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Select Simulation⏐Create Series Results and then select Cycle Simulation.

In the first column of the table you can select whether you want series-results created for each of the case-sets. Series-results can only be created for case-sets with one or more parameters assigned through case-explorer. In the Main Parameter column you can select main-parameter for each case-set. The State column indicates the state of creation process for each case-set. Creation process is started by pressing Run-Creation button.

When calculating series results via Simulation | Run | Creation of Series Results BOOST always creates series results versus the left-most parameter of the first parameter group in the case explorer. The same behavior is valid for optimizations e.g. via the Design Explorer.

Description of states:

New - always set when the dialog is opened Started - creation of results has started Done - creation process finished successfully Failed - creation process failed

The creation process can fail for a number of reasons, the most common being that the simulation has not been run for some or all of the cases in the case-set.

Starting from a single case model, it is possible to create a case series calculation. This allows parameters to be assigned for a set of cases so that a series of operating points or engine variants can be calculated at one time.

Refer to section 2.5.3 of the GUI Users Guide for a detailed description of the Case Explorer. Also refer to the BOOST case series calculation (ottoser.bwf – Examples Manual) for details.

2.4. Utilities

2.4.1. BURN

The BURN utility can be used for combustion analysis, which is the inverse process of the combustion calculation performed in the BOOST cylinder. That is, the rate of heat release (ROHR) can be obtained from measured cylinder pressure traces. The resulting ROHR can be used to specify the combustion characteristics of a single zone or two zone model.

For the analysis, general data is necessary about the type of engine and fuel, geometry data for the cylinder and data describing the operating point. After the analysis the results can be examined, especially the calculated rate of heat release (ROHR).

Select BURN from the Utilities menu to open the following window.

Figure 2-13: Burn - Global Window

Summary Opens the ASCII browser and displays the summary values from the simulation (refer to Chapter 5).

Copy Data from 'Globals' and...

Copy

Select the required cylinder from the pull-down menu and then select Copy. This allows existing data specified for a cylinder in the model to be used for the combustion analysis.

Alternatively while inputting the cylinder data for a BOOST model, select Table under the Combustion sub-group. In this case the resulting ROHR can be accepted immediately after calculation.

2.4.1.1. Globals

The global data shown in Figure 2-13 is described under section 2.3.

Analysis: Select either 1 zone or 2 zone (burned and unburned) for the number of zones considered in the combustion analysis.

2.4.1.2. Cylinder

The cylinder specifications are the same as those necessary for the BOOST cylinder.

Number of Cylinders

The total number of cylinders in the engine. This is used to calculate the mass flows to each individual cylinder by dividing the air and fuel mass flows by this number.

Bore, Stroke, Compression Ratio, Conrod Length

Main geometry data of the cylinder.

Piston Pin Offset The direction of positive Piston Pin Offset is defined as the direction of the rotation of the crankshaft at TDC.

Effective Blow By Gap, Mean Crank Case Pressure

For the consideration of blow-by from the cylinder, an equivalent Effective Blow-By Gap has to be specified, as well as the Average Crankcase Pressure. The actual blow-by mass flow is calculated from the conditions in the cylinder, the pressure in the crankcase and the effective flow area calculated from the circumference of the cylinder and the effective blow-by gap.

User Defined Piston Motion

If the piston motion and volume changes cannot be derived from the main cylinder geometry data, the piston position can be defined as a

54Table depending on crank angle, by selecting User Defined Piston Motion, input fields under Piston Motion.

Only the relative position must be specified, a value of 0 meaning piston at TDC, a value of 1 meaning piston at BDC.

In Cylinder Evaporation

For direct injection engines the rate of evaporation can be defined.

The Rate of Evaporation defines the addition of fuel vapor to the cylinder charge. The specified curve is normalized, so that the area beneath the curve is equal to one. The actual amount of fuel added is either defined directly or by the target A/F-Ratio.

The latent heat of evaporation of the fuel (Evaporation Heat) is defined independent of the main fuel definition.

The Heat from Wall specifies the fraction of the evaporation energy taken from the wall as opposed to the gas. An input value of 1 means that all the fuel evaporates on the wall and the in cylinder evaporation will have no affect on the gas mixture in the cylinder. An input value of 0 means the fuel evaporates in the gas mixture in the cylinder.

2.4.1.3. Heat Transfer

Four different models are available for modeling the Heat Transfer in the Cylinder:

• Woschni 1978

• Woschni 1990

• Hohenberg

• AVL 2000

The extension of the Woschni model by Lorenz is not available, because engines with prechamber are not considered for the combustion analysis.

For the wall heat transfer the surfaces of Piston, Cylinder Head and Liner must be specified. The variation of the wetted liner surface is considered automatically, only the surface with piston at TDC must be input. With the Calibration Factor the wall heat transfer calculated from the specific model may be increased or decreased. The factors may also be specified as tables accessible in the specific substructures.

Layer Discretization is available for the Liner wall heat transfer.

The wall temperatures are specified in the following section.

2.4.1.4. Operation Point

It is possible to perform the analysis for more than one operating point with a single procedure. Therefore two types of input data are available:

• Data describing the operating point, e.g. engine speed, wall temperatures, valve timing and mass flows.

Select the Operation Point sub-group folder to add or remove operating points by using Insert Row and Operating Point and Remove Row and Operating Point. The values for engine speed and load cannot be specified directly in the table but after specifying data each operating point, the table can be used to examine these values.

Select the required Operating Point, e.g. OP(1) and specify the following:

Figure 2-14: Burn - Operating Point Window

Engine Speed / BMEP

Engine Speed and measured Mean Effective Pressure (BMEP). Load as BMEP. The load does not influence the results and is used only to describe the operating point.

Start of High Pressure

Crank angle for the start of the high pressure phase. Should be set to Intake Valve Closing (IVC). This defines the starting crank angle for the combustion analysis calculation.

End of High Pressure

Crank angle for the end of the high pressure phase. Should be set to Exhaust Valve Opening (EVO). This defines the end crank angle for the combustion analysis calculation.

Air Massflow / Fuel Massflow

Specify for the whole engine. The value for a single cylinder is determined by dividing these numbers by the number of cylinders in the engine, assuming an even distribution to the cylinders.

Trapping Efficiency Air / Trapping Efficiency Fuel

If the assumption of even distribution is not valid Trapping Efficiency Air and Trapping Efficiency Fuel also can be used to consider such an effect.

Wall Temperature Wall Temperature must be defined for piston, head and liner in the same way as it is done for BOOST.