Stirling engine PV diagram measured in real time
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- Опубликовано: 18 сен 2024
- This video describes and demonstrates the real-time measurement of a Stirling engine's pressure versus volume diagram.
Kontax Stirling Engines: www.stirlingen...
Additional resources
- PV diagram: • Stirling Engine & PV-d...
- PV diagram with friction: • Stirling Engine & PV-d...
- Stirling engine instrumentation: cmps-people.ok...
- Stirling engine PV diagram and refrigeration: aapt.scitation... and arxiv.org/abs/...
So what's the power output?
The work done per cycle is determined by the area of the loop in the PV-diagram. Roughly speaking, with no friction applied to the flywheel, the change in volume is about 0.5 cm^3 and the change in pressure is about 1.2 kPa. Therefore, the area/work is approximately W = 0.6 mJ. In reality, the work is a little less because the PV-diagram is not rectangular. The power output is given my P = W/T, where T is the period of cycle. Without friction, the period is approximately T = 0.2 s such that the power output is about 3 mW = 4 micro-horsepower!
When friction is applied, the work per cycle increases and the power output decreases. The power decreases because the period of the cycle increases more than the work per cycle.
Am i understanding correctly that the volume of the engine is calculated externally? looked like you were using a sensor to add value of the volume depending on flywheel positioning.
you explained it in the part of the video i skipped over, sorry
Is it correct to assume zero pressure on the graph represents atmospheric pressure, therefore when a negative (below 0) pressure is indicated that would represent an internal working fluid pressure lower than the outside atmospheric pressure?
Yes, that is correct. The pressure sensor measures the difference between the pressure outside the engine (atmospheric pressure) and the pressure of the gas inside the engine, which can be greater than or less than atmospheric pressure.
@@jakebobowski3165 Thank you. Is there any possible way to also take temperature readings? It is difficult to understand how, in an enclosed heated space containing an expanding hot gas, the internal pressure can drop below the outside atmospheric pressure, unless there is a concomitant drop in temperature. But is there any thermocouple, or other instrument, with a fast enough response time to measure the actual gas temperature in real time?
@@peoplesresearchcenter6184 It's probably difficult to get a direct measurement of the gas temperature. However, you could deduce what it must be using the ideal gas law and knowledge of the instantaneous pressure and volume (PV = nRT). You would have to estimate the number of moles of gas contained inside the engine using the internal volume and the density of the air.