The Evaporative Gas Turbine Pilot Plant has been in operation at Lund Institute of Technology in Sweden since 1997. In this cycle low-grade heat in the flue gases is utilized for water evaporation into the compressed air in the humidification tower. This result in, amongst others, power augmentation, efficiency increase and lower emissions. This article presents the experimental and theoretical results of the humidification tower, in which simultaneous heat and mass transfer occurs. A theoretical model has been established for the simultaneous heat and mass transfer occurring in the humidification tower and it has been validated with experiments. The humidification tower in the pilot plant can be operated at several operating conditions. An after-cooler makes it possible to chill the compressor discharge air before entering the humidification tower. The saturation temperature of the incoming compressed air can thereby be varied from 62 to 105 °C at the operating pressure of 8 bar(a). It has been shown that the air and water can be calculated throughout the column in a satisfactory way. The height of the column can be estimated with an error of 10% compared with measurements. The results from the model are most sensitive of the properties of the diffusion coefficient, viscosity and thermal conductivity due to the complexity of the polar gas mixture of water and air.
Ethanol from bio-products has become an important fuel for future power production. However, the present production technology is rather expensive. This paper focuses on how to lower the production cost of ethanol extraction from mash, and to use the ethanol as a primary fuel in gas turbines for heat and power production. Today, ethanol is produced during distillation by supplying energy to extract the ethanol from the mash. Using the evaporation process in the evaporative gas turbine to extract the ethanol from the mash before the distillation step, a lot of energy can be saved. In the evaporation process, the ethanol is extracted directly from the mash using energy from low-level energy sources. The evaporation technology is therefore expected to reduce the cost for the ethanol production. Simultaneous heat and mass transfer inside the ethanol humidification tower drives a mixture of ethanol and water into the compressor discharge air. To investigate the evaporation of a binary mixture into air at elevated pressures and temperatures, a test facility was constructed and integrated into the evaporative gas turbine pilot-plant. The concentration of ethanol in the mash is not constant but depends on the sugar content in the feedstock used in the fermentation process. Tests were therefore conducted at different concentrations of ethanol in the ethanol-water mixture. Tests were also performed at different temperature and flow conditions to establish the influence of these parameters on the lower heating value of the produced low calorific gas. It has been shown that this technology extracts about 80% of the ethanol from the mash. It has also been shown that the composition of the resulting gas depends on the temperatures, flow rates and composition of the incoming streams. The tests have shown that the produced gas has a lower heating value between of 1.8 to 3.8 MJ/kg. The produced gas with heating values in the upper range is possible to use as fuel in the gas turbine without any pilot flame. Initial models of the ethanol humidification process have been established and the initial test results have been used for validating developed models.
For the materials in modern gas turbines to survive, a considerable amount of cooling is required. In cases where large amounts of heat need to be removed, impingement cooling with its high heat transfer coefficients may be a good alternative. The possibilities of enhancing impingement cooling by introducing surface enlarging/turbulence enhancing elements are examined experimentally in this work. A technique using thin foil heaters combined with an infrared camera is used. Local temperature distribution on the target plate is measured, enabeling to separately evaluate the Nusselt number enhancement for different areas. Experiments are conducted for four different area enlarging geometries: triangle, wing, cylinder and dashed rib all made from aluminum. Comparison between each area enlarged surface and a flat plate is made in terms of Nusselt number and also pumping power in order to maximize the cooling efficiency. Overall Nusselt number enhancement factors compared to impingement on a flat plate show values of 1 to 1.3, the trend decreasing with increased jet-to-plate distance and Reynolds number. When normalizing by the spent pumping power the enhancement factors drop to 0.4 to 1.2 compared to impingement on a smooth plate. The best results were achieved with die rib geometry and when not using a too large value of enlarger height compared to jet-to-plate distance. Row-wise evaluation of Nusselt number enhancement shows an increased enhancement factor with row number and therefore crossflow ratio (Gc/Gj). The infrared camera pictures reveal that the enhancement is found in three different areas, on the enlarger base area, the area just downstream the enlarger and in diagonal streaks with increased turbulence generated by the enlargers. Tests using an enlarger material with heat conductivity scaled to represent actual gas turbine conditions show that only the enlarger base area is affected when decreasing the enlarger heat conductivity. The result is a small decrease in total Nusselt number enhancement.
Modelling and data-normalization of a gas turbine process, called Evaporative Gas Turbine (EvGT) is studied here. The most important factor to achieve a high level of accuracy during the data normalization, is the consideration of changes in thermodynamic properties of the working medium at different environmental conditions. Performance of the EvGT, which is working with a mixture of air and steam, is strongly affected by the changes in the environmental conditions. When the properties of the working fluid such as the water content are continuously changing, the normalization process using conventional techniques becomes very difficult if not impossible. In this study, measured data from the worlds’ first Evaporative Gas Turbine at Lund University in Sweden have been used for generation of an empirical model by a single Artificial Neural Network system. Performance maps generated by ANN have been successfully used for data normalization and performance prediction of the Evaporative Gas Turbine. ANN predicted values are compared with experimental results, not used during the training, where very good correlation was observed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.