Influence of liquid bridge force on physical stability during fuel storage and transportation

The physical stability of solid-liquid fuel is a factor that needs to be considered for fuel product practicability for storage and transportation. To determine the Influence of liquid bridge force on physical stability, two detection devices were designed. The laws obtained from microscopic experiments are used to verify the physical stability of fuel under different component ratios. The liquid bridge force is found to increase with the droplet volume. Multiliquid bridges above one critical saturation can generate significant resultant forces compared to single-liquid bridges of the same volume. There exist four states of solid-liquid mixed fuel with increasing liquid saturation rate. The liquid bridge force between the solid and liquid plays a dominant role in the physical stability of the first three states. There may be two stages involved in the stratification process for state 4 fuel, and the liquid viscosity is another factor that cannot be ignored. In the process of selecting a fuel ratio, a larger liquid bridge force between the components can be obtained by properly improving the wetting effect so that the fuel shows better physical stability.

Experimental and Numerical Study of the Effect of Fuel/Air Mixing Modes on NO_(x) and CO Emissions of MILD Combustion in a Boiler Burner

The Moderate or Intense Low-oxygen Dilution (MILD) combustion is characterized by low emissions,stable combustion and low noise for various kinds of fuel,which has great potential in the industry.The aim of this study is to investigate the effect of fuel/air mixing modes on NO_(x) and CO emissions of MILD combustion in a boiler burner by experiments and numerical simulations.Three types of fuel/air mixing modes (premixing mode,diffusion mode and hybrid mode) have been considered in this study.The realizable k-ε turbulent model and the Eddy Dissipation Concept (EDC) combustion model were used in numerical simulations.In addition to the temperature near the burner head,the calculation results match very well with the axial temperature distribution at the furnace center.The flow pattern under different mixing modes is similar,while the hybrid mode has a higher OH concentration near the diffusive fuel nozzle than the premixing mode,and the corresponding position of the peak OH concentration is closer to the rear half of the furnace.The distribution of temperature is extremely uniform for the premixing mode in the main reactive zone,which is typical for MILD combustion.There is a distinct area where the reaction temperature is higher than 1600 K for the hybrid mode.Moreover,in the main reactive zone,the gas recirculation ratio is high enough to ensure flue gas recirculation,which is beneficial to achieve MILD combustion at local areas.At the location where the axial distance is greater than 0.2 m,the gas recirculation ratio of the premixing mode is larger than that of the hybrid mode,which strengthens the entrainment of hot flue gas into the recirculated gas.The experimental results show that when the thermal intensity is less than 1.67 MW·m^(-3),the NO_(x) emissions are less than 15× 10^(-6)@3.5%O_(2) in near stoichiometric ratio in the premixing mode,and the CO emissions are less than 10× 10^(-6)@3.5%O2 under the same conditions.In the diffusion mode,the NO_(x) emissions are less than 30×10^(-6)@3.5%O_(2).In order to keep NO_(x) and CO emissions low,the hybrid modes with optimized fuel distribution ratio are found under different thermal intensities.

Research on combustion characteristics of scramjet combustor with different flight dynamic pressure conditions

Combustion characteristics in a scramjet combustor equipped with a thin strut were observed and discussed in this paper.A series of numerical simulations were carried out under different flight dynamic pressure conditions.The parameters of cold flow field and combustion field were used to analyze the combustion characteristics.Based on the basic data,the mixing efficiency,characteristics of flame establishment and propagation as well as combustion field characteristics were discussed in this paper.The influence laws of lower dynamic pressure conditions were further revealed to optimize combustor performance.Results indicated that properly reducing the flight dynamic pressure can enhance the mixing of kerosene.The diffusion of kerosene determined the distribution of combustion zone and heat release.Then,the influencing factor that affected the chemical reaction rate was revealed to shorten chemical reaction time.And the higher flight Mach number made the flame propagation velocity faster and the combustion stability stronger.The fuel mixing became the main factor and low dynamic pressure had little effect on laminar flame propagation velocity under high Mach number conditions.The investigations in this paper are helpful for understanding the combustion characteristics under low dynamic pressure conditions.

Effect of methane-hydrogen mixtures on flow and combustion of coherent jets

Coherent jets are widely used in electric arc furnace(EAF)steelmaking to increase the oxygen utilization and chemical reaction rates.However,the influence of fuel gas combustion on jet behavior is not fully understood yet.The flow and combustion characteristics of a coherent jet were thus investigated at steelmaking temperature using Fluent software,and a detailed chemical kinetic reaction mechanism was used in the combustion reaction model.The axial velocity and total temperature of the supersonic jet were measured via hot state experiments.The simulation results were compared with the experimental data and the empirical jet model proposed by Ito and Muchi and good consistency was obtained.The research results indicated that the potential core length of the coherent jet can be prolonged by optimizing the combustion effect of the fuel gas.Besides,the behavior of the supersonic jet in the subsonic section was also investigated,as it is an important factor for controlling the position of the oxygen lance.The investigation indicated that the attenuation of the coherent jet is more notable than that of the conventional jet in the subsonic section.