Spray flame structure in conventional and hot-diluted combustion regime

2015 ◽  
Vol 162 (3) ◽  
pp. 759-773 ◽  
Author(s):  
Hugo Correia Rodrigues ◽  
Mark J. Tummers ◽  
Eric H. van Veen ◽  
Dirk J.E.M. Roekaerts
2015 ◽  
Vol 19 (1) ◽  
pp. 21-34 ◽  
Author(s):  
Amir Mardani ◽  
Sadegh Tabejamaat

In this paper, turbulent non-premixed CH4+H2 jet flame issuing into a hot and diluted co-flow air is studied numerically. This flame is under condition of the moderate or intense low-oxygen dilution (MILD) combustion regime and related to published experimental data. The modelling is carried out using the EDC model to describe turbulence-chemistry interaction. The DRM-22 reduced mechanism and the GRI2.11 full mechanism are used to represent the chemical reactions of H2/methane jet flame. The flame structure for various O2 levels and jet Reynolds numbers are investigated. The results show that the flame entrainment increases by a decrease in O2 concentration at air side or jet Reynolds number. Local extinction is seen in the upstream and close to the fuel injection nozzle at the shear layer. It leads to the higher flame entertainment in MILD regime. The turbulence kinetic energy decay at centre line of jet decreases by an increase in O2 concentration at hot Co-flow. Also, increase in jet Reynolds or O2 level increases the mixing rate and rate of reactions.


2013 ◽  
Vol 316-317 ◽  
pp. 17-22 ◽  
Author(s):  
Cheng Tung Chong ◽  
Simone Hochgreb

A model gas turbine burner was employed to investigate spray flames established under globally lean, continuous, swirling conditions. Two types of fuel were used to generate liquid spray flames: palm biodiesel and Jet-A1. The main swirling air flow was preheated to 350 °C prior to mixing with airblast-atomized fuel droplets at atmospheric pressure. The global flame structure of flame and flow field were investigated at the fixed power output of 6 kW. Flame chemiluminescence imaging technique was employed to investigate the flame reaction zones, while particle imaging velocimetry (PIV) was utilized to measure the flow field within the combustor. The flow fields of both flames are almost identical despite some differences in the flame reaction zones.


Author(s):  
S. K. Aggarwal ◽  
S. Chitre

Computations are reported on the detailed structures of unconfined turbulent combusting sprays. Favre-averaged gas-phase equations are used and a k-ε-g turbulence closure model is utilized. Using a conserved scalar approach and assuming the form of probability density function to be a clipped Gaussian, the thermodynamic scalar variables are calculated from a partial equilibrium model. The major features of the liquid-phase model are that a stochastic random-walk approach is used to represent the effect of gas-phase turbulence on droplet trajectory and vaporization, the variable-property effects are considered in a comprehensive manner, and a conduction-limit mode is employed to represent the transient liquid-phase processes. This two-phase model is used to study the structure of an unconfined methanol spray flame. Important observation is that the turbulent spray flame structure is significantly different, both quantitatively and qualitatively, from that of the corresponding gaseous diffusion flame. In addition, the spray flame exhibits a strong sensitively to the transient liquid-phase processes. The latter result is interesting since, in an earlier computational study for an evaporating spray, the vaporization behavior for the same liquid fuel indicated only a weak sensitivity to these processes.


Author(s):  
M. Vicentini ◽  
R. Lecourt ◽  
O. Rouzaud ◽  
V. Bodoc ◽  
O. Simonin

At ONERA Fauga-Mauzac center, a new air-breathing propulsion test setup, Prométhée-LACOM, has been recently developed. In this paper, both nonreacting and reacting two-phase flows (nonpremixed spray) were investigated. Under reactive conditions, simultaneous OH-PLIF (planar laser-induced fluorescence) and Mie scattering imaging were implemented in order to characterize the spray flame structure. The different behaviors observed in this study seem to support the existence of spray combustion regimes. Moreover, statistical analysis was performed on the spatial distribution of droplets and indicated that the center-to-center interdroplet distance (nearest neighbor) could be described by means of a perfectly random distribution.


2017 ◽  
Vol 36 (2) ◽  
pp. 2567-2575 ◽  
Author(s):  
F. Shum-Kivan ◽  
J. Marrero Santiago ◽  
A. Verdier ◽  
E. Riber ◽  
B. Renou ◽  
...  

Author(s):  
Sivaji Seepana ◽  
Sreenivas Jayanti

In the present paper, the stability of the new oxyfuel combustion regime titled as Intermediate temperature Diluted Oxygen Combustion (INDOCS) has been demonstrated theoretically. The operating conditions for the INDOCS are different from those of conventional oxyfuel combustion: the concentration by mass of oxygen in the oxidant stream is between 16 to 20% by mass (as opposed to 24% by mass in conventional oxyfuel combustion) and the temperature of the oxidant at entry to the furnace is in the range of 600 to 850 K (as opposed to an ambient temperature of about 300 K in conventional oxyfuel combustion). The method relies on the well-established fact that the stability of the flame increases with preheating of the oxidant (as demonstrated in High Temperature Air Combustion (HITAC) and FLAMELESS combustion regimes). The attendant high peak temperature of the flame can be reduced, to minimize NOx formation, by diluting the oxygen concentration. The overall benefits of this method are stable combustion at diluted oxygen concentrations, lower NOx (if N2 is present due to incomplete separation of oxygen from air), higher concentration of carbondioxide in the flue gases for a more efficient carbon sequestration. Flame structure calculations using the flamelet model of combustion with 35-step methane-air simplified reaction mechanism are used to demonstrate the stability of the flame. Simulations have also been carried out for the geometry of the 300 kW IFRF burner test facility; these show that the decreasing concentration of H and OH radicals in the quarl zone with increasing dilution by CO2 is counteracted by increasing the temperature of the oxidant. One of the principal advantages of this method is that, unlike in the case of HiTAC, the preheat requirements are mild which can be achieved by mixing part of the flue gas with the oxygen separated from air. It can be therefore readily implemented as a retrofitting measure in existing coal-fired plants.


Fuel ◽  
2014 ◽  
Vol 115 ◽  
pp. 551-558 ◽  
Author(s):  
Cheng Tung Chong ◽  
Simone Hochgreb
Keyword(s):  

Author(s):  
B. Franzelli ◽  
A. Vié ◽  
B. Fiorina ◽  
N. Darabiha

Accurate characterization of swirled flames is a key point in the development of more efficient and safer aeronautical engines. The task is even more challenging for spray injection systems. On the one side, spray interacts with both turbulence and flame, eventually affecting the flame dynamics. On the other side, spray flame structure is highly complex due to equivalence ratio inhomogeneities caused by the evaporation process. Introducing detailed chemistry in numerical simulations, necessary for the prediction of flame stabilization, ignition and pollutant concentration, is then essential but extremely expensive in terms of CPU time. In this context, tabulated chemistry methods, expressly developed to account for detailed chemistry at a reduced computational cost in Large Eddy Simulation of turbulent gaseous flames, are attractive. The objective of this work is to propose a first computation of a swirled spray flame stabilized in an actual turbojet injection system using tabulated chemistry. A Large Eddy Simulation of an experimental benchmark, representative of an industrial swirl two-phase air/kerosene injection system, is performed using a standard tabulated chemistry method. The numerical results are compared to the experimental database in terms of mean and fluctuating axial velocity. The reactive two-phase flow is deeper investigated focusing on the flame structure and dynamics.


Sign in / Sign up

Export Citation Format

Share Document