Influence of Blade Deterioration on Compressor and Turbine Performance

Gas turbine operating state determination consists of the assessment of the modification, due to deterioration and fault, of performance and geometric data characterizing machine components. One of the main effects of deterioration and fault is the modification of compressor and turbine performance maps. Since detailed information about actual modification of component maps is usually unavailable, many authors simulate the effects of deterioration and fault by a simple scaling of the map itself. In this paper, stage-by-stage models of the compressor and the turbine are used in order to assess the actual modification of compressor and turbine performance maps due to blade deterioration. The compressor is modeled by using generalized performance curves of each stage matched by means of a stage-stacking procedure. Each turbine stage is instead modeled as a couple of nozzles, a fixed one (stator) and a moving one (rotor). The results obtained by simulating some of the most common causes of blade deterioration (i.e., compressor fouling, compressor mechanical damage, turbine fouling and turbine erosion, occurring in one or more stages simultaneously) are reported in this paper. Moreover, compressor and turbine maps obtained through a stage-by-stage procedure are compared to the ones obtained by means of map scaling.

Introduction of the Taurus™ 65 Industrial Gas Turbine for Power Generation

Solar Turbines Incorporated has combined proven technology and product experience to develop the new Taurus 65 gas turbine for industrial power generation applications. The single-shaft engine is designed to produce 6.3 megawatts of electrical power with a 33% thermal efficiency at ISO operating conditions. Selection of the final engine operating cycle was based on extensive aerodynamic-cycle studies to achieve optimum output performance with increased exhaust heat capacity for combined heat and power installations. The basic engine configuration features an enhanced version of the robust Centaur®50 air compressor coupled to a newly designed three-stage turbine similar to the Taurus 70 turbine design. Advanced cooling technology and materials are used in the dry, lean-premix annular combustor, consistent with Solar’s proven SoLoNOx™ combustion technology, capable of reducing pollutant emissions while operating on standard natural gas or diesel liquid fuels. Like the Titan™ 130 and Taurus 70 products, a traditional design philosophy has been applied in development of the Taurus 65 gas turbine by utilizing existing components, common technology and product experience to minimize risk, lower cost and maximize durability. A comprehensive factory test plan and extended field evaluation program was used to validate the design integrity and demonstrate product durability prior to full market introduction.

Analysis of Stall Precursors and Determination of Optimum Signal Processing Methods for an LM-2500 Gas Turbine

This paper presents an analysis of data taken from several stall initiation events on a GE LM-2500 gas turbine engine. Specifically, the time series of three separate pressure signals located at compressor stages 3, 6, and 15 were analyzed utilizing various signal processing methods to determine the most reliable indicator of incipient stall for this engine. The spectral analyses performed showed that rotating precursor waves traveling around the annulus at approximately half of the rotor speed were the best indicators. Non-linear chaotic time series analyses were also used to predict stall, but it was not as reliable an indicator. Several algorithms were used and it was determined that stall wave perturbations can be reliably identified about 900 revolutions prior to the stall. This work indicates that a single pressure signal located at stage 3 on an LM-2500 gas turbine is sufficient to provide advance warning of more than 2 seconds prior to the fully developed stall event.

CBM Integrated Maintenance Scheduler

Condition Based Maintenance (CBM) is a key technology enabling facility maintenance cost reduction. The CBM approach to maintenance replaces rigid time-based maintenance schedules with the “right maintenance at the right time” identified by real-time equipment health monitoring. This approach creates a new requirement for determining the best time to schedule newly identified critical maintenance actions in light of the real world constraints of available labor and resources. One of the major challenges encountered when attempting to optimize a maintenance schedule is related to the resolution of the many and often complex interdependencies or constraints present throughout the maintenance process. This paper presents a CBM decision support software tool that leverages real-time current and future health condition information to optimize maintenance resources, tasking, and planning in order to maximize the system readiness. Over the past year Impact Technologies, under contract by NAVSEA, has been developing technologies that will provide the necessary decision support tools to address this dynamic maintenance environment. The software scheduling tool utilizes an Open Systems Architecture for Condition-Based Maintenance (OSA-CBM) architecture to facilitate implementation into new or legacy systems. The tool employs a generic maintenance model that accounts for equipment reliability attributes, maintenance task material and labor requirements, system dependencies, and subsystems relationships. The focus of the development has been on Naval Ship maintenance, but the model inputs can be adapted to a variety of applications including power generators, aircraft, ships, and production facilities. The core of the decision support tool is a multi-sweep optimization algorithm that is tuned to the maintenance scheduling problem. The algorithm has been designed to achieve the best computational speed. Benefits and risks of maintenance decisions have been quantified in risk, which can be defined in terms of readiness or financial. The probability and consequence of each system failure are considered in light of the complex system interdependencies, such as dependant and redundant systems, to achieve the best overall system readiness. Novel post-processing steps identify the active solution constraints further enhancing the user’s ability to understand the issues that affect system availability.

Clearance Reduction and Performance Gain Using Abradable Material in Gas Turbines

An improvement in the energy efficiency of industrial gas turbines can be accomplished by developing abradable seals to reduce the stator/rotor gap to decrease the tip leakage flow of gases in the hot gas components of the turbine. “ABRANEW” is a project funded by the European Commission aimed at developing a high temperature abradable material capable of controlled abrasion and resistant to erosion and oxidation. In order to define the basic parameters such as the component shape, the existing gap, the expected gap reduction, the seal thickness and other geometric parameters, a comprehensive review of the design of the blade/shroud/casing system was performed.

Gas Turbine Electric Start System (GT-ESS) Ship Integration

The U.S. Navy has incorporated a realm of new technologies into ship warfare in the last few years. This availability has led to advances in ship machinery systems that have enabled the Navy to improve and sustain its mission capabilities. Since 2003, the Navy has worked with manufacturers to develop, test and evaluate a gas turbine electric starter system (GT-ESS) capable of meeting all starting requirements of the General Electric LM2500 marine gas turbine. This engine is used on U.S. Navy Surface Combatants for vessel propulsion. The GT-ESS has also been used to start a newly acquired naval engine from Rolls Royce, the MT30. The GT-ESS has endured extensive test and evaluation at the Land Based Engineering Site (LBES) of the Naval Surface Warfare Center, Carderock Division in Philadelphia, PA. Throughout this time the system has been redesigned as well to comply with more restrictive shipboard requirements. This effort had a direct impact on the packaging of the system. Additional effort has been directed to machinery integration. Full integration of the GT-ESS onto the LM2500 engine entails sharing a common lubrication and cooling loop. This is a challenge for the engine since its lubrication is critical for its service life. It poses a challenge for the GT-ESS since its design must guarantee that the lubrication system will remain free of contamination. The GT-ESS also poses integration challenges for a ship installation. The ideal location of the GT-ESS in the ship is adjacent to the propulsion engine within the machinery room space. Switchboards that provide power to the system are located several decks above the machinery space. Additionally, dedicated power supplies are required to handle the power requirements of the GT-ESS. Thus this power demand calls for an assessment of the power loads onboard ship. This new technology also has an impact on other ship systems. The GT-ESS driver is water cooled and designed to feed from the chill water system of the ship. Its electric motor lubrication has ties with another naval technology (digital fuel control). In turn these two are tied to the lube oil system and conditioning assembly (LOSCA) of the engine. Thus issues of oil pressure, temperature, backpressure, suction, and starvation are addressed and assessed. This paper explores the impact of ship machinery design for ship installation and its impact on other machinery systems as well as ship’s power. It targets proper hardware packaging as a means to achieve a well balanced design for ship application.

Time-Frequency Analysis of Transient Vibrations to Improve Turbo-Compressor Start-Up

Diagnosis of turbo-compressors during start-up is a particularly challenging task. One of the reason is the reduced set of instruments that monitor this procedure. It is cumbersome to adjust lubrication and steam valves while controlling the speed and dynamic stability. In order to get the turbo-compressor out of a high vibration zone, it is important to be able to predict instabilities associated to the start-up process. Thus, it is necessary to have a measurement system with the ability of fault detection, especially at early stages of fault appearance. In this way, the start-up time can be significantly reduced. Although recent developed diagnosis methods use information from different sources and measurements, data structures are not designed to carry predictive information related to the turbo-compressor health. Therefore, it is important to extract early warning signals related to instability conditions. Vibration signals during machine start-up are non-stationary in nature, and conventional techniques, such as Fourier transforms and time series analysis, have difficulties to extract the full features of the vibrations signature. In this paper, the features of start-up vibrations in rotational systems like those found in turbo compressors are investigated by time-frequency analysis, and appropriate analysis of the transient vibration during compressor start-up is presented.

Feasibility Study of Low Grade Heat Recovery Rankine Cycle Using Ozone-Neutral Refrigerant

The paper addresses the feasibility of ozone-neutral low grade heat recovery to produce power. The low grade heat source can either be industrial exhaust or solar radiation. Using a scroll expander as a basis for testing, theoretical models yielded a thermal efficiency of 11%, utilizing a non-toxic and non-hazardous working fluid. This project spanned research and development of a system from the comparison of several working fluids, modeling of a theoretical 10 kW unit, the sizing and selection of appropriate system components, and the development of project management tools, in support of its real world development. A cost benefit analysis of the theoretical system shows that solar heat recovery with ozone-neutral refrigerant is a viable option for power generation, at about 1/3 the cost of a comparable photovoltaic system.

Air Cushion Vehicle Turbofan Propulsion Feasibility Analysis

This paper explores the feasibility of utilizing turbofan gas turbines for combined propulsion and lift on an amphibious air cushion vehicle (ACV). The required thrust and bleed flow were identified, and employed to select possible COTS turbofans for this application. In addition, the turbofan cycle was evaluated for ACV applicability. The investigation revealed that a turbofan configuration would require a new inlet filtration system, which was categorized as high risk. Furthermore, fuel comparisons showed that the turbofan arrangement would require significantly more fuel when compared to the traditional propeller and lift fan system.

Aeroderivative Gas Turbines for LNG Liquefaction Plants: Part 2—World’s First Application and Operating Experience

LNG market pressures for thermally efficient and environmentally friendly LNG plants coupled with the need for high plant availability have resulted in the world’s first application of high performance aeroderivative gas turbines for a 3.7 MTPA LNG plant in Darwin. The six engines utilized are GE PGT25+ engines rated at 32 MW ISO driving propane, ethylene and methane compressors. The paper describes the design, manufacture, testing, and implementation of these units focusing on both the gas turbine and the centrifugal compressors. Power augmentation utilized on these units is also discussed. An overview of operating experience and lessons learned are provided. Part 1 of this paper provides a detailed analysis of why high thermal efficiency is important for LNG plants from an economic and greenhouse gas perspective.