Gas Turbines in Cogeneration: Overall Analysis and Numerical Predictions (original) (raw)

Thermodynamic evaluation of gas turbines for cogeneration applications

International Journal of Exergy, 2009

In this paper, the first and second laws of thermodynamics have been utilised to evaluate the performance of intercooled reheat regenerative gas turbine cogeneration plant. The effects of overall pressure ratio, cycle temperature ratio, pressure losses, and process steam pressure on energetic and exergetic efficiencies have been investigated. The results indicate that most of the exergy destructions occur in the Combustion Chamber, which represent about 70% of total exergy destruction in the overall system. The compressor and gas turbine losses are shown to have a relatively small influence on system performance parameters. Energetic efficiencies decrease with increase in process steam pressure, but the exergetic efficiency is constant with the same.

Exergy Efficiency Optimization for Gas Turbine Based Cogeneration Systems

Volume 6A: Energy, 2013

Energy degradation can be calculated by the quantification of entropy and loss of work and is a common approach in power plant performance analysis. Information about the location, amount and sources of system deficiencies are determined by the exergy analysis, which quantifies the exergy destruction. Micro-gas turbines are prime movers that are ideally suited for cogeneration applications due to their flexibility in providing stable and reliable power. This paper presents an exergy analysis by means of a numerical simulation of a regenerative micro-gas turbine for cogeneration applications. The main objective is to study the best configuration of each system component, considering the minimization of the system irreversibilities. Each component of the system was evaluated considering the quantitative exergy balance. Subsequently the optimization procedure was applied to the mathematical model that describes the full system. The rate of irreversibility, efficiency and flaws are highlighted for each system component and for the whole system. The effect of turbine inlet temperature change on plant exergy destruction was also evaluated. The results disclose that considerable exergy destruction occurs in the combustion chamber. Also, it was revealed that the exergy efficiency is expressively dependent on the changes of the turbine inlet temperature and increases with the latter.

Thermodynamic analysis of a regenerative gas turbine cogeneration plant

2010

Design methodology has been developed for parametric study and thermodynamic performance evaluation of a gas turbine cogeneration system (GTCS). Parametric study showed that compression ratio (r p), inlet air temperature, turbine inlet temperature, steam pressure and pinch point temperature played a very vital role on overall performance of GTCS. Exergy analysis revealed that most sensitive components in GTCS were combustion chamber and regenerator.

THERMODYNAMIC ANALYSIS OF GAS TURBINE COGENERATION POWER PLANTS

Cogeneration cycles have many advantages over the conventional cycles. In this study, the performances of the simple and the air preheated cogeneration cycles are compared with each other. To calculate the enthalpy and entropy values of the streams, a computer program written by the author in FORTRAN codes is used. Exergy analysis is done for the simple and the air preheated cogeneration cycles. The results present that by changing the compression rate from 6 to 16, the electric power increases about 20 %, but the heat power decreases about 11 % for the simple cycle. By changing excess air rate from 1.3 to 3.5, the decrease of the heat power and the heat exergy power are about 20 % for the simple cycle at compression rate 6. Increasing compression ratio increases the exergetic efficiency for the two cycles. Maximum efficiencies are obtained about 2 and 2.5 excess air rates for the simple cycle. For the air preheated cycle increasing excess air rates increases the exergetic efficiency.

THERMODYNAMIC ANALYSIS OF RECUPERATED GAS TURBINE COGENERATION CYCLES

Cogeneration cycles have better advantages over the conventional cycles. In this study, the performances of the recuperated cogeneration cycles are analyzed. For the calculation of the enthalpy and the entropy values of the streams, a computer program written by the author in FORTRAN codes is used. Exergy analysis is done for the air-fuel preheated cogeneration cycle. The results present that by changing the compression rate from 6 to 16, the electric power increases about 20-40 %, but the heat power decreases about 10-30 % for the air-fuel preheated cycle. The decrease of the heat power is about 20-40 % for the air-fuel preheated cycle at compression rate 6 by changing excess air rate from 1.3 to 3.5. Increasing compression ratio increases the exergetic efficiency for the cycle. For the air-fuel preheated cycle increasing excess air rates increases the exergetic efficiency.

Thermo-environmental Analysis of Recuperated Gas Turbine-Based Cogeneration Power Plant Cycle

Arabian Journal for Science and Engineering, 2015

Two of the most prominent techniques to improve energy conversion efficiency of a gas turbine-based combined heat and power plant are the use of "recuperation" and "cogeneration". Thermodynamic and environmental analysis of this type of cycle has been reported in the article. Exergy analysis of the proposed recuperated gas turbine-triple pressure Rankine combined cycle has been presented in comparison with traditional basic gas turbine-based combined cycle. Analysis of emission of oxides of nitrogen from power plant based on the proposed cycle has been carried out to estimate its environmental impact. The results of exergy analysis show a higher gas turbine rational efficiency = 37.32 % in case of recuperated gas turbine-combined cycle as compared to 34.41 % for basic gas turbine-combined cycle configuration due to a relative decrease in fuel requirement. Results also show that power-to-heat ratio and cogeneration energy efficiency of recuperated gas turbine cogeneration configuration is 0.8246 and 56.28 % respectively, while cogeneration exergy efficiency for basic gas turbine-based cycle has been found to be 47.67 % and power-to-heat ratio is 0.6749. Emission of oxides of nitrogen from the proposed cycle has been observed to increase with increase in compression pressure ratio and has been found to be around 5.30 g/kg of fuel at compressor pressure ratio of 23. Keywords Cogeneration • Recuperation • Power-to-heat ratio • Cogeneration energy efficiency • Cogeneration exergy efficiency • NO x Acronyms AFC Air film cooling BGT Basic gas turbine B3PR Basic gas triple pressure reheat steam combined cycle layout CHP Combined heat and power GT Gas turbine HRSG Heat recovery steam generator RcGT Recuperated gas turbine ST Steam turbine

Efficiency improvement of gas turbine cogeneration systems

Tehnicki vjesnik - Technical Gazette, 2017

Original scientific paper 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.

Optimization of Gas Turbine Cogeneration Systemfor Various Heat Exchanger Configurations

Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, 2011

-Optimisation des systèmes de turbine à combustion en cogénération pour différentes configurations des échangeurs de chaleur-Cet article explore et compare les performances des trois configurations de systèmes de turbine à combustion permettant la production combinée de chaleur et d'électricité, sur la base du cycle irréversible régénératif de Brayton-Joule. Le modèle proposé est développé pour deux contraintes différentes sur le cycle, notamment le flux de chaleur produit par combustion imposé ou la température maximale du cycle imposée. Le modèle considère également l'irréversibilité due au frottement dans le compresseur et la turbine et celle due aux pertes de chaleur dans la chambre de combustion et les échangeurs de chaleur. Le rendement au sens du premier principe du système sans et avec cogénération et le rendement exergétique rendent compte des avantages de la cogénération, et aident le concepteur à choisir la meilleure configuration de turbines à combustion en fonction de ses besoins. Des données expérimentales d'une microturbine opérationnelle ont été utilisées pour valider le modèle. La puissance fournie et les rendements au sens du premier principe et exergétique sont optimisés par rapport à un ensemble de paramètres de fonctionnement. Les valeurs optimales des paramètres du moteur à turbine à combustion qui correspondent au maximum de puissance fournie, respectivement au maximum de rendement thermodynamique sont discutées. Les résultats montrent que la plupart des performances maximales correspondent aux mêmes valeurs optimales du taux de compression pour le flux imposé, sauf le rendement exergétique maximum qui demande des valeurs plus élevées du taux de compression que celles pour le maximum du flux d'exergie. Une comparaison des performances de ces trois configurations et les perspectives sont proposées.