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Article

Comparative Analysis of Flame Propagation and Flammability Limits of CH4/H2/Air Mixture with or without Nanosecond Plasma Discharges

Department of Engineering for Innovation, University of Salento, Via per Monteroni, 73100 Lecce, Italy
*
Author to whom correspondence should be addressed.
Aerospace 2023, 10(3), 224; https://doi.org/10.3390/aerospace10030224
Submission received: 31 January 2023 / Revised: 19 February 2023 / Accepted: 23 February 2023 / Published: 25 February 2023

Abstract

:
This study investigates the kinetic modeling of CH4/H2/Air mixture with nanosecond pulse discharge (NSPD) by varying H2/CH4 ratios from 0 to 20% at ambient pressure and temperature. A validated version of the plasma and chemical kinetic mechanisms was used. Two numerical tools, ZDPlasKin and CHEMKIN, were combined to analyze the thermal and kinetic effects of NSPD on flame speed enhancement. The addition of H2 and plasma excitation increased flame speed. The highest improvement (35%) was seen with 20% H2 and 1.2 mJ plasma energy input at ϕ = 1. Without plasma discharge, a 20% H2 blend only improved flame speed by 14% compared to 100% CH4. The study found that lean conditions at low flame temperature resulted in significant improvement in flame speed. With 20% H2 and NSPD, flame speed reached 37 cm/s at flame temperature of 2040 K at ϕ = 0.8. Similar results were observed with 0% and 5% H2 and a flame temperature of 2200 K at ϕ = 1. Lowering the flame temperature reduced NOx emissions. Combining 20% H2 and NSPD also increased the flammability limit to ϕ = 0.35 at a flame temperature of 1350 K, allowing for self-sustained combustion even at low temperatures.

1. Introduction

Combustion is a crucial factor in air transportation due to the high energy density of liquid fuels. However, the low efficiency of current aeroengines and the production of harmful emissions contributing to climate change are pressing issues. To comply with strict emission regulations set by CAEP (Committee on Aviation Environmental Protection) and improve fuel efficiency, various international organizations are exploring the concept of lean combustors.
Lean fuel burning is an effective solution for reducing NOx emissions by lowering flame temperature. However, these low temperature flames are prone to critical instabilities that can lead to re-ignition and flame blowout issues [1,2]. To address issues with methane combustion, the addition of a more reactive and cleaner fuel such as hydrogen could be a practical solution [3]. Blending methane with hydrogen has been shown to enhance performance and reduce emissions without modifying existing combustors [4]. Hydrogen is a carbon-free fuel with low ignition energy, a wide flammability range, fast flame propagation, and high reactivity [3]. Several studies in the past [3,4,5,6] have focused on the impact of hydrogen on the flame speed of CH4/H2 mixtures. Halter et al. [5] studied the effect of hydrogen content and inlet pressure on the laminar flame speed of CH4/H2 flames, with results indicating that the laminar flame speed improved with increasing hydrogen content and decreased with increasing inlet pressure.
Mandilas et al. [6] studied the impact of hydrogen on iso-octane-air and methane mixtures in both laminar and turbulent conditions. They found that using hydrogen led to earlier flame instabilities but improved laminar flame speed at lean limits in turbulent combustion. Adding hydrogen to methane slightly improved reactivity at lean conditions, but also increased complexities, safety issues, and thermoacoustic instabilities [3,4,5,6]. Flame speed was slightly better at lean compared to rich conditions [4]. Non-thermal plasma combustion can improve flame stability, flame speed, and lean blowout limits. NTP enhances combustion through kinetic, thermal and momentum effects [7]. NTP improves combustion through three mechanisms: kinetic (creation of active particles from fuel decomposition), thermal (increased fuel/air mixture temperature), and momentum (ionic wind and flow motion from electro-hydrodynamic forces) [8].
Among NTP technologies, nanosecond plasma discharge (NSPD) has gained attention due to its ability to effectively produce excited states and active particles [9,10]. NSPD also rapidly heats the gas, which accelerates combustion [11,12]. Despite numerous research studies on NTP combustion [1], commercialization is only possible with the development of accurate numerical models for plasma chemistry in combustion. Our group [12,13,14,15] has studied CH4/air mixtures with NSPD for flame propagation and ignition enhancement. We compared ignition delay, flame speed, and flammability limits under different conditions and found that NSPD improved ignition, flame propagation, and flammability limits due to the production of neutral radicals and increased mixture temperature. The improvements were primarily due to NSPD’s kinetic effects. Prior studies on NSPD have individually considered H2/air and CH4/air mixtures.
While initial studies have explored the kinetics of NSPD, a comprehensive understanding of plasma mechanisms for CH4/H2/air mixtures is still lacking. It has been shown that the evolution of active particles over time provides the most accurate analysis of plasma kinetics [16,17].
This paper presents a study of CH4/H2/air with nanosecond plasma discharge. There is currently no numerical study available on methane blended hydrogen plasma-assisted combustion. Both plasma and combustion kinetics were analyzed using validated mechanisms and compared to previously published experimental data. The impact of NSPD and hydrogen content on flame propagation and flammability limits in methane/air mixtures was studied. A comparative analysis of flame speed enhancement with and without plasma actuation was performed using different methane blended hydrogen ratios.

2. Numerical Procedure and Kinetic Modelling

2.1. Numerical Procedure

Numerical analyses were conducted using two solvers: ZDPlasKin (0D Plasma kinetic solver) [18] and CHEMKIN (Chemical kinetic solver) [19]. The methodology is shown in Figure 1 and explained in [13]. ZDPlasKin was used to analyze the kinetic and thermal effects of NSPD in CH4/H2/Air mixture. BOLSIG+ was linked to ZDPlasKin to predict the temporal evolution of excitation states and the reactions producing free radicals/active particles. It has been assumed that the non-equilibrium plasma created from a CH4/H2/air mixture at atmospheric pressure is uniformly distributed, which is a similar assumption to what was previously executed in [13]. Although the nanosecond pulsed plasma combustion process is three-dimensional and not homogeneous, we used a simplified homogeneous model. To investigate the effects of plasma CH4/H2/air products on flame speed and flammability limits, we used the plasma products of CH4/H2/air as the inlet domain of the reactor.
ZDPlasKin boundary conditions were set as ambient temperature and pressure, fixed EN and electron number density, and initial CH4/H2/Air composition. The simplified homogeneous model was used as in [20]. ZDPlasKin simulation was performed using the integral mean value of EN obtained from experiments, about 200 Td over 10−6 s, as shown in Figure 2. Experimental setup and EN estimation are described in [13]. The gas temperature was predicted using equations from [18]. The adiabatic gas temperature was calculated from the energy conservation equation and reallocation of electrical power Pext to electron translational degree Pelec, gas internal degree Pchem, and gas Pgas:
P e x t = P g a s + P e l e c + P c h e m                  
The above equation can be described below.
P e x t = e [ N e ] v e E                                                  
P g a s = 1 γ 1 + d ( N T g a s ) d t              
P e l e c = 3 2 + d ( [ N e ] T e ) d t                      
P c h e m = i n Q i + d [ N i ] d t      
where E is the reduced field, e is the elementary charge, Te is the electron temperature, ve is the drift velocity of electrons [Ne] is the electron density, N is the total gas density, γ = 1.2 is the specific gas heat ratio and Qi is the potential energy of species i.
The results gained from the ZDPlaskin solver in terms of neutral and excited species (at a time of 0.5 ms because the residence time is too short that autoignition chemistry does not significantly influence the reactants compositions), and the gas temperature of the activated region were introduced into the CHEMKIN solver to investigate the combustion process.
A 1-D premixed laminar flame speed reactor was employed to analyze combustion characteristics, considering thermal diffusion and multicomponent diffusion options. The adaptive mesh parameters were set as CURV = 0.5 and GRAD = 0.05, with absolute and relative error criteria of ATOL = 1 × 10−9 and RTOL = 1 × 10−5, respectively. The total number of grid points used was typically 350–400. In this study, we have established that the calculation domain of the CHEMKIN reactor ranges from −2.0 cm upstream to 4.0 cm downstream with respect to the reactor and is sufficient to attain adiabatic equilibrium. Numerical analyses were performed at various fueling conditions based on H2/CH4 ratio (xH2) with or without plasma actuation. Table 1 shows the mole fraction of CH4, and H2 reactants at equivalence ratio of 1.

2.2. Plasma Kinetic Model

A comprehensive literature review was conducted to develop an extended plasma kinetic mechanism for CH4/H2/Air mixture. It consists of 161 species and 1382 plasma and gas-phase reactions, and includes ionization reactions, charged transfer reactions, dissociation reactions, excited species reactions, recombination reactions, relaxation reactions, and three-body recombination reactions. The mechanism also included 38 exciting species and 35 charged species. The relevant reactions were taken from [21,22,23,24]. The collision cross-sectional data were taken from the LXCat data source [13]. Further information can be found in the previously published study [13].

2.3. Combustion Kinetic Model

The NSPD generated kinetic effects (neutral radicals, active particles, excited species) and thermal effects were used to study the effect on flame speed in a CHEMKIN combustion model. The CH4/H2/Air combustion kinetic model was created with an expanded version of the combustion mechanism, incorporating thermodynamics and transport data. The mechanism was updated from GRI-Mech v3.08 with ozone reactions [25] and updated hydrogen combustion mechanism including the excited species O(1D), OH(2+), O2(a¹g) [26]. A sub-model of the excited species OH* and CH* has also been added [27]. Furthermore, the reaction mechanism of ions and excited species of CH4/Air mixture was also considered [28].

3. Validation of Kinetic Models

The plasma kinetic model was validated using an experimental study in [29] by comparing the mole fraction of the decay process of O atoms. The plasma kinetic model was validated using an experimental study in [13]. The model accurately predicts the O atom mole fraction, in good agreement with experimental data.
The combustion kinetic model was validated using experiments by Coppens [30], Hermanns [31], the Konnov mechanism [32], and the San Diego mechanism [33]. The combustion kinetic mechanism was tested with H2 and CH4 fractions equal xH2 = 0.05 and xCH4 = 0.95CH4 at different equivalence ratios. Figure 3 shows the validation results for burning velocities of CH4/H2/Air mixture with 5%, 30%, and 40%. H2 content. The model shows good agreement with experimental data compared to other mechanisms, with slightly lower values at rich burning conditions as seen in [30,31].

4. Results and Discussions

The present analysis was conducted under fixed plasma conditions: EN = 200 Td, repetition frequency equal to 1000 Hz, and electron number density equal to 107 cm−3. The effect of varying H2 contents (xH2 from 0 to 0.2) on active particle production was studied in methane/air. Figure 4 shows the temporal evolution of active particles (H, OH, CH, and CH3) as predicted by ZDPlaskin simulations under fixed plasma actuation conditions, only changing the H2 content in the methane/air mixture. An increase in H2 concentration led to a significant improvement in the mole fraction of active species. The improvement in active particles production was linearly proportional to the rise in H2 content, with the maximum concentration observed at 20% H2. The rapid decomposition of H2+ into H, (E + H2+ => H + H) due to its simple molecular structure and high reactivity and the subsequent reactions with other intermediate species, led to increased concentration of active particles. The maximum mole fraction of H was 0.00704 (Figure 4a), which was almost twice the OH species equal to 0.0038 (Figure 4b). The maximum mole fraction of CH3 was 0.006 (Figure 4c), slightly less than H but two orders higher than the molar fraction of CH (0.000041, Figure 4d).
The H atoms were produced during the decomposition process when electrons reacted with the ions of CH+, CH2+, CH3+, CH4+, and H3O+. The primary reactions contributing to the production of H, CH, and CH3 were E + CH4+ = CH3 + H and E + CH3+ = CH + H + H (reaction rates: 1020 and 1021 cm3 s−1, respectively). The OH radicals were produced through the reaction O(1D) + CH4 = CH3 + OH (reaction rate: 1024 cm3 s−1).
As shown in Figure 5, the mole fraction of active species was significantly improved with an increase in H2 content in the methane/air mixture. The highest mole fraction of O atoms was observed at a 20% H2 content (xH2 = 0.2) with a value of 0.0158 (Figure 5b). This was due to the decomposition of excited O2 species when reacting with H atoms and H2O molecules, which increased in concentration due to the presence of H2 molecules in the methane/air mixture. The dominant reaction path was H + O2(V4) => O + OH (reaction rate: 1023 cm3/s). The O atoms produced began to reduce after 10−4 s, likely due to the short reactive time of O atoms leading to their consumption during recombination and intermediate reactions. Similarly, ozone concentration improved as shown in Figure 5c, with a mole fraction of 0.00729, close to that of H atoms (0.00704) at a 20% H2 content.
Ozone is primarily generated through the reaction of O atoms with molecular oxygen or with excited species of oxygen. The most significant reaction is O + O2 + N2 = O3 + N2, as it has a reaction rate of about 1023 cm3/s. Nitrogen acts as a third body, removing excess energy. Ozone can also improve combustion analysis as it increases flame speed [25]. The temporal evolution of ammonia was also found to improve when nitrogen seed particle was added to methane-blended hydrogen.
The kinetic and thermal effects predicted by ZDPlasKin were introduced into Chemkin to investigate the flame speed and maximum flame temperature. The reactant mole fraction of active particles and excited species predicted by ZDPlasKin were added to Chemkin to account for kinetic effects. This was executed with a 0.5 ms residence time, which is too short to affect the autoignition chemistry and the reactant composition. The flame speed and peak flame temperature were investigated using a pre-mixed laminar flame speed reactor at different methane-blended hydrogen mixture compositions with or without NSPD.
Figure 6a showed that flame speed improved with increasing hydrogen content and plasma excitation. At stoichiometric mixture, adding hydrogen (xH2 = 0.2) to the methane/air mixture resulted in a 14% increase in flame speed (∆sL). A further improvement of 35% was achieved with plasma discharge. At leaner condition (ϕ = 0.6) and same H2 fraction, ∆sL was 16.7% without and 52% with plasma actuation. However, the same flame speed was observed for both cases of xH2 = 0.2 and xH2 = 0.05 with PAC at lean and stoichiometric conditions, similarly in case of xH2 = 0.1 and xH2 = 0 with PAC. It means the same range of flame speed could be reached by varying both hydrogen fraction and plasma discharge.
Figure 6b shows the predicted peak flame temperature Tf with or without plasma for various H2 fractions. The results showed that increasing H2 did not affect Tf without plasma discharges. However, with plasma, Tf was affected by H2 at fixed operating conditions, especially for the rich mixture (Φ > 1). A slightly increase in Tf was found at lean and stoichiometric conditions.
The study found that lean conditions at low flame temperature resulted in significant improvement in flame speed. With 20% H2 and NSPD, flame speed reached 37 cm/s at flame temperature of 2040 K at ϕ = 0.8. Similar results were observed with 0% and 5% H2 and a flame temperature of 2200 K at ϕ = 1. It was observed that the same flame speed can be achieved at lean conditions by reducing Tf, leading to reduced NOx emissions.
Figure 7 compares the improvement in flame speed (%) at lean, stochiometric, and rich conditions with xH2 = 0.2 with or without NSPD. It was observed that the improvement trend was ϕ = 1.4 > ϕ = 0.6 > ϕ = 1. At lean conditions (ϕ = 0.6), adding xH2 = 0.2 improved flame speed by 15%, however, using both xH2 = 0.2 and plasma resulted in a more than 50% improvement. At rich conditions, the largest improvement was seen with plasma due to the increased fuel causing more active particles to be produced during NSPD”.
Literature [26] showed that the molecular excited species oxygen O2(1∆) increased burning velocity by 1% without plasma. The reaction path H2 + O2(1∆) = H + HO2 was found to play a significant role. More than 5% of O2 was converted to O2(1∆) in the presence of electric discharge at ambient pressure [34]. Thus, plasma discharge could produce significant amounts of O2(1∆). Figure 8 analyzed the role of O2(1∆) using hydrogen blends with or without plasma discharge. The results showed no change in O2(1∆) production with hydrogen blends alone at various equivalence ratios. However, with the use of plasma discharge, there was a significant rise in excited species production, especially at higher hydrogen content.
Impact of atomic excited species O(1D) on flame speed was studied using plasma and hydrogen blends (Figure 9). Results showed low O(1D) concentration increased with hydrogen and plasma, but still had minimal effect on combustion. However, it could be increased with the increase in plasma amplitude.
Free radicals such as O, H, and OH are active due to unpaired electrons and short lived in combustion [35]. They initiate chain reactions and branching. Figure 10a–d show mole fraction profiles of O, H, OH, and CH3 using hydrogen blends with/without plasma discharge. Adding hydrogen increased O, H, and OH mole fractions, but decreased CH3 slightly (Figure 10d). Using NSPD in hydrogen blends raised O, H, and OH concentrations and moved the reaction region upstream. CH3 mole fraction was also slightly increased with plasma discharge. OH particles had the highest concentration at 0.009 mole fraction. Main reactions producing O, H, and OH particles are described as follows in Equations (6) and (7).
OH + H2 = H + H2O
H + O2 = O + OH
Figure 11 shows the production rate of Equations (6) and (7) with xH2 = 0 and xH2 = 0.2 with/without NSPD. The rate increased and the peak shifted upstream with hydrogen addition, but with xH2 = 0.2 and plasma, a significant impact was seen.
H2 and O2 mole fractions change with hydrogen blends and NSPD, shown in Figure 12. H2 transforms from intermediate species to initial reactant in methane flames with xH2 ≥ 0.2 and NSPD. H2 starts reacting upstream in xH2 = 0.2, confirmed by [36]. H2 promotes combustion and moves the reaction region towards upstream due to its higher reactivity than CH4.
Figure 13a illustrates the mole fractions of CH4 in different H2 blends with or without the NSPD. The addition of H2 and NSPD leads to a decrease in CH4 mole fraction, possibly due to the high reactivity of H2 and lower CH4 concentration. The oxidation of CH4 greatly increased and its profiles were shifted towards the upstream sides. CH4 was mainly consumed by reactions with active particles O, H, and OH. The dominant CH4 consumption reactions are listed below.
OH + CH4 = CH3 + H2O
H + CH4 = CH3 + H2
O + CH4 = OH + CH3
The rate of production of Equations (8)–(10) using hydrogen contents xH2 = 0 and xH2 = 0.2 with or without NSPD is shown in Figure 13b. CH4 consumption was increased for reaction Equations (8)–(10) and the peak of the reaction region was shifted towards the upstream with the addition of hydrogen contents with or without plasma. However, when combining the H2 blends of xH2 = 0.2 with NSPD, a noticeable impact was observed. It was because hydrogen is more reactive, which promoted methane combustion. The concentration of active particles O, H, and OH were increased when methane was blended with hydrogen, mainly due to the chemical effects. Moreover, the NSPD further improved the combustion process due to the thermal (moderate gas heating) and kinetic effects (excitation, ionization and decomposition of fuel and air molecules occurred, which resulted in the production of intermediate fuel fragments and active particles).
Finally, the lean flammability limit is discussed as the minimum equivalence ratio for flame propagation. Figure 14 shows the lean flammability limit using hydrogen contents XH2 = 0 and XH2 = 0.2 with or without NSPD. The flammability limit remained at ϕ = 0.6 without H2 and plasma but improved to ϕ = 0.5 with the addition of XH2 = 0.2. Plasma discharge had a significant impact on the flammability limits, with ϕ = 0.45 at flame temperature about 1500 K.
Combining XH2 = 0.2 and NSPD increased the flammability limit to ϕ = 0.35 at 1350 K, allowing self-sustained combustion at lower flame temperatures and reduced NOx emissions. The improved flammability limits reduce fuel consumption due to the enhanced reactivity and chemical effects of H2 and thermal and kinetic effects of NSPD.

5. Conclusions

This paper investigated the impact of NSPD on enhancing the flame propagation of CH4/H2/air mixture under ambient temperature and pressure. A reduced electric field experimentally estimated was used for numerical investigation. An extended version of the plasma and combustion kinetic mechanism was applied and validated using available experimental and numerical data. ZDPlasKin was used to predict the temporal evolution of active particles and the results were integrated into CHEMKIN to enhance the flame speed. The numerical study was carried out with varying H2 contents from 0 to 20% in methane/air with or without plasma actuation. It was noticed that with the enrichment of H2 concentration in the methane/air mixture at fixed plasma, the mole fraction of active species was significantly improved. However, the improvements in the production of active particles were linearly increased with the increase in H2 contents. The highest improvement in flame propagation was observed at 20% H2/Plasma reaching 35%.
Flame speed improvement was significantly higher at lean conditions and low flame temperatures. For instance, at an equivalence ratio of 0.8, 20% H2/Plasma resulted in a flame speed of 37 cm/s at a flame temperature of around 2040 K. This same flame speed was also observed in the case of 0% and 5% H2 with a flame temperature close to 2200 K, meaning that high flame speed can be achieved at lean conditions and low flame temperatures, reducing NOx emissions. Figure 7 shows the comparison of flame speed improvement at lean, stoichiometric, and rich conditions with xH2 = 0.2 with or without NSPD. The improvement in flame speed was higher at lean conditions (equivalence ratio of 0.6) with the addition of xH2 = 0.2, reaching 15%. Combining xH2 = 0.2 with plasma discharge significantly increased flame speed by more than 50%. Furthermore, the combination of H2 blend (xH2 = 0.2) and NSPD improved the flammability limit to equivalence ratio 0.35 at a flame temperature of 1350 K, allowing for reduced fuel consumption.

Author Contributions

Conceptualization, M.G.D.G.; Methodology, M.G.D.G. and G.M.; Software, G.M.; Validation, G.M.; Formal analysis, G.M.; Investigation, G.M. and S.B.; Data curation, G.M., G.C., Z.A.S. and S.B.; Writing—original draft preparation, G.M.; Writing—review and editing, M.G.D.G.; Supervision, M.G.D.G. and A.F.; Project administration, M.G.D.G. and A.F.; Funding acquisition, G.M. All authors have read and agreed to the published version of the manuscript.

Funding

The work was supported and funded by the PON R&I 2014–2020 Asse I “Investimenti in Capitale Umano” Azione I.1 “Dottorati Innovativi con caratterizzazione industriale”—Corso di Dottorato in “Ingegneria dei Sistemi Complessi” XXXV ciclo—Università degli Studi del Salento”—Borsa Codice: DOT1312193 no. 3. This project is also received funding from the Clean Sky 2 Joint Undertaking (JU) under the grant agreement no. 831881 (CHAiRLIFT). The JU received support from the European Union’s Horizon 2020 research and innovation program and the Clean Sky 2 JU members other than the Union. Aerospace 10 00224 i001

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Ju, Y.; Sun, W. Plasma Assisted Combustion: Dynamics and Chemistry. Prog. Energy Combust. Sci. 2015, 48, 21–83. [Google Scholar] [CrossRef]
  2. Mehdi, G.; Bonuso, S.; De Giorgi, M.G. Plasma Assisted Re-Ignition of Aeroengines under High Altitude Conditions. Aerospace 2022, 9, 66. [Google Scholar] [CrossRef]
  3. Jackson, G.S.; Sai, R.; Plaia, J.M.; Boggs, C.M.; Kiger, K.T. Influence of H2 on the response of lean premixed CH4 flames to high strained flows. Combust. Flame 2003, 132, 503–511. [Google Scholar] [CrossRef]
  4. Hawkes, E.R.; Chen, J.H. Direct Numerical Simulation of Hydrogen-Enriched Lean Premixed Methane— Air Flames. Combust. Flame 2004, 138, 242–258. [Google Scholar] [CrossRef]
  5. Halter, F.; Chauveau, C.; Djebaili-Chaumeix, N.; Gokalp, I. Characterization of the effects of pressure and hydrogen concentration on laminar burning velocities of methane–hydrogen–air mixtures. Proc. Combust. Inst. 2005, 30, 201–208. [Google Scholar] [CrossRef]
  6. Mandilas, C.; Ormsby, M.P.; Sheppard, C.G.W.; Woolley, R. Effects of hydrogen addition on laminar and turbulent premixed methane and iso-octane–air flames. Proc. Combust. Inst. 2007, 31, 1443–1450. [Google Scholar] [CrossRef]
  7. De Giorgi, M.G.; Bonuso, S.; Mehdi, G.; Shamma, M.; Harth, S.R.; Zarzalis, N.; Trimis, D. Enhancement of Blowout Limits in Lifted Swirled Flames in Methane-Air Combustor by the Use of Sinusoidally Driven Plasma Discharges. In Proceedings of the Active Flow and Combustion Control 2021: Papers Contributed to the Conference “Active Flow and Combustion Control 2021”, Berlin, Germany, 28–29 September 2021; King, R., Peitsch, D., Eds.; Springer: Cham, Switzerland, 2022; pp. 66–82. [Google Scholar] [CrossRef]
  8. Meng, Y.; Gu, H.; Chen, F. Influence of Plasma on the Combustion Mode in a Scramjet. Aerospace 2022, 9, 73. [Google Scholar] [CrossRef]
  9. De Giorgi, M.G.; Mehdi, G.; Bonuso, S.; Shamma, M.; Harth, S.; Trimis, D.; Zarzalis, N. Characterization of Flame Behavior and Blowout Limits at Different Air Preheating Temperatures in Plasma Assisted Stabilized Combustor. In Proceedings of the Turbo Expo: Power for Land, Sea, and Air, Rotterdam, The Netherlands, 13–17 June 2022; American Society of Mechanical Engineers: New York, NY, USA, 2022; 86007, p. V03BT04A048. [Google Scholar] [CrossRef]
  10. Mehdi, G.; Bonuso, S.; De Giorgi, M.G. Development of plasma actuators for re-ignition of aeroengine under high altitude conditions. In IOP Conference Series: Materials Science and Engineering; IOP Publishing: Bristol, UK, 2022; Volume 1226, p. 012034. [Google Scholar]
  11. Ju, Y.; Lefkowitz, J.K.; Reuter, C.B.; Won, S.H.; Yang, X.; Yang, S.; Sun, W.; Jiang, Z.; Chen, Q. Plasma Assisted Low Temperature Combustion. Plasma Chem. Plasma Process. 2016, 36, 85–105. [Google Scholar] [CrossRef] [Green Version]
  12. Mehdi, G.; Bonuso, S.; De Giorgi, M.G. Effects of Nanosecond Repetitively Pulsed Discharges Timing for Aeroengines Ignition at Low Temperature Conditions by Needle-Ring Plasma Actuator. Energies 2021, 14, 5814. [Google Scholar] [CrossRef]
  13. Mehdi, G.; Fontanarosa, D.; Bonuso, S.; De Giorgi, M.G. Ignition thresholds and flame propagation of methane-air mixture: Detailed kinetic study coupled with electrical measurements of the nanosecond repetitively pulsed plasma discharges. J. Phys. D Appl. Phys. 2022, 55, 315202. [Google Scholar] [CrossRef]
  14. Fontanarosa, D.; Mehdi, G.; De Giorgi, M.G.; Ficarella, A. Assessment of the impact of nanosecond plasma discharge on the combustion of methane air flames. E3S Web Conf. 2020, 197, 10001. [Google Scholar] [CrossRef]
  15. Mehdi, G.; De Giorgi, M.G.; Fontanarosa, D.; Bonuso, S.; Ficarella, A. Ozone Production With Plasma Discharge: Comparisons Between Activated Air and Activated Fuel/Air Mixture. In Proceedings of the ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition, Virtual, 7–11 June 2021; American Society of Mechanical Engineers: New York, NY, USA, 2021; Volume 3B, p. V03BT04A036. [Google Scholar] [CrossRef]
  16. Starikovskiy, S.M. Topical review: Plasma-assisted ignition and combustion. J. Phys. D Appl. Phys. 2006, 39, 265–299. [Google Scholar] [CrossRef]
  17. Ruma, M.; Ahasan, H.; Ranipet, H.B. A Survey of Non-thermal plasma and their generation methods. Int. J. Renew. Energy Environ. Eng. 2016, 4, 6–12. [Google Scholar]
  18. Pancheshnyi, S.; Eismann, B.; Hagelaar, G.J.M.; Pitchford, L.C. ZDPlaskin Zero-Dimensional Plasma Kinetic Solver. 2008. Available online: http://www.zdplaskin.laplace.univ-tlse.fr/ (accessed on 8 September 2021).
  19. Lutz, A.E.; Kee, R.J.; Miller, J.A. SENKIN: A FOR- TRAN. In Program for Predicting Homogeneous Gas Phase Chemical Kinetics with Sensitivity Analysis; Report No. SAND87-8248; Sandia National Laboratories: Livermore, CA, USA, 1988. [Google Scholar]
  20. Aleksandrov, N.L.; Kindysheva, S.V.; Kukaev, E.N.; Starikovsjaya, S.M.; Starikovskii, A.Y. Simulation of the Ignition of a Methane-Air Mixture by a High-Voltage Nanosecond Discharge. Plasma Phys. Rep. 2009, 35, 867–882. [Google Scholar] [CrossRef]
  21. Capitelli, M.; Ferreira, C.M.; Gordiets, B.F.; Osipov, A.I. Plasma Kinetics in Atmospheric Gases; Springer: Berlin/Heidelberg, Germany, 2000. [Google Scholar]
  22. Flitti, A.; Pancheshnyi, S. Gas heating in fast pulsed discharges in N2–O2 mixtures. Eur. Phys. J. Appl. Phys. 2009, 45, 21001. [Google Scholar] [CrossRef] [Green Version]
  23. Mao, X.; Rousso, A.; Chen, Q.; Ju, Y. Numerical modeling of ignition enhancement of CH4 /O2 /He mixtures using a hybrid repetitive nanosecond and DC discharge. Proc. Combust. Inst. 2019, 37, 5545–5552. [Google Scholar] [CrossRef]
  24. Mao, X.; Chen, Q.; Guo, C. Methane pyrolysis with N2/Ar/He diluents in a repetitively pulsed nanosecond discharge: Kinetics development for plasma assisted combustion and fuel reforming. Energy Convers. Manag. 2019, 200, 112018. [Google Scholar] [CrossRef]
  25. Halter, F.; Higelin, P.; Dagaut, P. Experimental and detailed kinetic modelling study of the effect of ozone on the combustion of methane, Energy Fuels, 2011, 25 2909–16. Energy Fuels 2011, 25, 2909–2916. [Google Scholar] [CrossRef]
  26. Konnov, A.A. On the role of excited species in hydrogen combustion. Combust. Flame 2015, 162, 3755–3772. [Google Scholar] [CrossRef]
  27. Walsh, K.T. Quantitative Characterizations of Coflow Laminar Diffusion Flames in a Normal Gravity and Microgravity Environment. Ph.D. Thesis, Yale University, New Haven, CT, USA, 2000. [Google Scholar]
  28. Cámara, C.F.L.; Éplénier, G.; Tinajero, J.; Dunn-Rankin, D. Numerical Simulation of Methane/Air Flames Including Ions and Excited Species. Combust. Inst. Provo UT USA 2015. [Google Scholar]
  29. Uddi, M.; Jiang, N.; Mintusov, E.; Adamovich, I.V.; Lempert, W.R. Atomic oxy- gen measurements in air and air / fuel nano-second pulse discharges by two photon laser induced fluorescence. Proc. Combust. Inst. 2009, 32, 929–936. [Google Scholar] [CrossRef]
  30. Coppens, F.H.V.; De Ruyck, J.; Konnov, A.A. The effects of composition on burning velocity and nitric oxide formation in laminar premixed flames of CH4 + H2 + O2 + N2. Combust. Flame 2007, 149, 409–417. [Google Scholar] [CrossRef]
  31. Hermanns, R.T.E.; Kortendijk, J.A.; Bastiaans, R.J.M.; De Goey, L.P.H. Laminar burning velocities of methane-hydrogen-air mixtures. Submitt. Combust. Flame 2007. [Google Scholar] [CrossRef]
  32. Konnov, A.A. Detailed Reaction Mechanism for Small Hydrocarbons Combustion. 2022. Available online: http://homepages.vub.ac.be/~akonnov/ (accessed on 8 September 2021).
  33. Williams, F. San Diego Mechanism. 2010. Available online: http://maeweb.ucsd.edu/combustion/cermech/index.html (accessed on 8 September 2021).
  34. Kozlov, V.E.; Starik, A.M.; Titova, N.S. Enhancement of combustion of a hydrogen-air mixture by excitation of O2 molecules to the a 1Δgstate. Combust. Explos. Shock Waves 2008, 44, 371–379. [Google Scholar] [CrossRef]
  35. Law, C.K. Combustion Physics; Cambridge University Press: New York, NY, USA, 2006. [Google Scholar]
  36. Ying, Y.; Liu, D. Detailed influences of chemical effects of hydrogen as fuel additive on methane flame. Int. J. Hydrogen Energy 2015, 40, 3777–3788. [Google Scholar] [CrossRef]
Figure 1. Flowchart for numerical analysis.
Figure 1. Flowchart for numerical analysis.
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Figure 2. Experimental EN value used for numerical analysis [13].
Figure 2. Experimental EN value used for numerical analysis [13].
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Figure 3. Validation: predicted values of burning velocities of CH4/H2/Air mixture with a H2 content of (a) 5%, (b) 30% and (c) 40%.
Figure 3. Validation: predicted values of burning velocities of CH4/H2/Air mixture with a H2 content of (a) 5%, (b) 30% and (c) 40%.
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Figure 4. Temporal evolution of (a) H, (b) OH, (c) CH, (d) CH3 concentrations at different contents of H2 in methane/air mixture using fixed plasma actuation conditions.
Figure 4. Temporal evolution of (a) H, (b) OH, (c) CH, (d) CH3 concentrations at different contents of H2 in methane/air mixture using fixed plasma actuation conditions.
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Figure 5. Temporal evolution of (a) CH2, (b) O, (c) O3, (d) NH3 concentrations at different contents of H2 in methane/air mixture using fixed plasma actuation conditions.
Figure 5. Temporal evolution of (a) CH2, (b) O, (c) O3, (d) NH3 concentrations at different contents of H2 in methane/air mixture using fixed plasma actuation conditions.
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Figure 6. Comparison of (a) flame speed and (b) flame temperature at various equivalence ratios using different H2 contents with or without NSPD.
Figure 6. Comparison of (a) flame speed and (b) flame temperature at various equivalence ratios using different H2 contents with or without NSPD.
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Figure 7. Comparative behavior of flame speed improvements (%) at lean, stoichiometric, and rich conditions.
Figure 7. Comparative behavior of flame speed improvements (%) at lean, stoichiometric, and rich conditions.
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Figure 8. Comparison of molecular excited species O2(1∆) at various equivalence ratios using different H2 contents with or without NSPD.
Figure 8. Comparison of molecular excited species O2(1∆) at various equivalence ratios using different H2 contents with or without NSPD.
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Figure 9. Comparison of atomic excited species O(1D) at various equivalence ratios using different H2 contents with NSPD.
Figure 9. Comparison of atomic excited species O(1D) at various equivalence ratios using different H2 contents with NSPD.
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Figure 10. Mole fraction profiles of (a) H, (b) O, (c) OH, and (d) CH3 with different blends of hydrogen without or with NSPD.
Figure 10. Mole fraction profiles of (a) H, (b) O, (c) OH, and (d) CH3 with different blends of hydrogen without or with NSPD.
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Figure 11. Rate of production of O, H, and OH with different blends of hydrogen without or with NSPD.
Figure 11. Rate of production of O, H, and OH with different blends of hydrogen without or with NSPD.
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Figure 12. Mole fraction profiles of H2 and O2 with different blends of hydrogen without or with NSPD.
Figure 12. Mole fraction profiles of H2 and O2 with different blends of hydrogen without or with NSPD.
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Figure 13. (a) Mole fraction profile of CH4 (b) Rate of production of CH4 with different blends of hydrogen without or with NSPD.
Figure 13. (a) Mole fraction profile of CH4 (b) Rate of production of CH4 with different blends of hydrogen without or with NSPD.
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Figure 14. Flammability limits with different blends of hydrogen without or with NSPD.
Figure 14. Flammability limits with different blends of hydrogen without or with NSPD.
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Table 1. Reactants mole fraction of CH4/H2/Air flames at plasma on and off conditions.
Table 1. Reactants mole fraction of CH4/H2/Air flames at plasma on and off conditions.
Case No.H2 (%)CH4H2O2N2Plasma (ON/OFF)
100.0950/0.19000.7149OFF
250.09350.00490.18940.7122OFF
3100.09170.01010.18850.7094OFF
4200.08790.02190.18690.7031OFF
500.0950/0.19000.7149ON
650.09350.00490.18940.7122ON
7100.09170.01010.18850.7094ON
8200.08790.02190.18690.7031ON
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Mehdi, G.; De Giorgi, M.G.; Bonuso, S.; Shah, Z.A.; Cinieri, G.; Ficarella, A. Comparative Analysis of Flame Propagation and Flammability Limits of CH4/H2/Air Mixture with or without Nanosecond Plasma Discharges. Aerospace 2023, 10, 224. https://doi.org/10.3390/aerospace10030224

AMA Style

Mehdi G, De Giorgi MG, Bonuso S, Shah ZA, Cinieri G, Ficarella A. Comparative Analysis of Flame Propagation and Flammability Limits of CH4/H2/Air Mixture with or without Nanosecond Plasma Discharges. Aerospace. 2023; 10(3):224. https://doi.org/10.3390/aerospace10030224

Chicago/Turabian Style

Mehdi, Ghazanfar, Maria Grazia De Giorgi, Sara Bonuso, Zubair Ali Shah, Giacomo Cinieri, and Antonio Ficarella. 2023. "Comparative Analysis of Flame Propagation and Flammability Limits of CH4/H2/Air Mixture with or without Nanosecond Plasma Discharges" Aerospace 10, no. 3: 224. https://doi.org/10.3390/aerospace10030224

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