Towards Improved Boundary Layer Flashback Resistance of a 65 kW Gas Turbine With a Retrofittable Injector Concept

2018 ◽  
Author(s):  
Alireza Kalantari ◽  
Vincent McDonell ◽  
Scott Samuelsen ◽  
Shahram Farhangi ◽  
Don Ayers
Keyword(s):  
Boundary Layer ◽  
Gas Turbine ◽  
Elevated Pressure ◽  
Current Data ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Pollutant Emissions ◽  
Wall Region ◽  
Lean Premixed Combustion ◽  
High Hydrogen

Lean premixed combustion is extensively used in gas turbine industry to reduce pollutant emissions. However, combustion stability still remains as a primary challenge associated with high hydrogen content fuels. Flashback is a crucial concern for designing gas turbine combustors in terms of operability limits. The current experimental study addresses the boundary layer flashback of hydrogen-air premixed jet flames at gas turbine premixer conditions (i.e. elevated pressure and temperature). Flashback propensity of a commercially available injector, originally designed for natural gas, is studied at different operating conditions and corresponding measurements are presented. The pressure dependence of flashback propensity is consistent with previous studies. The previously developed flashback model is successfully applied to the current data, verifying its utilization for various test conditions/setups. In addition, the model is used to predict flashback propensity of the injector at the actual engine preheat temperature. The injector is then modified to increase boundary layer flashback resistance and the corresponding data are collected at the same operating conditions. To avoid the boundary layer flashback, the mixture is leaned out in the near-wall region, where the flame can potentially propagate upstream. The comparison of gathered data shows a clear improvement in flashback resistance. This improvement is further elaborated by numerically studying fuel/air mixing characteristics for the two injectors.

Boundary Layer Flashback Prediction for Turbulent Premixed Jet Flames: Comparison of Two Models

2019 ◽  
Author(s):  
Alireza Kalantari ◽  
Nicolas Auwaijan ◽  
Vincent McDonell
Keyword(s):  
Boundary Layer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Jet Flames ◽  
Turbulent Flame Speed ◽  
Turbulent Premixed

Abstract Lean-premixed combustion is commonly used in gas turbines to achieve low pollutant emissions, in particular nitrogen oxides. But use of hydrogen-rich fuels in premixed systems can potentially lead to flashback. Adding significant amounts of hydrogen to fuel mixtures substantially impacts the operating range of the combustor. Hence, to incorporate high hydrogen content fuels into gas turbine power generation systems, flashback limits need to be determined at relevant conditions. The present work compares two boundary layer flashback prediction methods developed for turbulent premixed jet flames. The Damköhler model was developed at University of California Irvine (UCI) and evaluated against flashback data from literature including actual engines. The second model was developed at Paul Scherrer Institut (PSI) using data obtained at gas turbine premixer conditions and is based on turbulent flame speed. Despite different overall approaches used, both models characterize flashback in terms of similar parameters. The Damköhler model takes into account the effect of thermal coupling and predicts flashback limits within a reasonable range. But the turbulent flame speed model provides a good agreement for a cooled burner, but shows less agreement for uncooled burner conditions. The impact of hydrogen addition (0 to 100% by volume) to methane or carbon monoxide is also investigated at different operating conditions and flashback prediction trends are consistent with the existing data at atmospheric pressure.

Experimental Study on the Influence of Pressure on the Flame Stabilization in Porous Inert Media (PIM)

2012 ◽  
Author(s):  
Cesar Bedoya ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis ◽  
Chockalingam Prathap ◽  
Hadi Ebrahimi
Keyword(s):  
Burning Velocity ◽  
Thermal Power ◽  
Elevated Pressure ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Pollutant Emissions ◽  
Lean Mixture ◽  
Wide Range ◽  
Porous Inert Media

Porous burners offer a possible solution to attain higher combustion stability under premixed conditions with ultra low pollutant emissions. To analyze the feasibility of PIM (porous inert media) in energy conversion processes, studies at elevated pressure have been carried out. In the present work, burning velocity of natural gas-air mixtures for lean mixture conditions at elevated pressure is obtained in a conical PIM by determining the flame location using thermocouples. Pressure, thermal power, equivalence ratio and initial temperature were varied in order to study their effect on the flame stability. The pressure was varied from 1.1 to 14.0 bar, and initial temperatures from 300 to 400K. The burning velocity data obtained from present measurements show good agreement with literature data at atmospheric pressure. The results show that the burning velocities measured in PIM decreased non-linearly with increase in pressure. Also, the decrease in the burning velocity in the PIM with pressure is more pronounced for lean mixture conditions. Present results indicate that the PIM produces stable flames for a wide range of operating conditions and generate low pollutant emissions, which show that it is a potential alternative for conventional burners.

scholarly journals Measurement of Air-Fuel Ratio Fluctuations Caused by Combustor Driven Oscillations

1998 ◽  
Author(s):  
Rajiv Mongia ◽  
Robert Dibble ◽  
Jeff Lovett
Keyword(s):  
Power Spectrum ◽  
Mole Fraction ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Premixed Combustion ◽  
Pollutant Emissions ◽  
Combustion Instabilities ◽  
Pressure Oscillations ◽  
Lean Premixed Combustion ◽  
Lean Premixed

Lean premixed combustion has emerged as a method of achieving low pollutant emissions from gas turbines. A common problem of lean premixed combustion is combustion instability. As conditions inside lean premixed combustors approach the lean flammability limit, large pressure variations are encountered. As a consequence, certain desirable gas turbine operating regimes are not approachable. In minimizing these regimes, combustor designers must rely upon trial and error because combustion instabilities are not well understood (and thus difficult to model). When they occur, pressure oscillations in the combustor can induce fluctuations in fuel mole fraction that can augment the pressure oscillations (undesirable) or dampen the pressure oscillations (desirable). In this paper, we demonstrate a method for measuring the fuel mole fraction oscillations which occur in the premixing section during combustion instabilities produced in the combustor that is downstream of the premixer. The fuel mole fraction in the premixer is measured with kHz resolution by the absorption of light from a 3.39 μm He-Ne laser. A sudden expansion combustor is constructed to demonstrate this fuel mole fraction measurement technique. Under several operating conditions, we measure significant fuel mole fraction fluctuations that are caused by pressure oscillations in the combustion chamber. Since the fuel mole fraction is sampled continuously, a power spectrum is easily generated. The fuel mole fraction power spectrum clearly indicates fuel mole fraction fluctuation frequencies are the same as the pressure fluctuation frequencies under some operating conditions.

Introduction of the Taurus™ 65 Industrial Gas Turbine for Power Generation

2008 ◽  
Author(s):  
George Rocha ◽  
Simon Reynolds ◽  
Theresa Brown
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Electrical Power ◽  
Field Evaluation ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Liquid Fuels ◽  
Operating Cycle ◽  
Product Experience ◽  
Exhaust Heat

Solar Turbines Incorporated has combined proven technology and product experience to develop the new Taurus 65 gas turbine for industrial power generation applications. The single-shaft engine is designed to produce 6.3 megawatts of electrical power with a 33% thermal efficiency at ISO operating conditions. Selection of the final engine operating cycle was based on extensive aerodynamic-cycle studies to achieve optimum output performance with increased exhaust heat capacity for combined heat and power installations. The basic engine configuration features an enhanced version of the robust Centaur®50 air compressor coupled to a newly designed three-stage turbine similar to the Taurus 70 turbine design. Advanced cooling technology and materials are used in the dry, lean-premix annular combustor, consistent with Solar’s proven SoLoNOx™ combustion technology, capable of reducing pollutant emissions while operating on standard natural gas or diesel liquid fuels. Like the Titan™ 130 and Taurus 70 products, a traditional design philosophy has been applied in development of the Taurus 65 gas turbine by utilizing existing components, common technology and product experience to minimize risk, lower cost and maximize durability. A comprehensive factory test plan and extended field evaluation program was used to validate the design integrity and demonstrate product durability prior to full market introduction.

Computational Study of NOx Formation at Conditions Relevant to Gas Turbine Operation, Part 2: NOx in High Hydrogen Content Fuel Combustion at Elevated Pressure

2016 ◽  
Vol 30 (9) ◽  
pp. 7691-7703 ◽  
Author(s):  
Sheikh F. Ahmed ◽  
Jeffrey Santner ◽  
Frederick L. Dryer ◽  
Bihter Padak ◽  
Tanvir I. Farouk
Keyword(s):  
Gas Turbine ◽  
Hydrogen Content ◽  
Computational Study ◽  
Elevated Pressure ◽  
Fuel Combustion ◽  
Nox Formation ◽  
High Hydrogen ◽  
High Hydrogen Content

Modeling of Turbulent Combustion and Radiative Heat Transfer in a Object-Oriented CFD Code for Gas Turbine Application

2008 ◽  
Author(s):  
Antonio Andreini ◽  
Matteo Cerutti ◽  
Bruno Facchini ◽  
Luca Mangani
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Radiative Heat Transfer ◽  
Turbulent Combustion ◽  
Radiative Heat ◽  
Object Oriented ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Combustion Models

One of the driving requirements in gas turbine design is the combustion analysis. The reduction of exhaust pollutant emissions is in fact the main design constraint of modern gas turbine engines, requiring a detailed investigation of flame stabilization criteria and temperature distribution within combustion chamber. At the same time, the prediction of thermal loads on liner walls continues to represent a critical issue especially with diffusion flame combustors which are still widely used in aeroengines. To meet such requirement, design techniques have to take advantage also of the most recent CFD tools that have to supply advanced combustion models according to the specific application demand. Even if LES approach represents a very accurate approach for the analysis of reactive flows, RANS computation still represents a fundamental tool in industrial gas turbine development, thanks to its optimal tradeoff between accuracy and computational costs. This paper describes the development and the validation of both combustion and radiation models in a object-oriented RANS CFD code: several turbulent combustion models were considered, all based on a generalized presumed PDF flamelet approach, valid for premixed and non premixed flames. Concerning radiative heat transfer calculations, two directional models based on the P1-Approximation and the Finite Volume Method were treated. Accuracy and reliability of developed models have been proved by performing several computations on well known literature test-cases. Selected cases investigate several turbulent flame types and regimes allowing to prove code affordability in a wide range of possible gas turbine operating conditions.

Effect of Fuel Composition on Emissions From a Low-Swirl Burner

2007 ◽  
Author(s):  
Daniel Sequera ◽  
Ajay K. Agrawal
Keyword(s):  
Gas Turbines ◽  
Bluff Body ◽  
Swirling Flow ◽  
Flame Temperature ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Recirculation Region ◽  
Fuel Composition ◽  
High Hydrogen ◽  
Flow Recirculation

Lean Premixed Combustion (LPM) is a widely used approach to effectively reduce pollutant emissions in advanced gas turbines. Most LPM combustion systems employ the swirling flow with a bluff body at the center to stabilize the flame. The flow recirculation region established downstream of the bluff-body brings combustion products in contact with fresh reactants to sustain the reactions. However, such systems are prone to combustion oscillations and flame flashback, especially if high hydrogen containing fuels are used. Low-Swirl Injector (LSI) is an innovative approach, whereby a freely propagating LPM flame is stabilized in a diverging flow field surrounded by a weakly-swirling flow. The LSI is devoid of the flow recirculation region in the reaction zone. In the present study, emissions measurements are reported for a LSI operated on mixtures of methane (CH4), hydrogen (H2), and carbon monoxide (CO) to simulate H2 synthetic gas produced by coal gasification. For a fixed adiabatic flame temperature and air flow rate, CH4 content of the fuel in atmospheric pressure experiments is varied from 100% to 50% (by volume) with the remainder of the fuel containing equal amounts of CO and H2. For each test case, the CO and nitric oxide (NOx) emissions are measured axially at the combustor center and radially at several axial locations. Results show that the LSI provides stable flame for a range of operating conditions and fuel mixtures. The emissions are relatively insensitive to the fuel composition within the operational range of the present experiments.

Numerical Simulation for the Preliminary Design of Fuel Flexible Stationary Gas Turbine Combustors Using Conventional and Alternative Fuels

2012 ◽  
Author(s):  
Washington Orlando Irrazabal Bohorquez ◽  
João Roberto Barbosa ◽  
Rob Johan Maria Bastiaans ◽  
Philip de Goey
Keyword(s):  
Numerical Simulation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
High Efficiency ◽  
Numerical Study ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Gas Turbine Combustor ◽  
Primary Zone

Currently, high efficiency and low emissions are most important requisites for the design of modern gas turbines due to the strong environmental restrictions around the world. In the past years, alternative fuels have been considered for application in industrial gas turbines. Therefore, combustor performance, pollutant emissions and the ability to burn several fuels became of much concern and high priority has been given to the combustor design. This paper describes a methodology focused on the design of stationary gas turbines combustion chambers with the ability to efficiently burn conventional and alternative fuels. A simplified methodology is used for the calculations of the equilibrium temperature and chemical species in the primary zone of a gas turbine combustor. Direct fuel injection and diffusion flames, together with numerical methods like Newton-Raphson, LU Factorization and Lagrange Polynomials, are used for the calculations. Diesel, ethanol and methanol fuels were chosen for the numerical study. A computer code sequentially calculates the main geometry of the combustor. From the numerical simulation it is concluded that the basic gas turbine combustor geometry, for some operating conditions and burning diesel, ethanol or methanol, are of similar sizes, because the development of aerodynamic characteristics predominate over the thermochemical properties. It is worth to note that the type of fuel has a marked effect on the stability and combustion advancement in the combustor. This can be seen when the primary zone is analyzed under a steady-state operating condition. At full power, the pressure is 1.8 MPa and the temperature 1,000 K at the combustor inlet. Then, the equivalence ratios in the primary zone are 1.3933 (diesel), 1.4352 (ethanol) and 1.3977 (methanol) and the equilibrium temperatures for the same operating conditions are 2,809 K (diesel), 2,754 K (ethanol) and 2,702 K (methanol). This means that the combustor can reach similar flame stability conditions, whereas the combustion efficiency will require richer fuel/air mixtures of ethanol or methanol are burnt instead of diesel. Another important result from the numerical study is that the concentration of the main pollutants (CO, CO2, NO, NO2) is reduced when ethanol or methanol are burnt, in place of diesel.

Investigation of Flame Stabilization in a High-Pressure Multi-Jet Combustor by Laser Measurement Techniques

2014 ◽  
Author(s):  
Oliver Lammel ◽  
Tim Rödiger ◽  
Michael Stöhr ◽  
Holger Ax ◽  
Peter Kutne ◽  
...  
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Recirculation Zone ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Single Shot ◽  
Optical Access

In this contribution, comprehensive optical and laser based measurements in a generic multi-jet combustor at gas turbine relevant conditions are presented. The flame position and shape, flow field, temperatures and species concentrations of turbulent premixed natural gas and hydrogen flames were investigated in a high-pressure test rig with optical access. The needs of modern highly efficient gas turbine combustion systems, i.e., fuel flexibility, load flexibility with increased part load capability, and high turbine inlet temperatures, have to be addressed by novel or improved burner concepts. One promising design is the enhanced FLOX® burner, which can achieve low pollutant emissions in a very wide range of operating conditions. In principle, this kind of gas turbine combustor consists of several nozzles without swirl, which discharge axial high momentum jets through orifices arranged on a circle. The geometry provides a pronounced inner recirculation zone in the combustion chamber. Flame stabilization takes place in a shear layer around the jet flow, where fresh gas is mixed with hot exhaust gas. Flashback resistance is obtained through the absence of low velocity zones, which favors this concept for multi-fuel applications, e.g. fuels with medium to high hydrogen content. The understanding of flame stabilization mechanisms of jet flames for different fuels is the key to identify and control the main parameters in the design process of combustors based on an enhanced FLOX® burner concept. Both experimental analysis and numerical simulations can contribute and complement each other in this task. They need a detailed and relevant data base, with well-known boundary conditions. For this purpose, a high-pressure burner assembly was designed with a generic 3-nozzle combustor in a rectangular combustion chamber with optical access. The nozzles are linearly arranged in z direction to allow for jet-jet interaction of the middle jet. This line is off-centered in y direction to develop a distinct recirculation zone. This arrangement approximates a sector of a full FLOX® gas turbine burner. The experiments were conducted at a pressure of 8 bar with preheated and premixed natural gas/air and hydrogen/air flows and jet velocities of 120 m/s. For the visualization of the flame, OH* chemiluminescence imaging was performed. 1D laser Raman scattering was applied and evaluated on an average and single shot basis in order to simultaneously and quantitatively determine the major species concentrations, the mixture fraction and the temperature. Flow velocities were measured using particle image velocimetry at different section planes through the combustion chamber.

Combustion Characteristics and NOX Emission of Hydrogen-Rich Fuel Gases at Gas Turbine Relevant Conditions

2012 ◽  
Author(s):  
Y.-C. Lin ◽  
S. Daniele ◽  
P. Jansohn ◽  
K. Boulouchos
Keyword(s):  
Gas Turbine ◽  
Turbulent Combustion ◽  
Turbulent Flame ◽  
Elevated Pressure ◽  
Chemical Kinetic ◽  
Nox Emission ◽  
Operating Pressure ◽  
High Hydrogen ◽  
Turbulent Flame Speed ◽  
Fuel Mixtures

In this paper, characteristics of turbulent combustion and NOx emission for high hydrogen-content fuel gases (H2 > 70 vol. %; “hydrogen-rich”) are addressed. An experimental investigation is performed in a perfectly-premixed axial-dump combustor under gas turbine relevant conditions. Fundamental features of turbulent combustion for these mixtures are evaluated based on OH-PLIF diagnostics. On the other hand, NOx emissions are measured with an exhaust gas sampling probe positioned downstream the combustor outlet. Compared to syngas mixtures (H2 + CO), the operational limits for hydrogen-rich fuel gases are found to occur at even leaner conditions concerning flashback phenomena. With respect to effects of operating pressure, a strongly reduced operational envelope is observed at elevated pressure. Only with decreasing the preheat temperature a viable approach to further extend the operational range is seen. Evaluation of the averaged turbulent flame shape shows that the profile of the flame front is generally approaching that of an ideal cone. Thus a simplified approach for estimating the turbulent flame speed via the location of the flame tip alone can be applied. The level of NOx emission for the hydrogen-rich fuel mixtures is generally above that of syngas mixtures, which exhibit already higher NOx emission values than natural gas. Distinct chemical kinetic features are found specifically at elevated pressure. While the pressure effects are weak for syngas, a non-monotonic behavior is observed for the hydrogen-rich fuels. Reaction path analysis is performed to complement and provide more insight to the findings from the measurements. From chemical kinetic calculations a distinct shift in NOx formation pathways (thermal NOx vs. NOx through N2O/NNH reaction channels) can be observed for the different fuel mixtures at different pressure levels.

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