N2 CARS thermometry and O2 LIF concentration measurements in a flame under electrically induced microbuoyancy

Microgravity combustion is fundamentally characterized by the absence of buoyancy driven flows. To facilitate a large range of diagnostics on microgravity flames, it is useful to create an equivalent microbuoyant condition in an earth-based laboratory. This experiment simulates microbuoyancy using electric fields to balance local convection in a region of the flame. Previous studies used N₂ coherent anti-Stokes Raman spectroscopy (CARS) temperature measurements to show that a region exists in which the temperature profile corresponds to that of a spherically symmetric diffusion profile, as would be expected in a true microgravity environment. The current study utilizes CARS thermometry and laser induced fluorescence (LIF) to examine the temperature and O₂ concentration profiles in a region below the flame. The results show that the electrically balanced flame apparatus produces a spherically symmetric wedge of microbuoyant flame extending 10° from the vertical axis of the capillary flame arrangement; thereby quantifying the extent of the microbuoyant region.     

Dual-pump CARS temperature and major species concentration measurements in counter-flow methane flames using narrowband pump and broadband Stokes lasers

Dual-pump coherent anti-Stokes Raman scattering (CARS) is used to measure temperature and species profiles in representative non-premixed and partially-premixed CH₄/O₂/N₂ flames. A new laser system has been developed to generate a tunable single-frequency beam for the second pump beam in the dual-pump N₂-CO₂ CARS process. The second harmonic output (∼532 nm) from an injection-seeded Nd:YAG laser is used as one of the narrowband pump beams. The second single-longitudinal-mode pump beam centered near 561 nm is generated using an injection-seeded optical parametric oscillator, consisting of two non-linear β-BBO crystals, pumped using the third harmonic output (∼355 nm) of the same Nd:YAG laser. A broadband dye laser (BBDL), pumped using the second harmonic output of an unseeded Nd:YAG laser, is employed to produce the Stokes beam centered near 607 nm with full-width-at-half-maximum of ∼250 cm⁻¹. The three beams are focused between two opposing nozzles of a counter-flow burner facility to measure temperature and major species concentrations in a variety of CH₄/O₂/N₂ non-premixed and partially-premixed flames stabilized at a global strain rate of 20 s⁻¹ at atmospheric-pressure. For the non-premixed flames, excellent agreement is observed between the measured profiles of temperature and CO₂/N₂ concentration ratios with those calculated using an opposed-flow flame code with detailed chemistry and molecular transport submodels. For partially-premixed flames, with the rich side premixing level beyond the stable premixed flame limit, the calculations overestimate the distance between the premixed and the non-premixed flamefronts. Consequently, the calculated temperatures near the rich, premixed flame are higher than those measured. Accurate prediction of the distance between the premixed and the non-premixed flames provides an interesting challenge for future computations.     

Temperature profile measurements in the near-substrate region of low-pressure diamond-forming flames

Coherent anti-Stokes Raman scattering (CARS) spectroscopy of diatomic hydrogen was used to measure gas-phase temperature profiles in low-pressure, stagnation-flow, diamond-forming flames. The objectives of the study were to measure detailed temperature profiles for comparison with a numerical flame model and to investigate the presence and magnitude of the temperature jump at the deposition substrate surface. At distances of several hundred microns or greater from the deposition substrate, the measured temperatures were in excellent agreement with the results of a numerical flame model incorporating elementary chemical kinetic and multi-species transport models. The estimated hydrogen CARS temperature accuracy was ±4% near the deposition substrate and was ±5% away from the substrate. The estimated spatial resolution of the measurements was 30 μm normal to the surface, and the gradient in temperature was resolved fully up to approximately 25 μm from the surface. The excellent spatial resolution for the near-surface measurements allowed the investigation of the presence and the magnitude of the discontinuity between the gas and surface temperature at the deposition substrate, a phenomenon known as the temperature jump. Temperature jumps of approximately 100 K were observed in these rich, premixed oxy-acetylene flames ranging from 30 Torr. to 125 Torr. The influence of gas flow rate and pressure on the temperature jump was investigated. The observed temperature jumps are consistent with an accommodation co-efficient in the range of 0.1 to 0.2 for the exchange of energy between the diamond-forming flame gases and the molybdenum surface or the diamond film on the deposition substrate. In these low-pressure flames, the ability to fully resolve the near-substrate temperature profiles will be extremely useful for the validation and improvement of surface chemistry models.     

Tubular premixed and diffusion flames: Effect of stretch and curvature

Tubular flames are ideal for the study of stretch and curvature effects on flame structure, extinction, and instabilities. Tubular flames have uniform stretch and curvature and each parameter can be varied independently. Curvature strengthens or weakens preferential diffusion effects on the tubular flame and the strengthening or weakening is proportional to the ratio of the flame thickness to the flame radius. Premixed flames can be studied in the standard tubular burner where a single premixed gas stream flows radially inward to the cylindrical flame surface and products exit as opposed jets. Premixed, diffusion and partially premixed flames can be studied in the opposed tubular flame where opposed radial flows meet at a cylindrical stagnation surface and products exit as opposed jets. The tubular flame flow configurations can be mathematically reduced to a two-point boundary value solution along the single radial coordinate. Non-intrusive measurements of temperature and major species concentrations have been made with laser-induced Raman scattering in an optically accessible tubular burner for both premixed and diffusion flames. The laser measurements of the flame structure are in good agreement with numerical simulations of the tubular flame. Due to the strong enhancement of preferential diffusion effects in tubular flames, the theory-data comparison can be very sensitive to the molecular transport model and the chemical kinetic mechanism. The strengthening or weakening of the tubular flame with curvature can increase or decrease the extinction strain rate of tubular flames. For lean H₂-air mixtures, the tubular flame can have an extinction strain rate many times higher than the corresponding opposed jet flame. More complex cellular tubular flames with highly curved flame cells surrounded by local extinction can be formed under both premixed and non-premixed conditions. In the hydrogen fueled premixed tubular flames, thermal-diffusive flame instabilities result in the formation of a uniform symmetric petal flames far from extinction. In opposed-flow tubular diffusion flames, thermal-diffusive flame instabilities result in cellular flames very close to extinction. Both of these flames are candidates for further study of flame curvature and extinction.     

Temperature and concentration profiles in hydrogennitrous oxide flames

Spontaneous Raman spectroscopy has been used to measure temperature and NO, O₂, and N₂ concentration profiles in lean to stoichiometric premixed laminar hydrogennitrous oxide flames. Relative concentration profiles for OH were also obtained for these flames by use of laser induced fluorescence. The present NO concentration results for the stoichiometric flame agree with previous NO measurements obtained by a different optical technique. Profiling these species for various equivalence ratios provides a further test for flame modelers.     

On the similitude between lifted and burner-stabilized triple flames: a numerical and experimental investigation

We have investigated lifted triple flames and addressed issues related to flame stabilization. The stabilization of nonpremixed flames has been argued to result due to the existence of a premixing zone of sufficient reactivity, which causes propagating premixed reaction zones to anchor a nonpremixed zone. We first validate our simulations with detailed measurements in more tractable methane–air burner-stabilized flames. Thereafter, we simulate lifted flames without significantly modifying the boundary conditions used for investigating the burner-stabilized flames. The similarities and differences between the structures of lifted and burner-stabilized flames are elucidated, and the role of the laminar flame speed in the stabilization of lifted triple flames is characterized. The reaction zone topography in the flame is as follows. The flame consists of an outer lean premixed reaction zone, an inner rich premixed reaction zone, and a nonpremixed reaction zone where partially oxidized fuel and oxidizer (from the rich and lean premixed reaction zones, respectively) mix in stoichiometric proportion and thereafter burn. The region with the highest temperatures lies between the inner premixed and the central nonpremixed reaction zone. The heat released in the reaction zones is transported both upstream (by diffusion) and downstream to other portions of the flame. Measured and simulated species concentration profiles of reactant (O₂, CH₄) consumption, intermediate (CO, H₂) formation followed by intermediate consumption and product (CO₂, H₂O) formation are presented. A lifted flame is simulated by conceptualizing a splitter wall of infinitesimal thickness. The flame liftoff increases the height of the inner premixed reaction zone due to the modification of the upstream flow field. However, both the lifted and burner-stabilized flames exhibit remarkable similarity with respect to the shapes and separation distances regarding the three reaction zones. The heat-release distribution and the scalar profiles are also virtually identical for the lifted and burner-stabilized flames in mixture fraction space and attest to the similitude between the burner-stabilized and lifted flames. In the lifted flame, the velocity field diverges upstream of the flame, causing the velocity to reach a minimum value at the triple point. The streamwise velocity at the triple point is ≈0.45 m s⁻¹ (in accord with the propagation speed for stoichiometric methane–air flame), whereas the velocity upstream of the triple point equals 0.7 m s⁻¹, which is in excess of the unstretched flame propagation speed. This is in agreement with measurements reported by other investigators. In future work we will address the behavior of this velocity as the equivalence ratio, the inlet velocity profile, and inlet mixture fraction are changed.     

Radiation intensity imaging measurements of methane and dimethyl ether turbulent nonpremixed and partially premixed jet flames

Quantitative time-dependent images of the infrared radiation intensity from methane and dimethyl ether (DME) turbulent nonpremixed and partially premixed jet flames are measured and discussed in this work. The fuel compositions (CH₄/H₂/N₂, C₂H₆O/H₂/N₂, CH₄/air, and C₂H₆O/air) and Reynolds numbers (15,200–46,250) for the flames were selected following the guidelines of the International Workshop on Measurement and Computation of Turbulent Nonpremixed Flames (TNF Workshop). The images of the radiation intensity are acquired using a calibrated high speed infrared camera and three band-pass filters. The band-pass filters enable measurements of radiation from water vapor and carbon dioxide over the entire flame length and beyond. The images reveal localized regions of high and low intensity characteristic of turbulent flames. The peak mean radiation intensity is approximately 15% larger for the DME nonpremixed flames and 30% larger for the DME partially premixed flames in comparison to the corresponding methane flames. The trends are explained by a combination of higher temperatures and longer stoichiometric flame lengths for the DME flames. The longer flame lengths are attributed to the higher density of the DME fuel mixtures based on existing flame length scaling relationships. The longer flame lengths result in larger volumes of high temperature gas and correspondingly higher path-integrated radiation intensities near and downstream of the stoichiometric flame length. The radiation intensity measurements acquired with the infrared camera agree with existing spectroscopy measurements demonstrating the quantitative nature of the present imaging technique. The images provide new benchmark data of turbulent nonpremixed and partially premixed jet flames. The images can be compared with results of large eddy simulations rendered in the form of quantitative images of the infrared radiation intensity. Such comparisons are expected to support the evaluation of models used in turbulent combustion and radiation simulations.     

A mechanistic study of Soret diffusion in hydrogen–air flames

The separate and combined effects of Soret diffusion of the hydrogen molecule (H₂) and radical (H) on the structure and propagation speed of the freely-propagating planar premixed flames, and the strain-induced extinction response of premixed and nonpremixed counterflow flames, were computationally studied for hydrogen–air mixtures using a detailed reaction mechanism and transport properties. Results show that, except for the conservative freely-propagating planar flame, Soret diffusion of H₂ increases the fuel concentration entering the flame structure and as such modifies the mixture stoichiometry and flame temperature, which could lead to substantial increase (decrease) of the flame speed for the lean (rich) mixtures respectively. On the other hand, Soret diffusion of H actively modifies its concentration and distribution in the reaction zone, which in turn affects the individual reaction rates. In particular, the reaction rates of the symmetric, twin, counterflow premixed flames, especially at near-extinction states, can be increased for lean flames but decreased for rich flames, whose active reaction regions are respectively located at, and away from, the stagnation surface. However, such a difference is eliminated for the single counterflow flame stabilized by an opposing cold nitrogen stream, as the active reaction zone up to the state of extinction is always located away from the stagnation surface. Finally, the reaction rate is increased in general for diffusion flames because the bell-shaped temperature distribution localizes the H concentration to the reaction region which has the maximum temperature.     

Stability characteristics of lifted turbulent partially premixed jet flames

The stability characteristics of partially premixed turbulent lifted methane flames have been investigated and discussed in the present work. Mixture fraction and reaction zone behavior have been measured using a combined 2-D technique of simultaneous Rayleigh scattering, Laser Induced Predissociation Fluorescence (LIPF) of OH and Laser Induced Fluorescence (LIF) of C₂H_x. The stability characteristics and simultaneous mixture fraction-LIPF-LIF measurements in three lifted flames with originally partially premixed jets at different mean equivalence ratio and Reynolds number are presented and discussed in this paper. Higher stability of partially premixed flames as compared to non-premixed flames has been observed. Lifted, attached, blow-out and blow-off regimes have been addressed and discussed in this work. The data show that the mixture fraction field on approaching the stabilization region is uniquely characterized by a certain level of mean and rms fluctuations. This suggests that the stabilization mechanism is likely to be controlled by premixed flame propagation at the stabilization region. Triple flame structure has been detected in the present flames, which is likely to be the appropriate model at the stabilization point.     

A study on flame structure and extinction in downstream interaction between lean premixed CH4-air and (50% H2 + 50% CO) syngas-air flames

Downstream interactions between lean premixed flames with mutually different fuels of (50% H₂ + 50% CO) and CH₄ are numerically investigated particularly on and near lean extinction limits in order to provide fundamental database for the design of cofiring burners with hydrocarbon and syngas under a retrofit concept. In the current study the anomalous combination of lean premixed flames is provided such that even a weaker CH₄-air flame temperature is higher than a stronger syngas-air flame temperature, and, based on a deficient reactant concept, the effective Lewis numbers Le_eff ≈ 1 for lean premixed (50% H₂ + 50% CO)-air mixture and Le_D < 1 for CH₄-air mixture. It is found that the interaction characteristics between lean premixed (50% H₂ + 50% CO)-air and CH₄-air flames are quite different from those between the same hydrocarbon flames. The lean extinction boundaries are of slanted shape, thereby indicating strong interactions. The upper extinction boundaries have negative flame speeds while the lower extinction boundaries have both negative and positive flame speeds. The results also show that the flame interaction characteristics do not follow the general tendency of Lewis number, which has been well described in interactions between the same hydrocarbon flames, but have the strong dependency of direct interaction factors such as flame temperature, the distance between two flames, and radical-sharing. Importance of chain carrier radicals such as H is also addressed in the downstream interactions between lean premixed (50% H₂ + 50% CO)-air and CH₄-air flames.     

Effects of the external turbulence on centrally-ignited spherical unstable Ch4/H2/air flames in the constant-volume combustion bomb

In the present study, we conducted experiments to investigate the effects of external turbulence on the development of spherical H₂/CH₄/air unstable flames developments at two different equivalence ratios associated with different turbulent intensities using a spherical constant-volume turbulent combustion bomb and high speed schlieren photography technology. Flame front morphology and acceleration process were recorded and different effects of weak external turbulent flow field and intrinsic flame instability on the unstable flame propagation were compared. Results showed the external turbulence has a great influence on the unstable flame propagation under rich fuel conditions. For fuel-lean premixed flames, however, the effects of external turbulence on the morphology of the cellular structure on the flame front was not that obvious. Critical radius decreased firstly and then kept almost unchanged with the augment of the turbulence intensity. This indicated the dominating inhibiting effect of flame stretch on the turbulent premixed flame at the initial stage of the flame front development. Beyond the critical radius, the acceleration exponent was found increasing with the enhancement of initial turbulence intensity for fuel-lean premixed flames. For fuel-rich conditions, however, the initial turbulence intensity had little effect on acceleration exponent. In order to evaluate the important impact of the intrinsic flame instability and external turbulent flow field for spherical propagating premixed flames, intrinsic flame instability scale and average diameter of vortex tube were calculated. Intrinsic flame instability scale decreased greatly and then stayed unchanged with the propagation of the flame front. The comparison between intrinsic flame instability scale and average diameter of vortex tube demonstrated that the external turbulent flow filed will be more important for the evolution of wrinkle structure in the final stage of the flame propagation, when the turbulence intensity was more than 0.404 m/s.     

Effects of CO addition on the characteristics of laminar premixed CH4/air opposed-jet flames

The effects of CO addition on the characteristics of premixed CH₄/air opposed-jet flames are investigated experimentally and numerically. Experimental measurements and numerical simulations of the flame front position, temperature, and velocity are performed in stoichiometric CH₄/CO/air opposed-jet flames with various CO contents in the fuel. Thermocouple is used for the determination of flame temperature, velocity measurement is made using particle image velocimetry (PIV), and the flame front position is measured by direct photograph as well as with laser-induced predissociative fluorescence (LIPF) of OH imaging techniques. The laminar burning velocity is calculated using the PREMIX code of Chemkin collection 3.5. The flame structures of the premixed stoichiometric CH₄/CO/air opposed-jet flames are simulated using the OPPDIF package with GRI-Mech 3.0 chemical kinetic mechanisms and detailed transport properties. The measured flame front position, temperature, and velocity of the stoichiometric CH₄/CO/air flames are closely predicted by the numerical calculations. Detailed analysis of the calculated chemical kinetic structures reveals that as the CO content in the fuel is increased from 0% to 80%, CO oxidation (R99) increases significantly and contributes to a significant level of heat-release rate. It is also shown that the laminar burning velocity reaches a maximum value (57.5 cm/s) at the condition of 80% of CO in the fuel. Based on the results of sensitivity analysis, the chemistry of CO consumption shifts to the dry oxidation kinetics when CO content is further increased over 80%. Comparison between the results of computed laminar burning velocity, flame temperature, CO consumption rate, and sensitivity analysis reveals that the effect of CO addition on the laminar burning velocity of the stoichiometric CH₄/CO/air flames is due mostly to the transition of the dominant chemical kinetic steps.     

Effects of preferential transport in turbulent bluff-body-stabilized lean premixed CH4/air flames

Preferential species diffusion is known to have important effects on local flame structure in turbulent premixed flames, and differential diffusion of heat and mass can have significant effects on both local flame structure and global flame parameters, such as turbulent flame speed. However, models for turbulent premixed combustion normally assume that atomic mass fractions are conserved from reactants to fully burnt products. Experiments reported here indicate that this basic assumption may be incorrect for an important class of turbulent flames. Measurements of major species and temperature in the near field of turbulent, bluff-body stabilized, lean premixed methane–air flames (Le = 0.98) reveal significant departures from expected conditional mean compositional structure in the combustion products as well as within the flame. Net increases exceeding 10% in the equivalence ratio and the carbon-to-hydrogen atom ratio are observed across the turbulent flame brush. Corresponding measurements across an unstrained laminar flame at similar equivalence ratio are in close agreement with calculations performed using Chemkin with the GRI 3.0 mechanism and multi-component transport, confirming accuracy of experimental techniques. Results suggest that the large effects observed in the turbulent bluff-body burner are cause by preferential transport of H₂ and H₂O through the preheat zone ahead of CO₂ and CO, followed by convective transport downstream and away from the local flame brush. This preferential transport effect increases with increasing velocity of reactants past the bluff body and is apparently amplified by the presence of a strong recirculation zone where excess CO₂ is accumulated.     

An experimental and numerical study on characteristics of laminar premixed H2/CO/CH4/air flames

The effects of variations in the fuel composition on the characteristics of H₂/CO/CH₄/air flames of gasified biomass are investigated experimentally and numerically. Experimental measurements and numerical simulations of the flame front position and temperature are performed in the premixed stoichiometric H₂/CO/CH₄/air opposed-jet flames with various H₂ and CO contents in the fuel. The adiabatic flame temperatures and laminar burning velocities are calculated using the EQUIL and PREMIX codes of Chemkin collection 3.5, respectively. Whereas the flame structures of the laminar premixed stoichiometric H₂/CO/CH₄/air opposed-jet flames are simulated using the OPPDIF package with the GRI-Mech 3.0 chemical kinetic mechanisms and detailed transport properties. The measured flame front position and temperature of the stoichiometric H₂/CO/CH₄/air opposed-jet flames are closely predicted by the numerical calculations. Detailed analysis of the calculated chemical kinetic structures reveals that the reaction rate of reactions (R38), (R46), and (R84) increase with increasing H₂ content in the fuel mixture. It is also found that the increase in the laminar flame speed with H₂ addition is most likely due to an increase in active radicals during combustion (chemical effect), rather than from changes in the adiabatic flame temperature (thermal effect). Chemical kinetic structure and sensitivity analyses indicate that for the stoichiometric H₂/CO/CH₄/air flames with fixed H₂ concentration in the fuel mixture, the reactions (R99) and (R46) play a dominant role in affecting the laminar burning velocity as the CO content in the fuel is increased.     

Measurements and modeling of SiCl4 combustion in a low-pressure H2/O2 flame

Laser-induced fluorescence (LIF) was used to measure temperature and OH concentration profiles as a function of distance from a McKenna-style burner in premixed one-dimensional low-pressure H₂/O₂/Ar SiCl₄-doped flames. The addition of SiCl₄ was shown to affect the flame temperature and OH concentration profiles. A gas-phase chemical kinetics mechanism for the combustion of SiCl₄ in an H₂/O₂/Ar flame was proposed, and experimental results were compared with predictions for a premixed one-dimensional laminar flame model based on CHEMKIN. The low-pressure flame data are sensitive to the overall kinetics of the mechanism. In order to obtain the best fit to the observed data for all flame configurations, we had to modify six different rates from our original estimates. None of the modified rates are well known for the temperature regime of our flame. Particle formation and surface chemistry were not taken into account.     

Measurement of propagation speeds in adiabatic flat and cellular premixed flames of C2H6+O2+CO2

Adiabatic burning velocities of premixed flat flames and propagation speeds of adiabatic cellular flames of mixtures of ethane+oxygen+carbon dioxide are reported. The oxygen content O₂/(O₂+CO₂) in the artificial air was varied from 26 to 35%. Nonstretched flames were stabilized on a perforated plate burner at 1 atm. A heat flux method was used to determine burning velocities under conditions when the net heat loss of the flame is zero. Under specific experimental conditions the flames become cellular; this leads to significant modification of the flame propagation speed. Measurements in cellular flames are presented and compared with those for laminar flat flames and also with qualitative predictions of a theoretical model. The onset of cellularity was observed throughout the stoichiometric range of the mixtures studied. Cellularity disappears when the flames become only slightly subadiabatic.     

A comparison of the heat transfer behaviors of biogas–H2 diffusion and premixed flames

An experimental study was conducted to investigate the influence of hydrogen addition on the heat transfer characteristics of a biogas (60%CH₄–40%CO₂) flame. Results show improved flame stability and higher flame temperature in the premixed flame upon hydrogen addition. Both temperature and burning speed are increased in 1.0 ≤ Ф ≤ 1.5. Comparison of the premixed and diffusion flames reveals that the former yields higher heat transfer than the latter, due to higher flame temperature and larger volume of hot gas in the premixed flame. The total heat transfer rates of the two flames show opposite trends with increasing level of hydrogen addition, which is explained by the different structures. In the premixed flame, the contact of large cool core with target plate configures the high-temperature flame zone to a radial location with larger distance from the stagnation point than that of the diffusion flame, contributing to its higher heat transfer rate.     

The role of in situ reforming in plasma enhanced ultra lean premixed methane/air flames

This paper describes a mechanism for the stabilization of ultra lean premixed methane/air flames by pulsed nonequilibrium plasma enhancement. It is shown that the pulsed discharge plasma produces a cool (～500–600 K) stream of relatively stable intermediate species including hydrogen (H₂) and carbon monoxide (CO), which play a central role in enhancing flame stability. This stream is readily visualized by ultraviolet emission from electronically excited hydroxyl (OH) radicals. The rotational and vibrational temperature of this “preflame” are determined from its emission spectrum. Qualitative imaging of the overall flame structure is obtained by planar laser-induced fluorescence measurements of OH. Preflame nitric oxide (NO) concentrations are determined by gas sampling chromatography. A simple numerical model of this plasma enhanced premixed flame is proposed that includes the generation of the preflame through plasma activation, and predicts the formation of a dual flame structure that arises when the preflame serves to pilot the combustion of the surrounding non-activated premixed flow. The calculation represents the plasma through its ability to produce an initial radical yield, which serves as a boundary condition for conventional flame simulations. The simulations also capture the presence of the preflame and the dual flame structure, and predict preflame levels of NO comparable to those measured. A subsequent pseudo-sensitivity analysis of the preflame shows that flame stability is most sensitive to the concentrations of H₂ and CO in the preflame. As a consequence of the role of H₂ and CO in enhancing the flame stability, the blowout limit extensions of methane/air and hydrogen/air mixtures in the absence/presence of a discharge are investigated experimentally. For methane/air mixtures, the blowout limit of the current burner is extended by ～10% in the presence of a discharge while comparable studies carried out in lean hydrogen/air flames fail to extend this limit.     

The influence of pressure on the control of premixed turbulent flames using an electric field

Previous investigations of the effects of electric fields on flames have shown the potential for stabilizing flames and reducing emissions with comparatively little effort, but were restricted to atmospheric pressure. In the present work the influence of the electric field on premixed turbulent jet flames at increased pressure is investigated. Besides the question of whether field effects persist at elevated pressure, it is of interest to find physically based scaling laws. The current work describes experiments with premixed turbulent seven-hole Bunsen-jet flames for pressures between 1 and 10 bar, where the exit velocity was held constant, and where electric fields of varied strength and direction were applied to the flame. Concentrations of CO, NO, and NO₂ were measured in the exhaust gas section. Experiments show that the electric field influence is clearly visible for increased pressures, without any indication that 10 bar should be an upper limit. CO emissions could be reduced by about 95%, irrespective of pressure. The decrease of CO was accompanied by an increase of NO_x by about 25%. Both of these effects can be understood qualitatively within the framework of a one-dimensional model. For reduced voltages up to 3.5 kV/bar the model correctly describes the current-voltage characteristics and leads to the conclusion that high pressure should favor rather than hamper electric field effects on flames. The electric power required for a CO reduction of 95% amounted to 0.1% of the thermal power. The improvement of the lean blowoff limit upon application of an electric field observed so far ranges from 1 to 3% and increases with pressure.