Research On Gas Turbine System With Cryogenic Exerny Of Liquefied Natural Gas

Liquefied natural gas (LNG) is a kind of clear energy, which will be imported in China. LNG releases a lot of cryogenic exergy during its boiloff, so it is necessary to research on how to utilize it. At the same time, gas turbine total energy system has drawn more attention and gotten wider application in recent years, so it deserves a comprehensive analysis concerning its thermodynamic performance.The main contents of this thesis include:1. Thermodynamic analysis of closed Brayton cycle based on integration of cryogenic exergy of LNG and waste-heat utilizationAt the present time, much waste-heat is discharged and it is difficult to convert it into power because its temperature is not high. In this thesis, a closed Brayton cycle is proposed, in which the supercritical LNG is taken as its cold sink and an industrial waste heat as its heat source. In this thermodynamic system, the heat releasing process in the Brayton cycle is a inconstant temperature process and it matches the process of LNG boiloff well, therefore, the exergy loss in the heat transfer process is reduced. At the same time, waste-heat can be utilized effectively in the system.2. Recuperative gas turbine cogeneration with water injection and its thermodynamic analysisRecuperative gas turbine cogeneration can reduce exhaust temperature, make use of waste heat and increase efficiency. When there are heat consumers nearby, waste heat can be used to heat up hot water to supply the consumers. As a result, output power and efficiency of such system are increased at the same time. In the system, waste heat is used to heat up hot water not steam because there is no phase change and the system is easier to be applied..This thesis gives a fundamental quantitative analysis of the cycle of recuperative gas turbine cogeneration with water injection and mainly discusses the influence of water injection ratio and pressure ratio on the specific power and the amount of heating. At the same time, using the total energy efficiency and the equivalent exergy efficiency as the evaluation criterion, this thesis also discusses the influence of the water injection ratio and pressure ratio on the performance of this cycle.3. Algebraically explicit analytical solutions of two-buoyancy natural convection in porous mediaApplying the approach of separating variables with addition, the thesis derives three sets of simple and clear algebraically explicit analytical equations describing the natural convection in porous media with both temperature and concentration gradients. Besides the theoretical meaning, they are more valuable for be the benchmark solutions to check and improve the computational fluid dynamics and computational heat and mass transfer. Since the derived expressions are very simple, various typical curvedrawings are omitted to save space.