Assignment 7
Objective
To explore FRM models and create a FRM model for a given engine configuration using FRM builder approach
FRM-(Fast Running Model)
A FRM model is a fully physical engine model that is designed specifically to run fast. When simulation speed is of priority, high-fidelity GT-POWER engine models can be simplified into FRMs using a standard conversion process.
A detailed engine model can either be converted in to a FRM using FRM Converter tool or a FRM can be created for the given engine configuration using FRM Builder tool.
FRMs are able to achieve such fast run times by two means:
(1) increasing the simulation time step size
(2) decreasing the number of calculations per time step
These two means are often accomplished at the same time by lumping various flow volumes together which will reduce the total number of subvolumes and also allow for a larger time step size by increasing the effective subvolume length (which is responsible for the time step size).
In addition to simplifying and combining flow volumes, there are additional solver options that can reduce the number of calculations per time step and, thus, further decrease the run time without changing the time step size.
Tutorial Explanation
Detailed engine model
Detailed Engine model converted to FRM Model
The above engine model is a 4 cylinder Turbocharged Gasoline Direct injection engine with a wastegate controller and a intercooler.
It can be seen that in the FRM model intake and exhaust manifolds are converted in to a single flowsplit having 5 boundaries connecting the ports of the cylinders to their respective engine parts .This way the total number of sub-volumes are reduced which decreases the simulation time.
The time variable calculates the actual time taken by the engine to complete 34 cycles (Period) and the CPU time variable gives the time taken by the solver to achieve steady state. It takes 34 cycles to achieve steady state in this case.
The solver will take more time to solve a detailed engine model than a FRM model which is shown in the above case.
FRM BUILDER
Given Engine Configuration
|
Engine type |
Compression Ignition (CI) |
|
Fuel used |
Diesel |
|
No of cylinders |
6 |
|
Cylinder Bore |
102 mm |
|
Cylinder stroke |
115 mm |
|
Compression Ratio |
17 |
|
Turbocharger type |
Twin scroll Turbo |
|
Number of cases |
Engine speed range |
The FRM builder tool is used to create a FRM model of the above given engine configuration.
FRM MAIN MODEL:
The detailed assembly parts of the main FRM model is shown below
FRM Intake:
FRM Turbocharger:
FRM Cylinder & Manifolds:
FRM Exhaust:
FRM EGR:
FRM Controller:
Simulation Time
FRM Models are especially useful when the user wants to run for several cases as shown above. It greatly reduces the simulation time.