`\ , set the parameter value of ``zone_id`` to :math:`j` when you call the engine postprocessor with the ``process_engine_solution()`` method. Otherwise, the cylinder averaged results are postprocessed by default, that is, when the ``zone_id`` parameter is omitted. .. note :: Because The ``process_engine_solution()`` method can process only one set of results at a time (one zonal result or the cylinder averaged result), you must postprocess the zones one by one to obtain all solution data of the multi-zone simulation. .. GENERATED FROM PYTHON SOURCE LINES 468-513 .. code-block:: Python thiszone = 1 MyMZEngine.process_engine_solution(zone_id=thiszone) plottitle = "Zone " + str(thiszone) + " Solution" # get the number of solution time points solutionpoints = MyMZEngine.getnumbersolutionpoints() print(f"Number of solution points = {solutionpoints}.") # get the time profile timeprofile = MyMZEngine.get_solution_variable_profile("time") # convert time to crank angle ca_profile = np.zeros_like(timeprofile, dtype=np.double) count = 0 for t in timeprofile: ca_profile[count] = MyMZEngine.get_ca(timeprofile[count]) count += 1 # get the cylinder pressure profile presprofile = MyMZEngine.get_solution_variable_profile("pressure") presprofile *= 1.0e-6 # get the zonal volume profile volprofile = MyMZEngine.get_solution_variable_profile("volume") # create arrays for zonal mixture density and mixture specific heat capacity denprofile = np.zeros_like(timeprofile, dtype=np.double) viscprofile = np.zeros_like(timeprofile, dtype=np.double) # loop over all solution time points for i in range(solutionpoints): # get the zonal mixture at the time point solutionmixture = MyMZEngine.get_solution_mixture_at_index(solution_index=i) # get zonal gas density [g/cm3] denprofile[i] = solutionmixture.rho # get zonal mixture viscosity profile [g/cm-sec] or [Poise] viscprofile[i] = solutionmixture.mixture_viscosity() * 1.0e2 # post-process cylinder-averged solution # do NOT set the zone_id parameter MyMZEngine.process_average_engine_solution() # get the cylinder volume profile cylindervolprofile = MyMZEngine.get_solution_variable_profile("volume") # create arrays for cylinder-averaged mixture density cylinderdenprofile = np.zeros_like(timeprofile, dtype=np.double) # loop over all solution time points for i in range(solutionpoints): # get the zonal mixture at the time point solutionmixture = MyMZEngine.get_solution_mixture_at_index(solution_index=i) # get zonal gas density [g/cm3] cylinderdenprofile[i] = solutionmixture.rho .. GENERATED FROM PYTHON SOURCE LINES 514-523 Plot the engine solution profiles ================================= Plot the zonal and the cylinder averaged profiles from the multi-zone HCCI engine simulation. .. note :: You can get profiles of the thermodynamic and the transport properties by applying ``Mixture`` utility methods to the solution mixtures. .. GENERATED FROM PYTHON SOURCE LINES 523-548 .. code-block:: Python plt.subplots(2, 2, sharex="col", figsize=(12, 6)) plt.suptitle(plottitle, fontsize=16) plt.subplot(221) plt.plot(ca_profile, presprofile, "r-") plt.ylabel("Pressure [bar]") plt.subplot(222) plt.plot(ca_profile, volprofile, "b-") plt.plot(ca_profile, cylindervolprofile, "b--") plt.ylabel("Volume [cm3]") plt.legend(["Zone", "Cylinder"], loc="upper right") plt.subplot(223) plt.plot(ca_profile, denprofile, "g-") plt.plot(ca_profile, cylinderdenprofile, "g--") plt.xlabel("Crank Angle [degree]") plt.ylabel("Mixture Density [g/cm3]") plt.legend(["Zone", "Averaged"], loc="upper left") plt.subplot(224) plt.plot(ca_profile, viscprofile, "m-") plt.xlabel("Crank Angle [degree]") plt.ylabel("Mixture Viscosity [cP]") # plot results if interactive: plt.show() else: plt.savefig("plot_multizone_HCCI_engine.png", bbox_inches="tight") .. _sphx_glr_download_examples_engine_multizone.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: multizone.ipynb ` .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: multizone.py ` .. container:: sphx-glr-download sphx-glr-download-zip :download:`Download zipped: multizone.zip ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_