Twotikes@aol.com wrote:

Here's the model in Excel 5.0 Format.  There's actually two models.  One with
a wastegate and one with a fixed leak.  Basic instructions are given in the
forms.  Both use the built in Excel "solver".  All values in green are user
entries.  You must have some knowledge of the 13B characteristics to get
anything useful out of the models.  You have to put in reasonable values for
EGT, BSFC, A/F ratio for instance.  It is up to the user to adjust EGT if A/F
is changed, etc.  It is also up to the user to adjust BSFC for RPM and A/F.
If you have no clue then leave them alone.  Turbine efficiency is a big
unknown based on operating condition and blowdown effectiveness.  70% is a
middle of the road guess.  It will only get worse for no blowdown but may be

100% (indicated) if good blowdown recovery exists.  Sometimes the solver

will choke on rapid changes i.e. changing sea level baro to 30K baro in one
step.  Sometimes changing rapidly will also cause division by zero or
something.  If either happens enter a new value (closer to correct) in the
changing cell (blue on leak model) and run solver again.  Sometmes it takes
several tries to get the solver to converge.  Once you have convergence if
you want to check the compressor efficiency from the charts and enter a
closer value you can do so and then run solver again.  Every time you change
any green cell you must run solver again before reading any valid results!
Have fun!  I look forward to some feedback.

Jeff Spitzer

 
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