FRM Converter and Builder

AIM

1. Explore the FRM Converter model with tutorial number 9.
2. Build FRM Model for the following configuration using FRM builder approach
   1. Bore 102 mm stroke 115 mm CR 17
   2. No of cylinder 6
   3. CI engine
   4. Twin Scroll Turbine
   5. GT Controller
   6. Run all cases

INTRODUCTION

• FRM(Fast Running Model) executes much more rapidly than the typical detailed GT-POWER engine model and is ideal for integrating with other vehicle systems where an accurate and predictive engine plant model is desired and where computational speed is critical.
• FRMs adapt to changing conditions (e.g. valve timing, spark/injection timing, turbo lag, external temperature, altitude, cooling system conditions, etc.) without the need to apply non-physical correction factors. Whether studying changes to ambient conditions or simulating events that are heavily transient in nature, FRMs will maintain the predictive capabilities of a detailed engine model while allowing for the fast computational speeds that are expected when performing drive cycle analysis and other transient-focused simulations.

FRM CONVERTER STUDY

For our fast running model case study, we have selected 4 cylinders direct injection engines, with a turbocharger wastegate controller.

A wastegate is a valve that diverts exhaust gases away from the turbine wheel in a turbocharged engine system. Diversion of exhaust gases regulates the turbine speed, which in turn regulates the rotating speed of the compressor. The primary function of the wastegate is to regulate the maximum boost pressure in turbocharger systems, to protect the engine and the turbocharged.

Gasoline direct injection model is shown below :

FRM conversion process involves various steps, from the conversion of intake port to exhaust port to minimize the time taken is shown below. Before running the FRM model we need to run our base model which will be used to calibrate our result.

To launch the FRM Conversion setup, we need to click on the FRM Converter button. It will validate the tagged subsystems and report if the validation is successful. And after checking In the "Accuracy Checking" dialog, and selecting key RLTs to track the accuracy of the model as the conversion progresses, we can start the conversion process.

After that we will get FRM Reduction window, that is shown below :

STEP 1: Exhaust Manifold

• For our first step, we have selected Exhaust Manifold 1, which restricts the maximum time step. But before modeling this, we change the maximum time step to "720" in run setup, which will allow larger time steps to be used, which will make the solution faster.
• After selecting the exhaust manifold, we have clicked on simplify for accuracy. This will combine the Exhaust Ports/Runners together, and left separate from the manifold volumes.

• After clicking on simplifying for accuracy, two parameters will be formed, one is Discretization Length and other is heat transfer multiplier called [HTM_Exhaust_Manifold_1_Step_1]. This parameter will be used to calibrate heat transfer in the combined volume to assure the Turbine Inlet Temperature is maintained.
• After that, we calibrate our model for case setup 1, which will automatically preprocess our design modification. And for configuring calibration, we have used Averaged Inlet Temperature" from the Turbine part.
• After that, we "Run calibration and run the simulation and then run the model for all cases in the next step which will give the result. After that we check, If any tolerance is outside of the specified range or not.

• We can see none of the tolerance is outside the tolerance limit, as there is no red mark or exclamation mark for missing.

STEP 2: Exhaust Pipes

• For our next step, we have selected the exhaust pipes downstream of the turbine. And then Clicked on "Simplify for Accuracy" and then a window pop up which asked to delete part.
• Since the pipe at the outlet of the Turbine is rather short (70mm), this pipe will be combined with the Catalyst volumes into a single FlowSplit part. We Selected the EP1_Pipe1-1, EP1_PDrop1-1 FlowSplit, and the OrificeConn between them and then right-click on the selection and select combine Flow Volumes Wizard and then named the object "CAT".
• Selected the "CAT-1" from the tree pane template and then in the thermal tab. And then we have selected "Imposed Wall Temperature" and modified the "GasT" Reference Object and provided the "Wireless Signal or RLT (X)" with "tav0: CAT-1 ", which will calculate the average temperature at this point.
• In Case Setup value of [DIA_Exhaust_Pipes_1_Step_2] is set to 40 mm.
• After that, for calibration, we used case setup 1 in the next step, which will automatically preprocess our design modification. And for configuring calibration, we have used the "Turbine Massflow-Averaged Outlet Pressure " from the Turbine part for response RTL.
• After that, we "Run calibration" and then run the model for all cases in the next step which will give the result. After that we check, If any tolerance is outside of the specified range or not.

• We can see none of the value is outside the tolerance limit, as there is no red mark or exclamation mark for missing.

STEP 3: Intake Manifold

• For our next step, we have selected the intake Manifold. And then Clicked on "Simplify for Accuracy" and then a window pop up which asked to delete part.
• After that Characteristic Length and Expansion Diameter attribute values for the combined volume have been changed for the IM1_Plenum1-1 part.

• To resolve the "Delete Part" warning, "RLT Norms" folder, and change the value of the attribute "Part Name for Manifold Volumetric Eff. Reference" to "IM1_Plenum1-1 for EngineCrankTrain after that go to "Run Setup" -> "ConvergenceRLT" folder and change the first RLT Variable to "pav:IM1_Plenum1-1".
• In Case Setup value of [HTM_Intake_Manifold_1_Step_3] is set to 1.
• After that, for calibration, we used case setup 1 in the next step, which will automatically preprocess our design modification. And for configuring calibration, we have used the " Compressor Massflow-Averaged Outlet Pressure " part for response RTL.
• After that, we "Run calibration" and then run the model for all cases in the next step which will give the result. After that we check, If any tolerance is outside of the specified range or not.
  
• We can see none of the value is outside the tolerance limit, as there is no red mark or exclamation mark for missing.

STEP 4: Compressor Outlet Pipes

• For our next step, we have selected Boost Pipes 1. And then Clicked on "Simplify for Accuracy" and then a window pop up which asked to delete part.
• Since the intercooler has been replaced with a FlowSplit and "HeatExchangerConn" part, it will be used to maintain intercooler outlet temperature. "BP1_CAC1-2 HeatExchangerConn" part is used to set the Imposed Fluid Temperature to 300 K.
• After that connection will be established for this control link, which is shown below :

• In Case Setup value of [[DIA_Boost_Pipes_1_Step_4] is set to 35.
• After that, for calibration, we used case setup 1 in the next step, which will automatically preprocess our design modification. And for configuring calibration, we have used the " Compressor Massflow-Averaged Outlet Pressure " part for response RTL.
• After that, we "Run calibration" and then run the model for all cases in the next step which will give the result. After that we check, If any tolerance is outside of the specified range or not.

• We can see none of the value is outside the tolerance limit, as there is no red mark or exclamation mark for missing.

STEP 5: Intake Pipes

• For our next step, we have selected Intake Pipes. And then Clicked on "Simplify for Accuracy" and then a window pop up which asked to delete part.
• We don't need to change anything manually, just set the Case Setup value of [[DIA_Intake_Pipes_1_Step_5] is set to 45.
• After that, for calibration, we used case setup 1 in the next step, which will automatically preprocess our design modification. And for configuring calibration, we have used the " Compressor Massflow-Averaged Inlet Pressure " part for response RTL.
• After that, we "Run calibration" and then run the model for all cases in the next step which will give the result. After that we check, If any tolerance is outside of the specified range or not.

• We can see none of the value is outside the tolerance limit, as there is no red mark or exclamation mark for missing.

STEP 6: Additional Changes

• Again for this step we have selected Exhaust Manifold 1 for further simplification and clicked on "Simplify for Speed". In this case, the Ports, Runners, and Manifold volumes will be combined together at once.

• After that, for calibration, we used case setup 1 in the next step, which will automatically preprocess our design modification. And for configuring calibration, we have used the " Turbine Massflow-Averaged Inlet Temperature" part for response RTL.
• After that, we "Run calibration" and then run the model for all cases in the next step which will give the result. After that we check, If any tolerance is outside of the specified range or not.

STEP 7: Cylinder Slaving

• For this step, we have selected the EngCylinder parts on the map and clicked on the advanced tab to edit, and for "Cylinder Slaving Option", selected "slave-RT-full-v2018". While for cylinder we have overridden the step to "master".
• For this step to work, all Valves must be specified as either an Intake or Exhaust valve. This is done by selecting ValveCamConn template in the model tree on the left and selecting "Edit Parts in Spreadsheet", which is shown below :

• After that, click on calibration to preprocess the model and continue to Calibration. Calibration will not be performed for this step, so simply click on the Run model in the next step. After that we check, If any tolerance is outside of the specified range or not.

• We can see none of the value is outside the tolerance limit, as there is no red mark or exclamation mark for missing.

STEP 8: Real-time Solver

• This is an optional step that is performed here, which can only be run with RT license.
• For this RLTCreatorRT object is selected from the model tree to the left, and dragged it out onto the map. And this object is edited with values provided form the FRM accelerator menu of RTL object, which is shown below.

• After that, click on calibration to preprocess the model in the FRM Reduction option, and continue to Calibration. Calibration will not be performed for this step, so simply click on the Run model in the next step. After that we check, If any tolerance is outside of the specified range or not.

To complete the FRM Conversion process, click "Finish" in the FRM Converter.

The final model after completing all steps is shown below :

FRM BUILDER

• FRM builder is used for creating the fast-running model from scratch. For creating the model, we just need to provide the basic information for our setup.
• The first step is to define what type of model it is if it is Compression Ignition or Spark Ignition. For our case, we have selected a Compression Ignition Model.

• The next step is to define the cylinder geometry, by defining a bore, stroke, and compression ratio as in our case.

• After we have selected the type of turbocharger we are using, for our case setup we have selected a twin-scroll turbocharger setup.

• Next, we have selected the six-cylinder engine type for our configuration.

• Next, we have to define the type of controller we are using. For our specifications, we have selected GT - suite controller.

After defining all of our specification models will be generated with default value calculation and case setup for our case. 6 cylinder diesel engine FRM model is shown below :

• This is our main model, which consists of various sub-assemblies of the object which are defined separately and are linked together. As for inlet, it is defined separately, with inlet environment, intake, and airflow box, which is use filter the air.
• The next setup is for the turbocharger, where the compressor is coupled with the turbine which is connected to the intercooler to maintain the required temperature and pressure.
• And then it is connected to the cylinder and crank train setup with intake and exhaust manifold. And the fuel is directly injected into the cylinder. One part of it connected to exhaust gas recirculation setup and one output to turbocharger setup.
• And then the turbocharger one part output is connected to exhaust setup, where the output cooled air from the turbine is flown back to the environment.
• There is a setup of the controller which is used to provide the required signal to injection control, exhaust gas control, and wastegate controller, these signals are designed to send the required parameters output to this setup.

CASE SETUP

The simulation was run to predefine RPM which is generated by FRM builder for our case setup. There are 25 case setup define, but only seven are shown here.

RESULT

• Simulation has been run for all 25 cases, it took 4min 20 sec total, which way faster if we ran model other than FRM.
• Some of the results of our simulation has been shown below. Most of the RPM and condition selected to give better results for the compressor map.

RPM = 3500 Target BMEP = 17.5

RPM = 2500 Target BMEP = 17.6

RPM = 3000 Target BMEP = 4.4

RPM = 2500 Target BMEP = 4.4

Observation

From the above observation, we can see that at RPM 3000 and 2500 they operate in operating conditions, but cases 1 and 2 at operating RPM 3500 and 2500 these models cant be considered because the operating point is near the choke line for case 1 which is not desirable.

If the compressor operates on the right of the choke line then the compressor will experience choked flow. Choked flow is when the flow reaches the speed of sound and this is a problem because it limits the maximum flow rate through the compressor.

Conclusion

FRM Builder and Converter function have been successfully studied and simulation has also been performed with the given specifications.