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Ceramics

1983;():V005T11A001. doi:10.1115/83-GT-112.
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Development of ceramic components for the Garrett/Ford AGT101, Advanced Gas Turbine Powertrain System Development Project, authorized under NASA Contract DEN3-167 is an iterative process involving current and advanced NDE inspection techniques, visual/dimensional inspection, and mechanical and thermal screening tests. Analytically predicted peak thermal and/or mechanical component stresses have been defined for engine operation and are closely simulated during rig testing. As development testing continues steady state strain and transient thermal data is continually fed back to the analytical models to aid in the design/development process. As part of the ceramic development task for the AGT101 a set of ceramic parts (49), constituting a complete assembly of engine structural hardware has been successfully rig tested to 1144K (1600°F) without incident, qualifying this assembly for subsequent engine testing. During the course of testing approximately 7.5 hours of 1144K (1600°F) operation has been accumulated on the assembly.

Commentary by Dr. Valentin Fuster
1983;():V005T11A002. doi:10.1115/83-GT-203.
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An experimental study was conducted to evaluate the effect of several grinding variables on the room temperature strength of Norton NC-132 hot pressed silicon nitride. The grinding variables studied included diamond grit size, diamond concentration, type of diamond bond, downfeed rate and type of cut. Significant effects on strength were noted for all variables except diamond concentration.

Commentary by Dr. Valentin Fuster
1983;():V005T11A003. doi:10.1115/83-GT-206.
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An x-ray radiographic NDE system specifically suited to three-dimensional tomographic reconstruction is described. The results of two applications of the system are discussed. The first is the reconstruction of a section of a ceramic gas turbine rotor blade. This demonstrates the system’s ability to reconstruct parts with complex external shape. In the second, an assembly of ceramic components containing a 50 μm gap is examined. The 50 μm gap is detected. This work was supported in part by the Office of Naval Research under contract N00014-78-C-0714.

Commentary by Dr. Valentin Fuster
1983;():V005T11A004. doi:10.1115/83-GT-223.
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The durability of thermally shocked high tempererature ceramic coatings on metal substrates can be dramatically improved using a fiber metal strain isolator between ceramic and metal. The fiber metal strain isolator is a compliant, porous and low modulus material which yields to control the stress on the ceramic coating during thermal cycling. Plasma sprayed strain isolated ceramic coatings .060” (1.5 mm) thick have shown excellent durability in thermal shock testing. The strain isolated ceramic coating is an excellent thermal barrier since both the ceramic and fiber metal are good insulators. Applications include ceramic thermal barrier coatings for gas turbine engine seals and turbine components, combustors, MHD electrodes, and internal combustion engine insulation.

Commentary by Dr. Valentin Fuster
1983;():V005T11A005. doi:10.1115/83-GT-240.
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This paper describes the final phase of testing and evaluation of the second stage monometallic water-cooled nozzles for the Department of Energy-funded High-Temperature Turbine Technology (HTTT) program. Earlier papers described the materials and process development work and the fabrication and initial testing of these nozzles. The additional testing of these nozzles in a static hot-gas path development test stand is described, and the results of this testing are discussed in terms of the component design goals. Evaluation of these nozzles after testing, including nondestructive and destructive examination is described in detail.

Commentary by Dr. Valentin Fuster
1983;():V005T11A006. doi:10.1115/83-GT-244.
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Two complementary single crystal alloys have been developed from the MAR-M-247 composition, with the objectives of providing high creep-rupture strength, excellent oxidation resistance, good castability, practical solution heat-treatment ranges, high incipient melting points, and stable microstructures. The alloys, CM SX-2 and CM SX-3, are turbine blade and vane alloys, with CM SX-3 showing improved coated oxidation and corrosion resistance. Foundry performance characteristics studied using ten different single crystal casting processes to produce both solid and complex cored, thin-wall turbine blade and vane components were: “freckling” sensitivity, spurious grain formation, microporosity, and alloy/ceramic core reactions. Practical solution heat-treatment ranges (difference between the γ′ solvus and the incipient melting temperatures) have been established and vary from 45–50°F for CM SX-3 and 50–55°F for CM SX-2 measured without prior homogenization treatments. Extensive machined-from-blade (MFB) mechanical property work is reported. Alloy stability investigations were undertaken using prior tested MFB stress-rupture specimens. Environmental evaluations using both bare and coated single crystal specimens, subjected to separate cyclic/dynamic oxidation, and corrosion testing in burner-type rigs are also reviewed. A new γ′ microstructure/heat-treatment technology has been found to be particularly applicable to CM SX-2 and CM SX-3 alloys, because of their low γ/γ′ mismatch and suitable γ′ chemistry. This technology further increases the creep-rupture capability of both alloys by 10–40°F, depending on test temperature.

Commentary by Dr. Valentin Fuster

Structures and Dynamics

1983;():V005T12A001. doi:10.1115/83-GT-89.
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Polygonal finite elements displaying linear displacement on specified edges and quadratic displacement elsewhere are formed. Models composed of these elements identified with simple quadrilateral meshes produce marked improvement in stress simulation with the same global degrees of freedom used in conventional models. The polygonal elements are constructed of quadratic triangular subelements with appropriate sides constrained to displace linearly. Compatible mesh refinement capability is shown.

Commentary by Dr. Valentin Fuster
1983;():V005T12A014. doi:10.1115/83-GT-156.
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There are many problems facing the designers of turbomachines with the demand for ever increasing capabilities and reliability. One problem that requires considerable attention is the vibration characteristics of some components. It is object of this work to determine the dynamic behavior, namely natural frequencies, mode shapes of a centrifugal impeller which are being important design parameters in order to avoid costly failures in the development phase.

This work divides into three sections. First, a Finite Element structural dynamic analysis is presented. Then experimental procedure used to determine the natural frequencies and mode shapes is described together with the comparison of the results obtained both theoretically through FEM and experimentally.

Finally, interferometric holography technique is used as a means for obtaining the dynamic behavior of the impeller.

Commentary by Dr. Valentin Fuster
1983;():V005T12A015. doi:10.1115/83-GT-158.
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The two methods currently used in industry to calculate blade resonant responses, the energy method and the transmissibility method, are discussed relative to accuracy and facility. Although identical in form for the ideal case, the methods differ in accuracy for practical cases depending on discretization, i.e., model lumped mass breakup fineness. For clarity, the equations for these two methods are derived for a Timoshenko beam and solved numerically for a beam with varying discretization. The results show resonant stress differences up to 30% for higher modes using limited but equal discretization, proving the practical superiority of the energy method over the transmissibility method by example as well as by theory.

Commentary by Dr. Valentin Fuster
1983;():V005T12A016. doi:10.1115/83-GT-167.
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This paper is concerned with the significance of the effects of shear deformation, rotatory inertia and Coriolis forces in the analysis of turbine blade vibrations. Since these are quite pronounced at the high frequency ranges encountered in turbine blade vibration problems, they should not be overlooked although their inclusion paves the way for a complicated nonlinear analysis. An approximate analysis technique is presented which involves an application of the stationary functional method using the normal modes of a discretized model. Numerical results are obtained and discussed. It is noted that a definite advantage of applying this technique to a lumped parameter model is that nonlinear modes higher than the fundamental can also be easily generated.

Commentary by Dr. Valentin Fuster
1983;():V005T12A017. doi:10.1115/83-GT-175.
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Mechanisms simulating rotor joint restoring moments different from the common axisymmetric elastic hinge are derived and their effects on the dynamics of a complete turbomachine are calculated by impressing equivalent perturbing moments. A mechanism for locking subsynchronous whirl to a fractional frequency is described and supporting experimental observations are discussed. Sample analysis shows the possibility of self-sustained synchronous whirl due to preload asymmetry.

Commentary by Dr. Valentin Fuster
1983;():V005T12A018. doi:10.1115/83-GT-176.
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An experimental investigation has been carried out into the influence of side-plate flow restrictors on the performance of a squeeze-film damper bearing. The experimental rig used was a flexible rotor with a disc positioned mid-way between two squeeze-film damper bearings. One of the squeeze-film dampers was fitted with side-plates which could be adjusted and accurately located with respect to the squeeze-film damper journal.

It has been found that the influence of the side-plate clearance on the ability of the squeeze-film damper to reduce the amplitude of the central disc can be considerable if the side-plate clearance is less than the radial clearance. As the side-plate clearance reduces towards zero, the effectiveness of the squeeze-film damper diminishes until the amplitudes obtained are the same as those measured when the rolling-contact bearing is rigidly supported.

An interesting type of precessing elliptical orbit was discovered for conditions where the ‘jump’ phenomenon was operating.

Commentary by Dr. Valentin Fuster
1983;():V005T12A019. doi:10.1115/83-GT-177.
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Fluid inertia forces are comparable to viscous forces in squeeze film dampers in the range of many practical applications. This statement appears to contradict the commonly held view in hydrodynamic lubrication that inertia effects are small. Upon closer inspection, the latter is true for predominantly sliding (rather than squeezing) flow bearings.

The basic equations of hydrodynamic lubrication flow are developed, including the inertia terms. The appropriate orders of magnitude of the viscous and inertia terms are evaluated and compared, for journal bearings and for squeeze film dampers. Exact equations for various limiting cases are presented: low eccentricity, high and low Reynolds number. The asymptotic behavior is surprisingly similar in all cases. Due to inertia, the damper force may shift 90° forward from its purely viscous location. Inertia forces are evaluated for typical damper conditions.

The effect of turbulence in squeeze film dampers is also discussed. On physical grounds it is argued that the transition occurs at much higher Reynolds numbers than the usual lubrication turbulence models predict.

Commentary by Dr. Valentin Fuster
1983;():V005T12A020. doi:10.1115/83-GT-178.
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A number of sophisticated procedures for balancing flexible rotors have been developed during the past two decades. For a variety of reasons, none of these methods has gained general acceptance by practicing balancing engineers. Several of these balancing techniques require a great deal of operator insight and expertise. This has tended to discourage many potential users where this expertise was not already available in-house, particularly where balancing is required as a production operation. In other cases (for example large steam turbines), the machinery owner has had to rely on the manufacturer to provide this balancing expertise when it is needed often resulting in excessive downtime and maintenance costs.

Other balancing methods have been developed which are more systematic so as to reduce the level of expertise required of the user. Unfortunately, these methods have invariably required the collection of large quantities of data and very complex computations. Thus, originally, this data was taken by hand and transcribed for input to a large computer. The results of the balancing calculations were returned some time later for use by the balancing engineer. Such an operation was clearly not conducive to effective commercial application. With the development of minicomputers, the situation was alleviated to a certain extent through the use of more accessible, and even on-line computers to perform these calculations. However even with these minicomputers, in-place flexible rotor balancing facilities were expensive and inconvenient to assemble, and in situ balancing of flexible rotors was impractical if not impossible.

The subsequent development of the microcomputer has made in situ balancing of flexible rotors a possibility. This paper describes a completely portable, microcomputer-based flexible rotor balancing system that uses influence coefficient balancing and the Unified Balancing Approach two of the systematic methods which have been shown to be very effective for balancing flexible rotors. The results of a series of verification tests are also presented.

Topics: Rotors
Commentary by Dr. Valentin Fuster
1983;():V005T12A021. doi:10.1115/83-GT-202.
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The torsional stiffness of a thin walled closed section is many times greater than that of the corresponding open section. The structure consisting of a thin walled open section partially closed along its length by beams is an intermediate case and studies have been carried out to analyze the torsional behavior of such structures. The continuous medium method, in which the intermediate connecting beams are replaced by an equivalent continuous medium, is applied for the torsional analysis. Basically, Vlasov’s theory is applied for the torsional analysis and for the determination of axial warping stresses. Expressions to determine the angle of twist and warping stresses are obtained. Design charts are developed to determine the response for various stiffnesses of intermediate connecting beams. Comparisons between completely open and partially open sections are made for angle of twist and warping stresses. Also, the warping stresses are compared with bending stresses and it is shown that the warping stresses could be very significant.

Commentary by Dr. Valentin Fuster
1983;():V005T12A022. doi:10.1115/83-GT-217.
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This paper treats the free vibration of hollow symmetrical turbo-machinery blades conveying cooling fluid. The blade motion is described by using a simplified shell theory, whereas the fluid forces are described by the linearized potential flow theory. Natural frequencies are presented for the axial and circumferential modes and the effect of flow velocity and other parameters are discussed. Two models are constructed and tested with air and water as the flowing fluid. Also a beam approximation is used to justify the results at least in a qualitative manner. Experimental data and theoretical results are in good agreement and they all show that the fluid flow tends to decrease the free vibration-natural frequencies.

Commentary by Dr. Valentin Fuster
1983;():V005T12A023. doi:10.1115/83-GT-224.
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The use of the stiffness derivative technique coupled with “quarter-point” singular crack-tip elements permits very efficient finite element determination of both stress intensity factors and nodal weight functions. Two-dimensional results are presented in this paper to demonstrate that accurate stress intensity factors and nodal weight functions can be obtained from relatively coarse mesh models by coupling the stiffness derivative technique with singular elements.

The principle of linear superposition implies that the calculation of stress intensity factors and nodal weight functions with crack-face loading, σ(rs), is equivalent to loading the cracked body with remote loads, which produces σ(rs) on the prospective crack face in the absence of crack. The verification of this equivalency is made numerically, using the virtual crack extension technique. Load independent nodal weight functions for two-dimensional crack geometry is demonstrated on various remote and crack-face loading conditions. The efficient calculation of stress intensity factors with the use of the “uncracked” stress field and the crack-face nodal weight functions is also illustrated.

In order to facilitate the utilization of the discretized crack-face nodal weight functions, an approach was developed for two-dimensional crack problems. Approximations of the crack-face nodal weight functions as a function of distance, (rs), from crack-tip has been successfully demonstrated by the following equation:

Display Formula

ha,rs=Aars+Ba+Cars+Dars

Coefficients A(a), B(a), C(a) and D(a), which are functions of crack length (a), can be obtained by least-squares fitting procedures. The crack-face nodal weight functions for a new crack geometry can be approximated using cubic spline interpolation of the coefficients A, B, C and D of varying crack lengths. This approach, demonstrated on the calculation of stress intensity factors for single edge crack geometry, resulted in a total loss of accuracy of less than 1%.

Commentary by Dr. Valentin Fuster
1983;():V005T12A024. doi:10.1115/83-GT-228.
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The safe and reliable operation of high-speed rotating machinery often requires the use of devices that dissipate undesirable rotor vibrations. As an alternative to the more conventional squeeze-film bearing damper designs, a Viton-70 shear-mounted, elastomeric damper was built and tested in a T-55 power turbine high-speed balancing rig. This application demonstrated, for the first time, the feasibility of using elastomers as the primary rotor damping source in production turbine engine hardware. The shear-mounted damper design was selected because of its compatibility with actual gas turbine engine radial space constraints, its accommodation of both the radial and axial thrust loads present in gas turbine engines, and its capability of controlled axial preload. The shear-mounted damper was interchangeable with the production T-55 power turbine roller bearing support so that a direct comparison between the shear damper and the production support structure could be made. Test results showed that the Viton-70 elastomeric damper operated successfully and provided excellent control of both synchronous and nonsynchronous vibrations through all phases of testing to the maximum rotor speed of 1676 rad/s (16,000 rpm). Excellent correlation between the predicted and experienced critical speeds, mode shapes, and log decrements for the power turbine rotor and elastomer damper assembly was also achieved.

Commentary by Dr. Valentin Fuster
1983;():V005T12A025. doi:10.1115/83-GT-229.
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A method is presented for computing the eigenvalues of multicase, coupled, rotating machinery trains. The method is based on a synthesis technique which utilizes generalized receptance formulas, previously derived by the authors. These formulas improve the accuracy of the computed receptances when only an incomplete set of modes is available. A nonsynchronous, gyroscopic, two rotor example is examined to illustrate the synthesis procedure.

Topics: Machinery , Trains
Commentary by Dr. Valentin Fuster
1983;():V005T12A026. doi:10.1115/83-GT-247.
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Squeeze-film dampers are commonly used in gas turbine engines and have been applied successfully in a great many new designs, and also as retrofits to older engines. Of the mechanical components in gas turbines, squeeze-film dampers are the least understood. Their behavior is nonlinear and strongly coupled to the dynamics of the rotor systems on which they are installed. The design of these dampers is still largely empirical, although they have been the subject of a large number of past investigations.

To describe recent analytical and experimental work in squeeze-film damper technology, two papers are planned. This abstract outlines the first paper, Part 1, which concerns itself with squeeze-film damper analysis. This paper will describe an analysis method and boundary conditions which have been developed recently for modelling dampers, and in particular, will cover the treatment of finite length, feed and drain holes and fluid inertia effects, the latter having been shown recently to be of great importance in predicting rotor system behavior. A computer program that solves the Reynolds equation for the above conditions will be described and sample calculation results presented.

Topics: Dampers
Commentary by Dr. Valentin Fuster
1983;():V005T12A027. doi:10.1115/83-GT-248.
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This paper is a companion to “Squeeze-Film Damper Technology, Part 1,” which covered an analytic approach and computer program for squeeze-film damper performance prediction. This paper describes a series of damper tests in which a controlled-orbit rig is used to explore squeeze-film damper behavior for representative gas turbine damper geometries and to verify and calibrate the damper analysis program. Test results for both locally end-sealed (hole fed and drained) and globally sealed (groove fed and drained) dampers are presented, along with performance predictions for those test points made using the software analysis. In particular, the effects of feeder hole flow resistance, feed groove geometry, and fluid inertia on damper performance are discussed and illustrated.

Topics: Dampers
Commentary by Dr. Valentin Fuster

Controls, Diagnostics and Instrumentation

1983;():V005T13A001. doi:10.1115/83-GT-6.
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The advent of large scale integration techniques into electronics has had a dramatic effect on the technology of engine control systems and accompanying this change has been the wider use of digital computational techniques to replace functions previously performed in analogue electronic technology and even by mechanical means. The industry has thereby benefited by smaller and more powerful electronic control systems but at the same time had to deal with costly and potentially difficult to manage technologies associated with the generation of software appropriate for these controllers.

Commentary by Dr. Valentin Fuster
1983;():V005T13A002. doi:10.1115/83-GT-59.
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This paper sets out to present a non-specialist overview of what fault tolerant systems are intended to achieve, the various possible approaches (from simple to complex) which are followed, how well they meet the goals and the particular problems or advantages they possess. The source data for the paper and its background is aviation gas turbine controls but the principles are of general application.

Fault tolerance is aimed at obtaining greater system availability without compromising safety. Many different system configurations have been postulated or tried out. The paper considers 11 and deals in detail with several of them, covering a wide range of cost and complexity. The choice between these diverse systems depends upon application, installation, the powerplant/vehcile configuration and most importantly on the complexity of the control hardware. It involves choices of actuation system, monitoring methods, failure recovery and, in digital systems, software. The paper explains the rationale and the significance of each influence.

Each configuration can be applied more or less successfully to a range of control uses. The discussion indicates which special features are advantageous and which are disadvantageous in different regions of the applications spectrum.

Relative representative cost and reliability figures are given for each configuration and, for aviation types of design, relative sizes and weights.

There is no single, generally applicable “fault tolerant system”. The issues are basically simple but frequently confused. It is the aim of the paper to clearly present these issues and the merits of various configurations in general terms and to promote wider and better informed discussion of them.

Commentary by Dr. Valentin Fuster
1983;():V005T13A004. doi:10.1115/83-GT-97.
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The use of high order languages for writing software for high integrity control applications is aimed to overcome the problems of slow development, lack of visibility and machine dependence in low order languages, assembly codes and machine codes.

But the use of high order languages has failed to overcome the problem of visibility especially on short word-length machines because of difficulties in identifying undesirable characteristics of the machine code generated from the high order language. These characteristics may be due to faults in complex compilers which are intrinsically error-prone; or may be properties of the “correct” operation of a compiler which generates code which may permit unchecked arithmetic overflows or excessive loss of numerical accuracy. Further, these characteristics may change between issues of a compiler and between versions for different processors. This all slows down software development and makes certification difficult.

This paper discusses techniques for overcoming these problems while maintaining the familiarity and visibility of high order languages. A language designed around these techniques and capable of intrinsically safe software development and modification is discussed.

Commentary by Dr. Valentin Fuster
1983;():V005T13A005. doi:10.1115/83-GT-98.
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There are several major factors influencing the development of modern turbomachinery control systems. First, the demand for fuel efficient engines with low emissions creates complex control requirements. Second, unmanned sites or plants where downtime is exceedingly expensive demand controls with high reliability and availability. In addition, there is a desire for controls to be programmable and to have the ability to communicate with data gathering and logging systems.

This paper describes the development and application of a digital control system which answers the above needs.

Commentary by Dr. Valentin Fuster
1983;():V005T13A006. doi:10.1115/83-GT-104.
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Ruston Gas Turbines is a manufacturer of industrial gas turbines. Present models are in the power range 1.3 MW to 6.5 MW, and engine testing is performed on two separate sites, one for acceptance testing of production engines, the other for development testing.

Commentary by Dr. Valentin Fuster
1983;():V005T13A007. doi:10.1115/83-GT-106.
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Greatly improved availability is the primary design goal of the SPEEDTRONTC Mark IV Gas Turbine control. It achieves this goal by distributing control functions among four microcomputers: three are identical control sections, and the fourth handles communications. Powerful on-line diagnostics indicate which section is faulty, down to the replaceable element. Panel repair is effected with the gas turbine running. Mean time to repair is predicted to be three to four hours. The prediction is that the SPEEDTRONIC Mark IV control will not cause a plant shut down more often than once in ten years. In addition, the system has capacity for redundant sensor inputs, which significantly reduces forced outages caused by faulty sensors. Information on how these results were accomplished is presented in the paper, along with a description of the initial experiences running gas turbines with the new system.

Commentary by Dr. Valentin Fuster
1983;():V005T13A008. doi:10.1115/83-GT-144.
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The Station chosen for the trial was Bulls Bridge Gas Turbine Station, sited near London Airport. (See Fig 1-1). Bulls Bridge contains 4, 70 MW sets; each 70 MW unit being powered by 4 Industrial Olympus gas generators, two at either end of a central alternator, (See Fig 1-2). At each end of the alternator, power is supplied via a clutch, to a shaft on which is mounted two power turbines, each driven by a single Olympus gas generator. Thus gas paths are separate between intake and final exhaust, and therefore each gas generator/power turbine assembly can be analysed without being unduly affected by associated plant.

Commentary by Dr. Valentin Fuster
1983;():V005T13A009. doi:10.1115/83-GT-145.
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A generator power system synchronizer, the microsynchronizer was developed specifically for gas turbine generator drives. It provides improved performance and reliability as compared to synchro n izers used in the past, while at the same time it cuts costs of manufacturing and installation. Faster and more accurate synchronizing is achieved by including a speed matching function and utilizing more sophisticated algorithms. Higher reliability is obtained by minimizing parts count, eliminating adjustments, incorporating transient suppression, and designing “failsafe” features. The microsynchronizer was first installed in the field in early 1979, while more than 100 will be in service by the end of 1982.

Commentary by Dr. Valentin Fuster
1983;():V005T13A010. doi:10.1115/83-GT-186.
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The advent of digital microprocessor electronic controls with decision making capabilities and airline interest in improved maintenance has resulted in the incorporation of powerful Built-In-Test-Equipment (BITE) in the latest Garrett gas turbine auxiliary power unit electronic control. BITE has been designed into the control to help isolate defective components and display this information. Garrett historical background and troubleshooting experience was combined with that of the Boeing Company, Messerschimitt-Bolkow-Blohm (MMB), and United Airlines (UAL) to obtain an effective system. Discussion includes BITE design philosophy, how the system functions, and how the information is displayed.

Commentary by Dr. Valentin Fuster
1983;():V005T13A011. doi:10.1115/83-GT-233.
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The use of powerful 16-bit microprocessors and associated components, together with control and sequencing orientated high level languages has enabled flexible and economical turbine control systems to be developed.

This paper describes the architecture, hardware, software and programming methods of a system designed specifically for the control of a range of gas turbines and associated plant.

Commentary by Dr. Valentin Fuster

Education

1983;():V005T14A001. doi:10.1115/83-GT-160.
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Over the history of gas turbine engine development, improvements in engine performance are closely tied to increases in the level of tolerable turbine inlet temperatures. The ability to operate at increasingly high temperatures has been the result of both improvements in materials capability and advances in the art of cooling the hot section components. For propulsion engines and their derivatives the cooling medium is air supplied from the compressor stages, requiring an expense of engine power. The hot section airfoils, particularly the first stage vanes and blades, consume a significant fraction of the total engine cooling air. Designers are continuously faced with the task of making more effective use of the coolant to improve either performance or durability or both. The design process requires detailed knowledge of heat transfer and flow friction characteristics for present and candidate future cooling schemes. Typical current cooling schemes and associated research work directed to future improved designs are discussed.

Commentary by Dr. Valentin Fuster
1983;():V005T14A002. doi:10.1115/83-GT-161.
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Many exciting opportunities to enhance aircraft performance, cost and reliability/availability are rapidly becoming available to the propulsion system designer, with use of digital electronics, information/sensor sharing between airframe systems, and integrated functional designs for propulsion and aircraft flight controls. The propulsion engineer must become an active participant in this area to take full advantage of the advanced technology. In this endeavor, he is faced with the task, which seems to occur all so frequently in a rapidly advancing technology age, of developing new working tools and approaches not normally part of the propulsion engineers experience. A discussion is presented of some key technologies available to the propulsion designer, such as digital electronics, serial data buses, analytical redundancy and avionics standards. Analytical tools in computational fluid flow analysis and modern control theories are reviewed. These tools can be utilized to provide the analytical understanding of the flow characteristics of the propulsion system and to develop the optimal control laws for multivariable, integrated control systems. A design methodology for integrating the propulsion control system with the aircraft controls and avionics systems is presented. The required simulation facilities necessary for the development and checkout of integrated systems are described with examples of their use in advanced research projects.

Topics: Propulsion , Design
Commentary by Dr. Valentin Fuster
1983;():V005T14A003. doi:10.1115/83-GT-197.
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Recent advances in the understanding of turbofan noise generation and suppression in aircraft engines are reviewed with particular emphasis on NASA research. The review addresses each link in the chain of physical processes which connect unsteady flow interactions with fan blades to far field noise. Mechanism identification and description, duct propagation, radiation and acoustic suppression are discussed. Recent advances in the experimental technique of fan inflow control assure that in-flight generation mechanisms are not marked by extraneous sources in static tests. Rotor blade surface pressure and wake velocity measurements aid the determination of the types and strengths of the generation mechanisms. Approaches to predicting or measuring acoustic mode content, optimizing treatment impedance to maximize attenuation, translating impedance into porous wall structure and interpreting far field directivity patterns are illustrated by comparisons of analytical and experimental results. A persistent theme of the review is the interdependence of source and acoustic treatment design to minimize far field noise. Areas requiring further research are discussed and the relevance of aircraft turbofan results to quieting other turbomachinery installations is addressed.

Commentary by Dr. Valentin Fuster

Process Industries

1983;():V005T15A001. doi:10.1115/83-GT-102.
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This paper highlights the results of the co-generation study and construction program of Hollandia-Coevorden, a paperboard mill located in the Netherlands. Selection of equipment based on an analysis of excess air ratio, along with a description of the installation, is presented. Operational experience, including availability and economic benefits, is reviewed, reinforcing their selection, which was based on the principles of minimal maintenance and operational simplicity. An improved performance program is also discussed. The program resulted in a 3.0 MW co-generation facility with a thermal efficiency of 82.5%.

Commentary by Dr. Valentin Fuster

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