Date of Award

August 2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Engineering

First Advisor

Ryoichi S Amano

Committee Members

Deyang Qu, Johann R Strickler, Ilya V Avdeev, Arsenio A Pacheco

Keywords

Biomass, Gas Turbines, Gasification, Jet in Cross Flow, Pyrolysis, Thermochemical

Abstract

The importance of gas turbine blades is to convert the thermal energy into shaft work output, which makes the turbine blades are one of the critical components of the gas turbines. Besides the mechanical stresses caused by the centrifugal force and the fluid forces, the thermal stresses arise because of the temperature gradient within the blade materials. This paper aims to have a uniform circumferential temperature field at the combustor exit, consequently reducing the thermal stresses caused by the non-uniform temperature distribution along the turbine blade. The validation of the simulation results with the experiments showed an acceptable agreement with available experimental data. The agreement includes the uniformity factor and the normalized mixture fraction at two different flowrates.Furthermore, sixteen cases studies have been implemented to study the effect of changing Internal Guide Vanes location, concerning the test section holes and the primary stream. The results show that the best location of the Internal Guide vanes is to be placed on the large holes of the dilution section with a 30o angle to the primary stream direction. This method gives 25% higher in thermal uniformity compared to attach them to the small holes. Compared to different orientations, it provides 14% higher regarding the thermal uniformity. Another location of the guide vanes, External Guide Vanes, was experimentally and numerically tested. The results show that the external guide vanes with a 30o orientation gave the most uniform temperature flow for the two different flow rates. Compared to the internal guide vanes with the same orientation, the external guide vanes gave a 7.5% higher uniformity factor and 2% lower pressure drop. The main reason for this result is that the external guide vanes direct the cold stream to penetrate the dilution zone with an angel enhance the swirling effect which are the main factors for excellent mixing, while the pressure drop is lower as the external guide vanes are facing the lower flowrate which is the secondary stream. Another advantage of the external guide vanes over the internal ones is that they are subjected to less thermal stresses as they are facing the cold flow. Furthermore, the external guide vanes are reachable and easy to maintain compared to the internal guide vanes. Finally, the combustor outer surface design has been investigated. Four different angles have been tested numerically and experimentally with a maximum error of 5% at two different Reynolds numbers. Designing the outer combustor surface with a 45-angle bend can give a more uniform temperature distribution of 37% higher than the basic design with only a 0.5% higher pressure drop. Moving to biomass, different thermochemical conversion processes on different biomass species were presented. The results show it is recommended to use the lowest heating rate to allow a quasi-equilibrium state through slow heating, hence avoiding measurement errors. Chicken manure, thermal degradation of the three main components of the chicken manure was obtained. The initial results show that for the slow heating rates, 5oC/min, the thermal degradation of the cow manure is different compared to that one obtained from chicken manure. The Hemicellulose decomposition took place at 250oC and 300oC for the chicken manure and cow manure, respectively. The Cellulose decomposition was started at 300oC for chicken manure and 470oC for cow manure. Gasification, all reactions were endothermic when CO2 used as a gasifying agent. Consequently, the energy must be supplied in terms of heating to sustain the reaction while air gasification was exothermic, which means that the reaction can be sustained without external heating where the self-ignition was observed between 450oC - 600oC. In addition, it was observed that carbon dioxide had the most complicated mechanism with four stages. The cow manure as well has been tested for gasification using the air and CO2 as gasifying agents. At the same temperatures of pyrolysis process the breakup of the hemicellulose and cellulose has occurred 302 oC and 500 oC while the lignin thermal degradation occurred at 745 oC. The 5 oC/min heat rate shows the best results in terms of keeping a very stable exothermic reaction compared to the other heating rates. The CO2 gasification for the cow manure shows poor results (endothermic reactions). This means that the carbon dioxide cannot be used with the cow manure as a gasifying agent since it needs a lot of energy to generate syngas. CO-Pyrolysis, results show the 40%RH-60%CH decreasing the energy of activation by 12% compared to Chicken manure. In addition, an increase in the conversion greater than 3% was achieved. The 40% CM-60%CH shows a positive result in terms of keeping an exothermic reaction over the Co-Pyrolysis process. Finally, CO-gasification, air is used as a gasifying agent, of the cow manure with the sheep manure has been investigated to show that the blend mixture of 20% sheep manure and 80% cow manure give the highest exothermic reaction among all other cases.

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