bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-Averaged and Time-Accurate Aero-Dynamics for the Recessed Tip Cavity of a High-Pressure Turbine Blade and the Outer Stationary Shroud: Comparison of Computational and Experimental Results
Authors: Green Brian R. , Barter John W. , Haldeman Charles W. , Dunn Michael G.
Published: November 2008

The unsteady aero-dynamics of a single-stage high-pressure turbine blade operating at design corrected conditions has been the subject of a thorough study involving detailed measurements and computations. The experimental configuration consisted of a single-stage high-pressure turbine and the adjacent, downstream, low-pressure turbine nozzle row. All three blade-rows were instrumented at three spanwise locations with flush-mounted, high frequency response pressure transducers. The rotor was also instrumented with the same transducers on the blade tip and platform and the stationary shroud was instrumented with pressure transducers at specific locations above the rotating blade. Predictions of the time-dependent flow field around the rotor were obtained using MSU-TURBO, a 3D, non-linear, computational fluid dynamics (CFD) code. Using an isolated blade-row unsteady analysis method, the unsteady surface pressure for the high-pressure turbine rotor due to the upstream high-pressure turbine nozzle was calculated. The predicted unsteady pressure on the rotor surface was compared to the measurements at selected spanwise locations on the blade, in the recessed cavity, and on the shroud. The rig and computational models included a flat and recessed blade tip geometry and were used for the comparisons presented in the paper. Comparisons of the measured and predicted static pressure loading on the blade surface show excellent correlation from both a time-average and time-accurate standpoint. This paper concentrates on the tip and shroud comparisons between the experiments and the predictions and these results also show good correlation with the time-resolved data. These data comparisons provide confidence in the CFD modeling and its ability to capture unsteady flow physics on the blade surface, in the flat and recessed tip regions of the blade, and on the stationary shroud.
Axial Fan at Reversal Flow
Authors: Cyrus Va´clav
Published: November 2008

Flow reversal in axial fans is usually performed by the change of revolution direction and by stator vanes turning. Derived relations express the relative position of characteristics curves for reverse and normal flows. The ratio of volume flow rates at these conditions decreases with rotor blade profiles camber (aerodynamic loading) and with flow coefficient. The characteristics of two axial-flow stages A, B with different aerodynamic loading and design flow coefficient were measured on a test rig with external diameter of 600mm. Rotor diffusion factor D at mid-span of stage A and B were DR,m = 0.56 and DR,m = 0.3. Design flow coefficient was φD = 0.6 and 0.4, respectively. Theoretical deductions were confirmed by the experiment. Required volume flow rate ratio (Qrev/Qn ≥ 0.6) was reached only in the case of stage B. Detailed flow fields investigations were carried out in this case with the use of 5-hole conical probes at normal and reverse flows. The mechanism of 3D flows in blade rows could be described in these different fan working regimes.
On Prediction of Tip Leakage Flow and Heat Transfer in Gas Turbines
Authors: Mumic Fadil , Eriksson Daniel , Sunde´n Bengt
Published: November 2008

A numerical study has been performed to simulate the tip leakage flow and heat transfer on the first stage of a high-pressure turbine, which represents a modern gas turbine blade geometry. The low Re k-ω (SST) model is used to model the turbulence. Calculations are performed for both a flat and a squealer blade tip for three different tip gap clearances. The computations were carried out using a single blade with periodic conditions imposed along the boundaries in the circumferential (pitch) direction. The predicted tip heat transfer and static pressure distributions show reasonable agreement with experimental data. It was also observed that the tip clearance has a significant influence on local tip heat transfer coefficient distribution. The flat tip blade provides a higher overall heat transfer coefficient than the squealer tip blade.
A Correlation-Based Transition Model Using Local Variables: Part I — Model Formulation
Authors: Menter F. R. , Langtry R. B. , Likki S. R. , Suzen Y. B. , Huang P. G. , Vo¨lker S.
Published: November 2008

A new correlation-based transition model has been developed, which is based strictly on local variables. As a result, the transition model is compatible with modern CFD approaches such as unstructured grids and massive parallel execution. The model is based on two transport equations, one for intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. The proposed transport equations do not attempt to model the physics of the transition process (unlike e.g. turbulence models), but form a framework for the implementation of correlation-based models into general-purpose CFD methods. Part I (this part) of this paper gives a detailed description of the mathematical formulation of the model and some of the basic test cases used for model validation, including a 2-D turbine blade. Part II of the paper details a significant number of test cases that have been used to validate the transition model for turbomachinery and aerodynamic applications. The authors believe that the current formulation is a significant step forward in engineering transition modeling, as it allows the combination of correlation-based transition models with general purpose CFD codes.
Effects of Tip Gap Film Injection From Plain and Squealer Blade Tips
Authors: Nasir Hasan , Ekkad Srinath V. , Bunker Ronald S. , Prakash Chander
Published: November 2008

The present study investigates the effect of orthogonal tip gap film injection from a plain and squealer tip of a HPT first stage rotor blade. The pressure ratio (inlet total pressure to exit static pressure) for the cascade used was 1.2, and the experiments were run in a blow-down test rig with a four-blade stationary linear cascade. The Reynolds number based on cascade exit velocity and axial chord length was 8.61×105 and the inlet and exit Mach numbers were 0.16 and 0.55, respectively. Five holes are located along the camber line of the blade tip. A transient infrared technique was used to measure the local heat transfer coefficient and film effectiveness from a single transient test. All measurements were made for three blowing ratios of 1.0, 1.5, and 2.0. For all the cases, a small tip gap-to-blade span ratio of 0.5% was used. The squealer depth-to-blade span ratio of 4.16% was used for the squealer. Results show that the film injection has some effect for plain tips but has no effect or negligible effect for squealer tips.
Performance Testing of a Microturbine Generator Set With Twin Rotating Disk Regenerators
Authors: Chiang Hsiao-Wei D. , Wang Chun-Hao , Hsu Chih-Neng
Published: November 2008

An investigation was conducted to study the performance of a 150 kW microturbine generator set with twin rotating disk regenerators, including testing and analyses. Originally designed as a vehicular microturbine engine, twin rotating ceramic disk regenerators were used to dramatically improve fuel consumption by transferring heat energy from the exhaust gas stream to compressor discharge. This microturbine engine consists of a gasifier assembly, a power turbine, a combustor, a regenerator system, a reduction and accessory drive gearbox, and a fuel management system. Because the microturbine engine did not come with the necessary start and control system (including electronic engine control unit), a start sequence was successfully developed and a manual control system installed. This paper reports on testing of the microturbine generator set at different load conditions using load banks. As a parallel effort, a software program was used to predict the performance of the microturbine generator set at different operating conditions in order to compare with the test results.
Effectiveness of a Serpentine Inlet Duct Flow Control Technique at Design and Off-Design Simulated Flight Conditions
Authors: Rabe Angie , Ng Wing , Burdisso Ricardo
Published: November 2008

An experimental investigation was conducted in a static ground test facility to determine the effectiveness of a serpentine inlet duct active flow control technique for two simulated flight conditions. The experiments used a scaled model of a compact, diffusing, serpentine, engine inlet duct developed by Lockheed Martin with a flow control technique using air injection through microjets at 1% of the inlet mass flow rate. The experimental results, in the form of total pressure measurements at the exit of the inlet, were used to predict the stability of a compression system through a parallel compressor model. The inlet duct was tested at cruise condition and angle of attack flight cases to determine the change in inlet performance due to flow control at different flight conditions. The experiments were run at an inlet throat Mach number of 0.55 and a resulting Reynolds number, based on the hydraulic diameter at the inlet throat, of 1.76*105. For both of the flight conditions tested, the flow control technique was found to reduce inlet distortion at the exit of the inlet by as much as 70% while increasing total pressure recovery by as much as 2%. The inlet total pressure profile was input in a parallel compressor model to predict the changes in stability margin of a compression system due to flow control for design and off-design flight conditions. Without flow control, both cases show a reduction in stability margin of 70%. With the addition of flow control, each case was able to recover a significant portion (up to 55%) of the undistorted stability margin. This flow control technique has improved the operating range of a compression system as compared to the same inlet duct without flow control.
Experimental Investigation of Vane Clocking in a One and 1/2 Stage High Pressure Turbine
Authors: Haldeman Charles W. , Dunn Michael G. , Barter John W. , Green Brian R. , Bergholz Robert F.
Published: November 2008

Aerodynamic measurements were acquired on a modern single-stage, transonic, high-pressure turbine with the adjacent low-pressure turbine vane row (a typical civilian one and one-half stage turbine rig) to observe the effects of low-pressure turbine vane clocking on overall turbine performance. The turbine rig (loosely referred to in this paper as the stage) was operated at design corrected conditions using the Ohio State University Gas Turbine Laboratory Turbine Test Facility (TTF). The research program utilized uncooled hardware in which all three airfoils were heavily instrumented at multiple spans to develop a full clocking dataset. The low-pressure turbine vane row (LPTV) was clocked relative to the high-pressure turbine vane row (HPTV). Various methods were used to evaluate the influence of clocking on the aeroperformance (efficiency) and the aerodynamics (pressure loading) of the LPTV, including time-resolved and time-averaged measurements. A change in overall efficiency of approximately 2–3% due to clocking effects is demonstrated and could be observed using a variety of independent methods. Maximum efficiency is obtained when the time-average surface pressures are highest on the LPTV and the time-resolved surface pressure (both in the time domain and frequency domain) show the least amount of variation. The overall effect is obtained by integrating over the entire airfoil, as the three-dimensional effects on the LPTV surface are significant. This experimental data set validates several computational research efforts that suggested wake migration is the primary reason for the perceived effectiveness of vane clocking. The suggestion that wake migration is the dominate mechanism in generating the clocking effect is also consistent with anecdotal evidence that fully cooled engine rigs do not see a great deal of clocking effect. This is consistent since the additional disturbances induced by the cooling flows and/or the combustor make it extremely difficult to find an alignment for the LPTV given the strong 3D nature of modern high-pressure turbine flows.
Experimental Inlet Air Cooling of a 75 kW Gas Turbine
Authors: Banta Andrew
Published: November 2008

An experimental study of gas turbine inlet air cooling was conducted in the Cogeneration Laboratory at California State University, Sacramento (CSUS). The cooling was done using both water sprays and air cooled by an absorption chiller. The primary objectives were to determine the effectiveness of inlet air cooling on a very small gas turbine and compare using water sprays with absorption cooled air. Secondary objectives were to investigate the use of low cost water spray equipment which is typically used in green houses, and the cost effectiveness of absorption cooling with a small turbine. The very small quantities of water, less than 0.006 L/s (0.1 gpm), required to saturate the turbine air flow was difficult to meter. With the low cost spray equipment employed, the only way to accomplish full saturation was to over saturate the air. The gas turbine engine did not respond well to this situation. The lower density of the inlet air caused unstable operation of the compressor resulting in reduced compressor efficiency. With about 2/3 of the turbine work going to the compressor, this loss in efficiency caused the electricity generated to be limited to about half the rated 75 kW. Concerns about damage to the engine caused early termination of these tests. The experiments using air cooled by absorption chilling were more successful but encountered some of the same difficulties. Again, the high humidity and lower density of the inlet air appeared to cause some instability in the compressor. Control of the air temperature proved to be difficult; thus the compressor inlet air was at the chiller discharge temperature, approximately 13 C (55 F). With this arrangement it was possible to operate the engine at full rated capacity which is substantially higher than the 60% fo full load possible with ambient air at approximately 32 C (90 F). In the case of this particular engine, it was concluded that the use of water sprays was not practical and in fact may cause damage. The difficulties of metering very small water quantities would be encountered with any similar size engine. The use of absorption cooling did improve performance but this is a costly solution. The economics of inlet cooling of micro-turbines is very questionable.
Jurassic Gas Turbine Is Brought Back to Life
Authors: Anderson Rodger O.
Published: November 2008

An old Dresser-Clark gas turbine initially installed at a Navy facility in the mid 1950’s keeps producing electric power for its present owner and provides system capacity. Like the “energizer bunny” it keeps going and going and going. Its first home was at a Navy test facility until the early 1980’s. Then it was sold to a small utility in northern Wisconsin where it has been used as a peak shaver and provides system capacity for the utility. This allows the utility to purchase energy at a lower cost from the large utility in the area. In the late 1990’s it suffered some blade damage and also a failed expansion joint. The blades were repaired, however, the expansion joint around the exterior casing is a 360 degree piece and its replacement would require a complete disassembly of the engine. The owner could not justify the expense and was planning to scrap the engine until an alternate solution was presented. An analysis was done to show that an expansion joint was not needed at that casing location if pre-tensioning of other joints were done. Then the solution was to weld a metal band over the joint. This was done for very little cost and the engine was returned to peaking service in late 2002. It continues to perform as it did before the joint failure.
Non-Synchronous Vibration (NSV) Due to a Flow-Induced Aerodynamic Instability in a Composite Fan Stator
Authors: Sanders A. J.
Published: November 2008

This paper describes the identification and prediction of a new class of non-synchronous vibration (NSV) problem encountered during the development of an advanced composite fan stator for an aircraft engine application. Variable exhaust nozzle testing on an instrumented engine is used to map out the NSV boundary, with both choke- and stall-side instability zones present that converge toward the nominal fan operating line and place a limit on the high-speed operating range. Time-accurate three-dimensional viscous CFD analyses are used to demonstrate the NSV instability is being driven by dynamic stalling of the fan stator due to unsteady shock-boundary layer interaction. The effects of downstream struts in the front frame of the engine are found to exasperate the problem, with the two fat service struts in the bypass duct generating significant spatial variations in the stator flow field. Strain gage measurements indicate that the stator vanes experiencing the highest vibratory strains correspond to the low static pressure regions of the fan stator assembly located approximately 90 degrees away from the two fat struts. The CFD analyses confirm the low static pressure sectors of the stator assembly are the passages in which the flow-induced NSV instability is initiated due to localized choking phenomena. The CFD predictions of the instability frequency are in reasonable agreement with the strain gage data, with the strain gage data indicating that the NSV response occurs at a frequency approximately 25% below the frequency of the fundamental bending mode. The flow patterns predicted by the CFD analyses are also correlated with the results of an engine flow visualization test to demonstrate the complex nature of the fan stator flow field.
Numerical Prediction of Non-Reacting and Reacting Flow in a Model Gas Turbine Combustor
Authors: Davoudzadeh Farhad , Liu Nan-Suey
Published: November 2008

The three-dimensional, viscous, turbulent, reacting and non-reacting flow characteristics of a model gas turbine combustor operating on air/methane are simulated via an unstructured and massively parallel Reynolds-Averaged Navier-Stokes (RANS) code. This serves to demonstrate the capabilities of the code for design and analysis of real combustor engines. The effects of some design features of combustors are examined. In addition, the computed results are validated against experimental data. The numerical model encompasses the whole experimental flow passage, including the flow development sections for the air annulus and the fuel pipe, twelve channel air and fuel swirlers, the combustion chamber, and the tail pipe. A cubic non-linear low-Reynolds number K-e turbulence model is used to model turbulence, whereas the eddy-breakup model of Magnussen and Hjertager is used to account for the turbulence combustion interaction. Several RANS calculations are performed to determine the effects of the geometrical features of the combustor, and of the grid resolution on the flow field. The final grid is an all-hexahedron grid containing approximately two and one half million elements. To provide an inlet condition to the main combustion chamber, consistent with the experimental data, flow swirlers are adjusted along the flow delivery inlet passage. Fine details of the complex flow structure such as helicalring vortices, recirculation zones and vortex cores are well captured by the simulation. Consistent with the experimental results, the computational model predicts a major recirculation zone in the central region immediately downstream of the fuel nozzle, a second recirculation zone in the upstream corner of the combustion chamber, and a lifted flame. Further, the computed results predict the experimental data with reasonable accuracy for both the cold flow and for the reacting flow. It is also shown that small changes to the geometry can have noticeable effects on the combustor flowfield.
Internal Cooling in 4:1 AR Passages at High Rotation Numbers
Authors: Zhou Fuguo , Lagrone Jonathan , Acharya Sumanta
Published: November 2008

Heat transfer and pressure drop measurements are reported for a rotating 4:1 aspect ratio (AR, (the ratio of the width of leading/trailing wall to the height of sidewalls) smooth coolant passage for Reynolds number in the range of 10,000–150,000, rotation number in the range of 0–0.6, and density ratios between 0.1–0.2. The measurements are performed for both 90° and 45° orientations of the coolant passage relative to the rotational axis. These measurements are done in a rotating heat transfer rig utilizing segmented foil heated elements and thermocouples, with slip rings providing the interface between the stationary and rotating frames. Results indicate that beyond specific Ro values (different values for the inlet and outlet passages) the expected trends of heat transfer enhancement on the destabilized surface and degradation on the stabilized surface are reversed. The inlet leading surface shows enhancement with Ro only at low Re, and shows degradation at high Re. Increasing density ratio enhances the heat transfer on all walls. Orientation of the coolant passage relative to the rotational axis has an important effect, with the 45° orientation reducing the heat transfer on the destabilized surface and enhancing it on the stabilized surface.
Direct Numerical Simulation of a Film Cooling Jet
Authors: Muldoon Frank , Acharya Sumanta
Published: November 2008

Direct Numerical Simulation (DNS) of a film cooling jet is presented. In DNS no turbulence models are introduced, and the turbulent length scales in the flow field are fully resolved. Therefore the calculations are expected to provide an accurate representation of reality, and the numerical data can be used to understand the flow physics and to compute turbulence budgets. In this paper, a DNS for an inclined jet at a jet Reynolds number of 3068 is presented. Statistics for the various budgets in the turbulence kinetic energy and dissipation rate equations are computed and presented to provide a basis for improvements to the turbulence models. A new wall function based on DNS results for a film cooling flow is presented.
Multi-Objective Robust Optimization of Air Engine Using IOSO Technology
Authors: Igor Egorov N. , Gennady Kretinin V. , Igor Leshchenko A. , Sergey Kuptzov V.
Published: November 2008

This paper demonstrates the multi-objective optimization of air engine in aircraft system using either Deterministic or Robust Design Optimization statements. The goal is to obtain the Pareto-optimum frontier for the air engine and aircraft parameters. Performance characteristics of engine include the following: specific fuel consumption; thrust, with external resistance included, for any flight operating modes of aircraft; weight; the engine size parameters; engine’s life period; level of engine noise; and maintenance costs of the engine. Performance characteristics of an aircraft include passenger-per-kilometer fuel consumption, direct maintenance expenditures, maintenance cost, terrain noise level, take-off runway length, maximum flight altitude, maximum flight Mach number for different parameters of the operation process of the engine, and the various aircraft geometry parameters. While solving a problem of optimizing an engine in an aircraft system, conditions may exist where values of objective function and constraints can not be calculated. This can be caused by both the unfeasibility of a whole system for certain combinations of design variables, and the instability of numerical schemes used as mathematical models. Such conditions can even lead to a crash of the mathematical model. The existence of such areas usually substantially complicates the solution of optimization tasks and in some cases makes it impossible to find optimal solution. The paper illustrates that IOSO algorithms can deal with such cases very efficiently. This paper presents the result of the probabilistic statement of the multi-objective optimization problem, which decreases technical risks when developing modern objects and systems with the highest level of efficiency.
A Study of Active Rotor-Blade Vibration Control Using Electro-Magnetic Actuation: Part 1 — Theory
Authors: Christensen Rene´ H. , Santos Ilmar F.
Published: November 2008

This is the first paper in a two-part study on active rotor-blade vibration control using electro-magnetic actuation. Emphasis is focused on theoretical aspects of implementing active control into coupled rotor-blade systems, more precisely, into systems where rotor lateral motion is coupled to blades flexible motion. The theoretical investigation includes controllability and observability analyses of such a system in order to determine optimal actuator and sensor placement. An analysis methodology based on modal analysis in time-variant systems, due to the periodic time-variant nature of this kind of system, is presented. The method takes into account the strong vibration coupling which has a significant effect on the controllability and observability of bladed rotor systems. The analyses show that, for tuned bladed rotors, actuators will have to be located within the blades in order to make all vibration modes controllable. However, if the system is deliberately mistuned, rotor and blade vibrations can be controlled using shaft-based actuation and sensing only. Moreover, a controller design procedure for obtaining active periodic time-variant modal controllers, capable to cope with the time-periodicity of the system, is presented. Controllers are designed for a tuned as well as a deliberately mistuned system. The tuned system is controlled using both blade and shaft actuators while the mistuned system is controlled using only shaft actuation. Numerical simulations are provided to show the efficiency of the designed controllers.
Concept of New, Dual-Path Steam System for Dual-Mode Operation
Authors: Uzunow N. , Furutani H.
Published: November 2008

A concept of new steam system for hydrogen energy storage application is presented in this paper. Its special, dual-path configuration enables operation in two basic modes. During the nighttime demand trough, one-source mode can be used and the system can be operated as a conventional water-steam cycle. During the daytime demand peak, a second, high-quality heat source in the form of hydrogen-oxygen combustion can be introduced, increasing the system output and efficiency. This concept seems to solve the two most serious problems of hydrogen turbine systems, which are the fuel cost and the requirement of continuous operation. Initial calculations for the proposed system combined with an advanced gas turbine confirmed that a remarkable performance is obtainable under manageable conditions. In one-source mode of operation, the performance corresponds to that of the newest advanced combined cycles, while in two-source mode the overall output is doubled, the electric efficiency exceeds 59% HHV (67% LHV), and the efficiency for heat supplied by hydrogen into the increment of output exceeds 62% HHV (73% LHV). An example of hydrogen energy storage cycle is also discussed in the paper.
Influence of Stator Clocking on the Unsteady 3-Dimensional Flow in a 2-Stage Turbine
Authors: Bohn Dieter , Ren Jing , Sell Michael
Published: November 2008

To give insight into the influence of the clocking and the stator-rotor interaction, the unsteady 3D flow through a two-stage turbine is simulated numerically, using a time marching Navier-Stokes computer code with a sliding mesh approach. A stator clocking is applied to the second stator vane over several circumferential positions. The numerical results are compared with the experimental one to check the availability of the code. Clocking effects on the turbine performance, wake trajectories and outlet flow field is focused. A relative efficiency variation of about 0.52% is concluded among clocking positions. A link between the turbine efficiency and the wake trajectories on the midspan is shown based on the presented clocking analysis in the 3D unsteady flow field. The detailed illustration of the outlet flow field shows that the influence of the clocking at the outlet is focused on the temperature distribution.
A Study of Active Rotor-Blade Vibration Control Using Electro-Magnetic Actuation: Part 2 — Experiments
Authors: Christensen Rene´ H. , Santos Ilmar F.
Published: November 2008

This is the second paper in a two-part study on active rotor-blade vibration control using electro-magnetic actuation. This part is focused on experimental aspects of implementing active control into coupled rotor-blade systems. A test rig, equipped with electro-magnetic actuators and various sensors to monitor the system vibration levels, is specially designed. The aim of the rig is to demonstrate the feasibility of controlling rotor and blade vibrations using a modal control scheme capable to handle the time-periodicity of this kind of system. Two different active controlled rotor-blade systems are considered in the present study: (a) a tuned bladed rotor, controlled with help of actuators attached to the rotating blades; (b) a deliberately mistuned bladed rotor controlled only by shaft based actuation. Experimental tests are carried out for both systems. Some experimental problems regarding control implementation are identified and discussed especially when the controller order and the number of actuators in the centralized control scheme become too high. For the blade mistuned system, controlled by using only rotor/hub based actuation, the controller works well. Despite of implementation difficulties of the modal control scheme due to high sensitivity to model imperfections, it can be concluded that the periodic modal control methodology applied to controller design works well and can become a very useful and powerful tool for designing mechatronic machine elements.
Development and Experimental Testing of a Pilot Burner for DLN Combustors
Authors: Riccio G. , Piazzini S. , Adami P. , Martelli F. , Tanzini G. , Carrai L. , Spadi A.
Published: November 2008

Different geometrical modifications have been investigated and experimentally tested to improve a pilot burner for low emission industrial gas turbine combustors. Results of the ongoing collaboration between the DE of Florence and the Italian electric company ENEL are reported. The activity is dedicated to the improvement of the pilot burner to extend the operable margin of the engine and to reduce, at the same time, the emissions. The study has been performed mainly by means of experimental investigations both on isothermal flow as on combustion test rig. Results of the activity were employed both to obtain design information about the swirler and injection fuel holes for the pilot burner under investigation. Moreover the post-processing of the experimental data permitted the improvement of the correlation implemented into the 1-D model for the prediction of the injected fuel path. These results were implemented in the routine DoFHIS (Design of Fuel Holes Injection Systems) developed for the analysis/design of injection fuel systems.
The Effect of Impurities in Fuel Grade Dimethyl-Ether on Combustion Characteristics
Authors: Narukawa Kimihito , Koizumi Hiromi , Inoue Hiroshi , Kobayashi Nariyoshi
Published: November 2008

In order to investigate the effect of impurities contained in fuel grade dimethyl-ether on combustion characteristics, laminar burning velocity tests and diffusion flame combustor tests were carried out with various contents of impurities in fuel grade dimethyl-ether (with about 0–9wt% methanol and 0–10wt% moisture). From the laminar burning velocity tests, it was found that the burning velocity of fuel grade dimethyl-ether was slightly slower than that of high purity dimethyl-ether and it was faster than that of methane. This indicates that fuel grade dimethyl-ether has a high potential of flash back, like high purity dimethyl-ether. Moreover, the diffusion flame combustor tests showed that NOx emission decreased when the impurities contained in fuel grade dimethyl-ether were increased, however CO emissions were almost constant, irrespective of the content of impurities. Further, by comparing NOx emissions with various contents of impurities in fuel grade dimethyl-ether, it was clear that NOx emissions could be estimated from the adiabatic flame temperature. From these results, a lot of valuable data regarding impurities content has been obtained, which will assist in the development of a gas turbine combustor for fuel grade dimethyl-ether.
Measurements of Surface Temperature Distribution on a Rotating Disk With Blade Cooling Holes Using Thermochromic Liquid Crystal
Authors: Luo Xiang , Zhang Chong , Xu Guoqiang , Tao Zhi , Ding Shuiting
Published: November 2008

A wide-band thermochromic liquid crystal (TLC) was used in measuring the surface temperature of a rotating disk. The experiments were carried out in a test section with a rotor with 60 blade-cooling holes and heating at rim, a stator with central air inflow. The images of TLC were recorded with only the camera flashlight, and were translated into temperature distribution by hue technique. Results clearly shows that the influence of holes to the temperature field. Isotherms were distorted within distance of 100–150% of hole diameter from the hole’s edge. The distortion develops with the rotating speed.
Design of a Transonic High-Pressure Turbine Stage 2D Section With Reduced Rotor/Stator Interaction
Authors: Vascellari Michele , De´nos Re´my , Van den Braembussche Rene´
Published: November 2008

In transonic turbine stages, the exit static pressure field of the vane is highly non-uniform in the pitchwise direction. The rotor traverses periodically this non-uniform field and large static pressure fluctuations are observed around the rotor section. As a consequence the rotor blade is submitted to significant variations of its aerodynamic force. This contributes to the high cycle fatigue and may result in unexpected blade failure. In this paper an existing transonic turbine stage section is redesigned in the view of reducing the rotor stator interaction, and in particular the unsteady rotor blade forcing. The first step is the redesign of the stator blade profile to reduce the stator exit pitchwise static pressure gradient. For this purpose, a procedure using a genetic algorithm and an artificial neural network is used. Next, two new rotor profiles are designed and analysed with a quasi 3D Euler unsteady solver in order to investigate their receptivity to the shock interaction. One of the new profiles allows reducing the blade force variation by 50%.
Aero-Gasturbine Emission Reduction and Simulation Technology: Philosophy and Approach
Authors: Shakariyants Savad A. , van Buijtenen Jos P. , Visser Wilfried P. J.
Published: November 2008

Aircraft engine technology has gained major advances in the past 40–50 years, steadily bringing significant gains in the reduction of exhaust emissions at the source. However, with the projected increase in air traffic, the cumulative amount of aircraft emissions will still increase. This maintains the need for further progress in developing analytical methods to predict the amount and composition of exhaust gases from aircraft engines to better assess the alternatives for reducing emissions and better inform decision-makers, manufacturers and operators. The Research Project “Aero-Gasturbine Emission Reduction and Simulation Technology”, started at the Delft University of Technology in collaboration with the Dutch National Aerospace Laboratory (NLR) and the Netherlands Ministry of Traffic, is aimed to contribute to the efforts to solve the problem. With the limitations, complexity and costs of emission measurements at operational conditions, the ability to predict engine exhaust emissions by means of analytical tools becomes more urgent for minimizing aircraft engine exhaust gas emissions. This paper presents a philosophy and approach to develop such tools.
Generic Geometry Definition of the Aircraft Engine Combustion Chamber
Authors: Shakariyants Savad A. , van Buijtenen Jos P. , Visser Wilfried P. J.
Published: November 2008

The type and layout of a particular gas turbine combustion chamber are largely determined by engine specifications and, peculiarly for the aircraft application, by the effort to use the available space as effectively as possible. Therefore, large commercial turbofan engine combustors exhibit a great degree of commonality. This commonality is a result of the similarity in working environment, size constraints and also safety, performance, and weight requirements. The objective of the present work is to propose generic relations between combustor overall performance and geometry, in order to develop accurate models for combustion quality and emission studies. Therefore, an algorithm has been developed to produce a generic combustion chamber layout. The algorithm is based on a set of empirical relations, semi-analytical methods, statistical figures and design philosophy. Results have been validated in a case study, showing accurate correspondence with modern turbofan engine combustors. An alternate application of the models may be preliminary sizing or design of aero-engine combustion chambers.
Experimental Investigation of Spatial and Temporal Aspects of the Liquid Fuel Placement in a Swirl Cup at Elevated Pressure
Authors: Becker Julian , Hassa Christoph
Published: November 2008

The kerosene spray generated by a pressure swirl fuel nozzle embedded in a swirling airflow in a swirl cup typical of aeroengine combustors was investigated at different levels of air pressure to assess the counter-acting effects of increasing air density and transfer of centrifugal momentum from airflow to spray. Hardware parameters investigated included air swirl angle and fuel nozzle flow number. Measurement techniques included spray visualization, Phase-Doppler Anemometry (PDA) for spray analysis and Laser-Doppler Anemometry (LDA) for investigation of the air flow field. Operating conditions for PDA measurements were 6, 12, and 18 bar at 700 K. Spray visualizations and LDA measurements were performed at scaled operating conditions. It was found that fuel placement is governed by the presence or absence of a recirculation zone inside the swirl cup and hence by the swirl angle of the airflow. Analysis of temporal aspects of the spray showed the existence of droplet clusters. Configurations characterized by strong swirl furthermore exhibited a preferred frequency of inter-particle times.
Investigation of Flow and Heat Transfer Instabilities in a Rotating Cavity With Axial Throughflow of Cooling Air
Authors: Tian Shuqing , Tao Zhi , Ding Shuiting , Xu Guoqiang
Published: November 2008

To study the instability of flow and heat transfer within the rotation frame, a rotating cavity with air axial throughflow was studied numerically and efforts were focused upon the flow structure evolution with the increase of Rayleigh number. The cavity can be divided into two typical zones: the Rayleigh_Benard-like convection zone occupying the upper cavity and the forced convection zone down under. These two zones interact with each other via the exchange of mass, momentum and energy. Numerical analysis indicated that, for a fixed inlet Reynolds number, there always exists a critical Rayleigh number Rac, below which the flow is stable and over which the flow becomes unstable and time-dependent. Among all the forces in momentum equations, the centrifugal induced buoyancy force was found to be the key factor leading to instability, while the Coriolis force pays its contribution to instability by inducing its occurrence earlier and the flow structure more complicated though it may not lead to instable by itself. The instability originated in the upper R-B-like convection zone develops into the whole region with the increase of Rayleigh number. For the heat transfer, the characteristic distribution of local Nur along the disk surface is remarkably different before and right after the occurrence of instability due to flow structure variation though the averaged Nuav varies slightly. It was found that the heat transfer, however, does experience a sudden increase when the flow instability develops further with Ra increase.
Ansaldo Energia Gas Turbine Operating Experience With Low BTU Fuels
Authors: Bonzani Federico , Pollarolo Giacomo
Published: November 2008

The Gas Turbine market for low BTU fuels has become very important in Italy in the last decade mainly due to the chance for the private utilities to sell power to the grid at higher rates according to a national law (CIP6/1992) specifically dealing with recovery fuel use for gas turbine power generation. Ansaldo Energia has been engaged in three low BTU fuel projects in Italy dealing respectively with IGCC technology and steel mill fuel gas. Each of these plants has its own features which all in all gives a wide range of experiences in development and operation of gas turbine fired with low BTU fuels. The first project is the ISAB Priolo IGCC plant, whereas two V94.2K manufactured by Ansaldo Energia are in operation burning syngas from residual refinery gasification since 1999. Since the presence of fuel impurities coming from the gasifier a new design phase and a test campaign has been necessary to re-design the syngas burner, originally developed by Siemens PG, in order to overcome this problems. The engines are now successfully operating. The second project is the Elettra Servola combined cycle plant whereas a V94.2K manufactured by Ansaldo Energia is in operation since 2000 burning a mixture of steel mill gas and natural gas. During the successfully operation some burner design optimisation has been required in order to meet the industrial process modification. The third project is the ENIPower Ferrera Erbognone IGCC plant is under realisation and the relevant first firing will be expected on next January 2004. The syngas burner test campaign carried out has shown very promising results that have to be confirmed on site. The paper is showing the combustion concept relevant to the combustion system and is giving an overview about the operating experience achieved by Ansaldo Energia in this field mainly focusing on how the main critical aspects have been faced and overcome.
An Investigation of Duct Aspect Ratio Effects on Heat/Mass Transfer in a Rotating Duct With 90° Ribs
Authors: Kim Kyung Min , Kim Yun Young , Rhee Dong Ho , Cho Hyung Hee
Published: November 2008

The effects of duct aspect ratio on heat/mass transfer are investigated. Mass transfer experiments are conducted to obtain detailed local heat/mass transfer coefficients on the leading and trailing surfaces in a rotating two-pass duct with 90°-rib turbulators. The duct has three aspect ratios (W/H = 0.5, 1.0, and 2.0) with a fixed hydraulic diameter (Dh) of 26.7 mm. 90°-rib turbulators are installed on the leading and trailing sides symmetrically. The rib height-to-hydraulic diameter ratio (e/Dh) is 0.056, and the rib height remains constant in all duct cases. The Reynolds number based on the hydraulic diameter is fixed to 10,000 and the rotation number ranges from 0.0 to 0.20. The results show that Sherwood number ratios are 2.5 times higher than the fully developed value in a stationary smooth pipe due to the flow reattachment near ribbed surfaces. The overall heat/mass transfer in the first pass is more enhanced in higher aspect ratio duct because the rib height-to-duct height ratio increases, which results in more turbulated and accelerated flow in the midsections of the ribs. Dean vortices augment heat/mass transfer in the turn and in the upstream region of the second pass. The rotation of duct produces heat/mass transfer discrepancy, having higher Sherwood number ratios on the trailing surface in the first pass and on the leading surface in the second pass. However, the effects of turning region and rotation on heat/mass transfer become less significant with the increment of duct aspect ratio.
Design Improvements of Power Conversion System of Gas Turbine High Temperature Reactor (GTHTR300)
Authors: Takada Shoji , Takizuka Takakazu , Kunitomi Kazuhiko , Yan Xing , Kosugiyama Shinichi
Published: November 2008

The power conversion system for GTHTR300 with a power output 274 MWe was designed to operate on regenerative closed-cycle with the turbine inlet helium gas temperature 850 °C and pressure 7.0 MPa. Horizontal single-shaft, axial-flow turbo-compressor and directly coupled electric generator by diaphragm-coupling are suspended by magnetic bearings. The study aimed to reduce the total mass of the plant by selecting non-inter-cooled-cycle and improving the performance of the main system components. Three-dimensional aerodynamic design of the turbo-compressor predicted high polytropic efficiencies of 93% and 90% respectively, while keeping high surge margin of 30% for compressor, which resulted in net generation efficiency of 45.6%. The turbo-machine rotor, which passed over critical speeds of the bending mode, fulfilled the standard limit of vibration amplitude of 75 μm at the rated rotational speed by optimising stiffness of the magnetic bearings. Plate-fin type recuperator with off-set fin arrangement minimized size and mass with square cross section of 1.2 mm × 1.2 mm, while fulfilling the target temperature effectiveness of 95%.
Shockwave and Noise Abatement of Transonic Fans
Authors: Xu Liping
Published: November 2008

The aerodynamic sources of the forward tone noise of transonic civil fans are analysed. The leading edge shockwave near the rotor tip section is identified as the main source of tone noise. By comparing the tone noise levels of the same fan operating at two different working lines, numerical calculations show that on the lower working line, the main passage shockwave is swallowed and locked into the blade passage, and the fan blades act as a shield to prevent the strong passage shock wave from propagating upstream. The calculations show that, by running the fan at a lower working line, up to 6 db abatement in the blade passing frequency (BPF) tone can be achieved through shielding the shockwave. With three dimensional CFD it is possible to design swept rotors which have desired shockwave structures near the tip region. Fan rotors with different swept leading edges have been designed to study this effect and comparisons in aerodynamics performances as well as the tone noise levels are made. It is predicted that in a swept rotor the leading edge shock strength can be further weakened and up to 5db further reduction in tone noise is possible. With a more secure shockwave shielding, a forward swept rotor has the combination of better aerodynamic performance and better noise abatement feature. The design and test results of a three dimensional fan rotor LNR2, featuring localised forward swept rotor are presented. Rig test results show that although the noise reduction through shock shielding has been demonstrated, the aerodynamics and noise are complicated by the problems specific to such localised forward swept fan.