Laminar burning velocity of hydrogen and flame structure of related fuels for detailed kinetic model validation

The laminar burning velocity and the flame structure are common targets for combustion studies aimed at detailed kinetic model development. In the present work, fuels relevant to hydrogen combustion were considered. The laminar burning velocity of rich and lean hydrogen flames was studied experimentally and numerically, including its pressure dependence in rich mixtures and temperature dependence in lean mixtures. An updated version of the Konnov detailed reaction mechanism for H2 combustion was validated, and after that it was applied to simulate the results obtained in experiments. The laminar burning velocities of rich H2 + air mixtures were determined from spherical flame propagation data using three models for stretch correction available in the literature. The heat flux method was employed for the first time to measure the laminar burning velocity of lean H2 + air mixtures and its temperature dependence. A modified procedure for processing data from unstable cellular flames was suggested, and its accuracy was evaluated. The observed difference between the literature results obtained in stretched flames and the values measured in the present work in flat flames was discussed. The trends in the temperature dependence of the burning velocity of lean H2 + air mixtures, indicated by the modeling but not supported by the majority of data determined from literature values, were confirmed experimentally in the present work. An analysis of the experimental uncertainties of the heat flux method was performed. It was shown that some of the factors which affect the accuracy of the measurements are related to the temperature dependence of the laminar burning velocity. A method to evaluate asymmetric heat fluxes in the plate of the heat flux burner was proposed. The work reported in the present study resulted in the necessity to re-evaluate some of the previously published data. Based on the available information from literature, as well as on the results obtained in the present study, recommendations were made on how to control or reduce several experimental uncertainties associated with the heat flux method. The structure of NH3 and CH4 flames was investigated with the aim of further kinetic model development. Intracavity laser absorption spectroscopy was applied to record HCO concentration profiles in rich low-pressure CH4 mixtures and predictions of two widely used kinetic models were analyzed. Minor and major species concentrations in NH3 + air flames were used to validate four contemporary H/N/O reaction schemes and investigate the performance of the best one

The Evolution of Multicomponent Systems at High Pressures: VI. The Thermodynamic Stability of the Hydrogen-Carbon System: The Genesis of Hydrocarbons and the Origin of Petroleum

The spontaneous genesis of hydrocarbons which comprise natural petroleum have been analyzed by chemical thermodynamic stability theory. The constraints imposed upon chemical evolution by the second law of thermodynamics are briefly reviewed; and the effective prohibition of transformation, in the regime of temperatures and pressures characteristic of the near-surface crust of the Earth, of biological molecules into hydrocarbon molecules heavier than methane is recognized. A general, first-principles equation of state has been developed by extending scaled particle theory (SPT) and by using the technique of the factored partition function of the Simplified Perturbed Hard Chain Theory (SPHCT). The chemical potentials, and the respective thermodynamic Affinity, have been calculated for typical components of the hydrogen-carbon (H-C) system over a range pressures between 1-100 kbar, and at temperatures consistent with those of the depths of the Earth at such pressures. The theoretical analyses establish that the normal alkanes, the homologous hydrocarbon group of lowest chemical potential, evolve only at pressures greater than approximately thirty kbar, excepting only the lightest, methane. The pressure of thirty kbar corresponds to depths of approximately 100 km. Special high-pressure apparatus has been designed which permits investigations at pressures to 50 kbar and temperatures to 2000 K, and which also allows rapid cooling while maintaining high pressures. The high-pressure genesis of petroleum hydrocarbons has been demonstrated using only the solid reagents iron oxide, FeO, and marble, CaCO3, 99.9% pure and wet with triple-distilled water

Tendencies of interaction between Russian universities and companies implementing innovative development programs

The main aim of this article is to analyze key indicators and trends of global innovative development and their role in development. Attention is given to the consideration of several mechanisms of interaction between universities and state companies, with concrete measures and steps that can be used in economic policy. The authors analyze the real experience of the Russian economy now. Based on collected data for the total volume of R&D, revenues and the number of patents, regression models were constructed to determine the relationship between the named indicators. Recommendations and innovative ideas to improve the economic policy are given to achieve the goals and to justify the use of mechanisms of "compulsion to innovate" in state companies for the implementation of more productive development programs.peer-reviewe

Laminar premixed flat non-stretched lean flames of hydrogen in air

Laminar burning velocity of lean hydrogen + air flames at standard conditions is still a debated topic in combustion. The existing burning velocity measurements possess a large spread due to the use of different measurement techniques and data processing approaches. The biggest uncertainty factor in these measurements comes from the necessity to perform extrapolation to the flat flame conditions, since all of the previously obtained data were recorded in stretched flames. In the present study, laminar burning velocity of lean hydrogen + air flames and its temperature dependence were for the first time studied in stretch-free flat flames on a heat flux burner. The equivalence ratio was varied from 0.375 to 0.5 and the range of the unburned gas temperatures was 278-358 K. The flat flames tended to form cells at adiabatic conditions, therefore special attention was paid to the issue of their appearance. The shape of the flames was monitored by taking OH* images with an EM-CCD camera. In most cases, the burning velocity had to be extrapolated from flat subadiabatic conditions, and the impact of this procedure was quantified by performing measurements in H-2 + air mixtures diluted by N-2. The effect of extrapolation was estimated to be of negligible importance for the flames at standard conditions. The measured burning velocities at 298 K showed an important difference to the previously obtained literature values. The temperature dependence of the burning velocity was extracted from the measured results. It was found to be in agreement with the trends predicted by the detailed kinetic modeling, as opposed to a vast majority of the available literature data. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved

Models of normative consolidation of the municipal police constitutional and legal status

The article is devoted to the comparative legal analysis of normative general and specialized legal acts, which indirectly or directly fix the constitutional and legal status of the lower level of public order protection bodies - the municipal police. The relevance of this study is explained by the attribution of local self-government bodies to the number of subjects of public order protection in the Russian Federation through the establishment of the municipal police, after the adoption of a specialized law on the municipal police. The comparative legal study made it possible to highlight the existing models of normative consolidation of the municipal police constitutional and legal status in accordance with the form of state structure

New Results on Generalized Graph Coloring

For graph classes \wp_1,...,\wp_k, Generalized Graph Coloring is the problem of deciding whether the vertex set of a given graph G can be partitioned into subsets V_1,...,V_k so that V_j induces a graph in the class \wp_j (j=1,2,...,k). If \wp_1=...=\wp_k is the class of edgeless graphs, then this problem coincides with the standard vertex k-COLORABILITY, which is known to be NP-complete for any k≥ 3. Recently, this result has been generalized by showing that if all \wp_i's are additive hereditary, then the generalized graph coloring is NP-hard, with the only exception of bipartite graphs. Clearly, a similar result follows when all the \wp_i's are co-additive

Consideration of soil strata heterogeneity influence on differential foundation settlements of overpasses for high-speed railways

The implementation of projects for the construction of high-speed railways actualizes the search of effective approaches to accounting the influence of soil strata heterogeneity along the course of the track on differential foundation settlements of overpasses. Russian special technical conditions prescribe sufficiently stringent regulation limits of absolute values of overpasses' foundation soil settlements (20 mm for ballastless track) and angles of break in profile (the differential foundation soil settlement), which should not exceed 1 ‰ for ballastless track. These requirements make it necessary to develop the calculation method, which is based on the criterion of deformation. To ensure compliance of design solutions to the specified regulations it is appropriate to use the method of the predefined equated soil settlements for design of shallow foundations of overpasses for high-speed railways. Several features of application of this method are presented in this article

Strategy for improved NH2 detection in combustion environments using an Alexandrite laser

A new scheme for NH2 detection by means of laser-induced fluorescence (LIF) with excitation around wavelength 385 nm, accessible using the second harmonic of a solid-state Alexandrite laser, is presented. Detection of NH2 was confirmed by identification of corresponding lines in fluorescence excitation spectra measured in premixed NH3-air flames and on NH2 radicals generated through NH3 photolysis in a nonreactive flow at ambient conditions. Moreover, spectral simulations allow for tentative NH2 line identification. Dispersed fluorescence emission spectra measured in flames and photolysis experiments showed lines attributed to vibrational bands of the NH2 A2A1 ← X2B1 transition but also a continuous structure, which in flame was observed to be dependent on nitrogen added to the fuel, apparently also generated by NH2. A general conclusion was that fluorescence interferences need to be carefully considered for NH2 diagnostics in this spectral region. Excitation for laser irradiances up to 0.2 GW/cm2 did not result in NH2 fluorescence saturation and allowed for efficient utilization of the available laser power without indication of laser-induced photochemistry. Compared with a previously employed excitation/detection scheme for NH2 at around 630 nm, excitation at 385.7 nm showed a factor of ~ 15 higher NH2 signal. The improved signal allowed for single-shot NH2 LIF imaging on centimeter scale in flame with signal-to-noise ratio of 3 for concentrations around 1000 ppm, suggesting a detection limit around 700 ppm. Thus, the presented approach for NH2 detection provides enhanced possibilities for characterization of fuel-nitrogen combustion chemistry

Some types of carbon-based nanomaterials as contrast agents for photoacoustic tomography

This paper is devoted to the study of various carbon-based nanomaterials as photoacoustic contrast agents. The research work was performed on agarose-based tissue phantom containing inclusions with and without carbon-based nanomaterials. The inclusion was created with the higher density compared to phantom in order to simulate a tumor. A specially designed photoacoustic probe was introduced for measuring a level of photoacoustic signal and its enhancement caused by the nanoinclusions presence. The probe consists of a buffer for time separation of the signal coming from the excitation source, piezoelectric transducer, and amplifier. A point-by-point measurement of the signal was performed to obtain a two-dimensional map from magnitude of photoacoustic signal and phase delay of the signal registration. From phase delay the 3D photoacoustic images were reconstructed by evaluation of the depth coordinate based on the tissue sound velocity. As an excitation source the light radiation from Nd:YAG laser with a 16 ns pulse duration and a 1064 nm wavelength was used. Firstly, we considered tissue phantom with a tumor covered by graphene oxide as a reference one. It has been shown that the use of graphene oxide leads to significant improvement of the image contrast. Further, the tumors labelled with nanodiamonds (NDs) and carbon fluoroxide (CFO) nanoparticles (NPs) were studied systematically. Amplitude of the photoacoustic signals registered from such tumor phantoms are one order of magnitude lower than the signal ensured by graphene oxide. All three types of the studied carbon-based nanomaterials (GO, NDs, CFO) give stable photoacoustic signal, this allows to consider them as good candidates for further in-vitro experiments in photoacoustic imaging for biological applications. The dependences of the signal level as a function of the NPs concentration were measured for types of NPs. Considering much more efficient penetration of NDs and CFO NPs inside the cells as well as their extremely low cytotoxicity, these both types of carbon nanomaterials could be used for further in-vivo experiments