Premixed System Research Articles

An Analysis of Critical Ignition and Extinction Diameters of Solid Particles

This paper gives an analysis of the influence of solid matter consumption on the critical diameters for the ignition and extinction of a single particle of solid fuel. The Thomas theory of ignition with reactant consumption for the pre-mixed system was adopted for obtaining the formula for the critical diameters of ignition and extinction. The calculations made for the coal particle show that consumption deflects the critical diameter of extinction about two times stronger than that for ignition

Ongoing Development of a Low Emission Industrial Gas Turbine Combustion Chamber

Experiments were performed in laboratory-and full-scale combustors to test the feasibility of meeting proposed EPA emission standards. It was found that by uniformly mixing gaseous fuel and primary zone air prior to combustion and burning fuel leanly (equivalence ratio <1.0), it was possible to meet the proposed emission standards in an industrial gas turbine. The characteristic narrow range of flame stability obtained with lean premix combustion necessitated the use of fuel staging or variable geometry to handle the operational range of the engine. Fuel staging was selected for its relative simplicity. Consequently, EPA proposed emission standards were met only over a narrow range covering the engine operation at and near the design point. Experiments on small scale models of various sizes operated with gaseous and liquid fuels showed that, contrary to expectation, NOx production from a lean premix combustion system is independent of the system pressure in the pressure range investigated (1 atm to 16 atm). The desirability of high combustor inlet temperature and pressure for premixing was indicated. Despite the complexities of premixing fuel and air, such a combustion system, in addition to meeting the proposed emission standards, offers advantages such as easing of combustor wall cooling problems, improved combustor exit temperature distribution, and freedom from exhaust and primary zone smoke.

モデル燃焼器による低汚染燃焼法の実験的研究

An experimental study was made to investigate the mixing and NOx formation in a swirlstabilized, diffusion-type flame in a model combustor operating at lean fuel/air ratios. The city gas was injected from a fuel injector into an air flow passed through a swirler. The temperature, stable species and NOx concentration profiles in the combustor were measured over a range of air flow velocities through the swirler from 5 to 20m/s, fuel injection velocities from 36.4 to 145.4m/s, overall equivalence ratios Φ from 0.2 to 0.8 and nominal fuel injection angles from 60° to 180°. The effects of these parameters on NOx concentration in the flame zone and the emission level of NOx from the combustor were discussed. The effects of mixing rates were also estimated by examination of the local equivalence ratio profiles across the flame zone.In general, the flame clearly showed the characteristics of a fuel jet flame near the fuel injector. The temperature and the concentration profiles across the main flame zone and the recirculation zone change considerably with change in Φ. In the case of comparatively low value of Φ, it was shown that the high mixing rate had the effect of lowering the local equivalence ratio in the flame zone and the combustion gas temperature early in the post-flame zone. Then, the emission levels of NOx can be reduced by achieving high mixing rate due to the increase of air flow velocity and the variation of the fuel injection angle, at the expense of slight increase of the emission levels of CO.The minimum emission level of NOx obtained is 0.23g NO2/kg fuel at Φ of 0.2. Although the emission levels of NOx from the present combustor are still higher than those from lean premixed system, they were found to be much lower than those from conventional diffusion flame combustor.

Premix copolymer cement materials

Studies to determine the influence of mixtures of monomers (and subsequently copolymers) on the behaviour of premix copolymer cement materials are described in this paper. Five system viz styreneacrylonitrile, styrene-vinyl acetate, methyl methacrylate - vinyl acetate, butyl methacrylate - methyl methacrylate and butyl acrylate - methyl methcrylate, were investigated. Setting time and hydration studies were carried out on premix cement pastes while compressive strength tests were carried out on premix mortars, to determine the influence of monomer volume, surfactants and polymerisation method. The results indicated, as has most of the work on premix systems, that the influence of the copolymers was to increase setting time, decrease the degree of hydration as measured by percentage of chemically combined water and decrease strength relative to that of specimens continuously moist cured.

Spectrometric Study of Shock-Heated Mg/MgO Particle Dispersions

Abstract Homogeneous kinetics may play a large role in dictating diffusion flame structure for metals like Mg. A premixed metal vapor-oxygen system for studying these kinetics was approximated by the combination of a shock tube with an exploding Mg wire particle generator. This portion of the study was unsuccessful because the experimental data indicate the dispersion to consist of MgO rather than Mg particles. A kinetic mechanism is postulated which is consistent with the spectrometric observations. Certain wave interactions in the shock tube which severely curtail experimental times behind the reflected shock are also discussed.

Stability of Riboflavin in Premixes

During the past few years extensive use has been made of the premix system for incorporating crystalline riboflavin in poultry feeds. It has been common practice for feed manufacturers to prepare at one time sufficient riboflavin premix to meet their feed mixing requirements for a considerable period of time. The present study was undertaken to determine whether or not any loss of riboflavin occurred during the storage of riboflavin premixes.In the work reported, four different feedstuffs were used as “carriers,” namely, buttermilk powder, meat meal, fish meal, and wheat middlings. The premixes were prepared by mixing twenty pounds of “carrier” with an appropriate amount of crystalline riboflavin1 in a mechanical batch mixer for thirty minutes. Sufficient crystalline riboflavin was added to increase the riboflavin content of the “carrier” by 350 micrograms per gram in the case of buttermilk powder and by 250 micrograms per gram in the case of .