04

FlO. 9.23. Input motoring power to small Stirling air engine ns a lunction of mean operating pressure at lour different speeds and with engine cylinder at ambient temperatures.

Tinginc speed (rpm) Engine speed (rpm)

(a) Mechanical friction loss vs speed (b) Gaseous pumping power vs speed

Tinginc speed (rpm) Engine speed (rpm)

(a) Mechanical friction loss vs speed (b) Gaseous pumping power vs speed

Fid. 9.2'«. Mechanical friction and gaseous pumping power of small Stirling air engine as a function of engine speed and mean pressure.

power required to drive the engine as a function of operating pressure at four different speeds.

The motoring power shown in Fig. 9.23 is the combined total of the mechanical friction and the gaseous pumping work necessary to overcome the aerodynamic-friction and the positive-displacement work.

A possible interpretation of these results is as follows. For each constant speed condition the motoring power curve (Fig. 9.23) has been extrapolated to the zero mean pressure axis. The motoring power at zero pressure was then assumed to be the mechanical-friction work of the engine. This was plotted in Fig. 9.24(a) and was found to be a strong function of engine speed. The mechanical-friction work was assumed to be independent of the mean pressure, so the balance between total motoring power and mechanical friction was attributed to the gaseous pumping work. This balance is plotted in Fig. 9.24(b) and can be seen to be a function mainly of pressure (and hence density) and, to a lesser extent, engine speed.

By reference to Fig. 9.21 it can be seen that the brake output at 1400 revolutions per minute with an operating pressure of 1.2 MN/m? (12.41 bar) was 0.42 k\V (0.57 hp). At a similar speed and pressure condition, the motoring power required, shown in Fig. 9.23, was 0.34 kW (0.46 hp). Therefore, the indicated power of the engine was approximately 0.42 +

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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