Experimental Investigation of the Impact of Biogas On a 3kW Micro Gas Turbine FLOX®-Based Combustor

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):  
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):  
Homam Nikpey ◽  
Mohsen Assadi ◽  
Peter Breuhaus

Previously published studies have addressed modifications to the engines when operating with biogas, i.e. a low heating value (LHV) fuel. This study focuses on mapping out the possible biogas share in a fuel mixture of biogas and natural gas in micro combined heat and power (CHP) installations without any engine modifications. This contributes to a reduction in CO2 emissions from existing CHP installations and makes it possible to avoid a costly upgrade of biogas to the natural gas quality as well as engine modifications. Moreover, this approach allows the use of natural gas as a “fallback” solution in the case of eventual variations of the biogas composition and or shortage of biogas, providing improved availability. In this study, the performance of a commercial 100kW micro gas turbine (MGT) is experimentally evaluated when fed by varying mixtures of natural gas and biogas. The MGT is equipped with additional instrumentation, and a gas mixing station is used to supply the demanded fuel mixtures from zero biogas to maximum possible level by diluting natural gas with CO2. A typical biogas composition with 0.6 CH4 and 0.4 CO2 (in mole fraction) was used as reference, and corresponding biogas content in the supplied mixtures was computed. The performance changes due to increased biogas share were studied and compared with the purely natural gas fired engine. This paper presents the test rig setup used for the experimental activities and reports results, demonstrating the impact of burning a mixture of biogas and natural gas on the performance of the MGT. Comparing with when only natural gas was fired in the engine, the electrical efficiency was almost unchanged and no significant changes in operating parameters were observed. It was also shown that burning a mixture of natural gas and biogas contributes to a significant reduction in CO2 emissions from the plant.


Author(s):  
Hannah Seliger ◽  
Andreas Huber ◽  
Manfred Aigner

This paper presents a comprehensive experimental investigation of a newly designed single-stage combustion system based on the flameless oxidation (FLOX®) technology for a small scale micro gas turbine (MGT). It is used for a combined heat and power plant (CHP) with an electrical power output of 3 kW, using natural gas as fuel. Flameless oxidation is characterized by a flame distributed over a large volume and a high internal recirculation of flue gas. Considering the high combustor inlet temperatures up to 1000 K as required for this application, the FLOX®-combustion concept offers various advantages compared to swirl-stabilized combustion systems in terms of flashback risk and exhaust gas emissions. This paper describes the detailed characterization of the jet-stabilized combustor. Two versions of the combustor were tested, one generic and one modified version suitable for the integration into the micro gas turbine at an atmospheric test rig with optical access. The stable operating range, including lean blow out (LBO) limits, was determined for varying equivalence ratios, thermal powers and preheat temperatures. The influence of these parameters on the combustion characteristics is discussed. Furthermore, the shape and location of the heat release zone is investigated with OH*-chemiluminescence (OH* CL). The exhaust gas emissions NOx, CO and unburned hydrocarbon (UHC) were also measured. The results demonstrate that the developed combustor design ensures stable and reliable performance. It also offers a high operational flexibility and low pressure loss with NOx, CO and UHC emissions far below regulation limits for all relevant engine conditions.


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.


2019 ◽  
Vol 113 ◽  
pp. 02012
Author(s):  
Martina Hohloch ◽  
Melanie Herbst ◽  
Anna Marcellan ◽  
Timo Lingstädt ◽  
Thomas Krummrein ◽  
...  

A hybrid power plant consisting of a micro gas turbine (MGT) and a solid oxide fuel cell (SOFC) is a promising technology to reach the demands for future power plants. DLR aims to set up a MGT/SOFC hybrid power plant demonstrator based on a 3 kWel MTT EnerTwin micro gas turbine and an SOFC module with an electrical power output of 30 kWel from Sunfire. For the detailed investigation of the subsystems under hybrid conditions two separate test rigs are set up, one in which the MGT is connected to an emulator of the SOFC and vice versa. The paper introduces the set-up and the functionalities of the MGT based test rig. The special features are highlighted and the possibilities of the cyber physical system for emulation of a hybrid system are explained.


Biomass fuel as carbon neutral, abundant, domestic, cost effective is being reconsidered to fuel-up the power plant to produce electricity in clean way. But utilization of biomass fuel directly in existing conventional power plant causes problem in turbine such as erosion, hot corrosion, clogging and depositions [1]. As such combustion of biomass fuel outside the primary cycle eradicates potential hazards for turbine. In such a case indirectly fired micro gas turbine opens a door to biomass fuel as this technology is free from negative aspects of direct combustion as well as making micro gas turbine feasible to generate electricity in small scale at non-grid areas for individual consumer or group of consumers. In this research, the effect of different types of biomass fuel on operating parameters as well as on output electrical power of externally fired micro gas turbine (EFmGT)has been analyzed. The biomass fuels are categorized on the basis of air to fuel ratio (AFR) using stoichiometry combustion theory. It is found from results that parameters like air mass flow rate, compression ratio, heat exchanger effectiveness, turbine inlet temperature, combustion temperature, and temperature difference in heat exchanger affect the performance of EFmGT. Also types of biomass fuel have substantial impacts on these performance parameters as well as on electrical power output of EFmGT cycle.


Author(s):  
Hannah Seliger ◽  
Michael Stöhr ◽  
Zhiyao Yin ◽  
Andreas Huber ◽  
Manfred Aigner

This paper presents an experimental and numerical study of the flow field and heat release (HRL) zone of a six-nozzle FLOX®-based combustor at atmospheric pressure. The 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 velocity field was measured using stereoscopic particle image velocimetry (PIV). The heat release zone was visualized by OH*-chemiluminescence (OH* CL) and the flame front by OH planar laser-induced fluorescence (OH PLIF). The results are compared with CFD simulations to evaluate the quality of the applied numerical turbulence and combustion models. The simulations were performed using Reynolds-averaged Navier-Stokes equations in combination with the k-ω-SST-turbulence model. Since the FLOX®-based combustion is dominated by chemical kinetics, a reaction mechanism with detailed chemistry, including 22 species and 104 reactions (DRM22), has been chosen. To cover the turbulence-chemistry interaction, an assumed probability density function (PDF) approach for species and temperature was used. Except for minor discrapancies in the flow field, the results show that the applied models are suitable for the design process of the combustor. In terms of the location of the heat release zone, it is necessary to consider possible heat losses, especially at lean operating conditions with a distributed heat release zone.


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):  
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):  
Tim Lieuwen ◽  
Vince McDonell ◽  
Eric Petersen ◽  
Domenic Santavicca

This paper addresses the impact of fuel composition on the operability of lean premixed gas turbine combustors. This is an issue of current importance due to variability in the composition of natural gas fuel supplies and interest in the use of syngas fuels. Of particular concern is the effect of fuel composition on combustor blowout, flashback, dynamic stability, and autoignition. This paper reviews available results and current understanding of the effects of fuel composition on the operability of lean premixed combustors. It summarizes the underlying processes that must be considered when evaluating how a given combustor’s operability will be affected as fuel composition is varied.


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