Hercules Engines

"B2431" wrote in message
...
From: Jim Yanik
Date: 1/16/2004 6:53 PM Central Standard Time
Message-id:

"John R Weiss" wrote in
news:Sp%Nb.73504$nt4.98595@attbi_s51:

"Phil Miller" wrote...

Yes really, on every jet engine TIT is Total Inlet Temperature.

Yep.

I ask because I came across an interesting paragraph in the T56-A-15
service manual yesterday. Went like this...

...measures the turbine inlet temperature by means of
thermocouples...Eighteen thermocouple assemblies are mounted in the
turbine inlet casing of each engine...One thermocouple of each
assembly is connected to the turbine inlet temperature indicating
system, and...one...is connected to the electronic datum control
system. The 18 indicating system thermocouples are connected in
parallel [!!] by the indicator turbine thermocouple harness assembly,

I'm surprised you ever doubted the truth on this one!


So, let's revise.

That's going a bit too far... Nobody can revise the Tarver
Chronicles! :-)


bimetallic thermocouples generate millivolt signals,and paralleling them
would not work.Standard practice is to series-connect them,and compare to
a
reference junction.Do these assemblies include signal processing to
convert
the mV signal to a digital form,which could then be sent on a parallel
bus?

--
Jim Yanik
jyanik-at-kua.net

On every aircraft I ever worked on thermocouples were in parallel if there
were
two or more.

Dan, U.S. Air Force, retired

Dan, we went through this early last year I think it was and Tarver was
shown to be wrong as per normal. On T56 engines the thermocouples are
connected in parallel and pick up TIT, the signal is then averaged. They
are averaged due to the non-uniform temperatures that occur at the turbine
inlet due to the short time of spraying fuel from the nozzle, to fuel
ignition, to introducing the hot gasses at high velocity to the turbine
inlet. The hot gases are not completely mixed and so there are some
stratifications of hotter and cooler areas at the turbine inlet. The
temperature averaging function of the parallel thermocouple circuits
compensates for these non-uniform temperatures.

Scet