bluuebunny/crossref_metadata_2025 huggingface dataset:
The Unsteady Development of a Turbulent Wake Through a Downstream Low-Pressure Turbine Blade Passage
Authors: Stieger R. D. , Hodson H. P.
Published: November 2008

This paper presents two-dimensional LDA measurements of the convection of a wake through a low-pressure (LP) turbine cascade. Previous studies have shown the wake convection to be kinematic but have not provided details of the turbulent field. The spatial resolution of these measurements has facilitated the calculation of the production of turbulent kinetic energy and this has revealed a mechanism for turbulence production as the wake convects through the bladerow. The measured ensemble-averaged velocity field confirmed the previously reported kinematics of wake convection while the measurements of the turbulence quantities showed the wake fluid to be characterised by elevated levels of turbulent kinetic energy (TKE) and to have an anisotropic structure. Based on the measured mean and turbulence quantities, the production of turbulent kinetic energy was calculated. This highlighted a TKE production mechanism that resulted in increased levels of turbulence over the rear suction surface where boundary layer transition occurs. The turbulence production mechanism within the bladerow was also observed to produce more nearly isotropic turbulence. Production occurs when the principal stresses within the wake are aligned with the mean strains. This coincides with the maximum distortion of the wake within the blade passage and provides a mechanism for the production of turbulence outside of the boundary layer.
Surge Avoidance in Gas Compression Systems
Authors: Kurz R. , White R. C.
Published: November 2008

The phenomenon of compressor surge and its prevention have drawn significant attention in the literature. An important aspect of surge avoidance lies in the design of the compressor station and, in particular, the piping upstream and downstream of the compressor. Most anti-surge systems are perfectly capable of avoiding surge during normal operating conditions. However, unplanned emergency shutdowns present a significant challenge, and surge avoidance in these cases depends to a large degree on the station layout. In this paper, data from a compressor that surged during an emergency shutdown are presented. The data are analyzed to determine the effects of surge and the rate of deceleration. A model to simulate shutdown events is developed and used to develop simpler rules that help with proper sizing of upstream and downstream piping systems, as well as the necessary control elements. The compression system is analyzed, thus verifying the model and the simplifications.
Enhancement of Mixing Effectiveness in Skewed Streams
Authors: Deinert B. , Hourmouziadis J.
Published: November 2008

Forced mixers are used to improve the performance (thrust and SFC) and to reduce jet-mixing noise of turbofan engines. Therefore every effort has been made to enhance the mixing from forced exhaust mixers. A lobed type of forced mixer induces rapid mixing by enhancing the streamwise vorticity and increasing the interfacial area. Lobed mixer effectiveness can be further enhanced through the introduction of smaller scale mixing devices. For the design of these mixing devices it is important to keep in mind, that the devices have to produce smaller scale vorticity, but with an acceptable pressure loss. Several investigations have been reported on mixing enhancement in a plane shear layer and in wake flows using tabs. One important result was that each tab produces a dominant pair of counter-rotating streamwise vortices with a rotational direction opposite to that of the vortices generated by the induced upstream stagnation field (horseshoe vortex). Due to the high relevance for many engineering applications such as for the mixing processes behind lobed exhaust mixers in turbojet engines, the present investigation also considers skewed streams with delta tabs. In an attempt to explain the basic flow behaviour downstream of a mixing device in a constant skewed stream, qualitative and quantitative measurements have been carried out. The experiments are carried out in a low-speed test facility, which generates a two-stream skewed flow at different angles. This investigation considers the evolution of coherent structures and the characteristic flow field of parallel and skewed streams generated by mixing devices in the form of delta tabs (triangular-shaped tabs with their apex leaning downstream). Later on the results of this study are to be applied to the design of mixing devices introduced on a lobed mixer. One significant result of these experimental investigations in skewed streams is that each tab generates a pair of counter-rotating streamwise vortices with the same rotational direction as in the unskewed stream, but both vortices are not equally strong. This is caused by the fact that the pressure field ceases to be symmetric upstream of the tab. Farther downstream, the wake flow appears to be wrapped around the stronger vortex.
Experimental Operating Range Extension of a Twin-Spool Turbofan Engine by Active Stability Control Measures
Authors: Scheidler Stephan G. , Fottner Leonhard
Published: November 2008

Modern engine operation is guided by the aim to broaden the operating range and to increase the stage loading allowing the stage count to be reduced. This is possible by active stability control measures to extend the available stable operating range. Different strategies of an active control system like air injection and air recirculation have been applied. While in the past mainly results have been published regarding the stability enhancement of compressor rigs or single-spool engines, this experimental study focuses as well on the stability as also on the operating range extension of a twin-spool turbofan engine as an example for a real engine application on an aircraft. The objective of this investigation is the analysis of the engine behavior with active stabilization compared to not supported operation. For this purpose high frequency pressure signals are used and analyzed to investigate the effects of air injection with respect to the instability onset progress and the development of any instabilities like rotating stall and surge in the LP Compression system. These Kulite signals are fed to a control system. Its amplified output signals control fast acting Direct Drive Valves circumferentially distributed ahead of the LPC. For the application of air injection described in the paper, the air is delivered by an external source. The control system responsible for air injection is a real-time system which directly reacts on marked instabilities and their pre-cursors. It allows the LP Compression System to recover from fully developed rotating stall by asymmetric air injection based on the pressure signals. Additionally, a delayed appearance of instabilities can be provoked by the system. Air injection guided by this control system resulted in a reduction of the required amount of air compared to constant air injection. Also, disturbances travelling at rotor speed can be detected, damped and eliminated by this control system with a modulation of the injected air in such a way that the injection maximum travels around the 10 injection positions.
Aerothermal Investigations on Turbine Endwalls and Blades (AITEB)
Authors: Haselbach F. , Schiffer H. P.
Published: November 2008

This paper delivers an overview on the European research project AITEB (Aerothermal Investigations on Turbine Endwalls and Blades), which started in year 2000 in the course of the 5th Framework Programme (GROWTH). The project shall deliver an integrated technology and design tool package for the advanced, aerothermal highly loaded design of turbine endwalls and blades. It focuses on the following technical tasks : A) Heat transfer/cooling in separated flow areas: Experimental and numerical investigation of heat transfer and film-cooling in separated flow for highly loaded blades including advanced trailing edge cooling (Work Package 1&2). B) Heat transfer/ improved cooling of turbine endwalls: Experimental and numerical work on heat transfer and cooling of turbine endwalls (Work Package 3, 4 & 5). These work packages comprise new technologies for passive shroud cooling and unshrouded blade tip groove cooling. C) Optimised CFD-process, which aims to validate and optimise the whole CFD-process (drawing-grid-modelling-postprocessing-risk assessment) in order to derive the,, best practice” for engineers to use CFD as a risk reduction and time effective tool. (WP6) Experimental results of test series at various test sites are presented and compared to numerical simulations of the eight industrial partners (Rolls-Royce Deutschland (co-ordinator), ALSTOM Power, Avio, ITP, MTU Aero Engines, Turbomeca, Volvo Aero Corp., Snecma Moteurs) and eight research establishments and Universities (DLR, VKI, Univ. of Cambridge, Univ. of Karlsruhe, Univ. of Florence, Univ. of German Armed forces Munich, Polisch Academy of Science, Techn. Univ. of Berlin). Key results of AITEB are in the development of physical understanding and validation of CFD for aerothermal purposes in the area of complex and separated flows. Furthermore, in case of tip regions of blades (either shouded or shroudless) existing cooling technologies are investigated in order to derive a basis for an optimization of the specific cooling technology.
Detecting and Evaluating Deterioration in Compression Equipment by Monitoring Deviations From Expected Performance
Authors: McKee Robert J. , Smalley Anthony J. , Bourn Gary D. , Young Kenneth N. , Treuhaft Martin B.
Published: November 2008

This paper presents a method for detecting deterioration of turbomachinery in pipeline service. Many pipeline compressors have data logging systems, but do not fully exploit the resulting data. This paper describes a method to predict how expected values for turbomachinery performance parameters vary with conditions, and provides options for assessing the severity of deviations between measured and expected values. Parameters considered include: centrifugal compressor discharge pressure, centrifugal compressor thermal efficiency, fuel flow, turbocharger speed, axial compressor discharge pressure, and air filter pressure drop. For most parameters, a method of predicting expected values is: first, to map performance over a range of operating conditions, then develop a regression model. Normalizing (dividing each measured value by its expected value) and comparing the result to unity represents one way to monitor for deterioration. Comparing the observed deviation against the statistical variance provides an alternative method to assess the significance of the deviation.
Stator Diffusion Enhancement Using a Re-Circulating Co-Flowing Steady Jet
Authors: Car David , Kuprowicz Nicholas J. , Estevadeordal Jordi , Zha Gecheng , Copenhaver William
Published: November 2008

This paper will outline a steady flow control technique that augments the diffusion process within a stator passage via a continuous co-flowing secondary flow stream along the suction surface. The technique is similar to that used for flow vectoring in nozzles where a secondary flow stream is used to enhance the diffusion and vectoring of high speed jets. Diffusion factors in excess of 0.95 are simulated and the “penalty” for the secondary system is addressed with an availability and simple power analysis. Losses within the secondary flow stream were included in the availability analysis, but it did not account for losses within a delivery system of this secondary flow. This was accomplished through the ID power analysis which assessed this technique’s impact on the efficiency of an axial compression stage and the sensitivity of this efficiency to the secondary flow system’s efficiency. Also, a system level analysis is presented to assess the merits that may be realized in a notional engine with this type of flow control. Particularly, impacts on specific fuel consumption and thrust-to-weight ratio were addressed. A cascade experiment was performed to demonstrate the concept and was conducted in a blow-down cascade tunnel. Significant improvements in diffusion were qualitatively seen from the DPIV measurements despite limitations in achieving the desired secondary flow conditions.
Performance Degradation Due to Blade Surface Roughness in a Single-Stage Axial Turbine
Authors: Yun Yong Il , Park Il Young , Song Seung Jin
Published: November 2008

Turbine blades experience significant surface degradation with service. Previous studies indicate that an order of magnitude or greater increase in roughness height is typical, and these elevated levels of surface roughness significantly influence turbine efficiency and heat transfer. This paper presents measurement and a mean line analysis of turbine efficiency reduction due to blade surface roughness. Performance tests have been conducted in a low speed, single-stage, axial flow turbine with roughened blades. Sheets of sandpaper with equivalent sandgrain roughnesses of 106 and 400 μm have been used to roughen the blades. The roughness heights correspond to foreign deposits on real turbine blades measured by Bons et al. [1]. In the transitionally rough regime (106 μm), normalized efficiency decreases by approximately 4 percent with either roughened stator or roughened rotor and 8 percent with roughness on both the stator and rotor blades. In the fully rough regime (400 μm), normalized efficiency decreases by 2 percent with roughness on the pressure side and by 6 percent with roughness on the suction side. Also, the normalized efficiency decreases by 11 percent with roughness only on stator vanes; 8 percent with roughness only on rotor blades; and 19 percent with roughness on both the stator and rotor blades.
Effect of 3D Vane Shape on the Flow Capacity
Authors: Afanasiev I. V. , Granovski A. V. , Karelin A. M. , Kostege M. K.
Published: November 2008

The results of the numerical analysis of the flow capacity and other parameters at the different turbine vanes are presented in this paper. Two plane cascades with the same geometrical throat but with a different shape of suction surface have been investigated by means of the 2D Navier-Stokes code [1]. Stacked with these profiles two vane rows with tip meridional opening have been investigated by means of the 3D Euler code [2] and the 3D Navier-Stokes code [3]. The numerical investigation of two full-scale annular vane rows is confirmed by experimental mass flow performance, obtained in a range of exit isentropic Mach number on the mean diameter from Ma2 is = 0.7 to Ma2 is = 1.3.
Rotor-Stator Interactions in a Four-Stage Low-Speed Axial Compressor: Part I — Unsteady Profile Pressures and the Effect of Clocking
Authors: Mailach Ronald , Vogeler Konrad
Published: November 2008

This two-part paper presents detailed experimental investigations of unsteady aerodynamic blade row interactions in the four-stage Low-Speed Research Compressor of Dresden. In part I of the paper the unsteady profile pressure distributions for the nominal setup of the compressor are discussed. Furthermore the effect of blade row clocking on the unsteady profile pressures is investigated. Part II deals with the unsteady aerodynamic blade forces, which are calculated from the measured profile pressure distributions. The unsteady pressure distributions were analysed in the first, a middle and the last compressor stage both on the rotor and stator blades. The measurements were carried out on pressure side and suction side at midspan. Several operating points were investigated. A complex behaviour of the unsteady profile pressures can be observed, resulting from the superimposed influences of the wakes and the potential effects of several up- and downstream blade rows of the four-stage compressor. The profile pressure changes nearly simultaneously along the blade chord if a disturbance arrives at the leading edge or the trailing edge of the blade. Thus the unsteady profile pressure distribution is nearly independent of the convective wake propagation within the blade passage. A phase shift of the reaction of the blade to the disturbance on the pressure and suction side is observed. In addition clocking investigations were carried out to distinguish between the different periodic influences from the surrounding blade rows. For this reason the unsteady profile pressure distribution on rotor 3 was measured, while stator 1–4 were separately traversed stepwise in the circumferential direction. Thus the wake and potential effects of the up- and downstream blade rows on the unsteady profile pressure could clearly be distinguished and quantified.
Syngas Fed Gas Turbine Performance Increase by Means of Evaporative Cooling
Authors: Brusca S. , Lanzafame R.
Published: November 2008

It is well known and proven by experience that gas turbine performance decrease while atmospheric temperature increases. Basing on theoretical and experimental data, it is also known that atmospheric air relative humidity it is able to reduce power losses due to high external temperature. Moving from this consideration, it is possible to increase engine performance at high atmospheric temperatures using evaporative cooling technique. The present paper deals with the thermodynamic study of the performance of a syngas fed gas turbine with evaporative cooler into the compressor intake system from both a theoretical and experimental point of view. A mathematical model of the gas turbine has been developed using GateCycle code. Engine performance analysis at various values of atmospheric temperature, relative humidity and pressure has been carried out. Two control strategies of the artificial air humidifier have been implemented: the first is characterized by an air humidity constant at the intake of the compressor (set to 95%); the second one is characterized by an air temperature constant at the intake of the compressor (set to the temperature corresponding to maximum IGV opening). Results analysis shows that using both of control strategies power and efficiency losses recovery could be achieved depending on atmospheric air humidity and temperature.
Salt in the Marine Environment and the Creation of a Standard Input for Gas Turbine Air Intake Filtration Systems
Authors: McGuigan Peter T.
Published: November 2008

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.
Influence of the Fillet Between Blade and Casing on the Aerodynamic Performance of a Transonic Turbine Vane
Authors: Pieringer P. , Sanz W.
Published: November 2008

Results of CFD simulations always suffer from simplifications made in flow modeling and boundary treatment, and from imprecise modeling of the geometry. For instance, the fillet between blade and casing is usually not considered in numerical calculations, since the grid generations is much more intricate and the effects on the flow result are assumed to be small. Especially when the profile close to the casing tends to induce flow separation, neglecting the fillet can result in a considerable error. In this paper, the influence of the fillet between the blade and casing at the hub and tip of a transonic turbine vane is investigated by CFD, taking into account different fillet radii. The numerical code applied solves the Reynolds-averaged Navier-Stokes equations using a time-iterative finite volume method. Turbulence is modeled by Spalart and Allmaras’ one-equation model. Results show that, depending on the flow situation, varying the fillet radius can either increase or decrease efficiency.
Technical and Economical Feasibility of Gas Turbine Inlet Cooling Using Evaporative Fogging System in Two Different Locations in Oman
Authors: Zurigat Yousef H. , Dawoud Belal , Al-Bortmany Jamal N. , Al-Shihabi Sameh T.
Published: November 2008

In this paper gas turbine power boost via inlet air evaporative fogging system is evaluated for power plants of 40 MW power output in two different locations in Sultanate of Oman. The cooling effect is quantified using evaporative cooling degree hour (ECDH) approach. The power output boost based on the month with the highest number of evaporative cooling degree hours reaches as high as 20% for both locations.. This is significant in view of the increased air conditioning load during summer months. It is found that the average net present value (NPV) of installing fogging system in Marmul is $4,622,018 and in Fahud is $6,182,496. It is also found that the purchase and installation costs are paid back within the first six months of system operation and for later years, annual revenue of over $500,000 is generated.
Thermal Stability Fuel Additives for Civil Aviation Applications
Authors: Versluis J. F. A. , van Buijtenen J. P. , Melkert J. A. , Bogers P.
Published: November 2008

Next generation aircraft propulsion systems inevitably place higher thermal loads on jet fuel since it is used as primary heat sink for engine, hydraulics, avionics and other on-board systems. Increased fuel temperatures prior to combustion may lead to deposit formation in fuel systems and combustion sections. This limits engine performance, puts a burden on maintenance personnel and increases operational costs. U.S. Air Force, industry and academia therefore decided to team up and start the development of thermally stable fuels in the late eighties. This initiative eventually led to the formulation of an additive package capable of improving fuel thermal stability with 100°F (56°C). Although significant experience has been gained with the additive in military applications, the potential in the much larger civil market is yet untapped. Recent evidence however indicates the ability of the additive to reduce particulate emissions and component wear as well. This paper describes the experiments that were undertaken with a stationary gas turbine located at Delft University of Technology (DUT). The proprietary additive in question, provided by Shell Aviation (SAV), was added to commercial Jet A-1 kerosene. Repeatable tests were conducted to characterize the exhaust aerosol and combustor deterioration of the test-rig with standard and dosed fuel. The outcome of the experiments indeed suggests a role of the stability additive in soot (precursor) formation processes. Short-term cleaning effects inside the combustor were not observed however.
Investigation of the Two-Phase Flow Field of the GTX100 Compressor Inlet During Off-Line Washing
Authors: Engdar Ulf , Orbay Raik C. , Genrup Magnus , Klingmann Jens
Published: November 2008

A modern gas turbine compressor, with its highly aerodynamically loaded blades, is sensitive to changes in profile shape and to surface roughness. Fouling is inevitable, despite highly efficient filtration systems. The remedy to this problem is washing. There are two different approaches, on-line or off-line washing. The off-line wash is the most effective one, whilst on-line washing only prolongs the interval between off-line washes. Most findings in this field are highly empirical, being based on some 50 years of industrial gas turbine operation. This paper is an investigation of the two-phase flow in the bellmouth of the compressor during off-line washing conditions. The unit under study was the GTX100 turbo-set. Computational fluid dynamics (CFD) is used in this paper to perform a detailed study of the flow field. The main emphasis has been on studying the characteristics of the injected spray used for cleaning of the compressor. The benefit of heating this fluid is of special interest, since if this heating can be avoided, the outage time for the off-line compressor wash can be shortened. To provide the CFD computations with accurate boundary conditions for the spray, laser-based measurements of a spray, originating from an authentic wash nozzle, have been conducted. The commercial CFD program Star-Cd has been used for all computations. The computations show that the water injected, regardless of its inlet temperature, is cooled down to ambient air temperature well before the spray reaches the inlet guide vanes. This indicates that heating of the wash fluid can be abolished. The airflow seems not to be to influenced by the injected fluid to any great extend.
Parametric Effects on Heat Transfer of Impingement on Dimpled Surface
Authors: Kanokjaruvijit Koonlaya , Martinez-Botas Ricardo F.
Published: November 2008

Jet impingement on a dimpled surface is investigated experimentally for Reynolds numbers in the range 5000–11500, and jet-to-plate spacing from 2 to 12 jet-diameters. These include spatially resolved local Nusselt numbers with impingement both on the dimpled itself and on the flat portion between dimples. Two dimple geometries are considered: hemispherical dimples and double or cusp elliptical dimples. All experiments were carried under maximum crossflow, that is the spent air exits along one way. At the narrow jet-to-plate spacing, such as H/Dj = 2, a vigorous recirculation occurred, which prevented the dimpled plate to enhance heat transfer. The effect of impinging jet positions meant that impinging onto dimples generated more and higher energetic vortices, and this led to better heat transfer performance. Cusped elliptical dimples increase the heat transfer compared to a flat plate less than the hemispherical geometry. The influence of dimple depth was also considered, the shallower dimple, d/Dd = 0.15, improves significantly the heat transfer by 64% compared to that of the flat surface impingement at H/Dj = 4, this result was 38% higher than that for a deeper dimple of d/Dd = 0.25. The very significant increase in average heat transfer makes dimple surface impingement a candidate for cooling applications. Detailed pressure measurements will form a second part of this paper, however, plenum pressure measurements are illustrated here as well as a surface pressure measurement on both streamwise and spanwise directions.
Nonlinear Model Predictive Control for Gas Turbine Engines
Authors: Mu Junxia , Rees David
Published: November 2008

In this paper Nonlinear Model Predictive Control (NMPC) is applied to a gas turbine engine. Since the performance of model based control schemes is highly dependent on the accuracy of the process model, the estimation of global nonlinear gas turbine models using NARMAX and neural network is first examined. To solve the NMPC problem, the Newton-based Levenberg-Marquardt Approach (NLMA) with hard constraints and Sequential Quadratic Programming (SQP) with soft constraints are validated using a wide range of large random, small and ramp signal tests. It is shown that the control performance using SQP is slightly better than that of NLMA, and proposed methods are robust in the face of large disturbances and model uncertainties. The results presented illustrate the improvement in the control performance using both methods over against gain-scheduling PID controllers.
Preliminary Evaluation of Turbulence Level Influence in Heat Transfer Measurements
Authors: Carcasci Carlo , Innocenti Luca , Surace Marco
Published: November 2008

Heat transfer coefficients have often been experimentally measured, taking into account Nusselt number as a function of Reynolds and Prandtl number. Most experimenters spend their effort to control turbulence level, set it to different values, or keep it unchanged during the tests, as it’s not easy to predict how its initial level may change final results. The aim of this work is to add some comprehension on how different turbulence incoming levels may affect heat transfer measurements, and when it’s possible or not to neglect such effects. Experimental setup features different duct geometries, and thermocromic liquid crystals coupled with hot-wire anemometers are used as main measurement techniques. Tests were performed for Reynolds number from 10000 to 50000 and turbulence level from 3% to 12%. Several turbulence manipulators were adopted, including aluminum foams and multi-perforated plates, and results show some interesting dependences of heat transfer from both turbulence level and grid features.
Vent Gas Collection From Gas Compressor Dry Gas Seals
Authors: Suomilammi Ari
Published: November 2008

Gasum is an importer of natural gas and is operating and maintaining the Finnish transmission pipeline in which the pressure is maintained with three compressor stations. Gasum’s compressor stations are unmanned and remotely controlled from the central control room. Some of the compressor units are equipped with dry gas seals. The otherwise satisfactory operation of dry gas seals has the disadvantage of methane emissions. Reduction of methane emissions has been stated as a target by international auspices of the Kyoto Protocol or through national programs seeking to reduce emissions. The application described in this paper to collect vent gases from the dry gas seals was installed into four of the compressor units during 2001. The compressors are centrifugal compressors: two of them are Nuovo Pignone PCL603 with PGT10DLE (10 MW) gas turbine and two are Demag DeLaval 2B-18/18 with Siemens Tornado gas turbines (6,5 MW). It is normal for dry gas seals to have a small leakage of gas through the seals due to the function principle and required cooling of the seals. This gas emitted from the seals is normally about of 5...10nm3/h per one compressor unit during operation and during the stand-still the leakage is almost zero. In the year 2000 the total amount of emitted gas in Gasum’s units was about 50.000 nm3 per four compressor units. The target was to find an efficient method to collect the dry gas seal vent gas and utilize it. The solution must be simple and its investment costs must be feasible. Injection of the vent gases to the gas turbine inlet air flow was selected as a solution among some alternatives. The operating experience so far has been several thousands of operating hours without any malfunctions. The amount of collected gas by this system has been in the range of 80.000 nm3 per annum. The total cost of the system for four compressor units was about 85.000€. The intention of this paper is not to describe any scientific approach to the issue but to present a practical solution with operating experience.
Enhanced TF40B Gas Turbine Engine Bleed Air Anti-Ice System (BAAS) Development
Authors: Yee Roger , Myers Lee
Published: November 2008

The Landing Craft Air Cushion (LCAC) Service Life Extension Program (SLEP) upgrades the current TF40B gas turbine engine and analog control system to an Enhanced TF40B (ETF40B) gas turbine with a Full Authority Digital Engine Control (FADEC) system. This upgrade and enhancement will provide additional engine horsepower, increased engine reliability, modern digital engine control equipment, and a Bleed Air Anti-Ice System (BAAS) for the LCAC during cold weather operations. The original permanent BAAS system for the SLEP configured LCAC has been redesigned as a “removable kit” to reduce overall craft weight and to minimize maintenance for the crews. The development has been an ongoing effort between the Navy, Textron Marine & Land Systems who is the LCAC craft builder, and Vericor Power Systems, who is the ETF40B manufacturer. This paper will document and outline the BAAS development effort and the many lessons learned during the design of a prototype BAAS system for the ETF40B engine.
Permanent Magnet High Speed Starter/Generator System Development Directly Coupled to Gas Turbine Engine for Mobile Auxiliary Power Unit
Authors: Yang H. S. , Rho M. S. , Park H. Y. , Choi J. H. , Cha Y. B. , Kwon J. H. , Yang C. H. , Hwang J. B.
Published: November 2008

This paper shows that high-speed starter/generator system is more efficient for gas turbine engine for mobile auxiliary power unit. The system is rated at 25kW, 325Vdc, 60krpm. The system also provides 4kw to start the 100kW engine. The system consists of a high speed machine directly coupled to the gas turbine engine, a power control unit (PCU), and an electronics controller. The PCU is consist of boost converter that boost from 24V (Battery of Vehicle) to 235V for driving high-speed motor, inverter drive PMSM (Permanent Magnet Synchronous Motor), and buck converter drop the voltage to 28V. For PMSM driving the system applied SVPWM (Space Vector Pulse Width Modulation), sensorless algorithm. And then, to supply optimized power, “Constant Power Control Algorithm” is applied. For the system development, electromagnetic analysis, structure analysis, rotor dynamic analysis, and heat transfer analysis are done. After manufacturing, we have tested the system many times to produce verified performance.
Investigation on a Type of Flow Control to Weaken Unsteady Separated Flows by Unsteady Excitation in Axial Flow Compressors
Authors: Zheng Xin-Qian , Zhou Xiao-Bo , Zhou Sheng
Published: November 2008

By solving unsteady Reynolds-averaged 2-D N-S equations discretized by a high-order scheme, the results showed that the disordered unsteady separated flow could be effectively controlled by periodic suction and blowing in a wide range of incidence, resulting in enhancement of time-averaged aerodynamic performances. The effects of unsteady excitation frequency, amplitude and excitation location were investigated in detail. The effective excitation frequency spans a wide spectrum and there is an optimal excitation frequency that is nearly equal to the Characteristic frequency of vortex shedding. Excitation amplitude exhibits a threshold value (nearly 10% in term of the ratio of maximum velocity of periodic suction and blowing to the velocity of free flow) and an optimal value (nearly 35%). The optimal excitation location is just upstream of the separation point. We also explored feasible unsteady actuators by utilizing upstream wake for constraining unsteady separation in axial flow compressors.
Flowfield and Pressure Measurements in a Rotating Two-Pass Duct With Staggered Rounded Ribs Skewed 45° to the Flow
Authors: Liou Tong-Miin , Hwang Yi-Sian , Li Yi-Chen
Published: November 2008

Laser-Doppler velocimetry and pressure measurements are presented of the local velocity and wall pressure distributions in a rotating two-pass square duct with staggered ribs placed on the leading and trailing walls at an angle of 45° to the main stream. The ribs were square in cross-section with the radii of rounds and fillets to rib height ratios of 0.33. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number Ro ranged from 0 to 0.2. Results are documented in terms of the evolutions of both main flow and cross-stream secondary flow, the distributions of the pressure coefficient, and the variation of friction factor with Ro. For CFD reference, the periodic fully developed flow condition is absent for the present length of the rotating passage roughened with staggered 45° ribs. In addition, the relationships between the regional averaged Nusselt number, transverse and convective mean velocity component, and turbulent kinetic energy are addressed. Using these relationships the general superiority of heat transfer enhancement of the staggered 45° ribs arrangement over the in-line one can be reasonably illustrated. Simple expressions are obtained to correlate the friction factor with Ro, which are lacking in the published literature for passages ribbed with staggered 45° ribs. The staggered 45° ribs are found to reduce the friction loss to about 88%±1% of the in-line 45° ribs for the rotating passage under the same operating conditions. The respective contributions of the angled ribs and passage rotation on the passage friction loss are identified.
An Assessment of Black Liquor Gasification Combined Cycles: Part A — Technological Issues and Performance Comparisons
Authors: Consonni Stefano , Larson Eric D. , Katofsky Ryan
Published: November 2008

Black liquor gasification (BLG) technologies are under active commercial development in the United States and Europe. BLG has been proposed as a future replacement for Tomlinson boilers to provide more efficient, safer, environmentally-friendlier, and more cost-competitive chemical and energy recovery at kraft pulp and paper mills. Also, some pulping process improvements are more readily implemented with BLG than with black liquor combustion. This is Part A of a two-part paper summarizing results of a large study supported by the US Department of Energy, the American Forest and Paper Association, the Southern Company, and the Tennessee Valley Authority to assess performances, emissions, costs and overall benefits of black liquor gasification combined cycle (BLGCC) technology for the U.S. kraft pulp and paper industry. Part A discusses the status of leading black liquor gasification technologies and presents detailed mass and energy balances for BLGCC integrated with a pulp and paper mill producing 1725 metric tons per day of uncoated freesheet paper. The corresponding nominal flow of black liquor solids is 6 million 1bs/day (or 438 MW of contained energy). Mass and energy balances are also presented at a comparable level of detail for state-of-the-art and advanced Tomlinson systems. Tomlinson performances are compared with that for three BLGCC configurations: (i) low-temperature, indirectly-heated gasifier coupled with a medium-power output heavy-duty gas turbine; (ii) high-temperature, oxygen-blown gasifier coupled with a medium-power output gas turbine; (iii) same high-temperature gasifier coupled with a utility-scale gas turbine, where the extra fuel input required to fully load the gas turbine is supplied by natural gas. With state-of-the-art Tomlinson technology, the integrated mill must import approximately 36 MW from the electric grid, which can be reduced to 11.5 MW with an advanced Tomlinson design. Medium-scale BLGCC allows export of 15–20 MW to the grid. This increases to 125 MW when the gasifier is coupled to the utility-scale gas turbine. The superior thermodynamic features of BLGCC are evidenced by the high ratio (0.5–0.9) of extra electricity generated by the BLGCC to extra fossil fuel purchased (higher heating value basis).
An Assessment of Black Liquor Gasification Combined Cycles: Part B — Emission, Costs and Macro-Benefits
Authors: Larson Eric D. , Katofsky Ryan E. , Consonni Stefano
Published: November 2008

This paper and its companion (Consonni et al., 2004) summarize the results of a major study (Larson, et al., 2003) that assessed performances, emissions, costs and overall benefits of black liquor gasification combined cycle (BLGCC) technology for the U.S. kraft pulp and paper industry. This paper presents analysis and estimates of the potential mill-level air emissions and financial performance of future commercial BLGCC systems described in technical detail in the companion paper. Also, potential regional and national impacts on energy consumption and emissions are estimated under different future BLGCC market penetration scenarios. Emission estimates for SO2, NOx, CO, volatile organic carbon (VOCs), particulate matter, total reduced sulfur (TRS) and CO2 are developed based on detailed quantitative data for Tomlinson furnaces and on extrapolation of gas turbine emissions and other relevant data for BLGCC systems. Prospective economics for a hypothetical representative mill in the Southeastern U.S. are assessed by assuming that an investment would be made in a new power/recovery system to replace an existing Tomlinson system that has reached the end of its working life. Key inputs to the financial analysis include the mass/energy balances shown in the companion paper and engineering cost estimates for each power/recovery system that were developed by two outside engineering firms. Because the overall objective of the study was to examine the long-term commercial potential for BLGCC, the capital cost estimates were based on assumed “Nth plant” levels of technology maturity and operational reliability. Widespread commercial implementation of BLGCC systems in the United States would enable significant energy savings for the country as a whole. Significant reductions in emissions of criteria pollutants and greenhouse gases could also be achieved, especially in the Southeastern United States, where two-thirds of U.S. kraft pulp mills are located. Relative to state-of-the-art Tomlinson systems, financial returns on investment are attractive without explicit valuation of environmental benefits. With monetary valuation of such benefits, the financial returns are very attractive.
Compressible Flow in Inlet Guide Vanes With Mechanical Flaps
Authors: Boehle M. , Cagna M. , Itter Lutz
Published: November 2008

The classical type of inlet guide vanes consists of uncambered or slightly cambered profiles, the stagger angle of which can be varied. A more advantageous possibility of generating an angular momentum in front of the rotor of the first stage contains the application of inlet guide vanes with mechanical flaps. This configuration consists of uncambered profiles with mechanical flaps. In the present paper, flow physics is explained for this configuration and compared with the flow physics for the classical type of inlet guide vanes. The configuration with mechanical flaps is examined numerically for 20 deg. and 32 deg. flap angles. The emphasis lies on the description of the compressible flow phenomena, which become dominant if the Mach number of the incoming flow gets close to the critical Mach number. An analytical estimation for the Mach number at the exit of the guide vanes is introduced and the results are discussed together with the results of the CFD simulations.
Probabilistic Analysis of a Turbofan Secondary Flow System
Authors: Cloud David , Stearns Ethan
Published: November 2008

This paper documents a probabilistic analysis of the secondary flow system in a modern commercial turbofan engine. The purpose of this analysis is to investigate the variability in the high and low rotor bearing loads and total secondary flow due to the inherent uncertainty in manufacturing processes and engine performance. In addition to quantifying the variability in bearing load and secondary flow, the sensitivity of the parameters to individual input variables is determined. The system was found to behave linearly, resulting in negligible mean shifts due to input variation. The importance of correlation among the performance parameters will be addressed, as well as the effects of different correlations. Methods used to reduce the time required for the analysis will also be discussed. This type of analysis has many applications in cost reduction, engine design, optimization, and root cause analysis that will be covered in this paper.
The Study on Development of Low NOx Combustor With Lean Burn Characteristics for 20 kW Class Microturbine
Authors: Yoon JeongJung , Lee HeonSeok
Published: November 2008

In order to reduce NOx emissions for the 20kW class microturbine under development, the low NOx characteristics were investigated as an application of the lean burn premixed combustion technology. This study was performed under the conditions of high temperature and high pressure. The compressed air of 2.5bar, 3.0bar, and 5.0bar with temperature of 560K was supplied to the combustor through the preheater. The exhaust air was sampled and measured at the immediate exit of the combustor. It is found that NOx increased while CO decreased as increasing inlet air temperature and pressure. NOx decreased, but CO increased as increasing mass flow of inlet air. Equivalent ratio was maintained between 0.10 and 0.16 in the lean region. NOx increased along equivalent ratio, while CO decreased because of the influence of flame temperature. Through numerical approach work with an appropriate combustion model, a complicated swirling flow pattern was predicted, and numerical values of NOx and CO emission were calculated and compared with experiments. As the results of this study, NOx can be reduced up to less than 42ppm at 15% of oxygen when the 20kW class microturbine is operated at design condition.
Investigation on NOx of a Low Emission Combustor Design With Multihole Premixer-Prevaporizer
Authors: Lin Yuzhen , Peng Yunhui , Liu Gaoen
Published: November 2008

A low NOx emission combustor design was presented in this paper. The design features the premixer-prevaporizer tube with multihole and two stages arranged radially in line, with the outer stage being pilot stage and inner stage being main stage. The multihole premixer and prevaporizer is a part of main stage. The results of NOx emission were provided and also compared with the baseline design that the premixer and prevaporizer tube without multihole. The double swirler prefilming airblast atomizer was installed in the premixed prevaporized duct entrance. The mean drop size and radial fuel flux distribution were measured to determine proper configurations of the multihole premixer-prevaporizer. NOx emission investigations were carried out using a test combustor with one pilot stage and one main stage under the operating condition of high inlet temperature (800K) and inlet air pressure was atmospheric pressure. The experiment results demonstrated large NOx emissions reduction of the multihole premixer-prevaporizer compared with the baseline design. The more even fuel-air mixing, which was gained by the multiple jets, intensified the fuel and air mixing within the premixer-prevaporizer, resulted in the large reduction of NOx emission. The configurations of multihole premixer-prevaporizer had great influence on NOx emissions reduction.