FRM Modeling
FRM Modeling
FRM or Fast-Running Model is a method to solve IC engine problems in GT-SUITE by controlling and compressing the detailed model into something that has the basic necessities to perform a faster simulation at the cost of a little accuracy. But the overall model is fairly accurate and provides a ball park view of the physical model that is to be simulated.
It is a shortcut method to model and find out whether the general technical specifications given can provide the results which we expect. A detailed model takes up too much space and takes a lot of time to solve compared to the FRM approach. But the detailed model is used to make predictive analysis of an engine since it is far more accurate than the FRM.
In this project, we look at the tutorials for FRM in GT-SUITE and how to use the FRM Builder to build an engine with the given specifications:
- Bore: 102 mm | stroke: 115 mm | CR: 17
- No. of cylinder: 6
- CI engine
- Twin Scroll Turbine
- GT Controller
Creating using the FRM Builder:
The FRM Builder will be located in the tools tab.
Create a new engine model or also paste an existing detailed model and compress that into an FRM model.
The bore stroke values given are entered.
For now the configurations are limited to 4 or 6 cylinders for CI engines and in case for SI engines, they start from 3 engines inline.
The twin scroll turbocharger type is selected for a 6 cylinder CI engine.
Since we are familiar with GT-SUITE, we can use the corresponding controller itself.
After clicking finish, we see how easy it is to build an engine model using FRM approach.
These are the case setups in the model that are assumed by default. We have to run all the cases here to view the results.
If you look inside the FRM models and blocks set up, you can see how the detailed model has been broken down for the FRM approach.
We know that the detailed model consists of manifold pipes and different inlet and exhaust pipes. But as we can see, the FRM approach assumes all of these pipes and manifolds as a single volume for easier discretization and faster results. Basically in FRM, the mesh is reduced and size to a generic model which given approximate results that are fairly accurate for a summary.
Likewise, there are different tabs for each of the part and how they connect to the blocks created in FRM to other parts of the engine. The blue marks show to which part each link connects. The controllers used in the FRM are also not PID controllers that have variations in the target values. Instead they are wireless GT-SUITE controllers that are used to achieve target values set in various cases of the model.
Hence these are the various ways in which the FRM model operates. This is how the build up of the FRM model is also illustrated in tutorial 9.
We start from the step 1 in the tutorial which explains a fully functioning detailed model. This model is systematically converted into an FRM model by eliminating the unnecessary extra volumes such as the inlet and exhaust pipes and manifolds etc. Likewise, step by step, each part of the model is being simplified into combination of volumes where the physical attributes are calculated accordingly.
As we can see, by step 8, many volumes like intercooler and EGR have also been discretized effectively to an FRM state.
RESULTS
This is the results for a single case from the FRM model we built for the given configurations. It is clear from the time of the periods and the simulation time taken that, FRM approach is way faster than the detailed approach.