bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Parametric Study of an Exhaust Recovery Turbogenerator on a Diesel-Electric Hybrid Bus
Authors: Briggs Ian , McCullough Geoffrey , Spence Stephen , Douglas Roy , O’Shaughnessy Richard , Hanna Alister , Rouaud Cedric , Seaman Rachel 
Published: November 2013

The fuel consumption of automotive vehicles has become a prime consideration to manufacturers and operators as fuel prices continue to rise steadily, and legislation governing toxic emissions becomes ever more strict. This is particularly true for bus operators as government fuel subsidies are cut or removed.
In an effort to reduce the fuel consumption of a diesel-electric hybrid bus, an exhaust recovery turbogenerator has been selected from a wide ranging literature review as the most appropriate method of recovering some of the wasted heat in the exhaust line. This paper examines the effect on fuel consumption of a turbogenerator applied to a 2.4-litre diesel engine.
A validated one-dimensional engine model created using Ricardo WAVE was used as a baseline, and was modified in subsequent models to include a turbogenerator downstream, and in series with, the turbocharger turbine. A fuel consumption map of the modified engine was produced, and an in-house simulation tool was then used to examine the fuel economy benefit delivered by the turbogenerator on a bus operating on various drive-cycles.
A parametric study is presented which examined the performance of turbogenerators of various size and power output. The operating strategy of the turbogenerator was also discussed with a view to maximising turbine efficiency at each operating point.
The performance of the existing turbocharger on the hybrid bus was also investigated; both the compressor and turbine were optimised and the subsequent benefits to the fuel consumption of the vehicle were shown.
The final configuration is then presented and the overall improvement in fuel economy of the hybrid bus was determined over various drive-cycles.
Effect of NGV Lean Under Influence of Inlet Temperature Traverse
Authors: Rahim A. , Khanal B. , He L. , Romero E. 
Published: November 2013

One of the most widely studied parameters in turbine blade shaping is blade lean, i.e. the tangential displacement of spanwise sections. However, there is a lack of published research that investigates the effect of blade lean under non-uniform temperature conditions (commonly referred to as a ‘hot-streak’) that are present at the combustor exit. Of particular interest is the impact of such an inflow temperature profile on heat transfer when the NGV blades are shaped.
In the present work a computational study has been carried out for a transonic turbine stage using an efficient unsteady Navier-Stokes solver (HYDRA). The configurations with a nominal vane and a compound leaned vane under uniform and hot-streak inlet conditions are analysed. After confirming the typical NGV loading and aero-loss redistributions as seen in previous literature on blade lean, the focus has been directed to the rotor aerothermal behavior. Whilst the overall stage efficiencies for the configurations are largely comparable, the results show strikingly different rotor heat transfer characteristics. For a uniform inlet, a leaned NGV has a detrimental effect on the rotor heat transfer. However, once the hot-streak is introduced, the trend is reversed; the leaned NGV leads to favourable heat transfer characteristics in general and for the rotor tip region in particular. The possible causal links for the observed aerothermal features are discussed.
The present findings also highlight the significance of evaluating NGV shaping designs under properly conditioned inflow profiles, rather than extrapolating the wisdom derived from uniform inlet cases. The results also underline the importance of including rotor heat transfer and coolability during the NGV design process.
Electrically Driven On Demand Oil System for Gas Turbine Engines
Authors: Spytek Christopher J. 
Published: November 2013

An on demand oil system, based on electrically driven lube and scavenge pumps, for use in gas turbine engines has been developed. The need to optimize gas turbine engine performance, coupled with ‘electrification’ of aircraft systems, as on the Lockheed F35 and Boeing 787 in order to maximize efficiency and flexibility, created an opportunity to develop a ‘smart’ electrically driven lubrication system for gas turbine engines. Spytek’s electric oil system, developed for use on its 400lbt ATG-2 engine platform, ascertains the operating condition of the gas turbine engine, including speed, pressure, bearing temperatures and determines the amount of lubrication required for each bearing zone. The system has the benefit of better thermal control of engine bearings, lower system weight and power use, with flexibility in the placement of the system on the engine/airframe combination. The system has been successfully demonstrated on the Spytek Aerospace ATG-2/J304 gas turbine engine series.
Major areas addressed in the development of the system were the selection of reliable, gas turbine engine compatible feed and scavenge pumps, control systems sensoring and feedback, variable feed of oil to the individual sump wells, as well as systems durability and operating parameters. Various gas turbine engine platforms can require altered oil system duty cycles, including pre-oiling or post run down-oiling, high flow oil conditions, features not readily available in traditional mechanical systems but easily implemented using the Spytek on-demand oil system.
In the project effort, evaluation of the existing prototype system was used as a system design baseline. Data on pump wear, filter performance and oil supply degradation was available and used in refining the oil system design. The ATG-2 system was modified to take advantage of a full proportional integral derivative controlled oil system with system demonstrations made on a gas turbine engine, demonstrating oil supply on demand capability and full bearing thermal management system control.
Preliminary Aero Engine Life Assessment via Techno-Economic Environmental Risk Analysis
Authors: Navaratne Rukshan , Camilleri William , Najafi Esmail , Sethi Vishal , Pilidis Pericles 
Published: November 2013

Significant progress has been made towards the improvement of engine efficiency through the increase in overall pressure ratio (OPR) and reduction in specific thrust (SFN). The implications of engine design extend beyond thermodynamics and should include the consideration of multi-disciplinary aspects related to operation, emissions, lifing and cost. This paper explores the relationship between fuel burn and engine life across the design space of a typical aircraft engine integrated system.
In this context the Cranfield University Techno-economic Environmental Risk Analysis (TERA) methodology allows for the assessment of environmental and economic risk when the design of an engine system is at its conceptual stage. It is essentially a multi-disciplinary optimization framework which can be used for design space exploration. Such an approach is necessary in order to assess the trade-off between asset life and powerplant efficiency at the preliminary stage of the design process.
A parametric study was conducted in order to assess the sensitivity of major design parameters on engine life and specific fuel consumption (SFC) for a given engine type. The principal failure modes of creep, fatigue and oxidation, were considered for engine life estimation. In addition an optimization study was carried out in order to investigate the trade-off between fuel burn and engine life as Time Between Overhaul (TBO). This was accomplished by integrating aircraft performance, engine performance and lifing models in the TERA Framework.
An increase in turbine entry temperature (TET) is required to maintain efficiency at OPR. However, as TET has a strong influence on engine life there is an important trade-off to be made against engine efficiency. The parametric study outlined in this work explores the design space both with respect to engine life as well as efficiency. The optimization study showed that a penalty of 1.42kg additional fuel is required per additional hour of TBO. The fuel penalty is a consequence of sub-optimal design parameters with respect to engine efficiency and is applicable for the presented engine aircraft combination.
Development and Validation of a Physics-Based, Dynamic Model of a Gas Turbine
Authors: Wiese Ashley P. , Blom Matthew J. , Brear Michael J. , Manzie Chris , Kitchener Anthony 
Published: November 2013

This paper presents and validates a physics-based, dynamic model of a gas turbine. The model is an extension of that proposed by Badmus et al. [1], such that representation of a complete gas turbine is achieved. It includes new models of several gas turbine components, in particular the turbine and compressor, and also applies a well known method for prescribing boundary conditions [10] to the gas path.
This model first uses data from a previously published, static model of the same gas turbine to determine this dynamic model’s many so-called ‘forcing terms’. A least-squares optimisation is then undertaken to estimate the shaft inertia and the thermal inertia of system components using transient test data. Importantly, these optimised results are all close to physically reasonable estimates. Further, they show that the shaft dynamics are only significant for a short period at the start of most transients, after which the dynamic effects of thermal storage are dominant.
The complete gas turbine model is then validated against transient test data. Whilst the simulated traces demonstrate some steady-state error arising from the static model [12], the overall system dynamics appear to be captured well. Since steady-state error can be integrated out in a control system, this suggests that the proposed dynamic model is appropriate for use in a model-based, gas turbine controller.
A Critical Numerical Review of Loss Correlation Models and Smith Diagram for Modern Low Pressure Turbine Stages
Authors: Bertini Francesco , Ampellio Enrico , Marconcini Michele , Giovannini Matteo 
Published: November 2013

The Smith diagram, originally published in 1965, has been largely exploited as a preliminary design (PD) tool for axial turbines. Currently, it is applied to aeronautical Low Pressure Turbines (LPTs) in order to define basic characteristics during the feasibility study and to compare different configurations.
The Smith diagram represents a correlation of stage performance (η) as function of flow coefficient (ϕ) and loading factor (Ψ), but it does not take into account the effects of some important input parameters (individual contributions of loss, Reynolds number, Aspect Ratio, Rotor Tip Clearance (RTC)) and does not report some key design outputs (deflection angles (δ), profile weights and stresses), which have also a direct relation with the configuration position on the Smith diagram.
This study employs meanline analyses incorporating traditional loss correlation models used in the turbine field to compare results with the original Smith diagram. The correlation approach allows one to obtain other important multidisciplinary information (primarily aero-mechanical) which was previously absent, which leads to some strategic design achievements. The investigation process is based on a reference two-stage turbine properly set to match specific operating points on the Smith diagram. Several three-dimensional blade geometries have been prepared and then detailed 3D CFD analyses have been performed in order to acquire confidence with respect to the meanline results.
This research adds important information for turbine module design to the Smith chart and allows for a numerical revision of the diagram itself, fine tuning it with data obtained from the analyses of modern blades optimized for high stage performance.
Finally numerically-based loss predictors, broadly applicable to LPTs during optimization procedures before detailed CFD analyses, are presented and discussed.
Effect of Manufacturing Variability on Turbine Engine Performance: A Probabilistic Study
Authors: Gorelik Michael , Obayomi Jacob , Slovisky Jack , Frias Dan , Swanson Howie , McFarland John , Enright Michael , Riha David 
Published: November 2013

While turbine engine Original Equipment Manufacturers (OEMs) accumulated significant experience in the application of probabilistic methods (PM) and uncertainty quantification (UQ) methods to specific technical disciplines and engine components, experience with system-level PM applications has been limited.
To demonstrate the feasibility and benefits of an integrated PM-based system, a numerical case study has been developed around the Honeywell turbine engine application. The case study uses experimental observations of engine performance such as horsepower and fuel flow from a population of engines. Due to manufacturing variability, there are unit-to-unit and supplier-to-supplier variations in compressor blade geometry. Blade inspection data are available for the characterization of these geometric variations, and CFD analysis can be linked to the engine performance model, so that the effect of blade geometry variation on system-level performance characteristics can be quantified. Other elements of the case study included the use of engine performance and blade geometry data to perform Bayesian updating of the model inputs, such as efficiency adders and turbine tip clearances.
A probabilistic engine performance model was developed, system-level sensitivity analysis performed, and the predicted distribution of engine performance metrics was calibrated against the observed distributions. This paper describes the model development approach and key simulation results. The benefits of using PM and UQ methods in the system-level framework are discussed.
This case study was developed under Defense Advanced Research Projects Agency (DARPA) funding which is gratefully acknowledged.
Radial Turbine Rotor Response to Pulsating Inlet Flows
Authors: Cao Teng , Xu Liping , Yang Mingyang , Martinez-Botas Ricardo F. 
Published: November 2013

The performances of automotive turbocharger turbines have long been realized to be quite different under pulsating flow conditions compared to that under the equivalent steady and quasi-steady conditions on which the conventional design concept is based. However, the mechanisms of this phenomenon are still intensively investigated nowadays.
This paper presents an investigation of the response of a stand-alone rotor to inlet pulsating flow conditions by using validated unsteady Reynolds Averaged Navier-Stokes solver (URANS). The effects of the frequency, the amplitude and the temporal gradient of pulse waves on the instantaneous and cycle integrated performances of a radial turbine rotor in isolation were studied, decoupled from the upstream turbine volute. Numerical method was used to help gaining the physical understandings of these effects.
A validation of the numerical method against the experiments on a full configuration of the turbine has been performed prior to the numerical tool being used in the investigation. The rotor is then taken out to be studied in isolation. The results show that the turbine rotor alone can be treated as a quasi-steady device only in terms of cycle integrated performance; however, instantaneously, the rotor behaves unsteadily which increasingly deviates from the quasi-steady performance as the local Strouhal number of the pulsating wave is increased. This deviation is dominated by the effect of quasi-steady time-lag; at higher local Strouhal number, the transient effects also become significant. Based on this study, an interpretation and a model of estimating the quasi-steady time lag have been proposed; a criterion for unsteadiness based on the temporal local Strouhal number concept is developed, which reduces to the Λ criterion proposed in the published literature when cycle averaged; this in turn emphasizes the importance of the pressure wave gradient in time.
Axial Compressor Degradation Effects on Heavy Duty Gas Turbines Overall Performances
Authors: Astrua Pio , Cecchi Stefano , Piola Stefano , Silingardi Andrea , Bonzani Federico 
Published: November 2013

The operation of a gas turbine is the result of the aero-thermodynamic matching of several components which necessarily experience aging and degradation over time. An approach to treat degradation phenomena of the axial compressor is provided, with an insight into the impact they have on compressor operation and on overall GT performances. The analysis is focused on the surface fouling of compressor blades and on rotor tip clearances variation.
A modular model is used to simulate the gas turbine operation in design and off-design conditions and the aerodynamic impact of fouling and rotor tip clearances increase is assessed by means of dedicated loss and deviation correlations implemented in the 1D mid-streamline code of the compressor modules.
The two different degradation sources are individually considered and besides the overall GT performance parameters, the analysis includes an evaluation of the compressor degradation impact on the secondary air system.
An Efficient 3D CFD Model for the Analysis of the Flow Field Around Darrieus Rotors
Authors: Torresi Marco , Fortunato Bernardo , Camporeale Sergio Mario 
Published: November 2013

An efficient numerical technique has been developed in order to investigate flow characteristics and global performance of Darrieus rotors. The interest for this kind of vertical axis wind turbines arises from their great capacity for integration within urban areas and for distributed generation.
The proposed methodology is based on the solution of the steady three-dimensional governing equations, by means of a robust commercial CFD code. Since the effect of the turbine blades on the flow field is simulated through the introduction of momentum sources in the porous shell representing the volume swept by the turbine blades, any expensive refinement of the grid, near the rotor, is avoided. This approach dramatically reduces the computational costs, with respect to conventional unsteady flow simulations. The model efficiency enables the simulation of the flow field around Darrieus rotors considering complex and realistic computational domains, for instance when these turbines are clustered within a wind farm or placed inside urban areas.
The methodology is validated by reproducing the performance of the Sandia 17-meter Darrieus rotor with approximate troposkien shape. Comparisons with other codes are also presented in order to highlight the advantages of the proposed method.
Stationary Component Optimization and the Resultant Improvement in the Performance Characteristics of a Radial Compressor Stage
Authors: Fakhri Syed , Sorokes James M. , Vezier Clementine , Pacheco Jorge E. 
Published: November 2013

This paper is a follow-up to work published by Sorokes et al. [16] regarding a diffuser flow-field phenomenon, identified as a precursor to stall in a centrifugal stage. The earlier work provided greater detail on the phenomenon that occurred, including further details on the CFD analyses done to investigate the phenomenon and the trends observed in the test data. The numerical and experimental results described in the earlier work were used as a foundation in developing improved stationary components of another stage of similar design whose surge margin fell short of expectation, with the goal of improving its surge margin and overall performance. The study focused specifically on improving the flow characteristics in the diffuser and return channel by optimizing the geometry. The improvement in surge margin and overall performance was first verified numerically (through CFD analysis) and then experimentally via scale model testing.
The paper will provide an overview of the centrifugal stage that was tested along with a description of the test vehicle, operating conditions and instrumentation used. The paper will also include a description of the numerical work completed; i.e., the CFD code used, computational domain considered and boundary conditions applied. Comparisons of the trends observed in the experimental and numerical work will be offered and the agreement between the numerical and empirical results will be assessed. Finally, performance comparisons of the optimized stage with the previous stage will also be presented.
Mortality following a brain tumour diagnosis in patients with multiple sclerosis
Authors: Montgomery Scott , Hassan Ahmad , Bahmanyar Shahram , Brus Ole , Hussein Oula , Hiyoshi Ayako , Hillert Jan , Olsson Tomas , Fall Katja 
Published: November 2013

ObjectivesAs brain tumours and their treatment may theoretically have a poorer prognosis in inflammatory central nervous system diseases such as multiple sclerosis (MS), all-cause mortality following a brain tumour diagnosis was compared between patients with and without MS. The potential role of age at tumour diagnosis was also examined.SettingHospital inpatients in Sweden with assessment of mortality in hospital or following discharge.ParticipantsSwedish national registers identified 20 543 patients with an MS diagnosis (1969–2005) and they were matched individually to produce a comparison cohort of 204 163 members of the general population without MS. Everyone with a primary brain tumour diagnosis was selected for this study: 111 with MS and 907 without MS.Primary and secondary outcome measures5-year mortality risk following brain tumour diagnosis and age at brain tumour diagnosis.ResultsA non-statistically significant lower mortality risk among patients with MS (lower for those with tumours of high-grade and uncertain-grade malignancy and no notable difference for low-grade tumours) produced an unadjusted HR (and 95% CI) of 0.75 (0.56 to 1.02). After adjustment for age at diagnosis, grade of malignancy, sex, region of residence and socioeconomic index, the HR is 0.91 (0.67–1.24). The change in estimate was largely due to adjustment for age at brain tumour diagnosis, as patients with MS were on average 4.7 years younger at brain tumour diagnosis than those in the comparison cohort (p<0.001).ConclusionsYounger age at tumour diagnosis may contribute to mortality reduction in those with high-grade and uncertain-grade brain tumours. Survival following a brain tumour is not worse in patients with MS; even after age at brain tumour diagnosis and grade of malignancy are taken into account.