bluuebunny/crossref_metadata_2025 huggingface dataset:
The health implications of low hemoglobin deferral in infrequent blood donors
Authors: Annen Kyle , Delaney Meghan , Leitch Dave , Mast Alan E.
Published: August 2014

Background

The causes of anemia in infrequent blood donors deferred for low hemoglobin (Hb) are not well known. We sought to assess this via surveys of infrequent, nonmenstruating deferred blood donors at two institutions, BloodCenter of Wisconsin and Puget Sound Blood Center.

Study Design and Methods

Men at least 18 years of age and women at least 50 years of age who were deferred for low Hb (≤12.5 g/dL), had not more than one donation in the year prior to deferral, and did not successfully donate in the 3 months after their deferral were surveyed.

Results

The total response rate was 380 donors or 34% of those contacted. Of the respondents, 141 had sought medical advice about their low Hb. Of these, 90 were confirmed to have anemia and 13 reported serious disease requiring medical intervention, including mantle cell lymphoma, multiple myeloma, and gastrointestinal bleeding.

Conclusions

A small but concerning number of infrequent blood donors deferred for low Hb have an underlying illness that is severe and would benefit from medical attention. Donors deferred for low Hb who have a high risk for serious underlying illness should be provided targeted educational information advising them to seek additional medical care.
A Probabilistic Approach to Aeropropulsion System Assessment
Authors: Tong Michael T.
Published: August 2014

A probabilistic approach is described for aeropropulsion system assessment. To demonstrate this approach, the technical performance of a wave rotor-enhanced gas turbine engine (i.e. engine net thrust, specific fuel consumption, and engine weight) is assessed. The assessment accounts for the uncertainties in component efficiencies/flows and mechanical design variables, using probability distributions. The results are presented in the form of cumulative distribution functions (CDFs) and sensitivity analyses, and are compared with those from the traditional deterministic approach. The comparison shows that the probabilistic approach provides a more realistic and systematic way to assess an aeropropulsion system.
The Use of Variable Fidelity Models in the Optimization Problems for Aircraft Engines Parameters and Control Laws
Authors: Egorov I. N. , Kretinin G. V. , Leshchenko I. A. , Babiy Y. I.
Published: August 2014

The typical situation when solving a problem of an aircraft engine optimization is that a researcher has several tools for effectiveness indices analysis, distinguished according to the levels of complexity and accuracy. The high-fidelity tools can be the detailed nonlinear mathematical models or even the experimental samples of the engine or its components. However the implementation of optimization researches using such a tools is associated with the significant time expenditures. The low-fidelity models also allow us to carry out optimization search, but the validity of the obtained results can be rather low. Therefore the methods based on a combination of various levels of the analysis tools are going to be used in the field of optimization of the aircraft engines parameters and control laws.

The given paper introduces the multicriteria optimization procedure for aircraft power plants and their components. The procedure is based upon the adaptive use of different levels analysis tools. The proposed approach is intended to minimize the complicated analysis tools application. It uses the method of indirect optimization on the base of self-organization, which permits to find numerically the Pareto-optimal set of solutions, uniformly distributed in the criteria space.

The effectiveness of the proposed optimization procedure is demonstrated by two examples. The first one is a problem to find the optimal control laws for the power plant of short take-off and vertical landing aircraft for its take-off (50 variables, 2 criteria). The second one is the problem of multistage axial compressor optimization aimed at its efficiency maximization (42 variables, 2 criteria).
Implementation of a Compressor Face Boundary Condition Based on Small Disturbances
Authors: Slater John W. , Paynter Gerald C.
Published: August 2014

A compressor-face boundary condition that models the unsteady interactions of acoustic and convective velocity disturbances with a compressor has been implemented into a three-dimensional computational fluid dynamics code. Locally one-dimensional characteristics along with a small-disturbance model are used to compute the acoustic response as a function of the local stagger angle and the strength and direction of the disturbance. Simulations of the inviscid flow in a straight duct, a duct coupled to a compressor, and a supersonic inlet demonstrate the behavior of the boundary condition in relation to existing boundary conditions. Comparisons with experimental data show a large improvement in accuracy over existing boundary conditions in the ability to predict the reflected disturbance from the interaction of an acoustic disturbance with a compressor.
A New Compressor Map Scaling Procedure for Preliminary Conceptional Design of Gas Turbines
Authors: Kurzke Joachim , Riegler Claus
Published: August 2014

In the preliminary conceptional design phase of any new gas turbine project the design and off-design performance of many alternative configurations and cycles must be studied. The simulation results for the off-design cases depend very much on the component maps employed in the model. Especially important are the compressor maps, and when the pre-design study covers a wide range in pressure ratio, then the use of a consistent set of maps is essential for high quality simulation results.

A statistical analysis of many compressor maps — taken from open literature and from the MTU in house data bank — was performed. In each map a reference point was defined which was employed to normalize it. Then, the topology of the normalized map was captured with three characteristic numbers that describe 1) the region where efficiency is highest, 2) the mass flow – speed relationship and 3) the shape of the speed lines.

The characteristic numbers show in the statistic evaluation clear trends with reference pressure ratio. From these trends a new map scaling procedure was derived which describes the systematic change of the compressor map topology with design pressure ratio much better than the conventional map scaling method, which applies constant factors on pressure ratio or on specific work.
A. R. Howell — Father of the British Axial Compressor
Authors: Dunham John
Published: August 2014

The history of Sir Frank Whittle’s invention of the jet engine is well known. Somewhat less well known is that the Royal Aircraft Establishment embarked in 1926 on developing the gas turbine as a way of driving a propeller. In 1938, A.R.Howell joined the team as a new graduate, and by 1944 he had played a major role in evolving successful axial compressor design methods, which were used in the first two generations of UK gas turbine engines. He was appointed Head of Aerodynamics Department in the National Gas Turbine Establishment when it was created in 1946, and led that team for twenty years. For many years he was a key figure in compressor design in the UK. He returned to personal research before retiring in 1980, and he died in 1988. This paper summarises his personal research contributions and some of the pioneering research he led in NGTE.
Steady Performance Measurements of a Turbofan Engine With Inlet Distortions Containing Co- and Counter-Rotating Swirl From an Intake Diffuser for Hypersonic Flight
Authors: Schmid Norbert R. , Leinhos Dirk C. , Fottner Leonhard
Published: August 2014

The influence of distorted inlet flow on the steady and unsteady performance of a turbofan engine which is a component of an airbreathing combined propulsion system for a hypersonic transport aircraft is reported in this paper. The performance and stability of this propulsion system depends on the behavior of the turbofan engine. The complex shape of the intake duct causes inhomogeneous flow at the engine inlet plane, where total pressure and swirl distortions are present. The S-bend intakes are installed axisymmetrically left and right into the hypersonic aircraft hence generating axisymmetrical mirror inverted flow patterns. Since all turbo engines of the propulsion system have the same direction of rotation, one distortion corresponds to a co-rotating swirl at the low pressure compressor (LPC) inlet while the mirror inverted image counterpart represents a counter-rotating swirl. Therefore the influence of the distortions on the performance and stability of the ‘CO’ and ‘COUNTER’ rotating turbo engine are differing, respectively. Both distortions were generated separately by an appropriate simulator at the inlet plane of a LARZAC 04 engine. The results of low frequency measurements at different engine planes yield the relative variations of thrust and specific fuel consumption and hence the steady engine performance.

High frequency measurements were used to investigate the different influence of CO and COUNTER inlet distortions on the development of LPC instabilities.
The Potential Impact of Utilizing Advanced Engine Technology for a Combat Capable Unmanned Air Vehicle (UAV)
Authors: Bruening Greg B. , Snyder James R. , Fredette Raymond E.
Published: August 2014

This paper evaluates the potential impact of utilizing advanced engine technology for a limited life, combat capable, unmanned air vehicle (UAV) application. A study was conducted to define payoffs in terms of mission capability and system level life cycle costs (LCC) associated with implementing three different engine development approaches into a combat capable UAV design. The three different approaches considered were: a new, advanced technology engine; an existing (off-the-shelf) engine; and a derivative of an existing engine with limited technology insertion. A detailed vehicle configuration design was developed to conduct this assessment, including a low observable (LO), highly integrated engine/airframe layout for survivability and mission adaptable considerations. The vehicle is designed with multi-role mission capability such as suppression of enemy air defense (SEAD), close air support (CAS), and battlefield air interdiction (BAI). A system level performance comparison is assessed with the three different engine approaches, specifically for the SEAD-type mission. For the cost analysis, the multi-role mission capability is reflected in the overall assumptions such as in the number of aircraft needed to meet the mission requirements.

A system level assessment such as in this study is essential in determining whether the additional costs associated with the development of a new, advanced engine is worth the investment. The results of this study suggest that advanced engine technology insertion can provide significant benefits in terms of mission range capability, vehicle weight/size, and overall life cycle costs versus an existing engine.
Thermodynamic Performance Analysis and Economic Evaluation of Externally Fired Gas Turbine Cycles for Small Scale Biomass Cogeneration
Authors: Anheden Marie , Martin Andrew R.
Published: August 2014

Externally fired gas turbine (EFGT) cycles in combination with a biomass-fueled, atmospheric circulating fluidized bed (CFB) furnace are investigated for small scale production of power and district heat. Both closed and open gas turbine cycle configurations are considered. The thermodynamic performance analysis includes an evaluation of cycle-to-furnace heat matching and cycle-side pressure loss considerations. An economic analysis is presented for the various EFGT configurations, and comparisons are made with existing and emerging alternatives for small-scale biomass cogeneration. Simulation results show that thermodynamic performance varies between the different configurations and working fluids, with electric efficiencies in the range of 31–38% (LHV) and total efficiencies of 86–106% (LHV). An economic evaluation for an 8 MWf plant shows that the specific capital cost is about 3200–3900 $/kWe for a first commercial plant. The turbomachinery and the CFB furnace dominate the total plant cost, with each contributing about 1/3 of the total installed equipment cost. The cost of electricity, COE, is estimated to be 73–84 $/MWhe for 4 000 full load hours per year in a cogeneration application.
Concepts for the Production of Biomass Derived Fuel Gases for Gas Turbine Applications
Authors: Schmitz W. , Hein D.
Published: August 2014

Amongst the available alternatives of regenerative energy sources, biomass may play an important role in the future. Biomass represents stored solar energy, accessible whenever there is demand. But so far, its large potential has only been used to a small extent. This is partly due to the fact that solid biomass is a common fuel for the production of heat, but is hardly used in combined heat and power (CHP) plants.

For the conversion of solid fuels, combustion in combination with a Rankine cycle is the only well established technology available today, thus acceptable net efficiencies (> 25% LHV) are only possible in complex, rather large scale plants.

However, since the occurrence of biomass differs depending on region and season, and because of its low energy density and thus reduced transportability, biomass is particularly suited for decentralized applications, i.e. for the generation of heat and power (1) in the small power range.

This paper discusses strategies for the integration of biomass gasification / pyrolysis and gas cleaning processes into different gas turbine schemes. Rather than reviewing all possible aspects of and concepts for the usage of biomass in gas turbine applications, this paper evaluates some key aspects (pressurization, tar removal, gas cleaning, choice of gas turbine cycle) of directly fired gas turbine concepts with regard to small scale applications.

The paper shows that tar is a key problem. Especially for small scale applications solutions based on the combustion of tars, like pressurized biomass conversion in combination with hot gas cleaning, prove to be simple and efficient.

This paper also compares the characteristics of integrated gasification cycles, e.g. by demonstrating difficulties connected with the integration of steam blown allothermal gasification (reforming). Furthermore, it is shown that recuperated gas turbines are well suited for highly efficient, yet simple small scale applications.

Test results indicate that “mild” pyrolysis is an alternative technology for the production of comparatively clean medium heating value gases. Integrating the use of pyrolysis gas and charcoal into a simple gas turbine plant, however, can not easily be achieved.
Performance of a Biomass Integrated Gasification Combined Cycle CHP Plant Supplying Heat to a District Heating Network
Authors: Harvey Simon
Published: August 2014

This paper examines a Biomass Integrated Gasification Combined Cycle (BIGCC) CHP plant using atmospheric air-blown gasification with wet cold gas clean-up and flue gas drying of the biomass feed stream. The plant provides heat and power to a medium sized municipality. The paper presents simulated performance results obtained using GateCycle software, and also presents results for the associated economy and CO2 emissions of the district heating system. The computed production costs of the cogenerated electricity are uncompetitively high, given current conditions in Sweden. In order to become competitive, international consensus must be reached on the level of economic advantage to be attributed to the “green” electric power produced by such a plant. However, likely price incentives for “green” power will probably be insufficient for BIGCC-CHP plants to become economically attractive. Therefore further effort is needed to improve the technology, reduce the investment costs, and identify options for longer annual operating times than those usually adopted for CHP plants coupled to district heating plants.
Designing Diagnostic Expert Systems for Long-Term Supportability
Authors: Forsyth Graham , Delaney John
Published: August 2014

In the late 1980s, the Royal Australian Air Force (RAAF) investigated the use of computer-based technology to improve diagnostic troubleshooting methods. One such technology was demonstrated in an Interactive Fault Diagnosis and Isolation System (IFDIS) that was produced by Competitive Advantage Technology Pty Ltd under direction from the Defence Science and Technology Organisation (DSTO).

This paper describes a new design which aims to improve the long-term supportability of such diagnostic systems by making the maximum use of commercial software, producing clear separation of technical information from any software elements, writing all non-standard software using defined standards and generally making the most possible use of the advances in computing over the last ten years.

The system is now in field trial with the aim of developing procedures and specifications for production.
An Investigation of Artificial Neural Network (ANN) in Quantitative Fault Diagnosis for Turbofan Engine
Authors: Bin Sun , Jin Zhang , Shaoji Zhang
Published: August 2014

This paper is aimed at investigating two kinds of Artificial Neural Network (ANN) applied to quantitative fault diagnosis of turbofan engine gas path components. Among them, one is Back Propagation neural Network (BPN) and the other is Adaptive Probabilistic Neural Network (APNN).

Using BPN in order to achieve quantitative fault diagnosis, number of training samples will increase greatly which may lead to the difficulty of iteration convergence. A new learning rule named hybrid rule is introduced to avoid the algorithm falling into static areas and expedite convergence.

Recently, a new method to improve the adaptability of multi-layer feed-forward neural network has been developed by the application of Radial Basis Function (RBF). In this paper, the APNN is put forward based on the theory of radial basis function, Bayesian estimation and normal distribution hypothesis of information. It is proposed that the adaptability of APNN can be obtained by applying maximum-likelihood estimation of the output of test case based on a posteriori probability of its input.

The investigation shows that BPN and APNN have their own advantages and disadvantages. BPN has faster diagnostic speed and fits the requirement of quantitative diagnosis for single fault. APNN is more adaptive and fit better to quantitative diagnosis for multiple faults.
Neural Networks Based Diagnostics for Mistuned Bladed Disk
Authors: Peng Pei-Yuan , Yang M. T.
Published: August 2014

Neural networks based diagnostics is studied in this paper for the fault/alert assessment of the mistuned bladed disk. By randomly varying the blades frequencies (± 2% of the nominal frequencies), we experimentally collected 1000 sets of data. Each set of data is composed of blade frequencies, maximal vibrating magnitude for each blade with the corresponding frequency. The goal is to investigate the mapping relationship from the blade property (blade frequency) to maximal vibrating displacement and the corresponding frequency.

Assuming the system is forced by a traveling excitation, the vibration/frequency signature is derived. The challenging part stems from mistuned bladed disk system, where every blade performs differently for the same input excitement. The neural networks based diagnostics system demonstrate its capability to identify the mapping relation for this complex system.

The simulation is based on a finite element model of bladed disk system and the results exhibit the effectiveness of the proposed algorithm.
Performance of Gas Turbine Power Plants Controlled by One Step Ahead Adaptive Technique
Authors: Dambrosio L. , Camporeale S. M. , Fortunato B.
Published: August 2014

The One Step Ahead Controllers represent a branch of the Minimum Prediction Error Adaptive Controllers. They combine the parameter estimation of the controlled system model with a particular control scheme; therefore, they are especially suitable for non-linear and time-varying systems. Since the estimated parameters are updated at each time step (by using the sampled data), these methods can be adopted for real-time applications. Consequently, the One Step Ahead Controllers do not require the knowledge of the dynamic characteristics of the controlled system (e.g. state space systems or transfer functions).

The One Step Ahead Adaptive (OSAA) algorithm combines the Least Square Algorithm (LSA) parameter estimator with a Deterministic Auto-Regressive Moving Average (DARMA) control scheme. The DARMA model can be characterized with a different number of time steps in the past (order of the estimated model) in relation to the dynamic feature of the controlled system.

Sometimes, an excessive control effort could arise, caused by sudden variations of the electric load. In order to reduce this control action, the OSAA control technique has been applied also in Weighted fashion. The Weighted One Step Ahead Adaptive (WOSAA) control algorithm considers a penalty associated with the control effort by use an appropriate cost function. In this way, the control variable does not assume too large values, even when the Gas Turbine undergoes sudden changes in the external load. As a consequence, the robustness and the stability features of the WOSAA control system are increased with respect to the OSAA algorithm.

The proposed techniques have been applied to a single shaft heavy-duty gas turbine (WOSAA) and to a double-shaft aero-derivative gas turbine (OSAA). They have been tested in Single-Input Single Output (SISO) mode. In the simulation tests, the plant is assumed to undergo sudden variations of the electric load. Second order schemes of the OSAA estimated model have been derived and applied to the double-shaft aero-derivative gas turbine.

The results show that the OSAA control technique, applied to the double-shaft aero-derivative gas turbine, effectively counteracts the load reduction with limited overshoot in the controlled variables and, introducing an integral correction, with a negligible static error. On the other hand, the WOSAA control algorithm is able to efficiently regulate the single shaft heavy-duty gas turbine, and to counteract the sudden variations of the electric load, with reduced control effort.
Advanced Fuel Metering for Aero Engines
Authors: Schwamm Friedrich
Published: August 2014

Traditionally the fuel system of most modern day aero engines consist of two basic functional blocks;

- pumping system

- fuel metering system.

The pumping system basically consists of a first stage centrifugal pump followed by a second stage gear pump. The function of the pumping system is to provide sufficient fuel at the required pressure to ensure engine operation (steady state and transient) over the complete operating envelope and under the consideration of worst case fuel inlet properties.

The fuel metering system basically consists of a fuel metering valve, an emergency valve and a shut off valve. The fuel metering valve itself is usually realised as controllable main metering valve, the pressure drop across which is hydro-mechanically controlled via a pressure drop regulator. The pressure drop regulator spills the excess fuel delivery back to the pump inlet in order to maintain the constant pressure drop. Whilst this approach to fuel system design has gained world wide industry acceptance, there still remains potential for further simplification and improved system reliability. This paper examines two alternative concepts for future fuel system designs namely,

- Electrically controlled variable speed fuel pump

- Reduced complexity fuel metering unit.

For both systems this paper examines and discusses, the technologies involved and the relative merits of each system in terms of:

• system performance

• fault detection / accommodation

• failure reaction and

• production costs.
Design and Test of a Semi-Passive Flow Control Device for Inlet Distortion Suppression
Authors: Jaw Link C. , Cousins William T. , Wu Dong N. , Bryg David J.
Published: August 2014

Advanced turbine engines often operate with reduced stability margin to increase performance. Aircraft engine temperature and pressure inlet distortion has a major effect upon the stability of the compression system. Suppression of inlet distortion can provide greater stability margin for the engine, thereby reducing operability restrictions on the engine by allowing closer operation to the stability limit.

SMI has designed and tested a semi-passive distortion suppression system. The system uses flow injection to modify temperature and pressure inlet distortion. The prototype system was tested on a Honeywell T55 compressor rig.

This paper presents both the design of the system and the test results. The test results show that this semi-passive distortion suppression system was able to reduce the surge margin degradation caused by the presence of pressure or temperature distortion. Special design considerations for this type of system are discussed, based upon the results of the prototype test. It is shown that distortion control can be a viable addition to the design of an aircraft engine.
Experimental Investigation of the Blade-to-Blade Flow in a Compressor Rotor by Digital Particle Image Velocimetry
Authors: Balzani N. , Scarano F. , Riethmuller M. L. , Breugelmans F. A. E.
Published: August 2014

The purpose of this study is to investigate the blade to blade flow in an axial compressor, providing a detailed description of the entire flow-field on multiple layers through the use of Particle Image Velocimetry (PIV).

Typical problems that relate to flow seeding, light-sheet generation and camera-laser timing control are successfully dealt with bringing additional knowledge in the domain.

An extensive data set is analysed to obtain statistical flow information (mean and fluctuating quantities). Spatial data reconstruction procedures allow the complete planar flow distributions to be determined. The multi-planar mean velocity field constitutes the final result of a 3D reconstruction of the domain geometry and the proper introduction of the available planar measurements.
Ceramic Stationary Gas Turbine Development Program — Seventh Annual Summary
Authors: Price Jeffrey , Jimenez Oscar , Parthasarathy Vijay , Miriyala Narendernath , Leroux Don
Published: August 2014

The Ceramic Stationary Gas Turbine (CSGT) program is being performed under the sponsorship of the United States Department of Energy, Office of Industrial Technologies. The objective of the program is to improve the performance of stationary gas turbines in cogeneration by retrofitting uncooled ceramic components into the hot section of the engine. The replacement of previously cooled metallic hot section components with the uncooled ceramics enables improved thermal efficiency, increased output power, and reduced gas turbine emissions. This review summarizes the progress on Phase III of the program, which involves field testing of the ceramic components at cogeneration end user sites.

The Solar Centaur 50S engine, which operates a turbine rotor inlet temperature (TRIT) of 1010°C (1850°F), was selected for the developmental program. The program goals include an increase in the TRIT to 1121°C (2050°F), accompanied by increases in thermal efficiency and output power. This will be accomplished by the incorporation of ceramic first stage blades and nozzles, and a “hot wall” ceramic combustor liner. The performance improvements are attributable to the increase in TRIT and the reduction in cooling air requirements for the ceramic parts. The “hot wall” ceramic liners also enable a reduction in gas turbine emissions of NOx and CO.

The component design and material selection have been definitized for the ceramic blades, nozzles and combustor liners. Each of these ceramic component designs was successfully tested in short term engine tests in the Centaur 50S engine test cell facility at Solar. Based on their performance in a 100 hour cyclic in-house engine test, the ceramic components were approved for field testing. Oxidation of the ceramic components in the gas turbine environment dictated the need for environmental barrier coatings, which were optimized under the program. To date, six field installations of the CSGT Centaur 50S engine totaling over 14,000 hours of operation have been initiated under the program at two industrial cogeneration sites. An 8000 hour field demonstration of a low emission ceramic combustion system was initiated in August 1999. This paper briefly discusses the recent developmental efforts for the ceramic components, but focuses on the various field demonstrations.
Infrared Measurements of Thermoacoustic Instabilities in a Swirl-Stabilized Combustor
Authors: Allgood D. , Murugappan S. , Acharya S. , Gutmark E.
Published: August 2014

An experimental study of the pressure and heat release dynamics associated with thermoacoustic instabilities was performed on a 30kW model gas turbine combustor. The combustor consists of an annular swirling air stream with a centrally located Parker Hannifin Research Simplex Atomizer that injects liquid fuel (ethanol) into a dump combustion chamber. An infrared (IR) imaging system has been implemented to visualize the spatial and temporal dynamics of the heat release within the combustor in order to study the effects of active control strategies on suppressing the instabilities. The infrared measurements were acquired in conjunction with heat flux and pressure measurements obtained from high frequency response transducers to investigate the coupling between the heat release and acoustic fields. Time averaged IR emissions show stronger gradients and higher average heat release near the base of the flame with closed-loop control. The results also showed that flow conditions corresponding to higher pressure oscillations in the combustor were characterized by strongly fluctuating compact regions of heat release near the base of the flame.
NOx Scaling Characteristics for Industrial Gas Turbine Fuel Injectors
Authors: Kendrick Donald W. , Bhargava Anuj , Colket Meredith B. , Sowa William A. , Maloney Daniel J. , Casleton Kent H.
Published: August 2014

An experimental and numerical investigation into the effects of nozzle scale was undertaken at the U.S. Federal Energy Technology Center in conjunction with the United Technologies Research Center. Experiments were conducted at operating pressures from 6.8 to 27.2 atm., and at primary zone equivalence ratios from 0.4 to 0.75. Results reported herein summarize tests at 6.8 atm., and with zero and 4% piloting levels (expressed as mass fractions of total fuel). Computations used to compare to the experimental data were made using the GRI Mech 2.11 kinetics and thermodynamics database for flame chemistry modeling. A perfectly stirred reactor network (PSR) was used to create a network of PSRs to simulate the flame. From these investigations, concentrations of NOx and CO expressed in parts per million (ppm) were seen to increase and remain virtually unchanged, respectively, when comparing a Quarter to Full Scale Bluff-Body (Tangential Entry) nozzle. Simple heat transfer modeling and CO emissions refuted that any variations in thermal characteristics within the combustors were solely responsible for the observed NOx variations. Using PSR network modeling, the NOx trends were explained due to variations in macroscopic mixing scales which increased with nozzle size, thereby creating progressively less uniform mixing, and hence higher NOx levels.
Rapid Non-Intrusive Gas Turbine Exhaust Temperature Measurement
Authors: Welch Michael. A. , Hilton Moira , Wilson Chris W.
Published: August 2014

An integrated data collection and rapid analysis system was developed which produces temperature maps of gas turbine efflux using Fourier Transform Infrared (FTIR) spectroscopy. The system is purely passive, collecting the infrared radiation from the hot plume gases and requiring no contact with the plume or additional source of infrared radiation. A remotely controlled infrared beam steering mechanism traverses in 2 dimensions, parallel to the direction of exhaust gas flow, positioning the line of sight of a FTIR spectrometer across the plume. Project-specific software integrates the collection of infrared spectra by the FTIR spectrometer (interfacing with the commercial spectrometer software) and analysis of the data utilising a single PC. The plume gas temperatures are calculated by comparison of specific CO2 bands with the radiance of a black body source.
Experimental and Theoretical Studies of a Novel Venturi LPP Combustor
Authors: Røkke Nils A. , Wilson Andrew J. W.
Published: August 2014

A new gas turbine engine using a unique layout patented in Norway has a low emission combustion system under development. The gas generator uses entirely radial rotating components and employs a dual entry LP radial compressor, a radial HP compressor and a radial HP turbine. The power turbine is of a two stage axial design, coupled to an epicyclical gear embedded in the exhaust duct.

Several combustor concepts have been tested and evaluated during the development of the engine. The engine is targeted for marine, power generation and train propulsion. For the marine and train application liquid fuel operation is needed, thus the primary focus in the development has been for a lean premixed prevapourised system.

An interesting concept utilising two venturi premixers has been studied intensively. By utilising venturi premixers the following advantages can be achieved:

• Low overall pressure drop but high injector pressure drop and velocities in the mixing region (throat region)

• High shear forces and drag imposed on the droplets enhancing droplet shedding and evaporation

• Excellent emission behaviour at designated load conditions

Although these advantages can benefit gas turbine low emission combustion the challenges in using venturi premixers are:

• Venturis are susceptible to separation and thus flame stabilisation within the venturi which is detrimental

• Inlet flow disturbances enhance the tendency for separation in the venturis and must be minimised

Studies were launched to investigate a proposed combustor configuration. These studies included analytical studies, Computational Fluid Dynamics (CFD) calculations of isothermal and combusting flow inside the combustor together with rig tests at atmospheric, medium and full pressure. Finally engine tests within the full operating range were conducted with very favourable emission figures for Lean Premixed Prevapourised (LPP) operation. The system was capable of running at below 20 ppm Nox and CO, at elevated power for liquid fuel. Control of part load performance and emissions is by variable fuel staging of the two venturi stages. The paper highlights the features of the venturi combustor development and discusses the characteristics in terms of flow conditions and droplet motion, heat transfer, ignition delay time and emissions.
Improvement of Aerodynamic Performance of a Combustor Dump Diffuser Using Inclined Walls
Authors: Honami Shinji , Yamazaki Eiichi , Shizawa Takaaki
Published: August 2014

The combustor diffuser with the deep flame dome in the recent engine results in the large total pressure loss. It is important to obtain both better aerodynamic performance by reduction of total pressure loss and reduced NOx in the exhaust from the combustor, regardless of the inlet flow conditions such as inlet distortion. Installation of an inclined wall within the combustor dump diffuser is suggested in order to improve the aerodynamic performance. A cold flow experiment using Pitot probe surveys in a model of a combustor diffuser shows that the inclined wall is effective in improvement of the total pressure loss, even if the velocity profile at the diffuser inlet is distorted. Furthermore, the flow rate distributions into the branched channels are also improved. The flow mechanism in the inclined wall configuration is clarified from the measurements of the mean velocity and turbulent Reynolds stress by a Laser Doppler Velocimetry (LDV) system.
Application of Macrolamination Technology to Lean, Premix Combustion
Authors: Mansour Adel , Benjamin Michael , Straub Douglas L. , Richards Geo. A.
Published: August 2014

Macrolamination, a novel manufacturing technique, is used to develop a dual-fuel premixer. A spatially distributed injection strategy is used to enhance fuel placement, distribution, and mixing inside the premixer. Parametric studies are conducted with different configurations of the premixer to determine the effects of residence time and nozzle configuration on pollutant emissions and flame stability. Diesel fuel (DF-2) and natural gas are used as fuels. Tests are conducted at a pressure of 400 kPa (5 atmospheres), and an inlet-air temperature of 533°K. The pollutant emissions and RMS pressure levels are presented for a relatively wide range of nozzle velocities (50–80 m/s) and equivalence ratios (0.54–0.75). These results indicate very good pollutant emissions for a prototype design. These results also indicate that the time-lag model, previously associated with combustion oscillations for gaseous-fuel applications, also applies to liquid-fuel operation.
Flow Structures of a Radial-Inlet Swirler
Authors: Ma Zhanhua , Wang Dexin , Jeng San-Mou , Benjamin Michael A.
Published: August 2014

The upstream and downstream flows of a radial inlet swirler were investigated by using a 2-D Laser Doppler Velocimetry (LDV) probe. The radial profiles of axial and tangential velocities at various axial locations were obtained. The effects of Reynolds Number, swirler exit configuration and combustor outlet condition were examined. The results reveal that the combustor outlet condition has strong influence on the downstream flow field of the swirler. The effect of Reynolds Number depends on the swirler exit configurations. The influence of the convergent configuration from swirl chamber to orifice on the flow fields is very small whereas the influence of the divergence at the swirler exit is significant. The upstream and downstream flows of the radial inlet swirler are of sub-critical nature, thus the swirler exit configuration and combustor outlet condition significantly affect the flow fields.
Design of a Jet-Stirred Gas Generator for Studies of High Temperature Mixing and Combustion
Authors: Fotache C. G. , Hautman D. J. , Rosfjord T. J.
Published: August 2014

A high-temperature Jet-Stirred Gas Generator (JSGG) has been designed to investigate the characteristics of combustion in the mixing layer between a flow of air and a mainstream flow of rich combustion products. The design goal is delivery of a near-equilibrium, spatially-uniform flow of combustion products for a range of Mach numbers in the test section between 0.1–0.7, pressures of 1–10 atm, and equivalence ratios of 0.5–2.0. In this paper we describe the reactor design, as well as the numerical and experimental evaluation of its operation. The FLUENT turbulent flow code was used together with a reduced chemical kinetic model for propane-air oxidation to verify the attainment of well-mixed, near-equilibrium conditions. Experiments were performed using flow sampling at the inlet of the test section by means of an optimized aerodynamic-quench probe. Both the experiments and the calculated results indicate achievement of the design goals.
CFD Analysis of a Complete Industrial Lean Premixed Gas Turbine Combustor
Authors: Birkby P. , Cant R. S. , Dawes W. N. , Demargne A. A. J. , Dhanasekaran P. C. , Kellar W. P. , Rycroft N. C. , Savill A. M. , Eggels R. L. G. M. , Jennions I. K.
Published: August 2014

The introduction of lean premixed combustion technology in industrial gas turbines has led to a number of interesting technical issues. Lean premixed combustors are especially prone to acoustically-coupled combustion oscillations as well as to other problems of flame stability such as flashback. Clearly it is very important to understand the physics that lies behind such behaviour in order to produce robust and comprehensive remedies, and also to underpin the future development of new combustor designs. Simulation of the flow and combustion using Computational Fluid Dynamics (CFD) offers an attractive way forward, provided that the modelling of turbulence and combustion is adequate and that the technique is applicable to real industrial combustor geometries. The paper presents a series of CFD simulations of the Rolls-Royce Trent industrial combustor carried out using the McNEWT unstructured code. The entire combustion chamber geometry is represented including the premixing ducts, the fuel injectors and the discharge nozzle. A modified k-ε model has been used together with an advanced laminar flamelet combustion model that is sensitive to variations in fuel-air mixture stoichiometry. Detailed results have been obtained for the non-reacting flow field, for the mixing of fuel and air and for the combustion process itself at a number of different operating conditions. The study has provided a great deal of useful information on the operation of the combustor and has demonstrated the value of CFD-based combustion analysis in an industrial context.
Computation of 3D Turbulent Not-Premixed Reacting Flows Using an Implicit Unstructured Solver
Authors: Adami P. , Martelli F.
Published: August 2014

A 3D CFD simulation of turbulent reactive flows is discussed. The original compressible version of the solver HybFlow designed for turbine rows investigation is here applied for low speed burning flow. A conserved scalar approach is considered to simulate the turbulent reacting flow field of non-premixed flames. The spatial discretization is based on an upwind finite volume method for unstructured grids using the Roe’s Riemann solver with a non-linear TVD scheme. The steady state solution is computed by means of an implicit relaxed Newton method. The linear solver is GMRES coupled with an ILU(0) preconditioning scheme. The turbulence chemistry interaction is described using a presumed β-PDF Flamelet approach. Two test applications are here presented to verify the methodology characteristics for a pilot-jet turbulent flame and a bluff-body stabilized flame both using CH4. A model combustor supplied with propane is also briefly shown as an example of application to a more realistic configuration.
Thermodynamic Optimization of Reheat Gas Turbine Cycles Combined With Bottoming Cycles
Authors: Shnaid Isaac
Published: August 2014

In this work, thermodynamic optimization of reheat gas turbine cycles (without intercooling and recuperative heat exchange) combined with bottoming cycles, is done. Thermodynamic conditions ensuring the combined cycle engine maximal specific work and thermal efficiency are formulated for a general case of arbitrary number of reheat stages with different inlet gas temperatures and isentropic efficiencies.

Parametric analyses show that application of reheat cycles brings significant improvement of gas turbine and combined cycle specific work and efficiency in comparison with a case of a simple cycle gas turbine.
Comparison of Gas Turbine Cooling With Dry Air, Humidified Air and Steam
Authors: Jordal Kristin , Torisson Tord
Published: August 2014

In order to study the impact of using a gas turbine coolant other than compressed air, a comparison is made among various gas-turbine based power cycles: the simple-cycle gas turbine, the steam injected gas turbine, the combined cycle and the Humid Air Turbine (HAT) cycle. Depending on the cycle configuration, the coolant, which is compared to the air extracted from the compressor, is either steam or humidified air. The study is based on a modern, medium-sized industrial gas turbine (net power output in base configuration: 40 MW), in order to evaluate the possibilities of different redesign options of the cooling system.

It is found that steam cooling is a very efficient method of cooling; whereas, the possible benefits of humid air cooling are mainly obtained through the temperature decrease that is a result of the humidification process. Hence, for the intercooled HAT cycle, the benefit of cooling with humid air is smaller (∼0.2 percentage points increase in thermal efficiency) than for the HAT cycle without intercooler (∼0.5 percentage points increase in thermal efficiency). For the simple cycle, there is an increase in thermal efficiency of 0.8 percentage points when it is cooled with humid air.

A parameter variation shows that with more advanced cooling technologies and heat resistant materials, the benefit of cooling with steam or humid air, instead of with compressed air, is reduced for the HAT and combined cycles.
Dynamic Modelling of the Gasification Island of a Coal-Based IGCC
Authors: Nihart Raoul
Published: August 2014

In developed countries, coal power plants are often used to work in part load and possibly to follow the demand. Consequently, the transient behaviour of these power plants is a very important issue. In integrated coal gasification combined cycles (IGCCs), the complex interactions between the different parts of the plant make the process behaviour difficult to predict.

This paper describes a non-linear simulation model of the gasification island. It comprises mainly a module for the gasifier reactor with water walls, two different ones for the convective and radiant syngas coolers, a raw gas / clean gas heat exchanger and a simple module for the gas treatment. This latter is simplified because it has only a small influence on the transients of the plant given its low inertia. All these modules have been introduced into a dynamic computational tool previously designed to simulate the transients of gas combined cycles (Dechamps, 1995). The computational code, called CCDYN (Combined Cycle DYNamics), is a modular and flexible code, each module being a main component (like a gasifier, a gas turbine, a heat exchanger, …) solving a set of transient equations.

This paper also presents some results and demonstrates the interest of such a modelling. As an example, the gasification island of a coal-based IGCC is modelled in the case of different coal feed properties and the influence on the syngas composition is illustrated. Another example is the evolution with time of the various temperatures in the system during a start-up procedure and a load variation.

The thermochemical and physical properties used in the models are extracted from Barin (1989), from Perry and Green (1984) and from Dechamps (1995).
Life Extension of GT HGP Components by Recycling
Authors: Lee Jung-Ho
Published: August 2014

The life of hot gas path (HGP) components in gas turbine units can be extended through regular recycling. It is important to control the degradation of components under a limiting level by repairing on a regular basis and reusing them by recycling successively. Recycling mechanism of the first stage turbine blades is developed by investigating the characteristics of their typical degradations, repairability criteria, repair techniques, optimum timings of repair and economic evaluation model.