bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of Gas Turbine Regenerator Fouling
Authors: Miller James A.
Published: April 2015

Possible mechanisms of gas turbine regenerator fouling are examined and compared with extant experimental evidence. A theoretical model of fouling which encompasses a two-phase process is proposed. It is shown that the controlling mechanism is the condensation of heavy hydrocarbon isomers which form an adhesive coating in which particulate matter subsequently become entrapped. Typical overall heat transfer and pressure drop degradation data are presented which tend to support the proposed model.
Operating Experience With Gas Turbines Under Arctic and Tropical Conditions
Authors: Arvidsson F.
Published: April 2015

Although the operation of gas turbines under arctic conditions may seem very different from operation under tropical conditions, many comparisons can be made and the solutions of varirous problems can be similar. This paper discusses such problems, as well as the more specific matters relating to the two extremes. A short presentation of gas turbine installations suitable for extreme climates is given.
Performance Testing of the Compact APCSE Closed Brayton-Cycle System
Authors: Janis J. M. , Braun G. S. , Ryan R. D.
Published: April 2015

A description of the Advanced Power-Conversion Skid Experiment (APCSE), a 300-kw operating closed Brayton-cycle power-conversion system, is presented. The methods used to predict the performance of the primary-system components and the comparison of these predictions with test results are discussed. Cycle power limitations resulting from deficient performance of some of the primary-loop components, as well as secondary performance effects due to the physical proximity of components, are also discussed.
Gas Turbines Supply Power for Electrolytic Cells
Authors: Swofford R. J.
Published: April 2015

Gas-turbine-driven generating facilities have been installed at the Houston refinery/chemical plant complex of Shell Oil Company to supply electric power to electrolytic cells on a new chlorine plant. The power plant consists of two gas turbines site rated at 15,500 hp, with 1900-hp helper steam turbines driving 3600-rpm generators. The waste-heat boilers used to recover heat from the gas turbine exhaust are equipped with duct burners for steam temperature control and feature two stages of economizer coils. This paper includes a description of the cycle and aspects relating to the initial operation of the equipment.
The Influence of Tailpipe Length on Flame Stability
Authors: Palermo Louis G. , O’Loughlin John R.
Published: April 2015

The influence of tailpipe length on the stability of a flame anchored in a high-velocity propane-air stream contained in a 2-in. pipe test section has been experimentally examined. Two flameholders were studied; a bluff body and a reverse-jet. A satisfactory correlation of the bluff-body data was obtained by plotting (blowoff velocity) (tailpipe length) 0.31 versus equivalence ratio. For the reverse-jet, the correlation procedure yielded a value of 0.64 for the exponent on tailpipe length but the correlation was poorer. A better correlation of the bluff-body data was obtained when the exponent on tailpipe length was taken as a function of equivalence ratio.
The Design and Economics of On-Site Generation With Aircraft-Type Gas Turbines for a Chemical Complex
Authors: Crouchley A. B. , Carroll’ C. E.
Published: April 2015

This paper discusses the economic and technical considerations involved in the decision of a large chemical complex to install on-site power generation; why the gas turbine with waste-heat recovery for process steam generation was determined to be the optimum approach; and the reasons for selecting the aircraft-type gas turbine for this particular application. A brief description of plant components and operation is also included.
Control System for and Sea Operation Experience With CODOG-Powered Frigates
Authors: Svensson Stig Olof
Published: April 2015

The Royal Danish Navy frigate Peder Skram successfully passed her sea trials on March 15–19, 1966, and has been in operation for about nine months, with an accumulated gas turbine operation of 490 hr at the end of December 1966. The frigate has twin-screw CODOG propulsion machinery consisting of a 22,000-shp jet-engine-fed power turbine and a 2400-shp two-stroke diesel engine. These two alternative prime movers drive the propeller shafts with controllable-pitch propellers through a common reduction gear including freewheeling clutches. The control system is described, embracing the governor system, the maneuvering system, and the instrumentation and safety systems. Operational experience at sea, including parts of the trials, is described, as well as experience gained by the Royal Danish Navy, including the voyage made by the frigate to the United States in October–December 1966.
Gas Turbine Versatility as a Generator Driver
Authors: Kay O. F.
Published: April 2015

The versatility of gas turbines driving electric generators is described. Various applications demonstrating this versatility are shown. Special characteristics which can be obtained only with gas turbine drives are illustrated. Some recommendations for further use of the gas turbine in generator drives are explored.
Bristol Siddeley/SNECMA Olympus 593 Powerplant for Concorde
Authors: John Derek J.
Published: April 2015

The optimum powerplant for a Mach 2.2 transport aircraft is a turbojet. The Olympus 593, latest of a well proven family of twin-spool, axial-flow turbojets, has been designed especially for installation in the Concorde. Invaluable development has been achieved from two 90-percent-scale engines and the first seven full-size engines. Satisfactory fuel and oils are now available for Concorde, and the powerplant has already flown in a Vulcan flying test bed.
Calculation of Fluid Motion in Axial Flow Turbomachines
Authors: Smith D. J. L. , Barnes J. F.
Published: April 2015

In the last few years considerable progress has been made in calculating the three-dimensional flows through turbomachines. The two methods which appear to be widely used are what have come to be known as the “Streamline Curvature” and the “Matrix Through Flow” methods. At the National Gas Turbine Establishment, these advanced methods have been applied to existing turbomachines and this paper presents some of the calculated and experimental results for four axial flow machines. By making use of fairly simple loss distributions it has been found that these methods can assist towards the understanding of observed phenomena and, in the case of the axial compressor, they offer some prospect of being able to calculate the onset of surge. Also included is a brief report of work in progress to generate a computer program for the solution of the compressible velocity distribution around the surfaces of turbomachine blades, together with an indication of possible future experimental work.
Use of Flame Sprayed Coatings for Reduction of Initial and Subsequent Repair Costs of Gas Turbines and Components
Authors: Hill R. B.
Published: April 2015

As a result of considering coatings as a tool to parts reclamation, enhancing a part, new parts processing and value analysis, this paper covers the subject title in a manner which the author hopes will give a basis for problem solving by flame sprayed coatings. To assist in this basis, a chart of material analysis, a nomograph of masking time, typical charts of spray, blast, and machine times, and a discussion of a micro surface are included for future reference.
The Ballistic Air Cleaner Concept for Army Vehicular Gas Turbines
Authors: DuRocher L. J. , Giannotti Hugo
Published: April 2015

The air cleaner requirements for Army vehicular gas turbines are developed and performance of the novel boundary-layer ballistic type separator is discussed. A unit specifically designed for gas turbines demonstrates high performance. This separator is compared and field results are included.
Performance and Potential of Perforated Plates as a Heat Transfer Surface
Authors: Osborn H. H. , Shah R. K. , Liljelund R. J. H. , Wolf P. C. , Eichhorn R.
Published: April 2015

The heat transfer and flow friction characteristics of a number of parallel plate surfaces with round or slotted perforations are presented. Their performance is compared to the parallel nonperforated plate as a standard and is shown to be very promising in terms of reducing the free area of volume of gas turbine regenerators. Sound and vibration phenomena were observed and recorded. To gain an understanding of the flow behavior over the perforations, a scaled-up flow visualization study was performed.
British Experience With Propulsion Machinery for Air Cushion Vehicles
Authors: Woodward M. L.
Published: April 2015

The paper outlines the position of the areo gas turbine engine as applied to the marine field, and illustrates the relationship of this work to the development of the Air Cushion Vehicle (Hovercraft) in Britain. A brief description is given of the installation of the Marine Gnome gas turbine in the SRN.5/6 Hovercraft and illustrates how the advent of these small craft suddenly resulted in extensive engine usage, together with the imposition of a wide variety of operating problems; some of the measures taken to keep pace from the engine viewpoint are covered in detail. Finally, there is a glimpse at second generation Hovercraft and the application of the Marine Proteus to these.
Fire Detection Techniques for Supersonic Aircraft
Authors: Beery G. T. , Trumble T. M.
Published: April 2015

The problems of detecting fire and overheat in a supersonic aircraft, while similar to those in subsonic aircraft, have certain unique characteristics. These characteristics are due basically to the dynamic and thermal environment associated with the Mach 3 to Mach 4.5 flight regime. This paper presents an approach toward the solution of these problems and provides a brief history of aircraft fire and overheat detection leading to current system design concepts.
A Turboprop Engine Advanced Adaptive Fuel Control With a High Contamination Tolerance
Authors: Keck M. F. , Schwent G. V. , Fredlake J. J. , Minshall B. J.
Published: April 2015

This paper describes an advanced adaptive fuel control that was developed and tested successfully on a Garrett Corporation YT76 single-shaft turboprop engine. The express purpose of the development was to achieve engine operation without adjustment of the control when using a wide variety of fuels and to achieve operation with unfiltered fuel when contamination in accordance with military aircraft requirements.
Dust Erosion of Compressor Materials: Experience and Prospects
Authors: Compton W. A. , Steward K. P.
Published: April 2015

The replacement costs resulting from dust erosion of military and commercial gas turbine engines at present are excessive. Foreshortened operating life of gas turbines is reportedly costing the military services over $150,000,000 a year in the Southeast Asia operations alone. Similar experiences exist in many new applications of commercial gas turbines in this country. It is imperative, therefore, that more detailed understanding of dust erosion be generated and ways of minimizing engine performance degradation be demonstrated. Blade erosion can be diminished either by minimizing dust ingestion or by selecting materials with maximum dust erosion resistance. This paper discusses the prospects for improved dust erosion resistance of compressor materials.
Variable Geometry Gas Turbine Radial Compressors
Authors: Rodgers C.
Published: April 2015

An examination of the various mechanical and aerodynamic methods of flow and pressure regulation through high-speed, single-stage radial compressors is presented. Performance testing of a small gas turbine radial compressor with a variable vaned diffuser system is described. Methods of combined geometry variation to obtain minimum reduction of efficiency with flow variation are suggested based upon theoretical matching studies.
Status Report on the Olympus 593 for Concorde
Authors: Woodward J. A.
Published: April 2015

Concorde’s Olympus 593 engines have now reached an advanced stage of development. As a result of improved technology, certain changes have been made to the original engine concept. Two of these, a new low-pressure fuel system and a new and more accurate method of turbine temperature measurement have been brought into the development program. This paper discusses both features and examines their implications. It concludes with a resume of the current status of the development program.
Pressure Jet Spray in Air Stream
Authors: Mellor R. , Chigier N. A. , Beér J. M.
Published: April 2015

A study has been made of droplet trajectories in a hollow cone pressure-jet water spray operating in a uniform axial airflow of 13.9 m/s. Use of a double spark light source enabled measurements of drop velocities, sizes and angles of trajectories to be made on droplets in the size range 20 to 250 microns with velocities up to 37 m/s. Entrainment into the spray of the surrounding airflow was found to be negligible in a wind tunnel and it was found possible to predict the trajectories of individual drops on the basis of the steady-state equation of motion for single solid spheres in an infinite quiescent atmosphere. Average droplet behavior could not be predicted because of the wide variation in initial droplet conditions.
Turbocirculator for High Temperature Gas-Cooled Reactors
Authors: Yampolsky J. , Melese D’Hospital G. , Cavallaro L. , Barbat V. J.
Published: April 2015

The present design study was part of a program undertaken for the purpose of determining the feasibility, establishing the development requirements, and estimating the cost of a turbocirculator to provide the pumping power for a 1000-MWe High Temperature Gas Cooled Reactor (HTGR). Methods were developed for the optimization of the thermodynamic cycle and the design point of the turbocirculator components. A comparison of a turbocirculator to other ways of pumping helium in a HTGR is also shown in this paper. A design of the machine with its associated bearing and seal system and gas conduits was carried out. An important feature of this design is incorporation with the other components of the nuclear steam supply system within the prestressed concrete reactor pressure vessel.
Advanced Composites: A State-of-the-Art Assessment
Authors: Peterson G. P.
Published: April 2015

There have been truly significant advances made in the development of advanced composite materials during the decade of the 1960’s. These advances have been specially noteworthy since they have occured in an environment which has not been conducive to either the rapid development or the early operational weapon system usage of new technology. We have seen, however, advanced composite technology literally emerge from the boron filament laboratory apparatus stage in 1961 to the point where boron composite primary aircraft structure production commitment was proposed in 1967 on Air Force aircraft and production commitment on horizontal stabilizer structure was made in 1968 by Grumman Aircraft and the Navy on F-14 aircraft. The success achieved warrants a brief look at the background and developmental approaches which are substantially different from those involved with the development of titanium.
World’s Largest Single-Shaft Gas Turbine Installation
Authors: Gaskins R. C. , Stevens J. M.
Published: April 2015

A unique 63,000-kw gas and steam turbine generator has been successfully integrated into a power plant to provide base load electric power and heat feedwater for existing boilers. The unit combined the world’s largest single-shaft gas turbine prototype with innovations of supercharging and a 20,000-kw steam turbine helper on the same shaft. The system, now a part of a Dow Chemical Power Plant in Freeport, Texas, had some minor problems mainly with the prototype turbine and has been in successful base load service since January, 1969.
Fire Detection Technology for Turbine-Powered Transportation
Authors: Trumble T. M.
Published: April 2015

The problems of providing a fire and overheat detection system for turbine-powered vehicles must be solved during the design phase of the vehicle. In order to accomplish this goal the vehicle design engineer must be aware of the basic constraints involved in the application of fire detection technology. This paper presents a condensed method for understanding, designing and evaluating fire and overheat detection systems. Advanced concepts and technologies such as optical redundancy and high temperature ultraviolet sensors are discussed. Performance of fire and overheat detection systems designed using this approach will provide maximum safety for those using the vehicles, as well as those in its operational envelope.
Design and Operation of a Gas Compressor Set
Authors: Glessner J. W.
Published: April 2015

The use of a small industrial gas turbine with a matching gas compressor has produced a compressor set which has become a leader in the natural gas pipeline industry. This paper describes the design of one of these sets including details of the gas compressor. While accumulating nearly 4,000,000 hr operating time, these sets have proved to be very flexible in operation. They are used in five continents over an extreme range of environments and gas compression services. Some of these installations are described in detail.
Digital Computer Control of Gas Turbine Engines
Authors: Eccles E. S. , Shutler A. G.
Published: April 2015

The use of digital computer methods to control aero gas turbines is comparatively new. The paper attemps to cover their background and essential features in broad outline. It discusses the special properties of digital computer control systems in relation to hydromechanical and electric analog arrangements and the special problems of design and safety involved. Some results of practical tests on a large complex engine are presented and discussed, special emphasis being given to those techniques which are particular to digital systems. The paper finally suggests the directions in which future developments of these systems might move.
Experimental Investigation of the Shaft Dynamics of a Gas Turbine-Reciprocating Compressor Drive
Authors: Erdmann Omer , Horne John
Published: April 2015

A test was conducted to explore the dynamic mechanical characteristics of a gas turbine-reciprocating compressor system, to define its optimum running conditions, and to verify the analytical results presented in ASME Paper 68-WA/GT-4. This paper summarizes the results of that test.
Boundary Layer Characteristics on the Buckets of a Large-Scale Turbine Stage: Part 1 — Profiles of Mean and Turbulent Velocity Vectors
Authors: Day W. H.
Published: April 2015

Data have been obtained on details of the three-dimensional boundary layer flow on rotating turbine buckets using hot-wire anemometer and flow visualization techniques. Profiles of velocity magnitude and two angular directions are presented for both the mean and turbulent velocity vectors, as well as profiles of the three products of fluctuating velocities. The data were obtained along six flow paths covering the pressure and suction sides at three radial heights. A high degree of turbulence relative to the rotating buckets was found at all points in the boundary layer on both the pressure and suction sides. Also three-dimensional (radial flow) effects in the boundary layer were significant.
Measurements on a Blast-Furnace-Gas and Oil-Fired Combustion Chamber of a 17.25-MWe Closed-Cycle Gas Turbine Plant
Authors: Bammert K. , Rehwinkel H.
Published: April 2015

The paper discusses the present stage of development of combustion chambers for fossil-fired closed-cycle gas turbines, describing West Germany’s “Gelsenkirchen” plant which can be operated with blast-furnace gas and fuel oil with any desired ratio of gas to oil. The output data and the efficiency of this plant are illustrated by test results. In the development and construction of fossil-fired closed-cycle gas turbine plants, the gas heater presents the greatest difficulties and is the most expensive part of the plant. Therefore, very detailed measurements were taken to determine the total heat absorption in the combustion chamber and its local distribution over the length of the chamber. The results obtained are compared with previous measurements at a smaller plant, the mine-gas and pulverized-coal fired “Haus Aden” plant.
Technological Trend of Aircraft Gas Turbines and its Effect on the Development for Ship Propulsion Plants
Authors: Scholz N. K. H.
Published: April 2015

The effect of the main design parameters of the aero gas turbine engine cycle, namely combustion temperature and compression pressure ratio, on the specific performance values is discussed. The resulting development trend has been of essential influence on the technology. Relevant approaches are outlined. The efforts relating to weight and manufacturing expense are also indicated. In the design of aero gas turbine engines increasing consideration is given to the specific flight mission requirements, such as for instance by the introduction of the by-pass principle. Therefore direct application of aero gas turbine engines for ship propulsion without considerable modifications, as has been practiced in the past, is not considered very promising for the future. Nevertheless, there are possibilities to take advantage of aero gas turbine engine developments for ship propulsion systems. Appropriate approaches are discussed. With the experience obtained from aero gas turbine engines that will enter service in the early seventies it should be possible to develop marine gas turbine engines achieving consumptions and lifes that are competitive with those of advanced diesel units.
Description of the Shore Test of Propulsion Plant for DDH-280 Class Gas Turbine Destroyers
Authors: Legallais N. H. , Healey E. J.
Published: April 2015

The propulsion plant for the DDH Class Helicopter Destroyers under construction for the Canadian Armed Forces was shore tested at the United States Navy’s Naval Ship Engineering Centre, Philadelphia Division (NAVSEC PHILADIV). Erection of the facility started in September 1967 and testing commenced in March of 1969. Completion of testing is scheduled for late November, 1969. The port shaft line of machinery including one Pratt & Whitney Aircraft (P & WA) FT4A-2 and one P & WA FT12A-3 engine, gearing, mounting system, ancillary equipment and the control system were subjected to testing during the period. Described herein are some of the more interesting aspects of the erection of the facility, the testing, the results and some of the problems encountered during all these phases.
CH-54A Engine Air Particle Separator-3 1/2 Years of Successful Operation
Authors: Stephenson C. D.
Published: April 2015

The CH-54A EAPS — the first effective, operational Engine Air Particle Separator — has been in field service in Southeast Asia for 3 1/2 years. In that time, engine times between removal for erosion have increased from approximately 80 hr to over 800 hr. Due to the availability of EAPS, engine TBO has increased from 400 to 800 hr. This paper reviews EAPS operational experience to date. The environment at operational sites is reviewed, engine removal history is summarized, and the various design improvements developed during this period are discussed. Recommendations for future systems design and development are included.
Design and Operating Experiences With Gas Turbine Combined Cycle Units
Authors: Jones R. W. , Shoults A. C.
Published: April 2015

This paper presents details of three large gas turbine installations in the Freeport, Texas, power plants of the Dow Chemical Company. The general plant layout, integration of useful outputs, economic factors leading to the selection of these units, and experiences during startup and operation will be reviewed. All three units operate with supercharging fan, evaporative cooler, and static excitation. Two of the installations are nearly identical 32,000-kw gas turbines operating in a combined cycle with a supplementary fired 1,500,000-lb/hr boiler and a 50,000-kw noncondensing steam turbine. The other installation is a 43,000-kw gas turbine and a 20,000-kw starter-helper steam turbine on the same shaft. The gas turbine exhaust is used to supply heated feedwater for four existing boilers.
Effects of Reynolds Number on Performance Characteristics of a Centrifugal Compressor
Authors: Mashimo Toshio , Suefusa Hiroshi , Ariga Ichiro , Watanabe Ichiro
Published: April 2015

The influences of the Reynolds number on centrifugal compressor performance have not so much been investigated. Especially, the experimental equation representing the rates of losses for the critical Reynolds number has been seemingly not established. Namely, the coefficients in the equation differ with each investigator. In the present study, an experiment was conducted by means of an experimental centrifugal compressor. From the results, it was found that the critical Reynolds number Recmeancr was reasonable for the compressor stage as well as for the impeller, and for the former it amounted to about 0.9∼1.3 × 105, while for the latter it amounted to about 0.9∼1.2 × 105. On the other hand, the critical Reynolds number Rec2cr was also found appropriate for the diffuser and it amounted to about 0.9∼1.5 × 105. In addition, the coefficients in the experimental equation which introduced the rate of losses were estimated.
Silencing Considerations for Large Gas Turbine Generator Sets
Authors: Surowiec M. W.
Published: April 2015

An attempt is made in this paper to inform the reader of the noise sources which are a problem when attempting to meet various criteria. Starting with the relatively easy-to-meet criteria of NEMA H to the more difficult NEMA D, and the stringent criteria of NEMA B, various noise components which could cause the overall system noise level to miss the specified criteria are considered, and their effect to the system is shown.
Single Process Plant Application of a Gas Turbine Generator With Recovery Boiler
Authors: Klein R. W.
Published: April 2015

This paper consists of the application considerations given for the selection of on-site power generation using a gas turbine with a recovery boiler in the process chemical industry. The additional use of 400 psig steam from recovery heat of the gas turbine exhaust used for process steam is evaluated. The techniques used for engineering, construction, training, and start-up are discussed. The performance of the unit after 30,000 operating hours, including reliability and a discussion of equipment problems, is included.
Gas Turbines for Pipeline Compressor Drives in North America and Europe
Authors: Parker R. F.
Published: April 2015

A brief statistical comparison of the application of gas turbines to gas pipeline compressor drives in North America and Europe is given. Basic similarities in the installations in North America and in Eurpoe are discussed briefly. Differences in application, in installation, in equipment, and in operation are shown. The factors — geographical, political, and operational — which are responsible for these differences are discussed. Future trends in North America and Europe and factors which may influence the elimination of some of the present differences but which may create new ones are also presented.
The Performance of the TCS 670-B Turbine in the Closed Cycle Test Facility at Fort Belvoir, Virginia
Authors: Manning G. B.
Published: April 2015

The design of the first compact AK Process Nuclear system in the United States was performed under the auspices of the Corps of Engineers. U. S. Army, Fort Belvoir, Va. Taking into account that there was virtually nothing on the shelf that could be used, and realizing that the feasibility of such a system first had to be established, demonstration models were built for the various subsystem components which were to eventually go into the complete system. The last and final turbine-compressor set tested as a backup unit for this program was the TCS 670-B. This paper reports the turbine performance obtained from this machine when tested in the Closed Cycle Test Facility (APCEF) at Fort Belvoir, Va.. in 1969. The compressor performance is not included.
Olin’s Five-Year Experience in Gas Turbine Operation
Authors: Lowery J. H.
Published: April 2015

Olin’s five-year experience in gas turbine operation shows the ammonia process, turbine and services rendered by the turbine with relation to the process. A start up and shutdown procedure is outlined as to the sequel steps followed at each start-up and shutdown. The final phase of the paper relates Olin’s experience in operating the gas turbine for the past five years. Explanations of problems and corrective action taken are included, along with some humorous experiences encountered.
A Comparison of Simulated Gas Turbine Ship Handling Characteristics With Several Different Transmission Systems
Authors: Rowen W. I.
Published: April 2015

This paper describes the handling characteristics of a simulated, gas turbine powered vessel using several different transmission schemes. These include both mechanically clutched and hydrodynamic reversing reduction gears, and two modes of operation using controllable, reversible pitch propellers. Schemes for controlling the various transmission systems are described together with the necessary integration to provide “single lever” propulsion control. The response of the simulated systems are presented for both normal and emergency maneuvers.
Cyclic Energy Demands Supplied Economically With Gas Turbines and Combined Cycle Plants
Authors: Smith H. L. , Budenholzer R. J.
Published: April 2015

The electric utility industry is finding a need for a new class of generation termed intermediate. This paper presents results of generation addition pattern studies performed to determine the relative merits of steam peaking plants and combined cycle plants in filling these needs. Corresponding optimum addition patterns are established for simple cycle gas turbine and nuclear power plants. The combined cycle and steam peaking plants are shown to be comparable at high cost levels, while the combined cycle shows definite advantage if permitted to burn non-distillate fuel.
The Supersonic Turbine: A Design and Cascade Study
Authors: Fruchtman Irving
Published: April 2015

Fundamental concepts are given for the design of a turbine stage with supersonic gas velocities relative to the blading. Minimum-length nozzles (stators) and free-vortex-type rotor blades are specified and a correlation of their published performance is given. A blade selection chart is given to provide a method for obtaining appropriate low-loss rotor blade configurations. A series of two-dimensional cascade experiments are described in which the performance of film-cooled, blunted leading-edge rotor blades were measured. Blade performance is given over a range of inlet Mach numbers and cooling flows.
Flat acoustic sources with frequency response correction based on feedback and feed-forward distributed control
Authors: Ho Jen-Hsuan , Berkhoff Arthur P.
Published: April 2015

This paper presents an acoustic source with a small thickness and high bending stiffness. The high bending stiffness is obtained with a sandwich structure in which the face of the sandwich structure internal to the source is perforated to increase the acoustic compliance, thereby leading to increased electroacoustic conversion efficiency. Multiple actuators are used to drive the moving component of the acoustic source. Control of the acoustic resonances and structural resonances is required to obtain an even frequency response. The use of collocated decentralized feedback control based on velocity sensing was found to be ineffective for controlling these resonances due to the destabilizing asymmetric modes caused by the coupling of the internal acoustic cavity and the rigid body vibration of the moving component. Resonances can be controlled by a set of independent combinations of symmetric driving patterns with corresponding velocity feedback controllers such that the fundamental mass-air resonance is effectively controlled, as is the lowest bending mode of the moving component. Finally, a compensation scheme for low frequencies is used which enables a flat frequency response in the range of 30 Hz to 1 kHz with deviations smaller than 3 dB.
Directional cloaking of flexural waves in a plate with a locally resonant metamaterial
Authors: Colombi Andrea , Roux Philippe , Guenneau Sebastien , Rupin Matthieu
Published: April 2015

This paper deals with the numerical design of a directional invisibility cloak for backward scattered elastic waves propagating in a thin plate (A0 Lamb waves). The directional cloak is based on a set of resonating beams that are attached perpendicular to the plate and are arranged at a sub-wavelength scale in ten concentric rings. The exotic effective properties of this locally resonant metamaterial ensure coexistence of bandgaps and directional cloaking for certain beam configurations over a large frequency band. The best directional cloaking was obtained when the resonators' length decreases from the central to the outermost ring. In this case, flexural waves experience a vanishing index of refraction when they cross the outer layers, leading to a frequency bandgap that protects the central part of the cloak. Numerical simulation shows that there is no back-scattering in these configurations. These results might have applications in the design of seismic-wave protection devices.
Generation of random microstructures and prediction of sound velocity and absorption for open foams with spherical pores
Authors: Zieliński Tomasz G.
Published: April 2015

This paper proposes and discusses an approach for the design and quality inspection of the morphology dedicated for sound absorbing foams, using a relatively simple technique for a random generation of periodic microstructures representative for open-cell foams with spherical pores. The design is controlled by a few parameters, namely, the total open porosity and the average pore size, as well as the standard deviation of pore size. These design parameters are set up exactly and independently, however, the setting of the standard deviation of pore sizes requires some number of pores in the representative volume element (RVE); this number is a procedure parameter. Another pore structure parameter which may be indirectly affected is the average size of windows linking the pores, however, it is in fact weakly controlled by the maximal pore-penetration factor, and moreover, it depends on the porosity and pore size. The proposed methodology for testing microstructure-designs of sound absorbing porous media applies the multi-scale modeling where some important transport parameters—responsible for sound propagation in a porous medium—are calculated from microstructure using the generated RVE, in order to estimate the sound velocity and absorption of such a designed material.
Passive estimation of internal temperatures making use of broadband ultrasound radiated by the body
Authors: Anosov Andrey A. , Kazansky Alexandr S. , Subochev Pavel V. , Mansfel'd Anatoly D. , Klinshov Vladimir V.
Published: April 2015

The internal temperatures of plasticine models and the human forearm in vivo were determined, based on remote measurements of their intrinsic ultrasonic radiation. For passive detection of the thermal ultrasonic radiation an acoustic radiometer was developed, based on a broadband 0.8–3.3 MHz disk-shaped ultrasonic detector with an 8 mm aperture. To reconstruct temperature profiles using the experimentally measured spectra of thermal acoustic radiation a priori information was used regarding the temperature distribution within the objects being investigated. The temperature distribution for heated plasticine was considered to be a monotonic function. The distribution for the human forearm was considered to fit a heat equation incorporating blood flow parameters. Using sampling durations of 45 s the accuracy of temperature measurement inside a plasticine model was 0.5 K. The measured internal temperature of the forearm in vivo, at 36.3 °C, corresponded to existing physiological data. The results obtained verify the applicability of this passive method of wideband ultrasonic thermometry to medical applications that involve local internal heating of biological tissue.
Passive probing of the sound fixing and ranging channel with hydro-acoustic observations from ridge earthquakes
Authors: Evers Läslo G. , Snellen Mirjam
Published: April 2015

The International Monitoring System includes a hydro-acoustic part to verify the Comprehensive Nuclear-Test-Ban Treaty. Besides explosive signals, monitoring stations also detect acoustic waves from earthquakes that travel through the SOund Fixing And Ranging (SOFAR) channel. The travel times of such detections are listed in the Reviewed Event Bulletin, which is statistically evaluated for the stations located in the Pacific, Indian, and Atlantic Oceans. The celerities of ridge earthquakes are calculated to build up a homogeneous data-set, based on similar source mechanisms. The celerity is defined as the epicentral distance divided by the travel time. The global characteristics of these celerities can be well understood in terms of temperature variations in the SOFAR channel. A detailed velocity profile has been retrieved for the Atlantic Ocean where large differences (14 m/s) are found between the southern and northern parts of the basin. Propagation modeling with normal modes supports these findings, which shows that the celerity gives an estimate of the sound speed in the SOFAR channel. These results compare remarkably well with those from active experiments, showing the ability of passively probing the SOFAR channel with hydro-acoustic waves from earthquake sources.
Grid-free compressive beamforming
Authors: Xenaki Angeliki , Gerstoft Peter
Published: April 2015

The direction-of-arrival (DOA) estimation problem involves the localization of a few sources from a limited number of observations on an array of sensors, thus it can be formulated as a sparse signal reconstruction problem and solved efficiently with compressive sensing (CS) to achieve high-resolution imaging. On a discrete angular grid, the CS reconstruction degrades due to basis mismatch when the DOAs do not coincide with the angular directions on the grid. To overcome this limitation, a continuous formulation of the DOA problem is employed and an optimization procedure is introduced, which promotes sparsity on a continuous optimization variable. The DOA estimation problem with infinitely many unknowns, i.e., source locations and amplitudes, is solved over a few optimization variables with semidefinite programming. The grid-free CS reconstruction provides high-resolution imaging even with non-uniform arrays, single-snapshot data and under noisy conditions as demonstrated on experimental towed array data.
Calibration of a broadband acoustic transducer with a standard spherical target in the near field
Authors: Chu Dezhang , Eastland Grant C.
Published: April 2015

This paper investigates the applicability of calibrating a broadband acoustic system in the near field. The calibration was performed on a single transducer with a mono-static configuration using a single standard target, a 25-mm tungsten carbide sphere in the nearfield of both the transducer and the sphere. A theoretical model was developed to quantify the nearfield effect. Numerical simulations revealed that the frequency responses at different distances varied significantly, the null positions were essentially invariant—a unique characteristic for determination of the compressional and shear wave speeds in the calibration sphere. The calibration curves obtained in the near field could be applied to farfield once the nearfield effects were accounted for. Since the transducer was located in the near field, the signal-to-noise ratio was high, resulting in a much wider useable bandwidth than the nominal bandwidth. The resultant calibration uncertainty, i.e., root-mean-square uncertainty over the entire usable frequency band was 1.05 dB and reduces to 0.33 dB when the regions corresponding to nulls were excluded. The methods reported here could potentially be applied to the calibration of multibeam and broadband echosounder/sonar systems since it is difficult to meet the farfield condition for outermost beams when shipboard calibrations are needed.
Effects of multiple impulses from a seismic air gun on bottlenose dolphin hearing and behavior
Authors: Finneran James J. , Schlundt Carolyn E. , Branstetter Brian K. , Trickey Jennifer S. , Bowman Victoria , Jenkins Keith
Published: April 2015

To investigate the auditory effects of multiple underwater impulses, hearing thresholds were measured in three bottlenose dolphins before and after exposure to 10 impulses produced by a seismic air gun. Thresholds were measured at multiple frequencies using both psychophysical and electrophysiological (auditory evoked potential) methods. Exposures began at relatively low levels and gradually increased over a period of several months. The highest exposures featured peak sound pressure levels from 196 to 210 dB re 1 μPa, peak-peak sound pressure levels of 200–212 dB re 1 μPa, and cumulative (unweighted) sound exposure levels from 193 to 195 dB re 1 μPa2s. At the cessation of the study, no significant increases were observed in psychophysical thresholds; however, a small (9 dB) shift in mean auditory evoked potential thresholds, accompanied by a suppression of the evoked potential amplitude function, was seen in one subject at 8 kHz. At the highest exposure condition, two of the dolphins also exhibited behavioral reactions indicating that they were capable of anticipating and potentially mitigating the effects of impulsive sounds presented at fixed time intervals.
Acoustic centering of sources with high-order radiation patterns
Authors: Shabtai Noam R. , Vorländer Michael
Published: April 2015

Surrounding spherical microphone arrays have recently been used in order to model the radiation pattern of acoustic sources that are assumed to be at the center of the array. Source centering algorithms are applied to the measurements in order to reduce the negative effect of acoustic source misalignment with regard to the physical center of the microphone array. Recent works aim to minimize the energy that is contained in the high-order coefficients of the radiation pattern in the spherical harmonics domain, in order to directly address the problem of increased order and spatial aliasing resulted by this misalignment. However, objective functions which directly minimize the norm of these coefficients were shown to be convex only when employed on sources with low-order radiation patterns. This work presents a source centering algorithm that operates on plane sections and aims to achieve a convex objective function on every plane section. The results of the proposed algorithm are shown to be more convex than the previous algorithms for sources with higher-order radiation pattern, usually at higher frequencies.
Spatial release of cognitive load measured in a dual-task paradigm in normal-hearing and hearing-impaired listeners
Authors: Xia Jing , Nooraei Nazanin , Kalluri Sridhar , Edwards Brent
Published: April 2015

This study investigated whether spatial separation between talkers helps reduce cognitive processing load, and how hearing impairment interacts with the cognitive load of individuals listening in multi-talker environments. A dual-task paradigm was used in which performance on a secondary task (visual tracking) served as a measure of the cognitive load imposed by a speech recognition task. Visual tracking performance was measured under four conditions in which the target and the interferers were distinguished by (1) gender and spatial location, (2) gender only, (3) spatial location only, and (4) neither gender nor spatial location. Results showed that when gender cues were available, a 15° spatial separation between talkers reduced the cognitive load of listening even though it did not provide further improvement in speech recognition (Experiment I). Compared to normal-hearing listeners, large individual variability in spatial release of cognitive load was observed among hearing-impaired listeners. Cognitive load was lower when talkers were spatially separated by 60° than when talkers were of different genders, even though speech recognition was comparable in these two conditions (Experiment II). These results suggest that a measure of cognitive load might provide valuable insight into the benefit of spatial cues in multi-talker environments.
Time reversal technique for gas leakage detection
Authors: Maksimov A. O. , Polovinka Yu. A.
Published: April 2015

The acoustic remote sensing of subsea gas leakage traditionally uses sonars as active acoustic sensors and hydrophones picking up the sound generated by a leak as passive sensors. When gas leaks occur underwater, bubbles are produced and emit sound at frequencies intimately related to their sizes. The experimental implementation of an acoustic time-reversal mirror (TRM) is now well established in underwater acoustics. In the basic TRM experiment, a probe source emits a pulse that is received on an array of sensors, time reversed, and re-emitted. After time reversal, the resulting field focuses back at the probe position. In this study, a method for enhancing operation of the passive receiving system has been proposed by using it in the regime of TRM. Two factors, the local character of the acoustic emission signal caused by the leakage and a resonant nature of the bubble radiation at their birth, make particularly effective scattering with the conjugate wave (CW). Analytical calculations are performed for the scattering of CW wave on a single bubble when CW is formed by bubble birthing wail received on an array, time reversed, and re-emitted. The quality of leakage detection depends on the spatio-temporal distribution of ambient noise.
Finite series expansion of a Gaussian beam for the acoustic radiation force calculation of cylindrical particles in water
Authors: Zhang Xiaofeng , Song Zhiguang , Chen Dongmei , Zhang Guangbin , Cao Hui
Published: April 2015

This paper focuses on studying the interaction between an acoustical Gaussian beam and cylindrical particles. Based on the finite series method, the Gaussian beam is expanded as cylindrical functions and the beam coefficient of a Gaussian beam is obtained. An expression for the acoustic radiation force function that is the radiation force per unit energy density and unit cross-sectional surface area for a cylinder in a Gaussian beam is presented. Numerical results for the radiation force function of a Gaussian beam are presented for rigid cylinders, liquid cylinders, elastic cylinders, and viscoelastic cylinders to illustrate the theory. The radiation force function versus the dimensionless frequency ka (where k is the wave number and a is the radius of the cylinder) are discussed for different beam waists. The simulation results show the differences from those of a plane wave when the beam waist w0≤5λ (where λ is the wave length). The beam waist has no effects on the radiation force function when ka<1, while the beam waist has greater effects when ka>1. The radiation force function reaches the plane wave limit when w0>5λ. The acoustic radiation force function is also determined by the parameters of the particles.