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R.P. Sampat

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Authored

Operating Characteristics of a Flameless Combustor Obtained By Experiments Informed Modelling

Conference paper (2022) - R.P. Sampat, N.G.H. Goselink, F.F.J. Schrijer, A. Gangoli Rao

Flameless Combustion is an interesting low NO_x combustion technology for gas turbine engines. In order to design systems for stringent performance standards, it is important to understand emission formation in this regime. To this end, the characteristics of a combu ...

Modeling Pollutant Emissions of Flameless Combustion With a Joint CFD and Chemical Reactor Network Approach

Journal article (2019) - A.A.V. Augusto Viviani Perpignan, R.P. Sampat, A. Gangoli Rao

The Flameless Combustion (FC) regime has been pointed out as a promising combustion technique to lower the emissions of nitrogen oxides (NOx) while maintaining low CO and soot emissions, as well as high efficiencies. However, its accurate modeling remains a challenge. The prediction of pollutant species, especially NOx, is affected by the usually low total values that require higher precision from computational tools, as well as the incorporation of relevant formation pathways within the overall reaction mechanism that are usually neglected. The present work explores a multiple step modeling approach to tackle these issues. Initially, a CFD solution with simplified chemistry is generated [both the Eddy Dissipation Model (EDM) as well as the Flamelet Generated Manifolds (FGM) approach are employed]. Subsequently, its computational cells are clustered to form ideal reactors by user-defined criteria, and the resulting Chemical Reactor Network (CRN) is subsequently solved with a detailed chemical reaction mechanism. The capabilities of the clustering and CRN solving computational tool (AGNES—Automatic Generation of Networks for Emission Simulation) are explored with a test case related to FC. The test case is non-premixed burner based on jet mixing and fueled with CH4 tested for various equivalence ratios. Results show that the prediction of CO emissions was improved significantly with respect to the CFD solution and are in good agreement with the experimental data. As for the NOx emissions, the CRN results were capable of reproducing the non-monotonic behavior with equivalence ratio, which the CFD simulations could not capture. However, the agreement between experimental values and those predicted by CRN for NOx is not fully satisfactory. The clustering criteria employed to generate the CRNs from the CFD solutions were shown to affect the results to a great extent, pointing to future opportunities in improving the multi-step procedure and its application.@en

Contributed

The design and commissioning of an enclosed jet-in-hot-coflow setup for the investigation of flameless combustion

Master thesis (2023) - T. van den Berg, A. Gangoli Rao, R.P. Sampat

Flameless combustion is a combustion regime which results in drastically lower ABe emissions. ABe has been found to influence global warming through its interactions with ozone chemistry and, exposure to this gas has been found to have adverse health effects on humans. The jet-in-hot-coflow design is well suited for studying flame morphology and the coflow composition can easily be changed. In most of these setups in literature, the reaction zone is uncontained, allowing ambient air to enter the region of interest. Furthermore, there is currently a lack of emissions data over a wide range of operating conditions.

This project included the engineering, design, and development of an enclosed jet-in-hot-coflow setup as well as an analysis of the flow field and combustion characteristics through experiments. Measurements were done using PIV, suction probe gas analyzer, thermocouples, and chemiluminescence imaging. Experiments were done with methane-air mixtures in the central jet and the coflow consisted of hot burnt products of methane-air combustion with the addition of external diluents such as 6B2 and A2. One of the most interesting results was that ABe reburning was observed in the reaction zone produced by the central jet, which was found to be correlated to the 6B concentration in the combustion chamber. The addition of 6B2 and A2 as diluents in the coflow resulted in a longer combustion zone and reduced temperatures in the combustion chamber, leading to decreased ABe production, and increased reburning. Further, the impact of oxygen concentration, equivalence ratio, and coflow temperature on product species formation was also analysed. The results indicate that combustion zone growth and temperature effects are balanced for lower jet speeds, while for others, the effects of increasing combustion zone size and distribution with increasing equivalence ratio result in reburning becoming more dominant. Improvements are recommended, such as redesigning the central jet cooling assembly, integrating a secondary burner inside the mixing duct, implementing a pre-heating system for temperature control, and using high-speed imaging techniques for capturing flame development and ignition behaviour.