Ideal Isothermal Analysis

Below you can enter data characterizing four different types of Stirling engines and obtain results concerning the performance of your engine almost instantaneously. You also will obtain information about optimizing the phase lag and ratio of the volumes of the compression and expansion space. The computations to achieve this are performed by a javascript based program simulating the physics of the engine based on the isothermal analysis model.

Regardless of the type of engine to be analyzed, you - as the user - have to provide the volumes the working gas occupies in the different subspaces of the engine, all in cm³ (1 in³ = 16.387064 cm³). This is straight forward for the heater, regenerator, and cooler section as these volumes are constant and only a single value is needed to describe them. For the compression and the expansion space we need two values each. As the expansion space is identical for all engine types we start here. As the expansion piston moves between its two extreme position the surface facing the working gas sweeps out a volume called the swept volume which is equal to the difference between the largest and the smallest volume of the expansion space. The smaller of these two volumes is called the clearance volume.
The definitions for these two volumes, swept volume and clearance volume, is applied equally to the compression space and nothing more needs to be said about the alpha-type engine. For the beta- and gamma-type some clarification is needed.

For beta- and gamma-type engines the term swept volume refers to the volume change of the compression space due to the motion of the compression piston only, as if the displacer remains at a fixed position.
The clearance volume refers to the volume of the compression space when - in the figures below - the displacer is at its lowest and the compression piston at its highest position. For the beta-type engine this - in principle - can be a negative value because the motion of the displacer and the power piston is phase shifted such they never reach their respective extreme positions simultaneously.

---- Good luck ----

Engine Type ( alpha, beta, gamma , delta )
Gas ( choose one of : air, H2, He, CH4, CO2 )
Average pressure [kPa]
Temp in heater [K]
Temp in cooler [K]
Volume Phase Lag [°]
Clearance volume, compression space [cm³]
Swept volume, compression space [cm³]
Clearance volume, expansion space [cm³]
Swept volume, expansion space [cm³]
Kooler volume [cm³]
Regenerator volume [cm³]
Heater volume [cm³]

(Sample engine)

In case of a Delta-Type engine you should enter a zero for the size of your kooler, regenerator, and heater volume, respectively. If you don't, the program does not care and in essence you are just doing a Gamma-type engine.

Note that you may copy and paste to a text-file the content of above entry box from which you can retreive your data at a later point.

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Zig Herzog © 2014
Last revised: 12/07/14