Core Nozzle Research Articles

Installation aerodynamics of civil aero-engine exhaust systems

Without careful consideration of aerodynamic installation effects on exhaust system performance the projected benefits of high bypass ratio engines may not be achievable. This work presents a computational study of propulsion system integration in order to quantify the effect that aircraft installation has on the aerodynamic performance of separate-jet aero-engine exhaust systems. Within this study the sensitivity of exhaust nozzle performance metrics to aircraft incidence and under wing position were investigated for two engines of different specific thrust. Upon installation, thrust generation was found to be beneficial or detrimental relative to an isolated engine depending on the position of the engine relative to the wing leading edge. The dominant installation effect was observed on the exhaust afterbodies and, over the range of engine positions investigated at cruise conditions, the installed modified velocity coefficient was shown to vary up to 1% relative to an isolated engine. Furthermore, due to variations in the core nozzle mass flow rate by up to 10% relative to an isolated engine, it is concluded that aerodynamic installation effects need to be taken into consideration when sizing the core nozzle in order to ensure engine operability.

An investigation of the interactions between impulsively started and steady supersonic jets

The ignition of the solid rocket booster strap-on and the following IOP wave have a severe influence on the dynamic as well as the acoustic loads experienced by a launch vehicle during lift-off. The jet from the strap-on interacts with the core jet and its established flow over the jet blast deflector, influencing the acoustic field experienced by the launch vehicle. The existing literature provides very little understanding of such interactions. This work investigates the interaction between the jet from SRB and the core, by simulating them with an impulsively started supersonic jet in close proximity to another established jet. While the flow for the core nozzle was allowed directly from the settling chamber, a novel approach using a quick opening valve was used for initiating the flow through the strap-on nozzle. The evolution of a strong shock wave emanating from the strap-on nozzle and the ensuing vortex ring, their interaction with the core jet flow, etc., was captured using schlieren. The results document the fluid dynamic interactions such as the evolution of a strong shock wave emanating from the strap-on nozzle and the ensuing vortex ring, their interaction with the core jet flow, etc., using flow visualizations and acoustic measurements.

Efficacy evaluation of horticultural oil based thermotherapy for pear psylla management

The goal of this study was to improve techniques for pear psylla, Cacopsylla pyricola (Föerster) control, one of the major pests in pear orchards worldwide and in the United States. Mortality of adult pear psylla was determined after its exposure to horticultural oil (HO) combined with high temperature (thermotherapy) treatments. A laboratory–scale application technology unit was developed to apply HO–based thermotherapy. Spray treatments included four variables namely heat–condition (i.e., heat and no–heat), HO concentration (i.e., 0.5 and 1.0%), nozzle types (i.e., N1: Conejet nozzle, N2: D2/DC13 disc–core nozzle) and application pressure (i.e., 344.7 [50] and 689.5 [100] kPa [psi]). Each treatment was replicated four times on pear psylla bioassays. Mortality was evaluated at 3, 6, 12, 24 and 48 h after spray application. HO combined with thermotherapy achieved as high as 100% pear psylla mortality during early hours after spray application. The overall mean pear psylla mortality using HO under heat condition (63.7 ± 2.4% [mean ± std. error]) was significantly higher compared to no–heat condition (43.6 ± 1.8%). Higher HO concentration (i.e., 1.0%) under heat condition had significantly higher mortality (60.2 ± 2.3%) compared to similar applications at lower concentration (47.1 ± 2.0%). Pear psylla mortality was significantly affected by nozzle type under heat conditions, and nozzle N1 (with comparatively higher spray coverage on water sensitive papers) had significantly higher (74.4 ± 3.1%) pear psylla mortality compared to nozzle N2 (52.9 ± 3.3%). The interaction between thermotherapy and each of the HO concentrations and nozzles on psylla mortality was significant at α = 0.05. Overall, HO combined with thermotherapy caused a rapid kill of pear psylla. Future field studies are warranted to evaluate efficacy of HO–based thermotherapy at reduced HO concentrations and pertinent effects on smothering of eggs and pear psylla mortality.

Optimizing Separate Exhaust Turbofans for Cruise Specific Fuel Consumption

Cruise specific fuel consumption (SFC) of turbofan engines is a key metric for increasing airline profitability and for reducing CO2 emissions. Although increasing design bypass ratio (BPR) of separate exhaust turbofan configurations improves cruise SFC, further improvements can be obtained with online control actuated variable geometry modulations of bypass nozzle throat area, core nozzle throat area, and compressor variable vanes (CVV/CVG). The scope of this paper is to show only the benefits possible, and the process used in determining those benefits, and not to suggest any particular control algorithm for searching the best combination of the control effectors. A parametric cycle study indicated that the effector modulations could increase the cruise BPR, core efficiency, transmission efficiency, propulsive efficiency, and ideal velocity ratio resulting in a cruise SFC improvement of as much as 2.6% depending upon the engine configuration. The changes in these metrics with control effector variations will be presented. Scheduling of CVV is already possible in legacy digital controls; perturbation to this schedule and modulation of nozzle areas should be explored in light of the low bandwidth requirements at steady-state cruise conditions.

Fluidic thrust vectoring using transverse jet injection in a converging nozzle with aft-deck

This paper summarizes the results of an experimental study carried out to implement fluidic thrust vectoring in yaw direction using transverse jet injection in a converging nozzle with an elliptic exit and triangular shaped aft-deck. The study was restricted to low subsonic flow regime typical for Unmanned Aerial Vehicle (UAV) applications. The momentum of the core nozzle flow was kept constant while varying the momentum of the secondary-jet. The surface pressure distribution, exhaust jet velocity field and thrust were measured. Secondary-jet injection was found to create a virtual exit plane at an angle to the stream wise direction of the nozzle flow resulting in the turning of the core-jet away from the injection slot and turning the direction of thrust (termed vectored thrust). The angle of the vectoring was found to increase with increase in momentum of the secondary-jet but only up to a certain maximum. The vectoring was found to increase the static pressure at the nozzle inlet, which is a very crucial observation in this study as it is directly related to engine performance. The secondary-jet injection was found to reduce the width of the core-jet and the magnitude of this reduction was found to increase in stream wise direction and also increase with increase in the momentum of the secondary-jet. Core flow behavior was different in the region with aft-deck compared to region without aft-deck. Jet spreading was expedited by the secondary-jet and aft-deck. Multiple shear layers were present in the flow with the secondary-jet switched on, which were otherwise absent. Secondary-jet injection was found to result in the formation of vortices with axes oriented along the direction of the secondary-jet at the injection slot and these vortices convect downstream with the core flow. These vortices were found to excite the shear layer, resulting in better jet mixing and hence augment the mass entrainment by the core flow.

A novel cell-printing method and its application to hepatogenic differentiation of human adipose stem cell-embedded mesh structures.

We report a cell-dispensing technique, using a core–shell nozzle and an absorbent dispensing stage to form cell-embedded struts. In the shell of the nozzle, a cross-linking agent flowed continuously onto the surface of the dispensed bioink in the core nozzle, so that the bioink struts were rapidly gelled, and any remnant cross-linking solution during the process was rapidly absorbed into the working stage, resulting in high cell-viability in the bioink strut and stable formation of a three-dimensional mesh structure. The cell-printing conditions were optimized by manipulating the process conditions to obtain high mechanical stability and high cell viability. The cell density was 1 × 107 mL−1, which was achieved using a 3-wt% solution of alginate in phosphate-buffered saline, a mass fraction of 1.2 wt% of CaCl2 flowing in the shell nozzle with a fixed flow rate of 0.08 mL min−1, and a translation velocity of the printing nozzle of 10 mm s−1. To demonstrate the applicability of the technique, preosteoblasts and human adipose stem cells (hASCs) were used to obtain cell-laden structures with multi-layer porous mesh structures. The fabricated cell-laden mesh structures exhibited reasonable initial cell viabilities for preosteoblasts (93%) and hASCs (92%), and hepatogenic differentiation of hASC was successfully achieved.

Core-Liquid-Induced Transition from Coaxial Electrospray to Electrospinning of Low-Viscosity Poly(lactide-co-glycolide) Sheath Solution

Co-electrospinning has demonstrated that polymer solutions below the entanglement concentration can be made into fibers as an encapsulated core in an electrospinnable sheath solution containing a carrier/template polymer. The carrier polymer may require removal at a later stage. This work shows for the first time that without increasing the polymer concentration/molecular weight or needing a template polymer, simply infusing a liquid in the core nozzle can cause the sheath polymer solution (viscosity <20 mPa s) to electrospin instead of electrospray in a coaxial electrified jet. Different from coelectrospinning, the core liquid can be a common solvent such as water and does not require a readily electrospinnable carrier polymer. The process was not limited to one core liquid system; infusing solvents and nonsolvents with different properties in the core generated either beaded fibers or continuous fibers from the sheath solution. The process of fiber formation instead of particle breakup was attributed to the relaxation time of the elastic polymer sheath solution becoming longer than the growth rate of the Rayleigh instability in the compound jet upon the infusion of a second solvent in the core. Key parameters of the process included high surface tension of the core liquid (e.g., water and glycerol), high interfacial tension between the core and the sheath liquids, and electrohydrodynamic operating parameters such as flow rate and applied voltage. Given that charge was transferred from the sheath solution to the core liquid, differences in the dielectric constant and electrical conductivity of the core liquids showed little influence on the process. Fibers also formed irrespective of the miscibility and solubility of the solvent, though in the case of a nonsolvent, a lower miscibility was desirable to minimize polymer precipitation at the core–sheath interface. The process was investigated using poly(lactide-co-glycolide) as a model system, with polycaprolactone and polymethylsilsesquioxane systems presented as two additional examples. This work documents new roles of solvents in coaxial electrohydrodynamic processes and presents a useful method to obtain micro- and nanofibers from low-viscosity solutions without using a template polymer.

New electrospinning nozzle to reduce jet instability and its application to manufacture of multi-layered nanofibers.

A new nozzle system for the efficient production of multi-layered nanofibers through electrospinning is reported. Developed a decade ago, the commonly used coaxial nozzle system consisting of two concentric cylindrical needles has remained unchanged, despite recent advances in multi-layered, multi-functional nanofibers. Here, we demonstrate a core-cut nozzle system, in which the exit pipe of the core nozzle is removed such that the core fluid can form an envelope inside the shell solution. This configuration effectively improves the coaxial electrospinning behavior of two fluids and significantly reduces the jet instability, which was proved by finite element simulation. The proposed electrospinning nozzle system was then used to fabricate bi- and tri-layered carbon nanofibers.

The application of hybrid RANS/ILES approach for the investigation of the effect of nozzle geometry and mode of efflux on the characteristics of turbulence of exhaust jets

The efficient hybrid RANS/ILES approach is used for the investigation of the effect of nozzle geometry and parameters of flow at the nozzle exit section on the characteristics of turbulence in the exhaust jet. The calculations are performed for nozzles of different types such as conical and chevron nozzles and the nozzle of double-flow turbojet engine (TJE) with chevrons on the core nozzle. The effect of the foregoing parameters on the level of fluctuations of velocity and pressure in the investigated jets is demonstrated. The effect of off-design mode of efflux on the parameters of turbulence in the jet is investigated under conditions of supersonic efflux of the jet. The effect of misalignment of the core and fan nozzles on the flow in the jet is considered for the nozzle of double-flow TJE. Grids containing about 106 cells are used for the calculations. The accuracy of the results is confirmed by comparison with the known experimental data.

Turbulence Measurements of Separate-Flow Nozzles with Pylon Interaction Using Particle Image Velocimetry

Particle image velocimetry measurements for separate-flow nozzles with bypass ratio five have recently been obtained in the NASA Langley Jet Noise Laboratory. The six configurations tested include a baseline configuration with round core and fan nozzles, an eight-chevron core nozzle at two different clocking positions, and repeats of these configurations with a pylon included. One run condition representative of takeoff was investigated for all cases. The unsteady flowfield measurements complement recent computational, acoustic, and mean flowfield studies performed at NASA Langley for the same nozzle configurations and run condition. The baseline configuration measurements show good agreement with existing mean and turbulent flowfield data. Nonetheless, the baseline configuration turbulence profile indicates an asymmetric flowfield, despite careful attention to concentricity. The presence of the pylon increases the upper shear layer turbulence levels while simultaneously decreasing the turbulence levels in the lower shear layer. In addition, a slightly shorter potential core length is observed with the addition of the pylon. Finally, comparisons of computational results with current measurements are favorable for mean flow, slightly overpredicted for Reynolds shear stress, and underpredicted for Reynolds normal stress components.

Experimental Study of Droplet Transport Time between Nozzles and Target

Variable rate pesticide application holds great potential in precision farming with high efficiency of pesticide use and minimised environmental contamination, while application efficiency depends strongly on the accuracy of the discharge rate on the target area. This study is an initial part of the development of a variable rate sprayer to quantify droplet travel time with four types of nozzle at four different liquid pressures and at four forward speeds using a moisture sensor and laser technology. Performance of droplet deposition at different instants was investigated by moving belt and fluorescent tracer. Sprayer forward speed had a significant influence on droplet transport time, while liquid pressure had less influence. Sample positions chosen at below the nozzle and midway between two nozzles on the boom produced little difference in droplet transport time. Dynamic deposition results indicated that accumulated deposition at the peak point is 37·1%, 33·6% and 29·2% of the total deposition with a flat fan nozzle, low drift nozzle, and hollow core nozzle, respectively.

Evolution of a compound droplet attached to a core-shell nozzle under the action of a strong electric field

The shape evolution of small compound droplets at the exit of a core-shell system in the presence of a sufficiently strong electric field is studied both experimentally and theoretically. It is shown that the jetting effect at the tip of the shell nozzle does not necessarily cause entrainment of the core fluid, in which case the co-electrospinning process fails to produce core-shell nanofibers. The remedy lies in extending the core nozzle outside its shell counterpart by about half the radius of the latter. The results also show that the free charges migrate very rapidly from both fluids and their interface to the free surface of the shell. This reflects the fact that most of the prejetting evolution of the droplet can be effectively described in terms of the perfect conductor model, even though the fluids can be characterized as leaky dielectrics. The stress level at the core-shell interface is of the order of 5×103g∕(cms2), the relevant value in assessing the viability of viruses, bacteria, DNA molecules, drugs, enzymes, chromophores, and proteins to be encapsulated in nanofibers via co-electrospinning.

Acoustics and Thrust of Quiet Separate-Flow High-Bypass-Ratio Nozzles

TheNASAGlennResearchCenterrecentlycompletedanexperimentalstudytoreducethejetnoisefrommodern turbofan engines. The study concentrated on exhaust nozzle designs for high-bypass-ratio engines. These designs modie ed the core and fan nozzles individually and simultaneously. In comparison with chevrons, tabs appeared to be an inefe cient method for reducing jet noise. Data trends show that interaction between fan e ow and the core cowl could strongly impact noise and cruise performance irrespective of the mixing device installed. The study demonstrates that modie cations of the core nozzle are generally more advantageous than of the fan nozzle. Even greater advantage in noise reduction and associated cruise thrust penalties is demonstrated through simultaneous modie cation of both nozzles. Thebestnozzledesign had a 0.06% cruisethrustlossand, corrected fortakeoff thrust loss, a 2.7-EPNdB reduction for the effective perceived noise level metric. This design simultaneously employed chevrons on the core and fan nozzles. Last, e ve nozzle cone gurations with cruise thrust loss of less than 0.5% and noise reductions of over 2.5 EPNdB are identie ed as candidates for full-scale engine and e ight demonstrations.

Air Deflector Effects on Aerial Sprays

Air deflectors (Chimavir Air Services, Ltd., Israel) were installed on an agricultural aircraft and tests were run to investigate: (1) the alteration in downwind residue results (drift) due to release height, (2) the influence on droplet sizes conducted with a laser drop size analyzer in a wind tunnel, and (3) the changes in air flow near the spray boom as observed from wind tunnel tests. A turbine-powered monoplane with air defectors was evaluated for spray drift losses and deposit characteristics in a cotton field. Air-burden residue from application heights of 3.0, 4.6, and 6.1 m were investigated using high-volume air samplers along a 610-m sampler line oriented at 23.6 from a 700-m flightline. Spray deposit was measured (concurrent with the downwind airborne drift sampling) from collection of residue on Mylar plastic sheets spaced at 6.1-m intervals from the first air sampler to beyond the flightline. Gas chromatographic analysis was used to measure the concentration of cinnamyl alcohol tracer. Results from air samplers indicated that the 3.0-m release height had significantly (P = 0.05) less airborne drift (2.19 ppm) than the 4.6 m height (9.52 ppm) and 6.1 m height (11.37 ppm). No differences (P = 0.05) in fallout deposit levels were detected, although the 4.6 m height tended to have a higher level of deposit (6.06 ppm) than the 3.0 m height (4.29 ppm) and the 6.1 m height (4.62 ppm). Spray droplet sizes produced in a wind tunnel with and without a deflector were examined for a custom-sized RF 25 fan nozzle (3.06 L/min at 276 kPa, Delavan-Delta, Inc., Lexington, Tenn.) and a D6-46 disk and core nozzle (Spraying Systems Co., Wheaton, Ill.). Both nozzles were oriented 45 down and back with airstream velocities of 60 and 75 m/s. Water-soluble formulations were examined and included (1) cinnamyl alcohol, (2) bifenthrin, and (3) water. Overall mean droplet sizes (Malvern) with the deflector were 235 mm, whereas without the deflector they were 182 mm. The downwash of air around the deflector was quantified in terms of mean, steady-state air velocity and direction. Measurement points were selected on a two-dimensional grid that ran longitudinally with the axis of the wind tunnel. Air was deflected to an angle of 50 from horizontal. A 54 m/s air flow was decelerated to 40 m/s behind the deflector.

Use of swirl for flow control in propulsion nozzles

In certain off-design conditions it is desirable to vary the effective area of turbofan propulsion nozzles, e.g., to aid component matching or to reduce fan noise on approach. It has been suggested that the mass flux reductions associated with swirl could be used to achieve such variations. This paper addresses the questions of whether swirl can achieve the required mass flux reductions and whether this can be done with minimal thrust losses. A quasicylindrical theory is used to analyze the swirling flow, and comparisons are made with variablearea nozzles for specific case studies. For a low-specific thrust engine of high bypass ratio (BPR = 12) the required fan nozzle mass flux reduction cannot be achieved using swirl, and in any case, swirl gives a far faster rate of decay of thrust with fan nozzle mass flux than does a variable-area nozzle. For a ducted fan of BPR -4, a 10% reduction in core nozzle mass flux can be achieved with swirl for slightly less thrust loss than with a variable-area nozzle. The swirl profile, however, needs to be carefully optimized.

Downwind Transport of Aerially Applied Sprays Under High Temperature, High Humidity Conditions

Residues of tracer salts, as applied by two aerial spray systems, were measured downwind under high temperature, high humidity conditions. The lowest levels of drift were measured from a D8-jet nozzle that produced the largest volume median diameter (Dv.5). The jet nozzle (disc orifice 8/64 in diameter, no core), directed at 0 with the airstream, produced a Dv.5 (533 m) appropriate for herbicide applications. The hollow cone disc and core nozzle, D8-46 directed at 0 to the airstream produced a Dv.5 of 374 m but with a wide drop size range. The Micronair had the narrowest drop size range and the smallest Dv.5 (264 m).

Chemigated and Aerially-Applied Insecticides for Control of Western Bean Cutworm, Hale (Bonny Dam), Co, 1985

Abstract Treatments were applied on 26 Jul ‘85 to pretassel corn. Chemigated treatments were applied through a Zimmatic sprinkler with Senninger 360-degree low pressure drop nozzles with a Pulsafeeder Hydracone R-l pump. Aerial treatments were applied with a Peiper A25 (Hutchinson Wing) aircraft calibrated to deliver 2 gal/acre in a 45-ft swath at 30 psi through 23 D 8-45 core nozzles. Treatments were evaluated on 21 Aug ‘85 by counting the number of live larvae in 4 groups of 25 ears per treatment.

Spray Additive Deposition Study 1985

Abstract Tests were conducted in Northeast LA to determine the influence of Triton CS-7 on spray coverage with aerial application. Droplet density per cm2 was used to evaluate coverage. Deposition in the cotton canopy was evaluated by placing fifteen 48-inch high deposit card holders in each of two 20-acre test plots in cotton 50-60 inches tall, planted on 40-inch rows. The holders were placed in the drill, arranged in a straight line on every 3rd row, making a 140-ft perpendicular collection area to the direction of the aircraft. Krome kote cards were attached at ground level, 20 inches mid-canopy, and 48 inches above ground. A 0.33% Agmark P2 dye was added to the treatments for a droplet marker. Deposition analysis for a clear open area, was made at the airport. Cards were placed at ground level, 2 ft on center from 80 ft right and left of the flight line for swath testing. Swath tests were made with and without Triton CS-7. The test airplane was an Ag Cat A (39 ft 1 inch Wingspan, 600HP) equipped with 22 D6-46 and 23 D-46 disc and core nozzles that were turned straight down and operated at 20 psi. Computed finished spray rate was 2.25 gal/acre, airspeed 115 mph. The swath tests and canopy tests were made 8 Aug. Insecticide performance data were collected from the test field during regular season applications made on 12 Jul, 17 Jul, 20 Jul, and 8 Aug.

Control of Grasshoppers on Alfalfa, Akron, Co, 1984

Abstract Plots were 2 swaths in width, replicated 4 times in a randomized complete block design. Treatments were made on 12 Jul ’84 to 2-4 inch alfalfa with a Peiper PA25 aircraft fitted with Hutchison wings and 23 T-Jet Hollow cone #8-45 core nozzles. One gal/acre treatments were applied at 28 psi and 2 gal/acre treatments were applied at 24 psi. Grasshoppers counts were made with standard USDA survey techniques.

Control of Grasshoppers on Range, Akron, Co, 1984

Abstract Plots were 2 swaths in width, replicated 4 times in a randomized complete block design. Treatments were made on 12 Jul ‘84, with a Peiper PA25 aircraft fitted with Hutchison wings and 23 T-Jet Hollow cone #8–45 core nozzles calibrated to apply 1 gal/acre at 28 psi. Grasshopper counts were made with standard USDA survey techniques.