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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 thero moacoustic 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. [ABSTRACT FROM AUTHOR]

Assessment of the local thin area should be undertaken for both tension and compression bending. In this paper, simplified reference stresses for a flaw in a cylinder are proposed. By using these results, a newly developed p-M (internal pressure ratio and external bending moment ratio) diagram which can evaluate the collapse condition for pressure equipment such as vessels, piping, and storage tanks with a local thin area simultaneously subjected to internal pressure p and external bending moment M due to earthquake, etc., is proposed. The p-M line is verified by comparison with the finite element analysis results and the numerous results of experiment for a cylinder with a volumetric flaw obtained through the reference literatures. It was clarified that the differences in collapse limit between the p-M line and DNV guideline under both internal pressure and compression moment became evident where the outer diameter/wall thickness of a cylinder is large and the yield ratio of the material is small. [ABSTRACT FROM AUTHOR]

This paper presents various approaches for finite element modeling of a cylindrical lightweight composite vessel for blast containment purposes. The vessel has a steel liner that is internally reinforced with throttle and gusset steel plates and wrapped with a basalt fiber/epoxy composite. The vessel design is fairly complex, including many geometric details and several components with different material models. The objective of this work is to determine an accurate and efficient procedure for modeling this type of vessels. This model can be used within an iterative optimization process. Different modeling approaches using various combinations of element types, material models, and geometric details are explored. Results of these models are compared to available experimental data. Accuracy and computational time between all these models are also compared. A suitable modeling method is recommended based on these findings. [ABSTRACT FROM AUTHOR]

This paper focuses on the usage of direct route for design by analysis, which is included in the new European standard for unfired pressure vessels (CEN, 2002, "Unfired Pressure Vessels-Part 3: Design," European Committee for Standardization No. EN 13445-3, Current Issue 14-2005). The direct route addresses failure modes directly, having, therefore, advantages in comparison to the traditional method, which is stress categorization. Special attention is given to the progressive plastic deformation design check (PD-DC) with space and time-dependent temperature distribution and the fatigue design check (F-DC) with stress components, which do not vary simultaneously. As a simple demonstration example, a nozzle with cold media injection is used to show how the direct route can be applied in such cases. This example is analyzed with abruptly changing injection temperature, which makes a transient thermal analysis necessary. In the case of the PD-DC, Melan's shakedown theorem and cycling of a finite element model with a linear-elastic ideal-plastic material model are used. In the case of the F-DC, some problems are discussed: One of them is cycle counting in the case of nonproportional loading, and the other one is the use of structural stresses and stress concentration factors. [ABSTRACT FROM AUTHOR]