bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Investigations of the Aerodynamics of Highly Loaded Tandem Vanes in a High-Speed Stator Cascade
Authors: Heinrich Alexander , Tiedemann Christine , Peitsch Dieter 
Published: August 2017

Tandem blade configurations are said to being able to outperform conventional single blades in terms of loss behaviour and flow turning. The work presented here is supported by experimental investigations which were conducted at a 2D linear stator cascade at the Chair for Aero Engines at the Technische Universität Berlin. Two different tandem blade configurations with a different load split are examined and compared against a conventional single reference blade.
Multi-coloured oil flow visualisation complemented by wake flow measurements show the development of the secondary flow structures and enable a thorough understanding of the impact of varying tangential displacement for tandem blades. The results show that tandem blades can reduce the total pressure losses, especially in the midspan region, which also results in smaller overall values. In addition, the incidence angle variation has shown that the working range of the tandem vanes exceeds the originally designed working range of the single reference blade. The tandem configurations still allow flow guidance at stall condition and prove the capability of the concept.
Validation of a Numerical Model for Predicting Stalled Flows in a Low-Speed Fan
Authors: Lee Kuen-Bae , Wilson Mark , Vahdati Mehdi 
Published: August 2017

This paper investigates the rotating stall for a low-speed/low-pressure ratio fan blade. The type of stall studied in this paper is similar to the multi cell, part span rotating stall, which can occur on the front stages of the core compressors. Although this type of rotating stall may not result in surge or massive loss of power, it can cause excessive vibration and noise.
It was found that the standard Spalart-Allmaras (SA) model implemented in the CFD solver used in this work predicts premature stall, which is in line with the observation of other researchers who use the SA model. Therefore, to improve the prediction of the stall boundary, the standard SA model was modified by scaling the source term in the model based on the local pressure gradient and the velocity helicity of the flow. Furthermore, a generalized wall function valid for non-zero wall pressure gradient was implemented to improve the accuracy of boundary conditions at the wall. The turbulence modelling part of this work aims to produce a turbulence model which can be used to model the flows near the stall boundary for the transonic fan blades on relatively coarse grids of around 300k points per passage. Initially, two fan blades with different design and operating speeds were used to optimize the new parameters in the modified turbulence model. The optimization was based on improving the correlation between measured and numerical radial profiles of the pressure ratio. Thereafter, steady computations were performed for two other blades (with the same parameters) and the predictions were compared with the experimental data for all the four fan blades. Numerical results showed a significant improvement over those obtained with the original SA model, when compared against the measured data.
In the second part, the modified turbulence model was used to study the flow near the stalled region. Three-dimensional, whole assembly unsteady simulations were performed for a modern low speed fan rig for which extensive measured data were available. Stall simulations were conducted at 80% speed, which contained a part with positive slope on the measured constant speed characteristic. The results indicated that by using an unsteady whole assembly approach and the modified turbulence model, it is possible to predict the flow for all the points on the measured constant speed characteristic (including those on the positive slope part).
Design and Testing for Ceramic Matrix Composite Turbine Vane
Authors: Watanabe Fumiaki , Nakamura Takeshi , Mizokami Yousuke 
Published: August 2017

Ceramic matrix composite (CMC) have higher temperature capability and lower density than nickel based alloys which have been used for hot section components of gas turbine engines. These properties are expected to bring many benefits, such as higher turbine inlet temperature (TIT), reduction of cooling air, and reduction of weight, when it is used as the material for hot section components of gas turbine engine.
The authors have been developing CMC turbine vane for aircraft engines. In this paper, the authors present the summary of design, manufacturing, and testing, which were conducted from 2010 to 2012.
The purpose of this work was to verify that the SiC-SiC CMC which IHI has developed has the applicability to aircraft turbine vanes. The concept was planned for CMC hollow turbine vanes, in which the airfoil and the platform are fabricated in CVI process. As the demonstration of this concept, the first stage turbine vane was designed with CMC for IHI IM270 that is the 2MW-class small industrial gas turbine engine.
Bending rig test was conducted at room temperature in order to check the structural feasibility of the airfoil-platform joint. The outer platform of vane was fixed in the same way with the engine parts, and the load simulating the aerodynamic force was applied at the airfoil portion. The fracture load was higher than the load which the vanes receive in the actual engine.
Burner rig test was conducted in order to check the durability against thermal cycle. A CMC vane was set between dummy metal vanes, and cyclically heated by gas burner. The maximum airfoil surface temperature was set to 1200 degree C, and the maximum temperature difference between airfoil and platform was about 700 degree C. The minimum airfoil temperature at the interval of heating was about 300 degree C. The time of one thermal cycle was 6 minutes that consisted of 3 minute heating and 3 minute natural cooling. The test was conducted for 1,000 cycles. In post-test inspection there was no defect like a crack.
Engine test for CMC vanes was conducted using IHI IM270. The four CMC vanes were mounted into the first stage turbine nozzle assembly in place of the normal metal vanes. The test was conducted for 400 hours. The inlet temperature of CMC vanes were measured by thermocouples installed at the leading edge, and the measured temperature was about 1050 degree C at the steady state.
From this work, the applicability of the design concept for the CMC vane to actual engine was verified in which airfoil-platform are fabricated in CVI process.
Detailed Numerical Study of the Main Sources of Loss and Flow Behavior in Low Pressure Steam Turbine Exhaust Hoods
Authors: Munyoki Dickson , Schatz Markus , Vogt Damian M. 
Published: August 2017

The performance of the axial-radial diffuser downstream of the last low-pressure steam turbine stages and the losses occurring subsequently within the exhaust hood directly influences the overall efficiency of a steam power plant. It is estimated that an improvement of the pressure recovery in the diffuser and exhaust hood by 10% translates into 1% of last stage efficiency [11].
While the design of axial-radial diffusers has been the object of quite many studies, the flow phenomena occurring within the exhaust hood have not received much attention in recent years. However, major losses occur due to dissipation within vortices and inability of the hood to properly diffuse the flow. Flow turning from radial to downward flow towards the condenser, especially at the upper part of the hood is essentially the main cause for this.
This paper presents a detailed analysis of the losses within the exhaust hood flow for two operating conditions based on numerical results. In order to identify the underlying mechanisms and the locations where dissipation mainly occurs, an approach was followed, whereby the diffuser inflow is divided into different sectors and pressure recovery, dissipation and finally residual kinetic energy of the flow originating from these sectors is calculated at different locations within the hood.
Based on this method, the flow from the topmost sectors at the diffuser inlet is found to cause the highest dissipation for both investigated cases. Upon hitting the exhaust hood walls, the flow on the upper part of the diffuser is deflected, forming complex vortices which are stretching into the condenser and interacting with flow originating from other sectors, thereby causing further swirling and generating additional losses.
The detailed study of the flow behavior in the exhaust hood and the associated dissipation presents an opportunity for future investigations of efficient geometrical features to be introduced within the hood to improve the flow and hence the overall pressure recovery coefficient.
Geometric Modeling and Analysis for Gooseneck II: 2D Simplified Model for Quick Assessment
Authors: Tu Qiuye , Deng Rutan , Zhang Dongdong , Sun Xingjian 
Published: August 2017

In the previous studies, the proposed method for gooseneck geometric modeling employed two polynomials to construct the inner-wall and area distribution curves. The inflection point location served as the variable to control the inner-wall polynomial curve, and the peak point location and peak value to control the area distribution polynomial curve. In the effort to be quickly located, the control variables were provided with more geometric meaning. 3D numerical simulations indicated that there existed a total pressure recovery island for given solution area of the three control variables. Consequently, the relationships between the geometric parameters and the total pressure loss were set up.
This paper focused on the 2D simplifications to quickly address the control variables for the total pressure island. The studies were conducted in three aspects. First, the simplified model took the constructional blocking effects of struts into account. The baseline of the 2D simplified modeling was set at 30% spanwise near the hub through comparisons of different settings. Therefore, 70% blocking area compensated to outer-wall and 30% to inner-wall along the normal direction of the baseline. The 2D simulation results indicated that the static pressure distribution was consistent with the 3D results, but waves exited at the end walls of both leading and trailing edges due to the geometric changes. Second, the simplification considered the blocking effects of the wake. The wake was converted to boundary layer thickness, and moreover, compensation to the end wall was similar with the constructional blocking of struts. The simulation results revealed that wake blocking had very small impacts to the simplification, although the peak values of static pressure slightly increased at the end wall. Third, smoothing treatments were done for both inner-wall and outer-wall after the above compensating transformations. The results showed that smoothing treatments were very necessary and improved the waves located at end wall on the static pressure distribution which was nearly the same with 3D results. After all the simplifying treatments above, the final 2D results had almost the same total pressure loss distributions with the 3D results, and could save at least 40% calculation time as a quick assessment used to search the reasonable geometric solution areas of inflection point location and peak point location for minimum total pressure loss of the gooseneck.
Thermal Properties for the Simulation of Direct-Fired sCO2 Combustor
Authors: Manikantachari K. R. V. , Martin Scott , Bobren-Diaz Jose O. , Vasu Subith 
Published: August 2017

The direct-fired supercritical CO2 (sCO2) cycle is currently considered as a zero-emission power generation concept. It is of interest to know how to optimize various components of this cycle using computational tools, however, a comprehensive effort on this area is currently lacking. In this work, the behavior of thermal properties of sCO2 combustion at various reaction stages has been investigated by coupling real gas CHEMKIN (CHEMKIN-RG) with an in-house Premixed Conditional Moment Closure (PCMC) code and the high pressure Aramco-2.0 kinetic mechanism. Also, the necessary fundamental information for sCO2 combustion modelling is reviewed.
The Soave-Redlich-Kwong equation of state (SRK EOS) is identified as the most accurate EOS to predict the thermal states at all turbulence levels. Also, an empirical model for the compression factor Z is proposed for sCO2 combustors, which is a function of mixture inlet conditions and the reaction progress variable. This empirical model is validated between the operating conditions 250–300 bar, inlet temperatures of 800–1200 K and within the current designed inlet mole fractions and the accuracy is estimated to be less than 0.5% different from the exact relation. For sCO2 operating conditions the compression factor Z always decreases as the reaction progresses and this leads to the static pressure loss between inlet and exit of the sCO2 combustor.
Further, a review of high pressure viscosity and thermal conductivity models of mixtures and pure-components are presented from the literature and suggestions are made for their adoptability in sCO2 combustor simulations. The thermal properties such as specific heats, speed of sound, pressure exponent and isothermal compressibility are accurately quantified.
Development and Testing of a Gas Turbine Engine Combustion Air Inlet Filtration System for the USMC Amphibious Combat Vehicle
Authors: Gastopoulos Thomai , Lawton Joseph 
Published: August 2017

The Auxiliary Ships and New Acquisition Support Branch (Code 425) of the Naval Surface Warfare Center, Philadelphia Division conducted a study to assist the Marine Corps Systems Command in assessing the feasibility of using a gas turbine engine as a propulsion system on future United States Marine Corps Amphibious Combat Vehicles (ACV). The study was focused on developing and testing a gas turbine intake solution for the ACV that can remove saltwater from the intake airstream of a notional 3,000 horsepower ACV engine.
Code 425 developed a two-part solution for the intake of the ACV. The first part of the solution is an intake shroud designed to elevate the intake to protect the engine from deck water wash. The second part of the solution is the Combustion Air Separation System (CASS), a gas turbine intake filtration system designed to remove marine contaminants that enter the intake. Code 425 tested a CASS prototype for its efficiency at removing saltwater spray and bulk water up to 10 gallons per minute. Test results showed that the CASS met each requirement and that an ACV intake system incorporating both the intake shroud and the CASS should protect the gas turbine engine from saltwater ingestion.
Life Extension of Power Turbine Disks Exposed to In-Service Corrosion Damage
Authors: Dua Dipankar , Khajavi Mohammad , Hill Matthew 
Published: August 2017

Siemens Energy has a large fleet of aero derivative gas turbines installed in oil & gas and power generation applications globally. Over the past several years, several incidents of disk corrosion damage have been observed during the power turbine overhauls especially for the units fielded in marine environment. Most of the corrosion attack has been observed at disk firtree (blade attachment features), gas washed disk faces and torque transmission features. In all of these cases the mechanism for corrosion has been identified as Low Temperature Hot Corrosion (LTHC) also known as Type-II sulphidation.
Siemens has explored a number of potential operating and/or design options e.g. utilization of more corrosion resistant alloys and coatings to mitigate the effects of the corrosive attack on these disks. However, many of these proposals are either intermediate or long term solutions and are addressed more towards new power turbine disks rather than those that are already in service.
In the short term, Siemens technical solution has focused on development of proprietary repair processes to effectively remove the corrosion damage and extend the operational life of in-service disks as well as salvage some of the previously scraped disks.
This Paper discusses the methodology and findings from the development and characterization of the repair of the power turbine disks when exposed to corrosion and other operational damage.
Aerodynamic Optimization of High Pressure Turbine and Interstage Duct in a Two-Stage Air System for a Heavy-Duty Diesel Engine
Authors: Khairuddin Uswah , Costall Aaron W. 
Published: August 2017

Turbochargers are a key technology for reducing the fuel consumption and CO2 emissions of heavy-duty internal combustion engines by enabling greater power density, which is essential for engine downsizing and downspeeding. This in turn raises turbine expansion ratio levels and drives the shift to air systems with multiple stages, which also implies the need for interconnecting ducting, all of which is subject to tight packaging constraints.
This paper considers the challenges in the aerodynamic optimization of the exhaust side of a two-stage air system for a Caterpillar 4.4-litre heavy-duty diesel engine, focusing on the high pressure turbine wheel and interstage duct. Using the current production designs as a baseline, a genetic algorithm-based aerodynamic optimization process was carried out separately for the wheel and duct components in order to minimize the computational effort required to evaluate seven key operating points.
While efficiency was a clear choice for the cost function for turbine wheel optimization, the most appropriate objective for interstage duct optimization was less certain, and so this paper also explores the resulting effect of optimizing the duct design for different objectives. Results of the optimization generated differing turbine wheel and interstage duct designs depending on the corresponding operating point, thus it was important to check the performance of these components at every other operating point, in order to determine the most appropriate designs to carry forward. Once the best compromise high pressure turbine wheel and interstage duct designs were chosen, prototypes of both were manufactured and then tested together against the baseline designs to validate the CFD predictions. The best performing high pressure turbine design, wheel A, was predicted to show an efficiency improvement of 2.15 percentage points, for on-design operation. Meanwhile, the optimized interstage duct contributed a 0.2 and 0.5 percentage-point efficiency increase for the high and low pressure turbines, respectively.
Integrated Electrical Machine-Turbo Machinery
Authors: Al-ani M. M. J. , Lee S. P. , Allport J. M. 
Published: August 2017

Global warming and climate change due to rising levels of greenhouse gases have placed significant pressure on the automobile industry to adopt more clean fuel, transportation electrification, and waste energy recovery technologies. As a result, several electrically assisted or driven turbo-machines have been proposed such as turbochargers, turbo-compressors, and electrical boosters. Therefore, the electrification of turbo-machinery has been trending for the past decade.
All the systems mentioned above consist of a conventional electrical machine connected to the turbo-machinery by a shaft, making the system relatively large, heavy, costly and mechanically complex.
In this paper, an integrated electrical machine-turbo machinery concept is proposed. It consists of an electrical machine mounted around a salient rotor that is shaped like an axial flow turbo-machinery wheel. The electrical machine can be used as a motor to drive or assist the operation of the turbo-machine or it can operate as a generator powered by the gas or fluid flow. Compared to the conventional electrically derived or assisted turbo-machine systems, the proposed system is expected to decrease the overall size, weight and complexity.
In order to illustrate this concept, an initial multi-physics feasibility study is presented. Electromagnetic and mechanical, performance are calculated and investigated using FEA. Additionally, aerodynamic consideration has been illustrated.
Towards Investigation of External Oil Flow From a Journal Bearing in an Epicyclic Gearbox
Authors: Berthold Martin , Morvan Hervé , Young Colin , Jefferson-Loveday Richard 
Published: August 2017

High loads and bearing life requirements make journal bearings the preferred choice for use in high power, epicyclic gearboxes in jet engines. In contrast to conventional, non-orbiting journal bearings in epicyclic star gearboxes, the kinematic conditions in epicyclic planetary arrangements are much more complex. With the planet gears rotating about their own axis and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing.
This paper presents a literature and state-of-the-art knowledge review to identify existing work performed on cases similar to external journal bearing oil flow. In order to numerically investigate external journal bearing oil flow, an approach to decompose an actual journal bearing into simplified models is proposed. Later, these can be extended in a step-wise manner to allow key underlying physical phenomena to be identified. Preliminary modeling considerations will also be presented. This includes assessing different geometrical inlet conditions with the aim of minimizing computational requirements and different numerical models for near-wall treatment. The correct choice of near-wall treatment models is particularly crucial as it determines the bearing’s internal and external thermal behavior and properties. The findings and conclusions are used to create a three dimensional (3D), two-component computational fluid dynamic (CFD) sector model with rotationally periodic boundaries of the most simplistic approximation of an actual journal bearing: a non-orbiting representation, rotating about its own axis, with a circumferentially constant, i.e. concentric, lubricating gap. The inlet boundary conditions for simulating the external oil flow are generated by partly simulating the internal oil flow within the lubricating gap. In order to track the phase interface between the oil and the air surrounding the bearing, the Volume of Fluid (VoF) method is used. The quality of the CFD simulations of the domain of interest is not only dependent on the accuracy of the inlet conditions, but is also dependent on the computational mesh type, cell count, cell shape and numerical methods used. External journal bearing oil flow was simulated with a number of different mesh densities and the effect on the flow field behavior will be discussed. Two different operating temperatures, representing low and high viscosity oil, were used and their effect on the flow field behavior will also be assessed.
In order to achieve the future objective of creating a design tool for routine use, key areas will be identified in which further progress is required. This includes the need to progressively increase the model fidelity to eventually simulate an orbiting journal bearing in planetary configuration with an eccentric, i.e. convergent-divergent, lubricating gap.