Efficiency improvement of gas turbine cogeneration systems

U radu se procjenjuje osam metoda za poboljšanje učinkovitosti kogeneracijskog ciklusa plinske turbine. Tim se metodama povećava temperatura ulaznog zraka plinske turbine, rashlađuje ulazni zrak kompresora, predgrijava zrak, predgrijava gorivo, povećava tlak ulaznog zraka kompresora, povećava brzina viška zraka, ubrizgava para i vlaži ulazni zrak kompresora. Te se metode istražuju kako bi se usporedilo njihovo djelovanje na performanse sustava. Učinci tih metoda na egzergetsku učinkovitost ovise o vrsti kogeneracijskog ciklusa. Kombiniranjem metoda rekuperacije, predgrijavanja goriva i ubrizgavanja pare može se postići visoka učinkovitost. Kombinirane metode daju najbolje rezultate kod različitih potreba tržišta za toplinom. Odgovarajućom kombinacijom metoda za poboljšanje učinkovitosti može se povećati egzergetska učinkovitost za oko 20 %. Rezultati pokazuju da se metode za poboljšanje učinkovitosti moraju primijeniti zajedno kada je god to moguće.In this study eight methods are evaluated for a gas turbine cogeneration cycle to improve the efficiency. These methods are increasing gas turbine inlet air temperature, cooling the inlet air of the compressor, air preheating, fuel preheating, increasing compressor inlet air pressure, increasing air excess rates, steam injection, and humidification of the inlet air of the compressor. These methods are studied in order to compare their effects on the performance of the systems. The effects of these methods on the exergetic efficiency depend on the kind of the cogeneration cycle. By combining recuperation, preheating fuel and steam injection methods high efficiency can be achieved. The combined methods give the best results under variable heat demands of the market. An appropriate combination of the efficiency improvement methods may increase the exergetic efficiency about 20 %. The results show that efficiency improvement methods must be applied together whenever it is possible

Analysis of Steam Injection into Combustion Chamber of Gas Turbine Cogeneration Cycles

Cogeneration is known as the generation of heat energy and electricity at same time by using the fuel's energy. There are various cogeneration systems, and steam injection is made into combustion chamber to increase the efficiency of the cycle and to reduce nitrogen oxide emissions. The most fundamental thermodynamic, operational, economical and thermo-economic factors must be considered when choosing the appropriate cogeneration system and designing the system. For the thermodynamic factors, such as the amount of fuel to be consumed, the electric heat rate, the artificial thermal efficiency, the fuel energy gain rate must be found for the unit amount of electric power to be obtained. The cost and availability of the fuel to be used must also be estimated by considering the problems will be affected by repair maintenance and economic fluctuations. In economic factors, the annual cash flow of the system and the amortization itself are calculated. In the thermo-economic factors, the investment costs depend on the exergy efficiency and the exergy of the products of the devices and the fuel required to operate are calculated. In this study, the analysis of steam injection into cogeneration systems according to performance and evaluation criteria was done using energy, exergy and economic methods. To calculate the energy and exergy values of the flows, a program was written by the authors in the FORTRAN programming language and the results obtained by running them were used. The results obtained were compared with the literature values and correctness was observed

Thoermodynamic Analyses of Steam Injected Gas Turnine Cogeneration Cycles

In this study, air preheating, air-fuel preheating and simple cycles where steam injected in to combustion chamber are analyzed. The effects of steam injection on thermodynamic performance are calculated and obtained for the three different gas turbine cogeneration systems. Simulation programs written by the authors in FORTRAN code are obtained for the analyses by applying the first law of thermodynamics and the exergy analysis method. Thermodynamic performance of these three different cycles for variable mass of injected steam and different stages are obtained and compared with the results of the literature. The effects of injection steam into combustion chambers of those three cycles for variable compressing ratios, on power, efficiencies and performance are obtained. Consequently, the advantages and the disadvantages of injection steam are evaluated and all results of this study are compared with the literature. Injection steam into combustion chamber increases the electricity power and the electricity efficiency but decreases the heat power of the cycles

GAZ TÜRBİNLİ KOJENERASYON TESİSLERİNİN PERFORMANS ANALİZLERİ

Bu çalışmada, gaz türbinli kojenerasyon çevrimlerinin geliştirilmesinde kullanılan bazı yöntemler basit bir kojenerasyon çevrimi üzerinde uygulanmıştır. Bu yöntemler havanın ön ısıtılması, hava ve yakıtın ön ısıtılması ve giriş havasının evaporatif ve absorpsiyonlu soğutma ile soğutulmasıdır. Bu kojenerasyon sistemleri enerji verimi (enerji kullanım faktörü), ekserji verimi, elektrik ve ısı gücü, elektrik ısı enerjisi oranı, yapay termal verim ve yakıt enerjisi kazanım oranı yönünden değerlendirilmiş ve birbirleri ile karşılaştırılmışlardır. Bu analizlerde basınç oranı, hava-yakıt kütleleri oranı ve çevrimlerin kompresör giriş sıcaklıkları gibi termodinamik parametreler kullanılmıştır. Bu parametrelerin en çok etkili olanından en az etkili olanına göre, hava-yakıt kütleleri oranı, basınç oranı ve kompresör giriş sıcaklıkları şeklinde sıralandığı anlaşılmıştır. Ayrıca daha çok elektrik ve daha az ısıl güç yönünden en verimli çevrimin hava-yakıt ön ısıtmalı çevrim ve daha çok ısıl güç daha az elektrik gücü için basit çevrimin en uygun çevrim oldukları ortaya çıkarılmıştırIn this study, some improving methods of gas turbine cogeneration cycles are applied on a simple cogeneration cycle. These methods are preheating air, preheating air and fuel, inlet air cooling by using evaporative cooling and absorption cooling. These cogeneration systems are evaluated with respect to energy efficiency (energy utilization factor), exergetic efficiency, electric and heat power, electric-heat energy rate, artificial thermal efficiency and fuel energy saving ratio and are compared with each other. In these analyses, the thermodynamic parameters such as compressing ratio, air and fuel mass ratio and compressor inlet temperatures of the cycles are used. It is concluded that these parameters can be listed from most effective to least effective as air fuel ratio, pressure ratio and compressor inlet temperature. It is also concluded that the most efficient cycle is found to be the air-fuel preheated cycle for obtaining more electric power and less heat power, and the simple cycle is the most suitable one for obtaining more heat power and less electric powe

Exergy analyses of two and three stage cryogenic cycles

Cryogenics has an important influence on industry and science. In this study, optimum working conditions are obtained by applying exergy analysis and local optimization methods to two- and three-stage vapor compression cascade cryogenic cycle. The first and second laws of thermodynamics, exergy analysis, and local optimization methods are applied to the two- and three-stage cascade cryogenic cycle. By considering the needs and demands, it is possible to create new cycles by adding new devices and/or new stages to these cycles. The results of the optimum operating conditions are obtained for the two- and three-stage vapor compression cascade cryogenic cycle. It is seen that to achieve high COP values and high efficiency; it is necessary to reduce the compression ratio of the compressor as much as the fluid allows. For the two-stage cycle, the minimum total work required for cryogenic cooling is around P 7 = 2,400 kPa. The COP value is 0.30 between P 7 = 2,400 and 2,800 kPa, and the maximum exergy efficiency is obtained around 0.235. It is seen operating the first-stage compressor at high pressures increases the total losses of the entire cycle from 7,500 to 18,550 kW. The increase in total exergy losses is around 247%, and operating the first-stage compressor at high pressures increases the exergy efficiency of the entire cycle. The increase in total exergy efficiency is around 160%. When the second-stage compressor is operated at low pressure, the COP value increases by 2%, the exergy efficiency increases by 20%, and the exergy losses decrease by around 40%

TAM SAYILI PROGRAMLAMA MODELİ İLE OTOBÜS ÇİZELGELEME OPTİMİZASYONU VE UYGULAMASI

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