Solution Analysis

Simcenter STAR-CCM+ In-cylinder allows you to analyse the solution of an ICE simulation while the simulation is running as well as when the simulation completes.

To view the progress of the simulation, you generally create and open post-processing objects before running the simulation.

Simcenter STAR-CCM+ In-cylinder provides the following categories of post-processing object:

For all categories, several predefined objects are available that display specific quantities. The availability of these objects varies with the selected engine models, specified materials, and created engine parts.

注In the context of plots and reports, the term "cylinder" refers to the volume of the cylinder without the ports. This volume is limited by the valve curtain interfaces.

Plots

Simcenter STAR-CCM+ In-cylinder provides three kinds of two-dimensional plots:

  • Monitor plots—display specific values collected by monitors as functions of deg crank angle.
  • Histogram plots—displays data distributions using bar charts.
  • XY plots—displays graphs of solution data from the simulation.

For more information, see Plots.

Monitor Plots
Monitor plots display the monitored values in a cycle-by-cycle manner. Results from consecutive cycles overlap on the same plot which means you can look for cyclic convergence, or the tendency to approach a repetitive result.
The following monitor plots are available:
In-Cylinder - Cylinder
  • Cylinder : Air/Fuel Equivalence Ratio—plots the ratio between AFR and the stoichiometric A/F Ratio AFRstoich, see Materials Dialog.
  • Cylinder : Air/Fuel Ratio—plots the ratio between the mass average of the mass fraction of air and the mass average of the mass fraction of fuel vapor in the cylinder and plenums, AFR. For mass fractions of fuel vapor ≤ 1.0E-10,Simcenter STAR-CCM+ In-cylinder limits the air/fuel ratio to a value of 1000. The maximum value that is displayed in the plot is 100 by default.
  • Cylinder : Air Mass Fraction Averaged—plots the mass average of the mass fraction of air in the cylinder and plenums.
  • Cylinder : Apparent Heat Release Rate—plots the apparent heat release rate in the cylinder and plenums as given by Eqn. (648).
  • Cylinder : Chemical Heat Release Rate—plots the chemical heat release rate in the cylinder and plenums.

    For ECFM combustion models, it is computed as the sum of the volume integrals of the following quantities over the cylinder:

    For the Complex Chemistry combustion model, it is computed as the volume integral of the Chemistry Heat Release Rate over the cylinder and plenums.

  • Cylinder : Cumulative Apparent Heat Release—plots the time integral of the Cylinder : Apparent Heat Release Rate from the time the simulation starts.
  • Cylinder : Cumulative Chemical Heat Release—plots the time integral of the Cylinder : Chemical Heat Release Rate from the time the simulation starts.
  • Cylinder : Cyclic Apparent Heat Release—plots the time integral of the Cylinder : Apparent Heat Release Rate in a cycle-by-cycle manner.
  • Cylinder : Cyclic Chemical Heat Release—plots the time integral of the Cylinder : Chemical Heat Release Rate in a cycle-by-cycle manner.
  • Cylinder : Fuel/Air Equivalence Ratio—plots the ratio between FAR and the stoichiometric fuel/air ratio, calculated as FAR⋅AFRstoich.
  • Cylinder : Fuel/Air Ratio—plots the ratio between the mass average of the mass fraction of fuel vapor and the mass average of the mass fraction of air in the cylinder and plenums, FAR. If the mass average of the mass fraction of air drops below 1.0E-10, the ratio is set to 1.
  • Cylinder : Fuel Mass Fraction Averaged—plots the mass average of the mass fraction of fuel vapor in the cylinder and plenums.
  • Cylinder : Indicated Mean Effective Pressure*—plots the net indicated mean effective pressure (IMEP) as given by Eqn. (651).
  • Cylinder : Mass—plots the mass of the gas in the cylinder and plenums, where the mass is calculated as volume integral of density over the cylinder and plenums.
  • Cylinder : Pressure—plots the volume average of the absolute pressure inside the cylinder and plenums.
  • Cylinder : Swirl—plots the swirl inside the cylinder and plenums.
  • Cylinder : Temperature—plots the mass average of the temperature inside the cylinder and plenums.
  • Cylinder : Tumble-X—plots the cross-tumble inside the cylinder and plenums.
  • Cylinder : Tumble-Y—plots the main-tumble inside the cylinder and plenums.
  • Cylinder : Turbulence Kinetic Energy—plots the mass average of the turbulent kinetic energy inside the cylinder and plenums.
  • Cylinder : Volume—plots the volume of the cylinder and plenums.
In-Cylinder - Emissions
  • Cylinder : CO Emission*—plots the mass fraction of CO in the cylinder in parts per milion (ppm).
  • Cylinder : CO Emission Mass Flow Rate*—plots the mass of CO that passes the cylinder in g/hr.
  • Cylinder : CO Emission Molar*—plots the mole fraction of CO in the cylinder in ppm.
  • Cylinder : NOx Emission*—plots the mass fraction of NOx (N2O, NO2, and NO) in the cylinder in ppm.
  • Cylinder : NOx Emission Mass Flow Rate*—plots the mass of NOx that passes the cylinder in g/hr.
  • Cylinder : NOx Emission Molar*—plots the mole fraction of NOx in the cylinder in ppm.
  • Cylinder : Specific CO Emission*—plots the mass of CO per net indicated work in g/kWhr as given by Eqn. (653).
  • Cylinder : Specific NOx Emission*—plots the mass of NOx per net indicated work in g/kWhr as given by Eqn. (653).
In-Cylinder - Injection
  • Fuel Mass Tracking—plots the following quantities evaluated inside the cylinder and the ports:
    • Fuel Mass (Total)—the total mass of the fuel (droplets, vapor, and liquid film)
    • Fuel Mass (Liquid)—the mass of the fuel droplets both injected and stripped from liquid film
    • Fuel Mass (Vapor)—the mass of vapor arising from the droplets
    • Fuel Mass (Film)—the mass of liquid film formed through the impingement of the droplets on the engine walls. This value is calcuated as the surface integral of the product of fluid film thickness and fuel density on the engine walls.
    • [injector] : Fuel Mass (Liquid)—the mass of the fuel droplets injected from [injector]
    • Stripped Film : Fuel Mass (Liquid)—the mass of the fuel droplets stripped from liquid film.
  • [injector] : Injection Velocity—for each nozzle hole of [injector], plots the initial velocity of the injected droplets.
  • [injector] : Liquid Spray Penetration—for each nozzle hole of [injector], plots the distance interval that contains 95% mass of the injected droplets, measuring from the injection point. See Penetration—Parcel and Vapor.
  • [injector] : Vapor Spray Penetration—for each nozzle hole of [injector], plots the distance interval that contains 95% mass of vapor arising from the injected droplets, measuring from the injection point.
  • Maximum Fluid Film Thickness—plots the maximum thickness of liquid film formed through the impingement of fuel droplets on the engine walls.
  • Mean Injection Velocity—plots the mean initial velocity of the injected droplets. For single-pulse injection, this value is calculated based on the total fuel mass injected from start of injection (SOI) until end of injection (EOI). For multipulse injection, this value is calculated based on the total fuel mass injected during each injection pulse.
  • Parcel Count for Fuel—plots the number of fuel parcels inside the engine, where a parcel represents a localized group of fuel droplets having the same properties. See What is a Parcel?.
  • Sauter Mean Diameter—plots the Sauter Mean Diameter of the fuel droplets inside the engine.
In-Cylinder - Intermediary
Cylinder : Gamma Mass Averaged—plots the mass average of the specific heat ratio in the cylinder.
In-Cylinder - Ports and Valves
  • Exhaust / Intake Port : Mass Flow Rate—for each exhaust / intake port, plots the mass of gas that passes the outlet/inlet per unit of time.
  • Exhaust / Intake Port : Pressure—for each exhaust / intake port, plots the surface average of the absolute pressure on the outlet/inlet.
  • Exhaust / Intake Port : Temperature—for each exhaust / intake port, plots the surface average of the temperature on the outlet / inlet.
  • Monitored Valve Lifts—plots the actual lift for each valve during the simulation. The specified Closure Tolerance sets a lower limit to the applied valve lifts.
In-Cylinder - Solution
  • Cell Count—plots the total number of cells in the volume mesh.
  • Cumulative CPU Time—plots the accumulated CPU time for all processes to run the simulation from the time the simulation starts.
  • Cumulative Elapsed Time—plots the cumulative time it takes the solver to run the simulation from the time the simulation starts.
  • PISO Correctors—plots the number of PISO corrector steps within each time-step.
  • Time Step—plots the actual time-step size during the simulation.
The Cumulative CPU Time, Cumulative Elapsed Time, and PISO Correctors plots do not display the respective values in a cycle-by-cycle but in a consecutive manner.
In-Cylinder - Walls
  • Wall Y+—for each Engine Part Surface inside the cylinder that is modeled as wall, plots the surface average of the non-dimensional wall distance y+ given by Eqn. (1584).
  • Wall Y+ Min/Max—plots the minimum value and the maximum value of the non-dimensional wall distance y+ inside the cylinder.
* For each cycle, IMEP and emission plots evaluate the respective values at 0.1 deg before exhaust valve opening (EVO). If the simulation ends before this point in the cycle, the values are evaluated at the end of the simulation.

For example, the following plot displays the Cylinder : Turbulence Kinetic Energy for a simulation that runs for three cycles:

Example:

Histogram Plots
The following histogram plot is available:
In-Cylinder - Injection
Histogram of Droplet Diameter—displays the distribution of droplet diameters for the fuel in the engine:
Example:

The particle diameter on the horizontal scale is divided into discrete bins. The frequency of occurrences—the particle count—is given on the vertical scale.
By default, the maximum value of the horizontal scale is fixed to half of the maximum hydraulic diameter of the injector nozzles.
In-Cylinder - Cylinder
Cylinder : Mass Fraction Burned (Apparent) / (Chemical)—displays the distribution of crank angles at which 10%, 50%, and 90% of the apparent / chemical heat release within a specified combustion interval is reached as well as the 10%-90% duration.

Example:



XY Plots
The following XY plots are available:
In-Cylinder - Cylinder
PV Diagram—displays the cylinder pressure as a function of the cylinder volume on a logarithmic scale.
Example:

In-Cylinder - Injection
  • [injector] : Droplet Diameter—displays the imported distribution of the droplet diameter for [injector] as a cumulative distribution function (CDF) or a probability density function (PDF).
  • [injector] : Fuel Temperature—displays the imported fuel temperature for [injector] as a function of time or crank angle.
  • [injector] : Mass Flow Rate—displays the imported fuel mass flow rate for [injector] as a function of time or crank angle.
In-Cylinder - Ports and Valves
  • Inlet / Outlet Boundary Condition Profiles—for each inlet / outlet, plots the imported boundary condition profiles for absolute pressure and temperature.
  • Valve Lifts—displays the imported valve lift curves for each valve as a function of time or crank angle.
In-Cylinder - Solution
Time Step Preview—displays a preview of the applied time-step size and valve lift curves for the duration of the simulation as a function of crank angle.

Reports

A report represents a computed summary of the current simulation or CPU data. Running a report returns a single value. For more information, see Reporting Results.

For each monitor plot, Simcenter STAR-CCM+ In-cylinder provides a report that returns the respective value. Additionally, the following reports are available:

In-Cylinder - CHT Export
  • CHTExport : Last Mapping Angle —returns the crank angle at which the last data mapping from the engine walls onto the shell regions was performed.
  • CHTExport : Mapping Angle—returns the crank angle at which the next data mapping is performed.
  • CHTExport : Mapping Delta Angle—returns the mapping interval at which the data are mapped.
  • CHTExport : Start Angle Actual—returns the crank angle at which the first data mapping was performed.
In-Cylinder - Cylinder
  • Cylinder : Compression Ratio—returns the ratio of the volume of the cylinder and plenums at BTD to the respective volume at TDC using Eqn. (586).
  • Cylinder : Displacement—returns the volume that is displaced when the piston moves from TDC to BDC using Eqn. (585).
  • Cylinder : Fuel Molecular Weight Averaged—returns the mass average of the molecular weight of fuel in the cylinder and plenums.
  • Cylinder : Peak Cylinder Pressure—returns the maximum value of the volume average of the absolute pressure inside the cylinder and plenums during the simulation.
  • Cylinder : Piston Stretch Ratio—returns the ratio of the current piston z-position to the piston z-position after the last re-mesh.
  • Cylinder : Piston Z—returns the piston z-position using Eqn. (569).
  • Cylinder : Stoichiometric A/F Ratio Averaged—returns the stoichiometric A/F Ratio AFRstoich, see Materials Dialog.
  • Cylinder : Trapped Mass—returns the trapped mass in the cylinder and plenums at intake valve closing (IVC). For a motored-test simulation, this value is calculated as the volume average of the density inside the cylinder and plenums. For a charge-motion simulations, the value is calculated as the volume average of the product of density and void fraction inside the cylinder and plenums. The void fraction is the fraction of the cell volume available to the fluid, unoccupied by a solid or dispersed phase.
In-Cylinder - Emissions
  • Cylinder : CO Mass Fraction—returns the mass average of the mass fraction of CO in the cylinder.
  • Cylinder : CO Mole Fraction—returns the mass average of the mole fraction of CO in the cylinder.
  • Cylinder : NOx Mass Fraction—returns the mass average of the mass fraction of NOx in the cylinder.
  • Cylinder : NOx Mole Fraction—returns the mass average of the mole fraction of NOx in the cylinder.
In-Cylinder - Injection
  • [injector] : Start / End of Injection—returns the crank angle at which the injection of fuel from [injector] starts / ends. The respective crank angle is calculated from the imported mass flow rate table considering the optional offset given by the specified Injection Anchor and Injection Target. For more information, see Injector Dialog.
In-Cylinder - Intermediary
Provides various intermediate reports that are required for the definition of other reports.
In-Cylinder - Ports and Valves
  • Exhaust / Intake Valve [n] : Actual Velocity—returns the actual velocity of exhaust / intake valve [n], calculated as the time derivative of the monitored valve lift. The specified Closure Tolerance sets a lower limit to the valve lift.
  • Exhaust / Intake Valve [n] : Curtain Interface Face Intersection Tolerance—returns the intersection tolerance that is used at the valve curtain interface of exhaust / intake valve [n]. The intersection tolerance limits the distance by which vertices on one side of the interface can move to match vertices, edges, and faces on the other side of the interface.
  • Exhaust / Intake Valve [n] : Displacement—returns the z-position of the exhaust / intake valve [n] minus its Closure Tolerance.
  • Exhaust / Intake Valve [n] : Lift Closure Check—returns 0 when exhaust / intake valve [n] is closed, that is, when the z-position of the valve is smaller or equal to its closure tolerance, and 1 otherwise.
  • Exhaust / Intake Valve [n] : Stretch Ratio—returns the ratio of the current lift of exhaust / intake valve [n] to the valve lift after the last re-mesh.
  • Exhaust / Intake Valve [n] : Z—returns the z-position of exhaust / intake valve [n].
In-Cylinder - Remesh Metrics
  • In-Cylinder Bad Face Validity Remesh Report—returns the number of cells that satisfy the Valid Face Criteria.
  • In-Cylinder Bad Morphed Cell Remesh Report—returns the number of cells that satisfy the Bad Morphed Cell Criteria.
  • In-Cylinder Morph Remesh Report—returns 1 if any of the Re-mesh Criteria is satisfied and 0 otherwise.
  • In-Cylinder Skewness Remesh Report—returns the number of cells that satisfy the Cell Skewness Criteria.
  • Min Cell Quality—returns the minimum cell quality of the volume mesh.
In-Cylinder - Solution
  • Crank Angle—returns the cumulative crank angle in deg.
  • Crank Angle : degCA—returns the cumulative crank angle in cyclic time units (degCA).
  • Crank Angle Cycle—returns the cycle wrapped crank angle (repeats 0 to cycle length) in deg.
  • Crank Angle Cycle : degCA—returns the cycle wrapped crank angle (repeats 0 to cycle length) in cyclic time units.
  • Cycle Length—returns the length of a cycle in deg, such as 720 deg for a four-stroke engine.
  • Cycle Length : degCA—returns the length of a cycle in cyclic time units, such as 720 degCA for a four-stroke engine.
  • Cycle Number—returns the number of the current cycle.
  • Revolutions per Cycle—returns the revolutions per cycle, such as 2 for a four-stroke engine.

Scenes

Scenes allow you to visualize the geometry, mesh, and solution data that are contained in the simulation.

Scenes encapsulate the complete representation of components that are required to generate an image or an animation. Within a scene, displayers bring together parts and other attributes (such as scalars and surface properties) to produce graphics primitives which are displayed in the scene. For more information, see Visualizing the Solution.

Simcenter STAR-CCM+ In-cylinder provides a number of predefined scenes. These scenes allow you to examine specific solution fields from which you can draw conclusions about the performance of your engine.

The following predefined scenes are available:

  • Absolute Pressure
  • CHT Export
  • Fluid Film Thickness
  • Fuel Distribution
  • Temperature
  • Turbulent Kinetic Energy
  • Velocity Magnitude

The Fuel Distribution scene allows you to visualize multiple definitions of air-fuel mixture ratio. For each definition, the scene provides a specific displayer, where the visibility of each displayer can be toggled as required.

The following definitions are available:

  • air/fuel ratio—the ratio between the mass fraction of air and the mass fraction of fuel vapor. For mass fractions of fuel vapor ≤ 1.0E-10,Simcenter STAR-CCM+ In-cylinder limits the air/fuel ratio to a value of 1000.
  • air/fuel equivalence ratio—the ratio between the air/fuel ratio and the stoichiometric A/F Ratio AFRstoich, see Materials Dialog.
  • fuel/air ratio—the ratio between the mass fraction of fuel vapor and the mass fraction of air. For mass factions of air ≤ 1.0E-10, the fuel/air ratio is limited to a value of 1.
  • fuel/air equivalence ratio—the ratio between the fuel/air ratio and the stoichiometric fuel/air ratio, calculated as the product of the fuel/air ratio and AFRstoich.

For charge-motion and combustion simulations, all predefined scenes additionally display the injected fuel parcels within the engine. On the parcels, Simcenter STAR-CCM+ In-cylinder visualizes the particle diameter by default. The screen display size of the parcels is scaled according to the particle diameter, where the particle diameter range is mapped to a physical size range of [1.0E-4 m; 4.0E-4 m] relative to the mesh dimensions. For more information, see Point Size Scale Field.

The Fluid Film Thickness scene displays the thickness of the fluid film on the engine walls. The CHT Export scene shows the cycle-averaged local heat transfer reference temperature on the engine walls. All other scenes display its respective solution field on a plane section that cuts through one of the intake valves and one of the exhaust valves and is oriented normal to the Y-direction. For example, the following image displays the Velocity Magnitude scene for a motored-test simulation:



To access solution data in other areas of the engine domain, Simcenter STAR-CCM+ In-cylinder provides the following additional plane sections:

  • Cylinder Center X Plane
  • Cylinder Center Y Plane
  • Cylinder Center Z Plane
  • Exhaust Valve 1 X Section
  • Intake Valve 1 X Section
  • Intake Valve 1 Y Section
  • Intake Valve 2 Y Section

The following image shows the location and orientation of the different plane sections for an engine with two intake valves and exhaust valves, respectively:



For cylinder sector models, Simcenter STAR-CCM+ In-cylinder provides the following plane sections:

  • Injector X Axis Plane
  • Injector Y Axis Plane
  • Sector XZ Plane

The location and orientation of the Injector X Axis Plane and the Injector Y Axis Plane depend on the injector position, origin, and target. The following image shows the the different plane sections for a cylinder sector model:



Additionally, Simcenter STAR-CCM+ In-cylinder allows you to display scalar fields on cylinder and valve surfaces.

For all predefined scenes in Simcenter STAR-CCM+ In-cylinder, you can toggle the visibility of displayers and their parts as required. Removing parts from displayers is not supported—when you reload a simulation, Simcenter STAR-CCM+ In-cylinder automatically restores the removed parts.