Gas Turbine Engine Combustion Research Articles

Effects of air to fuel ratio on parameters of combustor used for gas turbine engines: Applications of turbojet, turbofan, turboprop and turboshaft

Combustors of gas turbine engines have generally the highest irreversibility due to the combustion process. Therefore, to observe influence of air to fuel ratio (AFR) on combustor performance is of high importance. In this study, thermodynamic laws are employed to separately determine adiabatic flame temperature (AFT), entropy production, exergy destruction and exergy efficiency of combustor for turbojet (TJ), turbofan (TF), turboprop (TP) and turboshaft (TS) where variables are AFR, combustor inlet temperature (CIT) and combustor pressure ratio (CPR). In this regard, the higher the AFR, the lower the adiabatic flame temperature, however the higher the entropy production for related combustor. Similarly, increasing AFR leads to raise exergy destruction, thereby lowering exergy efficiency. On the other hand, as CIT increases, exergy efficiency of the combustor improves whereas slight effects of CPR on the combustor metrics are observed. Namely, due to variation of AFR, exergy destruction of combustor changes between 0.512 MW and 0.825 MW for TJ, between 1.807 MW and 2.735 MW for TS, between 28.38 MW and 40.49 MW for TF and between 3.102 MW and 4.564 MW for TP. Moreover, exergy efficiency of combustor changes between 59% and 73% for TJ, between 70% and 77% for TS, between 78% and 81% for TF and between 75% and 79% for TP engine through the determined AFR and CIT ranges. These findings indicate that combustor of each gas turbine engine demonstrates different behavior according to the mentioned variables and exergy efficiency of combustor depends on finding the optimum points of combustor variables.

Working process model development of the gas turbine engine combustor fueling on methanol

The use of methanol as a fuel for aircraft and stationary gas turbine engines (GTE) is a priority direction in engine building. It is well known that when modeling the GTE performances using first-level mathematical models, there is an error in calculating specific fuel consumption, which is caused by the simplified description of the GTE combustor working process. The object of the study is the working process in the GTE combustor fueling on methanol. The peculiarity of the developed mathematical model of the working process of the GTE combustor is the use of enthalpy dependencies on temperature, pressure, and mixture composition. Enthalpy dependencies in this form implicitly account for the effect of thermal dissociation and allow for the correct formulation of the equivalent combustion reaction path. For two components (H2O and CO2), accounting for pressure leads to the fact that at standard temperature and partial pressures exceeding the saturation pressure, these components exist in a liquid state. This situation, with a constant enthalpy increment in the equivalent process of heating the combustion products from the standard temperature to the temperature at the end of adiabatic heat supply, decreases this temperature. Clarification of the temperature at the combustor outlet leads to changes in all calculated combustor performances, including the combustor fuel air ratio. The calculation results of the fuel air ratio are compared with known experimental data of the General Electric CF6-80A engine combustor (USA). The average calculation error of the fuel air ratio does not exceed 4 %. The developed model can be implemented in existing and developing mathematical models of gas turbine engines for temperatures at the end of the combustion process below 2,600 K

Numerical Investigation on the Characteristics of a Novel Multi-Swirl Lean Direct Injection Burner With Large Eddy Simulation-Flamelet Generated Manifold Method

Abstract The lean direct injection (LDI) concept can eventually replace the current combustion systems in aviation engines because of its low NOx emissions without compromising other parameters. A novel multiswirl LDI burner with distributed fuel injection surrounded by air- flow through multiple hexagonal swirlers of vane angle 45 deg was developed. In this study, large eddy simulation (LES), using the dynamic Smagorinsky-Lilly subgrid model together with the flamelet generated manifold (FGM) combustion model, has been used to analyze the correlation between aerodynamics, mixing, and combustion characteristics of the burner. The agreement between the experimental data and the LES simulation was good, and it can accurately predict the trend of variables like velocity, temperature, and mixture fraction at different Reynolds number and equivalence ratios. The LES-FGM results demonstrated the rapid formation of a homogeneous fuel-air mixture over a short distance, which results in excellent flame stability, and it has ultralow NOx emission due to low flame temperature and negligible internal recirculation. It was discovered that going from a global equivalence ratio of 0.7 to 0.9 increases the flame liftoff distance because the high fuel volume flowrate causes the mixing of swirling air and fuel jet to become more and more delayed. The research in this paper provides an insight into the ability of the LES-FGM method to capture the complex flow field structures and the flame behavior globally of a novel low NOx multiswirl burner that might be a competitor in the combustors of commercial gas turbine engines.

Experimental study results of the front-end device with two-tier air burner as part of the gas turbine engine combustion chamber

In recent years, the gas turbine power plant has been increasingly used in various industries in Kazakhstan. The reasons for this are: thermal efficiency, simplicity of the thermal scheme and design, small mass per power unit, high maneuverability, low toxicity, and relatively simple automation of operation. This paper presents the experimental study results of a two-tier air burner as the part of the gas turbine engine combustion chamber at burning liquid fuel. ? new design of a microflame device was developed. Two-tier burner makes possible the combustion process in a number of discrete zones, i.e. microflame combustion. During the experiment, the installation angles of the blades of the external and internal registers, as well as the ratio of the coefficients of excess air in the tiers, were changed. The experimental studies of a two-tier burner confirmed the possibility to increase fuel combustion efficiency, a low degree of temperature field unevenness and to decrease NOx emission.

Kinetic model and kerosene surrogate for calculating gas turbine engine emission of carcinogenic hydrocarbons

To calculate the emission of carcinogenic polycyclic aromatic hydrocarbons by the combustion chambers of aircraft gas turbine engines, the A17 kinetic model has been developed, characterized by new blocks of elementary chemical reactions of hydrocarbon compounds oxidation and synthesis of polycyclic aromatic hydrocarbons. The results of model validation showed satisfactory agreement with the experimental data and the possibility of applying the model to describe combustion processes in gas turbine engine combustion chambers. A review and numerical study was carried out for 14 surrogates (model fuels) of aviation kerosene, the combustion of which can be described using the A17 model. Simulation of stabilized flame of a previously prepared mixture showed the effectiveness of Drexel, Liu, su4, UM1 surrogates, the predictions for which agree satisfactorily with the experimental data and provide the expected levels of concentration of polycyclic aromatic hydrocarbons. The calculations show the dependence of the concentration of the most carcinogenic polycyclic aromatic hydrocarbon benzo(a)pyrene, and the ratio of the main combustion products CO2/H2O on the molar mass of the fuel. For the experimentally determined value of the molar mass of kerosene TS-1, the smallest deviation (up to 0.25%) is demonstrated by the su4 and UM1 surrogates. Due to the best predictive capability for the ignition delay time, normal flame propagation speed, pyrolysis and combustion products, the su4 and UM1 surrogates can be chosen to calculate the emission of carcinogenic polycyclic aromatic hydrocarbons from aircraft gas turbine engine combustion chambers.

Оцінка впливу експлуатаційних параметрів на роботу авіаційного газотурбінного двигуна

This paper considers the possibilities of improving the reliability and efficiency of the aircraft engine, which are one of the main indicators of quality and require high-quality fuel. Modern gas turbine engines (GTE) are much more powerful and economical compared with those produced 50 years ago. Nevertheless, manufacturers are constantly working to improve gas turbine engines with the main emphasis on their fuel efficiency. Mechanical impurities present in the fuel can clog the fuel filters, thereby cutting off the fuel supply. The presence of resins in the fuel leads to the formation of various deposits on engine parts, and the content of sulfur, acids and alkalis increases the corrosiveness of the fuel. The completeness of combustion and the tendency of carbon formation are the main performance characteristics of hydrocarbon fuels, which are of great practical importance in improving the efficiency and service life of the engine. Currently, there are many options for improving technical and economic indicators. The proposed ways to prepare a better fuel mixture before supplying it to the engine. The preparation of aviation fuel is carried out because of the electrophysical effects on the fuel. The electrophysical effect on the fuel is determined by a magnetic installation with a sign-changing magnetic field. Studies were conducted to determine the effect of electrophysical impact on the completeness of combustion of aviation fuel and carbon formation in the combustion chamber of a gas turbine engine. The method allows to give a comparative assessment of the completeness of combustion and carbon formation of fuels for engines with a small amount of fuel consumed for testing. It has been established that under electrophysical action on aviation fuel, the fuel combustion efficiency increases by 10...12 %, carbon formation in the gas turbine engine combustion chamber decreases by 20...25 %. The positive effect on the combustion process in the previous phases decreases the afterburning phase, therefore, a decrease in the temperature of the exhaust gases, a decrease in the concentration of nitrogen oxide by 12...16 %, carbon monoxide by 0.64...0.7 % and hydrocarbon by 25...35 %. After the electrophysical impact and the fuel running time, the content of resinous compounds increased four times, the content of oxygen compounds decreased by ~23 %, and the content of sulfur compounds decreased by ~25 %.

Effect of Nozzle Port Shape of Fuel Injector of Micro Gas Turbine Engine Combustor on Mixture Gas Formation for Combustion

The objective of this study was to optimize the design of the injection nozzle hole of the fuel injector of a model MGT engine. To achieve a higher combustion efficiency of the mixed gas in the combustion chamber, first, well-mixed homogeneous gas should be formed to accelerate the flame propagation in the chamber to reach a higher combustion temperature and pressure. In this study, four different shapes of the nozzle hole of the fuel injector were designed, and the mixed gas formation characteristics in the chamber were numerically analyzed. Three parameters—the penetration, diffusivity, and amount of fuel injected—were analyzed and compared to find the optimum shape of the nozzle hole with the highest combustion efficiency in the chamber. CFD analysis was conducted using a general-purpose CFD (Computational Fluid Dynamics) code-named PHOENICS (ver. 2020). Based on the analysis results, it was found that the penetration length (lp), diffusion angle (θ), and volume flow rate (Q˙f) of the injected fuel of Model 3 had the best injection characteristics for the well-mixed gas formation condition in the combustion chamber. Especially, the volume flow rate of the injected fuel of Model 3, which directly affects the output power of the engine, increased by more than 5%. This result is useful and informative for making a sample combustor for a combustion performance test of the model gas turbine engine.

Adaptive fuzzy gas turbine engine combustion chamber temperature meter

Adaptive fuzzy gas turbine engine combustion chamber temperature meter

Numerical simulations and analysis of the turbulent flow field in a practical gas turbine engine combustor

The turbulent flow field in a practical gas turbine combustor is very complex because of the interactions between various flows resulting from components like multiple types of swirlers, dilution holes, and liner effusion cooling holes. Numerical simulations of flows in such complex combustor configurations are challenging. The challenges result from (a) the complexities of the interfaces between multiple three-dimensional shear layers, (b) the need for proper treatment of a large number of tiny effusion holes with multiple angles, and (c) the requirements for fast turnaround times in support of engineering design optimization. Both the Reynolds averaged Navier–Stokes simulation (RANS) and the large eddy simulation (LES) for the practical combustor geometry are considered. An autonomous meshing using the cut-cell Cartesian method and adaptive mesh refinement (AMR) is demonstrated for the first time to simulate the flow in a practical combustor geometry. The numerical studies include a set of computations of flows under a prescribed pressure drop across the passage of interest and another set of computations with all passages open with a specified total flow rate at the plenum inlet and the pressure at the exit. For both sets, the results of the RANS and the LES flow computations agree with each other and with the corresponding measurements. The results from the high-resolution LES simulations are utilized to gain fundamental insights into the complex turbulent flow field by examining the profiles of the velocity, the vorticity, and the turbulent kinetic energy. The dynamics of the turbulent structures are well captured in the results of the LES simulations.

Computation of conventional and alternative jet fuel sensitivity to lean blowout

Large Eddy Simulations (LES) are performed to compute the sensitivity of a conventional (A-2) and an alternate bio-jet (C-1) fuel to Lean Blowout (LBO). A realistic aviation gas turbine engine combustor configuration is considered. Reliable experimental LBO data and OH∗ chemiluminescence data for the conventional and alternate jet fuel in the combustor configuration have recently become available. The present work utilizes a highly automated, on-the-fly meshing strategy, along with adaptive mesh refinement, to demonstrate the feasibility of capturing the realistic combustion processes. A Lagrangian framework, with initial conditions specified using measurements of spray statistics, is used to model the fuel spray. Newly developed compact reaction mechanisms based on fuel surrogates are validated for the A-2 and the C-1 fuels. The compact reaction mechanisms are implemented using a detailed finite rate chemistry solver. Spray statistics computed by the present LES simulations compare well with available measurements at stable flame conditions near the lean blowout limit. The computed shape of the stable flame as represented by line integrated OH concentrations compares well with the experimental OH∗ chemiluminescence data. Lean blowout is reached by gradually decreasing the fuel flow rate in the computations, similar to that in the experiments. The results of the LES simulations effectively capture the fuel composition effects and estimate the sensitivity of the LBO limits to the fuel type. The computed trends in LBO limits agree within engineering accuracy with the experimental results for conventional and alternative aviation fuels. The methodology for predicting the fuel composition effects on the lean blowout limits in a fully resolved realistic, complex combustor is established for the first time.

A data-driven approach using machine learning for early detection of the lean blowout

A data-driven approach using machine learning is presented for the identification of the critical flame location for the early detection of an incipient lean blowout (LBO) in a realistic gas turbine engine combustor under engine-relevant conditions. This method is demonstrated by utilizing the temperature (T) and the hydroxyl radical mass fraction (YOH) data from high fidelity large eddy simulations (LES) of Jet-A combustion. The fuel flow rate is progressively reduced in numerical simulations with a fixed airflow rate to mimic experimental studies of LBO in the gas turbine combustor. These simulations are the first of their kind for a fully resolved realistic combustor geometry with adaptive mesh refinement and have accurately captured the dynamics of the LBO process and global lean blowout equivalence ratio. Time-series of T and YOH are extracted in the primary zone of the combustor, from stable flame condition to LBO condition, to train the machine learning model. A Support Vector Machine (SVM) model with radial basis function is successfully developed to identify the critical flame location for early detection of incipient LBO condition in a practical combustor for the first time. The performance of the SVM model is quantified using the F-score, and the critical flame location corresponds to the maximum value of the F-score. The critical flame location is found to be in the flame root region and is effective in the early detection of incipient LBO. The conventional statistical measures are compared with the results of the trained machine learning model to assess the feasibility of the latter for online flame health monitoring. The machine learning model successfully prognosticated the LBO approximately 20 ms before the event, and this study has shown significant promise for the use of the SVM model in engine prognostics and health management.

Evaluation of Chemical Kinetic Mechanisms for Methane Combustion: A Review from a CFD Perspective

Methane is an important fuel for gas turbine and gas engine combustion, and the most common fuel in fundamental combustion studies. As Computational Fluid Dynamics (CFD) modeling of combustion becomes increasingly important, so do chemical kinetic mechanisms for methane combustion. Kinetic mechanisms of different complexity exist, and the aim of this study is to review commonly used detailed, reduced, and global mechanisms of importance for CFD of methane combustion. In this review, procedures of relevance to model development are outlined. Simulations of zero and one-dimensional configurations have been performed over a wide range of conditions, including addition of H2, CO2 and H2O, and the results are used in a final recommendation about the use of the different mechanisms. The aim of this review is to put focus on the importance of an informed choice of kinetic mechanism to obtain accurate results at a reasonable computational cost. It is shown that for flame simulations, a reduced mechanism with only 42 irreversible reactions gives excellent agreement with experimental data, using only 5% of the computational time as compared to the widely used GRI-Mech 3.0. The reduced mechanisms are highly suitable for flame simulations, while for ignition they tend to react too slow, giving longer than expected ignition delay time. For combustible mixtures with addition of hydrogen, carbon dioxide, or water, the detailed as well as reduced mechanisms generally show as good performance as for the corresponding simulations of pure methane/air mixtures.

3D convolutional selective autoencoder for instability detection in combustion systems

While analytical solutions of critical (phase) transitions in dynamical systems are abundant for simple nonlinear systems, such analysis remains intractable for real-life dynamical systems. A key example is thermoacoustic instability in combustion, where prediction or early detection of the onset of instability is a hard technical challenge, which needs to be addressed to build safer and more energy-efficient gas turbine engines powering aerospace and energy industries. The instabilities arising in combustion chambers of engines are mathematically too complex to model. To address this issue in a data-driven manner instead, we propose a novel deep learning architecture called 3D convolutional selective autoencoder (3D-CSAE) to detect the evolution of self-excited oscillations using spatiotemporal data, i.e., hi-speed videos taken from a swirl-stabilized combustor (laboratory surrogate of gas turbine engine combustor). 3D-CSAE consists of filters to learn, in a hierarchical fashion, the complex visual and dynamic features related to combustion instability from the training videos (i.e., two spatial dimensions for the image frames and the third dimension for time). We train the 3D-CSAE on frames of videos obtained from a limited set of operating conditions. We select the 3D-CSAE hyper-parameters that are effective for characterizing hierarchical and multiscale instability structure evolution by utilizing the dynamic information available in the video. The proposed model clearly shows performance improvement in detecting the precursors and the onset of instability. The machine learning-driven results are verified with physics-based off-line measures. Advanced active control mechanisms can directly leverage the proposed online detection capability of 3D-CSAE to mitigate the adverse effects of combustion instabilities on the engine operating under various stringent requirements and conditions.

Numerical and Experimental Analysis of Combustion Characteristics of Gas Turbine Engines

Advanced computational fluid dynamics (CFD) methods were used to carry out the numerical analysis. It was created a three-dimensional CFD model to represent the intricate flow and combustion processes inside the gas turbine engine. Fuel injection, combustion kinetics, and the effects of turbulence were all taken into account by the model. In order to analyse several combustion factors, such as temperature distribution, species concentrations, and flame propagation, numerical simulations were run.Experimentation was done in order to verify the numerical results and understand the combustion properties better. To simulate the operational circumstances of a gas turbine engine, a test setup was created. Measurements of combustion parameters, including pressure, temperature, and emissions, were made and compared to the numerical forecasts. The computational model might then be verified and improved as a result.The findings of this study offer insightful information about how gas turbine engines behave during combustion. The temperature distribution, species concentrations, and flame propagation within the engine were all correctly predicted by the numerical models. The experimental observations showed good agreement with the expected values, confirming the accuracy of the numerical model. This thorough examination aids in the comprehension of gas turbine engine combustion processes and can be used as a foundation for future design enhancements and performance enhancements.

A Two-Parameter Corresponding States Method for Calculating the Steady-State Evaporation Rate of C2\u2013C9 n-Alkane Droplets in Air for Elevated Pressures and Temperatures

Advanced gas turbine and internal combustion engine combustion chambers operate at highly elevated pressures and temperatures. Therefore, spray vaporization analysis cannot be limited to the atmospheric environment since evaporation strongly depends on ambient conditions. Presently, the effect of air pressure and temperature on droplet evaporation rate was investigated by using both a transient and a steady-state approach. A corresponding states model was derived for the steady-state evaporation rate for n-alkanes in the range of C2–C9 with an excellent fit quality and < 1% model uncertainty, considering the thermophysical data uncertainties. The model was tested for C1, C10, and C12 n-alkanes as well with low success. The ambient conditions were evaluated in terms of reduced pressures and temperatures, covering the range of 0.02–0.5 and 1.2–1.5, respectively. However, the applicability of the model was limited to reduced temperature of 1.3–1.5, as higher discrepancy was observed between the trends of the different n-alkanes at lower temperatures. Since the heat-up phase of practical sprays in combustion chambers is often short, the present model might significantly reduce the computational effort required for liquid evaporation calculations.

Burner geometry impact on gas turbine engine combustion chamber characteristics

Burner geometry impact on gas turbine engine combustion chamber characteristics

Swirler blades installation angle impact on flow mixing efficiency behind the flame tube head of gas turbine engine combustion chamber

Swirler blades installation angle impact on flow mixing efficiency behind the flame tube head of gas turbine engine combustion chamber

A method of air-blast atomization of foamed liquid fuels for advanced combustors of gas-turbine engines

The design of the combined nozzle module with bubbling and pneumatic spraying for the low-emission combustion GTE chamber has been carried out. Based on pervious work and literature analyzie a prototype of new combined nozzle module with five places of bubbling air supplying were pre-designed. To pre-select the position of the emulsification holes and to determine the possibility of combining the emulsion and pneumatic spraying principles in one design a series of experiments was carried out. The first results obtained using even not optimized device, showed that in modes close to the ground start and idle, the quality of the fuel spraying was improved by 30 % using the method of low-flow fuel bubbling.

Flow conditions analysis of Gas Turbine Combustor

Gas turbines are equipped for working effectively on a wide assortment of energizes. Combustor is directed to a great extent by the requirement for its length and frontal territory to stay inside the cut-off points set by other motor segments by the need for a diffuser to limit pressure problems, another issue of expanding significance is that acoustic reverberation. The decrease of combustor size and weight is another significant necessity for air motors. The aim of the present work is to analyse the combustion chamber geometry using FINE/OPEN of NUMECA software and to predict the hot and cold total pressure loss, (circumferential and radial) pattern factors and combustion efficiency. This paper mainly work towards understanding the effect of cold and hot flow in a practical combustor systems using CFD and to estimate the various parameters like pressure loss, pattern factor (circumferential and radial), velocity distribution through diffuser, dome, swirler, three zones and combustor holes. The flow analysis is further extended to investigate the effects of temperature distribution of the flow that reaches the turbine inlet. The combustor model is created using CATIA and parts are then cleaned individual using CADfix suitable for meshing. The performance of the turbulence model is analysed and compared. Present work deals with the implementation of Computational Fluid Dynamics (CFD) for three-dimensional analysis of flow in an annular combustor of an aero gas turbine engine. FINE/OPEN of NUMECA commercial code will be used to analyse the Combustion chamber geometry. The analysis is carried out both in FLUENT and NUMECA and the results are compared.

Lowest emission sustainable aviation biofuels as the potential replacement for the Jet-A fuels

Purpose The purpose of this study is to predict the performance and emission characteristics of micro gas turbine engines powered by alternate fuels. The micro gas turbine engine performance, combustion and emission characteristics are analyzed for the jet fuel with different additives. Design/methodology/approach The experimental investigation was carried out with Jet A-1 fuel on the gas turbine engines at different load conditions. The primary blends of the Jet A-1 fuels are from canola and solid waste pyrolysis oil. Then the ultrasonication of highly concentrated multiwall carbon nanotubes is carried with the primary blends of canola (Jet-A fuel 70%, canola 20% and 10% ethanol) and P20E (Jet-A 70% fuel, 20% PO and 10% ethanol). Findings The consumption of the fuel is appreciable with the blends at a very high static thrust. The 39% reduction in thrust specific fuel consumption associated with a 32% enhance in static thrust with P20E blend among different fuel blends. Moreover, due to the increase in ethanol concentration in the blends PO20E and C20E lead to a 22% rise in thermal efficiency and a 9% increase in higher oxygen content is observed. Practical implications The gas turbine engine emits very low emission of gases such as CO, CO2 and NOx by using the fuel blends, which typically reduces the fossil fuel usage limits with reduced pollutants. Originality/value The emission of the gas turbine engines is further optimized with the addition of hydrogen in Jet-A fuel. That is leading to high specific fuel exergy and owing to the lower carbon content in the hydrogen fuel when compared with that of the fossil fuels used in gas turbine engines. Therefore, the usage of hydrogen with nanofluids was so promising based on the results obtained for replacing fossil fuels.