Laboratory tests of catalytic combustors with distillate fuel have achieved ultra low NOx formation at catalytic reactor exit temperatures and combustion efficiencies consistent with state-of-the-art gas turbine requirements. Concomitant with these features, however, are design limitations such as narrow turn down range and unique reactor mounting requirements. This paper presents fully analyzed conceptual design solutions to these problems within the constraints of fixed geometry, full catalytic combustion over 80% of the turbine load range, and retrofit to an existing gas turbine. The combustor design incorporates (a) a gutter stabilized pilot burner downstream of the reactor for operation from ignition to full speed no load, (b) a segmented fuel-air preparation system for fuel staging of the reactor, (c) a reactor mounting system which accommodates thermal growth and start-up and shutdown transients, and (d) a graded cell reactor. These features were achieved while maintaining low reactor face velocities and system pressure drops.
Almost all process compressors manufactured today are built in accordance with the fixed geometry modular system. It is not always possible to accurately predict the operational behaviour of a compressor particularly in such cases where a deviation from the standard solution is advisable or even necessary. This paper describes and analyses by means of experimental measurements the influence of three different stage modifications (axial stage pitch, shortening of the vaneless annular diffusor, blading cut-back). The results given here are directly related to engineering practice as they enable the design engineer to apply realistic efficiencies even for modified stages in the early planning stage.
An experimental program was conducted in a highly loaded, single-stage, low-speed research compressor that featured variations in blade tip clearances, shroud wall roughness, and stage loading levels. The results showed that tip clearances and stage loading levels exerted a very strong influence on casing boundary layer growth. Shroud wall roughness not only showed some effect on casing boundary layer development, but also influenced stage stall margin. The results point out the need to understand the basic flow processes that occur if realistic mathematical models are to be developed so that casing boundary layer development and its influence on compressor stage performance can be accurately predicted.
Rocketdyne is under contract to DOE for the development of heat-exchanger technology that will allow coal to be burned for power generation and cogeneration applications. This effort involves both atmospheric fluidized bed and pulverized coal combustion systems. In addition, the heat-exchanger designs cover both metallic and ceramic materials for high temperature operations. This paper reports on the laboratory and small AFB test results completed to date. It also covers the design and installation of a 6 × 6 ft-atmospheric fluidized bed test facility being used to correlate and expand the knowledge gained from the initial tests. The paper concludes by showing the direction this technology is taking and outlining the steps to follow in subsequent programs.
An earlier study demonstrated the theoretical potential of the concept of injecting methanol into a gas turbine compressor inlet as a means of increasing cycle thermal efficiency. To attain the full potential of such a system, continuous shifting vapour/liquid equilibrium is required which would pose formidable difficulties in practice due to the presence of liquid in the compressor blading. This study evaluates a more practicable configuration in which the alcohol is injected between stages of a multistage machine so that, due to the higher air temperatures, evaporation is complete before the mixture enters subsequent stages. Through a computer analysis, it is shown that this arrangement would retain most of the potential of the concept while greatly reducing the design and operating problems.
Shop performance tests were conducted on a four-stage industrial centrifugal compressor. The first stage consisted of a radial plenum inlet, an open inducer type impeller with high hub/tip ratio and radial exit blades, a short vaneless diffuser, and a scroll including a conical diffuser. These stages with high flow coefficients and high tip speed Mach numbers are sometimes used as a first stage with multistage process compressors to increase the volumetric capacity of the given casing and reduce the number of stages. We have four versions of the vaneless diffuser with a radius ratio of 1.46: wide parallel walled, narrow parallel walled, constant area tapered, and reduced area tapered. The influence of these modifications was tested within a tip speed Mach number range of 0.94 to 1.07. Improvement of turn-down was obtained by narrowing and tapering. But the two extremely narrow diffusers reduced the rated point efficiencies beyond acceptable limits. The wide parallel walled diffuser has the highest efficiency and the most unfavorable surge, whereas the constant area diffuser achieved 10 percent better surge without practically any detrimental effects on efficiency.
Gas turbines furnished with heat recovery equipment generally have maximum cycle efficiency when the gas turbine is operated at its ambient capability. At reduced gas turbine output the cycle performance can fall off rapidly as gas turbine exhaust temperature drops, which reduces the heat recovery equipment performance. This paper reviews the economic gains which can be realized through use of several control modes which are currently available to optimize the cycle efficiency at part load operation. These include variable inlet guide vane (VIGV) control for single-shaft units, and combined VIGV and variable high-pressure set (compressor) speed control for two-shaft units. In addition to the normal control optimization mode to maintain the maximum exhaust temperature, a new control mode is discussed which allows airflow to be modulated in response to a process signal while at constant part load. This control feature is desirable for gas turbines which supply preheated combustion air to fired process heaters.
A new method is derived to calculate unbalance response of a complete turbomachine, including mount asymmetry, disk flexibility, and fluid-film bearing anisotropy by utilizing conventionally obtained stiffness coefficients for the rotor and stator. Formulation through the coordinates whirl and whip is in real variables with only eight equations per bearing. Whereas the stator is usually ignored, sample analysis illustrates possible strong influence of casing flexibility. Coordinate transformations to enhance visualization and verification of the solution are shown.
The design and development of a water-cooled high temperature gas turbine has been under active investigation by the General Electric Gas Turbine Division for the past 15 years. The transition from testing small scale, laboratory-size experimental hardware to full scale industrial gas turbine components was initiated in 1975 by General Electric and extended further under the U.S. Department of Energy’s High Temperature Turbine Technology (HTTT) program. A key element in this transition was the identification of a composite (hybrid) design for the first stage nozzles. This design permits efficient heat transfer to the water-cooling passageways, thus lowering effective strains and increasing part life. This paper describes the metallurgical considerations and process technology required for such hardware. A review of the materials selection criteria utilized for the nozzle is presented, along with the results of several materials development programs aimed at determining metallurgical compatibility of the component materials, diffusion bonding behavior and both hot corrosion and aqueous corrosion performance of key materials. A brief description of the actual cascade testing of the part is given, along with results of a post-test metallurgical analysis of the tested hardware.
An empirically based engine simulation model was developed to analyze the operation of a heavy-duty gas turbine on ash-bearing fuel. The effect of the ash in the combustion products on turbine efficiency was determined employing field data. The model was applied to the prediction of the performance of an advanced-cooled turbine engine with a water-cooled first-stage nozzle, when operated with ash-bearing fuels. Experimental data from a turbine simulator rig were used to estimate the expected rates of ash deposit formation in the advanced-cooled turbine engine, so that the results could be compared with those for current engines. The results of the simulations indicate that the rate of decrease in engine power would be 32 percent less in the advanced-cooled engine with water cooling. An improvement in predicted specific fuel consumption performance was also noted, with a rate of increase of 38 percent for the advanced-cooled engine.
Experimental data obtained in heavy fuels operation of a gas turbine simulator with a water-cooled, transonic turbine nozzle cascade are presented. The ash fouling is characterized by the rate of decrease of the aerodynamic throat area. Particular attention is given to the cleanability of the ash deposits. A simple heat transfer analysis was performed to assist in evaluating the data. The rate of ash fouling in the water-cooled nozzle was found to be of the same order of magntude as for conventional air-cooled designs. Cleanability, both on and off-line, was found to be significantly enhanced, thus making the water-cooled gas turbine an attractive alternative for heavy fuels applications.
This paper describes short duration heat transfer measurements on a flat plate and a gas turbine nozzle airfoil at high free-stream temperatures. A shock tube generated the high-temperature and pressure air flow. Thin-film heat gages recorded the surface heat flux. The flat plate was tested both in the shock tube and in a shock tunnel placed aft of the tube. Shock tunnel tests on the nozzle airfoil measured the local heat transfer distribution. The flat plate free-stream temperatures varied from 830°R (460 K) to 3190°R (1770 K) for a Tw/TT, g temperature ratio of 0.17 to 0.64 at Mach numbers from 0.12 to 1.34. The nozzle measurements at a Tw/TT, g of 0.35 to 0.39 generally indicate that pressure (concave) surface heat transfer coefficients are high, whereas the suction (convex) surface shows much lower heat transfer coefficients than a turbulent flat-plate correlation.
The U.S. Department of Energy LMFBR Lines-of-Assurance are briefly stated and local faults are given perspective with an historical review and definition to help define the constraints of LMFBR fuel-element designs. Local-fault-propagation (fuel-element-failure propagation and blockage propagation) perceptions are reviewed. Fuel pin designs and major LMFBR parameters affecting pin performance are summarized. The interpretation of failed-fuel data is aided by a discussion of the effects of nonprototypicalities. The fuel-pin endurances expected in the United States, USSR, France, UK, Japan, and West Germany are outlined. Finally, fuel-failure detection and location by delayed-neutron and gaseous-fission-product monitors are briefly discussed to better realize the operational limits.
This paper develops a nonlinear ordinary differential equation (O.D.E.) of motion for a disk parallel to a flat plate and levitated by incompressible laminar flow of fluid supplied from a central orifice. The fluid's inertia, reflected in high mass flow rates, is accounted for. The transient flow velocity and pressure field are found by iterative integration of the Navier-Stokes equation to determine the O.D.E. for the time-dependent height of the disk (or fluid film thickness). The film thickness is found by not only numerically integrating the O.D.E., but also by linearizing the equation to obtain a closed-form solution. The results of this combined squeeze film, source-flow case compare favorably with experimental data presented which span cases from negligible inertia (viscous dominance) to cases of inertia dominance. Fortunately, the closed-form solution differs only slightly from the numerical solution; this provides relatively accurate expressions for the frequencies and damping coefficients in terms of the geometry, load (or weight of disk), mass flow rate, and the fluid properties.
Case-by-case reviews of selective world experience with severe local faults, particularly fuel failure and fuel degradation, are reviewed for two sodium-cooled thermal reactors, several LMFBRs, and LMFBR-fuels experiments. The review summarizes fuel-failure frequency and illustrates the results of the most damaging LMFBR local-fault experiences of the last twenty years, beginning with BR-5, and including DFR, BOR-60, BR2’s MFBS-and Mol-loops experiments, Fermi, KNK, Rapsodie, EBR-II, and Treat-D2. Local-fault accommodation is demonstrated and a need to more thoroughly investigate delayed-neutron and gaseous-fission-product signals is highlighted in view of uranate formation, observed blockages, and slow fuel-element failure-propagation.
A great deal of published literature exists which analyzes the free vibrations of turbomachinery blades by means of one-dimensional beam theories. Recently, a more accurate, two-dimensional analysis method has been developed based upon shallow shell theory. The present paper summarizes the two types of theories and makes quantitative comparisons of frequencies obtained by them. Numerical results are presented for cambered and/or twisted blades of uniform thickness. Significant differences between the theories are found to occur, especially for low aspect ratio blades. The causes of these differences are discussed.
An experimental apparatus was used to simulate the annular crevice formed by a heated tube and drilled tube support plate (TSP) in a pressurized water reactor recirculating steam generator. The aim of the experiment was to explore the conditions required for the formation and maintenance of a dry region. Water at 0.69 MPa or atmospheric pressure was circulated through the crevice. Visual observations and tube wall temperature measurements were obtained and compared to synthesize a description of the crevice boiling processes. It was determiend that a stable dry patch exists about a line of contact between tube and TSP above a wall superheat of 2–3°C. However, separating the tube and TSP by about 0.025 mm allows the dry patch to be rewet.
Two-phase transpiration is shown to possess considerable potential for gas turbine cooling. In this concept, water fed into a porous component boils within the wall. The resulting steam issues from the hot surface forming the transpiration film. A model for the performance of such a system is developed. Assuming constant properties and a linear reduction of Stanton number with transpiration rate, closed-form solutions are obtained. The governing dimensionless parameters are identified, the system behavior predicted, and the modes of operation delineated. Those are defined as two-phase, partially-flooded, and completely-flooded modes. At low values of a certain “modified Peclet number,” the two-phase mode is unstable and the system tends to flood. Large values of this parameter indicate stable, well-regulated behavior. Discussions on gas turbine applications are presented. A typical numerical example is given in the Appendix.
