Turbulence Measurements in a Fan-Stirred Flame Bomb Using Laser Doppler Velocimetry

An ongoing project for the construction of a high-pressure, high-temperature turbulent flame speed vessel is furthered in this study. Prior to this work, a laminar flame bomb apparatus was repurposed as a turbulent flame speed vessel with the addition of four fans. Several impeller prototypes were proposed and tested in a mock model. The turbulence was characterized with PIV. At that time, homogenous and isotropic flow field and negligible mean flow were found at the plane of measurement, but the study was limited to a small area and one fan speed. The turbulence characterization is revisited here with a newly acquired LDV system. The study objectives are to: confirm the PIV measurements with LDV, this time in the actual vessel; expand the interrogation area from a plane to a 3d volume; asses the performance of the impellers at different levels rotational speed, and; provide a more direct assessment of the temporal scale. Basic concepts on the statistical description of turbulence were introduced. The LDV principle of operation and the function of the elements comprising the LDV system were explained. The method developed for the experimentation was presented along with all the relevant parameters and adjustments in the control of the experiment. Two levels of fan speed were chosen to run in the modified turbulent vessel, namely 8,000 and 12,000 rpm. A tridimensional space situated at the center of the vessel was systematically scanned and turbulence statistics were obtained. The results confirmed some of the observations of the PIV, but the extension of the measurements to a tridimensional region also revealed unfavorable characteristics previously missed. The work concludes suggesting improvements for a new design of turbulent flame bomb. In particular a new arrangement of the fans is advised

Study of Turbulent Spherical Flames in a Reconfigurable Fan-Stirred Flame Bomb

Turbulent combustion is a very active and challenging research topic. A spherically expanding flame immersed in a turbulent field is one way to gain fundamental insight on the effect of turbulence in combustion. This kind of experiment is conducted inside a fan-stirred flame bomb, but there is only a handful of these devices around the globe. The list is even shorter if demanding conditions are to be tested, i.e. high pressure, high temperature and intense turbulence. A new fan-stirred flame bomb was designed and built to address this shortage. Existing fan-stirred flame bombs were studied first to learn their salient characteristics. This literature review was then used as guidance in the design of turbulence generation elements. A few options of impellers were explored. The flow field produced by the chosen impeller was measured with Laser Doppler Velocimetry (LDV). A detailed exposition of the vessel engineering ensued. Before turbulent experiments were attempted, a validation of the rig accuracy and worthiness was made. The setup demonstrated excellent repeatability and agreement with benchmarks. Finally, a demonstration of the new apparatus was made by testing a lean mixture of syngas. The experiment matrix using hydrogen and H₂/CO mixtures included three levels of pressure (1, 5, and 10 bar) and three levels of turbulence fluctuation rms (1.4, 2.8, and 5.5 m/s). General trends of the effect of turbulence were in line with expectation, but not enough information was obtained to gain insight on the role of pressure

Study of Turbulent Spherical Flames in a Reconfigurable Fan-Stirred Flame Bomb

Turbulent combustion is a very active and challenging research topic. A spherically expanding flame immersed in a turbulent field is one way to gain fundamental insight on the effect of turbulence in combustion. This kind of experiment is conducted inside a fan-stirred flame bomb, but there is only a handful of these devices around the globe. The list is even shorter if demanding conditions are to be tested, i.e. high pressure, high temperature and intense turbulence. A new fan-stirred flame bomb was designed and built to address this shortage. Existing fan-stirred flame bombs were studied first to learn their salient characteristics. This literature review was then used as guidance in the design of turbulence generation elements. A few options of impellers were explored. The flow field produced by the chosen impeller was measured with Laser Doppler Velocimetry (LDV). A detailed exposition of the vessel engineering ensued. Before turbulent experiments were attempted, a validation of the rig accuracy and worthiness was made. The setup demonstrated excellent repeatability and agreement with benchmarks. Finally, a demonstration of the new apparatus was made by testing a lean mixture of syngas. The experiment matrix using hydrogen and H₂/CO mixtures included three levels of pressure (1, 5, and 10 bar) and three levels of turbulence fluctuation rms (1.4, 2.8, and 5.5 m/s). General trends of the effect of turbulence were in line with expectation, but not enough information was obtained to gain insight on the role of pressure

Graduate Student Research Experience Report

This report includes five session. Project I - Knock quantification Project II - Spark plug and early flame kernel development study in optical chamber Project III - Flame kernel development study of emission certification gasolines and their surrogates Project IV - Spectroscopy Project V - LB

Ignition delay times, laminar flame speeds, and mechanism validation for natural gas/hydrogen blends at elevated pressures

New experimental ignition delay time data measured in both a shock tube and in a rapid compression machine were taken to determine the increase in reactivity due to the addition of hydrogen to mixtures of methane and natural gas. Test conditions were determined using a statistical design of experiments approach which allows the experimenter to probe a wide range of variable factors with a comparatively low number of experimental trials. Experiments were performed at 1, 10, and 30 atm in the temperature range 850-1800 K, at equivalence ratios of 0.3, 0.5, and 1.0 and with dilutions ranging from 72% to 90% by volume. Pure methane- and hydrogen-fueled mixtures were prepared in addition to two synthetic \u27natural gas\u27-fueled mixtures comprising methane, ethane, propane, n-butane and n-pentane, one comprising 81.25/10/5/2.511.25% while the other consisted of 62.5/20/10/5/2.5% C-1/C-2/C-3/C-4/Cs components to encompass a wide range of possible natural gas compositions. A heated, constant-volume combustion vessel was also utilized to experimentally determine laminar flame speed for the same baseline range of fuels. In this test, a parametric sweep of equivalence ratio, 0.7-1.3, was conducted at each condition, and the hydrogen content was varied from 50% to 90% by volume. The initial temperature and pressure varied from 300 to 450 K and 1 to 5 atm, respectively. Flame speed experiments conducted above atmospheric pressure utilized a 1:6 oxygen-to-helium ratio to curb the hydrodynamic and thermal instabilities that arise when conducting laminar flame speed experiments. All experiments were simulated using a detailed chemical kinetic model. Overall good agreement is observed between the simulations and the experimental results. A discussion of the important reactions promoting and inhibiting reactivity is included. (C) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved.This work was supported by Science Foundation Ireland under Grant No. [08/IN1./I2055]. We also acknowledge the support of Alstom Power Ltd. A. Morones was supported by CONANCYT of Mexico and CIDESI, and M. Davis was supported in part by a Graduate Diversity Fellowship from Texas A&M University

An experimental and modeling study of propene oxidation. Part 2: Ignition delay time and flame speed measurements

Journal articleExperimental data obtained in this study (Part II) complement the speciation data presented in Part I, but also offer a basis for extensive facility cross-comparisons for both experimental ignition delay time (IDT) and laminar flame speed (LFS) observables.To improve our understanding of the ignition characteristics of propene, a series of IDT experiments were performed in six different shock tubes and two rapid compression machines (RCMs) under conditions not previously studied. This work is the first of its kind to directly compare ignition in several different shock tubes over a wide range of conditions. For common nominal reaction conditions among these facilities, cross-comparison of shock tube IDTs suggests 20-30% reproducibility (2 sigma) for the IDT observable. The combination of shock tube and RCM data greatly expands the data available for validation of propene oxidation models to higher pressures (2-40 atm) and lower temperatures (750-1750 K).Propene flames were studied at pressures from 1 to 20 atm and unburned gas temperatures of 295-398 K for a range of equivalence ratios and dilutions in different facilities. The present propene-air LFS results at 1 atm were also compared to LFS measurements from the literature. With respect to initial reaction conditions, the present experimental LFS cross-comparison is not as comprehensive as the IDT comparison; however, it still suggests reproducibility limits for the LFS observable. For the LFS results, there was agreement between certain data sets and for certain equivalence ratios (mostly in the lean region), but the remaining discrepancies highlight the need to reduce uncertainties in laminar flame speed experiments amongst different groups and different methods. Moreover, this is the first study to investigate the burning rate characteristics of propene at elevated pressures (>5 atm).IDT and LFS measurements are compared to predictions of the chemical kinetic mechanism presented in Part I and good agreement is observed. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.The Rensselaer group was supported by the U.S. Air Force Office of Scientific Research (Grant No. FA9550-11-1-0261) with Dr. Chiping Li as technical monitor. Work at the University of Connecticut and at Princeton University was supported as part of the Combustion Energy Frontier Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, under Award Number DE-SC0001198. The work at Stanford University was supported by the Air Force Office of Scientific Research through AFOSR Grant No. FA9550-11-1-0217, under the AFRL Integrated Product Team, with Dr. Chiping Li as contract monitor. The work at NUI Galway was kindly supported by Saudi Aramco. The work of KAUST authors was supported by Saudi Aramco under the FUELCOM program.peer-reviewe

An experimental and modeling study of propene oxidation. Part 2: Ignition delay time and flame speed measurements

Journal articleExperimental data obtained in this study (Part II) complement the speciation data presented in Part I, but also offer a basis for extensive facility cross-comparisons for both experimental ignition delay time (IDT) and laminar flame speed (LFS) observables.To improve our understanding of the ignition characteristics of propene, a series of IDT experiments were performed in six different shock tubes and two rapid compression machines (RCMs) under conditions not previously studied. This work is the first of its kind to directly compare ignition in several different shock tubes over a wide range of conditions. For common nominal reaction conditions among these facilities, cross-comparison of shock tube IDTs suggests 20-30% reproducibility (2 sigma) for the IDT observable. The combination of shock tube and RCM data greatly expands the data available for validation of propene oxidation models to higher pressures (2-40 atm) and lower temperatures (750-1750 K).Propene flames were studied at pressures from 1 to 20 atm and unburned gas temperatures of 295-398 K for a range of equivalence ratios and dilutions in different facilities. The present propene-air LFS results at 1 atm were also compared to LFS measurements from the literature. With respect to initial reaction conditions, the present experimental LFS cross-comparison is not as comprehensive as the IDT comparison; however, it still suggests reproducibility limits for the LFS observable. For the LFS results, there was agreement between certain data sets and for certain equivalence ratios (mostly in the lean region), but the remaining discrepancies highlight the need to reduce uncertainties in laminar flame speed experiments amongst different groups and different methods. Moreover, this is the first study to investigate the burning rate characteristics of propene at elevated pressures (>5 atm).IDT and LFS measurements are compared to predictions of the chemical kinetic mechanism presented in Part I and good agreement is observed. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.The Rensselaer group was supported by the U.S. Air Force Office of Scientific Research (Grant No. FA9550-11-1-0261) with Dr. Chiping Li as technical monitor. Work at the University of Connecticut and at Princeton University was supported as part of the Combustion Energy Frontier Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, under Award Number DE-SC0001198. The work at Stanford University was supported by the Air Force Office of Scientific Research through AFOSR Grant No. FA9550-11-1-0217, under the AFRL Integrated Product Team, with Dr. Chiping Li as contract monitor. The work at NUI Galway was kindly supported by Saudi Aramco. The work of KAUST authors was supported by Saudi Aramco under the FUELCOM program