Dynamic measurements on an airfoil using acoustic forcing

Abstract only

Dynamic measurements on an airfoil using acoustic forcing

Abstract only

Marine impact on liquefaction processes

In the last decade the interest for liquefied natural gas (LNG) is growing. A tendency is to produce and transport LNG on large floating vessels. One important choice in designing such a vessel is the liquefaction process. Several processes have been developed in recent years, ranging from mixed refrigerants processes, cascade processes and expander processes. Using knowledge and experience from onshore LNG liquefaction plants, the different processes can be rated to the relevance for offshore operations. Little quantitative information is available in the open literature and therefore a large number of questions remain open. TNO, a Dutch contract research, technology development and consultancy organization, has started an investigation of the rationale with respect to offshore functionalities like small footprint, efficiency, flexibility and robustness, safety, availability, and sensitivity to ship motions. The most promising candidates are the nitrogen expander processes for small capacities and the single or dual mixed refrigerant processes. The latter two processes are more sensitive to ship motions, mainly due to the type of heat exchanger (spiral wound heat exchanger). Tilting the spiral wound heat exchanger lead to a significant maldistribution of the cooling liquid on the shell side

Forces on bends and T-joints due to multiphase flow

To be able to assess the mechanical integrity of piping structures for loading to multiphase flow conditions, air-water experiments were carried out in a horizontal 1" pipe system. Forces and accelerations were measured on a number of bends and T-joint configurations for a wide range of operating conditions. Five different configurations were measured: a baseline case consisting of a straight pipe only, a sharp edged bend, a large radius bend, a symmetric T-joint and a T-joint with one of the arms closed off. The gas flow was varied from a superficial velocity of 0.1 to 30 m/s and the liquid flow was varied from 0.05 to 2 m/s. This operating range ensures that the experiment encompasses all possible flow regimes. The magnitude of the measured forces was found to vary over a wide range depending on the flow regime. For slug flow conditions very high force levels were measured, up to 4 orders of magnitude higher than in single phase flow for comparable velocities. The annular flow regime resulted in the (relative) lowest forces, although the absolute amplitude is of the same order as in the case of slug flow. In case of slug flow, the measured results can be described assuming a simple slug unit model. For both the frequency and amplitude the available models can be used in assessments. In annular and stratified flow a different model is required, since no slug unit is present. Instead, the amplitude of the excitation force can be estimated using mixture properties. To predict the main frequency for the annular flow and stratified flow additional experiments are required. Copyright © 2010 by ASME

Multiphase fluid structure interaction in bends and T-joints

Air-water experiments were carried out in a horizontal 1" pipe system to measure the magnitude of the forces induced by the multiphase flow. Forces and accelerations were measured on a number of bends and T-joint configurations for a wide range of operating conditions. Five different configurations were measured: a baseline case consisting of straight pipe only, a sharp edged bend, a large radius bend, a symmetric T-joint and a T-joint with one of the arms closed off. The gas flow was varied from a superficial velocity of 0.1 to 30 m/s and the liquid flow was varied from 0.05 to 2 m/s. This operating range ensures that the experiment encompasses all possible flow regimes. In general, the slug velocity and frequency presented a reasonable agreement with classical models. However, for high mixture velocity the measured frequency deviated from literature models. The magnitude of the measured forces was found to vary over a wide range depending on the flow regime. For slug flow conditions very high force levels were measured, up to 4 orders of magnitude higher than in single phase flow for comparable velocities. The annular flow regime resulted in the (relative) lowest forces, although the absolute amplitude is of the same order as in the case of slug flow. These results from a one inch pipe were compared to data obtained previously from similar experiments on a 6mm setup, to evaluate the scaling effects. The results for the one inch rig experiments agreed with the model proposed by Riverin, with the same scaling factor. A modification of this scaling factor is needed for the model to predict the forces measured on the 6mm rig. The validity of the theories developed based on the 6mm experiments were tested for validity at larger scales. In case of slug flow, the measured results can be described assuming a simple slug unit model. In annular and stratified flow a different model is required, since no slug unit is present. Instead, excitation force can be estimated using mixture properties. This mixture approach also describes the forces for the slug regime relatively well. Only the single phase flow is not described properly with this mixture model, as would be expected. Copyright © 2010 by ASME