Optimization of Tehrmodynamic Cycles

本研究旨在找出各种热力循环的最佳工况。我们研究的循环是以Kalina循环为底循环的联合循环、HAT循环和回收液化天然气（LNG）冷能的复合动力循环。得出了各循环的最佳工况，并与传统的燃气涡轮机和朗肯循环的联合循环进行了性能比较。计算中所用的燃料是燃料，我们假定开式布雷顿循环燃烧室出口温度为800 ~ 1400 ℃，卡林纳循环的其它参数是排气流量比与底循环工质的压力、底循环涡轮机入口氨的压力和浓度有关。HAT循环的参数为燃烧室空气比、加湿器出口温度和冷却空气流量 ...更多信息 作为涡轮机。以Kalina循环为底的联合循环在热源温度较低时性能较高，而在热源温度较高时性能下降。与传统燃气涡轮机循环相比，HAT循环提高了效率，减少了NO_x的排放。最后，本文研究了一种以海水为热源，LNG为冷源的R-13和天然气的复合动力循环。经过R-13循环的LNG被海水加热并在两个天然气涡轮机中膨胀。结果表明，R-13循环所作的功是天然气循环的一半，增加R-13循环的功可以提高联合循环的总效率，减小高压冷凝器中R-13与天然气的温差可以提高联合循环的效率。少

The present study is to find out the optimum condition of various thermodynamic power cycles. The cycles we examined are the combined cycle which uses Kalina cycle as a bottoming cycle, HAT cycle and a composite power cycle to recover cold energy of liquefied natural gas (LNG). We obtained an optimum operating condition for each cycle and compared their performance with those of conventional combined cycle by gas turbine and Rankine cycle.Pure methane (CH4) was the fuel in all calculations covered and we assumed that the exit temperature of combustion chamber in open Brayton cycle ranges from 800 to 1400ﾟC.Other parameters for Kalina cycle are the ratio of flow rate of exhaust gas in topping cycle to that of working fluid in bottoming cycle, the pressure and concentration of ammonia at the inlet of turbine in bottoming cycle. On the other hand, for HAT cycle, the parameters are the air ratio in combustion chamber, the exit temperature of humidifier and the flow rate of cooling air in g … More as turbine. The amount of NO_x in each condition was obtained.The combined cycle by Kalina cycle as the bottoming brings higher performance when the temperature of heat source is relatively low, while its performance decreases when the temperature of heat source is higher. The HAT cycle enhances efficiency with less NO_x emission compared with the conventional gas turbine cycle.Finally, we examined a composite power cycle by R-13 and natural gas to recover cold energy of LNG.The R-13 cycle uses seawater as the hot heat source and LNG as the cold source. The LNG passing through R-13 cycle is heated by seawater and expands in two natural gas turbines. The parameters are the system pressure and the ratio of flow rate of R-13 to LNG.The result shows that the work produced by R-13 cycle is a half of the natural gas cycle, the increase in work by R-13 cycle will bring higher total efficiency of the combined cycle and the cycle effectiveness can be raised by decreasing the temperature difference between R-13 and natural gas in the high pressure condenser. Less