bluuebunny/crossref_metadata_2025 huggingface dataset:
United States Navy (USN) Integrated Power System (IPS) Gas Turbine Generator Set Test Experience
Authors: Harvey Edward , Kingsley Joseph , Stauffer Matthew
Published: February 2009

Many Navies around the world have either committed to or are considering utilizing an integrated electric propulsion and ship service power system for their next generation of surface combatants. An integrated system provides for greater operational flexibility, efficiency, and survivability as described in Reference [1]. Two examples of this concept are the Type 45 Destroyer program for the Royal Navy and the DD (X) program for the US Navy. The machinery plant for the Type 45 will include both gas turbine and diesel generators sets, and although not determined yet, the DD (X) plant will undoubtedly include gas turbine prime movers. The US Navy has been evaluating a gas turbine generator based Integrated Power System (IPS) architecture at the Land Based Engineering Site (LBES) at the Naval Surface Warfare Center, Ship Systems Engineering Station (NSWCCD-SSES) in Philadelphia, Pa since 1999. This paper will describe the IPS configuration, test program, gas turbine generators, gas turbine generator operational experience, and recommendations for future systems.
Rolls Royce/Allison 501-K Gas Turbine Anti-Fouling Compressor Coatings Evaluation
Authors: Caguiat Daniel E.
Published: February 2009

The Naval Surface Warfare Center, Carderock Division (NSWCCD) Gas Turbine Emerging Technologies Code 9334 was tasked by NSWCCD Shipboard Energy Office Code 859 to research and evaluate fouling resistant compressor coatings for Rolls Royce Allison 501-K Series gas turbines. The objective of these tests was to investigate the feasibility of reducing the rate of compressor fouling degradation and associated rate of specific fuel consumption (SFC) increase through the application of anti-fouling coatings. Code 9334 conducted a market investigation and selected coatings that best fit the test objective. The coatings selected were Sermalon for compressor stages 1 and 2 and Sermaflow S4000 for the remaining 12 compressor stages. Both coatings are manufactured by Sermatech International, are intended to substantially decrease blade surface roughness, have inert top layers, and contain an anti-corrosive aluminum-ceramic base coat. Sermalon contains a Polytetrafluoroethylene (PTFE) topcoat, a substance similar to Teflon, for added fouling resistance. Tests were conducted at the Philadelphia Land Based Engineering Site (LBES). Testing was first performed on the existing LBES 501-K17 gas turbine, which had a non-coated compressor. The compressor was then replaced by a coated compressor and the test was repeated. The test plan consisted of injecting a known amount of salt solution into the gas turbine inlet while gathering compressor performance degradation and fuel economy data for 0, 500, 1000, and 1250 KW generator load levels. This method facilitated a direct comparison of compressor degradation trends for the coated and non-coated compressors operating with the same turbine section, thereby reducing the number of variables involved. The collected data for turbine inlet, temperature, compressor efficiency, and fuel consumption were plotted as a percentage of the baseline conditions for each compressor. The results of each plot show a decrease in the rates of compressor degradation and SFC increase for the coated compressor compared to the non-coated compressor. Overall test results show that it is feasible to utilize anti-fouling compressor coatings to reduce the rate of specific fuel consumption increase associated with compressor performance degradation.
High Capacity and High Efficiency Multi-Stage Air Intake System
Authors: Hashem Alan , Fadda Dani , Fewel Kenneth J.
Published: February 2009

An advanced three stage filtration/separation air intake system (Compact II) is introduced in this paper. The system was developed to meet the current and expected future market demands for gas turbine combustion air treatment in a marine environment. Developing and testing of the Compact II are subjects of this paper.
Condition Monitoring and Fault Diagnosis of Naval Gas Turbines
Authors: Grzadziela Andrzej , Stapersma Douwe , Charchalis Adam
Published: February 2009

The Naval University of Gdynia (NUG) over the years have developed quite an extensive Condition Monitoring and Fault Diagnosis system and has applied this for some time now on Naval Gas Turbines of the Polish Navy. An outline of the system and its use is given in the paper. The Royal Netherlands Naval College, together with Delft University of Technology is active in the field of advanced modelling of marine systems. A broad outline of work done in that area forms the second part of the paper. Recently it has been decided to start a collaboration between the two research groups. The aims of this collaboration will be clarified.
Validation of Compressor Transient Behaviour
Authors: Bakken Lars E. , Bjo̸rge Tor , Bradley Tim M. , Smith Neal
Published: February 2009

Major challenges are related to compressor and driver integration during run down. In order to understand these challenges, the pipeline compressor facility at Troll Kollsnes gas treatment plant, Norway, has been subjected to detailed trip testing and dynamic simulation analysis. The plant includes five pipeline compressors and is utilised as a pilot for analysing the transient response of a 40 MW compressor driven by a variable speed electric motor. The compressor control and protection system include an anti-surge and a hot gas bypass system. Vibration records have shown that under power outage the compressors were exposed to violent vibrations. Further investigation revealed that during a short power outage, the compressor enters the surge- and rotating stall area under certain operating scenarios. The rotating stall response resulted in reduced operating range and flexibility for the pipeline compressors. Specific precautions had to be taken to prevent the compressor from running into the low flow operating area of the performance envelope. Dynamic simulations cover important aspects related to the transient scenario analyses performed to reveal the root cause of the compressor problems. The simulation system enables sophisticated plant models to be configured from high quality standard model algorithm building blocks. Verification of the model blocks have been performed against plant records in order to validate the transient predictions. The paper reports experience from testing and verification of compressor and driver integration with reference to transient behaviour during run down. This includes the validation of the dynamic models, which apply both to the design and commissioning phase where actual plant trip tests should be used to verify the design and stability margins.
Gas Turbine Maintenance Policy: A Statistical Methodology to Prove Interdependency Between Number of Starts and Running Hours
Authors: Ceschini Giuseppe Fabio , Carlevaro Fausto
Published: February 2009

In general, two approaches have been followed so far in gas turbine maintenance procedures to determine correct inspection intervals: “no interdependency” or “interdependency” between number of starts and number of running hours. The first approach is based on the assumption that starts and running hours induce different deterioration processes not correlated to each other. Accordingly, the number of starts defines the life limit for cyclic duty operation where low-cycle fatigue phenomena dominate, while the number of running hours define the continuous operation life limit for which erosion, corrosion and creep are controlling factors. The “interdependency” approach instead assumes that failure is produced by combination of low-cycle fatigue and continuous degradation mechanisms: in this scheme the frequency of starts becomes a fundamental parameter in order to determine the optimal maintenance interval. A statistical and reliability engineering methodology to validate the first or rather the second line of action is described in the paper. The population on which the study was conducted is made up by GE Oil & Gas PGT10 gas turbines that are in operation worldwide with fleet operation totaling 1,5 million hours. Most of the cases examined consist of mechanical drive applications for natural gas production, storage and transportation, with significant combination of both intermittent and continuous operation. Hot gas path components have been chosen for examination in consideration of their sensitivity to effects of both cyclic fatigue stress and wear mechanisms. The analysis concentrates on transition piece and combustion liner, both having scored a number of failures statistically significant for the purposes of this study. This analysis is considered the key to optimize inspection intervals and therefore achieve extended machine life. The methodology, based on Weibull data analysis, has been applied to a restricted sample of machines that operate in “standard” conditions, corresponding to gas fuel utilization, mechanical drive service with homogeneous load factor and very low number of trips. The study shows that interdependency between starts and running hours does exist and, given the number of starts, the corresponding running hours can be evaluated, and the inspection intervals appropriately predicted. Further developments of this study will be aimed at evaluating maintenance factors for “non standard” conditions such as dual fuel combustion systems, generator drive and operation with higher number of trips etc.
The Method of Harmonic Excitation for Determination of the Flexibility of the Support of Machine’s Rotor
Authors: Rybczynski Jozef
Published: February 2009

A series of experimental investigations were made in order to determine the set of coefficients of flexibility of construction supporting the rotor. The investigations were made on the test rig for the rotor dynamics investigation. A harmonic force of known amplitude was applied to all supports of the system to induce vibration of the system. Then the system’s reaction in the form of displacement in all connections at the same time was measured. On the bases of the experimental results a square 36-element (6×6) matrix of flexibility coefficients for each frequency of excitation was created. The matrices are the initial material to determine the modal masses, stiffness coefficients and damping coefficients in such form so that they could be the data to calculate the dynamics of the experimental rotor by means of computer programs. Moreover the experimental results are interesting information in the to analysis of the behavior of the test rig’s pedestals.
Effects of Blade Count on Three-Bladerow Interaction in a Transonic Turbine
Authors: Li H. D. , He L.
Published: February 2009

This paper presents some numerical parametric studies of the multi-row interaction mechanisms for a one and half stage (NGV-rotor-stator) transonic turbine. Firstly both steady and unsteady flows under the nominal operating condition for this turbine have been validated against the experimental data available. The sub-harmonic interaction induced by the two fundamental passing frequencies from the upstream and downstream vanes has been identified in the rotor row. But more significant is an aperiodic unsteady flow pattern characterized by variable amplitudes and inter-blade phase angles in the downstream stator row. Although the time-averaged blade forces only vary by about 5%, the maximum unsteady force can be changed by factor of three among stator blades. The parametric studies have revealed a strong dependence of the aperiodic flow behavior on blade count ratio between the NGV and the stator. The spatial mode of the unsteadiness amplitude variation is shown to correspond exactly to the spatial wavelength due to the NGV-stator interference. The longer the spatial NGV-stator interference wavelength, the larger the aperiodic unsteady loading variation. Given that the spatial mode amplifies the unsteady loading aperiodically on the stator, the present results suggest that the choice of stator-stator relative blade counts may be used to limit the maximum unsteady force on the downstream stator.
Unsteady Pressures in a Transonic Fan Cascade Due to a Single Oscillating Airfoil
Authors: Lepicovsky J. , McFarland E. R. , Capece V. R. , Hayden J.
Published: February 2009

An extensive set of unsteady pressure data was acquired along the midspan of a modern transonic fan blade for simulated flutter conditions. The data set was acquired in a nine-blade linear cascade with an oscillating middle blade to provide a database for the influence coefficient method to calculate instantaneous blade loadings. The cascade was set for an incidence of 10 dg. The data were acquired on three stationary blades on each side of the middle blade that was oscillated at an amplitude of 0.6 dg. The matrix of test conditions covered inlet Mach numbers of 0.5, 0.8, and 1.1 and the oscillation frequencies of 200, 300, 400, and 500 Hz. A simple quasi-unsteady two-dimensional computer simulation was developed to aid in the running of the experimental program. For high Mach number subsonic inlet flows the blade pressures exhibit very strong, low-frequency, self-induced oscillations even without forced blade oscillations, while for low subsonic and supersonic inlet Mach numbers the blade pressure unsteadiness is quite low. The amplitude of forced pressure fluctuations on neighboring stationary blades strongly depends on the inlet Mach number and forcing frequency. The flowfield behavior is believed to be governed by strong nonlinear effects, due to a combination of viscosity, compressibility, and unsteadiness. Therefore, the validity of the quasi-unsteady simplified computer simulation is limited to conditions when the flowfield is behaving in a linear, steady manner. Finally, an extensive set of unsteady pressure data was acquired to help development and verification of computer codes for blade flutter effects.
Turbomachinery Dual Rotor-Bearing System Analysis
Authors: Chiang Hsiao-Wei D. , Hsu Chih-Neng , Jeng Wes , Tu Shun-Hsu , Li Wei-Chen
Published: February 2009

It is very common for aircraft engines to have dual rotor or even triple rotor designs. Due to the complexity of having multiple rotor design, the transfer matrix methods have used in the past to deal with multiple rotor-bearing systems. However, due to transfer matrix method’s assumptions, sometimes resulted in numerical stability problems or root-missing problems. The purpose of this paper is to develop a systematic theoretical analysis of the dynamic characteristics of turbomachinery dual rotor-bearing systems. This dual rotor-bearing system analysis will start with a finite element (FEM) rotor-bearing system dynamic model, then using different methods to verify the analysis results including critical speed map and bearing stiffness. In an inertia coordinate system, a general model of continuous dual rotor-bearing systems is established based on a lagrangian formulation. Gyroscopic moment, rotary inertia, bending and shear deformations have been included in the model. From a point of view of the systematic approach, a solution of the finite element method is used to calculate the critical speeds by several different methods, which in turn can help to verify this dual rotor-bearing system approach. The effects of the speed ratio of dual rotors on the critical speed will be studied, which in turn can be used as one of the dual rotor design parameters. Also, both critical speeds are in effect functions of dual rotor speeds. Finally, the bearing stiffness between high speed and low speed shafts not only affect the critical speeds of the dual rotor system, but also affect the mode shapes of the system. Therefore, the bearing stiffness in between is of even greater importance in turbomachinery dual rotor or multiple rotor design.
The Effect of Milling Process Induced Coarse Surface Texture on Aerodynamic Turbine Profile Losses
Authors: Harbecke Ulrich G. , Riess Walter , Seume Joerg R.
Published: February 2009

Production time and costs of milled turbine blades can be significantly reduced by increasing the spacing of the cutter paths. In order to quantify the effect of the resulting coarse milling groove texture on profile losses, two different turbine cascades with various cutter path parameters were investigated in a linear cascade wind tunnel. It was found that neither the milling groove spacing nor the stagger angle measured between the grooves and the core flow direction affect the profile loss significantly in the range of typical industrial applications. Therefore, coarsely milled surfaces may be used for cost reduction within the milling parameter ranges investigated.
The Effect of Secondary Air Injection on the Performance of a Transonic Turbine Stage
Authors: Girgis S. , Vlasic E. , Lavoie J.-P. , Moustapha S. H.
Published: February 2009

This paper presents results of rig testing of a transonic, single stage turbine with various modifications made to the injection of secondary air into the mainstream. Results show that significant improvements in stage efficiency can be realized by optimizing the injection of upstream disk purge and rotor upstream shroud leakage flow into the mainstream flow. Results of CFD simulations of the rotor upstream disk purge flow test conditions and closely simulated test geometry agree well with test data.
Axisymmetric Endwall Contouring in a Four-Stage Turbine: Comparison of Experimental and Numerical Results
Authors: Bohn Dieter E. , Su¨rken Norbert , Yu Qing , Kreitmeier Franz
Published: February 2009

Secondary flows and leakage flows lead to complex vortex structures in the 3-D flow field of a turbine blading. Aerodynamic losses are the consequence. Reducing these aerodynamic losses by axisymmetric endwall contouring is the subject of a current experimental and numerical investigation of the flow field in a 4-stage test turbine with repeating stages. Numerical 4-stage simulations for the reconstructed turbine with an axisymmetric off-set arc endwall contour at the casing have been performed and compared to corresponding numerical investigations of the original machine without endwall modifications. The 3-D flow fields have been calculated by application of a steady 3-D Navier-Stokes code. Based on these results the experimental setup is modified to the off-set arc endwall design. The characteristics of the reconstructed machine are measured and compared to the original test rig. Special emphasis is put on the determination of the aerodynamic efficiencies over the four stages. For a detailed assessment of the radial and spanwise flow field properties inside the blading, 5-hole pressure probes are used for steady flow measurements in the narrow axial gaps before and after the 3rd stage. Finally, the measured radial distributions of the flow field properties and the machine characteristics are compared to the corresponding numerical predictions. All results show a significant positive influence of the endwall contouring on the radial distribution of the flow angle, the pressure field and the aerodynamic efficiency.
Experimental Study of Rotating Stalls in a Four-Stage Axial Compressor
Authors: Levy Y. , Pismenny J. , Reissner A. , Riess W.
Published: February 2009

The relationships between the frequencies of pressure oscillation ωOSC and the rotor speed (frequencies of rotor rotation) ωRR, as well as between the phases of pressure oscillation and geometrical angles of the sensor locations on the compressor casing (in the transverse cross-section) were determined experimentally. In addition, the phase–location relation permitted determination of the number of stall cells under established rotating stall. Literature on rotating stall in axial compressors typically refers to rotating stall with frequencies less than the rotor speed. This paper is concerned with two types of rotating stall, observed during experiments in a four-stage axial compressor, operating at the same rotor speed, n/nd = 0.95, where n is the rotor speed and nd the rotor data-sheet speed. The rotating stall frequencies were both, smaller and larger than the rotor speed. The relationships between ωOSC and ωRR were determined by four methods: directly from the time diagram of the pressure oscillation, from the diagrams of pressure variation in space and time, from the autocorrelation characteristics, and from the frequency characteristics of the pressure signals. All methods indicated values of ωOSC/ωRR in the form of integer ratios, 3:7 and 11:2. The phases of pressure oscillation in the transverse cross-section are equal to the sensor angles in compressor stator (in the case ωOSC/ωRR = 3:7) or are three times larger (in the case ωOSC/ωRR = 11:2), in accordance with the classical theory of single-cell and three-cell configurations of rotating stall, respectively.
Investigation of Off-Design Performance of Vaned Diffusers in Centrifugal Compressors: Part I — A Channel-Wedge Diffuser
Authors: Oh JongSik
Published: February 2009

Experimental and numerical investigations of the off-design performance of a simple channel-wedge diffuser in a small centrifugal compressor are presented. Surge and choke conditions as well as design point are considered using somewhat limited range of experimental data and also supplementary 3D CFD results. Some critical meanline design parameters’ behavior is investigated numerically, to render the basis for improved modelings in the meanline performance prediction.
CFD Applications to Industrial Centrifugal Compressor Design
Authors: Arnone Andrea , Bonaiuti Duccio , Boncinelli Paolo , Ermini Mirco , Milani Alberto , Baldassarre Leonardo , Camatti Massimo
Published: February 2009

The aerodynamic redesign of an industrial transonic centrifugal impeller by means of CFD techniques is presented here. The computational procedure was validated by comparing numerical predictions of efficiency and work input coefficient to data from experimental tests on two different typologies of impellers: a low flow coefficient subsonic radial impeller and a high flow coefficient one. Three–dimensional, fully viscous computations were used to investigate the transonic impeller aerodynamic performance in terms of both the characteristic curves and details of the flow structure, suggesting possible improvements in the design. In order to standardize the redesign process of 3D impellers, a number of geometrical parameters, capable of describing the main features of the geometry, were identified. The original configuration was modified by varying the values of such parameters, and the impact of changes was assessed by means of 3D computations. As a result, the designer would be able to recognize which parameters have greater influence, and understand the physical effect of each change. This made it possible to establish some design rules to be exploited in future design processes.
Microturbine Recuperator Manufacturing and Operating Experience
Authors: Treece Bill , Vessa Phil , McKeirnan Robert
Published: February 2009

Capstone Turbine Corporation has produced thousands of recuperated microturbines since 1998. This paper will discuss the manufacturing and field operating experience with these recuperators for microturbines less than 100kW.
The ACTE Spiral Recuperator for Gas Turbine Engines
Authors: Antoine Hubert , Prieels Luc
Published: February 2009

A new recuperator is now being introduced for small and micro-turbine applications. These applications are characterized by low pressure ratios, exhaust gas temperatures that are suitable for use with stainless steel, and a limited allowance for leakage that does not impair the performance. However high reliability is required, because microturbines typically experience 4000 start/stop cycles during their life, and have to be totally reliable when supplying electricity for applications that are independent of the grid. Recuperated gas turbines have a history of expensive installations, prone to cracking under thermal shocks. The ACTE recuperator has been specifically designed for reliablity, compactness and low cost. This paper shows how these seemingly conflicting requirements are met in the ACTE design.
The Effects of Incondensable Gases on H2/O2 Cycle Performance
Authors: Gambini M. , Guizzi G. L. , Vellini M.
Published: February 2009

In this paper a method to evaluate the expansion of condensing steam in presence of incondensable gases is presented. The expansion of such a mixture involves thermodynamic processes very different from those related to the expansion of pure steam (as it happens in conventional steam power plants) or to the expansion of a gaseous mixture without steam condensation (as it happens in gas turbine power plants, combined and mixed cycles). In this paper these thermodynamic processes are investigated and an evaluating method is developed. In particular using this method it is possible to evaluate the excess turbine back pressure, that is the pressure increase with respect to the steam saturation pressure, and the specific expansion work of the mixture. The proposed method is then applied in order to evaluate the performance of an hydrogen/oxygen (fuel/oxidiser) cycle, where the presence of incondensable gases into condensing steam is unavoidable owing to the processes that give H2 from fossil fuels and O2 from air. The results of the developed investigation confirm that the presence of incondensable gases can not be neglected for a realistic evaluation of H2/O2 cycle performance.
Genetic Optimization of Steam Injected Gas Turbine Power Plants
Authors: Akmandor Ibrahim Sinan , O¨ksu¨z O¨zhan , Go¨kaltun Sec¸kin , Bilgin Melih Han
Published: February 2009

A new methodology is developed to find the optimal steam injection levels in simple and combined cycle gas turbine power plants. When steam injection process is being applied to simple cycle gas turbines, it is shown to offer many benefits, including increased power output and efficiency as well as reduced exhaust emissions. For combined cycle power plants, steam injection in the gas turbine, significantly decreases the amount of flow and energy through the steam turbine and the overall power output of the combined cycle is decreased. This study focuses on finding the maximum power output and efficiency of steam injected simple and combined cycle gas turbines. For that purpose, the thermodynamic cycle analysis and a genetic algorithm are linked within an automated design loop. The multi-parameter objective function is either based on the power output or on the overall thermal efficiency. NOx levels have also been taken into account in a third objective function denoted as steam injection effectiveness. The calculations are done for a wide range of parameters such as compressor pressure ratio, turbine inlet temperature, air and steam mass flow rates. Firstly, 6 widely used simple and combined cycle power plants performance are used as test cases for thermodynamic cycle validation. Secondly, gas turbine main parameters are modified to yield the maximum generator power and thermal efficiency. Finally, the effects of uniform crossover, creep mutation, different random number seeds, population size and the number of children per pair of parents on the performance of the genetic algorithm are studied. Parametric analyses show that application of high turbine inlet temperature, high air mass flow rate and no steam injection lead to high power and high combined cycle thermal efficiency. On the contrary, when NOx reduction is desired, steam injection is necessary. For simple cycle, almost full amount of steam injection is required to increase power and efficiency as well as to reduce NOx. Moreover, it is found that the compressor pressure ratio for high power output is significantly lower than the compressor pressure ratio that drives the high thermal efficiency.
Maximum Bladed Disk Forced Response From Distortion of a Structural Mode
Authors: Kenyon J. A. , Griffin J. H. , Feiner D. M.
Published: February 2009

A method is presented for obtaining maximum bladed disk forced response from distortion of a structural mode. It is shown that maximum response from mode distortion in a bladed disk occurs when the harmonic components of a distorted mode superimpose in a certain manner, causing localization of the mode and strong response in a particular blade. In addition, it is shown that the response of an intentionally mistuned system with maximum response does not change significantly when small random mistuning is added to the system. A method is described for calculating the structural mistuning necessary to obtain the distorted mode that gives maximum response. The theory is validated numerically.
Wake, Shock and Potential Field Interactions in a 1.5 Stage Turbine: Part II — Vane-Vane Interaction and Discussion of Results
Authors: Miller R. J. , Moss R. W. , Ainsworth R. W. , Harvey N. W.
Published: February 2009

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighbouring blade rows is investigated with the individual effects of wake, shock and potential field interaction being determined. Two test geometries are considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high-pressure stage but with a vane located in the downstream duct. Both tests were conducted at engine-representative Mach and Reynolds numbers and experimental data was acquired using fast-response pressure transducers mounted on the mid-height streamline of the HP rotor blades. The results are compared to time-resolved computational predictions of the flowfield in order to aid interpretation of experimental results and to determine the accuracy with which the computation predicts blade interaction. In the first half of this paper it is shown that, in addition to the two main interaction mechanisms (upstream vane-rotor and rotor-downstream vane interactions, presented in Miller et al. [1]) a third interaction occurs. This new interaction mechanism is shown to be caused by the interaction between the downstream vane’s potential field and the upstream vane’s trailing edge potential field and shock. The unsteady rotor surface static pressure fluctuations caused by this interaction are shown to occur on the late rotor suction surface at a frequency corresponding to the difference in the numbers of upstream and downstream vanes. The second part to the paper discusses the mechanisms that cause vane-rotor-vane interaction. The rotor’s operating point is periodically altered as it passes the downstream vane. It is shown that for a large downstream vane, the flow conditions in the rotor passage, at any instant in time, are close to being steady state.
Effects of Riblets on the Loss Behavior of a Highly Loaded Compressor Cascade
Authors: Boese Matthias , Fottner Leonhard
Published: February 2009

An experimental investigation of the influence of riblet surface structures on the loss behavior of a highly loaded compressor cascade V103-180 featuring a large chord length for high spatial resolution of the flow phenomena was performed. The cascade experiments were carried out at the High Speed Cascade Wind Tunnel of the University of the Armed Forces Munich in order to simulate realistic Mach and Reynolds numbers. The riblets used for the first investigation are of symmetric v-groove type with heights of 0.0762, 0.1143 and 0.1524 mm, respectively [1]. With two total pressure probes simultaneously traversed over one pitch behind the center airfoil, the local total pressure difference between the structured and the smooth blade is determined. From these measurements, the total pressure loss coefficient can be evaluated. For a better understanding of the flow phenomena, the profile pressure distribution is measured for the smooth and the structured blade. Boundary layer calculations were performed in order to optimise the riblet size for the design conditions of the compressor cascade. Resulting from the measurements an optimised riblet configuration (size and shape) has been manufactured and transferred to the cascade. Further flow measurements have been performed in order to evaluate the total pressure loss coefficient. Additional insight into the flow phenomena of the boundary layer has been achieved by laser-two-focus measurements. The experimental results indicate that the riblets mainly influence the suction side boundary layer behaviour. The ideal dimensionless groove height is obtained h+ = 9 leading to a reduction of the loss coefficient of 6–8%. Values of h+ > 20 cause an increase of the loss coefficient due to the development of a turbulent boundary layer separation.
Recognising the Viability of Cooling Gas Turbine Inlet Air in Colder Regions by Using Low Pressure Fogging Techniques
Authors: Confurius John
Published: February 2009

The profits that can be gained by use of inlet air cooling on gas turbines has been recognised for quite some time now and the systems installed throughout the world have shown the users in the gas turbine field that cooling indeed can be used to boost power at times when the ambient temperature reaches or exceeds the ISO rating temperature of the gas turbine. Drawback however being that the initial investment asked of the gas turbine user is rather large thus only justifying a cooling system in regions where the outdoor temperatures exceed the ISO rating time and again due to the climate in that region. Lately gas turbine users in colder climates have become interested in power augmentation during their short summer, however there is no justification for an investment like necessary when installing one of the presently available systems on the market. As the question reached us from more and more of our clients it stimulated us to go out and search for a low-investment solution to this problem. This resulted in the world’s first low pressure gas turbine inlet cooling system.
Investigation of Unsteady Aerodynamic Blade Excitation Mechanisms in Transonic Turbine Stages
Authors: Laumert Bjo¨rn , Ma˚rtensson Hans , Fransson Torsten H.
Published: February 2009

This paper presents a study of the blade pressure perturbation levels and the resulting rotor blade force in three high-pressure transonic turbine stages, based on three-dimensional unsteady viscous computations. The aim is to identify stage characteristics that correlate with the perturbation strength and degree of force realization on the rotor blades. To address the effects of off-design operation, the computations were performed at high subsonic, design and higher vane exit Mach number operating conditions. Furthermore spanwise variations in pressure levels and blade force are addressed. In our investigation the RMS of the pressure perturbations integrated in both time and along the blade surface is utilized as a global measure of the blade pressure perturbation strength on the rotor blade surface. The relative strength of the different pressure perturbation events on the rotor blade surface is also investigated. To obtain information about the relative strength of events related to the blade passing frequency the pressure field is Fourier decomposed in time at different radial positions along the blade arc-length. With the help of the observations and results from the blade pressure study, the radial variations of the unsteady blade force are addressed.
Mode Shape Sensitivity of the High Pressure Turbine Rotor Excitation Due to Upstream Stators
Authors: Jo¨cker Markus , Fransson Torsten H.
Published: February 2009

The excitability of single rotor blade mode shapes due to the excitations by upstream stators in high-pressure turbine stages is subject of the present work. An evaluation of unsteady aerodynamic analyses of the stator-rotor interaction towards their sensitivity to the rotor blade mode shape is presented and applied. The unsteady aerodynamic analyses were performed at midspan sections with a well validated 2D/Q3D hybrid Euler/Navier Stokes non-linear flow solver (UNSFLO). The mode shape is parametrized by a torsion axis location in the plane of the blade section, which allows the construction of excitability maps as a function of 2D rigid body mode shapes. Excitability itself is derived from a generalized force analysis. The evaluation demonstrates the high sensitivity of excitability to the mode shape, which suggests that only small modifications in mode shape can significantly change the risk of blade mode excitation. It also highlights the central importance of the relative phase of unsteady blade pressure harmonic. Changes in axial gap can significantly modify the excitability and transform highly excited modes to less excited modes and vice versa. The variation of rotational speed (−5% to +10%) did not show remarkable changes in the mode excitability of the investigated rotor.
Unsteady Flow Simulations of a Transonic Nozzle and Cascade for a Time-Dependent Boundary Flow
Authors: Turkbeyler Erdal
Published: February 2009

In this study we investigate unsteady compressible internal flow caused by flow fluctuations at an inlet or outlet flow-boundary. A finite-volume time-marching method has been developed for the unsteady flow analysis. This paper presents the proposed method and reports the results of a numerical investigation into the effects of a time-varying back pressure to a two-dimensional transonic nozzle and of a pulsating inlet flow to a transonic three-dimensional cascade of tapered blades. The computational model is based on a solution of the unsteady Euler equations for compressible flow. The time accurate solution is advanced by an explicit single-step second order time integration scheme. It has been found that the flow fluctuations at flow boundaries can cause strong unsteady effects on the operation of nozzles and cascades. Two modes of operation have been predicted for the unsteady flow in the nozzle: an upstream moving shock wave (mode-A) and an oscillating shock wave (mode-B). The results for the cascade have shown that the pulsating inlet flow causes the shock wave to originate, to move upstream and weaken over the period; the supersonic region on the blade surface varies continuously. The instantaneous mass flow rates and shock motions have been determined for them; they are important for their design and performance calculations.
Gas Turbine Test Parameters Corrections Including Operation With Water Injection
Authors: Mathioudakis K.
Published: February 2009

Methods for correcting data from gas turbine acceptance testing are discussed, focusing on matters which are not sufficiently covered by existing standards. First a brief outline is presented of the reasoning on which correction curves are based. Typical performance correction curves are shown together with the method of calculating mass flow rate and turbine inlet temperature from test data. A procedure for verifying guarantee data at a specific operating point is then given. Operation with water injection is then considered. Ways of correcting performance data are proposed, and the reasoning of following such a procedure is discussed. Corrections for water amount as well as power and efficiency are discussed. Data from actual gas turbine testing are used to demonstrate how the proposed procedure can be applied in actual cases of acceptance testing.
A Study on the CAD/CAM of Curvic Couplings
Authors: Tsai Ying-Chien , Hsu Wei-Yi
Published: February 2009

The curvic coupling was first developed by Gleason Works about sixty years ago. Then, it has been implemented through design and manufacture methods to be used for connecting shafts of gas-turbine engine. The stiffness and the accuracy of centering the coupling have become very important. Therefore, it is necessary to design curvic couplings with the following characteristics: high positioning accuracy, high indexing accuracy, high indexing stiffness, self-centering, and self-improving of indexing accuracy. The process of designing and manufacturing curvic coupling required prior experience as well as a series of trial and error runs. In this paper, mathematical models for designing curvic coupling are developed. First, the parametric and the generalized forms of the quadric surface are presented, and then the mathematical models of cone surface are obtained from the degeneration of quadric surface. Tooth profiles are described by using mathematical model of cone surface in conjunction with design/manufacturing parameters of curvic coupling. The contact patterns are predicted by solving the intersections of all meshing surfaces on the pair of curvic couplings simultaneously. Finally, a computer program is developed for designing curvic couplings with design parameters as input variables to predict the contact patterns of designed curvic couplings and to show them in the form of 3D models. Some design charts are also presented. It is believed that the methodology and the computer program developed in this paper will prove to be an efficient tool for the design and manufacturing of curvic couplings.
Stator-Rotor Interactions in a Transonic Compressor: Part 1 — Effect of Blade-Row Spacing on Performance
Authors: Gorrell Steven E. , Okiishi Theodore H. , Copenhaver William W.
Published: February 2009

Usually less axial spacing between the blade rows of an axial flow compressor is associated with improved efficiency. However, mass flow rate, pressure ratio, and efficiency all decreased as the axial spacing between the stator and rotor was reduced in a transonic compressor rig. Reductions as great as 3.3% in pressure ratio and 1.3 points of efficiency were observed as axial spacing between the blade-rows was decreased from far apart to close together. The number of blades in the stator blade-row also affected stage performance. Higher stator blade-row solidity led to larger changes in pressure ratio, efficiency, and mass flow rate with axial spacing variation. Analysis of the experimental data suggests that the drop in performance is a result of increased loss production due to blade-row interactions. Losses in addition to mixing loss are present when the blade-rows are spaced closer together. The extra losses are associated with the upstream stator wakes and are most significant in the mid-span region of the flow.
Fracture Toughness Testing on Bars Under Opposite Cylinder Loading
Authors: Fett Theo , Munz Dietrich , Thun Gerhard
Published: February 2009

Bars loaded by opposite concentrated forces via rollers are appropriate test specimens for the determination of the fracture toughness, KIc, and the crack resistance curve (R-curve) of ceramic materials. In this paper stress solutions for the proposed test specimens are provided, as well as the stress intensity factor and the T-stress solutions. As practical applications, R-curves are determined for a soft PZT ceramic and several alumina ceramics.
Small-Scale Well-Proven Inherently Safe Nuclear Power Conversion
Authors: Crommelin G. A. K.
Published: February 2009

Over the last few years a number of papers have discussed the progress on studies and thoughts on small-scale nuclear power. Nuclear power conversion systems aiming for the t of the non-utility markets, such as the stand-alone heat generation, Combined Heat & Power production, stand-alone electricity conversion and ship propulsion. The design of these installations must fully comply with the philosophies as are common in these markets, where the expression “the engine is a means to an end” applies. So design to cost, design to be operated by non professional energy producers, to be managed by a pool-management system, maintained, repaired and overhauled by replacement, etc. The paper will discuss such a design. So far all papers mentioned have discussed the gas turbine directly coupled to the heat source. However the helium turbine is considered quite a challenge for the gas turbine industry, so alternatives had to be found. At the moment the possibilities of gas turbines with an indirect heat source (to burn refuse, wood, refinery waste, etc.) are getting much more attention. The paper therefore will discuss how an inherently safe, well proven, nuclear heat source can be coupled by an Intermediate Heat Exchanger to a recuperative, existing but adapted gas turbine.
Performance Simulation of Turboprop Engine Using SIMULINK® Model
Authors: Kong Changduk , Roh Hongsuk
Published: February 2009

A performance simulation model of a turboprop engine, the PT6A-62, which is the power plant of KT-1, was developed to predict the steady-state behaviors using the SIMULINK® model. The SIMULINK model consists of subsystems to represent engine components such as intake, compressor, combustor, compressor turbine, power turbine and exhaust nozzle. For validation, performance parameters calculated using the SIMULINK model were compared with the results using GASTURB model. The steady-state performance analysis using the developed SIMULINK model was performed. Performance parameters, such as the mass flow rate, the compressor pressure ratio, the fuel flow rate, the specific fuel consumption ratio and the turbine inlet temperature, were conducted to evaluate validity of the SIMULINK model at various cases. The first case was the uninstalled condition at various altitudes from sea level to 9144m (30000ft) with fixed M.N. = 0. And the second case was the installed condition at various altitudes from sea level to 7620m (25000ft) with fixed M.N. = 0. The third case was the installed condition at altitudes of 1524m (5000ft) and 3048m (1000ft) and at the M.N. = 0.1, 0.2 and 0.3 in ECS operation ECS. In this investigation, it was confirmed that the results using the SIMULINK model were well agreed with the results using the GASTURB model within maximum 6.5%.
Analytical Blade Row Cooling Model for Innovative Gas Turbine Cycle Evaluations Supported by Semi-Empirical Air Cooled Blade Data
Authors: Torbidoni Leonardo , Massardo Aristide F.
Published: February 2009

With the objective of performing reliable innovative gas-turbine cycle calculations, a new procedure aimed at evaluating blade cooling performance is presented. This complete analytical (convective and film) blade cooling modelling provides the coolant mass flow and pressure loss estimation, and is a useful tool in the field of innovative gas turbine cycle analysis, mainly when alternative fluids are considered. In this case, in fact, the conventional semi-empirical data based on the use of air as traditional coolant and working media are no longer suitable. So the analytical approach represents a way of properly investigating alternative cooling methods and fluids. In the presented analysis the effects of internal blade geometry on cooling performance are summarised by the Z parameter, which also highly affects the coolant flow pressure losses. Since existing technology represents a natural starting point for the assessment of Z, the model is able to automatically estimate a proper value relying only on available semi-empirical data which were established for air-cooled gas turbine blades. When alternative fluids are considered, the same estimated value of Z is still maintained for the calculation, with the result of investigating the performance of existing blade technology for novel operational conditions. This represents an example of how the analytical approach, supported by conventional air cooled blade semi-empirical data, appears as an innovative tool in the analysis of novel gas turbine cycles. In fact, the simulation results for the cooled blade were easily employed on the whole system level (Gas Turbine).