scholarly journals Thermodynamic Analysis and Process System Comparison of the Exhaust Gas Recirculated, Steam Injected and Humidified Micro Gas Turbine

Author(s):  
Usman Ali ◽  
Carolina Font Palma ◽  
Kevin J. Hughes ◽  
Derek B. Ingham ◽  
Lin Ma ◽  
...  

Stringent environmental emission regulations and continuing efforts to reduce carbon dioxide (CO2) from the energy sector, in the context of global warming, have promoted interest to improve the efficiency of power generation systems whilst reducing emissions. Further, this has led to the development of innovative gas turbine systems which either result in higher electrical efficiency or the reduction of CO2 emissions. Micro gas turbines are one of the secure, economical and environmentally viable options for power and heat generation. Here, a Turbec T100 micro gas turbine (MGT) is simulated using Aspen HYSYS® V8.4 and validated through experimental data. Due to the consistency and robustness of the steady state model developed, it is further extended to three different innovative cycles: (i) an exhaust gas recirculated (EGR) cycle, in which part of the exhaust gas is dried and re-circulated to the MGT inlet; (ii) a steam injected (STIG) cycle, and (iii) a humid air turbine (HAT) cycle. The steam and hot water are generated through the exhaust of the recuperator for the STIG and HAT cycle, respectively. Further, the steam is directly injected into the recuperator for power augmentation, while for the HAT cycle; the compressed air is saturated with water in the humid tower before entering the recuperator. This study evaluates the impact of the EGR ratio, steam to air ratio, and water to air ratio on the performance and efficiency of the system. The comparative potential for each innovative cycle is assessed by thermodynamic properties estimation of process parameters through the models developed to better understand the behavior of each cycle. The thermodynamic assessment indicates that CO2 enrichment occurs for the three innovative cycles. Further, the results indicate that the electrical efficiency increases for the STIG and HAT cycle while it decreases for the EGR cycle. In conclusion, the innovative cycles indicates the possibilities to improve the system performance and efficiency.

Author(s):  
Hannah Seliger-Ost ◽  
Peter Kutne ◽  
Jan Zanger ◽  
Manfred Aigner

Abstract The use of biogas has currently two disadvantages. Firstly, processing biogas to natural gas quality for feeding into the natural gas grid is a rather energy consuming process. Secondly, the conversion into electricity directly in biogas plants produces waste heat, which largely cannot be used. Therefore, a feed-in of the desulfurized and dry biogas to local biogas grids would be preferable. Thus, the biogas could be used directly at the end consumer for heat and power production. As biogas varies in its methane (CH4) and carbon dioxide (CO2) content, respectively, this paper studies the influence of different biogas mixtures compared to natural gas on the combustion in a FLOX®-based six nozzle combustor. The single staged combustor is suitable for the use in a micro gas turbine (MGT) based combined heat and power (CHP) system with an electrical power output of 3 kW. The combustor is studied in an optically accessible atmospheric test rig, as well as integrated into the MGT system. This paper focuses on the influence of the admixture of CO2 to natural gas on the NOX and CO emissions. Furthermore, at atmospheric conditions the shape and location of the heat release zone is investigated using OH* chemiluminescence (OH* CL). The combustor could be stably operated in the MGT within the complete stationary operating range with all fuel mixtures.


Author(s):  
Caterina Brandoni ◽  
Gabriele Comodi ◽  
Leonardo Pelagalli ◽  
Flavio Caresana

The paper reports on the performance analysis of cogenerative and trigenerative plants based on Micro Gas Turbines. The core of the system is a natural-gas-fuelled Turbec T100 operating on a regenerated open-air cycle. A code specifically developed by the authors to simulate the micro gas turbine in cogeneration plants, and already checked against experimental data, has been upgraded to simulate the unit’s behavior when facing also a cooling demand (trigenerative case). For this purpose the model of a water-LiBr single-effect absorption chiller driven by hot water has been used. The analysis cover all the unit’s application range and represent a start for its economic evaluation.


2021 ◽  
Author(s):  
Thomas Krummrein ◽  
Martin Henke ◽  
Timo Lingstädt ◽  
Martina Hohloch ◽  
Peter Kutne

Abstract Micro gas turbines are a versatile platform for advanced cycle concepts. In these novel cycles, basic micro gas turbine components — compressor, turbine, combustor and recuperator — are coupled with various other technologies to achieve higher efficiency and flexibility. Examples are hybrid power plants integrating pressurized fuel cells, solar receivers or thermal storages. Characteristically, such complex cycles contain vast pressurized gas volumes between compressor and turbine, many times larger than those contained in conventional micro gas turbines. In fast deceleration maneuvers the rotational speed of the compressor drops rapidly. However, the pressure decrease is delayed due to the large amount of gas contained in the volumes. Ultimately, this can lead to compressor flow instability or surge. To predict and mitigate such instabilities, not only the compressor surge limit must be known, but also the dynamic dependencies between shaft speed deceleration, pressure and flow changes within the system. Since appropriate experiments may damage the system, investigations with numerical simulations are crucial. The investigation begins with a mathematical explanation of the relevant mechanisms, based on a simplified analytical model. Subsequently, the DLR in-house simulation program TMTSyS (Transient Modular Turbo-System Simulator) is used to investigate the impact of transient maneuvers on a micro gas turbine test rig containing a large pressurized gas volume in detail. After the relevant aspects of the simulation model are validated against measurement data, it is shown that the occurrence of compressor instabilities induced by fast deceleration can be predicted with the simulator. It is also shown that the simulation tool enables these predictions using only measurement data of non-critical maneuvers. Hence, mitigation strategies are derived that allow to estimate save shaft speed deceleration rate limits based on non-critical performance measurements.


Author(s):  
Yastuti Rao Gautam

Micro gas turbines are an auspicious technology for power generation because of their small size, low pollution, low maintenance, high reliability and natural fuel used. Recuperator is vital requirement in micro gas turbine unit for improve the efficiency of micro turbine unit . Heat transfer and pressure drop characteristics are important for designing an efficient recuperator. Recuperators preheat compressed air by transfer heat from exhaust gas of turbines, thus reducing fuel consumption and improving the thermal efficiency of micro gas turbine unit from 16–20% to 30%. The fundamental principles for optimization design of PSR are light weight, low pressure loss and high heat-transfer between exhaust gas to compressed air. There is many type of recuperator used in micro gas turbine like Annular CWPS recuperator , recuperator with involute-profile element , honey well , swiss-Roll etc . In this review paper is doing study of Heat transfer and pressure drop characteristics of many types recuperator.


Author(s):  
Homam Nikpey Somehsaraei ◽  
Mohammad Mansouri Majoumerd ◽  
Mohsen Assadi

As a renewable energy source, biogas produced from anaerobic digestion seems to play an important role in the energy market. Unlike wind and solar, which are intermittent, gas turbines fueled by biogas provide dispatchable renewable energy that can be ramped up and down to match the demand. If post-combustion carbon capture systems are implemented, they can also result in negative CO2 emissions. However, one of the major challenges here is the energy needed for CO2 chemical absorption in post-combustion capture, which is closely related to the concentration of CO2 in the exhaust gas upstream of the capture unit. This paper presents an evaluation of the effects of biogas and exhaust gas recirculation use on the performance of the gas turbine cycle for post-combustion CO2 capture application. The study is based on a combined heat and power micro gas turbine, Turbec T100, delivering 100kWe. The thermodynamic model of the gas turbine has been validated against experimental data obtained from test facilities in Norway and the United Kingdom. Based on the validated model, performance calculations for the baseline micro gas turbine (fueled by natural gas), biogas-fired cases and the cycle with exhaust gas recirculation have been carried out at various operational conditions and compared together. A wide range of biogas composition with varying methane content was assumed for this study. Necessary minor modifications to fuel valves and compressor were assumed to allow the engine operation with different biogas composition. The methodology and results are fully discussed in this paper.


Author(s):  
David Sánchez ◽  
Miguel Rollán ◽  
Lourdes García-Rodríguez ◽  
G. S. Martínez

Abstract This paper presents the preliminary design and techno-economic assessment of an innovative solar system for the simultaneous production of water and electricity at small scale, based on the combination of a solar micro gas turbine and a bottoming desalination unit. The proposed layout is such that the former system converts solar energy into electricity and rejects heat that can be used to drive a thermal desalination plant. A design model is developed in order to select the main design parameters for two different desalination technologies, phase change and membrane desalination, in order to better exploit the available electricity and waste heat from the turbine. In addition to the usual design parameters of the mGT, the impact of the size of the collector is also assessed and, for the desalination technologies, a tailored multi-effect distillation unit is analysed through the selection of the corresponding design parameters. A reverse osmosis desalination system is also designed in parallel, based on commercial software currently used by the water industry. The results show that the electricity produced by the solar micro gas turbine can be used to drive a Reverse Osmosis system effectively whereas the exhaust gases could drive a distillation unit. This would decrease the stack temperature of the plant, increasing the overall energy efficiency of the system. Nevertheless, the better thermodynamic performance of this fully integrated system does not translate into a more economical production of water. Indeed, the cost of water turns out lower when coupling the solar microturbine and Reverse Osmosis units only (between 3 and 3.5 €/m3), whilst making further use the available waste heat in a Multi Effect Distillation system rises the cost of water by 15%.


Author(s):  
Martina Hohloch ◽  
Jan Zanger ◽  
Axel Widenhorn ◽  
Manfred Aigner

For the development of efficient and fuel flexible decentralized power plant concepts a test rig based on the Turbec T100 micro gas turbine is operated at the DLR Institute of Combustion Technology. This paper reports the characterization of the transient operating performance of the micro gas turbine by selected transient maneuvers like start-up, load change and shut-down. The transient maneuvers can be affected by specifying either the electrical power output or the turbine speed. The impact of the two different operation strategies on the behavior of the engine is explained. At selected stationary load points the performance of the gas turbine components is characterized by using the measured thermodynamic and fluid dynamic quantities. In addition the impact of different turbine outlet temperatures on the performance of the gas turbine is worked out. The resulting data set can be used for validation of numerical simulation and as a base for further investigations on micro gas turbines.


Author(s):  
J. S. Campbell ◽  
P. C. Malte ◽  
S. de Bruyn Kops ◽  
I. Novosselov ◽  
John C. Y. Lee ◽  
...  

This paper describes a cycle analysis study on the use of the staged prevaporizer-premixer injector (SPP) in high-pressure gas turbine systems fired with liquid fuel. A review of the SPP is given, including discussions of its operational concepts and previous research. The main portions of the paper consist of analyzing the use of the SPP in three different gas turbine systems: a steam-injected gas turbine (STIG) engine, a Frame H gas turbine in combined cycle, and a reheat gas turbine in combined cycle. Focus is placed on determining the effect of the SPP on cycle efficiency. In addition, SPP use in an engine conventionally recuperated by heat exchange from the exhaust gas stream to the compressor discharge air is examined. The SPP offers the potential of low NOx emissions for liquid-fired gas turbines. Because water injection is a method currently practiced for the reduction of NOx, simulations of engines without the SPP but with water injection into the combustor are also performed and comparisons are made. The simulation process is described, as are methods of how the SPP is implemented into the various engines. Results of the study are given, showing the effect of SPP use on cycle efficiency. In general, except for application to the conventionally recuperated engine, use of the SPP causes a decrease in cycle efficiency of around 1–3 percent (relative). The impact of water injection is somewhat greater, causing a 2.5–4 percent (relative) decrease in cycle efficiency. Further, the water injection does not provide as much NOx control as the lean prevaporized-premixed combustion.


Author(s):  
Hannah Seliger-Ost ◽  
Peter Kutne ◽  
Jan Zanger ◽  
Manfred Aigner

Abstract The use of biogas has currently two disadvantages. Firstly, processing biogas to natural gas quality for feeding into the natural gas grid is a rather energy consuming process. Secondly, the conversion into electricity directly in biogas plants produces waste heat, which largely cannot be used. Therefore, a feed-in of the desulfurized and dry biogas to local biogas grids would be preferable. Thus, the biogas could be used directly at the end consumer for heat and power production. As biogas varies in its methane (CH4) and carbon dioxide (CO2) content, respectively, this paper studies the influence of different biogas mixtures compared to natural gas on the combustion in a FLOX®-based six nozzle combustor. The single staged combustor is suitable for the use in a micro gas turbine (MGT) based combined heat and power (CHP) system with an electrical power output of 3kW. The combustor is studied in an optically accessible atmospheric test rig, as well as integrated into the MGT system. This paper focuses on the influence of the admixture of CO2 to natural gas on the NOx and CO emissions. Furthermore, at atmospheric conditions the shape and location of the heat release zone is investigated using OH* chemiluminescence (OH* CL). The combustor could be stably operated in the MGT within the complete stationary operating range with all fuel mixtures.


Author(s):  
Peter L. Meitner ◽  
Anthony L. Laganelli ◽  
Paul F. Senick ◽  
William E. Lear

A semi-closed cycle, turboshaft gas turbine engine was assembled and tested under a cooperative program funded by the NASA Glenn Research Center with support from the U.S. Army. The engine, called HPRTE (High Pressure, Recuperated Turbine Engine), features two distinct cycles operating in parallel; an “inner,” high pressure, recuperated cycle, in which exhaust gas is recirculated, and an “open” through-flow cycle. Recuperation is performed in the “inner,” high pressure loop, which greatly reduces the size of the heat exchanger. An intercooler is used to cool both the recirculated exhaust gas and the fresh inlet air. Because a large portion of the exhaust gas is recirculated, significantly less inlet air is required to produce a desired horsepower level. This reduces the engine inlet and exhaust flows to less than half that required for conventional, open cycle, recuperated gas turbines of equal power. In addition, the reburning of the exhaust gas reduces exhaust pollutants. A two-shaft engine was assembled from existing components to demonstrate concept feasibility. The engine did not represent an optimized system, since most components were oversized, and the overall pressure ratio was much lower than optimum. New cycle analysis codes were developed that are capable of accounting for recirculating exhaust flow. Code predictions agreed with test results. Analyses for a fully developed engine predict almost constant specific fuel consumption over a broad power range. Test results showed significant emissions reductions. This document is the first in a series of papers that arc planned to be presented on semi-closed cycle characteristics, issues, and applications, addressing the impact of recirculating exhaust flow on combustion and engine components.


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