In this numerical study, supersonic combustion of kerosene in three model combustor configurations is investigated. To this end, 3-D, compressible, turbulent, nonreacting, and reacting flow calculations with a single step chemistry model have been carried out. For the nonreacting flow calculations, the droplet diameter distribution at different axial locations, variation of the Sauter mean diameter, and the mixing efficiency for three injection pressures are presented and discussed. In addition, the effect of turbulent dispersion on the mixing efficiency is studied using a stochastic model in conjunction with the two-equation shear stress transport k-ω turbulence model. For the reacting flow calculations, contours of heat release and axial velocity at several axial locations are used to identify regions of heat release inside the combustor. Combustion efficiency predicted by the present results is compared with earlier predictions for all the combustor models. Furthermore, the predicted variation of static pressure along the combustor top wall is compared with experimental data reported in the literature. Calculations show that the penetration and spreading of the fuel increases with an increase in the injection pressure. Predicted values of the combustion efficiency are more realistic when the spray model is used for modelling the injection of the fuel. The importance of the mixing process, especially for a liquid fuel such as kerosene, on the prediction of heat release is discussed in detail.

Mixing and combustion characteristics of kerosene In a model supersonic combustor

In this numerical study, supersonic combustion of liquid kerosene in a strut-based combustor is investigated. To this end, three-dimensional compressible, turbulent, nonreacting and reacting flow calculations with a single-step chemistry model have been carried out. For the nonreacting flow calculations, fuel droplet trajectories, degree of mixing,andmixingefficiencyarepresentedanddiscussed.Forthereacting flowcalculations,contoursofheatrelease and Mach number and the variation of combustion efficiency, total pressure loss, and thrust profile along the combustor length are used to identify the regions of mixing and heat release inside the combustor. Furthermore, the predicted variation of static pressure along the combustor top wall is compared with experimental data. The significance of the lateral spread of the fuel and the extent of the mixing process, especially for a liquid fuel such as kerosene, on the prediction of heat release is discussed in detail.

Numerical investigation of the supersonic combustion of kerosene in a strut-based combustor

Investigation on supersonic combustion of hydrogen with variation of combustor inlet conditions

Mixing and combustion augmentation of the RBCC with different mixer configurations in ejector mode

Results from 3D, compressible, unsteady Favre-averaged calculations of transverse injection into a supersonic cross flow are reported. Four injector geometries, namely, circular, wedge, diamond, and chevron, have been investigated. The effectiveness of the chevron injector is demonstrated by comparing performance metrics, such as degree of mixing and total pressure loss, against those of the other injectors. The results show that the chevron injector provides better mixing and spreading compared to other injectors, with almost the same total pressure loss. Furthermore, for the operating conditions studied, the chevron-penetration angle is shown to have a minimal impact on the mixing and the total pressure loss.

Transverse Injection Into a Supersonic Cross Flow Through a Circular Injector With Chevrons

Numerical simulations of the 3D reacting flow in a model supersonic combustor with kerosene as the fuel have been carried out. The combustor entry Mach number is nominally 2.5. Tetrahedral grids with wall y+ less than 75 have been used. Details of the flow field inside the combustor such as contours of static pressure, static temperature, species mass fraction, reaction rate and Mach number are discussed. Also, the variation of metrics such as combustion efficiency and total pressure loss along the length of the combustor are presented. Predicted values of wall static pressure along the top wall of the combustor are compared with previously reported experimental data. The calculations over predict the pressure rise due to combustion in the cavity region, but the overall pressure rise is predicted well.

Numerical simulation of the supersonic combustion of kerosene in a model combustor

In the present work, the influence of the turbulence model on the numerical predictions of supersonic combustion of hydrogen in a model combustor is investigated. Three dimensional, compressible, turbulent, reacting flow calculations using the Shear Stress Transport (SST) k – ω model have been carried out. The results are compared with earlier results obtained using the Spalart-Allmaras model. The effect of detailed chemistry on the predictions of heat release and combustion efficiency is also investigated for one injection scheme. The calculations show that the mixing and hence the heat release is over predicted by the SA model. Whereas, the peak values for pressure and temperature are predicted better by the SST k – ω model. This investigation demonstrates the importance of the use of a two equation turbulence model over a one equation model for studying such complex flow phenomena.

A comparison of the numerical predictions of the supersonic combustion of Hydrogen using the S-A and SST k – ω models

Numerical simulations of round, compressible, turbulent jets at Mach 0.75 have been carried out. Two jets, one cold and hot, have been simulated. Overall Sound Pressure Levels (SPL) at far-field observer locations have been calculated using Ffowcs Williams-Hawkings equation. Axial and radial variation of the mean axial velocity, axial variation of u′u′½, v′v′½, radial variation of u′v′ and overall SPL levels are compared with experimental data reported in the literature. The potential core length is predicted well, but the predicted centreline velocity decay is faster than the measured value. The URANS calculations are able to predict the absolute values for the overall SPL, and the trends to within ±4dB of the experimental value for most of the receivers. The calculations predict the trends as well as absolute values of the variations of the spectral amplitude for receivers at 30Dj but not 50Dj.

Improved noise predictions from subsonic jets at Mach 0.75 using URANS calculations

In this paper, numerical simulations of a full scale concept supersonic combustor using kerosene fuel are presented. Results are reported first for a baseline model. These results are then used for identifying the shortcomings in this model, which allows improvements to be made. In particular, the spacing between the ramps is widened so that the heat addition is not confined to a short region and is distributed over a larger volume. Also the design of fuel supply lines has been reworked so that they do not obstruct the supersonic flow. Details of the flow field inside the combustor such as contours of static pressure, static temperature, species mass fraction, reaction rate and Mach number are discussed. Wall static pressure distribution along the top wall of the combustor is presented. Intricate details of the flow field such as separation zones, shocks and expansion fans and their interaction are also brought out. Finally, thrust developed by the combustor is calculated using two different methods.

Evaluation of a ramp cavity based concept supersonic combustor using CFD

Numerical simulations of the flow in a vapour ejector have been carried out. Real gas effects are accounted for in the calculations. Ejection as well as flow-through studies have been performed. Effects of the generator and evaporator temperatures and position of the primary nozzle have been investigated. Predicted values of the suction pressure and COP have been compared with experimental values reported in the literature. In addition, secondary flow area has also been evaluated and correlated with the COP. By tracking the sonic line and the edge of the primary stream and flow separation, insights on the gas dynamic and fluid dynamic aspects of the flow field and how they influence the entrainment of the secondary stream and consequently the COP are brought out. The study reveals that, in addition to the choking of the secondary stream, the expansion of the primary stream and the area available for the secondary stream also plays a key role in affecting the performance of the vapour ejector.

V. Babu

Papers

Numerical simulation of the supersonic combustion of kerosene in a model combustor

A comparison of the numerical predictions of the supersonic combustion of Hydrogen using the S-A and SST k – ω models

Improved noise predictions from subsonic jets at Mach 0.75 using URANS calculations

Evaluation of a ramp cavity based concept supersonic combustor using CFD

A numerical investigation of the compressible flow in the ejector of a vapour ejector refrigeration system