Strategy for Selecting Optimised Technologies for Gas Turbine Air Inlet Filtration Systems

Author(s):  
Stephen D. Hiner

With continuous advances in gas turbine technology, wider breadth of fuel quality burnt and ever growing expectations of; longer life, higher efficiency and reduced maintenance requirements, the filtration of the air entering the gas turbine (GT) has never been more important to meeting its operational requirements. Gas turbines are used throughout the world in an ever increasing diversity of application and environment. This presents a number of challenges to the air filtration system, that require unique solutions for each subset of environment specific challenge, gas turbine platform technology and fuel quality being burnt. This paper discusses the importance of air filtration to a modern GT and how this has changed over time and it’s shifting operational requirements. It explores the challenges facing the air filtration system presented by the different; environments, GT technologies and fuel quality. The paper details what approaches and filtration technologies are currently used to address these challenges, with strengths and weaknesses explained as appropriate, to finally present a strategy for specifying an optimized filtration system to meet the challenges of the modern GT.

Author(s):  
Steve Ingistov ◽  
Michael Milos ◽  
Rakesh K. Bhargava

A suitable inlet air filter system is required for a gas turbine, depending on installation site and its environmental conditions, to minimize contaminants entering the compressor section in order to maintain gas turbine performance. This paper describes evolution of inlet air filter systems utilized at the 420 MW Watson Cogeneration Plant consisting of four GE 7EA gas turbines since commissioning of the plant in November 1987. Changes to the inlet air filtration system became necessary due to system limitations, a desire to reduce operational and maintenance costs, and enhance overall plant performance. Based on approximately 2 years of operational data with the latest filtration system combined with other operational experiences of more than 25 years, it is shown that implementation of the high efficiency particulate air filter system provides reduced number of crank washes, gas turbine performance improvement and significant economic benefits compared to the traditional synthetic media type filters. Reasons for improved gas turbine performance and associated economic benefits, observed via actual operational data, with use of the latest filter system are discussed in this paper.


Author(s):  
T. Zaba ◽  
P. Lombardi

Industrial gas turbines swallow air at a rate of approximately 14 to 16 kg/kWh. Even in clean environments the amount of solid particle ingestion is significant. A 70.000 kW gas turbine operating in a typical residential area could ingest 1.3 to 1.5 kg of solid contaminants in a 24 hour period. The same gas turbine operating in a typical mining or oil field region could ingest 33 to 39 kg of solid contaminants in a 24 hour period. Depending on the composition, size, quantity and condition (wet, dry, sticky) of the ingested particles, performance loss, due to the fouling of the compressor and/or turbine and hardware deterioration, due to erosion, corrosion and/or foreign object damage, can be experienced. To protect against performance loss and hardware deterioration, industrial gas turbines are normally equipped with air inlet filtration systems. However, the effectiveness of the filtration system depends on how well it is matched to the contaminants and site conditions. Matching the filtration system to the contaminants and site conditions is usually a judgement decision based on experience and available information. This paper was written in an effort to enhance the equipment selection process by reviewing BBC’s experience with air inlet filtration systems.


Author(s):  
Peter T. McGuigan

Contaminants are ever-present in the air. Contaminated air entering a Gas Turbine will damage internal components and bring about a reduction in overall efficiency. The amount of contaminant entering a Gas Turbine, therefore, needs to be minimised. This paper describes recent developments in the understanding of one such contaminant, salt. It describes how salt is produced, how it varies climatically and how it varies from location to location and is presented here in the context of the author’s particular field of competence — air filtration system design. Salt ingestion by a Gas Turbine intake can cause corrosion and, given time, can accumulate on the compressor blades and reduce the aerodynamic efficiency. The removal of salt in the air is therefore of primary concern to all those involved in the design and operation of Gas Turbines. Salt removal systems are manufactured in various guises. The concept, however, remains the same — salt capture upstream of the Compressor stage. The drawback to this method of salt removal is that it results in a decrease in air pressure entering the Compressor and will consequently bring about a decrease in the overall system performance. As the requirement to remove more and more salt contaminant increases, the pressure drop across the method of filtration required to achieve this, increases. The responsibility of the Filtration Engineer is therefore to fully understand the requirements of the Gas Turbine, to understand the balance between pressure drop, salt removal and salt size and, consequently, to design an appropriate filtration system — one fit for purpose. Gas Turbines in the marine environment are generally found at heights less than 50m above sea level. It is this environment (the Marine Boundary Layer) which historically has been difficult to fully quantify. Herein lies the problem for those involved — if the environment is not fully understood how can the proper exploitation of the technologies be achieved? Recent developments, however, have led to a better understanding of salt in the Marine Boundary Layer. This paper describes these recent developments.


Author(s):  
Gianluca de Arcangelis

Abstract Traditional air filtration systems for Gas Turbine Naval applications consist of 3 stages: 1st vane separator + pocket filter + 2nd vane separator. The 2nd vane separator is required to drain out droplets formed by the traditional pocket filter during its coalescing function. Further to technological advancements in the water repellency of filter media, as well as leak-free techniques, it is now possible to implement a pocket filter that avoids leaching water droplets downstream. This enables the elimination of the 3rd stage vane separator in the air filtration system. The result is a suitable 2-stage air filtration system. The elimination of the 3rd stage vane separator provides the obvious following advantages: • Reduced pressure drop • Reduced weight • Reduced foot-print • Reduced cost Latest technological advancements in water repellency and high efficiency melt-blown media also allow the attainment of higher performance such as: • Increased efficiency against water droplet and salt in wet state • Increased efficiency against dry salt and dust This results in higher cleanliness of the Gas Turbines with benefits in terms of compressor fouling, compressor blades corrosion and turbine blades hot erosion. Higher performance also results in simplified maintenance as technicians need only focus on the replacement of the elements as opposed to the cleaning and overhauling of the intake duct. The paper goes through the engineering challenges of evolving from a 3-stage to 2-stage filtration system. The paper provides data from testing at independent laboratories with results that back the claims. Furthermore, reference is made to Offshore Oil & Gas installations and testing that have proven successful with independently measured data.


Author(s):  
Jerome Ehrhardt ◽  
Iván Piñeiro

The Landing Craft Air Cushion (LCAC) is the U.S. Navy’s high speed hovercraft used for amphibious landings. The LCAC uses four Allied Signal TF40B gas turbines for propulsion and air cushion lift, and two Sundstrand T-62 gas turbines for auxiliary power. Because of the craft’s low height at sea, the air cushion pressure and the propeller thrust the LCAC generates a high volume of sea spray, dust and airborne beach sand during its amphibious mission. For what can be considered the most severe environment of any U.S. NAVY gas turbine application, a combustion air system was designed to efficiently remove the airborne contaminants of seawater, salt and sand. This paper discusses the design, developmental testing, fleet experience and improvements for the LCAC gas turbine combustion air inlet system.


Author(s):  
Thomai Gastopoulos ◽  
Joseph Lawton

The Auxiliary Ships and New Acquisition Support Branch (Code 425) of the Naval Surface Warfare Center, Philadelphia Division conducted a study to assist the Marine Corps Systems Command in assessing the feasibility of using a gas turbine engine as a propulsion system on future United States Marine Corps Amphibious Combat Vehicles (ACV). The study was focused on developing and testing a gas turbine intake solution for the ACV that can remove saltwater from the intake airstream of a notional 3,000 horsepower ACV engine. Code 425 developed a two-part solution for the intake of the ACV. The first part of the solution is an intake shroud designed to elevate the intake to protect the engine from deck water wash. The second part of the solution is the Combustion Air Separation System (CASS), a gas turbine intake filtration system designed to remove marine contaminants that enter the intake. Code 425 tested a CASS prototype for its efficiency at removing saltwater spray and bulk water up to 10 gallons per minute. Test results showed that the CASS met each requirement and that an ACV intake system incorporating both the intake shroud and the CASS should protect the gas turbine engine from saltwater ingestion.


Author(s):  
A. Cavarzere ◽  
M. Venturini

The growing need to increase the competitiveness of industrial systems continuously requires a reduction of maintenance costs, without compromising safe plant operation. Therefore, forecasting the future behavior of a system allows planning maintenance actions and saving costs, because unexpected stops can be avoided. In this paper, four different methodologies are applied to predict gas turbine behavior over time: Linear and Non Linear Regression, One Parameter Double Exponential Smoothing, Baesyan Forecasting Method and Kalman Filter. The four methodologies are used to provide a prediction of the time when a performance limit will be exceeded in the future, as a function of the current trend of the considered parameter. The application considers different scenarios which may be representative of the trend over time of some significant parameters for gas turbines. Moreover, the Baesyan Forecasting Method, which allows the detection of discontinuities in time series, is also tested for predicting system behavior after two consecutive trends. The results presented in this paper aim to select the most suitable methodology that allows both trending and forecasting as a function of data trend over time, in order to predict time evolution of gas turbine characteristic parameters and to provide an estimate of the occurrence of a failure.


Author(s):  
Dieter Bohn ◽  
James F. Willie ◽  
Nils Ohlendorf

Lean gas turbine combustion instability and control is currently a subject of interest for many researchers. The motivation for running gas turbines lean is to reduce NOx emissions. For this reason gas turbine combustors are being design using the Lean Premixed Prevaporized (LPP) concept. In this concept, the liquid fuel must first be atomized, vaporized and thoroughly premixed with the oxidizer before it enters the combustion chamber. One problem that is associated with running gas turbines lean and premixed is that they are prone to combustion instability. The matrix burner test rig at the Institute of Steam and Gas Turbines at the RWTH Aachen University is no exception. This matrix burner is suitable for simulating the conditions prevailing in stationary gas turbines. Till now this burner could handle only gaseous fuel injection. It is important for gas turbines in operation to be able to handle both gaseous and liquid fuels though. This paper reports the modification of this test rig in order for it to be able to handle both gaseous and liquid primary fuels. Many design issues like the number and position of injectors, the spray angle, nozzle type, droplet size distribution, etc. were considered. Starting with the determination of the spray cone angle from measurements, CFD was used in the initial design to determine the optimum position and number of injectors from cold flow simulations. This was followed by hot flow simulations to determine the dynamic behavior of the flame first without any forcing at the air inlet and with forcing at the air inlet. The effect of the forcing on the atomization is determined and discussed.


Author(s):  
Stian Madsen ◽  
Lars E. Bakken

Gas turbine performance has been analyzed for a fleet of GE LM2500 engines at two Statoil offshore fields in the North Sea. Both generator drive engines and compressor driver engines have been analyzed, covering both the LM2500 base and plus configurations, as well as the SAC and DLE combustor configurations. Several of the compressor drive engines are running at peak load (T5.4 control), and the production rate is thus limited to the available power from these engines. The majority of the engines discussed run continuously without redundancy, implying that gas turbine uptime is critical for the field’s production and economy. Previous studies and operational experience have emphasized that the two key factors to minimize compressor fouling are the optimum designs of the inlet air filtration system and the water wash system. An optimized inlet air filtration system, in combination with daily online water wash (at high water-to-air ratio), are the key factors to achieve successful operation at longer intervals between offline washes and higher average engine performance. Operational experience has documented that the main gas turbine recoverable deterioration is linked to the compressor section. The main performance parameter when monitoring compressor fouling is the gas turbine compressor efficiency. Previous studies have indicated that inlet depression (air mass flow at compressor inlet) is a better parameter when monitoring compressor fouling, whereas instrumentation for inlet depression is very seldom implemented on offshore gas turbine applications. The main challenge when analyzing compressor efficiency (uncorrected) is the large variation in efficiency during the periods between offline washes, mainly due to operation at various engine loads and ambient conditions. Understanding the gas turbine performance deterioration is of vital importance. Trending of the deviation from the engine baseline facilitates load-independent monitoring of the gas turbine’s condition. Instrument resolution and repeatability are key factors for attaining reliable results in the performance analysis. A correction methodology for compressor efficiency has been developed, which improves the long term trend data for effective diagnostics of compressor degradation. Avenues for further research and development are proposed in order to further increase the understanding of the deterioration mechanisms, as well as gas turbine performance and response.


2015 ◽  
Vol 22 (4) ◽  
pp. 53-58 ◽  
Author(s):  
Zygfryd Domachowski ◽  
Marek Dzida

Abstract The use of inlet air fogging installation to boost the power for gas turbine engines is widely applied in the power generation sector. The application of fogging to mechanical drive is rarely considered in literature [1]. This paper will cover some considerations relating to its application for gas turbines in ship drive. There is an important evaporative cooling potential throughout the world, when the dynamic data is evaluated, based on an analysis of coincident wet and dry bulb information. This data will allow ships’ gas turbine operators to make an assessment of the economics of evaporative fogging. The paper represents an introduction to the methodology and data analysis to derive the direct evaporative cooling potential to be used in marine gas turbine power output loss compensation.


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