Test Flow Conditions Research Articles

A low-profile wall shear comparator to mount and test surface samples

Accurate measurement of shear stress on a solid surface is a crucial but challenging task in fluid mechanics. Different sensors are usually used for different experimental settings: water channel, wind tunnel, towing tank, watercraft, aircraft, etc. This paper presents a direct shear sensor designed to work for varying test objects and flow conditions. Designed to compare two different sample surfaces, the shear sensor is comprised of two floating elements, whose displacement is proportional to the shear stress they experience, and two optical encoders, which measure the displacements precisely, right under the floating elements. The main plate includes two identical sets of floating elements and flexure beams machined monolithically from a thick piece of metal, allowing displacements in only one in-plane direction. The side-by-side arrangement allows the two floating elements to experience essentially the same flow conditions, regardless of test condition, enabling the comparative sensing. The method of machining these folded-beam flexures, whose width is on the scale of micrometers, while thickness and length are in millimeters and centimeters, respectively, is presented. The main plate is designed with the help of finite element analysis to ensure dynamic response of the floating elements is appropriate for target flow conditions. The utility of the shear sensor is verified in three different flow settings, i.e., water tunnel, boat in open water, and wind tunnel. A miniature underwater camera system is also developed to observe the sample surfaces during testing on a moving object, such as a boat.

Evaluation of Test Time and Flow Conditions for 35 mm Square Bore Free-piston Driven Expansion Tube

Evaluation of Test Time and Flow Conditions for 35 mm Square Bore Free-piston Driven Expansion Tube

Mitigating tip vortex cavitation by a flexible trailing thread

Tip Vortex Cavitation (TVC) is a major issue in design and operation of axial hydraulic machines. We investigate the capacity of a flexible trailing thread in alleviating TVC by analyzing the flow-induced motion. For this purpose, a nylon thread with three diameters is cut in various lengths and attached to the tip of an elliptical hydrofoil. The selected threads are flexible enough to become unstable and start to flutter under almost all the tested flow conditions. Due to the vortical flow, an oscillating thread is forced to spiral around the vortex axis. The resulting rotational motion is shown to decelerate the axial velocity in and around the vortex core via two possible mechanisms: first by exerting a local drag and taking energy from the flow and second by increasing the flow fluctuations and turbulent mixing. Our results reveal that a thread becomes more effective in TVC suppression when it is comparable in size with the viscous core of the tip vortex. In fact, a sufficiently thick thread may be sucked into the vortex core under the effect of the pressure field. This results in the hereby-called “whipping” motion that consists of the quasiperiodic coincidence of a part of the thread and the tip vortex axis close to the root. Compared with the rotational motion, the whipping motion is found superior in mitigating TVC. We propose a model that predicts that whipping motion, in contrast to rotational motion, could lead to viscous core thickening, which is validated by the velocity measurements.

Experimental Investigation of the Vertical Upward Single- and Two-Phase Flow Pressure Drops Through Gate and Ball Valves

Abstract This paper presents an experimental investigation of the pressure drop (DP) through valves in vertical upward flows. Experiments were carried out using a 1¼″ (DN 32) ball and gate valve. Five opening areas have been investigated from fully open to the nearly fully closed valve, using air with a superficial velocity of 0–3.5 m/s and water 0.05–0.91 m/s. These ranges cover single-phase and the bubbly, slug and churn two-phase flow regimes. It was found that for the single-phase flow experiments, the valve coefficient increases with the valve opening and is the same, in both valves, for the openings smaller than 40%. The single-phase pressure drop increases with the liquid flowrate and decreases with the opening area. The two-phase flow pressure drop was found considerably increased by reducing the opening area for both valves. It reaches its maximum values at 20% opening for the ball valve and 19% opening for the gate valve. It was also inferred that at fully opening condition, the two-phase flow multiplier, for both valves, has been found close to unity for most of the tested flow conditions. For 40 and 20% valve openings the two-phase multiplier decreases in the power-law with liquid holdup for the studied flow conditions. Models proposed originally for evaluating the pressure drop through an orifice in single-phase and two-phase flows were also applied and assessed in the present experimental data.

Flow Control in Supersonic-Cavity-Based Airflow by Quasi-Direct-Current Electric Discharge

This experimental study examines flow control authority of a quasi-DC (Q-DC) electric discharge in a cavity-based supersonic flow. Testing was performed with Mach 2 airflow using the Research Cell 19 facility at the U.S. Air Force Research Laboratory while varying pressure (), temperature (), gaseous fuel-injection rate [ standard L/min (SLPM)], and power of the electric discharge (). Schlieren imaging and pressure sensors were used to study changes to the flowfield and wall pressure distribution over the test section. The Q-DC electric discharge generates a shock wave that impinges on a rear-facing cavity and increases the pressure throughout the cavity up to 5%. A gas was injected upstream of the cavity to represent fuel injection in a scramjet engine. The flowfield changes due to the Q-DC discharge interaction with the fuel-related bow-shock wave, and shifts the shock train upstream. For injection rates of SLPM, the Q-DC discharge shifts the bow-shock reflection forward to impinge the cavity, thus showing a synergistic effect of the Q-DC discharge and the upstream injection. The maximum relative pressure increase during Q-DC operation with injection was . The control effectiveness parameter was defined and is approximately constant across the tested flow conditions.

Impact of Blockage Ratio on Thermal Performance of Delta-Winglet Vortex Generators

The impact of double-sided delta-winglet tape (DWTs) inserts on convective heat transfer and friction behaviors in a tube was experimentally investigated. Three DWTs with ratios of winglet-height (b) to inner tube diameter (di) called blockage ratio (Rb) of 0.28, 0.35 and 0.42 were tested and their performance was compared to that of a longitudinal strip and plain tube under similar test flow conditions. Experiments were conducted over a wide range of flow rates, 3.35 × 10−5–8.33 × 10−5 m3/s, which correspond to 5500 ≤ Reynolds number (Re) ≤ 14,500 in the 14.3 mm i.d. tube. The results revealed that using DWTs dramatically increased the Nusselt number (Nu) by as much as 364.3% and the friction factor (f) by 15.5 times compared with those of a plain tube. Thermal performance (η) increased with a corresponding increase in Rb. The highest thermal performance (η) obtained was 1.4. Showing a notable improvement on the thermal performance of the system, DWTs are proposed as a favorable insert device.

Fundamental Study on Operational Parameters of Diaphragmless Shock Tube

This paper shows influences of initial conditions on a diaphragmless shock tube operation. This facility consists of a driver tube, a driven tube and a damp tank. The driver tube has a circular cross section with diameter of 150 mm and the driven tube, a rectangular cross section (60 mm x 150 mm). The shock tube is operated by using a quick-opening pneumatic piston instead of a diaphragm. For the operation, pressure inside the pneumatic piston (piston pressure) is quickly released by opening a solenoid valve. In this paper, the initial piston pressure was chosen as a parameter to investigate effects on test flow conditions created by the shock tube. As a result, it was found that when the piston pressure at initial condition is large, piston pressure decreased more rapidly than that obtained for a small piston pressure condition, regardless of the pressure ratio of driver and the driven tube. In the condition of a constant initial operational pressure ratio and a different piston pressure, the shock Mach number was almost constant.

Study of effects of blend of plant seed oils on wax deposition tendencies of Nigerian waxy crude oil

Paraffin wax deposition has been a reoccurring problem in transportation of waxy crude oil in the oil industry. Chemical treatment had been the most convenient and economical method for tackling this problem. This paper considered the study on effects of blends of plant seed oils on wax deposition tendencies of Nigerian waxy crude oil. Three waxy crude oil samples obtained from Niger Delta region of Nigeria were characterized to determine their wax deposition tendencies, pour point, American Petroleum Institute gravity (APIg), wax content and viscosity using standard methods. The impacts of the blend of Jatropha seed oil (JSO) and castor seed oil (CSO) on the wax deposition tendencies of the crude oil samples were determined both in cold finger test and under a dynamic flow. The results obtained showed that blend of castor seed oil with 40% Jatropha seed oil reduced the wax deposition tendencies of the crude oil samples appreciably both in cold finger test and dynamic flow condition. The blend of CSO with 40% JSO gave optimum positive impacts on the pour point and wax deposition tendencies of the waxy crude oils in cold finger tests. The paraffin inhibition efficiency (PIE) attained under this condition was minimum of 79.1% for the crude oil samples at concentration of 0.1%v/v of additive with crude oil. Dynamic flow test using the optimum blend seed oil confirmed that the seed oils performed favourably as wax deposition inhibitor and flow improver at low temperatures and low concentrations of 0.10% additive to crude oil. It is recommended that blend of non-edible CSO and JSO be considered for usage as wax deposition inhibitor and flow improver in the Nigeria oil industry.

X3 expansion tube driver gas spectroscopy and temperature measurements

The University of Queensland’s X3 facility is a large, free-piston driven expansion tube used for super-orbital and high Mach number scramjet aerothermodynamic studies. During recent development of new scramjet test flow conditions, experimentally measured shock speeds were found to be significantly lower than that predicted by initial driver performance calculations. These calculations were based on ideal, isentropic compression of the driver gas and indicated that loss mechanisms, not accounted for in the preliminary analysis, were significant. The critical determinant of shock speed is peak driver gas sound speed, which for a given gas composition depends on the peak driver gas temperature. This temperature may be inaccurately estimated if an incorrect fill temperature is assumed, or if heat losses during driver gas compression are significant but not accounted for. For this study, the ideal predicted peak temperature was 3750 K, without accounting for losses. However, a much lower driver temperature of 2400 K is suggested based on measured experimental shock speeds. This study aimed to measure initial and peak driver gas temperatures for a representative X3 operating condition. Examination of the transient temperatures of the driver gas and compression tube steel wall during the initial fill process showed that once the filling process was complete, the steady-state driver gas temperature closely matched the tube wall temperature. Therefore, while assuming the gas is initially at the ambient laboratory temperature is not a significant source of error, it can be entirely mitigated by simply monitoring tube wall temperature. Optical emission spectroscopy was used to determine the driver gas spectra after diaphragm rupture; the driver gas emission spectrum exhibited a significant continuum radiation component, with prominent spectral lines attributed to contamination of the gas. A graybody approximation of the continuum suggested a peak driver gas temperature of 3200 K; uncertainty associated with the blackbody curve fit is ±100 K. However, work is required to quantify additional sources of uncertainty due to the graybody assumption and the presence of contaminant particles in the driver gas; these are potentially significant. The estimate of the driver gas temperature suggests that driver heat losses are not the dominant contributor to the lower-than-expected shock speeds for X3. Since both the driver temperature and pressure have been measured, investigation of total pressure losses during driver gas expansion across the diaphragm and driver-to-driven tube area change (currently not accounted for) is recommended for future studies as the likely mechanism for the observed performance gap.

Influence of reversing currents on the erosion stability and bed degradation of widely graded grain material

Physical model tests were done in a recirculating flume to investigate the overall erosion stability of widely graded bed material in estuarine and coastal conditions by means of simulating tidal flow conditions with reversing currents. As a result of the reversing flow conditions, previously protected sediment eventually became exposed again, leading to bidirectional displacement processes depending on the flow direction. Furthermore, eroded sediment fractions were slightly finer due to flow in the initially applied direction rather than under the subsequently applied flow in the reverse direction. This indicates higher critical shear stresses, and, thus, erosion stability for the initial flow direction. In comparison to the erosional pattern found when subjecting the material to unidirectional currents, this study finds an even higher erosional stability for sediment fractions smaller than the median (d50) diameter of the parent bed material under reversing current conditions. Overall, no significant damage or failure of the bed was observed after subjecting the material to reversing currents, indicating only a small amount of bed degradation, and, thus, high potential for scour and bed protection under the tested flow conditions.

Impact of Yttrium-90 Microsphere Density, Flow Dynamics, and Administration Technique on Spatial Distribution: Analysis Using an In Vitro Model

PurposeTo investigate material density, flow, and viscosity effects on microsphere distribution within an in vitro model designed to simulate hepatic arteries. Materials and MethodsA vascular flow model was used to compare distribution of glass and resin surrogates in a clinically derived flow range (60–120 mL/min). Blood-mimicking fluid (BMF) composed of glycerol and water (20%–50% vol/vol) was used to simulate a range of blood viscosities. Microsphere distribution was quantified gravimetrically, and injectate solution was dyed to enable quantification by UV spectrophotometry. Microsphere injection rate (5–30 mL/min) and the influence of contrast agent dilution of injection solution (0%–60% vol/vol) were also investigated. ResultsNo significant differences in behavior were observed between the glass and resin surrogate materials under any tested flow conditions (P = .182; n = 144 injections). Microspheres tend to align more consistently with the saline injection solution (r2 = 0.5712; n = 144) compared with total BMF flow distribution (r2 = 0.0104; n = 144). The most predictable injectate distribution (ie, greatest alignment with BMF flow, < 5% variation) was demonstrated with > 10-mL/min injection rates of pure saline solution, although < 20% variation with glass microsphere distribution was observed with injection solution containing as much as 30% contrast medium when injected at > 20 mL/min. ConclusionsGlass and resin yttrium-90 surrogates demonstrated similar distribution in a range of clinically relevant flow conditions, suggesting that microsphere density does not have a significant influence on microsphere distribution. Injection parameters that enhanced the mixing of the spheres with the BMF resulted in the most predictable distribution.

Flow-Control Optimization Maximizes Accuracy of Multiphase-Flow Rate Allocation

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 173873, “Flow-Control Optimization To Maximize the Accuracy of Multiphase-Flow Rate Allocation,” by Reza Malakooti, Khafiz Muradov, and David Davies, Heriot-Watt University, and Alexander Kuznetsov, Weatherford, prepared for the 2015 SPE Bergen One Day Seminar, Bergen, Norway, 22 April. The paper has not been peer reviewed. The value added by intelligent wells (I-wells) derives from real-time reservoir and production-performance monitoring together with zonal downhole flow control. Unfortunately, downhole sensors that directly measure the flow rates and phase cuts required for optimal control of the well’s producing zones are not typically installed. This paper describes an “active” monitoring technique that uses a direct search method to optimize the sequence of interval-control-valve (ICV) positions during a routine multirate test in an I-well. Introduction I-well completions include both downhole flow-control tools and monitoring sensors. Reservoir inflow is controlled by means of passive devices [inflow- control devices (ICDs)], active valves (ICVs), and self-adjusting devices ( autonomous ICDs and autonomous ICVs). Reservoir and well-performance properties should be monitored regularly to support flow- control decisions efficiently. Various physical quantities, including temperature, pressure, flow rate, acoustics, strain, and seismic, are currently measured by electronic, radioactive, and fiber-optic sensors to assist the multiphase-flow rate allocation in I-wells. Producing from only a single well or zone during a test is a common practice. This delivers a single flow-rate value measured at a particular time. However, this approach is inefficient, resulting in lost production and possible difficulties when trying to restart the closed-in wells or zones. A costly production-logging well intervention is a possible alternative; it does provide an inflow rate and a phase-cut profile, but only at a specific time without the possibility of delivering the current phase cut and production rate continuously. The alternative is to use (continuous) passive indirect measurements. Such soft-sensing techniques are used widely in (surface) facilities and process plants where extensive, complex networks of sensors can be implemented relatively easily. They are now being introduced for reservoir and well applications. A multiphase soft sensor consists of (1) an estimation technique, (2) a multiphase-flow model, and (3) the measurements. The multiphase-flow model relates the measurements to the parameters required for the estimation of downhole flow rates. The estimation technique is used to compute these parameters by minimization of the mismatch between measured information and predicted values. Published soft sensors have used both stochastically and deterministically based optimization methods as the estimation technique. The complete paper provides a review of recent research and developments in this field. Soft-sensing techniques are subjected to multiphase-flow-model errors and measurement uncertainties. The latter refers to variance of the values attributed to a measured quantity. For this reason, a new approach is required to overcome the limitation of the passive soft- sensing techniques used to allocate downhole flow rates. To accomplish this goal, an active multiphase-flow-rate soft-sensing method has been developed to design an optimum series of flow tests. The soft sensor obtains the most accurate estimate of the zonal properties by use of the deformed-configuration (DC) method to optimize the flow-test conditions (the ICV flow area in multizone I-wells or the wellhead-choke position for multiple conventional wells). To the authors’ knowledge, this work is the first publication to demonstrate the applicability of the DC optimization method in well soft-sensing problems.

Research on electron density measurements for high enthalpy flows

The high enthalpy shock tunnel, which can provide the high temperature gas conditions for hypersonic flight, is an effective ground facility for the research of reentry problems. It also has the ability of studying real gas effect. The hypersonic test flow condition, with the stagnation enthalpy of 16 MJ/kg and stagnation temperature of 7900 K, was achieved in the JF-10 high enthalpy shock tunnel. The electron density of the flow-field for the 10 degree wedge model was measured using the electrostatic probe, which can obtain sufficient spatial resolution without influencing the flow structure. Results showed that the electrostatic probe has high sensitivity and the spatial electron density can be preferable acquired. The constant bias method can get the dimensionless electron density coupling with the flow field parameters, but the new developed sweeping circuit can get the quantitative value on the basis of effectively reducing the induced noise in the circuit.

逆噴射ジェットによる高エンタルピー流中での空力加熱防御

An experimental investigation on an opposing jet as a thermal protection system in high enthalpy flow has been conducted. The heat flux distributions on a hemispherical-cylindrical test model with and without the opposing jet have been measured in a free-piston shock tunnel. The test gas is air with Mach number of 7.5 or 7.9 with total enthalpy of 20 MJ/kg or 4.8 MJ/kg, respectively. Nitrogen as a coolant gas is injected directly against the test flow through a sonic nozzle at the nose tip of the test model. The effect of alleviating heat loads is investigated by changing total pressure of the opposing jet. A significant reduction of surface heat loads is observed in the case of relatively strong opposing jet under both test flow conditions. The result indicates that thermal protection with the opposing jet is effective in high enthalpy flow. In addition, parameters to characterize the cooling effect of the opposing jet are discussed.

Atomization Characteristics of Camelina-Based Alternative Aviation Fuels Discharging From Dual-Orifice Injector

The atomization characteristics of blends of bioderived camelina hydrogenated renewable jet (HRJ) alternative fuel with conventional aviation kerosene (Jet A-1) discharging into ambient atmospheric air from a dual-orifice atomizer used in aircraft engines are described. The spray tests are conducted in a spray test facility at six different test flow conditions to compare the atomization of alternative fuels with that of Jet A-1. The fuel sprays are characterized in terms of fuel discharge, spray cone angle, drop size distribution, and spray patternation. The measurements of spray drop size distribution are obtained using laser diffraction based Spraytec equipment. The characteristics of fuel discharge and cone angle of alternative fuel sprays do not show any changes from that of Jet A-1 sprays. The characteristics of spray drop size, evaluated in terms of the variation of mean drop size along the spray axis, for the alternative fuel sprays remain unaffected by the variation in fuel properties between the alternative fuels and Jet A-1. The measurements on spray patternation, obtained using a mechanical patternator at a distance 5.1 cm from the atomizer exit, show an enhanced fuel concentration in the vicinity of spray axis region for the alternative fuel sprays discharging from the dual-orifice atomizer.

Effects of Temperature, Humidity and Air Flow on Fungal Growth Rate on Loaded Ventilation Filters

This study compares the fungal growth ratio on loaded ventilation filters under various temperature, relative humidity (RH), and air flow conditions in a controlled laboratory setting. A new full-size commercial building ventilation filter was loaded with malt extract nutrients and conidia of Cladosporium sphaerospermum in an ASHRAE Standard 52.2 filter test facility. Small sections cut from this filter were incubated under the following conditions: constant room temperature and a high RH of 97%; sinusoidal temperature (with an amplitude of 10°C, an average of 23°C, and a period of 24 hr) and a mean RH of 97%; room temperature and step changes between 97% and 75% RH, 97% and 43% RH, and 97% and 11% RH every 12 hr. The biomass on the filter sections was measured using both an elution–culture method and by ergosterol assay immediately after loading and every 2 days up to 10 days after loading. Fungal growth was detected earlier using ergosterol content than with the elution–culture method. A student's t-test indicated that Cladosporium sphaerospermum grew better at the constant room temperature condition than at the sinusoidal temperature condition. By part-time exposure to dry environments, the fungal growth was reduced (75% and 43% RH) or even inhibited (11% RH). Additional loaded filters were installed in the wind tunnel at room temperature and an RH greater than 95% under one of two air flow test conditions: continuous air flow or air flow only 9 hr/day with a flow rate of 0.7 m3/s (filter media velocity 0.15 m/s). Swab tests and a tease mount method were used to detect fungal growth on the filters at day 0, 5, and 10. Fungal growth was detected for both test conditions, which indicates that when temperature and relative humidity are optimum, controlling the air flow alone cannot prevent fungal growth. In real applications where nutrients are less sufficient than in this laboratory study, fungal growth rate may be reduced under the same operating conditions.

Theoretical investigation of air vitiation effects on hydrogen fuelled scramjet performance

The renewed interest in the next generation hypersonic vehicles for commercial and military applications requires combined efforts between multidisciplinary teams involved in computational and experimental work. A common feature of experimental tests, at least for studies on air breathing propulsion systems, is the relatively short test time, limited by the test flow conditions high dynamic pressure and total enthalpy, i.e. 10 MPa at Mach 8 flight conditions. In general, it can be stated that test times decrease as the flow Mach number increases, with changes of several orders of magnitude: a few tens of microseconds for shock tube based tunnels (Mach numbers above 10–15) to tens of seconds or even minutes for the high supersonic range (Mach 4–7.5). In many cases the test flow chemical composition differs from the standard air composition because of pollutants production by the different techniques adopted to increase the flow stagnation enthalpy (combustion products, ionized species, dust, …). The real flow conditions are thus not perfectly duplicated, but only partially simulated in terms of a few main parameters, such as velocity, pressure, and temperature. Few studies have been performed until now, therefore a deep investigation of the air vitiation effects on combustion is mandatory to extrapolate ground to flight correlations. Numerical simulations accounting for the effects of vitiation are also scarce and a characterization of the chemical and turbulence models is still lacking. In this context, CFD simulations of the LAPCAT II MR2 combustor configuration have been performed to provide useful information in terms of efficiency at various vitiation percentages. Theoretical laws and remedies have been proposed for the ground to flight data extrapolation.

Study on spray patterns of gas-centered swirl coaxial (GCSC) injectors in high pressure conditions

Recess ratio and momentum flux ratio are the key parameters in determining spray characteristics and mixing efficiency of the propellants in rocket injectors. In this study, effects of the recess ratio and momentum flux ratio on the spray patterns of gas-centered swirl coaxial (GCSC) injectors have been experimentally investigated through cold flow tests in a high pressure chamber, in which the liquid fuel and gaseous oxidizer are simulated by water and gaseous nitrogen, respectively. By elevating the chamber pressure, the cold flow test conditions are adjusted to match the ratios of momentum flux, density, and velocity between the gas and liquid flows to those of the actual hot-firing conditions. The results showed that the spray patterns change drastically from a wide hollow cone to a narrow solid cone as the gas to liquid momentum flux ratio increases. Also, the injector with the shorter recess needs a higher momentum flux ratio to have a similar spray pattern to that with the longer recess. Based on the measured spray contraction parameters, the critical momentum flux ratio, which determines the near-injector spray pattern as internal or external mixing, correlates with the recess ratio.

One-dimensional interfacial area transport of vertical upward bubbly flow in narrow rectangular channel

The design and safety analysis for miniature heat exchangers, the cooling system of high performance microelectronics, research nuclear reactors, fusion reactors and the cooling system of the spallation neutron source targets requires the knowledge of the gas–liquid two-phase flow in a narrow rectangular channel. In this study, flow measurements of vertical upward air–water flows in a narrow rectangular channel with the gap of 0.993mm and the width of 40.0mm were performed at seven axial locations by using the imaging processing technique. The local frictional pressure loss gradients were also measured by a differential pressure cell. In the experiment, the superficial liquid velocity and the void fraction ranged from 0.214m/s to 2.08m/s and from 3.92% to 42.6%, respectively. The developing two-phase flow was characterized by the significant axial changes of the local flow parameters due to the bubble coalescence and breakup in the tested flow conditions. The existing two-phase frictional multiplier correlations such as Chisholm (1967), Mishima et al. (1993) and Lee and Lee (2001) were verified to give a good prediction for the measured two-phase frictional multiplier. The predictions of the drift-flux model with the rectangular channel distribution parameter correlation of Ishii (1977) and several existing drift velocity correlations of Ishii (1977), Hibiki and Ishii (2003) and Jones and Zuber (1979) agreed well with the measured void fractions and gas velocities. The interfacial area concentration (IAC) model of Hibiki and Ishii (2002) was modified by taking the channel width as the system length scale and the modified IAC model could predict the IAC and Sauter mean diameter acceptably.

Three-Dimensional Fluorescence Spectra of Thermally Stressed Commercial Jet A-1 Aviation Fuel in the Autoxidative Regime

In this study, the thermal oxidative stability of a kerosene-type Jet A-1 commercial aviation fuel has been investigated using a three-dimensional (3D) excitation/emission matrix fluorescence (EEMF) method. The fuel was thermally stressed in flow test conditions over a range of temperatures in the autoxidative regime. To determine the effect of dissolved oxygen on aviation fuel thermal stability, the measurements were conducted for both air-saturated and fully deoxygenated fuel samples. The increase in the fuel temperature results in a large red shift of the fluorescence signals for the air-saturated fuel; however, fully deoxygenated fuel showed no difference in the fluorescence spectra with respect to neat fuel. The observed increase in the emission wavelengths of the collected spectra may be attributed to the formation of high-molecular-mass compounds within the liquid fuel. These species are formed as a consequence of the chemical reactions activated during the thermal stressing process. The use of 3D ...