bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow Evolution Through a Turning Mid Turbine Frame With Embedded Design
Authors: Bader Pascal , Sanz Wolfgang , Spataro Rosario , Göttlich Emil
Published: September 2014

The paper discusses the time-averaged flow of a new concept turbine transition duct placed in a two-stage counter-rotating test turbine located at the Institute for Thermal Turbomachinery and Machine Dynamics of Graz University of Technology.

As a possible architecture for the turbine transition duct of future engines, the structural vanes carrying the bearing loadings can be integrated with the first low pressure vane row in one aerodynamically optimized wide-chord vane. Such architecture is also called Turning Mid Turbine Frame (TMTF).

In order to increase the flow uniformity and to decrease the unsteady content of the flow at the inlet of the LP rotor, a baseline TMTF was redesigned embedding two splitter vanes into the strut passage. The discussion on the flow field is based on numerical results obtained by a CFD code and validated by aerodynamic measurements.

The flow structures moving from the outlet of the transonic high pressure stage are observed propagating towards the low pressure stage. In particular the splitter vanes are seen playing a major role in suppressing the big structures generated by the struts. On the other hand new losses are introduced by the splitter structures. Such structures play a decisive role in the overall component performance and therefore their effect should be properly understood in the design phase.

This work provides a deep insight into the flow physics of TMTF designed with an embedded concept for next generation aero-engines. This configuration is seen to be a promising architecture in order to compact the engine size while keeping the components performance high.
Crack Propagation Life Calculation of an Aircraft Compressor Blade due to Bird Ingestion
Authors: Jammi Srinivasa R. , Rzadkowski R.
Published: September 2014

Bird ingestion is simulated by blade passage blocks in the incoming flow and the pressure field is obtained from a CFD code. The alternating pressure field corresponding to the identified critical speed of the first stage rotor blade is obtained from an FFT. A nonlinear damping model is developed using Lazan’s hysteresis law; the equivalent viscous damping model is determined as a function of reference strain amplitude in the given mode of vibration at the rotational speed. An iterative process is developed with the nonlinear damping model and the resonant stress and location is determined. The Fracture Mechanics approach is used to estimate the crack propagation life of the blade.
Exploitation of Measured Flame Transfer Functions for a Two-Phase Lean Fuel Injector to Predict Thermoacoustic Modes in Full Annular Combustors
Authors: Macquisten M. A. , Whiteman M. , Stow S. R. , Moran A. J.
Published: September 2014

Thermoacoustic instabilities are a limitation on the operability of any combustion system, especially under lean fuel conditions. The ability to avoid or eliminate rumble, especially at an early stage of the development of a combustion system, is a useful capability. The occurrence of thermoacoustic modes can be predicted by an acoustic network of the combustion system, where the aerodynamic/flame interaction is described by a flame transfer function. In the EC funded KIAI project a series of tasks were performed to measured flame transfer functions of lean fuel injectors with the aim of predicting thermoacoustic Eigen modes in a full annular combustion rig.

The linear flame transfer functions, of the injector, were measured at Cambridge University on a single intermediate pressure sector siren rig via OH* and CH* chemiluminescence and unsteady pressure measurements. These flame transfer functions were implemented in a low order acoustic network of the rig in the form of an inverse FFT method. The acoustic network uses linear perturbation theory, where the Eigen modes are solved by satisfying the acoustic boundary conditions. Alternatively, the acoustic network can be used to predict the forced pressure response of the system. Finally, the network was used to predict the frequencies, stability and spectra in a full annular combustor rig, utilising the same injector.
A Multidisciplinary Approach for the Comprehensive Assessment of Integrated Rotorcraft–Powerplant Systems at Mission Level
Authors: Ali Fakhre , Goulos Ioannis , Tzanidakis Konstantinos , Pachidis Vassilios , d’Ippolito Roberto
Published: September 2014

This paper presents an integrated methodology for the comprehensive assessment of combined rotorcraft–powerplant systems at mission level. Analytical evaluation of existing and conceptual designs is carried out in terms of operational performance and environmental impact. The proposed approach comprises a wide-range of individual modeling theories applicable to rotorcraft flight dynamics and gas turbine engine performance. A novel, physics-based, stirred reactor model is employed for the rapid estimation of nitrogen oxides (NOx) emissions. The individual mathematical models are implemented within an elaborate numerical procedure, solving for total mission fuel consumption and associated pollutant emissions. The combined approach is applied to the comprehensive analysis of a reference twin-engine light aircraft modeled after the Eurocopter Bo 105 helicopter, operating on representative mission scenarios.

Extensive comparisons with flight test data are carried out and presented in terms of main rotor trim control angles and power requirements, along with general flight performance charts including payload-range diagrams. Predictions of total mission fuel consumption and NOx emissions are compared with estimated values provided by the Swiss Federal Office of Civil Aviation. Good agreement is exhibited between predictions made with the physics-based stirred reactor model and experimentally measured values of NOx emission indices. The obtained results suggest that, the production rates of NOx pollutant emissions are predominantly influenced by the behavior of total air inlet pressure upstream of the combustion chamber, which is affected by the employed operational procedures and the time-dependent all-up mass of the aircraft. It is demonstrated that, accurate estimation of on-board fuel supplies ahead of flight is key to improving fuel economy as well as reducing environmental impact. The proposed methodology essentially constitutes an enabling technology for the comprehensive assessment of existing and conceptual rotorcraft–powerplant systems, in terms of operational performance and environmental impact.
Methods for the Gas Dynamic Calculation of the Cooled Multistage Turbine Performance
Authors: Mamaev B. I. , Petukhovsky M. M. , Pozdnyakov A. V. , Ryabov E. K.
Published: September 2014

Method of 1D calculation was developed. It is applicable to various ideal gases and their mixtures with regard to variability of their physical properties within wide temperature range.

Four checking cross-sections were set for each vane/blade row: at the row inlet, in the row throat, at the row outlet, and downstream the row at the distance of the inter-row gap.

Relations for the calculation of the flow outlet angle and maximum outlet velocity when the velocity in the throat reaches sonic values were a basis for a mathematical model. These relations considered the row geometry, tapering of a meridional streamline, a compressibility of gas, and losses variable along a channel. They made it possible to determine a gas mass flow at various flow outlet velocities.

The row loss coefficient was determined from numerous test results. Losses in uncooled row were composed of a friction, edge, wave (due to incidence), and tip losses. A cascade density, the row height, the edge thickness, the airfoil surface roughness, inlet and outlet angles, Re, and the flow turbulence were also considered.

Semi-empirical relations, describing an impact of a cooling air blow-off through a perforation in the airfoil and tip shrouds, trailing edge slot, at the shroud mating area, and in the gap downstream the row, were applied for the cooled turbine calculation. The influence of the blade cooling air pre-swirl on its temperature and turbine power was taken into account as well.

Axial flows and the impact of a circumferential flow were defined when the radial gap flow for shroudless blades was calculated. For shrouded blades flows through linear and step labyrinths calculated. Influence of the rotation direction on the flow and gas heating in the labyrinth were also taken into account.

Disk-gas losses are also calculated.

Inputs were geometry of each row, a rotation velocity, a pressure, a temperature, a flow inlet angle, cooling air mass flow, temperature and pressure. Outputs could be any operation parameter of a turbine or a stage and flow parameters at checking cross-sections. Calculation covered whole range of turbine operation modes, including stage operation modes with energy consumption.

A high-performance code was written on a basis of this method. It was verified against test results of some model turbines. A comparison showed quite good correspondence to tests both for turbine integral parameters and flow parameters at the checking cross-sections.
Wind-Hydro-Gas Turbine Unit Commitment to Guarantee Firm Dispatchable Power
Authors: Branchini L. , Bianchi M. , Cavina N. , Cerofolini A. , De Pascale A. , Melino F.
Published: September 2014

The randomness and intermittence of wind power require additional reserves provided by thermal generators. This creates difficult scheduling of generation, causing thermal generators to start up or shut down frequently, or to operate at low efficiency and high fuel consumption state. If not, some wind power will be curtailed and wasted. This paper examines the operation of a hybrid system made up of a wind farm, a pump storage hydro and conventional thermal generation units consisting in a combination of a heavy-duty and an aeroderivative gas turbines.

In order to seek an optimal approach to deal with the uncertainty of increasing wind power and ensure both the efficient operation of thermal generators and full use of wind energy, two different control strategies have been proposed and compared: (i) a “custom” in house developed strategy and (ii) an “optimal” strategy based on Dynamic Programming.

Using actual generation data of a wind farm, the operation of hydro power plant and gas turbines are obtained with the aim of compensating differences between actual wind generation and load demanded. Natural gas fuel consumption and average gas turbine efficiencies during the analyzed time period are calculated along with number of units starts-up.
Applying an Extended Non Linear Harmonic Method to a CROR Configuration With Emphasis on the Acoustic Signature
Authors: Hildebrandt Thomas , Thiel Peter , Albert Sven , Vilmin Stephan
Published: September 2014

Contra Rotating Open Rotor (CROR) propulsion concepts offer the possibility of gaining a significant step in the reduction of the specific fuel consumption (SFC) of aeroengines. Next to their advantages in this area, CROR configurations pose serious challenges to aircraft designers in terms of their inherently high and unsteady pressure fluctuations, which are not shielded by any sort of casing. When compared to ducted fans, these pressure fluctuations can lead to an unacceptably high acoustic signature on the environment as well as to a high frequency stress load on the airplane structure. It is therefore necessary to capture and understand these unsteady flow effects early in the design phase, which in turn makes unsteady CFD calculations mandatory.

The paper presents the application of a highly efficient frequency based unsteady CFD method, the so called Non Linear Harmonic (NLH) method on a tractor (puller) CROR configuration. The Non Linear Harmonic Method returns unsteady results within at least two orders of magnitude less CPU time compared to the conventional approach of traditional unsteady sliding grid methods.

The NLH method has first been introduced by [1] and significantly extended by [2–4] in order to take more of the interacting blade frequencies into account. The NLH method used herein does not require any scaling of the geometry or changes in the blade count. In order to apply the method on CROR configurations, it has been further developed [5] and is fully capable to account for the different rotational speeds of all components of a CROR configuration. The novel rank-2 extension enables the unsteady effects of the first rotor to pass through the rotating flow field of the second rotor.
Characterization and Modeling of a Spinning Thermoacoustic Instability in an Annular Combustor Equipped With Multiple Matrix Injectors
Authors: Bourgouin Jean-François , Durox Daniel , Moeck Jonas P. , Schuller Thierry , Candel Sébastien
Published: September 2014

Oscillations in fully annular systems coupled by azimuthal modes are often observed in gas turbine combustors but not well documented. One objective of the present study is to characterize this type of oscillation in a laboratory scale system allowing detailed pressure measurements and high speed visualization of the flame motion. The experiment is designed to allow detailed investigations of this process at a stable limit cycle and for an extended period of time. Experiments reported in the present article are carried out in the MICCA facility which was used in our previous work to analyze instabilities arising when the chamber backplane was equipped with multiple swirling injectors (Bourgouin et al. ASME Paper GT2013-95010). In the present study, these units are replaced by a set of matrix injectors. The annular plenum feeds sixteen such devices confined by two cylindrical quartz tubes open to the atmosphere. The multiple flames formed by the matrix injectors are laminar and have a well documented describing function. This constitutes an ideal configuration allowing systematic investigations of thermo-acoustic oscillations coupled by longitudinal or azimuthal modes while avoiding complexities inherent to swirling turbulent flames studied previously. Optical access to the chamber allows high speed imaging of light emission from the flames providing instantaneous flame patterns and indications on the heat release rate fluctuations. Eight waveguide microphones record the pressure signal at the combustor injection plane and in the plenum. Among the unstable modes observed in this setup, this analysis focuses on situations where the system features a spinning azimuthal mode. This mode is observed at a frequency which is close to that associated with the 1A mode of the plenum. A theoretical analysis is then carried out to interpret the angular shift between the nodal lines in the plenum and chamber and the measured flame describing function is used to quantify this shift and determine the linear growth rate.
The Influence From the Working Medium on the Profile Loss in Compressor and Turbine Airfoils
Authors: Dahlquist Adrian , Thern Marcus , Genrup Magnus
Published: September 2014

A number of CCS-technologies are currently being developed for the reduction of CO2 emissions from thermal power stations. One such technology is the oxyfuel process, in which a mixture of CO2 and steam is used as the working medium. The semi-closed oxyfuel combustion combined cycle (SCOC-CC) is an oxyfuel cycle where the working medium mainly consists of CO2 (85–95%).

Current practice is to design turbomachinery using 1D and 2D flow tools, which primarily rely on loss models derived from experiments with air. For the oxyfuel case, the losses are hence extrapolated from air to a CO2/ steam mixture, which can have adverse effects on the accuracy of the loss model.

Therefore, the applicability and accuracy in using profile loss correlations derived with air when changing the working medium to the oxyfuel like environment of pure CO2 was investigated. The reason that 100% CO2 was chosen as the working medium and not a CO2/ H2O mixture is that the water content present is relatively low and varies from case-to-case. Hence, a general water content could not be specified that was relevant for all cases. The study was done with typical compressor and turbine airfoils using a steady-state Navier-Stokes’ 3D flow solver. This solver type can resolve the boundary layer (y+ of about unity) rather than relying upon a boundary layer equation, — hence eliminating the latter as a source of error.

The hypothesis was that the profile loss depended on the viscosity, and that amendments to the viscosity would affect the profile loss. This trend was observed, e.g. when changing the working medium from air to CO2, the profile loss coefficient (Yp) for the compressor was reduced with 25% and for the turbine with 6%, respectively.

A slight difference in profile loss for an individual cascade was found when changing the working medium from air to CO2. Theoretically, this difference leads to an increased mismatch of the stages downstream even at design point, and thus increases the losses and reduces the stability. However, the difference in profile loss is relatively small at the design point, and thus it is the authors’ opinion that the practical effect will be quite small. Therefore, it is considered safe to use loss correlations derived from air for design point calculations even when the working medium is CO2. However, there is a certain risk involved that air-based loss models are not capable of predicting the behavior over the full operating range, as the boundary layers risk to behave in a different manner.

Another aspect that was considered is how the wet surface area (physical size) of a turbomachine performing the same work (m·Δh0) will change between the two gases. This is important as the total profile loss in a whole compressor or turbine is directly proportional to this change. The conclusion was that the total wet area would increase by some 20% for CO2 compared to air.
Ejector Tip Injection for Active Compressor Stabilization
Authors: Stößel Marcel , Bindl Stefan , Niehuis Reinhard
Published: September 2014

In propulsion industry there is an ongoing need to significantly reduce SFC of jet engines resulting in cost reduction and lower emissions. Since the design of most of the engine components is at the limit of today’s technology level further gain of improvement on short term is to be achieved by implementation of new system concepts. Especially the stall safety margin in compression system design holds high potential for the optimization of the overall engine system. Once a reliable and effective stall control system becomes available an extension of present operating range is likely to be achieved by moving the steady operating line towards the stability limit and to intervene only in critical situations. At the Institute of Jet Propulsion at the University of the Federal Armed Forces in Munich, Germany a Larzac 04 twin-spool turbofan engine has already been equipped and tested with an adequate active stabilization system of the low pressure compressor for research purposes.

Those investigations revealed a strong dependency of the achievable stabilization effect and the amount and momentum of the injected air mass flow. For flying applications this mass flow has to be delivered by carried on means. Therefore it always penalizes the propulsion efficiency. In the given configuration, redirected air from the last stage of the high pressure compressor is used for injection. Usage of this bleed air directly influences the propulsion efficiency of the engine. In order to optimize the mass flow needed for stabilization, the existing injection system was redesigned to utilize ejector pumps. With this configuration a comparable stabilizing effect could be realized with less redirected air mass flow. In fact the open ejector pump configuration showed an even higher performance at maximum injection rate than the closed injection before. Therefore further investigations with this system focused on the effect of additional flow ports to the engine intake as they are necessary for an ejector pump and their basic influence on the operation stability of the low pressure compressor (LPC). In combination with the already existing stall detection algorithm of the institute a very promising system for increasing the available operating range in turbo compressors could be achieved.
A Comprehensive Investigation of Pre-Swirled Flow Through Rotating Radial Holes
Authors: Riedmüller Daniel , Sousek Jan , Pfitzner Michael
Published: September 2014

This paper reports on the flow (centrifugal = radially outwards, centripetal = radially inwards) through rotating radial orifices with and without pre-swirl in the flow approaching the orifice in the outer annulus. The aerodynamical behavior of flow through radial rotating holes is different from the one through axial and stationary holes due to the presence of centrifugal and Coriolis forces. To investigate the flow phenomena and the discharge coefficient of these orifices in detail, an existing test rig containing two independently rotating shafts (co- and counter rotating) was used. To simulate conditions of real gas turbines, where the flow is often influenced by upstream components, various pre-swirl angles were used in the test rig. Measurements of the flow discharge coefficient in both flow directions through the orifices (centripetal and centrifugal), with and without pre-swirl generation in the outer annulus, are presented at various flow conditions (pressure ratios across orifices, Mach numbers of approaching flow) and for different geometric parameters (length to diameter ratios, sharp/rounded inlet edges). Flow effects, that occur with pre-swirled flow are clarified. A comparison of the experimental data, for both flow directions, shows a similar behavior of the discharge coefficients with increasing shaft speeds. To supplement the experimental data and to better understand the experimental findings, numerical simulations were performed, which show a good agreement with the experimental results. Furthermore, an optimization model with complete automatic grid generation, CFD simulation and post-processing, was built to enable large parametric studies e.g. grid independence of the solutions.
Modeling and Experimental Investigation of an Oil-Free Micro Compressor-Turbine Unit for an ORC Driven Heat Pump
Authors: Demierre Jonathan , Rubino Antonio , Schiffmann Jürg
Published: September 2014

Domestic heating and cooling will more and more have to rely on heat pumps in order to support a more rational use of primary energy consumption. The heat pump market is mainly dominated by electrically driven vapour compression cycles and by thermally driven sorption processes. The drawback of electrically driven vapour compression cycle is their dependence on an electrical grid and the fact that they increase the winter or summer electricity peak demands. Hence, a thermally driven vapour compression cycle would offer substantial advantages and flexibility to the end user for heating and cooling applications.

This paper presents the investigation of an oil-free Compressor-Turbine Unit (CTU) used for a Thermally Driven Heat Pump (TDHP) based on the combination of a heat pump compression cycle and an Organic Rankine Cycle (ORC). The CTU consists of a radial inflow turbine and a centrifugal compressor of the order of 2 kW each, directly coupled through a shaft supported on gas lubricated bearings. The CTU has been tested at rotor speeds in excess of 200 krpm, reaching compressor and turbine pressure ratios up to 2.8 and 4.4 respectively and isentropic efficiencies around 70%. Comparisons between the experimental data and predictions of models, that are briefly described here, have been carried out. A sensitivity analysis based on the experimentally validated models shows that tip clearance, for both compressor and turbine, and surface roughness of the compressor are key parameters for further improving performance.
Experimental Validation of a Non-Linear Buckling Method on a Rear Engine Mount Support Structure
Authors: Peral Moreno Alonso , Marquina Zárraga Francisco Javier , Prieto Santos Francisco José , Gómez Sánchez Francisco Javier
Published: September 2014

Traditionally buckling analyses in engine structures have been performed using analytical solutions from validated bibliographical reference (e.g. Bruhn). This method requires a certain margin of safety due to the idealization of the real complex geometries into the more simple validated set of cases.

As computational power increased, linear Euler buckling based on finite element solutions has become accessible. This second approach also requires of a certain margin of safety due to not considering material and geometrical non-linear effects.

This paper presents the development of an accurate non-linear finite element prediction of the buckling characteristics of a rear engine mount support structure. The method includes both material and geometrical non-linearity.

This analytical prediction method has been validated by a series of material coupon and sub-component compressive experimental rig tests.

The work presented in this paper will be completed in the future with validation from a full component test and with a method to account for manufacturing tolerances.
Thermoeconomic Optimization of CSP Hybrid Power Plants With Thermal Storage
Authors: Barberis Stefano , Rivarolo Massimo , Traverso Alberto
Published: September 2014

This paper investigates the integration of Concentrating Solar Power technology in Combined Cycles for power production. Starting from a state of the art of CSP plants, the paper investigates alternative plant configurations, assessed and compared with a through-life thermoeconomic analysis. Plant layouts include thermal storage to manage the load demand of the plant throughout the day, considering both variable solar input and variable power demand. Focus is on the impact of thermal storage devices on optimal layouts.

The hybrid combined CSP plants are analyzed using original software tools, WTEMP for the design point analysis and WECoMP for the time-dependent thermoeconomic optimization, to take into proper account the time-dependent nature of both the electrical load demand and the hour-by-hour irradiation during the year.

The analysis shows that combining CSP technology with existing combined cycles a significant reduction of fuel consumption and greenhouse gas emissions is obtained, with an optimal solar share factor of about 20%, providing the grid with fully dispatchable power generation.
Density Ratio Effects on the Flow Field Emanating From Cylindrical Effusion and Trenched Film Cooling Holes
Authors: Schreivogel Peter , Kröss Bernhard , Pfitzner Michael
Published: September 2014

The present paper investigates density ratio effects on the flow field of cylindrical hole effusion and trench film cooling. An extensive parametric study of varying blowing rates (M = 1; 2; 4; 6), momentum (I = 1; 2; 8; 16) and velocity ratios (VR = 0.5; 1; 2) was carried out at three different density ratios (DR = 1.33; 1.6; 2). All cases were simulated using the realizable k-ε turbulence model with enhanced wall treatment. The mainstream boundary conditions were kept constant, while the coolant mass flow and temperature were varied. Additional 2D PIV measurements in streamwise planes and planes parallel to the wall were carried out in a heated, closed loop wind tunnel with an injection of cryogenically cooled air.

For constant momentum ratios, the jet core trajectories for both configurations were almost independent from the density ratio. In case of a constant blowing ratio, the jet penetration decreased with the density ratio, while it increased for a constant velocity ratio. Downstream of the trench a large recirculation zone is visible. Furthermore, cooling air is forced out of the trench in the midplane between two cooling holes.
Large-Eddy Simulation and Conjugate Heat Transfer in a Round Impinging Jet
Authors: Shum-Kivan Francis , Duchaine Florent , Gicquel Laurent
Published: September 2014

This study addresses and evaluates the use of high fidelity Large Eddy Simulation (LES) for the prediction of Conjugate Heat Transfer (CHT) of an impinging jet at a Reynolds number of 23 000, a Mach number of 0.1 and for a nozzle to plate distance of H/D = 2. For such simulations mesh point localization as well as the turbulent model and the numerical scheme are known to be of primary importance. In this context, a compressible unstructured third order in time and space LES solver is assessed through the use of WALE sub-grid scale model in a wall-resolved methodology. All simulations discussed in this document well recover main unsteady flow features (the jet core development, the impinging region, the deviation of the flow and the wall jet region) as well as the mean statistics of velocity. Convergence of the wall mesh resolution is investigated by use of 3 meshes and predictions are assessed in terms of wall friction and heat flux. The meshes are based either on full tetrahedral cells or on a hybrid strategy with prism layers at the wall and tetrahedral elsewhere. The hybrid strategy allows reaching good discretization of the boundary layers with a reasonable number of cells. Unsteady flow features retrieved in the jet core, shear layer, impinging region and wall jet region are analyzed and linked to the unsteady and mean heat flux measured at the wall. To finish, a LES based CHT computation relying on the finer grid is used to access the plate temperature distribution. Nusselt number profiles along the plate for the isothermal and the coupled cases are also provided and compared.
Analysis and Verification Test of Damping Characteristics of Steam Turbine Hollow Vane With Friction Damper
Authors: Kaneko Yasutomo , Yamashita Hiroyuki , Ooyama Hiroharu
Published: September 2014

A vane used in a low pressure end of a steam turbine is usually fixed to a shroud and a casing by welding both ends. In such a vane structure, the damping in loading operation is comprised of the material damping and the aerodynamic damping, because the structural damping is very small. In the blade and vane of high-capacity steam turbine units, the aerodynamic damping may become negative under the high loading operation, and some papers reported the self-excited vibration of the blade and vane caused by the negative aerodynamic damping. Recently, in order to increase the reliability of the steam turbine vane, a hollow vane with a friction damper has been proposed. In such a steam turbine vane, the curved damper piece made of the thin plate is inserted into the hollow vane, and the structural damping is added by use of the friction between the damper piece and the vane. In this paper, for the purpose of clarifying the damping characteristics of the hollow vane with the friction damper, first, the excitation test of the model vane is carried out. In the excitation test of the model vane, the damping characteristics of the model vane consisting of two flat plates and the thin curved damper piece are measured, changing the excitation force. Second, the analysis method for predicting the damping characteristics of the hollow vane with the friction damper, which utilizes the conventional modal analysis method and the harmonic balance method, is proposed. The validity of the analysis method is verified by comparing the measured damping with the calculated ones. After verifying the analysis method, the actual steam turbine hollow vane with the friction damper is also analyzed, and the effect of the damper stiffness on the damping characteristics is examined. Finally, the actual hollow vane with the friction damper for the high-capacity steam turbine unit is designed and manufactured, and the excitation test of the actual hollow vane is carried out. From these results, the damping characteristics of the hollow vane with the friction damper are clarified.
Development Approach to the Dry Low Emission Combustion System of MAN Diesel and Turbo Gas Turbines
Authors: Huitenga Holger , Norster Eric R.
Published: September 2014

The THM series of industrial gas turbines covers a power range of 6 to 12.5 MW and has been improved and uprated over many years. The majority of turbines installed are still in commercial operation and they are mainly used for compressor drives but also find generator applications.

In recent years the constraints of emission legislations for new and existing gas turbines has made a development programme for a dry low emission (DLE) combustion system essential. The combustion system apart from meeting latest emission targets of 75 mg/mN3 NOx and 100 mg/mN3 CO must be suitable for both, new and retrofit engine options and therefore compact for standard enclosure installation. In addition the design should be simple and robust with the same accessibility as the existing standard combustion system.

The paper describes the design and development steps to provide a prototype lean premixed DLE combustion system. The basic approach for a simple lean premixed design together with aero-thermodynamic sizing for pressure loss, flow proportions, stability and cooling is described. The initial efforts were directed to a system for the 11 MW THM 1304-11AP machine, with combustor atmospheric testing to verify design parameters and operating limits.

The development was continued by subsequent high pressure testing of the prototype, starting with suitable units in the MAN engine test facility, omitting any high pressure rig tests. Field tests were carried out on a compressor drive application on a gas pumping station to prove long term durability. Adaptations of the design are now engine-tested for other THM models, even recuperated ones. Also, the combustor technology and methods developed here provide the basis for the combustors on the new MAN MGT 6100 and 6200 engines [1].
Losses of Steam Admission in Industrial Steam Turbines Depending on Geometrical Parameters
Authors: Engelmann David , Schramm Andreas , Polklas Thomas , Mailach Ronald
Published: September 2014

Due to the range of applications, industrial steam turbines show a compact and modular design including several branches for the admission and/or extraction of process steam. In conjunction with a flexible operation and partial load conditions, it is important to estimate the losses appearing at those branches sufficiently.

Therefore, the results of an extended parameterized numerical study of a T-junction with steam admission are discussed in the first part of the current paper. This study, carried out with a 3D RANS CFD-solver, is used to determine the additional secondary loss, which is caused by deflection of the admitted steam and mixing with the main flow. At this, the loss distribution depends on geometrical parameters of the T-junction such as the area ratio of branch to main pipe diameter and the curvature of the transition piece. The secondary loss, calculated as a function of total pressure loss and local wall shear, is compared with measurement data from literature.

In the second part of the paper the loss calculation procedure is adapted from theoretical computations to two actual industrial steam turbine configurations. First, a 3-stage segment of a high speed turbine which includes a circumferential slot for steam admission is examined. Therefore, flow ratios from 0 to 50 % of admitted steam, compared to main flow, are numerical performed. Second, a 2.5-stage low speed turbine segment with two asymmetrical branches and a fix flow ratio of 40% for the first branch, respectively 80% for the second branch is considered. All invested configurations illustrate how geometrical parameters affect the secondary loss distribution as well as the mixing process within subsequent turbine stages.
Thermoeconomic Evaluation of Solar Thermal and Photovoltaic Hybridization Options for Combined-Cycle Power Plants
Authors: Spelling James , Laumert Björn
Published: September 2014

The hybridization of combined-cycle power plants with solar energy is an attractive means of reducing carbon dioxide emissions from gas-based power generation. However, the construction of the first generation of commercial hybrid power plants will present the designer with a large number of choices. To assist decision making, a thermoeconomic study has been performed for three different hybrid power plant configurations, including both solar thermal and photovoltaic hybridization options. Solar photovoltaic combined-cycle power plants were shown to be able to integrate up to 63 % solar energy on an annual basis, whereas hybrid gas-turbine combined-cycle systems provide the lowest cost of solar electricity, with costs only 2.1 % higher than a reference, unmodified combined-cycle power plant. The integrated solar combined-cycle configuration has been shown to be economically unattractive.
Experimental Study of Compressor Instability Inception in a Transonic Axial Flow Compressor
Authors: Li Qiushi , Pan Tianyu , Li Zhiping , Sun Tailu , Gong Yifang
Published: September 2014

An experimental investigation is conducted to study the details of instability inception in a transonic axial flow compressor. The experimental results indicate that the compressor instability is initiated through the development of a low-frequency axisymmetric disturbance. The frequency of this disturbance is approximately the Helmholtz frequency of the test facility. The low-frequency disturbance can be detected over 3000 rotor revolutions before the compressor becomes unstable. Further experimental investigations illustrate that this low-frequency axisymmetric disturbance is initiated at the hub region of the compressor. This new kind of instability inception is termed “partial surge.” Examination of the design parameters of the compressor indicates that a high diffusion factor in the rotor root region might be the cause of the partial surge type instability inception.
Mathematical Model of Two-Stage Turbocharging Gasoline Engine Propeller Propulsion System and Analysis of Its Flying Characteristic
Authors: Shan Peng , Zhou Yicheng , Zhu Dexuan
Published: September 2014

A flying characteristic simulation method is studied for two-stage turbocharging Compression Ignition engine propeller propulsion system, intended for medium/high altitude low-speed long-endurance multi-role UAV systems at 10 ∼ 20 kilometers high, with cruising speed 100 ∼ 250 km/h. Introducing the simulation method for gas turbine engine with component models, based upon component maps or algebraic equations, this method solves joint-working equations of the propulsion system by Newton iteration method to obtain cooperation points of the system. A full-power holding requirement and turbocharger-engine collaboration condition are stated. The regulating rules in both full-power holding mode and power lapse mode are analyzed. The influences of regulating rules on turbocharger operating lines are placed. Finally, the altitude-velocity characteristics of the propulsion system and components are investigated. The research shows three results. This method converges rapidly that usually it needs only 5–6 iterations to obtain one operating point. The regulation scheme of two gas-bypass valves can not only meet the design objectives, but also allow an effective adjusting to the operating points of the turbochargers. This method can be extended conveniently to the simulations of more complex multi-stage turbocharging systems.
A Simplified Method for Predicting the Average Vibratory Response of Mistuned Clustered Stator Vanes
Authors: Philippe Jonathan , Thouverez Fabrice , Blanc Laurent , Gruin Marion
Published: September 2014

The role of stator vanes is to straighten the air flow on each stage of axial compressors. They are so subject to dynamically fluctuating high pressure loads. Furthermore, monobloc clustered designs have been developed to facilitate the manufacturing process and reduce costs, but they result in the loss of cyclic symmetry properties and very low structural damping. This makes it more difficult to predict vibratory behavior, when taking high modal density and extreme sensitivity to mistuning into account, end even more essential to ensure structural strength in the context of fatigue. In most cases, mistuning due to geometrical and material tolerances is unknown. Here, an analytical method has been developed to predict the average vibratory response of a clustered stator vane in which the Young modulus of certain blades is associated with a random variable mimicking the mistuning effect. This method is based on a linear approximation of the evolution of eigenfrequencies as a function of a random variables, as eigenvectors are almost constant, and a dynamic flexibility matrix reconstruction strategy. This method was tested on a simplified stator vane model based on a 2D Euler-Bernoulli beam lattice. The results are quite accurate when pressure is uniformly distributed on the “blades” and when the ferrule to blade stiffness ratio is high. This approach provides a simple model that can be used in the first stages of design as it allows fast simulation with a large number of random variables and with good approximation of the average vibratory response.
Optimization of the Hole Exit Shaping of Film Holes Without and With Compound Angles for Maximal Film Cooling Effectiveness
Authors: Chi Zhongran , Li Xueying , Han Chang , Ren Jing , Jiang Hongde
Published: September 2014

Shaped film holes can achieve higher film cooling effectiveness compared with the simple cylindrical film holes. According to former studies, the geometry of the shaped film holes has significant influence on the cooling performance. In order to maximize the film cooling effectiveness of the shaped holes, a two-level design optimization methodology of the hole exit shaping is developed in the present study.

The optimization methodology consists of a parametric design and CFD mesh generation tool called Coolmesh, a RANS CFD solver, a database of film cooling effectiveness distributions, a metamodel, and a genetic algorithm (GA) for evolutionary optimization. A binary parametric representation of the 2D hole exit shaping is initiated based on the B-spline methods. The metamodel can efficiently predict the detailed distribution of film cooling effectiveness using the CFD results in the database, which is continuously updated for higher accuracy. In each first-level iteration, a second-level GA optimization search is carried out coupled with the metamodel, and then the optimal geometry is evaluated using CFD methods and added to the database. An anisotropic turbulence model is applied to the CFD solver for higher accuracy according to a detailed experimental validation using PSP measurements.

In the present study, three design optimizations of the shaped holes without and with compound angles are carried out on a flat plate. The optimization methodology can efficiently find the optimal geometries of shaped holes using only hundreds of CFD runs. For the shaped holes with compound angle, the optimized geometry can generate a back flow vortex which interacts with the shear vortex and weakens the mixing of coolant and hot gas, resulting in a higher film cooling effectiveness on the plate.
Heat Transfer in Reacting Cooling Films: Part I — Influence and Validation of Combustion Modelling in CFD Simulations
Authors: Pohl Stephanie , Frank Gabriele , Pfitzner Michael
Published: September 2014

The demand for increased performance and lower weight of gas turbines gives rise to higher fuel-to-air ratios and a more compact design of the combustion chamber, thereby increasing the potential of fuel escaping unburnt from the combustor. Chemical reactions are likely to occur when the coolant air, used to protect the turbine blades, interacts with the unreacted fuel.

Within this work, RANS simulations of reacting cooling films exposed to high temperature fuel-rich exhaust gases are performed using the commercial CFD code ANSYS Fluent and validated against experimental results obtained at the Air Force Research Laboratory in Ohio. The results underline that the choice of the turbulence model has a significant impact on the evolution of the flow field and the mixing effectiveness. The flamelet as well as the equilibrium combustion model are able to predict an adequate distance of the reaction zone normal to the wall. Its thickness, however, is still much smaller and its onset too far upstream as compared to the experimental results. According to the present analysis the k-ω SST turbulence model applied along with the flamelet combustion model turned out to be an appropriate choice in order to model near wall reacting flows with reasonable prospect of success.
Experimental and Numerical Studies of Sulfate and Organic Condensation on Aircraft Engine Soot
Authors: Peck Jay , Yu Zhenhong , Wong Hsi-Wu , Miake-Lye Richard , Liscinsky David , Jennings Archer , True Bruce
Published: September 2014

To study the condensation of sulfates and organics on aircraft engine soot, a systematic measurement of particulate matter was performed using a sector rig combustor at various operation conditions and sampling configurations. The condensation of organics increased with increasing soot loading, although the initial vapor phase concentration was lower for the high soot condition. The condensation rate of the organic species is much slower than that of the sulfates, and therefore the availability of the soot surfaces becomes a rate-limiting factor. On the other hand, because the sulfates are nearly completely condensed on soot surfaces even for the low soot conditions, more soot did not significantly increase the condensation of sulfates. The experimental results were explained with a microphysical simulation by using a 6-species surrogate model to represent volatile aircraft emissions. Using the relative composition of the volatile organics based on saturation vapor concentration, and the dry mass accommodation coefficient derived from the correlation to water solubility, the proposed surrogate model was able to match the experimental measurements both qualitatively and quantitatively.
Influence of the Arrangement of Dilution Holes for Dilution Mixing in a Three-Injector Reverse Flow Combustor
Authors: Dai Wei , Zhang Yan , Lin Yuzhen , Yang Qian , Zhang Chi
Published: September 2014

The exit temperature profile has a great effect on the reliability and security in a gas turbine. In this paper, the exit temperature profile of a small engine reverse-flow combustor with three injectors test module was experimentally obtained to qualitatively analyze the influence of the dilution hole distribution. The test model was a three-injector rectangular reverse-flow combustor with swirling flow atomizing. A 1D moving thermocouple rake was used to measure the global exit temperature profile of the combustor. The pressure was at ambient pressure with the inlet temperature was 290K. The FAR was in the range of 0.03. The dilution holes were in opposed and staggered arrangements. The experimental results showed that the exit temperature profile was obviously influenced by the dilution holes. Compared with the opposed dilution jets, the staggered dilution jets provided more uniform circumferential exit temperature profile, but a little higher pattern factor of 0.1725. The numerical results showed that the staggered dilution jets generated a larger scale counter-rotating vortex pairs. The inner and outer jets not only did not interact with each other (especially at the outer ring of combustor), but also filled the intermediate regions of dilution jets, resulting in a higher gas mixing rate. Consequently, the staggered dilution jets provided a better mixing performance for the outer ring of combustor.