Control of Lean Blowout in Partially Premixed Swirl-Stabilized Combustor Using a Fuel Rich Central Pilot Configuration

2019 ◽  
Author(s):  
Somnath De ◽  
Prasanna Mondal ◽  
Gourav Manohar Sardar ◽  
Rakin Bin Bokhtiar ◽  
Arijit Bhattacharya ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Premixed Flames ◽  
Premixed Combustion ◽  
Combustion Stability ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Lean Blowout ◽  
Partially Premixed Combustion ◽  
Partially Premixed

Abstract The main problem for using reliable and stable diffusion combustion in modern gas turbine engines is the production of NOx at a higher level which is not permissible for maintaining the healthy environment. Thus, combustion in lean premixed mode has become the most promising technology in many applications related to power generation gas turbine, industrial burner etc. Although the lean combustion minimizes NOx production, it suffers from an increased risk of lean blowout (LBO) when the requirement of thrust or load is low. It mainly occurs at the lean condition when the equilibrium between the flame speed and the unburnt air-fuel mixture velocity is broken. Current aircraft gas turbine engines operate fuel close to the combustion chamber which leads to the partially premixed combustion. Partially premixed combustion is also susceptible to lean blowout. Therefore, we have designed a swirl-stabilized dump combustor, where different lengths of fuel-air mixing are available. Our present work aims at improving the combustion stability by incorporating a secondary fuel injection through a pilot arrangement connected with the combustion chamber for premixed as well as partially premixed flames. Incorporation of the pilot system adds a small fraction of the total fuel into the combustion chamber directly. This investigation shows significant extension of the LBO limit towards leaner fuel-air mixture while the NOx emission in the combustion chamber is within the permissible limit. This result can be used for aircraft operators during the process of landing when fuel supply has to be decreased to reduce engine thrust or for power plants operating at low loads. The study of control is based on the colour variation of the flame which actually defines the changes in combustion characteristics. For early detection of LBO, the ratio between the intensity of red and blue colour obtained from flame images with a high speed camera is used. As LBO is approached, the ratio of red to blue intensity falls monotonically. When the ratio falls below a preset threshold, a small fraction of the total fuel is added to the central pilot line. This strategy allows the LBO limit to be shifted to a much lower equivalence ratio (maximum 20% and 11% for fully premixed and least premixed flames, respectively) without any significant increase in NOx production. The analysis includes a feedback control algorithm which is computed in MATLAB and the code is embedded in Labview for hardware implementation.

Fuel Flexible Rich Catalytic Lean Burn System for Low BTU Fuels

2013 ◽  
Author(s):  
Sandeep K. Alavandi ◽  
Shahrokh Etemad ◽  
Benjamin D. Baird
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Energy Content ◽  
Methane Content ◽  
Combustion Stability ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Waste Streams ◽  
Lean Burn ◽  
Process Waste

Limited fuel resources, increasing energy demand, and stringent emission regulations are drivers to evaluate process off-gases or process waste streams as fuels for power generation. Often these process waste streams have low energy content and their operability in gas turbines leads to issues such as unstable or incomplete combustion and changes in acoustic response. Due to above reasons, these fuels cannot be used directly without modifications or efficiency penalties in gas turbine engines. To enable the use of the wide variety of ultra-low and low Btu fuels in gas turbine engines, a rich catalytic lean burn (RCL®) combustion system was developed and tested in a subscale high pressure (10 atm.) rig. Previous work has shown promise with fuels such as blast furnace gas (BFG) with Lower Heating Value (LHV) of 3.1 MJ/Nm3 (85 Btu/scf). The current testing extends the limits of RCL® operability to other weak fuels by further modifying and improving the injector to achieve enhanced flame stability. Fuels containing low methane content such as weak natural gas with an LHV of 6.5 MJ/Nm3 (180 Btu/scf) to fuels containing higher methane content such as landfill gas with an LHV of 21.1 MJ/Nm3 (580 Btu/scf) were tested. These fuels demonstrated improved combustion stability with an extended turndown (defined as the difference between catalytic and non-catalytic lean blow out) of 140°C–170°C (280°F–340°F) with CO and NOx emissions lower than 5 ppm corrected to 15% O2.

Multispectral pyrometer for high temperature measurements inside combustion chamber of gas turbine engines

Measurement ◽  
2019 ◽  
Vol 139 ◽  
pp. 355-360 ◽  
Author(s):  
M.V. Mekhrengin ◽  
I.K. Meshkovskii ◽  
V.A. Tashkinov ◽  
V.I. Guryev ◽  
A.V. Sukhinets ◽  
...  
Keyword(s):  
High Temperature ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Temperature Measurements ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
High Temperature Measurements

Investigation of Tangential Trapped Vortex Combustor

2009 ◽  
Author(s):  
Chi Zhang ◽  
Yuzhen Lin ◽  
Quanhong Xu ◽  
Gaoen Liu
Keyword(s):  
Gas Turbine ◽  
Swirling Flow ◽  
Tangential Direction ◽  
Combustion Efficiency ◽  
Combustion Stability ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Stability Range ◽  
Combustion Technology ◽  
Trapped Vortex

An innovative concept of Tangential Trapped Vortex Combustor (TTVC) applying a swirling flow to eliminate the guide vanes of the compressor and turbine in the future gas turbine engines is presented via theoretical analysis and experimental investigation. In TTVC, the airflow is mostly whirlblast, and the processes of evaporation, mixing, and chemical reaction for the liquid spray combustion take place along the tangential direction. It is shown that the TTVC operation has the potential of improving combustion efficiency, widening combustion stability range, and reducing emissions, mainly due to the effects of trapped vortex, high centrifugal force, and periodical mixing. Experimental results of the ignition and LBO limits in a small 4-cup annular TTVC operating at atmospheric pressure demonstrated that this innovative combustion technology has a good LBO limit performance to meet the requirements of advanced gas turbine engines.

Large-Eddy Simulation With a New Flamelet Model for Partially Premixed Combustion in a Gas-Turbine Combustor

2017 ◽  
Author(s):  
Keisuke Tanaka ◽  
Tomonari Sato ◽  
Nobuyuki Oshima ◽  
Jiun Kim ◽  
Yusuke Takahashi ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Diffusion Flame ◽  
Premixed Combustion ◽  
Combustion Model ◽  
Gas Turbine Combustor ◽  
Flamelet Model ◽  
Eddy Simulation ◽  
Partially Premixed Combustion ◽  
Large Eddy ◽  
Partially Premixed

Turbulent combustion flows in the partially premixed combustion field of a dry low-emission gas-turbine combustor were investigated numerically by large-eddy simulation with a 2-scalar flamelet model. Partially premixed combustion was modelled with 2-scalar coupling based on the conservative function of the mixture fraction and the level set function of the premixed flame surface; the governing equations were then used to calculate the gas temperature in the combustion field with flamelet data. A new combustion model was introduced by defining a nondimensional equilibrium temperature to permit the calculation of adiabatic flame temperatures in the combustion field. Furthermore, a conventional G-equation was modified to include spatial gradient terms for the adiabatic flame temperature to facilitate smooth propagation of a burnt-state region in a predominantly diffusion flame. The effect of flame curvature was adjusted by means of an arbitrary parameter in the equation. The simulation results were compared with those from an experiment and a conventional model. Qualitative comparisons of the instantaneous flame properties showed a dramatic improvement in the new combustion model. Moreover, the experimental outlet temperature agreed well with that predicted by the new model. The model can therefore reproduce the propagation of a predominantly diffusion flame in partially premixed combustion.

scholarly journals Design and development of combustion chambers for gas turbine engines based on calculations of various levels of complexity

2021 ◽  
Vol 20 (3) ◽  
pp. 7-23
Author(s):  
Y. B. Aleksandrov ◽  
T. D. Nguyen ◽  
B. G. Mingazov
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Gas Flow ◽  
Combustion Process ◽  
Three Dimensional ◽  
Numerical Calculations ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Combustion Chambers ◽  
Flame Tube

The article proposes a method for designing combustion chambers for gas turbine engines based on a combination of the use of calculations in a one-dimensional and three-dimensional formulation of the problem. This technique allows you to quickly design at the initial stage of creating and development of the existing combustion chambers using simplified calculation algorithms. At the final stage, detailed calculations are carried out using three-dimensional numerical calculations. The method includes hydraulic calculations, on the basis of which the distribution of the air flow passing through the main elements of the combustion chamber is determined. Then, the mixing of the gas flow downstream of the flame tube head and the air passing through the holes in the flame tube is determined. The mixing quality determines the distribution of local mixture compositions along the length of the flame tube. The calculation of the combustion process is carried out with the determination of the combustion efficiency, temperature, concentrations of harmful substances and other parameters. The proposed method is tested drawing on the example of a combustion chamber of the cannular type. The results of numerical calculations, experimental data and values obtained using the proposed method for various operating modes of the engine are compared.

scholarly journals Performance Assessment of the Thermodynamic Cycle in a Multi-Mode Gas Turbine Engine

2021 ◽  
Author(s):  
Viktors Gutakovskis ◽  
Vladimirs Gudakovskis
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Gas Turbine Engine ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Working Process ◽  
Adaptive Approach ◽  
Turbine Engine ◽  
Operation Modes ◽  
Multi Mode

This chapter discusses the direction of development of promising multimode aviation gas turbine engines (GTE). It is shown that the development of GTE is on the way to increase the parameters engine workflow: gas temperatures in front of the turbine (T*G) and the degree of pressure increase in the compressor (P*C). It is predicted that the next generation engines will operate with high parameters of the working process, T*G = 2000–2200 K, π*C = 60–80. At this temperature of gases in front of the turbine, the working mixture in the combustion chamber (CC) is stoichiometric, which sharply narrows the range of stable operation of the CC and its efficiency drops sharply in off-design gas turbine engine operation modes. To expand the range of effective and stable work, it is proposed to use an advanced aviation GTE: Adaptive Type Combustion Chamber (ATCC). A scheme of the ATCC and the principles of its regulation in the system of a multi-mode gas turbine engine are presented. The concept of an adaptive approach is given in this article. There are two main directions for improving the characteristics of a promising aviation gas turbine engine. One is a complication of the concepts of aircraft engines and the other one is an increase in the parameters of the working process, the temperature of the gases in front of the turbine (T*G) and the degree of increasing pressure behind the compressor (π*C). It is shown how the principles of adaptation are used in these areas. The application of the adaptation principle in resolving the contradiction of the possibility of obtaining optimal characteristics of a high-temperature combustion chamber (CC) of a gas turbine engine under design (optimal) operating conditions and the impossibility of their implementation when these conditions change in the range of acceptable (non-design) gas turbine operation modes is considered in detail. The use of an adaptive approach in the development of promising gas turbine engines will significantly improve their characteristics and take into account unknown challenges.

Relative Effects of Velocity- and Mixture-Coupling in a Thermoacoustically Unstable, Partially-Premixed Flame

2021 ◽  
Author(s):  
Ashwini Karmarker ◽  
Jacqueline O’Connor ◽  
Isaac Boxx
Keyword(s):  
Gas Turbine ◽  
Equivalence Ratio ◽  
Premixed Flame ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Real Gas ◽  
Planar Laser ◽  
Partially Premixed ◽  
Partially Premixed Flame ◽  
The Impact

Abstract Combustion instability, which is the result of a coupling between combustor acoustic modes and unsteady flame heat release rate, is a severely limiting factor in the operability and performance of modern gas turbine engines. This coupling can occur through different coupling pathways, such as flow field fluctuations or equivalence ratio fluctuations. In realistic combustor systems, there are complex hydrodynamic and thermo-chemical processes involved, which can lead to multiple coupling pathways. In order to understand and predict the mechanisms that govern the onset of combustion instability in real gas turbine engines, we consider the influences that each of these coupling pathways can have on the stability and dynamics of a partially-premixed, swirl-stabilized flame. In this study, we use a model gas turbine combustor with two concentric swirling nozzles of air, separated by a ring of fuel injectors, operating at an elevated pressure of 5 bar. The flow split between the two streams is systematically varied to observe the impact on the flow and flame dynamics. High-speed stereoscopic particle image velocimetry, OH planar laser-induced fluorescence, and acetone planar laser-induced fluorescence are used to obtain information about the velocity field, flame, and fuel-flow behavior, respectively. Depending on the flow conditions, a thermoacoustic oscillation mode or a hydrodynamic mode, identified as the precessing vortex core, is present. The focus of this study is to characterize the mixture coupling processes in this partially-premixed flame as well as the impact that the velocity oscillations have on mixture coupling. Our results show that, for this combustor system, changing the flow split between the two concentric nozzles can alter the dominant harmonic oscillation modes in the system, which can significantly impact the dispersion of fuel into air, thereby modulating the local equivalence ratio of the flame. This insight can be used to design instability control mechanisms in real gas turbine engines.

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