Page 22 – Resist Temptation – Equilibrillate!

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It is all too easy to look at the scatter of data points on the chart,
and edit out the ones you don’t like!!

No! Do not “doctor” the data.

Never, never, never” – to quote the Reverend Doctor Ian Paisley
(But I don’t think he was talking about scientific honesty)

All these data points are real. They are measurements of what actually happened.

The whole point of taking measurements is to quantify and understand what is happening.

So, those points describe something that is going on. Find out what.

Plotting the same data against time, it becomes very clear.

It takes time for the engine to warm up!

To reach thermal equilibrium.

There is no point in trying to draw a power curve UNTIL the engine has reached steady state.

Yes, it can be as long as 30 minutes.
It varies with how much metal there is in the engine and how strong, or weak, the burner is.

When starting a Stirling it is essential to prevent the engine from over revving.

The technique is, as the revs start to rise, to slowly increase the load.
And keep the revs relatively steady

Take readings as you go, say every minute. When the revs no longer rise and you get
three readings the same, the engine is now ready to start measuring the power curve.

But charting the data for only the first 30 minutes - see what happened.
The line on the chart shows the time sequence. The engine started, bottom left
on the chart and progressed, zig-zag fashion, upwards as time, progresses.