Numerical Modeling of an Axisymmetric Trapped Vortex Combustor

The paper consists in modelling and simulation of the combustion in a turbojet engine in order to find optimal characteristics of the burning process and the optimal shape of combustion chambers. The main focus of this paper is to find a new configuration of the aircraft engine combustion chambers, namely an engine with two main combustion chambers, one on the same position like in classical configuration, between compressor and turbine and the other, placed behind the turbine but not performing the role of the afterburning. This constructive solution could allow a lower engine rotational speed, a lower temperature in front of the first stage of the turbine and the possibility to increase the turbine pressure ratio by extracting the flow stream after turbine in the inner nozzle. Also, a higher thermodynamic cycle efficiency and thrust in comparison to traditional constant-pressure combustion gas turbine engines could be obtained.

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“…Figure 7 shows the level of ignition energy of various vaporized fuel-air mixtures as a function of equivalence ratio [12,13].…”

Section: Combustion Chamber Modelmentioning

confidence: 99%

An Extended Combustion Model for the Aircraft Turbojet Engine

Rotaru

Andres-Mihăilă

Matei

2014

International Journal of Turbo &Amp; Jet-Engines

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Numerical simulation of cavity flow structure in an axisymmetric trapped vortex combustor

Kumar

Mishra

2012

Aerospace Science and Technology

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Determination of Criteria for Flame Stability in an Annular Trapped Vortex Combustor

Xavier

Pires

Vandel

et al. 2015

Volume 4B: Combustion, Fuels and Emissions

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Development of lean premixed (LP) combustion is still a challenge as it results in considerable constraints for the combustor design. Indeed, new combustors using LP combustion are more prone to flashback, blow-off, or even thermo-acoustic instabilities. A detailed understanding of mechanisms leading to such extreme conditions is then crucial to reduce pollutant emissions, widen the range of operating conditions, and reduce design time. This paper reports the experimental study of an innovative LP trapped vortex combustor (TVC). The TVC concept uses a recirculating rich flow trapped in a cavity to create a stable flame that continuously ignites a main lean mixture passing above the cavity. This concept gave promising performances but some workers highlighted the existence of combustion instabilities for some operating conditions. Detailed studies have therefore been carried out in order to understand the occurrence of these drastic operating conditions. Results showed that the cavity flow dynamics in conjunction with the location of the interfacial mixing zone (between the cavity and the mainstream) were the driving forces to obtain stable combustion regimes. The goal of this work has been to take advantage of these detailed recommendations to determine stability maps, trends, and dimensionless parameters which could be easily used as early-design rules. For this reason, the study introduced a simple and robust criterion, based on the global pressure fluctuation energy. The latter was used to distinguish stable and unstable modes. An aerodynamic momentum flux ratio and a chemical stratification ratio (taken between the cavity and the mainstream) were defined to scale all measurements. Results indicated that the mainstream velocity was critically important to confine the cavity and to prevent combustion instabilities. Remarkably, this trend was verified and even more pronounced for larger cavity powers. In addition, flame stabilization above the cavity resulted in the existence of specific stratification ratios, in order to obtain a soft gradient of gas composition between the rich and lean regions. Finally, a linear relation between the mainstream and cavity velocities became apparent, thereby making possible to simply predict the combustor stability.

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Numerical Modeling of an Axisymmetric Trapped Vortex Combustor

Cited by 6 publications

References 10 publications

An Extended Combustion Model for the Aircraft Turbojet Engine

An Extended Combustion Model for the Aircraft Turbojet Engine

Numerical simulation of cavity flow structure in an axisymmetric trapped vortex combustor

Determination of Criteria for Flame Stability in an Annular Trapped Vortex Combustor

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