bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
CCPP Performance Augmentation Using LNG Re-Gasification Cold Energy
Authors: Acharya Mihir , Pattanayak Lalatendu , Gajjar Hemant , Elbracht Frank , Asthana Sandeep 
Published: September 2014

With gas becoming a fuel of choice for clean energy, Liquefied Natural Gas (LNG) is being transported and re-gasification terminals are being set up at several locations. Re-gasification of LNG leads to availability of considerable cold-energy which can be utilized to gain power and efficiency in a Gas Turbine (GT) based Power Plant. With a number of LNG Re-gasification Terminals coming up in India & around the globe, setting up of a high efficiency CCPP adjacent to the terminal considering utilization of the cold energy to augment its performance, and also save energy towards re-gasification of LNG, provides a feasible business opportunity.
Thermodynamic analysis and major applications of the LNG re-gasification cold energy in Gas Turbine based power generation cycle, are discussed in this paper. The feasibility of cooling GT inlet air by virtue of the cold energy of Liquefied LNG to increase power output of a Combined Cycle Power Plant (CCPP) for different ambient conditions is analyzed and also the effect on efficiency is discussed. The use of cold energy in condenser cooling water circulating system to improve efficiency of the CCPP is also analyzed. Air cooling capacity and power augmentation for a combined cycle power plant based on the advanced class industrial heavy duty gas turbine are demonstrated as a function of the ambient temperature and humidity. The economic feasibility of utilizing the cold energy is also deliberated.
Two-Phase Flow Modeling and Measurements in Low-Pressure Turbines: Part 2 — Turbine Wetness Measurement and Comparison to CFD-Predictions
Authors: Schatz M. , Eberle T. , Grübel M. , Starzmann J. , Vogt D. M. , Sürken N. 
Published: September 2014

The correct computation of steam subcooling, subsequent formation of nuclei and finally droplet growth is the basic prerequisite for a quantitative assessment of the wetness losses incurred in steam turbines due to thermal and inertial relaxation. The same basically applies for the prediction of droplet deposition and the resulting threat of erosion.
Despite the fact that there are many CFD-packages that can deal with real-gas effects in steam flows, the accurate and reliable prediction of subcooling, condensation and wet steam flow in steam turbines using CFD is still a demanding task.
One reason for this is the lack of validation data for turbines that can be used to assess the physical models applied. Experimental data from nozzle and cascade tests can be found in the open literature; however, this data is only partly useful for validation purposes for a number of reasons. With regard to steam turbine test data, there are some publications, yet always without any information about the turbine stage geometries.
This publication is part of a two-part paper; whereas part 1 focuses on the numerical validation of wet steam models by means of condensing nozzle and cascade flows, the focus in this part lies on the comparison of CFD results of the turbine flow to experimental data at various load conditions. In order to assess the validity and reliability of the experimental data, the method of measurement is presented in detail and discussed. The comparison of experimental and numerical results is used for a discussion about the challenges in both modeling and measuring steam turbine flows, presenting the current experience and knowledge at ITSM.