bluuebunny/crossref_metadata_2025 huggingface dataset:
High Stage Loading Low Pressure Turbines: A New Proposal for an Efficiency Chart
Authors: Va´squez R. , Cadrecha D. , Torre D.
Published: February 2009

In 1999, ITP (Industria de Turbopropulsores, S.A) launched a wide on-going research and development program to advance the state of the art in Low Pressure Turbines for use in future high bypass ratio aeroengines for long range civil transport. The objectives of the program were very aggressive in order to satisfy the market demands. Enormous cost and weight savings (about 30% off) were required, equalling or even improving the efficiency and noise emissions. Through that program, ITP has continuously reduced the components of the turbine, as the most adequate way to achieve the previous targets. As result of that reduction, High Stage Loading Turbine technology has being developed. High stage loading turbines have less number of stages to produce the same work output (high stage loading), fewer numbers of blades to perform the same duty (high and ultra high lift blades) and low rotational velocities. An overview of the two options of high stage loading turbines, high through flow and low through flow, is introduced and how both approaches allow an important reduction in weight and number of components (stages and blades). It is also shown that keeping the same levels of efficiency and noise than conventional turbines, is a technical challenge that demands improved aerodynamics or/and higher rotational velocity. This paper describes the current technology limits that are exceeded by high stage loading turbines and the special aerodynamic and geometrical features that come up. Special attention must be highlighted when the stage loading is increased over 50%. In those cases the Mach number limit is exceeded and the pressure ratio per stage is risen as much than transonic blades can not be avoided. Even on those extreme cases the pressure ratio levels and referred work are still far from typical values of high-pressure turbines and geared low-pressure turbines, and considering the high efficiencies achieved for those last two types of turbines, someone could wonder whether a specific research program is required. To conclude the paper, a new efficiency chart, alternative to Smith Chart, is presented to support the answer to the previous reasonable question.
Parametric Study on Economic Feasibility of Microturbine Cogeneration Systems by an Optimization Approach
Authors: Gamou Satoshi , Ito Koichi , Yokoyama Ryohei
Published: February 2009

Economic feasibility of microturbine cogeneration systems is investigated by analyzing relationships between the optimal number of microturbine units and the maximum energy demands under various conditions. For this purpose, a method to obtain the maximum energy demand at which the optimal number changes is proposed by combining a non-linear equation problem and an optimal unit sizing problem hierarchically. Based on the proposed method, a map expressing the aforementioned relationships can be illustrated. Through numerical studies carried out on systems installed in hotels by changing the electrical generating efficiency and the capital unit cost of the microturbine cogeneration unit as parameters, the influence of the parameters on the economic feasibility of the microturbine cogeneration system is clarified.
Multi-Stage Solid Oxide Fuel Cell–Gas Turbine Combined Cycle Hybrid Power Plant System
Authors: Tsuji Tadashi , Yanai Noboru , Fujii Kentaro , Miyamoto Hitoshi , Watabe Masaharu , Ishiguro Tatsuo , Ohtani Yuichi , Uechi Hideyuki
Published: February 2009

Today, the need to develop more efficient thermal power systems that emit less greenhouse effect gas has become a paramount importance. In line with this awareness, our research has leapt into such development that the combination of SOFC and Gas Turbine could generate power at extremely high efficiency. In this paper, we would like to present our concept of Inter Cooled Multistage SOFC-GT Hybrid Power System, developed to maximize fuel heat input to the system. We propose the combination of F-class GT (TIT 1350°C class) and 5 stage SOFC as the best for the hybrid power plant system and 77% (LHV base) is achieved at high pressure ratio.
Flow Field and Structure of Turbulent High-Pressure Premixed Methane/Air Flames
Authors: Griebel P. , Scha¨ren R. , Siewert P. , Bombach R. , Inauen A. , Kreutner W.
Published: February 2009

The present study focuses on the flow field characterization of highly turbulent premixed flames, typical for stationary gas turbines. Mean flame front position and flame front structure at high inlet temperatures, lean mixtures, and high pressures are studied, too. Turbulence intensities and integral length scales have been measured in an isothermal flow field with the help of Particle Image Velocimetry (PIV). Mean flame front position and flame structure have been studied using Planar Laser-Induced Fluorescence (PLIF) of the OH radical. Turbulence intensities and integral length scales have been measured for different turbulence generating grid geometries and operating conditions. The results show that the combustor flow field can be divided in a region close to the combustor head, where grid-generated turbulence is dominant, and a region further downstream, strongly influenced by turbulence generated in the shear layer. In general the measured turbulence intensity scales well with the bulk velocity. For a systematic variation of the turbulent Reynolds number, Damko¨hler number, and Karlovitz number the mean flame front position and the flame front structure were investigated. Increasing the pressure and thereby mainly increasing the turbulent Reynolds number only slightly affects the mean flame front position but increasingly corrugates the flame front. Increasing the bulk velocity and thereby the turbulence intensity does not affect the mean flame front position but due to the higher turbulence the flame front is increasingly corrugated.
Application of Genetic Algorithms to Design of an Internal Turbine Cooling System
Authors: Favaretto C. F. F. , Funazaki K.
Published: February 2009

This paper deals with the development of an optimizing technique based on Genetic Algorithms (GA), which can be applied to the optimization of an internal cooling system of turbine nozzles. An impingement cooling system with pins and air-discharging holes is selected as target cooling system to be optimized using a single-objective GA code developed in this study. The optimization is performed for several design parameters such as the impingement and discharging hole diameters, pin diameter and pin height. The computational grid is automatically generated and boundary conditions prescribed. A commercial CFD code is used to evaluate the target function, which is in the present case simply defined as the ratio between the averaged heat transfer coefficient multiplied by the wetted area and the pressure loss. A hybrid FORTRAN/UNIX shell script program controls the whole process of the optimization, leading to the successful achievement for finding an optimum configuration of the cooling system concerned.
Gas Turbine Life Extension: A 655 MW Combined Cycle Power Plant User’s Experience
Authors: Gajjar Hemant , Jain Sunil , Modi Arpesh
Published: February 2009

Gujarat Paguthan Energy Corporation Pvt. Ltd. (GPEC) is operating a Combined Cycle Power Plant, located near Paguthan in the state of Gujarat, India. It is a dual fuel 655MW combined cycle power station consisting of three Heavy Duty Industrial Gas Turbines coupled with three Heat Recovery Steam Generators and one Steam Turbine. In a combined cycle plant, Gas Turbine is the single most critical piece of equipment & costliest to maintain. Maintenance cost of GT can be as high as 85% of the total maintenance cost of a combined cycle power station. It therefore becomes important for a plant operator not only to optimise the maintenance cost but also to look for possible extension in the life of the engine. OEM inherently builds in a factor of safety and coupled with the site operating conditions it is a question of how much more can be squeezed out of a component & the engine as a whole. GPEC’s experience of getting life assessment done on 6 numbers of turbine blades and also making an experience based risk assessment of various hot gas path and critical components is discussed in this paper. The life assessment, for a user, has to basically answer two questions: 1) Can the interval between outages of GT be extended? in other words — How long can the GT be run before taking a planned shutdown (Combustion Inspection or Hot Gas Path Inspection or Major Inspection)? 2) Can the component be refurbished and reused? in other words — How long can a component be used before discarding? Decision for life extension is taken on the basis of the design criteria & OEM’s recommendation, operating experience of self & other users and, results of life assessment testing specially of hot gas path components. A risk assessment table is generated which gives a picture of the possibility of engine life extension and in particular the possibility of extension in running hours between outages. GPEC’s experience, from both technical and commercial point of view, with regard to extending running hours beyond standard recommendation & analysing right refurbishment requirements for hot gas path components to further extend the running hours, is put up in this paper.
Classic Surge in a Centrifugal Compressor
Authors: Rose M. G. , Irmler K. , Schleer M. , Stahlecker D. , Abhari R. S.
Published: February 2009

This paper reports on the results of experimental work using LDA in the flow path of a centrifugal compressor with a vaned diffuser. The work was done in the ‘RIGI’ facility in the Turbomachinery Laboratory (‘LSM’) of ETH Zu¨rich. The flow-field is studied at impeller exit and in the vaned diffuser using LDA. At low rotational speed Mu = 0.4 and low flow rate φ = 0.024 the compression system adopts a complex mode of unsteady behaviour, previous authors have called this ‘classic surge’. The mode exhibits both surge and stall like events. The 2D velocity data are taken with a ‘dual time base’ i.e. both relative to the position of the impeller and also relative to a recorded instantaneous pressure signal. This gives a five dimensional array of results for each velocity component, two spatial coordinates and three temporal coordinates: relative to the impeller, the stall cell and the surge event. The velocity data are reduced relative to the three deterministic temporal axes. The interaction of these deterministic terms is studied. The nature of the interaction between rotating stall and surge in this situation is described.
Experiment on Linear Compressor Cascade With 3-D Blade Oscillation
Authors: Yang H. , He L.
Published: February 2009

An experiment has been carried out to enhance the understanding of 3D blade aeroelastic mechanisms and to produce test data of realistic configurations for validation of advanced 3D aeromechanical methods. A low speed rig with a compressor cascade consisting of seven prismatic blades of controlled diffusion profile has been commissioned. The middle blade is mechanically driven to oscillate in a 3D bending/flapping mode. At a nominal steady flow condition unsteady pressure measurements were performed at six spanwise sections for three different reduced frequencies and two different tip-clearance gaps. Off-board pressure transducers were utilized in conjunction with a transfer-function method to correct tubing distortion errors. The linearity of aerodynamic response is confirmed by the tests with different blade oscillation amplitudes, which enables the tuned cascade results to be constructed by using the Influence Coefficient Method. The measured results illustrate fully three-dimensional unsteady behaviour. Strong spanwise unsteady interaction leads to a non-proportional distribution of pressure amplitude at different spanwise locations. The tests with different tip-clearance gaps (1–2% span) show that the near tip region is destabilised as the tip gap is increased. This may be attributed to the local unloading of the corresponding steady flow. The destabilised region is seen to extend to approximately 20% of the blade span. The total aerodynamic damping at the least stable inter-blade phase angle has been reduced by 27%, when the tip gap is increased from nearly zero to 2% span.
Control of Combustion Dynamics Using Fuel System Impedance
Authors: Richards Geo , Straub Doug , Robey Ed
Published: February 2009

Combustion oscillations (dynamics) have become a major challenge in the development of low-emission premix combustors. In this paper, a variable impedance fuel system is used to modulate the phase and magnitude of the combustion response in a laboratory scale 30 kW combustor. With the proper choice of design parameters, this technique demonstrates significant attenuation of dynamics pressures, over a wide range of operating conditions. The technique is similar to active control, but does not require high frequency actuators. The paper will report on the key design variables that should be considered when using this concept to improve dynamic stability.
Performance Evaluation of a Prototype TurbX™ Engine
Authors: Arimilli Rao V. , Erickson Kurt , Mottley Frederick T. , Conklin James C.
Published: February 2009

A revolutionary new concept internal-combustion engine called TurbX™ was invented and a prototype was built by an independent inventor, M. A. Wilson. Theoretically, the TurbX™ engine cycle can be represented by the Atkinson thermodynamic cycle with a continuous combustion process. Because of these attributes, this concept has the potential for higher fuel economy and power density relative to other internal combustion engine types. To evaluate the performance of this prototype, Oak Ridge National Laboratory and The University of Tennessee conducted an independent experimental study. Two series of tests were performed: cold-flow and fuel-fired tests. Cold-flow, compressed-air driven, tests were performed by pressurizing the combustion chamber with shop air to demonstrate the prototype performance of the turbine section. These results showed positive but unremarkable torque for combustion chamber air pressures above 300 kPa with a functional relationship illustrative of typical gas turbines with respect to shaft speed. The fuel-fired tests consisted of 26 constant-speed runs between 1800 and 9500 RPM. The experimental apparatus limited the maximum test speed to 9500 RPM. The TurbX™ engine produced no net output power for all fuel-fired tests conducted. The temperature measurements indicated that for most of the runs there was sustained combustion. However, even in runs where satisfactory combustion was observed, measured gage pressure inside the combustion chamber never exceeded 15.5 kPa. The lack of sufficient pressure rise inside the combustion chamber is indicative of excessive leakage of the combustion products through the preliminary prototype engine internals. Based on the results and the experience gained through this independent testing of this preliminary prototype, further development of this concept is recommended. Three major issues are specifically identified: 1) the internal components must be redesigned to reduce leakage, 2) combustion chamber design and 3) improve the overall aerodynamic performance of the engine internal components.
Aircraft Turbofan Engine Health Estimation Using Constrained Kalman Filtering
Authors: Simon Dan , Simon Donald L.
Published: February 2009

Kalman filters are often used to estimate the state variables of a dynamic system. However, in the application of Kalman filters some known signal information is often either ignored or dealt with heuristically. For instance, state variable constraints (which may be based on physical considerations) are often neglected because they do not fit easily into the structure of the Kalman filter. This paper develops an analytic method of incorporating state variable inequality constraints in the Kalman filter. The resultant filter is a combination of a standard Kalman filter and a quadratic programming problem. The incorporation of state variable constraints increases the computational effort of the filter but significantly improves its estimation accuracy. The improvement is proven theoretically and shown via simulation results obtained from application to a turbofan engine model. This model contains 16 state variables, 12 measurements, and 8 component health parameters. It is shown that the new algorithms provide improved performance in this example over unconstrained Kalman filtering.
Forced Low-Frequency Spray Characteristics of a Generic Airblast Swirl Diffusion Burner
Authors: Eckstein J. , Freitag E. , Hirsch C. , Sattelmayer T. , von der Bank R. , Schilling T.
Published: February 2009

The low frequency response of the spray from a generic air-blast diffusion burner with a design typical of an engine system has been investigated as part of an experimental study to describe the combustion oscillations of aero engine combustors called rumble. The atomization process was separated from the complex instability mechanism of rumble by using sinusoidal forcing of the air mass flow rate without combustion. Pressure drop across the burner and the velocity on the burner exit were found to follow the steady Bernoulli equation. Phase-locked PIV measurements of the forced velocity field of the burner show quasi-steady behavior of the air flow field. The phase-locked spray characteristics were measured for different fuel flow rates. Here again quasi-steady behavior of the atomization process was observed. With combustion, the phase-locked Mie-scattering intensity of the spray cone was found to follow the spray behavior measured in the non-combusting tests. These findings lead to the conclusion that the unsteady droplet SMD mean and amplitude of the air-blast atomizer can be calculated using the steady state atomization correlations with the unsteady burner air velocity.
Simulation of Transitional Boundary-Layer Development on a Highly-Loaded Turbine Cascade With Advanced RANS Modeling
Authors: Walters D. Keith , Leylek James H.
Published: February 2009

This paper documents computational simulations of the flow over a modern, highly-loaded turbine vane, including boundary-layer transition. Accurate prediction of transition has traditionally been difficult for commonly available RANS-based turbulence models. The present simulations used an advanced version of a three-equation eddy viscosity model recently developed and documented by the current authors. The new model is an elliptic single-point method, developed based on considerations of the universal character of pre-transitional boundary layers that have recently been published in the open literature. Simulations were performed at an engine-realistic chord Reynolds number (2.3×105) and with varying freestream turbulence intensities of 0.6, 10, and 19.5%. Detailed comparisons are made within the developing boundary layer, on both the suction and pressure surfaces, between the simulations and high-fidelity experimental measurements that have been previously documented in the open literature. Comparison of both mean velocity and Reynolds stress profiles indicates that the new model shows potential for predicting boundary layer development, including development of pre-transitional fluctuations and subsequent breakdown to turbulence.
Analysis of Brush Seal Bristle Stresses With Pressure-Friction Coupling
Authors: Aksit Mahmut F.
Published: February 2009

With their superior leakage performance brush seals are used in many demanding sealing applications. In recent years, they found ever increasing use in ground based large industrial gas and steam turbines replacing labyrinth seals. As the applications become more demanding, seal designs are pushed to their limits. The knowledge of brush seal bristle stresses is essential to determine seal pressure carrying capability and amount of creep for high temperature applications. Seal manufacturers continue to rely on their experience and simple models based on beam theory in order to develop the required robust seal designs. Although some analytical formulations are developed over the years, pressure-stiffness coupling and its effects on bristle stresses deserve further study due to complicated frictional bristle interactions. In order to explore brush seal bristle stresses with frictional effects, this paper presents a study using a 3-D finite element analysis. A maximum bristle stress relation is derived based on statistically designed experiments. Model accuracy is determined through verification simulations. A discussion on the effects of design and loading parameters on maximum stress is also included.
Simulations of Shock/Boundary-Layer Interactions Over Highly Loaded Turbine Blades
Authors: Liu Yi
Published: February 2009

Transonic viscous flow over highly loaded turbine blades, where the interaction of a shock wave and a boundary layer often leads to extremely complicated flow phenomena, has been studied numerically in this paper. A Modified Implicit Flux Vector Splitting solver of the Navier-Stokes equations, which has been well established though combining a unique implicit formulation with a Flux Vector Splitting, has been extended to simulate a transonic cascade flow. A low Reynolds number k-ε turbulence model, with the compressibility effect considered, and a transition model have been implemented to predict heat transfer, flow patterns in the high loaded transonic turbine vanes and turbine vanes and blades. Numerical investigations show it has obvious superiority in terms of accuracy, robustness, convergence and computing time.
Heat Transfer Measurements and Predictions for the Vane and Blade of a Rotating High-Pressure Turbine Stage
Authors: Haldeman Charles W. , Dunn Michael G.
Published: February 2009

This paper describes heat-transfer measurements and predictions obtained for the vane and blade of a rotating high-pressure turbine stage. The measurements were obtained with the stage operating at design corrected conditions. A previous paper described the aerodynamics and the blade midspan location heat-transfer data and compared these experimental results with predictions. The intent of the current paper is to concentrate on the measurements and predictions for the 20%, 50%, and 80% span locations on the vane, the vane inner and outer endwall, the 20% and 96% span location on the blade, the blade tip (flat tip), and the stationary blade shroud. Heat-transfer data obtained at midspan for three different TBC coated vanes (fine, medium and coarse) are also presented. Boundary-layer heat transfer predictions at the off-midspan locations are compared with the measurements for both the vane and the blade. The results of a STAR-CD 3D prediction are compared with the 20% and 96% span results for the blade surface. Predictions are not available for comparison with the tip and shroud experimental results.
Mapping and Predicting Air Flows in Gas Turbine Axial Compressors
Authors: McKee Robert J.
Published: February 2009

Determining the airflow through a gas turbine’s axial compressor is not a simple or one step process as many factors affect flow and there is seldom a flow meter or a means to directly measure airflow rate. Speed of the compressor, inlet pressure and temperature, and resistance or backpressure at the compressor’s outlet all affect the amount of airflow. The type of gas turbine, single or twin spool, the magnitude of power produced, the use of bleed or bypass valves, the power turbine speed, and operating conditions all have influences on the amount of airflow. Despite this, there are several reasons why an estimate of airflow is useful for understanding and describing the behavior and performance of gas turbines. The amount of airflow compared to fuel flow determines the composition and condition of the exhaust gases and is directly related to the turbine’s power output, heat rate, and waste heat recovery potential. A predicted airflow rate and the corresponding axial compressor discharge pressure can be used to identify deterioration in performance and to estimate emission characteristics of a unit. This paper presents an approach based on easily obtained gas turbine data, such as the design point data, test stand data, or manufacturer’s curves for the compressor. Compressor performance curves may be obtained from the manufacturer or by mapping compressor output during normal operations. A great deal of information has been presented in the literature about the performance of gas turbines and axial compressors but this paper focuses on methods that are sufficiently simple and direct that users can obtain an estimate of their unit’s airflow, References 1, 2, and 3. Some manufacturers provide computer data bases or on-line control panel estimates of gas turbine airflow but in these cases, the user has no idea what causes a change. Detailed performance curves for axial compressors are usually not available, however, through the methods presented in this paper, a reasonable approximation of the operating curves can be developed and used to estimate axial compressor airflow over the full range of normal operations. The methods described are based on tracking and mapping a compressor’s operations over a period of time and relating compressor output to other performance parameters and known conditions (design point) in order to establish a normally expected airflow rate.
Performance Improvement of Small Gas Turbines Through Use of Wave Rotor Topping Cycles
Authors: Akbari Pezhman , Mu¨ller Norbert
Published: February 2009

Results are presented predicting the significant performance enhancement of two small gas turbines (30 kW and 60 kW) by implementing various wave rotor topping cycles. Five different advantageous implementation cases for a four-port wave rotor into given baseline engines are considered. The compressor and turbine pressure ratios, and the turbine inlet temperatures vary in the thermodynamic calculations, according to the anticipated design objectives of the five cases. Advantages and disadvantages are outlined. Comparison between the theoretic performance (expressed by specific cycle work and overall thermal efficiency) of wave-rotor-topped and baseline engines shows a performance enhancement by up to 33%. The results obtained show that almost all the cases studied benefit from the wave-rotor-topping, but the highest gain is obtained for the case in which the topped engine operates with the same turbine inlet temperature and compressor pressure ratio as the baseline engine. General design maps are generated for the small gas turbines, showing the design space and optima for baseline and topped engines.
Dual Wavelength Temperature Monitoring of TBC Coated Alstom 13E2 Turbine Blades
Authors: Rooth R. A. , Hiemstra W.
Published: February 2009

Through rapid developments in fiber technology and data acquisition technology, pyrometry has become a successful tool for the measurement of gas turbine blade temperatures. The technology enables gas turbine owners and operators to monitor the blades and to optimise the exploitation of their assets in terms of efficiency and maintenance. With the application of thermal barrier coatings on turbine blades, pyrometry faces a new challenge as these coatings are not opaque at commonly used wavelengths. The application of TBC’s to protect the metal blades allows an increase of the firing temperature, increasing the efficiency of the installation, but is potentially an additional cause of locally overheating blades in the case the coating comes off. The present paper reports on the results of experimental work related to the temperature measurement on an in service Alstom 13E2 turbine with TBC coated first stage blades. Temperature measurements have been performed with both short- and long wavelength instruments (1 μm and 10 μm). The optical characteristics of ZrO2 material at a range of temperatures have been determined. These characteristics are important in the implementation of an algorithm that calculates the metal temperature from the temperature measurement results. These metal temperatures are of primary interest, This is the first time that experimental radiation temperature measurements on an industrial turbine, using both 1 and 10 μm technology, are reported. As the measurement trace over the turbine airfoil consists of areas on the blade that are covered with TBC as well as uncovered areas, a very interesting comparison on the merits of the various systems can be presented.
Numerical Investigation of Losses Due to Unsteady Effects in Axial Turbines
Authors: Moczala Michael , von Lavante Ernst , Parvizinia Manuchehr
Published: February 2009

Understanding of losses caused by unsteady effects is essential in efforts to improve the efficiency of modern turbomachines. In the present research work, the unsteady midspan flow in a typical high pressure axial turbine was investigated using a compressible Navier Stokes solver. The aim of this study was to take a closer look at trends in the loss behavior depending on several flow and geometry parameters as well as to give a physical explanation of these trends. Two different definitions of loss coefficients were also employed for the loss assessment and its suitability for evaluation of “unsteady losses” was discussed considering accuracy and physical aspects.
Technical, Financial and Engineering Management of CCGT Overhauls: InnogyOne Approach at Didcot B
Authors: Khan Iftikhar , Hamilton Alan , Llewellyn Richard
Published: February 2009

Operating a CCGT in a highly competitive electricity market requires understanding of many pressures, often potentially conflicting. Reliability, future mechanical integrity, minimum overhaul time and accurate prediction of availability are key issues for financial competitiveness, particularly under the UK’s NETA (New Electricity Trading Arrangements) which reward frequent CCGT two–shifting. The maintenance of CCGTs, in particular gas turbines, is complex discipline, especially as regards the integrity of hot gas path components. Original Equipment Manufacturers (OEMs) are able to offer maintenance packages to support new owners/operators through Long Term Service Agreements (LTSAs). Independent Power Producers (IPPs) are often required by project lenders to adopt this approach, but at a premium. Independent Service Providers (ISPs) are increasingly becoming available as a credible and more cost effective alternative in supporting CCGTs. InnogyOne has developed a comprehensive operations and maintenance package consisting of expert tools and procedures that address the technical, financial and management concerns of CCGT stations. This paper focuses on InnogyOne’s outage strategy and management for a large 1360MW CCGT. Hot Gas Path (HGP) life optimization, gas turbine maintenance strategy including refurbishment, component re-engineering and managing technical risks for pressure parts are addressed. Data capture, quality assurance and documentation are also considered.
Control Study for Five-Axis Dynamic Spin Rig Using Magnetic Bearings
Authors: Cho Benjamin , Johnson Dexter , Provenza Andrew , Morrison Carlos , Montague Gerald
Published: February 2009

The NASA Glenn Research Center (GRC) has developed a magnetic bearing system for the Dynamic Spin Rig (DSR) with a fully suspended shaft that is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. Two heteroplolar radial magnetic bearings and a thrust magnetic bearing and the associated control system were integrated into the DSR to provide magnetic excitation as well as non-contact magnetic suspension of a 15.88 kg (35 lb) vertical rotor with blades to induce turbomachinery blade vibration. For rotor levitation, a proportional-integral-derivative (PID) controller with a special feature for multidirectional radial excitation worked well to both support and shake the shaft with blades. However, more advanced controllers were developed and successfully tested to determine the optimal controller in terms of sensor and processing noise reduction, smaller rotor orbits, more blade vibration amplitude, and energy savings for the system. The test results of a variety of controllers that were demonstrated up to 10,000 rpm are shown. Furthermore, rotor excitation operation andconceptual study of active blade vibration control are addressed.
Case Studies of Fatigue Life Improvement Using Low Plasticity Burnishing in Gas Turbine Engine Applications
Authors: Preve´y Paul S. , Ravindranath Ravi A. , Shepard Michael , Gabb Timothy
Published: February 2009

Surface enhancement technologies such as shot peening, laser shock peening (LSP), and low plasticity burnishing (LPB) can provide substantial fatigue life improvement. However, to be effective, the compressive residual stresses that increase fatigue strength must be retained in service. For successful integration into turbine design, the process must be affordable and compatible with the manufacturing environment. LPB provides thermally stable compression of comparable magnitude and even greater depth than other methods, and can be performed in conventional machine shop environments on CNC machine tools. LPB provides a means to extend the fatigue lives of both new and legacy aircraft engines and ground-based turbines. Improving fatigue performance by introducing deep stable layers of compressive residual stress avoids the generally cost prohibitive alternative of modifying either material or design. The x-ray diffraction based background studies of thermal and mechanical stability of surface enhancement techniques are briefly reviewed, demonstrating the importance of minimizing cold work. The LPB process, tooling, and control systems are described. An overview of current research programs conducted for engine OEMs and the military to apply LPB to a variety of engine and aging aircraft components are presented. Fatigue performance and residual stress data developed to date for several case studies are presented including: • The effect of LPB on the fatigue performance of the nickel based super alloy IN718, showing the fatigue benefit of thermal stability at engine temperatures. • An order of magnitude improvement in damage tolerance of LPB processed Ti-6-4 fan blade leading edges. • Elimination of the fretting fatigue debit for Ti-6-4 with prior LPB. • Corrosion fatigue mitigation with LPB in Carpenter 450 steel. • Damage tolerance improvement in 17-4PH steel. Where appropriate, the performance of LPB is compared to conventional shot peening after exposure to engine operating temperatures.
High Specific Speed, High Inducer Tip Mach Number, Centrifugal Compressor
Authors: Rodgers C.
Published: February 2009

The demand for more efficient turbocharger and aviation centrifugal compressors operating at higher pressure ratios and specific speeds with extended flow ranges is focusing research efforts on the inducer and diffuser transonic flow fields. At pressure ratios above 5.0 and specific speeds of unity inducer tip relative Mach numbers exceeding 1.4 can be encountered, precipitating both increased shock losses and diminished stall margin. The results of compressor rig testing on a research 6.8 inch tip (173mm) diameter single stage centrifugal compressor operating with inducer tip relative Mach number up to 1.5 are presented. The test results reveal high efficiency combined with extended flow range. This was achieved through improved impeller stability with shroud bleed, thereby permitting the diffuser to operate stably on its positive slope recovery characteristic.
Application of “H Gas Turbine” Design Technology to Increase Thermal Efficiency and Output Capability of the Mitsubishi M701G2 Gas Turbine
Authors: Fukuizumi Y. , Masada J. , Kallianpur V. , Iwasaki Y.
Published: February 2009

Mitsubishi completed design development and verification load testing of a steam-cooled M501H gas turbine at a combined cycle power plant at Takasago, Japan in 2001. Several advanced technologies were specifically developed in addition to the steam-cooled components consisting of the combustor, turbine blades, vanes and the rotor. Some of the other key technologies consisted of an advanced compressor with a pressure ratio of 25:1, active clearance control, and advanced seal technology. Prior to the M501H, Mitsubishi introduced cooling-steam in “G series” gas turbines in 1997 to cool combustor liners. Recently, some of the advanced design technologies from the M501H gas turbine were applied to the G series gas turbine resulting in significant improvement in output and thermal efficiency. A noteworthy aspect of the technology transfer is that the upgraded G series M701G2 gas turbine has almost equivalent output and thermal efficiency as H class gas turbines while continuing to rely on conventional air-cooling of turbine blades and vanes, and time proven materials from industrial gas turbine experience. This paper describes the key design features of the M701G2 gas turbine that make this possible such as the advanced 21:1 compressor with 14 stages, an advanced pre-mix DLN combustor, etc, as well as shop load test results that were completed in 2002 in Mitsubishi’s in-house facility.
Three-Component LDV Measurements in the Wake of a Compressor Cascade With Flow Separation
Authors: Hobson G. V. , Caruso T. M. , Carlson J. R.
Published: February 2009

Measurements were taken of the vortex system and turbulent flow that resulted from the interaction between a stator blade and the approaching end-wall boundary layer in a linear cascade of compressor blades. Data were taken at a Reynolds number based on blade chord of and 640000. Five-hole pressure measurements were conducted upstream and downstream of the blade row. The approaching boundary layer was also characterized with the laser-Doppler velocimeter. Downstream three-component laser-Doppler velocimetry surveys were conducted at three streamwise stations to map the location and velocity characteristics of the wake and vortex system. Results clearly showed the extent of the vortex emanating from the separation of the boundary layer on the suction side of the blade. Finally all components of mean flow velocity and turbulence are documented for the last survey station. These data will form challenging test case for numerical code validation.
Extended Multi-Channel H∞/H2 Control of an Evaporation Process
Authors: Yan Wenjun
Published: February 2009

In this paper, a new mixed H∞/H2 control with pole placement approach is developed based on a new stability condition. It extends the standard mixed H∞/H2 control problem to a set of new linear matrix inequality (LMI) constraints. The global optimal controller can be less conservatively synthesized using computationally tractable algorithms. The simulation results of an evaporation process with controllers designed by different techniques demonstrates the superiority of the new method.
Investigation on the Ignition Conditions From a Comparison Between Reacting and Non-Reacting Diesel Spray Experiments
Authors: Kim T. , Ghandhi J. B.
Published: February 2009

Natural luminosity images from reacting diesel sprays were acquired in a combustion-type constant-volume spray chamber. Using an ambient condition of 15 kg/m3 and 1000 K, the effects of peak injection pressures (60, 90 and 150 MPa) and nozzle hole sizes (140, 158 and 200 μm) were investigated. From high-speed natural luminosity cinematography, macroscopic reacting spray characteristics such as flame lift-off height and ignition delay time were obtained. For increasing injection pressures the ignition delay time decreased, and the flame lift off height increased. For increasing hole diameter the ignition time delay decreased, and the flame lift-off height decreased. The authors’ previous results of the fuel concentration measurement from non-reacting spray experiments were used to ascertain the local equivalence ratio for the reacting spray during the ignition and initial flame development period. The first detection of the luminosity (believed to be chemiluminescence) signal was found to occur in fuel-rich vapor regions near the boundary of the liquid core with an equivalence ratio near 2 and a temperature of approximately 800 K. These conditions were found to be independent of injection pressure and nozzle diameter for the condition tested (15 kg/m3 and 1000 K ambient), suggesting that this is a kinetically controlled process.
Experimental and Numerical Investigation of Vapor Formation in a Fuel Rail
Authors: Michalek Donna J. , Stalsberg-Zarling Krista L. , Evers Lawrence W.
Published: February 2009

Recently, additional scrutiny is being placed on all vapor releases to the environment from the fuel system of an automobile. In an effort to lower the overall release of fuel vapor, a preliminary study of the vapor formation processes that occur in a low pressure supply fuel rail was undertaken. The first objective of this work was to determine the means by which fuel vapor is generated within the fuel rail, particularly during hot soak conditions. Then, using this information, the next task was to develop a computational fluid dynamics (CFD) code which would model the vapor formation in the rail. An investigation of the fuel rail material and design revealed that the probable mechanism for vapor formation is nucleate boiling from cavities in the fuel rail surface and at the o-ring connections with the fuel injectors. Therefore, an experiment was constructed to investigate the vapor formation from artificial cavities on a metallic surface and at an o-ring interface. The data collected from the experiment included the departure diameter of the vapor bubbles, the bubble frequency, and the bubble rise velocity. These values, which are used to determine the vapor generation rate, were compared to the results predicted by various correlations available in the literature. Subsequently, a CFD model was constructed of the fuel rail, using Star-CD, by incorporating the appropriate vapor generation correlations as user-defined subroutines. The experimental observations clearly demonstrated that a large amount of vapor was generated at the o-ring interface and, to a lesser degree, from the cavities in the metallic surface. A CFD model was constructed to predict the vapor generated in a fuel rail from these cavities. Existing correlations that describe nucleate boiling adequately model this generation mechanism in the fuel rail. This CFD code can be used to determine the amount of vapor formed under various hot soak conditions. An analytical means of predicting the vapor formation at the o-ring interface will have to be developed in order to complete the CFD model.
Analysis of Forces Acting on Compressor Sliding Vanes
Authors: Huang Yuan Mao , Li Chien Liang
Published: February 2009

This study utilizes Newton’s law to analyze: 1) the force required to act on a vane bottom in order to create zero contact force between the vane and the stator, and 2) the contact forces between the vane and the rotor in a sliding vane compressor. The effects of the number, length, thickness and material of vanes, the locations of the outlet ports, and the rotor rotational speed of the compressor on these forces are analyzed. The results show that the effect of the vane thickness on these forces is not significant. Nevertheless, these forces increase when the number of vanes and the angular starting location of the outlet port increases. When the length and the density of the vane and the rotational speed of the rotor increase, there is a decrease in the force required to act on the vane bottom in order for it to come in to contact with the stator.
Numerical Simulation of a Diesel Particulate Filter During Loading and Regeneration
Authors: Peters Bernhard J.
Published: February 2009

The objective of this study is to develop a numerical method to predict deposition and regeneration of soot in a particulate filter. The fluid dynamic and loading characteristics are described by one-dimensional differential conservation equations for mass and momentum for both inlet and outlet channel. For the inlet channel, the varying cross sectional area due to trapped soot is taken into account. The flow through the soot layer and the filter wall is approximated by Darcy’s law. The evolution of temperature of the gaseous and solid phase (soot layer and filter wall) is dealt with by one-dimensional conservation of energy. However, a two-dimensional approach was chosen for the distribution of species during regeneration within the soot layer. Under these assumptions, deposition and regeneration, the latter as thermal and fuel-additive regeneration, was predicted very satisfactorily.
Torsional Vibration Damping in a Marine Propulsion System Driven by a Two-Cycle Diesel Engine
Authors: Martinek Felix
Published: February 2009

Torsional systems of marine propulsions are simulated by multiple inertias connected by linear springs and linear viscous absolute- and relative damping values. Absolute damping is acting between a global system without rotation and the rotating inertias of engine, propeller and auxiliary drive. Relative damping is acting in between inertias. Inertia and torsional stiffness is predicted by calculation and can easily be verified by measurements. Damping values are roughly estimated by various empirical methods. The measured vibratory stress of an intermediate shaft allows different damping identifications. Discrepancies in damping models for engines and propellers currently used will be presented. General numerical problems of various identifications will be shown as well.
Multidimensional Predictions of In-Cylinder Turbulent Flows: Contribution to the Assessment of k-ε Turbulence Model Variants for Bowl-in-Piston Engines
Authors: Catania Andrea E. , Baratta Mirko , Spessa Ezio , Liu Rui L.
Published: February 2009

As is well known, the in-cylinder flow phenomena can strongly affect the engine combustion process and the related emission sources. Therefore, a better understanding of the fluid motion is critical for developing new engine concepts with the most attractive operation and emission characteristics. To that end, multidimensional flow computational codes with reliable turbulence models are useful investigation and design tools. This paper is concerned with mean-flow and turbulence simulation in a motored model engine with a compression ratio of 6.7. The flow configurations comprise an axisymmetric combustion chamber with one centrally located valve and each of a flat piston and cylindrical bowl-in-piston arrangements. The calculations are performed using a non-commercial CFD code that was originally developed by the authors. A finite volume conservative implicit method, applying various order-of-accuracy schemes, is employed for the discretization of the partial differential equations modeling the in-cylinder turbulent flow, and the resultant algebraic equations are linearized and sequentially solved by an iterative procedure. Velocity-pressure coupling is ensured by a pressure correction method similar to that of the SIMPLER algorithm. Results of the simulation are presented at the model engine speed of 200 rpm throughout the engine cycle. They were obtained using three versions of the k-ε turbulence model (Standard, Two Scale and RNG) which differ from each other for underlying concepts, complexity and accuracy in capturing flow features. Modified boundary conditions with respect to logarithmic wall-functions were applied. Insight was also gained into the nonlinear effects of stress-strain constitutive relation on turbulence modeling. The effects of the equation differencing schemes and computational grid spacing on flow predictions were tested. Then the numerical results were compared to those of LDV measurements and the influence of the k-ε model variants on the flow field features were examined during the induction stroke and around compression TDC.