Jabawocky
oggers, you are simply not correct....Time to put your glasses on, figure 8 clearly shows that statement is false.
NACA-754 Figure 8:
Figure 8b.png
Valve temp correlates very well with EGT. What glasses do you recommend to change that fact – beer goggles perhaps. Note the blue line I added where Walter Atkinson wrongly claims peak valve temp occurred is actually outside the range in which the report authors say it occurred.
This same data was repeated in tests done by Lycoming in the 1960's.
I don't doubt that Lycoming have acquired plenty of data for their valves. But they did not draw the conclusion that you and Walter Atkinson have – quote: “EGT does NOT affect valve temperature...valve temperature does NOT track EGT...the two are not in any way related”.
Walter Atkinson:
According to the 1943 NACA report referenced, those who think that valve temp is in any way related to EGT must reconcile the fact that as EGT is going UP from 25dF ROP to peak EGT the valve temperature is going DOWN. This is definitive evidence that the two are NOT related.
You are clutching at straws. Eyeballing the curve from the test with the thermocouple gives a peak valve temp at no more than 10ROP, not your 25ROP and definitely not the 40°ROP you claimed previously.
But that is beside the point. The knowledge that valve temperature is linked to both CHT and EGT is well and truly established in the engineering literature and the publicly accessible data.
reconcile the fact that as EGT is going UP from 25dF ROP to peak EGT the valve temperature is going DOWN
Easy: the spread between where CHT and EGT peak as a function of mixture means the valve temp will not peak precisely at either but between them.
This extract is from a document by Electronics International that is very well referenced throughout:
“
During the exhaust stroke the high velocity of the exhaust gasses and the large surface area of the exhaust valve head cause the exhaust valve to absorb a significant amount of heat. The temperature of the hot exhaust gasses (EGTs) flowing over the valve has a direct affect on the temperature of the exhaust valve. The exhaust valve is heated during two of the four strokes of the engine (power and exhaust strokes). During the exhaust stroke, the valve loses its major cooling path (valve seat face to the seat insert).” http://buy-ei.com/wp-content/uploads...ots-Manual.pdf
Meanwhile you have provided nothing to support the APS hypothesis that “EGT does not affect valve temperature...[and]...exhaust valve temperature is not related to EGT in any way”.