Liquid-fueled Gas Turbine Combustor Research Articles

Large Eddy Simulations of complex multicomponent swirling spray flames in a realistic gas turbine combustor

Large Eddy Simulations of the realistic liquid fueled gas turbine combustor LOTAR operated at ONERA are performed for two fuels; a conventional JetA-1 and an alternative alcohol to jet fuel At-J, each modeled by a 3-component formulation. JetA-1 is composed of n-dodecane, methyl-cyclohexane and xylene each corresponding to the major hydrocarbon families found in real fuel. At-J is a synthetic drop in fuel composed of only branched chain alkanes, iso-octane, iso-dodecane and iso-hexadecane. Analytically Reduced Chemistry and multicomponent spray evaporation model coupled to the dynamic thickened flame turbulent combustion model are employed to understand the processes involved in turbulent spray flames in the LOTAR configuration. The objectives are to predict and understand the potential effects of staged vaporisation and consumption of the fuel components, and their impact on the spray flame structures. Simulations confirm the role of preferential evaporation in establishing and stabilising the reaction zone. JetA-1 evaporation zones extend deep into the rich burnt gasses resulting in a combustion regime with the possibility of droplet clusters burning individually. At-J which is more volatile, leads to complete combustion with the majority occurring due to the premixed lean reactions of the smaller pyrolysed components. The need to further include models capable of identifying and handling combustion regimes encountered in such spray flames is hence highlighted. This work is intended as a starting point for improving multicomponent spray modelling and requires additional experimental data for validation.

Flamelet Versus Detailed Chemistry Large Eddy Simulation for a Liquid-Fueled Gas Turbine Combustor: A Comparison of Accuracy and Computational Cost

Abstract A Honeywell liquid-fueled gas turbine test combustor at idle conditions is numerically investigated in simcenterstar-ccm+ version 2020.3. This work presents large eddy simulation (LES) results using both the flamelet generated manifold (FGM) and detailed chemistry combustion models. Both take advantage of a hybrid chemical (HyChem) mechanism which has previously demonstrated very good accuracy for real fuels such as Jet-A with only 47 species. The objective of this work is to investigate the ability of FGM and detailed chemistry modeling to capture pollutant formation in an aero-engine combustor. Comparisons for NOx, CO, unburned hydrocarbons (UHC), and soot are made, along with the radial temperature profile. To fully capture potential emissions, a soot moment model and Zeldovich NOx model are employed along with radiation. A comparison of results with and without chemistry acceleration techniques for detailed chemistry is included. Then, computational costs are assessed by comparing the performance and scalability of the simulations with each of the combustion models. It is found that the detailed chemistry case with clustering can reproduce nearly identical results to detailed chemistry without any acceleration if CO is added as a clustering variable. With the Lagrangian model settings chosen for this study, the detailed chemistry results compared more favorably with the experimental data than FGM; however, there is uncertainty in the secondary breakup parameters. Sensitivity of the results to a key parameter in the spray breakup model is provided for both FGM and complex chemistry (CC). By varying this breakup rate, the FGM case can predict CO, NOx, and UHC equally well. The smoke number, however, is predicted most accurately by CC. The cost for running detailed chemistry with clustering is found to be about four times that of FGM for this combustor and chemical mechanism.

Influence of Swirl and Primary Zone Airflow Rate on the Emissions and Performance of a Liquid-Fueled Gas Turbine Combustor

This paper presents the results of an experimental study on the influence of swirl number (S) and primary zone airflow rate on the temperature, emission indices of the pollutants, and combustion efficiency in an atmospheric pressure liquid-fueled gas turbine (GT) combustor, equipped with a swirling jet air blast atomizer and operated with Jet A1 fuel. Experiments were conducted at three primary zone air flow rates and three swirl numbers (0.49, 0.86, and 1.32). For all the cases, it was found that the NOx emissions were very low (< 2 g/kg of fuel). At all the swirl numbers, an increase in primary zone airflow led to a nonmonotonous variation in CO while minimally affecting the NOx emissions. However, increase in the swirl number generated relatively higher NOx and lower CO owing to higher temperature resulting from efficient combustion caused by a superior fuel–air mixing. Also, the unburnt hydrocarbons (UHC) was quite high at S = 0.49 because of the unmixedness of fuel and air, and zero at S = 0.86 and 1.32. The combustion efficiency was very low (around 60%) at S = 0.49 while almost 100% at S = 0.86 and 1.32. The study conducted demonstrates a significant dependence of emissions and GT performance on the swirl number governed by the convective time scales and the residence time of the combustible mixture in the combustion zone.

Dual-pump coherent anti-Stokes Raman scattering system for temperature and species measurements in an optically accessible high-pressure gas turbine combustor facility

The development and implementation of a dual-pump coherent anti-Stokes Raman scattering (DP-CARS) system employing two optical sub-systems to measure temperature and major species concentrations at multiple locations in the flame zone of a high-pressure, liquid-fueled gas turbine combustor are discussed. An optically accessible gas turbine combustor facility (GTCF) was utilized to perform these experiments. A window assembly has been designed, fabricated, and assembled in the GTCF to allow optical access from three directions using a pair of thin and thick fused silica windows on each side. A lean direct injection (LDI) device consisting of an array of nine integrated air swirlers and fuel injectors was operated using Jet-A fuel at inlet air temperatures up to 725 K and combustor pressures up to 1.03 MPa. The DP-CARS system was used to measure temperature and CO2/N2 concentration ratio on single laser shots. An injection-seeded optical parametric oscillator (OPO) was used as a narrowband pump laser source in order to potentially reduce shot-to-shot fluctuations in the CARS data. Large prisms mounted on computer-controlled translation stages were used to direct the CARS beams either into the main leg optical system for measurements in the GTCF or to a reference leg optical system for measurements of the non-resonant spectrum and for alignment of the CARS system. The spatial maps of temperature and major species concentrations were obtained in high-pressure LDI flames by translating the CARS probe volume in the axial and vertical directions inside the combustor rig without loss of optical alignment.

Recent advances in combustion flow-field imaging measurements in high-pressure liquid-fueled gas turbine combustor concepts

Recent advances in combustion flow-field imaging measurements in high-pressure liquid-fueled gas turbine combustor concepts

Numerical study on heat and mass transfer in a liquid-fueled gas turbine combustor

A two-dimensional spray combustion code is developed for investigating the spray flame in a gas turbine combustor. The modified K-ε model is used to describe the turbulent flow field and the generalized Rosin-Rammler equation is used to evaluate the fuel droplet size distribution in the spray. The effects of the inlet turbulent kinetic energy K o and dissipation rate ε o on the flow velocity and the length of recirculation zone are studied. Compared with results in the isothermal flow, the recirculation strength will increase, but the length of the recirculation zone will decrease in reacting flow case. Also, the influence of bluff-body size on velocity, temperature, fuel/oxygen concentration, and droplet distribution profiles is studied in detail.