Analysis of unsteady gas temperature measurements in the appendix gap of a Stirling engine

Sauer, Jan; Kuehl, Hans-Detlev

doi:10.2514/6.2017-4795

Cited by 1 publication

(5 citation statements)

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“…The readings obtained from probe a -and to a lesser extent also those from probe b -are severely disturbed by turbulent vortices entering the open end of the gap with the inflowing gas from the hot cylinder volume. Considering the velocity ratio 𝛤𝛤 at this position, it can be demonstrated that these actually penetrate up to the position of probe b approximately [21].…”

Section: Experimental Investigation Of the Appendix Gap Lossmentioning

confidence: 88%

“…Considering that the hydrodynamic entry length in laminar flow may extend to more than 50 times the hydraulic diameter, this assumption will probably apply to a small section around the center of the gap only, if at all. So, Sauer and Kühl performed experimental investigations to verify the predictions by the analytical model [20,21]. For this purpose, an experimental machine was used, the design of which had been downsized to laboratory scale by application of similarity-based scaling rules [22].…”

Section: Experimental Investigation Of the Appendix Gap Lossmentioning

confidence: 99%

“…4: Photograph of the tip of a fine-wire thermocouple probe deployed to capture gas temperature profiles in the appendix gap Fig. 5: Schematic cross section of the hot cylinder of the laboratory-scale machine indicating the thermocouple positions [21] and was spot-welded onto the tips of two solid support wires consisting of the corresponding thermocouple alloys. These are embedded in a ceramic sleeve and may be adjusted axially by a micrometer head.…”

Section: Experimental Investigation Of the Appendix Gap Lossmentioning

confidence: 99%

“…Exemplary gas temperature readings vs. crank angle obtained by the four probes at the positions shown in Fig.5in Stirling mode operation of the laboratory-scale machine[21] …”

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confidence: 99%

“…Fig.7: Exemplary plots of the corrected experimental gas temperatures vs. the radial position in the gap for the four probe positions according to Fig.5in Stirling mode operation of the laboratory-scale machine, in comparison to the analytically predicted curves[21] …”

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confidence: 99%

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Appendix gap losses in Stirling engines – review of recent findings

Kühl

Sauer

2021

E3S Web Conf.

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The appendix gap loss in Stirling cycle machines is generated by the annular gap around the thermally insulating, thin-walled dome typically attached to a piston or displacer plunging into the hot cylinder volume of an engine or the cold volume of a cryocooler. It was considered to be of minor importance for decades. Thus, simplified analytical models were considered sufficiently accurate for its description, until numerical simulations and experimental results gave rise to a more detailed analysis revealing that, neglecting entrance and end effects, the flow is typically laminar, but unsteady. Subsequently, an enhanced analytical model accounting for fluidic and thermal inertia effects as well as the volumetric displacement by the seal was developed. Compared to the previous ones, this model predicts a shift of the optimum width to smaller values, a higher minimum overall loss and furthermore, an option to decrease the loss by reducing the effective seal diameter. This could be experimentally confirmed as well as the unsteady gas temperature profiles predicted by this model. Subsequently, both theoretically and experimentally founded correlations for the radial and axial energy transport in the gap were derived and implemented in a differential simulation of the gap within a third order code.

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Section: Experimental Investigation Of the Appendix Gap Lossmentioning

confidence: 88%

Section: Experimental Investigation Of the Appendix Gap Lossmentioning

confidence: 99%

Section: Experimental Investigation Of the Appendix Gap Lossmentioning

confidence: 99%

“…Exemplary gas temperature readings vs. crank angle obtained by the four probes at the positions shown in Fig.5in Stirling mode operation of the laboratory-scale machine[21] …”

mentioning

confidence: 99%

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confidence: 99%

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