Mailing List flyrotary@lancaironline.net Message #35054
From: Ed Anderson <eanderson@carolina.rr.com>
Subject: Re: [FlyRotary] Re: EM2 Data Logger pix
Date: Tue, 2 Jan 2007 22:49:21 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Ok, somebody has to be first to take a stab at it.  How about this:
 
 Assuming the temperature measurement difference between CC and Rad-In are not an artifact of difference between  the two sensors or their installation....
 
 
Note that  the temperature divergence coincides with increased fuel flow,increased power, and increased rpm.  That means the coolant pump rpm has approx doubled following the engine rpm increase from approx 3000 to around 6700 rpm. The  Rad -n temp divergence higher than CC might be a results of better heat transfer to that sensor as it is further down stream than CC sensor.  This better heat transfer is a results of more even mixing of the coolant fluid stream heat load further away from the engine (pump).  We know that turbulence increases heat transfer over laminar (or less turbulent flow).  So (speculating is so much fun!) my hypothesis is that the second sensor is getting more heat transferred to it due to the increased time for better mixing of the heat load of the coolant fluid.  So the average heat transfer to that sensor is higher than the upstream sensor operating in a less well-mixed/heat distributed flow.
 
Note as the rpm is rapidly decreased, the red and yellow line once again approach each other.
 
There!  I'm going to bed.
 
Great information and data to ponder on those days when it is too nasty to fly.
 
Ed
 
----- Original Message -----
Sent: Tuesday, January 02, 2007 9:43 PM
Subject: [FlyRotary] Re: EM2 Data Logger pix

 
The JPEG is about 2 minutes of engine monitor data (from a 1 hour log).  I'd post the entire Excel spreadsheet itself but 6 meg is way too much for up/download. The X axis is in Time (seconds) and Y is the value.  Note that some of the parameters (like rpm and fuel flow) are scaled so they fit the Y scale of the chart
 
 A few details about flight conditions so the data can be placed in context.   The chart starts with the plane at minimum power for level flight (MPLF) at around 1500 ft with all temperatures and pressures stabilized.   The throttle is opened to max (notice that fuel flow goes from 3 gph to ~18 gph) and the airspeed climbs to ~150 mph.  The plane was then pitched up into a climb at Vx to see worst case cooling conditions.  WOT is maintained for about 1 minute then reduced to MPLF again.
 
Most of the chart is self explanatory but there are a few interesting and (to me) mystifying points.  Note the L. Rad Air Out temperature (air temp after passing through rad).  According to Paul L., the optimum for this parameter is 10 - 20 deg F. above ambient OAT.  I wanted a lot more than that to minimize the number of CFM required and as you can see, mine is running as much as 127 deg F above OAT which is even more than I figured on. 
 
The real mystery is the comparisons between rad inlet temp, rad outlet temp and C.C. coolant temp (coolant temp measured right after passing both rotor combustion chambers).  In a 2nd gen 13B the CC coolant temp is the hottest coolant in the engine because it normally cools slightly after passing through the cooler intake port side of the engine.  This is the rad inlet temperature.  As you can see, the CC temp and rad inlet temp start out the same.  When the power is increased, the rad inlet temp climbs faster and higher than CC in the Renesis.  I assume this is caused by the increased heat picked up from the longer exhaust ports.  It is the amount that surprises me.  Study the temp differentials between these three temps and see if you can see the mystery and make sense of this.
 
The Chart is pretty crowded even after I eliminated several parameters for this jpeg but when viewing it in Excel, it is very easy to see and identify all the data.  Moving the mouse pointer to any point of any parameter pops up a little tag showing what the item is and the exact digital value at that point in time.
 
Tracy


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