The structure of rich turbulent methane flames, with an equivalence ratio of 2.0, at high strain rates has been investigated based on simultaneous and instantaneous line profile measurements of the species mass fractions of CH4, O2, N2, H2O, CO2, CO, H2 and OH radical, together with gas temperature. The flames are stabilized by the hot combustion products from a stoichiometric large pilot flame surrounding a Bunsen burner. Two flames have been investigated at overall stretch rates of 2500 s-1 and 4167 s-1. One-dimensional combined UV Raman, Rayleigh, and laser-induced predissociation fluorescence (LIPF) technique has been applied. Measurements at different axial positions enable the flame structure to be studied at different turbulence levels. The instantaneous species mass fractions and temperature profiles are conditioned on both mixture fraction and a reaction progress variable, namely the H2O mass fraction, allowing a proper description of the partially premixed flame structure. The components of the scalar dissipation rate of both mixture fraction and progress variable in the radial direction are also measured. The flames are stabilized at rich conditions by radicals and heat transferred from the stoichiometric pilot flame. Stretch effects are found to he dominant in these flames, leading to local flame structures that correspond to flames in the distributed-reaction- zones regime. The pdf of the progress variable is found to be monomodal in all cases. The conditional mean scalar dissipation rate profile in mixture fraction space exhibits a local minimum at the reaction zone due to differential polynary diffusion effects. The scalar dissipation rates of the progress variable are of the same order of magnitude as those of the mixture fraction, when these are appropriately normalized. This indicates that molecular mixing in both variables is equally important. This also suggests that a two-variable formulation is necessary to model these flames.

Planar images of Rayleigh scattering and laser-induced predissociative OH-fluorescence (OH-LIPF) have been obtained simultaneously in turbulent premixed jet flames on a single-shot basis. The geometric structure of temperature and OH isocontours were extracted for fractal analysis. A power-law fractal behavior can be identified in the ensemble-averaged flame length measure. It was found that the inner and outer cut-off scales of OH contours are larger than those of the iso-temperature contours; while the OH images show comparatively smaller fractal dimensions. The joint-pdf's between flame temperature and OH LIPF signals at different heights are also derived to evaluate the flame stretch effect on local flame structure. Comparison of image pairs near the extinction limit suggests that Rayleigh thermometry is more adequate to characterize the fine-scale flame front wrinkling in highly stretched turbulent premixed flames.

A two-plane two-dimensional Rayleigh thermometry technique is applied to investigate the three-dimensional flame structure in highly stretched turbulent premixed flames beyond the flamelet regime. Experimental data of the preheat zone thickness, δF, and flame temperature conditioned at the maximum temperature gradient, T0, are reported. Broadening of the preheat zone thickness is observed and found to be correlated well with the increase of turbulence intensity. This suggests a pure hydrodynamic straining effect in a chemically inert preheat zone in the thin-reaction-zones regime, which is consistent with the rate-ratio asymptotic analysis. Although a general decrease of T0 is also found with increasing flame stretch, this temperature drop is subject to the nonadiabatic condition in the postflame region. Flame extinction would be expected when T0 is approaching the ignition temperature ≥ 900 K.

Simultaneous two-dimensional CH-LIF/Rayleigh measurements were carried out in highly stretched turbulent premixed stoichiometric methane-air flames. These flames fall into the thin reaction zones regime. In this regime, the Kolmogorov scale is smaller than the preheat zone thickness of a laminar flame, but it is larger than the reaction zone thickness. Therefore, small eddies can penetrate into the preheat zone but not into the reaction zone. These small eddies widen the preheat zone by turbulent mixing. In the present flames at Karlovitz numbers Ka of 23 and 91, thin reaction zones with relatively thick turbulent preheat zones are being observed. The thickness of the preheat zone is expected to scale with the mixing length scale lm, which is the thickness of an eddy within the inertial range that has a turnover time equal to the flame time. The temperature/CH images are presented at different axial locations together with line profiles through the reaction zone to illustrate the different structures. In addition probability density functions (PDFs), of temperature conditioned on CH are presented. The present data show that the temperature in the thin reaction zones' regime at the early positions in the highly stretched flames is relatively low. This is attributed to heat loss to the burner. In addition, in highly stretched flames at the borderline of this regime, local extinction has sometimes been observed, which could be due to entrainment of small eddies into the reaction zone.

A lifted laminar axisymmetric diffusion flame is stabilized in the downstream region of a diluted methane jet that is surrounded by a lean methane-air co-flow and an outer co-flow of air. The flame shows a distinct triple flame structure in the stabilization region. It is investigated experimentally by PIV for the velocity field, OH-LIPF imaging, C2H(x)-LIF imaging, and a 1D-Raman technique for major species concentrations, combined with a Rayleigh technique for temperature. This is complemented by numerical simulations solving the two-dimensional axisymmetric Navier-Stokes equations in the zero Mach number limit on an adapted mesh, coupled with balance equations for temperature and species. A simplified model for molecular transport properties was used with constant, but non-unity, Lewis numbers for all species. Chemistry is represented by a ten-step reduced mechanism for methane oxidation, which was derived starting from a 61-step elementary mechanism that includes the C1 and C2 chains. The agreement between the measured and the predicted flow field is very satisfactory. Owing to gas expansion, the velocity decreases immediately ahead of the flame and increases strongly at the flame front. Further downstream acceleration due to buoyancy is dominant and is predicted accurately. There is a good agreement between measurements and computations for flame shape and flame length. The measured OH-LIPF image and the computed OH concentrations indicate that OH is concentrated in the vicinity of stoichiometric mixture. The results from a newly developed C2H(x)-LIF method are also supported by calculations. While these measurements were only qualitative, the temperature and mole fractions of the major species could be measured quantitatively with the combined Raman-/Rayleigh technique along a line and were found to agree well with the numerical predictions. It is found that the structure is a triple flame and is influenced essentially by two external parameters: heat exchange between the branches and heat loss at the curved flame front near the triple point.

An imaging system was developed to resolve the instantaneous two-dimensional reaction zone structure in combustion media with combined Rayleigh thermometry and laser-induced saturated CH fluorescence technique. The carefully chosen excitation/detection strategy and high laser spectral intensity permit single-shot CH fluorescence imaging in premixed CH4/air flames where CH concentration is on the order of 1 ppm based on flamelet calculations. The present experimental conditions are also examined and shown to be suitable for quantitative measurements of CH radical based on the two-level model analysis. A linear relationship can be found between the measured CH signal intensity and the calculated CH concentration within a maximum 30% uncertainty range. The FWHM thickness of the CH profile in a stoichiometric laminar methane flame was shown to be less than 0.3 mm, which is the smallest ever achieved. Simultaneous image pairs of flame temperature and concentration of CH radicals from a premixed turbulent Bunsen flame at an exit velocity of 65 m/sec are obtained to demonstrate the system superiority of application on high-speed reacting flows.

One-dimensional simultaneous measurements of the species mass fractions of O2, H2, H2O, N2 and OH radical as well as flame temperature have been carried out in hydrogen jet diffusion flames diluted with Ar using the line-Raman/Rayleigh/LIPF-OH technique. Statistical information about the mixture fraction Z and scalar dissipation rate χ can be obtained for evaluation of current finite-chemistry combustion models for the turbulent nonpremixed flames. At an upstream position of x/d = 8, the flamelet approach is found to be qualitatively valid, in agreement with a larger Favre mixture fraction fluctuation than the reaction zone thickness in the Z-space. Transient effect, however, can be important in view of H2 and O2 superequilibrium. Preferential diffusion effects are negligible due to a relatively large Peclet number. Joint correlations between a reactive scalar T with χ and the conserved scalar Z with χ are found to be different from those reported in nonreacting flows. The observed distinct features can be explained based on the flamelet concept so that statistical independence is argued to be a good approximation. There is evidence showing that large-scale turbulent motion dominates scalar transport in the connected reaction zone regime. Thus, flamelet approach is also favored. Some modeling assumptions used in the flamelet model and the CMC method are discussed. Model refinements based on the present experimental data are suggested as well.

A new bread oven has been developed, tested and presented in this work for local balady bread. The design has the advantage of being efficient and producing unpolluted bread. An extensive study of the conventional and available designs has been carried out in order to help developing the new design. Evaluation of the conventional design is based on numerous tests and measurements. A computer code utilizing the indirect method has been developed to evaluate the thermal performance of the tested ovens. The present design achieves higher thermal efficiency of about 50% than the conventional ones. In addition, its capital cost is much cheaper than other imported designs. Thus, the present design achieves higher efficiency, pollutant free products and less cost. Moreover, it maybe modified for different types of bread baking systems.

The premixed stoichiometric turbulent methane flames are investigated on a piloted Bunsen burner with a nozzle diameter of 12 mm and mean nozzle exit velocities of 65, 50, and 30 m/s. Advanced laser diagnostics of the flow field using two-component and two-point laser Doppler anenometer (LDA), as well as of the scalar fields with 2-D Rayleigh thermometry and line Raman/Rayleigh laser-induced predissociation fluorescence (LIPF)-OH techniques, are applied to obtain both the instantaneous and mean flame structure in terms of velocity, temperature, and major species concentrations, as well as turbulent kinetic energy and length scales. In terms of their location on the combustion diagram, the three flames cover the entire range of the distributed-reaction-zones regime from the borderline to the well-stirred reactor regime to the flamelet regime. Measurements were from X/D = 2.5 above the nozzle exit plane to X/D = 12.5 downstream. Thus, a complete database is established for comparison with the numerical predictions. Within the mixing layer between the unburnt gas and the pilot flame, the instantaneous temperatures are much lower than the adiabatic flame temperature due to the short residence time and heat loss to the burner. With increasing residence time the mean flame temperature increases in the axial direction. The radial mixing of the turbulence generated with the shear layers between the nozzle jet stream and surrounding pilot stream is supressed, such that the turbulence kinetic energy remains nearly constant on the centerline. From the two-dimensional (2D) temperature fields instantaneous iso-temperature contours are plotted showing broad regions where burnt and unburnt gas are partially mixed. These regions are interpreted in terms of the quench scale l(q) = (ετ(c)3)(1/2). The measured values of the flame brush thickness are proportional to the quench scale for the two high-velocity flames, whereas the low-velocity flame exhibits essential flamelet behavior. The premixed stoichiometric turbulent methane flames were studied on a piloted Bunsen burner. The instantaneous and mean flame structure of the flames were measured in terms of velocity, temperature, and major species concentrations as well as turbulent kinetic energy and length scales. The instantaneous temperatures between the unburnt gas and the pilot flame were much lower than the adiabatic flame temperature due to the short residence time. Mean flame temperature increased proportionally with residence time.

We have applied a line UV Raman, Rayleigh, and laser-induced predissociation fluorescence technique for measurement of turbulent hydrocarbon flames. The species concentration of CO2, O2, CO, N2, CH4, H2O, OH, and H2 and the temperature are measured instantaneously and simultaneously along a line of 11.4 mm, from which the gradients with respect to mixture fraction and spatial direction are obtained. The technique has been successfully tested in a laminar premixed stoichiometric methane flame and a laminar hydrogen diffusion flame. In addition the technique has been tested in a highly turbulent rich premixed methane flame. The data show that the technique can be used to provide instantaneous measurements of local profiles that describe the local flame structure in highly turbulent flames. © 1996 Optical Society of America.

The instantaneous as well as conditionally averaged flame structure of a 78% H2-22% Ar jet diffusion flame is investigated with the Line-Raman/Rayleigh/LIPF-OH technique. Radial profiles of major species concentration, flame temperature, and OH concentration are measured along a line 10,5 mm long at two exit velocities and several axial positions. Statistical distributions of mixture fraction and one-dimensional scalar dissipation rate at different turbulence levels can be obtained to validate current model assumptions. The difference between upstream flamelets and downstream connected reaction zones can be inferred from the simultaneously measured multipoint scalar profiles in the mixture fraction space. Comparison with flamelet calculations shows that in the near field close to the nozzle region, flamelet behavior is qualitatively preserved. At positions farther downstream, the root mean square (rms) of the instantaneous mixture fraction in the mean reaction zone =st becomes smaller than the reaction zone width. Connected reaction zones are therefore a more appropriate conceptual model. Preferential molecular diffusion is found to be unimportant under strong small-scale turbulent mixing inside the jet flame, which justified the Lc=1 assumption for calculation of hydrogen diffusion flamelets at high strain rates. The probability density function of the measured one-dimensional scalar dissipation rates is lognormal at downstream positions but becomes more skewed when moving upstream. The mean scalar dissipation rate scales inversely with the streamwise distance in the axial direction, showing a rather slower decay than that in the cold flows. In addition, a local minimum of the radial scalar dissipation rate near the instantaneous reaction zone position is found at all the measuring stations and can be attributed to the thermal expansion effect and low turbulence level of the surrounding air. © 1996 Combustion Institute.

A two-plane two-dimensional Rayleigh thermometry technique is presented for measurements in turbulent hydrocarbon flames. UV Rayleigh thermometry is used in this technique for what is to the author’s knowledge the first time. It shows the advantages of using UV excimer lasers rather than visible lasers for Rayleigh scattering. The present technique is useful for studying the three-dimensional structure of the reaction zone in turbulent flames. © 1993 Optical Society of America.

Two-plane two-dimensional Rayleigh thermometry measurements have been carried out in turbulent premixed methane-helium-air flames in order to study the 3-D structure of the reaction zone. Three piloted premixed flames have been investigated at different Reynolds numbers near extinction. The instantaneous temperature, its mean profiles and rms fluctuations as well as the pdfs of the reaction zone thickness are presented in this paper. Also, the pdfs of the reaction zone location are presented. Helium has been added to the premixed jet in order to adjust the Rayleight cross-section of the fuel-air mixture to equal that of the surrounding air. This does not change the chemistry of the flame. The data in this paper show that the temperature, instantaneous, mean or rms, is reduced by stretch indicating significant chemical kinetic effects. Also, there is some evidence of extinguished parcels in the flame near extinction. On approaching extinction, the flame thickness increases and the deviation of reaction zone from its mean position is reduced. © 1992 Combustion Institute.

Spontaneous Raman/Rayleigh measurements have been carried out in turbulent partially premixed flames of nitrogen-diluted methane near extinction. The flames are created in a reverse flow reactor (RFR) and are stabilized by means of a recirculation zone. The flames are stretched by reducing the residence time of the flow within the reactor. The mean profiles, scatter plots, and conditional pdfs are used to study the flame structure in the present investigation. The detailed structure studies have been carried out in two shear layers, where the stretch rates are highest. The data presented in this article are for two flames close to extinction at low residence times (3.6 and 5.1 ms). The flame structure at both shear layers shows quite significant chemical kinetic effects on approaching extinction. These effects reduce the products concentration and temperature and increase the reactants. Also, these effects increase the CO concentration. A substantial decrease in the reactedness of the reactive scalars has also been found at both shear layers on approaching extinction. The flame structure shows broad distribution between the equilibrium and frozen limits with no obvious bimodality. From the conditional pdfs, the reactedness decreases around stoichiometric and increases at the lean side of the stoichiometric. © 1991.

Spatial-averaging effects on laser-based measurements of scalar quantities in turbulent flames are investigated. Raman/Rayleigh measurements are made in the shear layers of a turbulent reverse flow reactor (RFR) with two different probe volumes to study the effects on the measured mean, rms, and probability density functions (pdfs). In addition, the errors in the measured variance are estimated by scalar spectrum analysis for an isotropic flow, using the Pao-Corrsin scalar spectrum. The data show that spatial averaging reduces the rms fluctuations of the species concentrations and Rayleigh signal. Also, the form of the pdf is affected in such a way that for a monomodal distribution, it may reduce any sharp peak, whereas for a bimodal distribution it reduces the peaks and fills the gap in between, i.e, reduces its bimodality. These errors are slightly higher for reacting species and the Rayleigh signal data than for nonreacting species. For the measurements reported here the effects are not large enough to change the overall shape of the pdf greatly. The analytical estimates agree quite well with the experimental data, and the theory shows that the effect of the length of the sensor on the variance depends on both the integral scale of the turbulence and the microscale of the scalar, which are related by the turbulence Reynolds number. © 1990.

Imatinib mesylate (IM) is the gold standard for treatment of Chronic Myeloid Leukemia (CML). This study aimed to gain more knowledge of the altered PK, pharmacogenetic factors, and gene expression leading to variable IM levels. Fifty patients with chronic phase-CML were enrolled in this study and divided as 25 responders and 25 non-responders (patients are directly recruited after response assessment). HPLC/MS/MS was used to determine trough and peak concentration of imatinib and N-desmethyl imatinib in the blood. PCR-RFLP technique was used to detect IDH1 gene mutation (R132). The median value of IM trough level was significantly higher, the P/T ratio was significantly lower and the α-1-acid glycoprotein (AGP) was significantly higher among responders compared to non-responders (P=0.007, 0.009 and 0.048, respectively). Higher N-desmethyl imatinib peak plasma concentration was observed with low mRNA expression of ABCG2 and OCT1 (P=0.01 and 0.037, respectively). IDH1 R132 gene mutation was associated with a significant increase in toxicities (P=0.028). In conclusion, IM trough level, P/T ratio and AGP was significantly higher in responders. In addition, ABCG2 and OCT1 gene expression may affect the interindividual PK variation. Although a prospective study with a larger patient population is necessary to validate these findings. IDH1 mutation is a predictor of increased toxicity with IM treatment.

Novel reliable biomarkers of inflammatory bowel disease (IBD) are clinically imperative due to potential limitations of endoscopic techniques. MicroRNAs (miRNAs) have emerged as non-invasive biomarkers of IBD; however, the full disease-specific miRNAs signature for IBD subtypes remains elusive. We evaluated the diagnostic role of circulating miR-486 and miR-25 in IBD patients and their potential ability to discriminate IBD subtypes; ulcerative colitis (UC) and Crohn's disease (CD). Sixty UC patients, 60 CD patients, and 60 healthy controls were recruited. Serum miRNA expression was determined using RT-qPCR. Bioinformatics was employed for target gene and protein-protein interaction (PPI) network analyses. Serum miR-486 was upregulated in CD patients, but didn't change in UC patients compared to controls. Conversely, serum miR-25 was decreased in both CD and UC patients compared to controls. Only miR-486 was differentially expressed between UC and CD patients. Receiver-operating characteristic analysis revealed that serum miR-486 was superior in CD diagnosis (AUC=0.945) and significantly distinguished CD and UC patients, whereas miR-25 showed discriminative potential for both UC and CD from controls. In the multivariate logistic analysis only miR-486 was associated with the risk of CD diagnosis. Serum miR-486 was correlated with CD activity index and location of disease in CD patients, whereas miR-25 was correlated with the type/extent of UC. PPI network analysis revealed common target genes and signaling pathways for both miRNAs. Conclusively, serum miR-486 and miR-25 might serve as new biomarkers of IBD, with serum miR-486 could be employed in risk stratification of IBD subtypes and has the ground for clinical utility in CD diagnosis, whereas miR-25 has potential for UC and CD diagnosis.