A Reheat Gas Turbine Oilfield Cogeneration System, Fueled With Heavy Crude Oil, Which Produces Very Low NOx Emissions

A gas turbine cogeneration system is described that offers fuel flexibility plus substantially reduced NOx emissions without water injection or selective catalytic reduction (SCR). The entirely new turbine design developed by TurboEnergy Systems permits boiler repowering and other cogeneration applications. The first application will be in the California heavy oilfields; the system will be retrofitted to an existing 50 million btu/hr oilfield steam generator used in thermally enhanced oil recovery. The turbine, rated at 1250 kw (site output), was sized to match the combustion air flow requirements of the steam generator. A reheated design was selected to maximize power output from the limited airflow available and to maximize the exhaust temperature for cogeneration and industrial process applications. The oilfield cogeneration system being developed includes a new heavy oil burner for the steam generator which will be fired on the high temperature exhaust from the turbine. The system will also provide low NOx emissions, below the tightest projected standards in Kern County, which has a large concentration of heavy oilfields. Both the turbine and the steam generator burner will burn heavy (API 13 gravity) crude oil. The paper describes the overall system, its interface with the existing process, the design techniques used, and presents performance projections. Field testing will begin at a site near Bakersfield, California, starting in early to mid-1987.

Rainbow Field Test of Coatings for Hot Corrosion Protection of Gas Turbine Hot Section Components

The work described in this paper was conducted under Electric Power Research Institute (EPRI) Contract RP 2465, “Rainbow Test of Advanced Coatings for Gas Turbine Blades and Vanes”. A field test of a rainbow rotor and nozzle was carried out to establish the hot corrosion protection of various aluminide and MCrAlX (X = Y, Hf) overlay coatings on first stage blades and nozzles of a Centaur gas turbine operating in Valera, Venezuela. The blade coatings included both simple and precious metal aluminides, Electron Beam-Physical Vapor Deposition (EB-PVD) coatings and Low Pressure Plasma Spray (LPPS) coatings on Inconel-738LC, Inconel-792 and MAR-M421 substrates. The turbine nozzle vanes were coated by similar methods on FSX-414 and MAR-M509 substrates. Field testing was performed under industrial conditions where the continuous duty engine, used for power generation, ran on a liquid fuel contaminated with sodium and sulfur. The engine test was terminated after nearly 8,000 hours of operation. Visual examination and micro-structural analysis indicated that EB-PVD and LPPS overlay coatings were more effective than simple and modified aluminides for hot section hot corrosion protection. The protection of overlay coatings on nozzle airfoils was found to increase with their chromium content.

Characterization of the Multiaxial States of Stress in an Uncooled Gas Turbine Blade

The assessment of fatigue-creep life of hot engine components either using conventional safe life design approach or damage tolerant design concepts require the computation and evaluation of the stress-strain-temperature-time cycles corresponding to the operational sequences. For typical jet engine operations the temperature and elastic stress-strain states for an uncooled turbine blade were calculated using finite elements. A primary concern was the aspect of multiaxiality and associated non-proportionality. The results are discussed in regard to multiaxial equivalent damage concepts.

A Model to Determine the Behaviour of a Pressure Measurement Equipment During Non-Static Operations of Gasturbine Engines

For some time there have existed different approaches and models by various authors to describe the behaviour of gasturbines during the transition between different operating points. A problem that has not been solved satisfactorily so far is the verification of these models with the help of exact data. Quite often one notices that the instruments do not react properly to the processs they are measuring: there is a time lag and the measured values become distorted by the measuring facility. This paper is a contribution to the adjustments on gasturbine engines during non-static operations. A mathematical model has been developed to determine the influence of the different components on the measuring chain, which consist of a pressure measuring transducer with high natural frequency on a semiconductor base, a hose pipe and a pressure probe. This model has been verified by pressure measurements with a calibrating device. The final part is the discussion of the pressure values, which were measured on a gasturbine engine during the transition between different operating points and adjusted with the help of the mathematical model for the measuring chain.

A Triplex Fault Tolerant Digital Control

Reliability is becoming more important as turbomachinery applications become more complex and as competition becomes more intense. This paper describes a fault tolerant control system that offers the needed reliability. Both the hardware and software are discussed. An application of the control on a Westinghouse 501 gas turbine is noted.

The HF “Fluoride-Ion” Cleaning Technique for Superalloys

Fluoride-ion cleaning, using Hydrogen Fluoride gas as the active agent, is rapidly becoming established as a cost effective method to prepare nickel and cobalt based superalloys for braze repair. Background and comparative information on the four basic processes currently in use are discussed. The latest process using hydrogen fluoride gas directly is described in detail including the methods used for precise process control and safe handling of the HF input gas, as well as the off-gas fluoride compounds. Alloys successfully prepared for braze repair are listed. Other uses for the process and potential uses for the manufacture of new components are suggested.

A Diagnosis of Failure of a Compressor Blade

The methodology and the procedure of diagnosis of a cracked stationary blade of a compressor due to high cycle fatigue is presented. The natural frequencies of the blades and a stator row were measured and an analysis of the casing vibrations during start-up and under load conditions of the compressor was conducted in a search for the cause of the failure. Using finite element code the natural frequencies and the vibratory stresses of the stator row blades (vanes) were computed. The computed maximum vibratory stresses in the vane were concentrated in the location of the crack which originated from the welded joint. It was concluded that the welded joint requires modification.

Localization of Natural Modes of Vibration in Bladed Disks

A study is presented of the mode localization phenomenon in imperfect blade-disk and blade-shroud-disk assemblies. This surprising phenomenon, first discovered in solid state physics, occurs in a number of periodic structures when the periodicity is broken by disorder or imperfections. Localization is signalled by the amplitude of a global blade-disk mode becoming confined to one or more local regions consisting of just a few blades, and could have serious implications for blade fatigue life. The results of this investigation indicate that unshrouded blades mounted on stiff disks are especially susceptible, and even small blade imperfections within manufacturing tolerances are likely to trigger mode localization. Increasing the interblade coupling by adding shrouds or reducing the disk stiffness greatly reduces the localization susceptibility, although certain modes may still become localized if the shrouds are free to slip.

Performance and Reliability Improvements for Heavy Duty Gas Turbines

Many significant advances in technology have been applied to new unit production in the past 15 years. These technology improvements can be applied to field units to achieve increased performance, life, and/or reliability. Several types of improvement are now available for compressors, combustion systems, hot gas path turbine parts, and turbine controls. This paper provides a summary of performance improvements available for General Electric gas turbines MS3002, MS5001, MS5002, MS6001, MS7001, and MS9001 and tabulations of performance for each improvement. Also provided are detailed descriptions of control modernization designs available for improving the operating reliability of field units.

New Materials for Fabricated Gas Turbine Hot Section Components

Materials have been developed in recent years which are particularly well-suited for use in fabricated gas turbine hot section components. Among these are HAYNES® alloy No. 230 and HASTELLOY® alloy S. These alloys combine very good performance characteristics with capability for fabrication into such complex components as combustion chambers, afterburner flameholders, seal rings, and thermocouple/probe assemblies. The properties and fabrication characteristics of these two materials are reviewed and compared with other well-known gas turbine alloys.