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Experimental laboratory research was performed to study the effect of test section width on the magnitude of acoustic resonance generated in a small pitch ratio staggered tube bank. Three different test section widths were studied: 505mm, 714mm, and 953mm. The results for acoustic resonance were compared to the tube bank data of Blevins and Bressler (1993, J. Sound Vib., 164(3), pp. 503–533), Ziada, Bolleter, and Chen (1984, ASME Symposium on Flow-Induced Vibrations, ASME, New York, Vol. 2, pp. 227–242); Ziada, Oengören, and Buhlmann (1989, J. Fluids and Struct., 3, pp. 293–324), and Fitzpatrick and Donaldson (1977, ASME J. Fluids Eng., 99, pp. 681–686). The present study showed that test-section width may be a significant factor in determining the maximum acoustic pressures generated by the flow. In particular, the simple relationship between maximum acoustic pressure and input energy parameter derived by Blevins and Bressler was not a reliable predictor for the array studied and will likely underpredict the maximum acoustic pressures in the lower modes of practical heat exchangers.

Seven burner/furnace systems, three of which vibrated and four of which did not vibrate in operation are evaluated for thermoacoustic oscillations. The evaluation is based on the Rijke and Sondhauss models representing the combined burner/furnace (cold/hot) thermoacoustic systems. Frequency differences between the lowest vulnerable furnace acoustic frequencies in the burner axial direction and those of the systems’ Rijke and Sondhauss frequencies are evaluated to check for resonances. Most importantly, the stability of the Rijke and Sondhauss models is checked against the published design stability diagram of Eisinger (1999, “Eliminating Thermoacoustic Oscillations in Heat Exchanger and Steam Generator Systems,” ASME J. Pressure Vessel Technol., 121, pp. 444–452) and Eisinger and Sullivan (2002, “Avoiding Thermoacoustic Vibration in Burner/Furnace Systems,” ASME J. Pressure Vessel Technol., 124, pp. 418–424). It is shown that thermoacoustic oscillation can be well predicted by the published design stability diagram with the vibrating cases falling into the unstable zone above the stability line and the nonvibrating cases congregating in the stable zone below the stability line. The evaluation suggests that the primary criterion for predicting thermoacoustic oscillations is the stability of the thermoacoustic system and that frequency differences or resonances appear to play only a secondary role. It is concluded, however, that in conjunction with stability, the primary criterion, sufficient frequency separation shall also be maintained in the design process to preclude resonances. The paper provides sufficient details to aid the designers.

Burner/furnace systems are generally sensitive to thermoacoustic vibration due to the presence of large temperature differentials between the cold burner air and the hot furnace gases. The systems are predicted to vibrate when the temperature ratio between the hot and cold components reaches a critical value and when the acoustic mode shape of the combined system develops into a Rijke or a Sondhauss tube type. Original full-scale large-utility steam generator systems which vibrated in operation and modified systems resisting the vibration are described and explained. Guidelines for designing systems resistant to thermoacoustic vibration are also given to aid the designers.