Feed Arm Research Articles

Experimental and quantum chemical investigation into the nature of jet fuel deposition on surfaces

Chemical analysis of undissolved deposits formed on a simulated jet fuel burner feed arm suggest a higher concentration of oxidized polar fuel species at the wall-deposit interface. To investigate the nature of their adsorption, the adsorption energies of various jet fuel species classes were calculated using plane-wave DFT methods on two oxide surfaces Fe2O3-(0001) and Cr2O3-(0001), which were chosen to represent a stainless steel surface. A mixed termination approach was chosen to encapsulate the heterogeneous nature of stainless steel surfaces. On metal-terminated Fe2O3 and Cr2O3 surfaces, the order of the absolute adsorption energies was RSO3H > RSO2H > RCOOH > RSH > ROH > RCOH > RH. Dissociative chemisorption was observed for all the acid species, with sulfur acids having a higher absolute adsorption energy on Cr2O3 but carboxylic acids having a higher adsorption energy on Fe2O3. On oxygen-terminated Fe2O3, the order of the absolute adsorption energies was RSO2H > RSR > RSO3H > RSH > ROH > RCOH > RCOOH > RH. On the other hand, for oxygen-terminated Cr2O3, the order of the absolute adsorption energies were RSO2H > RSR > RSH > RSO3H > RCOH > ROH > RCOOH > RH. In contrast to the metal terminated surface, acids do not chemisorb on the oxygen terminated surfaces. Instead, the sulfur acids are found to form surface hydroxyl species from the dissociation of the acidic -OH group. The reactivity of the surfaces followed the general pattern: metal terminated-Fe2O3> metal-terminated Cr2O3, oxygen-terminated Fe2O3≈ Cr2O3. Overall, a combination of experimental and quantum chemical techniques confirmed the theory that sulfur acids are the initial species to deposit on stainless steel.

Compact dielectric impulse radiating antenna with a flat feed arm structure for low‐frequency gain enhancement

AbstractA compact dielectric impulse radiating antenna (IRA) with flat coplanar conical plate (CCP) feed arms was proposed for low‐frequency gain enhancement. An empirical equation was proposed to predict the characteristic impedance of the CCP arms submerged in a dielectric half‐space. The predicted value was used to determine the termination resistors that connect the feed arms to the reflector. Both the dielectric‐filled and conventional air‐filled IRAs were fabricated, and their performances were measured. The gain of the proposed dielectric‐filled IRA is shown to be higher at frequencies lower than 3 GHz, where the diameter of the reflector is one wavelength.

Investigation on oxidation deposition characteristics and its inhibition tactics in aero-engine swirl nozzle

As a hidden danger of modern aircraft, the problem of nozzle carbon deposition must be addressed. Carbon deposition prediction and suppression methods for aviation nozzles still need further study. In this study, fouling experiments of the aero swirl nozzle were conducted to analyze the deposition characteristics of each component, and the deposit distribution of nozzle under different working conditions was predicted by numerical simulation. Finally, the anti-coking effect of the TiN coating on swirl nozzle was evaluated. The results showed that the buoyancy force could lead to an uneven distribution of deposits in the fuel feed arm. High inlet temperature fuel carries more precursors and results in a swirler surface covered with deposits, whereas for low inlet temperature fuel, deposits accumulate on the boss near passages inlet. The reaction species content, local velocity and temperature determined this. The deposition layer on the nozzle orifice surface is the densest owing to the high temperature and oxygen-rich environment. The TiN coating was applied to the inside and outside of the nozzle by chemical vapor deposition (CVD). The coating protection on fuel feed arm and swirler was inconspicuous. However, it exhibited the best anti-coking effect on the orifice surface. In this study, the causes of carbon deposition in swirl nozzles were determined and the protective effect of TiN inert coating was evaluated for the first time.

Electric field effects on thermal oxidation deposition of aviation kerosene

Aiming at solving the problem of carbon deposition in aero-engine fuel nozzles, this study presents a method of arranging cylindrical electrode in fuel feed arm to inhibit thermal oxidation deposition. Based on the electrohydrodynamics (EHD) technique, the effect of electric field on fuel’s original flow, heat transfer and oxidation deposition reaction process was investigated. A 3D mathematical model was established based on the Maxwell, Navier Stokes (NS) and species transport equations. The finite volume method was used for conservative discretization of the governing equations. The oxidation deposition behavior of aviation kerosene in fuel feed arm under different mass flow and voltage conditions was investigated. The results show that, in the absence of electric field, the deposition in the fuel feed arm mainly comes from the surface reaction caused by the diffusion of insoluble precursor (InsolubleAH) from the thermal boundary layer to the wetted wall. The secondary flows generated by the electric field break the original flow and thermal boundary layer, which can reduce the temperature gradient of the fuel near the wall and inhibit the generation of insoluble deposition precursor in the volumetric reaction. Furthermore, driven by electric field force, the mainstream fuel fully cooled the wetted wall thus inhibiting the wall surface reaction. The average deposition rate was reduced up to 30.9%. This study provides a new means of inhibiting oxidation deposition in fuel injection system.

A wideband omnidirectional planar filtenna for 5 GHz WLAN application

This paper presents a wideband planar filtenna based on the filter synthesis technique. The proposed filtenna consists of a third order hairpin line resonator filter coupled with an elliptical antenna. One arm of the last resonator of hairpin line resonator along with the extended feed arm of an antenna constitute an admittance inverter, which provides better integration between filter and antenna. The measured results show that the proposed filtenna exhibits a filtering response with impedance bandwidth of 26.5% (4.19–5.47 GHz), flat passband gain, good selectivity at band edges and omnidirectional radiation pattern well suited for WLAN application.

A Preliminary Plan to Quickly Restore Utility to the Arecibo 305m Telescope

Since the fall of the Arecibo 305[Formula: see text]m telescope platform on 2020 December 1, there has been much discussion of building a new Arecibo telescope or rebuilding the facility that was destroyed. In the collapse, the top of the three platform support towers was sheared off, and the feed arm fell free from the swinging platform and destroyed 25% of the dish. Fortunately, the Control Building, the home of the computers, spectrometers, masers, atomic clocks, 430[Formula: see text]MHz Klystrons, etc., was spared. By replacing the main dish support cables and resurfacing with coarse mesh, the main dish can be repaired as a reflector [Formula: see text] operation. By replacing the damaged aluminum panels to make the dish whole again, RF operations at up to 500[Formula: see text]MHz can be resumed. In this paper, we outline the steps that can be taken to restore High Frequency (HF, 3–30[Formula: see text]MHz) ionospheric heating, 430[Formula: see text]MHz ionospheric incoherent scattering radar, passive radio observations of satellite arcing and pulsars, and to extend the field of regard to 47∘ from the zenith. This would restore and improve much of the utility of the Arecibo dish. Part of this plan involves supporting, positioning and pointing novel point feeds from lightweight football-camera-like cables, strung from the rebuilt tower tops. It is believed that the dish may thus become broadly useful long before replacement facilities can be engineered and constructed.

Design of a Compact Quasi-Self-Complementary UWB-MIMO Antenna with Dual Band-Notched Characteristics for Wireless Communication Applications

ABSTRACT The proposed work contains a quasi-self-complementary (QSC) half-cut flower-shaped ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with dual-band-notch characteristics. The overall size of the antenna is 27 × 39 mm2, which offers impedance bandwidth from 2.67 GHz to 11.7 GHz. The inter-port isolation is more than 15 dB over the FCC defined UWB range of frequencies. A reverse 2-shaped slit is etched off from a flower-shaped patch to reject the interfering WiMAX/C-band (3.28–4.19 GHz), whereas an inverse P-shaped stub is placed near the feed arm a notch at the WLAN band (5.1–6.15 GHz). Further, the performance of the proposed antenna is analysed by comparing the simulated results with the fabricated ones. Moreover, diversity parameters such as envelope correlation coefficient (ECC), channel capacity loss (CLL), mean effective gain (MEG), effective diversity gain (EDG) and total active reflection coefficient (TARC) are computed, which makes the proposed QSC UWB-MIMO antenna a suitable candidate for high-speed wireless applications.

Prediction model development for material removal rate in band sawing using dimensional analysis approach

Bandsawing is an accurate and fast process to cut various raw materials. Material removal rate (MRR) is the important parameter in bandsawing to judge its performance. To the best of knowledge of the author, almost none of the researchers has developed semi empirical model to study combined effect of process, material and machine parameters for bandsawing process. Hence, in the present research work, semi empirical model is developed for MRR using dimensional analysis approach. In this work, Taguchi's technique is used to conduct experiments. As per ANOVA, feed (58%), speed (17.44%) and top arm angle (13.55%) found as significant parameters. The model is formulated as a function of these parameters and validated calculating mean error (0.024), root mean square error (0.029) and percentage average error (6.63%). The model is verified by randomly substituting the values from experiment data set. The predicted results were found in close agreement with the experiment results.

A qualitative numerical study of glucose dynamics in patients with stress hyperglycemia and diabetes receiving intermittent and continuous enteral feeds

Abstract Background Using 12 healthy adults, it was shown that a reduction in mean glucose concentration follows intermittent gastric feeds, not continuous: a desirable result for hospitalized patients. A numerical study comparing glucose dynamics after intermittent gastric and continuous post-pyloric feeds may inform the design of a similar clinical study in the critical care setting. Methods A mathematical model was used to construct a small virtual crossover study comparing intermittent gastric feeds and continuous post-pyloric feeds. The model, validated for eight diabetic patients, produced maximum glucose concentration, mean glucose concentration and glucose concentration standard deviation data. Simulations were repeated after renal insulin clearance was increased by 50%, a common physiologic alteration in critical illness. Five hypothetical patients with stress hyperglycemia also underwent simulation. Results Mean glucose concentration was significantly lower after intermittent gastric feeds in type 1 diabetics and in the stress hyperglycemia patients. Without insulin therapy, intermittent gastric feeds increased maximum glucose concentration more than continuous post-pyloric feeds, and glucose concentration standard deviation was largest after intermittent gastric feeds in all patients. Also, the continuous glucose concentration data suggests that the total amount of insulin required to treat patients with stress hyperglycemia would be least in the intermittent feed arm. Finally, data collection with a continuous glucose-monitoring device might be required to resolve maximum glucose and glucose standard deviation differences between the study arms. Conclusions This is the first examination of glucose dynamics following intermittent gastric feeds in a critical care setting. A small crossover clinical study could demonstrate that patients with stress hyperglycemia require less insulin following intermittent, not continuous, enteric feeds. Preliminary data from a clinical trial is reviewed and is found consistent with the results reported here.

Prediction of growth of jet fuel autoxidative deposits at inner surface of a replicated jet engine burner feed arm

A low thermally stable jet A-1 fuel was heated up to 115 h under engine representative condition in a simulated burner feed arm with cylindrical shape using “Aviation Fuel Thermal Stability Test Unit (AFTSTU)”. The local growth of surface carbonaceous deposits was measured by the use of three K-type thermocouples which were inserted in discrete locations along the inner surface of heated tube. Subsequently, the deposited tube was sectioned and prepared for “Scanning Electron Microscopy(SEM)” to visualise the circumferential profile of the carbonaceous deposit. This helped to identify the axial profile of deposit thickness by integration of the average deposit thickness at five cross sections along the tube. Using the temperature rise data, a one dimensional, analytical heat transfer model was used to calculate local deposit thickness as a function of time.A transient fuel dependent, two stage chemical kinetic model was developed to simulate the growth of deposit as a function of time, temperature, and fuel chemical composition. In this model, the growth of deposit was assumed to be equal as a geometrical displacement in radial direction. Such a displacement is explicitly calculated using an initial rate of deposition(steady state at t = 0) and accelerating deposition rate(at t=t+Δt) to account for the non linear rate of deposition over the time period of thermal exposure. The concentration of insoluble species and initial rate of deposition as well as temperature at the adjacent layer to the heated surface were obtained through a steady state “computational fluid dynamics(CFD)” simulation using pseudo detailed mechanism of fuel autoxidation by Kuprowicz et al. (2007). The rate parameters of the accelerating deposition were optimised by the application of pattern search method with respect to the calculated deposit thickness from one dimensional heat transfer model. Eventually, the optimised model was used with a transient CFD simulation with dynamic mesh using Ansys Fluent commercial package to predict the growth of deposit in a reactive flow medium. The predicted results are in good agreement with the experimental data obtained from visualised deposit.

Investigation of surface deposition in a simulated fuel injector feed arm with sudden expansion/contraction

Formation of surface carbonaceous deposits at inner surface of two classes of simulated jet engine burner feed arm including a straight tube as well as two tubes with sudden expansion/contraction was studied using “Aviation Fuel Thermal Stability Test Unit (AFTSTU)”. The generated results indicate that phenomena such as stagnant flow formation, flow separation and vena contracta have a substantial impact on surface deposition. Commercial “Computational Fluid Dynamics (CFD)” package, ANSYS Fluent was used to interpret the impact of flow features and heat transfer characteristics on surface deposition. The experimental data obtained in this work were used in a one dimensional heat transfer model for prediction of deposit thickness in simulated burner feed arms. Subsequently, the simulated burner feed arm with contraction/expansion structure were sectioned and prepared for deposit visualisation with “Scanning Electron Microscopy (SEM)”. The results of visualised deposits are consistent with one dimensional heat transfer calculation.The novel set of experimental data presented in this work provides a basis for the construction of predictive models for calculation of deposit growth and total deposit mass in fuel injection system. A description of the model will be addressed in the second paper of this work which is currently under preparation.

Isothermal Combustor Prediffuser and Fuel Injector Feed Arm Design Optimization Using the prometheus Design System

The prometheus combustor design system aims to reduce the complexity of evaluating combustor designs by automatically defining preprocessing, simulation, and postprocessing tasks based on the automatic identification of combustor features within the computer-aided design (CAD) environment. This system enables best practice to be codified and topological changes to a combustor's design to be more easily considered within an automated design process. The following paper presents the prometheus combustor design system and its application to the multiobjective isothermal optimization of a combustor prediffuser and the multifidelity isothermal optimization of a fuel injector feed arm in combination with a surrogate modeling strategy accelerated via a high-performance graphical processing unit (GPU).

Partition lens system for focusing field from PSIRA with TSVS feed on biological target

The Impulse Radiating Antenna (IRA) is suited for radiating picosecond electromagnetic impulse for the treatment of skin cancer. The feed of the reflector IRA is an ultra-wideband antenna. In this proposed work, a Tapered Slot Vivaldi Shaped (TSVS) feed arm is designed for Prolate Spheroidal Reflector (PSR). The feed antenna is placed at the first focal point of the PSR. The picosecond electric pulse is launched from the first focal point and is focused at the second focal point where the target is placed. Next Partition dielectric lens system is designed to enhance the electric field and reduce the spot size of the focused pulse. The TSVS feed arm is matched from 500 MHz to 10 GHz. The 3 dB angular beam width of the proposed IRA with 50 cm aperture diameter is 4.3°, and the radiation efficiency is 63% at 10 GHz. Simulation results show that the full width half maximum of electric field intensity is reduced by 57% in the axial direction and 20% in the lateral direction when compared to the conical feed IRA without lens. The three layer partition lens system greatly reduces the spot size from 1.187 to 0.75 cm, when compared to five layer spherical dielectric lens and increases the electric field by 65%.

Optimizing Aqua Splicer Parameters for Lycra−Cotton Core Spun Yarn Using Taguchi Method

In this paper, optimization of the aqua splicer parameters viz opening time, splicing time, feed arm code (i.e. splice length) and duration of water joining was carried out for 37 tex lycra−cotton core spun yarn for better retained splice strength (RSS%), splice abrasion resistance (RYAR%) and splice appearance (RYA%) using Taguchi experimental design. It is observed that as opening time, splicing time and duration of water joining increase, the RSS% and RYAR% increases, whereas increase in feed arm code leads to decrease in both. The opening time and feed arm code do not have significant effect on RYA%. The optimum RSS% of 92.02 % was obtained at splicing parameters of 350 ms opening time, 180 ms splicing time, 65 feed arm code and 600 ms duration of water joining.

Design of Tunable Monopole Arm Planar Spiral Antenna for Cognitive Radio

This paper presents a spiral antenna design operating in the frequency range of 1–15 GHz having both selective notch bands and wideband response. The main feed arm of spiral antenna is configured as rectangular monopole of width quarter wavelength to achieve impedance matching with standard 50 Ω excitation. Frequency tuning in the design is achieved by placing varactor diode at an appropriate position along the spiral arms and in the ground plane. The design offers a peak gain of 3.4 dB (simulated) and 3 dB (measured). The unique frequency response of antenna makes its suitable to be used for front-end system of cognitive radio for sensing the spectrum in various modes.

Multi-Port Network Approach for the Analysis of Dual Band Fractal Microstrip Antennas

The multiport network approach is extended to analyze the behavior of microstrip fractal antennas. The capacitively fed microstrip square ring antenna has the side opposite to the feed arm replaced with a fractal Minkowski geometry. Dual frequency operation is achieved by suitably choosing the indentation of this fractal geometry. The width of the two sides adjacent to this is increased to further control the resonant characteristics and the ratio of the two resonance frequencies of this antenna. The impedance matrix for the multiport network model of this antenna is simplified exploiting self-similarity of the geometry with greater accuracy and reduced analysis time. Experimentally validated results confirm utility of the approach in analyzing the input characteristics of similar multi-frequency fractal microstrip antennas with other fractal geometries.

Measuring and Correcting Wind-Induced Pointing Errors of the Green Bank Telescope Using an Optical Quadrant Detector

ABSTRACTWind-induced pointing errors are a serious concern for large-aperture high-frequency radio telescopes. In this paper, we describe the implementation of an optical quadrant detector instrument that can detect and provide a correction signal for wind-induced pointing errors on the 100 m diameter Green Bank Telescope (GBT). The instrument was calibrated using a combination of astronomical measurements and metrology. We find that the main wind-induced pointing errors on timescales of minutes are caused by the feed arm being blown along the direction of the wind vector. We also find that wind-induced structural excitation is virtually nonexistent. We have implemented offline software to apply pointing corrections to the data from imaging instruments such as the MUSTANG 3.3 mm bolometer array, which can recover ∼70% of sensitivity lost due to wind-induced pointing errors. We have also performed preliminary tests that show great promise for correcting these pointing errors in real time using the telescope’s subreflector servo system in combination with the quadrant detector signal.

Recent Developments in Acute Pancreatitis

The incidence of acute pancreatitis (AP) has been increasing worldwide, but the major etiologies remain gallstones and alcohol. Several studies have reported that smoking is an independent risk factor for developing AP. Classification of AP has traditionally used the categories of mild and severe disease. However, a new intermediate category of moderately severe AP has been described with intermediate characteristics including a high incidence of local complications but a low mortality. Assessment criteria that can serve as early predictors of AP severity are often complex and not sufficiently accurate. However, several recently described criteria that rely on criteria such as the body mass index, physical findings, and simple laboratory measurements could prove useful if validated in large prospective studies. Many issues related to the therapy of AP are still unresolved. Although preliminary studies support the importance of early volume expansion for the treatment of acute pancreatitis, optimization of the amount and type of fluids will require further studies. Similarly, preliminary studies suggest that enteral nutrition might benefit patients with AP and could even be useful early in the course of disease. However, the timing and type of fluids as well as the intestinal infusion site require further study. Finally, issues related to the prophylactic use of antibiotics in patients with severe AP have not been resolved. While the process of clinical investigation moves slowly, progress has been made in clinical studies of AP.

MICROSTRIP SQUARE RING ANTENNA FOR DUAL-BAND OPERATION

This paper presents a generalized approach to design an electromagnetically coupled microstrip ring antenna for dual-band operation. By widening two opposite sides of a square ring antenna, its fractional bandwidth at the primary resonance mode can be increased significantly so that it may be used for practical applications. By attaching a stub to the inner edge of the side opposite to the feed arm, some of the losses in electrical length caused by widening can be regained. More importantly, this addition also alters the current distribution on the antenna and directs radiations at the second resonant frequency towards boresight. It has also been observed that for the dual frequency configurations studied, the ratio of the resonant frequencies (center dot r(2)center dot center dot r(1)) can range between 1.55 and 2.01. This shows flexibility in designing dual frequency antennas with a desired pair of resonant frequencies.

Tuned to the Universe

The Robert C. Byrd Green Bank Telescope has advanced the knowledge of astronomy with some key discoveries. It assisted in observing the first known double-pulsar binary systems, improving astronomers’ understanding of pulsars and allowing the most precise test yet of general relativity. The telescope would have an offset feed arm, meaning the sub-reflector at the focal point would lie outside the path of incident radio waves, increasing the viewing area by as much as 10 percent. Measuring 100 by 110 meters, the telescope’s oval reflector dish has two acres of surface area. The surface would consist of 2004 panels that could be adjusted in and out to fine-tune the shape of the surface. The basic structure of the telescope consists of the rotating lower section, known as the alidade, and the tipping structure, which tilts within it. The telescope operates over a greater band of wavelengths than any telescope before it and points with greater accuracy. It can zero in on targets within an arc-second, the angle subtended by a dime from a mile away.