bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Modeling Study of the Combustion of Synthetic Jet Fuels: Naphtenic Cut and Blend With a GtL Jet Fuel
Authors: Dagaut Philippe , Diévart Pascal
Published: September 2016

Research on the production and combustion of synthetic jet fuels has recently gained importance because of their potential for addressing security of supply and sustainable air transportation challenges. The combustion of a 100% naphtenic cut that fits with typical chemical composition of products coming from biomass or coal liquefaction (C12.64H23.64; M=175.32 g.mol−1; H/C=1.87; DCN=39; density=863.1 g.L−1) and a 50% vol. mixture with Gas to Liquid from Shell (mixture: C11.54H23.35; M=161.83 g.mol−1; H/C=2.02; DCN=46; density=800.3 g.L−1) were studied in a jetstirred reactor under the same conditions (temperature, 550–1150 K; pressure, 10 bar; equivalence ratio, 0.5, 1, and 2; initial fuel concentration, 1000 ppm). Surrogate model-fuels were designed based on fuel composition and properties for simulating the kinetics of oxidation of these fuels. We used new model-fuels consisting of mixtures of n-decane, decalin, tetralin, 2-methylheptane, 3-methylheptane, n-propyl cyclohexane, and n-propylbenzene. The detailed chemical kinetic reaction mechanism proposed was validated using the entire experimental database obtained in the present work and for the oxidation of pure GtL, we used previous results. Kinetic computations involving reaction paths analyses and sensitivity analyses were used to interpret the results.
Effect of Exit Pressure Pulsation on the Performance and Stability Limit of a Turbocharger Centrifugal Compressor
Authors: Barrera-Medrano Maria Esperanza , Newton Peter , Martinez-Botas Ricardo , Rajoo Srithar , Tomita Isao , Ibaraki Seiichi
Published: September 2016

It is well known that compressor surge imposes a significant limit on the flow range of a turbocharged internal combustion engine. The centrifugal compressor is commonly placed upstream of the inlet manifold and hence, it is exposed to the intermittent flow regime of the inlet valves. Surge phenomena has been well studied over the past decades, there still remains limited information with regards to the unsteady impact caused by the inlet valves. This study presents an experimental evaluation of such a situation. Engine representative pulses are created by a downstream system comprising a large volume, two rotating valves, a throttle valve and the corresponding pipe network. Different pulsation levels are characterized by means of their frequency and the corresponding amplitude at the compressor inlet.

The stability limit of the system under study is evaluated with reference to the parameter B proposed by Greitzer [7–9]. B describes the dynamics of the compression system in terms of volume, area, equivalent length and compressor tip speed as well as the Helmholtz frequency of the system. For a given compressor, as B goes beyond a critical value, the system will exhibit surge as the result of the flow instability progression.

The reduced frequency analysis shows that the scroll-diffuser operates in an unsteady regime, while the impeller is nearly quasi-steady. In the vicinity of the surge point, under a pulsating flow, the instantaneous operation of the compressor showed significant excursions into the unstable side of the surge line. Furthermore, it has been found that the presence of a volume in the system has the greatest effect on the surge margin of the compressor under the unsteady conditions.
Development and Application of a Fast-Response Total Temperature Probe for Turbomachinery
Authors: Arenz Martin C. , Weigel Björn , Habermann Jan , Staudacher Stephan , Rose Martin G. , Lutum Ewald , Berns Wolfgang
Published: September 2016

The measurement of unsteady total temperature is of great interest for the examination of loss mechanisms in turbomachinery with respect to the improvement of the efficiency. Since conventional thermocouples are limited in frequency response, several fast-response total temperature probes have been developed over the past years. To improve the spatial resolution compared to these existing probes and maintaining a high temporal resolution, a new fast-response total temperature probe has been developed at the Institute of Aircraft Propulsion Systems (ILA) in cooperation with Berns Engineers. The design of the probe allows a sensitive measuring surface below one square millimeter. A detailed insight into the design of the probe, the measurement principle, the calibration process, and an estimation of the measurement uncertainty is given in the present paper. Furthermore, to prove the functionality of the probe, first experimental results of a simple test bed and of area traverses downstream of the first rotor of a two-stage low pressure turbine are presented. It is shown, that the new probe is capable of detecting rotor characteristic effects as well as rotor-stator-interactions. In addition, a hot-spot is investigated downstream of the first rotor of the turbine and the findings are compared to effects known from literature.
Coke Deposition Effect on the Flow Distribution Characteristics of Kerosene Under Supercritical Pressure
Authors: Huang H. R. , Deng H. W. , Xu G. Q. , Jia Z. X. , Fu Y. C.
Published: September 2016

Performed experiments have studied the effect of coke deposition on the characteristics of flow distribution of aviation kerosene RP-3 at supercritical pressure. The whole experiment is divided into two steps: 1) making a coke tube; 2) paralleling the coked tube and a regular one with the same scale and observing the flow distribution status in different system pressure and total mass flow rate. The experimental results indicated that the deposition of coke made a great difference on the flow distribution of fuel.

Based on experimental results, it’s demonstrated that the percentage of total mass flow rate in coke-free tube increases to 68.5%. Further analyses reveal the fact that the total mass flow rate has nearly no impact on flow distribution and the system pressure also influence the distribution very little. What’s more, the amount of coke vs axial position and total amount of coke in coked tube are mentioned in this paper, which is benefit in analysis of flow distribution.
Prediction of Confined Flame Flashback Limits Using Boundary Layer Separation Theory
Authors: Hoferichter Vera , Hirsch Christoph , Sattelmayer Thomas
Published: September 2016

Premixed combustion is a common technology applied in modern gas turbine combustors to minimize nitrogen oxide emissions. However, early mixing of fuel and oxidizer opens up the possibility of flame flashback into the premixing section upstream of the combustion chamber. Especially for highly reactive fuels boundary layer flashback is a serious challenge. For high preheating and burner surface temperatures, boundary layer flashback limits for burner stabilized flames converge to those of so-called confined flames, where the flame is stabilized inside the burner duct. Hence, the prediction of confined flashback limits is a highly technically relevant task.

In this study, a predictive model for flashback limits of confined flames is developed for premixed hydrogen-air mixtures. As shown in earlier studies, confined flashback is initiated by boundary layer separation upstream of the flame tip. Hence, the flashback limit can be predicted identifying the minimum pressure rise upstream of a confined flame causing boundary layer separation. For this purpose, the criterion of Stratford is chosen which was originally developed for boundary layer separation in mere aerodynamic phenomena. It is shown in this paper that it can also be applied to near wall combustion processes if the pressure rise upstream of the flame tip is modeled correctly. In order to determine the pressure rise, an expression for the turbulent burning velocity is derived including the effects of flame stretch and turbulence. A comparison of the predicted flashback limits and experimental data shows high prediction accuracy and wide applicability of the developed model.
Liquid Fuel Composition Effects on Forced, Non-Premixed Ignition
Authors: Sforzo Brandon , Dao Hoang , Wei Sheng , Seitzman Jerry
Published: September 2016

The effects of jet fuel composition on ignition probability have been studied in a flowfield that is relevant to turbine engine combustors, but also fundamental and conducive to modeling. In the experiments, a spark kernel is ejected from a wall and propagates transversely into a crossflow. The kernel first encounters an air-only stream before transiting into a second, flammable (premixed) stream. The two streams have matched velocities, as verified by hot-wire measurements. The liquid fuels span a range of physical and chemical kinetic properties. To focus on their chemical differences, the fuels are prevaporized in a carrier air flow before being injected into the experimental facility. Ignition probabilities at atmospheric pressure and elevated crossflow temperature were determined from optical measurements of a large number of spark events, and high speed imaging was used to characterize the kernel evolution. Eight fuel blends were tested experimentally; all exhibited increasing ignition probability as equivalence ratio increased, at least up to 1.5. Statistically significant differences between fuels were measured that have some correlation with fuel properties. To elucidate these trends, the forced ignition process was also studied with a reduced order numerical model of an entraining kernel. The simulations suggest ignition is successful if sufficient heat release occurs before entrainment of colder crossflow fluid quenches the exothermic oxidation reactions. As the kernel is initialized in air, it remains lean during the initial entrainment of the fuel-air mixture; thus richer crossflows lead to quicker and higher exothermicity.
Development of Temperature Estimation Method for a Gas Turbine Transition Piece
Authors: Okada Mitsutoshi , Takahashi Toshihiko , Yamada Susumu , Ozeki Takayuki , Fujii Tomoharu
Published: September 2016

Temperature estimation methods for a transition piece of a gas turbine are developed in terms of microstructural changes and computational fluid dynamics (CFD) for life assessment. Temperature is estimated to be low around the center of the component where thermal barrier coating (TBC) is deposited on the Ni-base superalloy and a combination of internal cooling and film cooling is also applied. Test specimens are prepared from the above area for a high-temperature heating test in air. The microstructure in the superalloy and TBC is investigated after the test. The thermally grown oxide (TGO) formed on the bondcoat surface increases with the square root of the test time, and on the basis of this relation, a temperature-estimation equation is obtained. The estimated temperature distribution is compared with a numerical heat transfer simulation by means of CFD. The geometry of the transition piece with internal cooling structure is acquired using an X-ray computerized radiography and a laser digitizer, and it is modeled for the numerical simulation. The heat conduction analysis is applied to the transition piece, and the convection and radiation heat transfer analyses are applied to the gas path and internal cooling flow. These analyses are conjugated to estimate the temperature distribution. The simulation result agrees well with the estimation using TGO thickness.
A Laboratory Based Course on Energy Systems in Mechanical Engineering Undergraduate Program
Authors: Deniz Sabri
Published: September 2016

A laboratory based undergraduate course focused on energy systems and energy efficiency was developed at the Lucerne University of Applied Sciences. The course is a practice-oriented introduction to fluid / energy systems, turbomachinery, and energy production. It is offered to the mechanical engineering as well as to the “Energy Systems” program students in the first semester. Main parts of the course are experiments and mini projects carried out in the fluid mechanics, thermodynamics, and turbomachinery laboratories. After an introduction of (1) the basic theory of the mass- and energy conservation equations as main governing laws for energy systems and (2) measurement techniques during the first two weeks, the students carry out experiments in small groups on different test rigs with the help of an instructor for about four weeks (each week a different test). The experiments and test rigs are selected considering different aspects of turbomachinery and energy systems. They cover hydraulic turbines, small wind turbines, a water pump, compressor, heat pump, combined heat and power system, fuel cell, solar energy, and combustion engine. Following a two weeks theory wrap up, the students start with mini projects again in small groups in the laboratory. The students are requested to do a new design or to carry out a design change or modification at an existing machine or test rig. They also need to test their new design or design modification. At the end the students have to do a presentation about the mini project results and write a short report.

The objectives of the course are first to introduce the laboratory environment to the students from the beginning of the curriculum. Further the experimental investigations on laboratory test rigs make the students familiar with the fundamentals, working principles, characteristics, operation, and application of turbomachinery and energy systems. They also learn the basics of energy conversion, conservation, and the importance of relevant performance parameters such as efficiency. The mini projects have direct practical relevance to real world problems and applications. From an educational viewpoint the students are introduced to team-work during the projects, project planning with execution, and they are learning by doing or by experiential learning. The students are actively involved in the mini projects and they can reflect their experience at the end of the course during the presentations. The implementation of the course is time consuming and costly but the feedback from the students is very positive although they are challenged by confronting real world energy systems and problems in the first semester.
Automated Design Space Exploration of Advanced-Shaped Film Cooling Holes Using the SHERPA Algorithm
Authors: Kusterer Karsten , Dickhoff Jens , Campana Noël T. , Sugimoto Takao , Tanaka Ryozo , Kazari Masahide , Bohn Dieter
Published: September 2016

In modern gas turbines, the film cooling technology is essential for the protection of hot parts. Today, shaped holes are widely used, but besides others, the NEKOMIMI-shaped cooling holes have shown that there is still potential to increase the film cooling effectiveness significantly by generation of Anti-Counter-Rotating Vortices (ACRV). As a result, the cooling air remains close to the wall and spreads in lateral direction along the surface. The ACRV result from the specialized shape of the expanding hole exits (NEKOMIMI-shape). Thus, the design parameters have a crucial impact to the film cooling effectiveness behind the hole.

In the present study the design parameters are varied and in order to explore the design space for a defined test case with respect to the maximum achievable averaged adiabatic film cooling effectiveness. This illustrates the capabilities of the technology. Additionally, the design space of a laidback fan-shaped film cooling configuration is explored and compared to the result obtained with the NEKOMIMI-shaped geometry. In order to show the robustness of the configurations with respect to compound angles of the cross flow, two advanced configurations — one NEKOMIMI and one shaped hole — are analysed with compound angles up to 16°.
Low Frequency Distortion in Civil Aero-Engine Intake
Authors: Carnevale Mauro , Wang Feng , di Mare Luca
Published: September 2016

The main role of the intake is to provide a sufficient mass flow to the engine face and sufficient flow homogeneity to the fan. Intake-fan interaction off design represents a critical issue in the design process because intake lines are set very early during the aircraft optimization.

The off-design operation of an aero-engine, strictly related to the intake flow field, can be mainly related to two different conditions. When the plane is in near ground position, vorticity can be ingested by the fan due to crosswind incidence. During the flight, distortions occur due to incidence. In these conditions, the windward lip is subjected to high acceleration followed by strong adverse pressure gradients, high streamline curvature and cohabitation of incompressible and transonic flow around the lip. All these features increase the risk of lip stall in flight at incidence or in crosswind near ground operation and increase the level of forcing seen by the fan blades because of the interaction with non-uniform flow from the intake.

This work deals with the study of two sources of distortions: ground vortex ingestion and flight at high incidence conditions. A test case representative of a current installation clearance from the ground has been investigated and the experimental data available in open literature validated the CFD approach. An intake, representative of a realistic civil aeroengine configuration flying at high incidence, has been investigated in powered and aspirated configurations. Distortion distributions have been characterized in terms of total loss distributions in space and in time. The beneficial effect of the presence of the fan in terms of distortion control has been demonstrated. The mutual effect between fan and incoming distortion from the intake has been assessed in terms of modal force and distortion control. CFD has been validated by means of comparisons between numerical results and experimental data have been provided. Waves predicted by CFD have been compared with an actuator disk approach prediction. The linear behavior of the lower disturbance frequency coming from distortion and the waves reflected by the fan has been demonstrated.
Numerical Analysis of Turbulent Jets in Quiescent Medium
Authors: Singh Ritik , Gyuro Marton L.
Published: September 2016

Jet fans produce a highly anisotropic turbulent flow regime and cause severe entrainment of the ambient fluid. Additionally, the placement of jet fans near or away from walls has a significant impact on throw and spread of the fan. This paper proposes a RSM based numerical technique to accurately predict the throw and spread of jet fans in an industrial setting while accounting for both the near wall effects and anisotropic nature of turbulence. The RSM based numerical technique described in this study allows for accurate prediction of the axial throw termination distances for jet fans in an industrial setting. The RSM approach also overcomes the limitations imposed by the free jet theory by accounting for wall effect on flow as well as other physical or temporal limitations imposed by various numerical methods such as RANS and SRS.

The Free Jet Theory proposes a classification method for turbulent jet decay problems, where the jet decay domain is classified into three flow domains and one terminal region. The terminal region of turbulent jet decay is not understood well physically and is neglected for the purpose of throw and spread calculations. The technique put forth in this paper draws from the fundamentals presented by the free jet theory and is then modified and applied to account for Coanda effects seen due to the proximity of walls to the flow when the jet fan is mounted close to the ceiling. Finally, experimental data is recorded by placing the jet fan in proximity with the floor in a closed room. The data thus generated is subsequently used to validate numerical results.
Numerical and Experimental Results From a Common-Source High-G Ultra-Compact Combustor
Authors: Cottle Andrew E. , Polanka Marc D.
Published: September 2016

Ultra-Compact combustion presents a novel solution to address the demand for increasingly compact, efficient, and low weight aircraft gas turbine engine propulsion systems. An Ultra-Compact Combustor (UCC) operates by diverting a portion of the compressor exit flow into a cavity about the engine outer diameter. Injection into the cavity can be done at an angle in order to induce bulk circumferential swirl. Swirl velocities in the cavity then impart a centrifugal load of approximately 1000g0. This high-g UCC concept has been investigated by The Air Force Institute of Technology with the goal of incorporating a common upstream flow source to distribute the simulated compressor exit flow into separate core and combustion cavity flow paths.

Experimental results from this test rig are presented, with particular emphasis on establishing the design flow split through the diffuser into the circumferential cavity. The implementation of a core channel plate was instrumental in control of the mass flow splits. Computational Fluid Dynamics (CFD) supplement the experiments and enable a more detailed understanding of the interactions within the diffuser and the interactions between the air injection jets and the fuel jets. A range of cavity equivalence ratios was studied and combustion within the cavity was shown to be a strong function of cavity loading, which was in turn a function of the total mass flow. Varying the orientation of the channel plate with respect to guide-vane leading edges caused a change in the core flow development which then had a secondary effect of aiding the combustion process within the cavity.
Evaluation of Performance Robustness of a Gas Turbine Cogeneration Plant Based on a Mixed-Integer Linear Model
Authors: Yokoyama Ryohei , Nakamura Ryo , Wakui Tetsuya , Shinano Yuji
Published: September 2016

In designing energy supply systems, designers are requested to rationally determine equipment types, capacities, and numbers in consideration of equipment operational strategies corresponding to seasonal and hourly variations in energy demands. However, energy demands have some uncertainty at the design stage, and the energy demands which become certain at the operation stage may differ from those estimated at the design stage. Therefore, designers should consider that energy demands have some uncertainty, evaluate the performance robustness against the uncertainty, and design the systems to heighten the robustness. Especially, this issue is important for cogeneration plants, because their performances depend significantly on both heat and power demands. Although robust optimal design methods of energy supply systems under uncertain energy demands were developed, all of them are based on linear models for energy supply systems. However, it is still a hard challenge to develop a robust optimal design method even based on a mixed-integer linear model. At the first step for this challenge, in this paper, a method of evaluating the performance robustness of energy supply systems under uncertain energy demands is proposed based on a mixed-integer linear model. This problem is formulated as a bilevel mixed-integer linear programming one, and a sequential solution method is applied to solve it approximately by discretizing uncertain energy demands within their intervals. In addition, a hierarchical optimization method in consideration of the hierarchical relationship between design and operation variables is applied to solve large scale problems efficiently. Through a case study on a gas turbine cogeneration plant for district energy supply, the validity and effectiveness of the proposed method and features of the performance robustness of the plant are clarified.
Exhaust Gas Recirculation to Improve Part Load Performance on Combined Cycle Power Plants
Authors: Jonshagen Klas
Published: September 2016

The common approach for part load operation of a combined cycle power plant is to maintain the turbine inlet temperature as high as possible without exceeding the temperature limits of the gas turbine exhaust. High part load firing temperature will give high cycle efficiency and low HC and CO emissions. The common approach is to reduce the flow by decreasing the compressor inlet flow-angle by turning the compressor variable guide vanes. This is done to control the turbine inlet temperature while the load is reduced by decreasing the fuel flow. However, using the variable guide vanes to reduce the flow renders in an offset of the compressor stage loading which has a negative impact on the efficiency.

Compressors are basically volumetric flow machines and if operated on a fixed speed, a change in inlet gas density will alter the mass-flow. This means that if the inlet air is heated, the mass-flow and hence load will be reduced if turbine inlet temperature is kept constant. Thanks to the more or less maintained volume flow the compressor is operated closer to its design point and efficiency remains high. A heat exchanger, preferably with water or steam from the bottoming cycle on the hot side, would be a simple solution to heat the inlet gas. A better use of the available energy would be to semi-close the cycle by recirculating a part of the exhaust gas flow.

Semi-closing the cycle means that less oxygen will be available in the combustion process and this will be one of the limiting factors for the recirculation rate. However, the fuel to air ratio decreases at part load and hence the oxygen surplus increases. Therefore, higher recirculation rates may be acceptable at part load compared to full load. The results from this thermodynamic study are very promising and show that a 40% recirculation rate can improve part load efficiency by as much as 4.1%.
Evaluation of a Volume of Fluid CFD Methodology for the Oil Film Thickness Estimation in an Aero-Engine Bearing Chamber
Authors: Bristot Andrea , Morvan Hervé P. , Simmons Kathy A.
Published: September 2016

The presented work aims to identify a Volume of Fluid (VOF) CFD approach for the transient simulation of air/oil flows inside an aero-engine bearing chamber. Typically VOF requires relatively fine grids and consequently small time-steps to sufficiently resolve the formation of oil films and their interaction with air flows. The need to achieve a stationary-state which requires flow times on the order of seconds makes the compromise between simulation accuracy and simulation times a challenging choice when using the VOF method. In this work, the use of the Compressive Interface Reconstruction scheme with bounded second order implicit time discretization has enabled a significant speed-up of the simulation times against the previously adopted explicit Geometric-Reconstruction scheme. The results are evaluated against experimental data available in the literature.
Predicting Flashback Limits of a Gas Turbine Model Combustor Based on Velocity and Fuel Concentration for H2-Air-Mixtures
Authors: Utschick Matthias , Eiringhaus Daniel , Köhler Christian , Sattelmayer Thomas
Published: September 2016

This study investigates the influence of the fuel injection strategy on safety against flashback in a gas turbine model combustor with premixing of H2-air-mixtures. The flashback propensity is quantified and the flashback mechanism is identified experimentally.

The A2EV swirler concept exhibits a hollow, thick walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow-injector, JICI). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector, TEI). Velocity and mixing fields in mixing zone and combustion chamber in isothermal water flow were measured with High-speed-Particle-Image-Velocimetry (PIV) and Highspeed-Laser-Induced-Fluorescence (LIF). The flashback limit was determined under atmospheric pressure for three air mass flows and 673 K preheat temperature for H2-air-mixtures. Flashback mechanism and trajectory of the flame tip during flashback were identified with two stereoscopically oriented intensified high-speed cameras observing the OH* radiation.

We notice flashback in the core flow due to Combustion Induced Vortex Breakdown (CIVB) and Turbulent upstream Flame Propagation (TFP) near the wall dependent on the injector type. The Flashback Resistance (FBR) defined as the ratio between a characteristic flow speed and a characteristic flame speed measures the direction of propagation of a turbulent flame in the flow field. Although CIVB cannot be predicted solely based on the FBR, its distribution gives evidence for CIVB-prone states.

The fuel should be injected preferably isokinetic to the air flow along the entire trailing edge in oder to reduce the RMS fluctuation of velocity and fuel concentration. The characteristic velocity in the entire cross section of the combustion chamber inlet should be at least twice the characteristic flame speed. The position of the stagnation point should be tuned to be located in the combustion chamber by adjusting the axial momentum. Those measures lead to safe operation with highly reactive fuels at high equivalence ratios.
Impact of Heat Release Distribution on the Spinning Modes of an Annular Combustor With Multiple Matrix Burners
Authors: Laera Davide , Prieur Kevin , Durox Daniel , Schuller Thierry , Camporeale Sergio M. , Candel Sébastien
Published: September 2016

Annular combustors of aero-engines and gas turbine are often affected by thermo-acoustic combustion instabilities coupled by azimuthal modes. Previous experiments as well as theoretical and numerical investigations indicate that the coupling modes involved in this process may be standing or spinning but they provide diverse interpretations of the occurrence of these two types of oscillations. The present article reports a numerical analysis of instability coupled by a spinning mode in an annular combustor. This corresponds to experiments carried out on the MICCA test facility equipped with 16 matrix burners. Each burner response is represented by means of a global experimental flame describing function (FDF) and it is considered that the flames are sufficiently compact to interact with the mode without mutual interactions with adjacent burning regions. A harmonic balance nonlinear stability analysis is carried out by combining the FDF with a Helmholtz solver to determine the system dynamics trajectories in a frequency-growth rate plane. The influence of the distribution of the volumetric heat release corresponding to each burner is investigated in a first stage. Even though the 16 burners are all compact with respect to the acoustic wavelength considered and occupy the same volume, simulations reveal an influence of this volumetric distribution on frequencies and growth rates. This study emphasizes the importance of providing a suitable description of the flame zone geometrical extension and correspondingly an adequate representation of the level of heat release rate fluctuation per unit volume. It is found that these two items can be deduced from a knowledge of the heat release distribution under steady state operating conditions. Once the distribution of the heat release fluctuations is unequivocally defined, limit cycle simulations are performed. For the conditions explored, simulations retrieve the spinning nature of the self-sustained mode that was identified in the experiments both in the plenum and in the combustion chamber.
Performance Simulation of 3-Stage Gas Turbine CHP Plant for Marine Applications
Authors: Wang Zhitao , Li Yi-Guang , Li Shuying
Published: September 2016

Energy saving and environment become important issues in power and propulsion generation industry. One of such examples is the marine transportation where a lot of energy from consumed fuel is wasted in exhaust and emissions are produced in vessel propulsion systems. The focus of this research is to look at a typical marine propulsion system where gas turbines are the prime movers and to investigate the potentials of a novel 3-stage gas turbine combined heat and power (CHP) system for marine applications. Such a CHP system may include a topping gas turbine Brayton cycle, an intermediate water Rankine cycle (WRC), and a bottoming organic Rankine cycle (ORC). In the system, gas turbine is connected with a generator to produce electricity, water Rankine cycle produces superheated steam driving steam turbine for electricity generation and/or for heating, and organic Rankine cycle is used to produce electricity by recycling low temperature energy. A thermodynamic model for the 3-stage CHP system is established to simulate the performance of the system at different power demand operating conditions. The developed performance simulation system has been applied to a typical model vessel propulsion system application. Based on the simulated results, it is evident that compared with a conventional 2-stage CHP cycle where only gas turbine topping cycle and water Rankine bottoming cycle are included, the introduction of the organic Rankine cycle can increase the power output by about 7% and improve the cycle thermal efficiency by about 3.52%.
Development of Next Generation Gas Turbine Combined Cycle System
Authors: Yamazaki Hiroyuki , Nishimura Yoshiaki , Abe Masahiro , Takata Kazumasa , Hada Satoshi , Masada Junichiro
Published: September 2016

Tohoku Electric Power Company, Inc. (Tohoku-EPCO) has been adopting cutting-edge gas turbines for gas turbine combined cycle (GTCC) power plants to contribute for reduction of energy consumption, and making a continuous effort to study the next generation gas turbines to further improve GTCC power plants efficiency and flexibility.

Tohoku-EPCO and Mitsubishi Hitachi Power Systems, Ltd (MHPS) developed “forced air cooling system” as a brand-new combustor cooling system for the next generation GTCC system in a collaborative project. The forced air cooling system can be applied to gas turbines with a turbine inlet temperature (TIT) of 1600deg.C or more by controlling the cooling air temperature and the amount of cooling air. Recently, the forced air cooling system verification test has been completed successfully at a demonstration power plant located within MHPS Takasago Works (T-point). Since the forced air cooling system has been verified, the 1650deg.C class next generation GTCC power plant with the forced air cooling system is now being developed. Final confirmation test of 1650deg.C class next generation GTCC system will be carried out in 2020.
Influence of Heat Transfer and Material Temperature on Combustion Instabilities in a Swirl Burner
Authors: Kraus Christian , Selle Laurent , Poinsot Thierry , Arndt Christoph M. , Bockhorn Henning
Published: September 2016

The current work focuses on the Large Eddy Simulation of a combustion instability in a laboratory-scale swirl burner. Air and fuel are injected at ambient conditions. Heat conduction from the combustion chamber to the plenums results in a preheating of the air and fuel flows above ambient conditions. The paper compares two computations with different modeling strategies. In the first computation, the temperature of the injected reactantsis 300 K (equivalent to the experiment) and the combustor walls are treated as adiabatic. The frequency of the unstable mode (≈ 635 Hz) deviates significantly from the measured frequency (≈ 750 Hz). In the second computation, the preheating effect observed in the experiment and the heat losses at the combustion chamber walls are taken into account. The frequency (≈ 725 Hz) of the unstable mode agrees well with the experiment. These results illustrate the importance of accounting for heat transfer/ losses when applying LES for the prediction of combustion instabilities. Uncertainties caused by unsuitable modeling strategies when using CFD for the prediction of combustion instabilities can lead to an improper design of passive control methods (such as Helmholtz resonators), as these are often only effective in a limited frequency range.
Effect of Buoyancy-Induced Rotating Flow on Temperatures of Compressor Discs
Authors: Tang Hui , Owen J. Michael
Published: September 2016

Calculation of the clearances between the blades and casing of the high-pressure-compressor rotors in aeroengines involves calculating the radial growth of the corotating compressor discs. This requires the calculation of the thermal growth of the discs, which in turn requires a knowledge of their temperatures and of the Nusselt numbers and the flow structure in the cavity between the discs. The authors have recently published a theoretical model of the buoyancy-induced flow in rotating cavities, and approximate solutions were obtained for laminar Ekman-layer flow on the discs; the equation for the Nusselt numbers, which includes two empirical constants, depends strongly on the Grashof number and on the radial distribution of disc temperature.

In this paper, Nusselt numbers and disc temperatures predicted by the buoyancy model are compared with values obtained from published experimental data. For most of the 19 test cases, with Grashof numbers up to nearly 1012, mainly good agreement was achieved between the theoretical and experimental distributions of Nusselt numbers and disc temperatures. This suggests that, owing to Coriolis effects, the laminar model of buoyancy-induced rotating flow could be valid even at the high Grashof numbers found in the compressor rotors of aeroengines. As predicted by the model, for a constant Grashof number increasing the rotational Reynolds number can cause a decrease in the Nusselt number.

This is the first time a theoretical model (rather than CFD) has been used to predict the temperatures of a compressor disc, and the model takes only seconds to predict disc temperatures that would take days or even weeks to predict using CFD. More experimental data is required if the model is to be used by the designers of compressor rotors, and suggestions for future research are given in the paper.
Development of a Comprehensive Model for Plasma Actuation in 3D-RANS-Simulations
Authors: Matzgeller Roland , Bleh Alexander , Klaubert Daniela
Published: September 2016

Being a comparably new technology, plasma actuation as a method to influence the flow in turbomachines has been investigated with a lot of effort in the past few years. Most of these investigations related to turbomachinery applications were carried out numerically using extensions to various RANS-codes and showed rather good improvements of the flow, particularly when using plasma actuators to suppress separations. Although most of these works gave a good impression of the capabilities of plasma actuators a comprehensive model of plasma actuation accounting for the impact of local static pressure, local temperature and the velocity of the flow passing the actuator was not presented yet. In this paper an extension to the proven and well validated RANS CFD code TRACE is presented which is able to model the influence of plasma actuation dependent on the local flow properties, i.e. dependent on the local static pressure, static temperature and Mach-number. This model extends the work of Lemire et al. [1] in a way that a comprehensive calibration based on open data is possible. In this paper, first the calibration is described followed by a validation in order to ensure that the model works correctly under different boundary conditions. The work is concluded by performing a numerical study applying a plasma actuator on different stator vanes along a generic high pressure compressor. Using this example the benefits of the extension to Lemire et al. [1], featuring the calibration for local static pressure, static temperature and Mach-number is explained and their impact on the potential of plasma actuation to suppress trailing edge separations is discussed.
Fatigue Behavior Comparisons Between Ultrasonic and Servohydraulic Axial Testing Procedures
Authors: Scott-Emuakpor Onome , George Tommy , Holycross Casey , Brown Jeffrey , Beck Joseph
Published: September 2016

An investigation of cycling rate effects on fatigue life behavior is being conducted on Aluminum (Al) alloys. This effect, along with specimen diameter, highlights the major difference between ultrasonic and servohydraulic fatigue test procedures. Ultrasonic fatigue testing is conducted on a 3.2 mm diameter hourglass specimen operating at 26 kHz, and servohydraulic axial testing is conducted on an ASTM E 466-07 standard dogbone specimen with a 25.4 mm gage length and 4.45 mm diameter operating at 35 Hz. Previous works have shown that cycling rate increases of 100–1000 times can reduce the fatigue crack growth rates in the stress intensity region between threshold and critical by at least an order of magnitude for aluminum and steel. For high cycle fatigue (HCF), however, where the majority of cycles to failure are accumulated before crack initiation, not during propagation, the effects of cycling rate on total loading cycles to failure needs further understanding, which may lead to more accurate and/or less conservative HCF design of critical gas turbine engine components. Fatigue behavior of Al 6061-T6 was assessed between the failure range of 104–1010 cycles using ultrasonic and servohydraulic testing procedures. Though aluminum is not a widely used alloy in gas turbine engine applications, understanding frequency-based fatigue life discrepancies associated with the choice of empirical methods is of paramount importance to component design; Aluminum 6061-T6 is the most cost-effective way to gaining this understanding. Comparisons were made between the fatigue behavior results using cycling rate (also stated as strain-rate or frequency) comparisons for fatigue crack growth study. The comparisons show promising results correlating the fatigue behavior trends of servhydraulic and ultrasonic fatigue data.
Performance Characterization of Twin Scroll Turbine Stage for Vehicular Turbocharger Under Unsteady Pulsating Flow Environment
Authors: Lee Jinwook , Tan Choon S. , Sirakov Borislav T. , Wilkins Chris , Im Hong-Sik , Babak Martin , Tisserant Denis
Published: September 2016

Unsteady three-dimensional computations have been implemented on a turbocharger twin-scroll turbine system (volute-turbine wheel-diffuser). The flow unsteadiness in a turbocharger turbine system is essentially driven by a highly pulsating flow from the upstream combustor which causes a pulsating stagnation pressure boundary condition at the inlet to the turbine system. Computed results have been post-processed and interrogated in depth in order to infer the significance of the induced flow unsteadiness on performance. The induced flow unsteadiness could be deemed important since the reduced frequency of the turbine system (based on the time scale of the inlet flow fluctuation and the flow through time) is higher than unity. Thus, the computed time-accurate pressure field and the loss generation process have been assessed to establish the causal link to the induced flow unsteadiness in the turbine system. To do this consistently both for the individual subcomponents and the system, a framework of characterizing the operation of the turbine system linked to the fluctuating inlet stagnation pressure is proposed. The framework effectively categorizes the operation of the unsteady turbine system in both spatial and temporal dimension; such a framework would facilitate determining whether the loss generation process in a subcomponent can be approximated as unsteady (e.g. volute) or as locally quasi-steady (e.g. turbine wheel) in response to the unsteady inlet pulsation in the inlet-to-outlet stagnation pressure ratios of the two inlets. The notion that a specific subcomponent can be approximated as locally quasi-steady while the entire turbine system in itself is unsteady is of interest as it suggests a strategy for an appropriate flow modeling and scaling as well as for the turbine system performance improvement. Also, computed results are used to determine situations where the flow effects in a specific subcomponent can be approximated as quasi-one-dimensional; thus for instance the flow mechanisms in the volute can reasonably be approximated on an unsteady one-dimensional basis. For a turbine stage with sudden-expansion type diffuser, the framework for integrating sub-component models into a turbine system is formulated. The effectiveness and generality of the proposed framework is demonstrated by applying it to three distinctly different turbocharger operating conditions. The estimated power from the integrated turbine system model is in good agreement with the full unsteady CFD results for all three situations. The formulated framework will be generally applicable for assessing the new design configurations as long as the corresponding high fidelity steady CFD results are utilized to determine the quasi-steady (or acoustically compact) behavior of each new sub-component.
Experimental and Numerical Investigations on the Aerodynamic Performance of the Three-Stage Turbine With Consideration of the Leakage Flow Effect
Authors: Chen Yang , Li Jun , Tian Chaoyang , Zhong Gangyun , Fan Xiaoping , Kong Xianglin
Published: September 2016

The aerodynamic performance of three-stage turbine with different types of leakage flows was experimentally and numerically studied in this paper. The leakage flows of three-stage turbine included the shroud seal leakage flow between the rotor blade tip and case, the diaphragm seal leakage flow between the stator blade diaphragm and shaft, as well as the shaft packing leakage flow and the gap leakage flow between the rotor blade curved fir-tree root and wheel disk.

The total aerodynamic performance of three-stage turbine including leakage flows was firstly experimentally measured. The detailed flow field and aerodynamic performance were also numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and S-A turbulence model. The numerical mass flow rate and efficiency showed well agreement with experimental data. The effects of leakage flows between the fir-tree root and the wheel disk were studied. All leakage mass flow fractions, including the mass flow rate in each hole for all sets of root gaps were given for comparison. The effect of leakage flow on the aerodynamic performance of three-stage was illustrated and discussed.
Influence of Mach Number on Profile Loss of Axial-Flow Gas Turbine Blades
Authors: Kibsey M. D. , Sjolander S. A.
Published: September 2016

The current profile loss prediction methods for axial turbine blades usually predict a monotonic increase in profile losses at outlet Mach numbers above 1.0, while linear cascade testing in the literature has revealed a more complex behaviour. An objective of this investigation was to help clarify the flow features that are most influential on the profile losses in the transonic and supersonic regimes. Four linear cascades of turbine blades were investigated both experimentally and computationally, at design incidence. Measurements were carried out over an outlet Mach number range of roughly 0.5 to 1.4, and a Reynolds number range of about 5 × 105 to 1.4×106.

It was found that the profile losses of the four cascades exhibited a loss “plateau”, where the total pressure loss coefficient became approximately constant over a range of outlet Mach numbers spanning the low supersonic range. Cascades of different geometries exhibited different extents of this loss plateau, and a commonly used Mach number correction for profile losses did not capture the behaviour.

In the literature, a relationship has been observed between the base pressure and the profile losses. The base pressure was linked to the losses in the trailing edge wake and in the trailing edge shock system. For this reason, base pressure data were obtained from blades instrumented with a static tap at the trailing edge, and also from computational fluid dynamics (CFD). The results provided insight into the role of the base pressure in the profile losses through the transonic regime. It was concluded from this study that an accurate prediction of the base pressure may serve as a basis for a revised Mach number correction to be applied to the profile loss correlation in the transonic and supersonic flow regimes.