variable geometry compressor mapping

[Nickinge]

hi to all, I am a graduate in mechanical engineering at the faculty of bologna, I just enrolled in this forum, and to tell the truth I do not know if I will find what I look for because from what I understood the forum is more focused on the mechanical design to the computer, but I still try to ask a hand:

I have a project concerning an over-charged marine diesel engine, and I'm making it using the gt-power program (what do you know? ).
I have already done all my calculations and have already made a model that satisfies me enough with its behavior to the higher rotation regimes, where the engine will work for much of its use. I introduced a turbocharger that I had to map by viewing the online catalogs of garret. Of course, I have the problem of turbo-lag at the lowest regimes, so I have to introduce a variable geometry turbocharger. I know already what type of operation must have at the low systems, because at the moment I have made two models of the same engine, but with 2 different turbos, one for operation at low speeds and one for operation at high speeds.

my doubt is this: how to map such a turbo? In the sense, mapping can be customized in any way by the designer or I have to expect to find something similar to the normal operating maps of a compressor with the return islands, rotation regime lines, axes with mass flow rates and compression ratio etc. Unfortunately I still know little about this type of compressors, they were not subject to study and online is found little, at least in Italian, at the moment I am checking if I find something in English.
would you also tell me a good online catalog where to find this type of engines?



Thank you for your attention!

 

[paulpaul]

Hi.

These are the normal maps that describe the operation of a turbine: Reduced expansion/return/return/number of specific turns that are tracked for different positions of the turbine distributor's operating organ (e.g. 20-40-60-80-100% of the end of the race).
in its time I had faced a modeling problem in the time domain of a diesel overcharged with this type of turbo, and I had given the specific maps of the turbine from the turbo manufacturer (curves not available on commercial catalogs). the compressor map is unique (I don't think it also has the variable geometry stator like the turbine).

I don't know how gt-power works even if I've heard of it often: in simulink I had created, starting from these maps, lookup tables for the turbine, for the compressor and a block for the dynamic simulation of the group. in practice:

- turbine
entrances: expansion ratio, number of turns, % distributor command
outputs: fumes flow, power developed to the tree

- compressor
entrances: compression ratio, number of turns (obviously equal to that of the turbine)
output: air flow, power absorbed into the shaft

- dynamic
inputs: power developed by the turbine, power absorbed by the compressor, inertia of the rotating masses (however, given of the turbo manufacturer)
output: group number of turns

I hope I helped you.
Hi.