Roberto Solana Pérez

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Solana Pérez

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Roberto

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0000-0001-5985-0446

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Publications1 - 10 of 11

Anchoring of premixed jet flames in vitiated crossflow with pulsed nanosecond spark discharge
Shcherbanev, Sergey; Morinière, Titouan; Solana Pérez, Roberto; et al. (2020)
Applications in Energy and Combustion Science
This paper deals with the effect of non-equilibrium plasma on the anchoring of a premixed jet flame in hot vitiated crossflow at atmospheric pressure. The turbulent vitiated crossflow was generated by an array of 4 ×4 premixed turbulent jet flames burning a lean mixture of air and natural gas at an equivalence ratio of 0.7 and a thermal power of 50 kW. The rich jet, with equivalence ratio jet varied between 1 and 3, was injected perpendicularly to the vitiated crossflow in a rectangular duct, with jet-to-crossflow momentum flux ratios ranging from 1 to 26. A nanosecond repetitively pulsed discharge was initiated in the vicinity of the windward side of the jet root. The effect of discharge power and repetition rate on the lift-off height of the flame is systematically analyzed for different combinations of jet equivalence ratio and momentum ratio. High speed chemiluminescence imaging of the flame and of the discharge shows that the initiation of the discharge on the windward side of the jet enhances the combustion chemistry, reducing the ignition time and the lift-off height of the flame. It is shown that the nanosecond repetitively pulsed discharges are able to maintain a robust anchoring of the flame for a wide range of operating conditions at relatively low electric power cost. Emission spectroscopy and OH-PLIF measurements were carried out to show that the plasma has both thermal and kinetic effects on flame anchoring respectively via intense localized heating of the mixture at temperatures exceeding 3000 K and via an intense production of OH radicals.
Flame stabilization with nanosecond repetitively pulsed discharge in a sequential combustor
Shcherbanev, Sergey; Dharmaputra, Bayu; Solana Pérez, Roberto; et al. (2022)
AIAA SciTech
This paper describes the experimental results of the flame dynamics stabilized by nanosecond repetitively pulsed discharge (NRPD) in a sequential combustor configuration. In such configuration of the combustor, two flame regions are organized sequentially: (i) first stage flame and (ii) second-stage sequential flame placed downstream of the first one. The sequential flame is located downstream of the injection of the dilution air and the second stage fuel into the hot vitiated products of the first stage flame. Several operation conditions of the second stage flame were considered in the present paper. The parameters of the first stage flame and amount of the dilution air were fixed while the second stage fuel injection was composed of natural gas/H2 mixture with different fractions of hydrogen. It is shown that the flame anchoring and combustion dynamics is significantly affected by the amount of hydrogen and mean power of the NRPD. Thermal effect of the plasma was studied with optical emission spectroscopy. Namely, the temperature increase due to the fast gas heating was measured during applied high-voltage pulses. It was shown that, for a mean vitiated flow temperature of 1000K, the temperature increase due to nanosecond pulse discharge can reach up to 2100K. The coupling of the gas flow with NRPD was identified for different frequencies and amplitudes of applied pulses. It was found that for high pulse repetition frequency (PRF>40 kHz) the discharge propagation and the parameter of the plasma have a cumulative effect. Spatially resolved electron density and mean gas temperature in the plasma region were measured in order to characterize the flow-discharge coupling in the flow direction. High speed OH chemiluminescence is used for quantitative analysis of the ignition and stabilization of the second stage flame.
Morphology and dynamics of a premixed hydrogen-methane-air jet flame in hot vitiated turbulent crossflow
Solana Pérez, Roberto; Miniero, Luigi; Shcherbanev, Serge; et al. (2020)
Proceedings of ASME Turbo Expo 2020 Turbomachinery Technical Conference and Exposition GT2020 September 21-25, 2020, Virtual, Online
The effect of hydrogen enrichment of a premixed hydrogen-methane-air jet in hot vitiated crossflow was studied at atmospheric condition. The hot turbulent vitiated crossflow is generated by a symmetric array of 4 4 jet flames burning a lean mixture of natural gas and air in fully premixed condition at equivalence ratio phi = 0.7 and total thermal power of 50 kW. This crossflow is then used to ignite the premixed perpendicular jet of hydrogen-methane-air at ambient temperature. Three jet parameters are varied to study the effect of hydrogen addition on the flame morphology and estabilization mechanism: the hydrogen mass fraction of the H2/CH4 fuel blend (x = 0-100%), the jet equivalence ratio (phi = 0.8-2.0) and the jet-to-crossflow momentum ratio (J = 3-12). High-speed hydroxyl (OH) chemiluminescence is used to obtain the time-resolved imaging of the reactive jet and to compute its time averaged morphology. OH planar laser induced fluorescence (OH-PLIF) is used to acquire OH concentration fields at the jet center plane. The jet morphology is analyzed by considering its mean trajectory, extracted from the experimental data and fitted with empirical correlations available from the literature. New correlations are proposed for the flame length, width and center of gravity as function of the hydrogen content. It is shown that with increasing hydrogen fraction, the flame is shortened and more compact, and it stabilises close to the jet root. Another finding of this work is the reattachment of the flame at the base of the windward jet shear layer when hydrogen fraction is increased. Robust flame anchoring is observed for H2 mass fractions of the CH4/H2 fuel blend that exceed 50%. Moreover, it is shown using instantaneous OH-PLIF images that for these conditions of increasing hydrogen concentration, the windward shear layer features larger-scale coherent structures that govern the aerodynamics of the reactive premixed jet in turbulent vitiated crossflow.
Simulation of the self-ignition of a cold premixed Ethylene-Air jet in hot vitiated crossflow
Solana Pérez, Roberto; Schulz, Oliver; Noiray, Nicolas (2019)
Previous studies investigated experimentally and numerically the stabilization mechanism of an existing flame in a reactive jet in cross flow (RJICF) con figuration. The aim of this paper is to analyze the transient self-ignition phenomenon when transitioning from a non-reactive to a reactive JICF. A premixed ethylene-air mixture (Equivalence ratio = 1.2) at 300 K is injected into a hot vitiated cross flow at 1500 K. A compressible 3D large eddy simulation (LES) using analytically reduced chemistry (ARC) is performed. The numerical scheme and LES were previously validated against experiments. Simulations show the sudden outbreak of low heat release patches by autoignition in scattered positions of the jet windward region. In this region autoignition conditions are met, i.e. very lean most reactive mixture fractions, high temperatures and low velocity magnitudes. These patches grow and expand by a chain reaction along the windward side, they laterally wrap the jet and extend into the recirculation region. The intensity of heat release in the windward region grows exponentially in time due to the autoignition cascade phenomenon. In this phenomenon heat release diffuses downstream contributing to a reduction of the autoignition time values in the inner richer regions which are accompanied by stronger heat release. Eventually the visible flame starts by autoignition. It appears lifted at the windward side and propagates to the jet leeward side from the laterals and top zones of the jet.
Combustion regime transition of H2 flames during steady and transient operation of a sequential combustor
Solana Pérez, Roberto; Shcherbanev, Serge; Dharmaputra, Bayu; et al. (2023)
Proceedings of the Combustion Institute
The combustion regime transition in a sequential burner (SB) supplied with H (48 kW) is experimentally studied during steady and transient operation. The test rig is a simplified model of an industrial sequential combustor featuring two-staged combustion chambers separated by a mixing section in which dilution air and fuel are injected. The temperature, velocity and composition of the hot vitiated gas flowing through the SB are defined by the products from the first stage (30 kW natural gas-air flame at equivalence ratio 0.7), and by the mass flow of dilution air. To study the combustion regime transition during steady operation of the combustor, is fixed at several values between 22 g/s and 7 g/s. For transient operation investigations, is suddenly changed between 20 and 7 g/s, which triggers a fast transition of the combustion mode. High-speed hydroxyl radicals OH chemiluminescence is used to characterize the combustion process, and optical emission spectroscopy (OES) and tunable diode laser absorption spectroscopy (TDLAS) are respectively used to extract mean and time-resolved temperatures of the vitiated gas in the SB. In particular, we investigate the transition from a propagation-driven turbulent flame anchored at the inlet of the sequential combustion chamber, to a flame stabilized by autoignition inside the mixing section of the burner when the dilution air mass flow is suddenly reduced. Zero-dimensional (0D) simulations are used to analyze the underlying combustion regime transition. A 0D reactor network is developed and calibrated with the experimental data. This simplified low-order model predicts well the flame location for both steady and transient operation. Moreover, the good agreement between the numerical results and the experimental data demonstrates that time-resolved TDLAS successfully enables measurement of small temperature variations in the vitiated flow associated with non-perfect mixing of the different streams in the SB.
Effect of plasma-flow coupling on the ignition enhancement with non-equilibrium plasma in a sequential combustor
Shcherbanev, Serge; Malé, Quentin; Dharmaputra, Bayu; et al. (2022)
Journal of Physics D: Applied Physics
The effect of the regime of nanosecond repetitively pulsed discharges (NRPDs) on ignition and stabilization of a natural-gas/hydrogen/air flame in the sequential stage of a lab-scale atmospheric pressure sequential combustor is investigated experimentally. Electrical parameters of the NRPDs are characterized by measuring voltage, current, and deposited energy. Fast gas heating (FGH) of the nanosecond discharges is measured in a single pulse regime and validated by means of 0D kinetic modelling. It was found that the conventional scheme for energy release from internal degrees of freedom adequately describes the dynamics of FGH in vitiated hot environment diluted with air. Short-gated ICCD imaging and spatially-resolved emission spectroscopy are used to identify the coupling between the NRPDs and the vitiated hot flow. The effectiveness of the NRPDs actuation is assessed through the OH* chemiluminescence images of the sequential flame. The distance of the center of gravity of the sequential flame to the outlet of the mixing channel is evaluated, with and without plasma actuation. The effect of fuel reactivity on plasma effectiveness is also studied by varying the fraction of hydrogen in the fuel blend of the second stage of the combustor. The results show that the glow NRPDs regime allows strengthening the flame anchoring for the most reactive blends considered in this work, while the spark NRPDs is required for the ignition and prevention of lean blow-out of the flame for the least reactive fuel blends which exhibit low fractions of hydrogen.
The ignition process of a premixed reactive jet in hot vitiated crossflow
Solana Pérez, Roberto; Schulz, Oliver; Noiray, Nicolas (2019)
17th International Conference on Numerical Combustion. Book of Abstracts
The transient ignition process of a premixed methane-air jet that is injected into a hot vitiated cross-flow is investigated by means of LES with analytically reduced chemistry. Premixed reactive jet in hot crossflow (RJICF) configurations are important for modern combustion systems for power applications. The ignition process occurs without external heat source and it is here investigated by comparing numerical simulations to experimental data (PIV and OH LIF). The LES gives access to the full spatio-temporal evolution of the reaction zone, and allows to identify regions governed by autoignition and by flame propagation. After the transient flame anchoring, the turbulent RJICF structure is also characterised. The reaction zone stretches over a wide range of mixture fractions from the most reactive one to the stoichiometry.
Flame anchoring of a premixed jet flame in vitiated crossflow using nanosecond repetitively pulsed discharge
Shcherbanev, Sergey; Morinière, Titouan; Solana Pérez, Roberto; et al. (2021)
Proceedings Volume
This paper aims to investigate the effects of nanosecond repetitively pulsed discharge on the dynamics and on the anchoring of a premixed jet flame in hot vitiated cross flow. The lift-off height of the flame is studied for different mean plasma power, jet equivalence ratio and momentum ratio. It was found that the effect of plasma on the flame anchoring increases while decreasing jet equivalence ratio at fixed discharge mean power. Instantaneous and averaged OH-PLIF images showed the production of OH radicals on the windward side of the jet as well as their propagation along and around the windward jet shear layer over 2 to 5 jet diameters depending on the jet equivalence ratio and jet-to-cross-flow momentum ratio. It was shown that the presence of the NRPD on the windward side increases the overall OH density on both the windward and the leeward side of the jet. The chemical and thermal effects are discussed based on results of OH-PLIF images and emission spectroscopy. It is shown that rather low mean power (comparing to the flame power) discharge can serve as an efficient instrument for flame anchoring and stabilization.
Effect of Mixing on the Anchoring and Combustion Regimes of Pure Hydrogen Flames in Sequential Combustors
Solana Pérez, Roberto; Shcherbanev, Serge; Ciani, Andrea; et al. (2023)
Journal of Engineering for Gas Turbines and Power
In this work, we perform an experimental study of the combustion of pure hydrogen in the sequential stage of a generic combustor. This academic test rig is a simplified model of an industrial sequential combustor. The sequential fuel is injected using different injector geometries. The composition and temperature of the hot stream at the inlet of the sequential burner are defined by the mass flows of the hot combustion products from the first stage (30 kW natural gas–air flame with equivalence ratio of 0.7) and of the dilution air. This temperature is varied between 1100 K and 850 K by modifying the dilution air mass flow in order to study the different combustion regimes of the sequential hydrogen flame. High-speed imaging of OH radicals chemiluminescence is performed with optical emission spectroscopy to measure vitiated gas temperatures. In particular, we investigate the transition from a flame anchored in the sequential combustion chamber, to the situation where it stabilizes upstream into the mixing section, when the inlet flow temperature is increased. Of particular interest is the increasing rate of formation of auto-ignition kernels in this transition process. The underlying combustion regime change is analyzed with 0D reactor simulations, and the limitations of such a simplified low-order model of the flame location are discussed. The effects and importance of the mixing process between fresh fuel and the hot vitiated coflow are examined. Two different injectors are compared under the same operating conditions that create different flow structures along the mixing section. As a result of that, they provide different degrees of mixing between the hydrogen and the hot vitiated flow and allow to demonstrate the impact of mixing quality on the flame morphology.
Simulation of the Self-Ignition of a Cold Premixed Ethylene-Air Jet in Hot Vitiated Crossflow
Solana Pérez, Roberto; Schulz, Oliver; Noiray, Nicolas (2021)
Flow, Turbulence and Combustion
The aim of this paper is to analyze the self-ignition of a jet fame in hot vitiated cross fow using Large Eddy Simulation with analytically reduced chemistry. A rich premixed ethylene-air mixture at 300 K is injected into a hot vitiated crossfow at 1500 K. The simulated reacting fow steady-state was validated against experiments in previous publications and the focus of the present work is the transient self-ignition of the jet. It is shown that spontaneous ignition occurs at very lean mixture fractions in the form of reacting patches in the windward jet mixing layer. These patches grow, laterally wrap the jet and extend into the recirculation region. Chemical explosive mode analysis is performed to identify the chemically active regions that are precursors of the patches undergoing spontaneous ignition. It is shown that the self-ignition occurs at very lean fuel concentrations regions, which are leaner and hotter than the most reactive mixture fraction of the jet and crossfow. This is explained by the fact that the scalar dissipation is signifcantly lower in these very lean regions. Ultimately, the peak heat release moves toward the richer regions and an autoignition cascade governs the steady state fame anchoring.

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Roberto Solana Pérez

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