Assignment 7: FRM Converter and FRM Builder in GT Power

Aim:

To understand the process to convert High fidelity engine model to Fast Running Model (FRM) and to build FRM model using GT-Power.

Objective:

1.To Explore tutorial number 9

2.Build FRM Model for following configuration using FRM builder approach:

• Bore 102 mm stroke 115 mm CR 17
• No of cylinder 6
• CI engine
• Twin Scroll Turbine
• GT Controller

Introduction:

Fast Running Engine Models are dynamic, fully-physical engine models that are designed specifically to run fast. While high-fidelity engine models are commonplace in the engine performance department, they are often too slow running to incorporate into system level models where long transient events may be simulated, or where the simulation model must respond faster than real-time, such as for HiL (Hardware-in-the-Loop) simulations. When simulation speed is of priority, high-fidelity GT-POWER engine models can be simplified into FRMs using a standard conversion process.

FRMs are able to achieve such fast run times by two means:

(1) Increasing the simulation time step size, and

(2) Decreasing the number of calculations per time step

Tutorial 9:

This tutorial covers the process of converting detailed, high-fidelity engine model into a Real-Time capable Fast Running Engine Model (FRM).

While this tutorial shows a specific set of steps, note that each engine model is unique and so the steps required to convert a detailed model will depend on the complexity of the model, as well as on the goals of the end user.

Model:

The engine is a 4-cylinder, four-stroke, Turbocharged direct injection, 2L gasoline engine. Combustion is modelled by the’Si-Wiebe’. In-cylinder heat transfer is modelled using the ‘Woschni’ model. Turbine waste-gate is being controlled to achieve target BMEP. Fuel ratio is specified by FAR.

Fig: 4 cylinder Turbochargerd GDi Model

FRM Conversion:

Step 1: Exhaust manifold

In high fidelity Model, Exhaust manifold where High exhaust gas velocities occurs and hence take large time steps.

Step 2: Exhaust Pipes

For the second step of model simplification, the exhaust pipes downstream of the turbine will be simplified. 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 using ’Combine Flow Volumes wizard’.

Step 3: Intake Manifold

For the third step of model simplification, the intake Manifold will be simplified.

Step 4: Compressor Outlet Pipes

For the Fourth step of model simplification, the compressor outlet pipes will be simplified.

Step 5: Intake Pipes

For the Fifth step of model simplification, the Inlet pipes will be simplified.

Step 6: Exhaust Port

For the Sixth step of model simplification, the Exhaust ports will be combined into single one using ’Combine Flow Volumes wizard’.

Step 7: Cylinder Slaving

‘Master’ indicates that the calculated cylinder pressure for this cylinder will be analyzed, and the resulting burn rate and heat transfer rate will be stored for use by other cylinder parts designated as "slave".

Step 8: Real-Time Solver

By adding Real Time Solver allows us to operate GT Suite with Hardware in Loop(HiL) with Real Time Response.To run with the real-time solver, the license type of the model must be changed.

Fig: simplified Engine Model with Real Time Solver

Thus, any High fidelity Engine model can be converted into Fast Running Model using FRM Converter.

FRM Builder:

Fast Running Modelis build with following specification:

• Bore 102 mm & stroke 115 mm
• CR 17
• No of cylinder 6
• CI engine
• Twin Scroll Turbine
• GT Controller

Steps:

1.Define Engine Type.

2.Define Engine cylinder Geometry.

3.Define No. of cylinder.

4.Define type of Turbocharger.

5.Define Control Logic Type.

Case Setup:

There are total 25 Case Setups to be run with different engine speed and target BMEP .

For the sake of our simplicity, we will them in Group of 5.

Case Setup 1:5

Result:

Engine Operating Condition and Performance Prediction:

MEP:

Compressor Map:

Turbine Map:

Case Setup 6:10

Result:

Engine Operating Condition and Performance Prediction:

Engine MEP:

Compressor Map:

Turbine Map:

Case Setup 11:15

Result:

Engine Operating Condition and Performance Prediction:

Engine MEP:

Compressor Map:

Turbine Map:

Case Setup 16:20

Result:

Engine Operating Condition and Performance Prediction:

Engine MEP:

Compressor Map:

Turbine Map:

Case Setup 21:25

Result:

Engine Operating Condition and Performance Prediction:

Engine MEP:

Compressor Map:

Turbine Map:

Conclusion:

• Target BMEP is achieved in almost all cases.
• With higher Target Load and BMEP,compressor and Turbine operates with Critical Speed.
• With Lower Target Load and BMEP, operating points on compressor map lie in Heart region with the disadvantage of producing less power and target.
• With Lower Target Load and BMEP,BSFC values tends to be on Higher side.