flyrotary@lancaironline.net Mailing List Archive

Steve,

The figure below shows delta T's for a flight in January. The OAT was in the neighborhood of 40 deg F which is warmer than normal for here that time of year. The delta T's may still be useful. Not much time was spent on the ground as indicated by the times when the TAS is zero. The times of interest to you are probably from 9 to 10 minutes with the run up and from 68 minutes to shut down.

The heat exchanger configuration was an underbelly scoop containing a coolant radiator and an oil to coolant heat exchanger. A second coolant radiator was located in the cowl plumbed in series with the scoop radiator but the air inlet to this second radiator was closed. That is why the coolant delta T for this radiator is close to zero the entire time. There were no thermostats installed.

The oil delta T through the oil to coolant heat exchanger is negative during warm up since the oil is being heated by the coolant. The oil to coolant heat exchanger coolant delta T is negative after warm up since the coolant is being heated by the oil.

Data is collected with a Dynon D10 EMS equipped with EGT and CHT thermocouples for a six cylinder engine. Those thermocouples are used for temperature measurements other than EGT or CHT.

Figures for individual heat exchangers and flight conditions will follow in separate messages.

Steve Boese

RV6A, 1986 13B NA, RD1A, EC2

From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of steve Izett <flyrotary@lancaironline.net>
Sent: Friday, November 25, 2016 4:42:53 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Oil and water delta temps

Hi guys
I thought I should provide an update.

Our final ground testing has been interrupted by a dead battery and a fuel leak.
With these fixed we were able to weight the aeroplane to check CofG and do a longer run to check idle temps in the warmer weather.

With an OAT of mid 80’s F I started her up and after 30 mins at ~1700RPM I switched her off when the water leaving the engine hit 220F.
One mystery I’m pondering. Having run out of sensor inputs on the Dynon Skyview Engine Monitor I put a switch into the oil and water senders so I can read either oil & water temps into the exchangers or out.
Now when I put the switch in the circuit the wires weren’t marked so I had a 50/50 chance of getting the in and out right on the DPDT.
So on next engine run realised that I got them wrong. In one position I read oil out and Water in, and vice versa.
I’ll have to switch a couple wires next time I’m soldering in the cockpit.

But here’s the mystery. As temps rose, at some point when I switch between in/out temps, they now both read higher in one switch position and lower in the other position!
How can that be?
Now the water circuit doesn’t have a thermostat while the RX7 turbo oil cooler does.
Can anyone provide some helpful logic?
Also, can any of you provide figures for your water and oil delta temps on the ground? What do you get across your coolers?

On another note I was really pleased to see the Empty Weight come in on the low side.
The CG close to the forward limit.

Getting close to first flight.

Cheers
Steve Izett
Glasair Super II RG Renesis 4 port, RD1C 2.85:1, EC3, EM3