Atomization of broad specification aircraft fuels

The atomization properties of liquid fuels for the potential use in aircraft gas turbine engines are discussed. The significance of these properties are addressed with respect to the ignition and subsequent combustion behavior of the fuel spray/air mixture. It is shown that the fuel properties which affect the atomization behavior (viscosity, surface tension, and density) are less favorable for the broad specification fuels as compared to with those for conventional fuels

Thermal Decomposition and Combustion of γ-irradiated Polyamide 6 Containing Phosphorus Oxynitride or Phospham

Polyamide 6 (PA-6) containing the fire retardants phosphorus oxynitride ((PON)m) or phospham ((PN2H)n) was exposed to 60Co-γ-rays (absorbed dose: 1.0–4.0 MGy). The irradiation led to crosslinking of the polymer which caused an increase in the char yield and a decrease in the flammability of the polymer. The combustion behavior was strongly affected by irradiation: dripping was totally prevented in the case of system PA-6/(PN2H)n and strongly retarded in the case of system PA-6/(PON)m. The thermal stability of the system PA-6/(PN2H)n decreased with increasing absorbed dose whereas the thermal stability of the system PA-6/(PON)m did not change

Ignition and combustion of metallized propellants

The overall objective is the development of a fundamental understanding of the ignition and combustion of aluminum-based slurry (or gel) propellant droplets using a combination of experiment and analysis. Specific objectives are the following: (1) The development and application of a burner/spray rig and single particle optical diagnosis to study the detailed ignition and combustion behavior of small droplets; (2) Understanding the role of surfactants and gellants (or other additives) in promoting or inhibiting secondary atomization of propellant droplets; and (3) The extension of previously developed analytical models and the development of new models to address the phenomena associated with microexplosions (secondary atomization)

PC programs for the prediction of the linear stability behavior of liquid propellant propulsion systems and application to current MSFC rocket engine test programs, volume 1

Research on propulsion stability (chugging and acoustic modes), and propellant valve control was investigated. As part of the activation of the new liquid propulsion test facilities, it is necessary to analyze total propulsion system stability. To accomplish this, several codes were built to run on desktop 386 machines. These codes enable one to analyze the stability question associated with the propellant feed systems. In addition, further work was adapted to this computing environment and furnished along with other codes. This latter inclusion furnishes those interested in high frequency oscillatory combustion behavior (that does not couple to the feed system) a set of codes for study of proposed liquid rocket engines

The combustion behavior of epoxy‐based multifunctional electrolytes

Multifunctional or structural electrolytes are characterized by ionic conductivity high enough to be used in the electrochemical devices and mechanical performance suitable for the structural applications. Preliminary insights are provided into the combustion behavior of structural bi‐continuous electrolytes based on bisphenol A diglycidyl ether (DGEBA), synthesized using the techniques of reaction induced phase separation and emulsion templating. The effect of the composition of the structural electrolytes and external heat flux on the behavior of the formulations were studied using a cone calorimeter with gases formed during testing analyzed using FTIR. The composition of the formulations investigated was changed by varying the type and amount of the ion conductive part of the bi‐continuous electrolyte. Two ionic liquids, 1‐ethyl‐3‐methylimidazolium bis(fluorosulfonyl)imide (EMIM‐TFSI) and 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIM‐BF4), as well as a deep eutectic solvent (DES) based on ethylene glycol and choline chloride, were used. The results obtained confirm that time to ignition, heat release rate (HRR), total mass loss, as well as the composition of the gases released during tests depend on the composition of the formulations. Addition of liquid electrolyte is found to reduce the time to ignition by up to 10% and the burning time by between 28% and 60% with the added benefit of reducing the HRR by at least 34%. Gaseous products such as CO2, CO, H2O, CH4, C2H2, N2O, NO, and HCN were detected for all formulations with the gases SO2, NH3, HCl, C2H4, and NH3 found to be for certain formulations only

A Hybrid Droplet Vaporization-Chemical Surrogate Approach for Emulating Vaporization, Physical Properties, and Chemical Combustion Behavior of Multicomponent Fuels

The complex nature of multicomponent aviation fuels presents a daunting task for accurately simulating combustion behavior without incurring impractical computational costs. To reduce computation time, chemical fuel surrogates comprised of only a few species are used to emulate the combustion of complex pre-vaporized fuels. These surrogates are often unable to match the vaporization behavior and physical properties of the real fuel and fail to capture the effect of preferential vaporization on combustion behavior. Therefore, a computationally efficient, hybrid droplet vaporization-chemical surrogate approach has been developed which emulates both the physical and chemical properties of a multicomponent kerosene fuel. The droplet vaporization/physical portion of the hybrid uses the Coupled Algebraic–Direct Quadrature Method of Moments with delumping to accurately solve for the evolution of every discrete species in a vaporizing fuel droplet with the computational efficiency of a continuous thermodynamic model. The chemical surrogate portion of the hybrid is linked to the vaporization model using a functional group matching method, which creates an instantaneous surrogate composition to match the distribution of chemical functional groups (CH2, (CH2)n, CH3 and Benzyl-type) in the vaporization flux of the full fuel. The result is a hybrid method which can accurately and efficiently predict time-dependent, distillation-resolved combustion property targets of the vaporizing fuel and can be used to investigate the effects of preferential vaporization on combustion behavior

Influence of diesel surrogates on the behavior of simplified spray models

Numerous experimental investigations make use of diesel surrogates to make the computational time reasonable. In the few studies where measured (surrogate and real diesel) and computed (surrogate only) results have been compared, the selection methodology for the surrogate constituent compounds and the measures taken to validate the chemical kinetic models are not discussed, and the range of operating conditions used is often small. Additionally, most simplified models use tuning variables to fit model results to measurements. This work makes the comparison between some frequently used diesel surrogates using a simple 1D vaporizing spray model, with the spray cone angle as the tuning parameter. Results show that liquid length and fuel fraction strongly depend on the physical properties of the used fuel for a fixed spray angle. These parameters are important for modeling auto-ignition and pollutant formation. The spray angle is varied till the spray length is the same for each surrogate. Results show important differences between other spray parameters such as local mixture fraction and axial velocity

Comparison of numerical and experimental results of four liquid spray combustors

Validation of CFD predictions for liquid spray combustion application is a challenging task due to difficulties in both modeling and experimental measurements. Validation is considered to be a key step for successful CFD predictions of combustion systems. The goals of this thesis are threefold: (1) validation of models used for spray combustion predictions, (2) using the validated predictions to explain steady flow and combustion physics, and (3) using the validated procedure to simulate conditions where unstable combustion behavior is observed experimentally, and to explore if such unstable behavior can be predicted correctly. The model validation is done with respect to three experimental data sets for spray combustors, and it is shown that predictions match data reasonably well. The validated code is then used to predict and understand the flow and combustion behavior for both steady and unsteady combustion conditions

Grindability and combustion behavior of coal and torrefied biomass blends

Biomass samples (pine, black poplar and chestnut woodchips) were torrefied to improve their grindability before being combusted in blends with coal. Torrefaction temperatures between 240 and 300 °C and residence times between 11 and 43 min were studied. The grindability of the torrefied biomass, evaluated from the particle size distribution of the ground sample, significantly improved compared to raw biomass. Higher temperatures increased the proportion of smaller-sized particles after grinding. Torrefied chestnut woodchips (280 °C, 22 min) showed the best grinding properties. This sample was blended with coal (5–55 wt.% biomass). The addition of torrefied biomass to coal up to 15 wt.% did not significantly increase the proportion of large-sized particles after grinding. No relevant differences in the burnout value were detected between the coal and coal/torrefied biomass blends due to the high reactivity of the coal. NO and SO2 emissions decreased as the percentage of torrefied biomass in the blend with coal increased.This work was part of the subcontracted contribution of INCAR to a project carried out by EDP Spain with the financial support from the European Regional Development Fund (ERDF) and acting IDEPA (Economic Development Agency of the Principality of Asturias) as research funding agency (Ref.: IDE/2013/000233). The authors thank A. J. Martín, member of the PrEM group at INCAR-CSIC, for his contribution.Peer reviewe