202 research outputs found
Data for: Co-Optima Fuels Combustion: A comprehensive Experimental Investigation of Prenol Isomers
No full textThis is the supporting experimental dat
Data for: Co-Optima Fuels Combustion: A comprehensive Experimental Investigation of Prenol Isomers
No full textThis is the supporting experimental dat
Thermal Stability Measurement of Alternative Jet Fuels Using Ellipsometry
No full textThermal stability is an important characteristic of alternative fuels that must be evaluated before they can be used in aviation engines. Thermal stability refers to the degree to which a fuel breaks down when it is heated prior to combustion. This characteristic is of great importance to the effectiveness of the fuel as a coolant and to the engine’s combustion performance. The thermal stability of Sasol IPK, a synthetic alternative to Jet-A, with varying levels of naphthalene has been studied on aluminum and stainless steel substrates at 300 to 400 °C. This was conducted using a spectroscopic ellipsometer to measure the thickness of deposits left on the heated substrates. Ellipsometry is an optical technique that measures the changes in a light beam’s polarization and intensity after it reflects from a thin film to determine the film’s physical and optical properties. It was observed that, as would be expected, increasing the temperature increased the deposit thickness for a constant concentration of naphthalene on both substrates. The repeatability of these measurements was verified using multiple trials at identical test conditions. Lastly, the effect of increasing the naphthalene concentration at a constant temperature was found to also increase the deposit thickness.</jats:p
Measurements of Propanal Ignition Delay Times and Species Time Histories Using Shock Tube and Laser Absorption
No full textPropanal is an aldehyde intermediate formed during the hydrocarbon combustion process. Potentially, the use of oxygenated biofuels reduces greenhouse gas emissions; however, it also results in increased toxic aldehyde by-products, mainly formaldehyde, acetaldehyde, acrolein, and propanal. These aldehydes are carcinogenic, and therefore it is important to understand their formation and destruction pathways in combustion systems. In this work, ignition delay times were measured behind reflected shock waves for stoichiometric (Φ = 1) mixtures of propanal (CH3CH2CHO) and oxygen (O2) in argon bath gas at temperatures of 1129 K \u3c T \u3c 1696 K and pressures around 1 and 6 atm. Measurements were conducted using the kinetics shock tube facility at the University of Central Florida. Current results were compared to available data in the literature as well as to the predictions of three propanal combustion kinetic models: Politecnico di Milano (POLIMI), National University of Ireland at Galway, and McGill mechanisms. In addition, a continuous wave-distributed feedback interband cascade laser centered at 3403.4 nm was used for measuring methane (CH4) and propanal time histories behind the reflected shock waves during propanal pyrolysis. Concentration time histories were obtained at temperatures between 1192 and 1388 K near 1 atm. Sensitivity analysis was carried for both ignition delay time and pyrolysis measurements to reveal the important reactions that were crucial to predicting the current experimental results. Adjustments to the POLIMI mechanism were adopted to better match the experimental data. Further research was suggested for the H abstraction reaction rates of propanal. In addition to extending the temperature and pressure region of literature ignition delay times, we provide the first high-temperature species concentration time histories during propanal pyrolysis
A kinetic model for the high-temperature oxidation of n-butanol based on recent shock tube/laser absorption experiments
No full textButanol is a very promising biofuel candidate that has received considerable attention from the combustion community. However, the literature kinetic models are not able to predict shock tube data with reasonable accuracy. Therefore, an improved hightemperature kinetic mechanism is presented here for the oxidation of n-butanol in shock tubes. The mechanism is based on the published Sarathy et al. 2012 [1] mechanism. This study reinforces the strategy of chemical kinetic model development using a comprehensive set of reaction pathways with reaction rate rules based on expert knowledge. We demonstrate that a model for n-butanol oxidation can be modified only slightly to better predict a new set of experimental data while also improving predictive capabilities at other combustion relevant conditions. Discussions are presented on the validity of the proposed mechanism against recent shock tube experiments
Jet Fuel Thermal Stability Investigations using Ellipsometry
No full textEllipsometry is an optical technique used to measure the thickness of thin films. This technique was used to measure the thickness of deposits created by heated jet fuel, specifically Sasol IPK on stainless steel tubes. A new amorphous model was used to iteratively determine the film thickness. This method was found to be repeatable, and the thickness of deposit increased with increasing temperature and increasing concentration of naphthalene
Ellipsometric Measurements of the Thermal Stability of Alternative Fuels
No full textThermal stability is an important characteristic of alternative fuels that must be evaluated before they can be used in aviation engines. Thermal stability refers to the degree to which a fuel breaks down when it is heated prior to combustion. This characteristic is of great importance to the effectiveness of the fuel as a coolant and to the engine's combustion performance. The thermal stability of Sasol iso-paraffinic kerosene (IPK), a synthetic alternative to Jet-A, with varying levels of naphthalene has been studied on aluminum and stainless steel substrates at 300–400 °C. This was conducted using a spectroscopic ellipsometer to measure the thickness of deposits left on the heated substrates. Ellipsometry is an optical technique that measures the changes in a light beam's polarization and intensity after it reflects from a thin film to determine the film's physical and optical properties. It was observed that, as would be expected, increasing the temperature minimally increased the deposit thickness for a constant concentration of naphthalene on both substrates. The repeatability of these measurements was verified using multiple trials at identical test conditions. Finally, the effect of increasing the naphthalene concentration at a constant temperature was found to also minimally increase the deposit thickness.</jats:p
Unsteady Rans Simulation of an Enclosed, Turbulent Reacting Methane Jet with the Premixed CMC Method
No full textThe premixed conditional moment closure (CMC) method has been shown to provide the capability to model turbulent, premixed methane flames with detailed chemistry and reasonable runtimes in a RANS environment [1]. Here the premixed CMC method is extended to Unsteady RANS. The new model is validated with the PIV and Raman turbulent, enclosed reacting methane jet data from DLR [2]. The experimental data has a rectangular test section at atmospheric pressure and 573 K with a single inlet jet. A jet velocity of 90 m/s is used with an adiabatic flame temperature of 2,064 K. Contours of major species, temperature and equivalence ratio along with their rms values are provided. The CMC model falls into the class of table lookup turbulent combustion models where the combustion model is solved offline over a range of conditions and stored in a table that is accessed by the CFD code. The scalar dissipation is used to account for the effects of the small scale mixing on the reaction rates. A presumed shape beta function PDF is used to account for the effects of large scale turbulence on the reactions. The unsteady RANS version of the open source CFD code OpenFOAM is used with the PISO algorithm solved with the finite volume method. Velocity, temperature and major species are compared to the experimental data. Once validated, this tool will be useful for designing lean premixed combustors for gas turbines. The results match the experimental data better than the steady RANS of [1] and are able to pick up the unsteadiness of the flame
Pyrolysis of RP-2 and Surrogate Fuels in a Jet Stirred Reactor Coupled with Synchrotron Photo Ionization Mass Spectrometry
No full textCombustion chemistry of real fuels are highly complicated by hundreds of individual chemical components that represent their broad composition spectrum. At the same time, typical speciation techniques are limited by the number of individual compounds which can be detected in a single experiment. In this work, the pyrolysis of RP-2 (a kerosene-based rocket fuel) was investigated in a jet stirred reactor (JSR) coupled with synchrotron photo ionization mass spectrometer (PIMS) at various temperatures (295-541 C) and photon energies (7.9-9.7 eV) at atmospheric pressure. The synchrotron PIMS is a powerful tool to identify and characterize various chemical compounds simultaneously. The mass spectrum signals were presented and the products were identified by comparing mass signal intensity versus photon energy and the corresponding standard photoionization efficiency (PIE) spectrum. The product identification showed that peaks at mass-to-charge-ratio (m/z)=54 is 1,3-butadiene (C4H6) and m/z=66 is 1,3-cyclopentadiene (C5H6). The m/z=68 indicated cyclopentene (C5H8) contribution, m/z=78 was matched with benzene (C6H6) PIE, the peak at m/z=92 confirmed toluene (C7H8), and m/z=106 was in perfect match with Xylene (C8H10). In summary, the dominant product peak is benzene followed by toluene and most peaks in the RP-2 product spectrum are aromatic compounds. The present results indicated the potential of JSR and Synchrotron-PIMS as a tool to identify multiple combustion species in a single experiment to study the kinetics of real fuels
LES Simulation of an Enclosed Turbulent Reacting Methane Jet With the Tabulated Premixed CMC Method
No full textThe Tabulated Premixed Conditional Moment Closure Method (T-PCMC) has been shown to provide the capability to model turbulent, premixed methane flames with detailed chemistry and reasonable runtimes in a RANS environment [1]. Here the premixed conditional moment closure method is extended to Large Eddy Simulation. The new model is validated with the turbulent, enclosed reacting methane backward facing step data from El Banhawy [2]. The experimental data has a rectangular test section at atmospheric pressure and temperature with an inlet velocity of 10.5 m/s and an equivalence ratio of 0.9 for two different step heights. Contours of major species, velocity and temperature are provided. The T-PCMC model falls into the class of table lookup turbulent combustion models where the combustion model is solved offline over a range of conditions and stored in a table that is accessed by the CFD code using three controlling variables; the reaction progress variable, variance and local scalar dissipation rate. The local scalar dissipation is used to account for the affects of the small scale mixing on the reaction rates. A presumed shape beta function PDF is used to account for the effects of large scale turbulence on the reactions. Sub-grid scale models are incorporated for the scalar dissipation and variance. The open source CFD code OpenFOAM is used with the compressible Smagorinsky LES model. Velocity, temperature and major species are compared to the experimental data. Once validated, this low runtime CFD turbulent combustion model will have great utility for designing the next generation of lean premixed gas turbine combustors
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