Numerical Analysis of Biomass-Derived Gaseous Fuels Fired in a RQL Micro Gas Turbine Combustion Chamber: Preliminary Results

Author(s):  
Paolo Laranci ◽  
Edoardo Bursi ◽  
Francesco Fantozzi

The economically sustainable availability of biomass residuals and the growing need to reduce carbon dioxide emissions from power generation facilities has driven the development of a series of processes that lead to the production of a variety of biomass-derived fuels gaseous fuels, such as syngas, pyrolysis gas, landfill gas and digester gas. These technologies can find an ideal coupling when used for fuelling micro gas turbines, especially for distributed power generation applications, in a range between 50 and 500 kWE. This paper features a report on numerical activity carried out at the University of Perugia on a 80 kWE micro gas turbine annular combustion chamber, featuring RQL technology, that has been numerically modeled in order to verify combustion requirements, principally in terms of air/fuel ratio and lower heating value, simulating mixtures with varying chemical composition. The use of CFD turbulence and combustion modeling, via both Eddy Break-up and non-adiabatic PPDF methods, allows us to evaluate flame temperatures and stability, NOx and unburnt hydrocarbons emissions, under various load conditions, for the different fuel mixtures taken into account.

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Saad Alshahrani ◽  
Abraham Engeda

Abstract A performance assessment was conducted for a solar–biogas hybrid micro gas turbine integrated with a solar power tower technology. The considered system is a solar central receiver integrated with a micro gas turbine hybrid with biogas fuel as a backup. The Brayton cycle is designed to receive a dual integrated heat source input that works alternatively to keep the heat input to the system continuous. The study considered several key performance parameters including meteorological condition effects, recuperator existence and effectiveness, solar share, and gas turbine components performance. This study shows a significant reduction in CO2 emissions due to the utilization and hybridization of the renewable energies, solar, and biogas. The study reveals that the solar–biogas hybrid micro gas turbine for 100-kW power production has a CO2 emission less than a conventional fossil fuel gas turbine. Finally, the study shows that the method of power generation hybridization for solar and biogas gas turbines is a promising technique that leads to fuel-savings and lower CO2 emissions.


Author(s):  
A. Cavarzere ◽  
M. Morini ◽  
M. Pinelli ◽  
P. R. Spina ◽  
A. Vaccari ◽  
...  

The application of bio-fuels in automotive, power generation and heating applications is constantly increasing. However, the use of straight vegetable oil (pure or blended with diesel) to feed a gas turbine for electric power generation still requires experimental effort, due to the very high viscosity of straight vegetable oils. In this paper, the behavior of a Solar T-62T-32 micro gas turbine fed by vegetable oils is investigated experimentally. The vegetable oils are supplied to the micro gas turbine as blends of diesel and straight vegetable oils in different concentrations, up to pure vegetable oil. This paper describes the test rig used for the experimental activity and reports some experimental results, which highlight the effects of the different fuels on micro gas turbine performance and pollutant emissions. Moreover, an identification model is set up to predict the behavior of the considered gas turbine, when fuelled by vegetable oil, and the sensitivity of micro gas turbine thermodynamic measurements and emissions is quantitatively established.


Author(s):  
Toshihiko Nakata ◽  
Mikio Sato ◽  
Toru Ninomiya ◽  
Takeharu Hasegawa

Developing integrated coal gasification combined cycle systems ensures cost-effective and environmentally sound options for supplying future power generation needs. The reduction of NOx emissions and increasing the inlet temperature of gas turbines are the most significant issues in gas turbine development in an Integrated Coal Gasification Combined Cycle (IGCC) power generation systems. The coal gasified fuel, which is produced in a coal gasifier of air-blown entrained-flow type has calorific value as low as 1/10 of natural gas. Furthermore the fuel gas contains ammonia when a gas cleaning system is a hot type, and ammonia will be converted to nitrogen oxides in the combustion process of a gas turbine. This study is performed in a 1500°C-class gas turbine combustor firing low-Btu coal-gasified fuel in IGCC systems. An advanced rich-lean combustor of 150-MW class gas turbine was designed to hold stable combustion burning low-Btu gas and to reduce fuel NOx emission that is produced from the ammonia in the fuel. The main fuel and the combustion air is supplied into fuel-rich combustion chamber with strong swirl flow and make fuel-rich flame to decompose ammonia into intermediate reactants such as NHi and HCN. The secondary air is mixed with primary combustion gas dilatorily to suppress the oxidization of ammonia reactants in fuel-lean combustion chamber and to promote a reducing process to nitrogen. By testing it under atmospheric pressure conditions, the authors have obtained a very significant result through investigating the effect of combustor exit gas temperature on combustion characteristics. Since we have ascertained the excellent performance of the tested combustor through our extensive investigation, we wish to report on the results.


2020 ◽  
Vol 10 (6) ◽  
pp. 6422-6426
Author(s):  
A. C. Mangra

The interest in micro gas turbines has been steadily increasing. As a result, attention has been focused on obtaining optimal configurations for micro gas turbines depending on the applications in which they are used. This paper presents the CFD modeling results regarding an annular type combustion chamber, part of an 800N micro gas turbine, predestined to equip a small scale multifunctional airplane. Two configurations have been taken into consideration and 3D RANS numerical simulations have been conducted with the use of the commercial software ANSYS CFX. The liquid fuel droplets were modeled by the particle transport model, which tracks the particles in a Lagrangian way. An initial fuel droplet diameter of 500µm has been imposed. The numerical results obtained are encouraging. The flame was developed in the central area of the fire tube, its walls thus not being subjected to high temperatures. Also, the maximum temperatures were obtained in the primary zone of the fire tube. The temperature then decreased in the fire tube's secondary zone and dilution zone. The numerical results will be validated by conducting combustion tests on a testing rig which will be developed inside the institute's Combustion Chamber Laboratory.


Author(s):  
Chao Zong ◽  
Yaya Lyu ◽  
Desan Guo ◽  
Chengqin Li ◽  
Tong Zhu

Micro gas turbine is one of the ideal prime movers for small-distributed energy systems. It can effectively reduce the emission of greenhouse gases and nitrogen oxides. Moreover, the use of micro gas turbines will contribute to burning fossil fuels in a much cleaner way. The staged combustion technology is the favorite way for low pollution combustion chamber such like. Therefore, the influence of the proportion of pilot fuel in the combustion chamber on pollutant emission deserves further study. The object of this research is the Double annular swirler (Das), which was applied to a 100 kW micro gas turbine combustion chamber. The combustion performance and emission characteristics under different Pilot Fuel Ratios (PFR) were obtained in prototype experimental system. Under the experimental conditions, Computational fluid dynamics (CFD) method was applied to research the reacting flow field and the formation of NOx in the combustion chamber and then analyze the influences of PFRs on combustion process. Experimental results show that the NOx emission of Das decreased at first and then increased with the augment of PFR. When PFR was near to 11%, the per unit NOx emission concentration reached its minimum. The numerical simulation agreed well with the experimental data. Further analysis of the simulation results indicate that there is a strong correlation between Φlocal and NOx concentration. When it is lower than a certain value, the number of nitrogen oxides will be significantly reduced. The value has a lot to do with the inlet air temperature and the pressure of the combustion chamber under the design condition, and it needs to be confirmed by calculating the adiabatic temperature. Simultaneously, we also find that although the percentage of total air flowing into the combustor remains unchanged, the increase of PFR would reduce the airflow ratio in inner swirler. This implies that for some particular combustion chambers, special attention should be paid to the changes in air allocation caused by PFR.


Author(s):  
Maryam Pourhasanzadeh ◽  
Sajjad Bigham

Distributed generation is an attractive way of producing energy, minimizing transport losses and enhancing energy efficiency. Micro gas turbines in distributed generation systems add other advantages such as low emissions and fuel flexibility. In the present work, a 100 kW micro gas turbine is considered. The optimization procedure is done by Genetic Algorithm method which is a new method in optimizing problems. The plant is comprised of an air compressor, recuperator, combustion chamber and gas turbine. The design Parameters of the plant, were chosen as: compressor pressure ratio, compressor isentropic efficiency, gas turbine isentropic efficiency, combustion chamber inlet temperature and the temperature of the combustion gas at the gas turbine inlet. In order to find the design parameters optimally, a thermo-economic approach has been followed. An objective function, representing the total cost of the plant in terms of dollar per second, was defined as the sum of the operating cost, related to the fuel consumption, the capital investment which stands for equipment purchase and maintenance cost. Subsequently, different parts of the objective function have been expressed in terms of design variables. Finally, the optimal values of design variables were obtained by minimizing the objective function using Genetic Algorithm code that is developed in Matlab software programming.


Author(s):  
Paolo Laranci ◽  
Edoardo Bursi ◽  
Francesco Fantozzi

A CFD analysis was carried out to study the performance of a modified combustion chamber of a micro gas turbine with the objective to change its fuelling from natural gas to biomass pyrolysis gas. The micro gas turbine is a component of a pilot IPRP (Integrated Regenerated Pyrolysis Plant), a distributed energy system, based on a rotary kiln reactor for the pyrolysis of biomass. This paper describes the combustion process occurring inside the combustion chamber of the micro gas turbine. In particular, a new, revised kinetic scheme was implemented in the RANS analysis to better reproduce CO oxidation and flue gases temperature, for both methane and pyrolysis gas combustion; further investigation was undertaken on NOx formation mechanisms, which are now modeled through a non-adiabatic PPDF approach, also taking into account the effects of turbulence interaction. CFD simulations for natural gas and pyrolysis gas combustion were performed for two different annular rich-quench-lean combustion chamber configurations, one with the original design for natural gas and one with a modified design optimized for syngas, in order to quantify the advantage of using a dedicated design. Furthermore, through the numerical analysis, the hot spots of the combustor have been identified and monitored the to study the possible effects of material corrosion due to high temperatures.


1996 ◽  
Vol 118 (3) ◽  
pp. 534-540 ◽  
Author(s):  
T. Nakata ◽  
M. Sato ◽  
T. Ninomiya ◽  
T. Hasegawa

Developing integrated coal gasification combined-cycle systems ensures cost-effective and environmentally sound options for supplying future power generation needs. The reduction of NOx emissions and increasing the inlet temperature of gas turbines are the most significant issues in gas turbine development in Integrated Coal Gasification Combined Cycle (IGCC) power generation systems. The coal gasified fuel, which is produced in a coal gasifier of an air-blown entrained-flow type has a calorific value as low as 1/10 of natural gas. Furthermore, the fuel gas contains ammonia when a gas cleaning system is a hot type, and ammonia will be converted to nitrogen oxides in the combustion process of a gas turbine. This study is performed in a 1500°C-class gas turbine combustor firing low-Btu coal-gasified fuel in IGCC systems. An advanced rich-lean combustor of 150-MW class gas turbine was designed to hold stable combustion burning low-Btu gas and to reduce fuel NOx emissions from the ammonia in the fuel. The main fuel and the combustion air are supplied into a fuel-rich combustion chamber with strong swirl flow and make fuel-rich flame to decompose ammonia into intermediate reactants such as NHi and HCN. The secondary air is mixed with primary combustion gas dilatorily to suppress the oxidization of ammonia reactants in fuel-lean combustion chamber and to promote a reducing process to nitrogen. By testing under atmospheric pressure conditions, the authors have obtained a very significant result through investigating the effect of combustor exit gas temperature on combustion characteristics. Since we have ascertained the excellent performance of the tested combustor through our extensive investigation, we wish to report on the results.


Author(s):  
Torsten Methling ◽  
Marina Braun-Unkhoff ◽  
Uwe Riedel

Biomass is a clean, renewable energy source with a large potential to contribute significantly to power generation, promising a more environmentally friendly production of electricity in future, with lower greenhouse gas emissions. A large variety of biomass feedstock exists, including agricultural and biomass residues and by-products, with wood, sludge, and waste among them. Biomass can be used directly to generate electricity if converted to more user-friendly sources of energy, e.g. by fermentation producing mainly methane (biogas) and by gasification leading mostly to hydrogen and carbon monoxide (syngas), allowing a more efficient use of the product gases compared to direct combustion, besides further advantages, with less amounts of ash and corrosive species. The resulting product gases can be burned in small to large scale gas turbines, stand alone, process integrated or in combined cycles. In a hybrid power plant, an increase of the electrical efficiency of small gas turbines to more than 50 % can be reached, by coupling a gasifier or biogas reactor with a fuel cell (FC) and a micro gas turbine. To widen the acceptable range in the variation of fuel composition and conditions and to ensure a reliable and more efficient operation, it is of outmost importance to expand our knowledge on biogenic gas mixtures with respect to modeling capabilities e.g. of major combustion properties, thus enabling predictive calculations. The present work is dealing with the use of representative biogenic gas mixtures for decentralized power production. The concept of coupling a gasifier or biogas reactor with a fuel cell and a micro gas turbine (hybrid power plant) is followed. The product gases are stemming from the fermentation of sludge and algae as well as from the gasification of their residues and wood, in addition. Their combustion behavior — lower heating value (LHV), Wobbe index, adiabatic flame temperature, laminar flame speed, and ignition delay time — is calculated for the relevant parameters — fuel-air ratio, pressure — and discussed with respect to the intended use.


Author(s):  
Peter J. Stuttaford

Gas turbines have the advantage of being able to operate on a wide range of fuels. Given the escalating cost of conventional fuel sources such as natural gas, there is increasing interest in, and implementation of, systems burning lower cost fuel gases. There are significant combustor performance effects when utilizing different fuels. Flame stability, emissions, durability, and combustion dynamics are critical combustion parameters which must be controlled when varying fuel constituents. Significant emphasis continues to be placed on the use of liquefied natural gas (LNG) as well as syngas derived from coal and petroleum coke. The elimination of carbon from gaseous coal based fuels also offers the possibility of burning hydrogen to reduce or eliminate carbon dioxide emissions. Existing stringent emissions permits must be met by power plants utilizing these different fuels. There is also a requirement for the flexible use of these fuels allowing power plants to switch real time between fuel sources using the same combustion hardware, without affecting commercial generating schedules. This highlights the requirement for fuel preparation and control skids, as well as robust combustion systems, for reliable plant operations. The objective of this work is to review fuel properties which affect combustion and consider the methods and tools used to characterize the subsequent combustion characteristics. The work focuses on gaseous fuel premixed combustion. A full scale high pressure combustion test stand was used to evaluate the effects of various gaseous fuels on given gas turbine combustor configurations. Data collected through the testing of natural gas containing heavy hydrocarbons, as might be expected from liquefied LNG or refinery offgas, and hydrogen based syngas fuel blends with natural gas to simulate various coal gas blends, is presented with conclusions drawn based upon the critical combustion parameters mentioned above. A methodology for fuel characterization and combustor qualification for the acceptable operation of gas turbine combustors on various gaseous fuels is discussed. The practical implementation of multi-fuel systems on commercially operating engines is also discussed, with emphasis on diluent free premixed systems.


Sign in / Sign up

Export Citation Format

Share Document