bluuebunny/crossref_metadata_2025 huggingface dataset:
Free Vibration Response of Thin and Thick Nonhomogeneous Shells by Refined One-Dimensional Analysis
Authors: Varello Alberto , Carrera Erasmo
Published: July 2014

The free vibration analysis of thin- and thick-walled layered structures via a refined one-dimensional (1D) approach is addressed in this paper. Carrera unified formulation (CUF) is employed to introduce higher-order 1D models with a variable order of expansion for the displacement unknowns over the cross section. Classical Euler–Bernoulli (EBBM) and Timoshenko (TBM) beam theories are obtained as particular cases. Different kinds of vibrational modes with increasing half-wave numbers are investigated for short and relatively short cylindrical shells with different cross section geometries and laminations. Numerical results of natural frequencies and modal shapes are provided by using the finite element method (FEM), which permits various boundary conditions to be handled with ease. The analyses highlight that the refinement of the displacement field by means of higher-order terms is fundamental especially to capture vibrational modes that require warping and in-plane deformation to be detected. Classical beam models are not able to predict the realistic dynamic behavior of shells. Comparisons with three-dimensional elasticity solutions and solid finite element solutions prove that CUF provides accuracy in the free vibration analysis of even short, nonhomogeneous thin- and thick-walled shell structures, despite its 1D approach. The results clearly show that bending, radial, axial, and also shell lobe-type modes can be accurately evaluated by variable kinematic 1D CUF models with a remarkably lower computational effort compared to solid FE models.
What to Do With CO2
Authors: Green Alex E. S. , Schaefer Greg P.
Published: July 2014

Indirectly heated gas liquid and char converters (IHGLCCs) are employed to investigate several means of using or sequestering CO2. As a gasification agent CO2 is used with IHGLCCs to substantially increase gaseous energy output for a given carbonaceous feedstock. IHGLCCs are also used for mild oxidation of coal and for mild pyrolysis of biomass to produce humate type soil amendments. These soil amendments can indirectly sequester CO2 by enhanced plant growth and the atmospheric scrubbing action of plants (photosynthesis-respiration). Results of attempts to convert coal-biomass blends into an activated charcoal that can scrub CO2 and also become useful soil organic carbon are inconclusive as yet but appear promising. Countries that must import oil or have agriculturally depleted lands need “omnivorous” feedstock converters to upgrade available domestic feedstock into fuels, chemicals and chars that serve their energy, agricultural and other needs. The results of exploratory research directed at applying IHGLCC forms of omnivorous feedstock converters to using or sequestering CO2 are reported. IHGLCC technology should also be useful in mitigating potential global greenhouse problems and CO2 and waste disposal problems on space missions.
Uncertainty Reduction in Gas Turbine Performance Diagnostics by Accounting for Humidity Effects
Authors: Mathioudakis K. , Tsalavoutas A.
Published: July 2014

The paper presents an analysis of the effect of ambient humidity on the performance of industrial gas turbines and examines the impact of humidity on methods used for engine condition assessment and fault diagnostics. First, the way of incorporating the effect of humidity into a computer model of gas turbine performance is described. The model is then used to derive parameters indicative of the “health” of a gas turbine and thus diagnose the presence of deterioration or faults. The impact of humidity magnitude on the values of these health parameters is studied and the uncertainty introduced, if humidity is not taken into account, is assessed. It is shown that the magnitude of the effect of humidity depends on ambient conditions and is more severe for higher ambient temperatures. Data from an industrial gas turbine are presented to demonstrate these effects and to show that if humidity is appropriately taken into account, the uncertainty in the estimation of health parameters is reduced
Advanced Test Cell Diagnostics for Gas Turbine Engines (USAF Automated Jet Engine Test Strategy – AJETS)
Authors: Roemer Michael J. , Kacprzynski Gregory J. , Schoeller Michael , Howe Ron , Friend Richard
Published: July 2014

Improved test cell diagnostics capable of detecting and classifying engine mechanical and performance faults as well as instrumentation problems is critical to reducing engine operating and maintenance costs while optimizing test cell effectiveness. Proven anomaly detection and fault classification techniques utilizing engine Gas Path Analysis (GPA) and statistical/empirical models of structural and performance related engine areas can now be implemented for real-time and post-test diagnostic assessments. Integration and implementation of these proven technologies into existing USAF engine test cells presents a great opportunity to significantly improve existing engine test cell capabilities to better meet today’s challenges.

A suite of advanced diagnostic and troubleshooting tools have recently been developed and implemented for gas turbine engine test cells as part of the Automated Jet Engine Test Strategy (AJETS) program. AJETS is an innovative USAF program for improving existing engine test cells by providing more efficient and advanced monitoring, diagnostic and troubleshooting capabilities. This paper describes the basic design features of the AJETS system; including the associated data network, sensor validation and anomaly detection/diagnostic software that was implemented in both a real-time and post-test analysis mode. These advanced design features of AJETS are currently being evaluated and advanced utilizing data from TF39 test cell installations at Travis AFB and Dover AFB.
ICEMS: Intelligent Condition-Based Engine/Equipment Management System (www.icems.com)
Authors: Jaw Link , Wang Yu-tsung (Jim) , Friend Richard
Published: July 2014

Health management of a machine, such as a gas turbine engine, offers the potential benefits of efficient operations planning and the reduced cost of ownership. It requires a tight integration of major health management functions, such as trending, failure identification, forecasting, life prediction, operations and maintenance planning. This paper introduces a suite of plug-in tools that enhance the condition monitoring and health management capabilities of operational (or legacy) systems. One of these systems is the U. S. Air Force Comprehensive Engine Trending and Diagnostics System (CETADS), which has been used as the baseline for the development of the tools.

These tools are collectively called the Intelligent Condition-based Engine/Equipment Management System (ICEMS). These tools are configured as software modules, which can be incorporated into an operational health management system individually or as a group. ICEMS modules implement the advanced algorithms containing artificial intelligence, statistical, model-based analysis techniques, and RCM practices. Although these modules have been developed and tested using data from the Pratt & Whitney F100-PW-220 engine in service at Luke Air Force Base, the modules are also generalized to cover many generic machines (or equipment).
Simultaneous Short and Long Wavelength Infrared Pyrometer Measurements in a Heavy Duty Gas Turbine
Authors: Markham J. R. , Latvakoski H. M. , Frank S. L. F. , Lüdtke M.
Published: July 2014

Advanced thermal barrier coatings (TBCs) are increasingly being used in high performance turbine engines. For optimized use of the coatings, accurate surface temperature measurements are required in the combustion environment. Current on-engine pyrometers, which use short infrared wavelengths to accurately measure the temperatures of metal surfaces, show increased uncertainties when used on TBCs. Studies have suggested that long infrared wavelengths are a suitable alternative. Therefore, to evaluate the response of both wavelength regions, simultaneous measurements with short and long wavelength infrared pyrometers have been accomplished in the first stage turbine of a Siemens V84.3A 60Hz 180MW engine at the Berlin Gas Turbine Development and Manufacturing Center.
Force Measurements in Magnetic Bearings Using Fiber Optic Strain Gauges
Authors: Raymer Stephen G. , Childs Dara W.
Published: July 2014

A new method for measuring forces in magnetic bearings is presented. Fiber-optic strain gauges (FOSGs) mounted to the side of the magnet poles are used to detect the small levels of strain that the metal experiences as the bearing exerts a force. These strains can be converted into force components, providing measurements with a previously unattainable level of accuracy and precision.

Tests were done using the Magnetic Bearing Test Rig at the Texas A&M University Turbomachinery Laboratory. Two FOSGs were placed approximately 90° apart on two separate poles of one of the bearings, and the strain levels for different load magnitudes and directions were measured. The raw signal has several undesirable attributes that prevent an accurate static measurement. However, dynamic measurements proved to be very effective in the frequency domain, as most of the noise in the signal is confined to frequencies below 1 Hz.

Due to the raw signal characteristics, new techniques for load application and calibration were developed. By using these new approaches, an equation relating reaction force components and strain was generated. This equation provides precise knowledge of any force vector in the bearing. An uncertainty analysis was performed on the resulting equation, providing a measure of resolution and a reduction in error several times more precise than any previous result.

As a result of these findings, magnetic bearings can now be used to perform precise diagnostic analysis, determine rotordynamic coefficients, and improve magnetic bearing design and performance.
Dynamic Response of a Premix Fuel Injector
Authors: Richards Geo. A. , Straub Douglas L. , Robey Edward H.
Published: July 2014

Combustion oscillations (dynamics) have become a major challenge in the development of low-emission premix combustors. Numerous recent papers have considered the various mechanisms that drive oscillations, as well as acoustic features of the combustor and fuel system that participate in sustaining unwanted oscillations. The acoustic transfer matrix technique has been used in a number of recent analyses of both the combustion and fuel injection process. In this paper, the transfer matrix analysis is combined with a reduced order model of the fuel supply to calculate the magnitude and phase of the fuel system response to imposed pressure perturbations. The analysis is used to determine if a variable geometry resonator in the fuel system can be used to adjust the phase and gain of the fuel response to enhance stability. Experimental data recorded in a research premix fuel injector show that the reduced order model accurately describes the dynamic response of the fuel entering the premix passage. Using measured acoustic properties it is also shown that the variable geometry resonator studied here can produce a phase response for fuel delivery over a range of 70 degrees, with appreciable modulation of the main fuel flow. It is suggested that this variable phase response could be used to adjust the stability properties of a given combustor.
Measurement of Dynamic Flame Response in a Lean Premixed Single-Can Combustor
Authors: Straub Douglas L. , Richards Geo. A. , Baumann William T. , Saunders William R.
Published: July 2014

Combustion oscillations are a serious technical challenge for stationary gas turbine manufacturers. In order to address this issue, the development cycle for a gas turbine combustor typically involves an extensive test program. In many cases, the dynamic stability observed in sub-scale test rigs differs from the commercial engines. If encountered late in the development cycle, these rig-to-engine variations can impact an entire engine program. This paper discusses an experimental approach to measure time-scales (i.e., fuel-transport time and flame response time) that play a critical role in combustion oscillations. If these time-scales can be measured throughout the development cycle, the rig-to-engine variations in combustor performance may be improved. The results described in this paper are collected from a nominal 1MWth single-can combustor rig operating on natural gas. The inlet-air temperature and pressure are 589K (600°F) and 760 kPa (7.5 atm), respectively. The measured time-scales are significantly larger than the bulk fuel-transport time calculated from simple estimates. In order to explain these discrepancies, a simple flame model is presented to show how the flame structure can influence these time-scales. This model is also used to illustrate how these critical time-scales can change as a function of operating condition.
Improved Combustion Mixture Control Using a Novel Fuel Injector
Authors: Brundish K. D. , Wilson C. W.
Published: July 2014

A fuel injector has been designed with the capacity to change effective area and fuel placement by varying the swirl number. This gives more flexibility on fuel/air mixture control than current designs, allowing a potentially wide turndown to be achieved whilst maintaining low emissions at high power. The fuel injector utilises fluidic control, eliminating the need for mechanical moving parts in the hot region commonly found in current variable geometry fuel injector designs.

The concept was evaluated and showed promising improvement in stability compared to the baseline fuel injector. The control flow system, using fluidics, was developed in isolation. The concept and control systems were then combined and evaluated. Although variable swirl using fluidic control was achieved, it was not sufficiently optimised to separate the downstream outer and inner airflow as with the concept design. As such the observed improvement in stability was not as good as expected. However, the ability to control effective area, and fuel placement without the need for moving parts was proven.

It is therefore recommended that further work be performed to allow the optimisation of the device such that controllable improvements in stability performance can be achieved in line with the potential shown with concept testing.
Modulation of a Liquid-Fuel Jet in an Unsteady Cross-Flow
Authors: Anderson Torger J. , Proscia William , Cohen Jeffrey M.
Published: July 2014

This paper describes an experimental study of a fuel jet in an unsteady cross flow as part of a program to evaluate active control of combustion instabilities that involve acoustic / spray coupling.

The results provide insights into the different physical mechanisms through which the jet and cross flow interact and the degree to which acoustic velocity fluctuations modulate liquid jet mixing, penetration and spray distribution. They also provide a means of evaluating the effectiveness of fuel flow modulation for controlling fuel jet behavior, demonstrating that fluctuations in the downstream spray distribution can be significantly reduced by phased fuel flow modulation. The paper describes a unique method for modulating the fuel and a relatively simple diagnostic for evaluating the fuel spray density and uniformity.
Investigation of Unsteady Gas Mixing Processes in Gas Turbine Burners Applying a Tracer-LIF Method
Authors: Schneiders T. , Hoeren A. , Michalski B. , Pfost H. , Scherer V. , Koestlin B.
Published: July 2014

The profound understanding of the mixing process of gaseous fuels and air is essential for the development of high temperature gas turbine premix-combustion with low pollutant emissions. At the Chair of Steam and Gas Turbines at the University of Bochum, a new approach has been made to obtain more information on the fuel gas-air mixing process. Investigations were undertaken applying an acetone Tracer-LIF-method with a high temporal resolution. Combined with statistical analysis, it yields insights into spatial and temporal mixture distributions and inhomogeneities.

The test rig operated at ambient conditions represents a generic model for gas mixing processes in gas turbine premix burners. Experiments are undertaken with different injection configurations by varying the geometry and the momentum flux ratio. The results of the investigations for opposed rows of gas injection orifices reveal similar characteristics and dependencies of spatial and temporal mixing distributions on the injection set-up.
An Experimental Investigation of Laminar Premixed Aviation Fuel-Air Flames
Authors: Kyne A. G. , Patterson P. M. , Pourkashanian M. , Wilson C. W. , Williams A.
Published: July 2014

An experimental investigation of a premixed kerosene/O2/N2 flame at various stoichiometries has been undertaken to provide a wider database for validation purposes. A premix burner has been designed to burn the multi-component fuel at atmospheric pressure. Particular emphasis is placed on the measurement of intermediate species using non-intrusive techniques such as laser-induced fluorescence for the measurement of OH concentrations. In addition to this, conventional gas analysis techniques were employed in providing concentration profiles of O2, CO2, and CO. Gas samples were withdrawn along the central axis of the flame with a quartz microprobe before being passed through a system of gas analysers. Temperature profiles were obtained using a Pt/Pt-13%Rh thermocouple.
CFD Modeling of the Aero Gas Turbine Combustor
Authors: Sivaramakrishna G. , Muthuveerappan N. , Shankar Venkataraman , Sampathkumaran T. K.
Published: July 2014

Performance of a practical aero gas turbine combustor has been predicted using a commercially available CFD code. The entire flow field from the inlet to exit of the combustor, including the liner injection holes, has been modeled with reasonable accuracy. Comparison of the quality of temperature distribution at combustor exit and combustion efficiency for part-load and full-load engine operating conditions are presented. A close agreement is observed between the predictions and the experiments. It is demonstrated that commercial CFD codes provide qualitative and reasonable quantitative information that can be effectively used in the combustor design optimization.
Comparison of Numerical and Experimental Results of a Premixed DLE Gas Turbine Combustor
Authors: Eggels Ruud L. G. M. , Brown Christopher T.
Published: July 2014

A numerical and experimental study on a premixed DLE gas turbine combustor has been performed. Experiments and CFD modelling have been carried out at isothermal and combusting conditions. The measurements were obtained at ERC using two component Laser Doppler Velocimetry. To be able to access the inner part of the combustor, the liners of the combustion chamber were outfitted with quartz windows. Temperature measurements were obtained at a few planes using a thermocouple.

Modelling of the combustor has been performed using an in-house CFD code. The combustion process has been modelled using a global reaction mechanism and a Flame Generated Manifold reaction mechanism in combination with a presumed PDF model to incorporate the effect of turbulent fluctuations. The Flame Generated Manifold method uses a flame library, which has been generated by performing a number of laminar one-dimensional flame calculations at representative conditions.

Comparing the numerical and experimental quite some differences are observed. The CFD model is able to predict the main features of the flow and combustion process, but does not predict the recirculation length accurately. Both combustion models, however, are able to predict the low combustion efficiency measured at the 1atm test condition.
NOx Formation in High-Pressure Jet-Stirred Reactors With Significance to Lean-Premixed Combustion Turbines
Authors: Rutar Teodora , Malte Philip C.
Published: July 2014

Measurements of NOx and CO in methane-fired, lean-premixed, high-pressure jet-stirred reactors (HP-JSRs) independently obtained by Rutar [1] and Rutar et al. [2] and by Bengtsson [3] and Bengtsson et al. [4] are well predicted assuming simple chemical reactor models and the GRI 3.0 chemical kinetic mechanism. The single-jet HP-JSR of Rutar [1] and Rutar et al. [2] is well modeled for NOx and CO assuming a single PSR for Damköhler number below 0.15. Under these conditions, the estimates of flame thickness indicate the flame zone, that is, the region of rapid oxidation and large concentrations of free radicals, fully fills the HP-JSR. For Damköhler number above 0.15, that is, for longer residence times, the NOx and CO are well modeled assuming two PSRs in series, representing a small flame zone followed by a large post-flame zone. The multi-jet reactor of Bengtsson [3] and Bengtsson et al. [4] is well modeled assuming a large PSR (over 88% of the reactor volume) followed by a short PFR, which accounts for the exit region of the HP-JSR and the short section of exhaust prior to the sampling point. The Damköhler number is estimated between 0.01 and 0.03.

Our modeling shows the NOx formation pathway contributions. Although all pathways, including Zeldovich (under the influence of super-equilibrium O-atom), nitrous oxide, Fenimore prompt, and NNH, contribute to the total NOx predicted, of special note are the following findings: 1) NOx formed by the nitrous oxide pathway is significant throughout the conditions studied; and 2) NOx formed by the Fenimore prompt pathway is significant when the fuel-air equivalence ratio is greater than about 0.7 (as might occur in a piloted lean-premixed combustor) or when the residence time of the flame zone is very short. The latter effect is a consequence of the short lifetime of the CH radical in flames.
Low NOX Combustion for Liquid Fuels: Atmospheric Pressure Experiments Using a Staged Prevaporizer-Premixer
Authors: Lee John C. Y. , Malte Philip C. , Benjamin Michael A.
Published: July 2014

Low emissions of NOx are obtained for a wide range of liquid fuels by using a staged prevaporizing-premixing injector. The injector relies on two stages of air temperature and fires into a laboratory jet-stirred reactor operated at atmospheric pressure and nominal ϕ of 0.6. The liquid fuels burned are methanol, normal alkanes from pentane to hexadecane, benzene, toluene, two grades of light naphtha and four grades of No. 2 diesel fuel. Additionally, natural gas, ethane and industrial propane are burned. For experiments conducted for 1790 K combustion temperature and 2.3±0.1 ms combustion residence time, the NOx (adjusted to 15% O2 dry) varies from a low of 3.5 ppmv for methanol to a high of 11.5 ppmv for No. 2 diesel fuel. For the most part, the NOx and CO are positively correlated with the fuel carbon to hydrogen ratio (C/H). Chemical kinetic modeling suggests the increase in NOx with C/H ratio is caused in significant part by the increasing super-equilibrium concentrations of O-atom created by the increasing levels of CO burning in the jet-stirred reactor. Fuel bound nitrogen also contributes NOx for the burning of the diesel fuel.

This paper describes the staged prevaporizing-premixing injector, the examination of the injector and the NOx and CO measurements and their interpretation. Optical measurements, using beams of He-Ne laser radiation passed across the outlet stream of the injector, indicate complete vaporization and a small variation in the cross-stream averaged fuel/air ratio. The later is determined by measuring the standard deviation and mean of the transmission of the laser beam passed through the stream. Additional measurements and inspections indicate no pressure oscillations within the injector and no gum and carbon deposition. Thus, the NOx and CO measurements are obtained for fully vaporized, well premixed conditions devoid of preflame reactions within the injector.
Lean/Lean Staged Low NOx Combustion for Near Stoichiometric Gas Turbine Primary Zone Conditions
Authors: Mkpadi M. C. , Andrews G. E. , Khan I. , Jaafar M. N. Mohd , Pourkashanian M. , Yang Y.
Published: July 2014

A two-stage lean/lean primary zone at simulated atmospheric pressure gas turbine combustion conditions was shown to give low NOx emissions at atmospheric pressure and 600K inlet temperature. All the combustion air was admitted to the first lean stage, where very lean <5ppm low NOx combustion occurred. A 40mm outlet diameter radial swirler with radial vane passage fuel injection was used in the first stage. After completion of this first stage lean combustion, second stage of fuel injection with no associated air occurred 320mm downstream of the primary swirler outlet, using 76mm radially inward wall injection. This was followed by a dump flow expansion to a 140mm diameter combustor. This provided an expansion shear layer and associated turbulence to mix the second stage fuel with the outlet products from the primary swirl combustion. The second stage fuel burned in the depleted oxygen (∼12%) from the first stage, but still remained a lean combustion zone overall. This design was intended to achieve engine power variation using the second stage fuel. The use of the second stage fuel was shown to reduce the NOx emissions by 50% compared with injecting all of the fuel into the first stage radial swirler. Emission levels of NOx at a first stage swirler equivalence ratio of 0.4 were below 5ppm and at an overall primary zone equivalence ratio of 0.8 with the two stage fuel injection, NOx emissions were about 20ppm. The second stage flame radial distribution of equivalence ratio and emissions was determined by gas analysis. The second stage NOx formation was predicted using CFD with flamelet modelling, with a flamelet strain library computed for 12% oxygen combustion. The mole fraction profile of NOx and combustion temperatures for a range of strain rates in the second stage were predicted. NOx emissions at 0.65 equivalence ratio overall was predicted to be 23ppm at 15% oxygen compared with 16ppm measured. Improved second stage fuel mixing is required to achieve lower NOx emissions and the use of wall turbulators is recommended.
Investigation of Two Advanced Cooling Mixing Concepts for a Rich Quench Lean Combustor
Authors: Diers Olaf , Koopman Johan , Fischer Michael , Hassa Christoph
Published: July 2014

To support the development of a rich quench lean pilot zone for a staged aeroengine combustor, two rectangular rich quench lean (RQL) combustor sectors have been investigated under atmospheric conditions. Two advanced cooling mixing concepts, effusion and impingement cooling with one and two rows of secondary air inlet holes in the mixing zone have been measured using intrusive and non-intrusive measurement techniques. The results elucidate the interrelations between the cooling concepts and the respective mixing and emissions performances. The measurements were accompanied by numerical calculations supporting the interpretation of the measured data. Drawbacks were observed for the near stoichiometric conditions of the effusion cooling concept near the wall, however the quench zone design with two rows of staggered holes performs well. On the contrary the impingement cooling system shows good results for the homogeneity of the primary zone, but since less quench air is available with impingement cooling, optimum mixing is more difficult to achieve.
A Hybrid System Based on a Personal Turbine (5 kW) and a SOFC Stack: A Flexible and High Efficiency Energy Concept for the Distributed Power Market
Authors: Magistri Loredana , Massardo Aristide , Rodgers Colin , McDonald Colin F.
Published: July 2014

In this paper a high efficiency and flexible hybrid system representing a new total energy concept for the distributed power market is presented.

The hybrid system is composed of a very small size (5 kW) micro gas turbine (named personal turbine – PT) presented in a companion paper by the authors (McDonald and Rodgers, 2001) coupled to a small size Solid Oxide Fuel Cell (SOFC) stack. The power of the whole system is 36 kW depending on the design parameters assumed for the stack.

The design and off design performance of the hybrid system have been obtained through the use of an appropriate modular code named “HS-SOFC” developed at the University of Genoa (Magistri, 1999) and described in detail in this paper.

The results of the simulation are presented and discussed with particular regards to: choice of the Hybrid System (HS) design point data, HS design point performance, off design performance of PT and SOFC stack, off design performance of the whole HS.

Some preliminary economic results are also included based on different fuel and capital cost scenarios and using the cost of electricity as the parameter for comparison between PT and HS.
A Novel Gas Turbine Concept for Combined Power, Heat and Cooling Generation
Authors: Arriagada Jaime , Rosén Per , Torisson Tord
Published: July 2014

An attractive and innovative technology for gas turbines for obtaining power, heat and cooling simultaneously has been developed and studied in Lund.

The basic idea behind this technology, called the TRIGENERATION™, is to interrupt the expansion in the gas turbine expander at an elevated pressure level, at which the heat rejection is carried out in a heat exchanger. After that, the expansion of the flue gas continues until ambient pressure, but the temperature is below the ambient temperature. This “negative” temperature difference allows the use of the exhaust for cooling purposes. The performance coefficient, defined as the ratio between all the benefits (power, heat and cooling) and the fuel heat, can reach values higher than 100% (HHV). This technology has its major potential when integrated with “wet” cycles, e.g. HAT and STIG. In such cycles, an easier extraction of the latent heat of vaporization within the humid flue gas is allowed, due to the higher water dew point at higher pressures. In this work, this technology is evaluated through simulations in a heat and mass balance program for the simple cycle gas turbine.
The Ubiquitous Personal Turbine (PT)…A Power Vision for the 21st Century
Authors: McDonald Colin F. , Rodgers Colin
Published: July 2014

Having a personal computer (PC) and related electronic equipment in the majority of US homes today is accepted without question. In the same vein, having a personal turbine (PT) in the home could also be taken for granted in coming decades to assure a constant and reliable source of electrical power, which is paramount in the e-business era. As addressed in this paper, gas turbine technology has advanced to the point where a natural gas-fired PT, rated at about 5 kW could reliably provide the total energy needs of an average home. The Industrial Revolution of the 18th Century, in which a centralized factory replaced cottage industries, was made possible by introduction of the steam engine. In the 21st Century IT Revolution, the situation will have essentially gone the full circle, with a high percentage of service industry work being done in the home. For individuals using the Internet for conducting business a reliable source of electrical power is mandatory. Alas, this can no longer be assured by the US power grid which is quickly reaching its capacity, and increasing outages will become more commonplace. One solution to this could be the use of PT’s in homes in both cities and remote areas. Also it would be ideally suited to applications in the developing countries, where it could provide the total energy needs of villages and small communities. In this introductory paper it is projected that when mass produced in very large quantities like automobile turbochargers, the PT unit cost would be competitive.
Applications of Gas Turbine Plants With Cooled Compressor Intake Air
Authors: Kakaras E. , Doukelis A. , Scharfe J.
Published: July 2014

The operation of gas turbines at ambient air temperatures higher than the ISO standard conditions (15°C) causes performance penalties both in the generated power and the efficiency of the engine. At high inlet-air temperatures, there can be a power loss of more than 20% combined with a significant increase in specific fuel consumption, compared to the ISO standard conditions. Thus, over a long period of time, gas turbines have a lower power output and efficiency than the equipment could actually perform.

It is the purpose of this work to present the possibilities and advantages from the integration of an innovative air-cooling system for reducing the gas turbine intake-air temperature. The advantages of this system are demonstrated by examining alternative scenarios of usage, representative of different countries and different climatic conditions.
A Converging Slot-Hole Film-Cooling Geometry: Part 1 — Low-Speed Flat-Plate Heat Transfer and Loss
Authors: Sargison J. E. , Guo S. M. , Oldfield M. L. G. , Lock G. D. , Rawlinson A. J.
Published: July 2014

This paper presents experimental measurements of the performance of a new film cooling hole geometry - the Converging Slot-Hole or Console. This novel, patented geometry has been designed to improve the heat transfer and aerodynamic loss performance of turbine vane and rotor blade cooling systems. The physical principles embodied in the new hole design are described, and a typical example of the console geometry is presented.

The cooling performance of a single row of consoles was compared experimentally with that of typical 35° cylindrical and fan-shaped holes and a slot, on a large-scale, flat-plate model at engine representative Reynolds numbers in a low speed tunnel with ambient temperature main flow. The hole throat area per unit width is matched for all four hole geometries. By independently varying the temperature of the heated coolant and the heat flux from an electrically heated, thermally insulated, constant heat flux surface, both the heat transfer coefficient and the adiabatic cooling effectiveness were deduced from digital photographs of the colour play of narrow-band thermochromic liquid crystals on the model surface.

A comparative measurement of the aerodynamic losses associated with each of the four film-cooling geometries was made by traversing the boundary layer at the downstream end of the flat plate.

The promising heat transfer and aerodynamic performance of the console geometry have justified further experiments on an engine representative nozzle guide vane in a transonic annular cascade presented in Part 2 of this paper [1].
A Converging Slot-Hole Film-Cooling Geometry: Part 2 — Transonic Nozzle Guide Vane Heat Transfer and Loss
Authors: Sargison J. E. , Guo S. M. , Oldfield M. L. G. , Lock G. D. , Rawlinson A. J.
Published: July 2014

This paper presents the first experimental measurements on an engine representative nozzle guide vane, of a new film cooling hole geometry, a Converging Slot-Hole or Console. The patented console geometry is designed to improve the heat transfer and aerodynamic performance of turbine vane and rotor blade cooling systems. These experiments follow the successful validation of the console design in low-speed flat-plate tests described in Part 1 of this paper (Sargison et al [1]).

Stereolithography was used to manufacture a resin model of a transonic, engine representative nozzle guide vane in which 7 rows of previously tested fan-shaped film-cooling holes were replaced by 4 rows of consoles. This vane was mounted in the annular vane ring of the Oxford Cold Heat Transfer Tunnel for testing at engine Reynolds numbers, Mach numbers and coolant to mainstream momentum flux ratios using a heavy gas to simulate the correct coolant to mainstream density ratio.

Heat transfer data were measured using wide band thermochromic liquid crystals and a modified analysis technique. Both surface heat transfer coefficient and the adiabatic cooling effectiveness were derived from computer-video records of hue changes during the transient tunnel run. The cooling performance, quantified by the heat flux at engine temperature levels, of the console vane compares favourably with that of the previously tested vane with fan-shaped holes.

The new console film cooling hole geometry offers advantages to the engine designer due to a superior aerodynamic efficiency over the fan-shaped hole geometry. These efficiency measurements are demonstrated by results from mid span traverses of a four hole pyramid probe downstream of the nozzle guide vane.
Film Cooling Effectiveness Downstream of Compound and Fan-Shaped Holes
Authors: Yuen C. H. N. , Martinez-Botas R. F. , Whitelaw J. H.
Published: July 2014

The steady-state wide band liquid crystal technique is used to study the film cooling performance downstream of a variety of geometries in a flat plate. This technique provides a detailed measurement of both cooling effectiveness and heat transfer coefficient. This paper presents the effects of compound and fan–shaped holes, the effect of streamwise angle variation has been presented at previous meetings. The following configurations are investigated: a single hole, a row of holes with a pitch-to-diameter ratio, p/D, of 3, two inline rows with p/D of 3 and two staggered rows with p/D of 6; all with a stream–wise angle of 30°. The spacing between two rows was chosen as 12.4D. Two lateral injection are investigated: 30° and 60° compound angle. The fan shaped hole used comprised of a lateral expansion of 14° from the original simple cylindrical shape with streamwise inclination of 30°; forward expansion was not incorporated. The length-to-diameter ratio, L/D, was maintained at a value of 4 for all the compound cases, the L/D for the fan shaped-hole was 6, larger due to its physical limitation. The tests were performed with a jet-to-freestream density ratio of 1.5; achieved by using a foreign gas (CO2) injection. The range of momentum flux ratios (M) covered was 0.33 to 1.67.

The row of 30° compound angle holes gave a lower value of effectiveness when compared to the non-compound case at M<0.67, but greater values and coverage at M>1.0, consistent with previous experiments. The row of 60° compound angle gave greater effectiveness, coverage and uniformity than the row of 30° compound at a given blowing ratio; the jet-to-jet interaction was greater for the 60° row due to the added lateral momentum. The row of 60° compound gave an increase of order 100% relative to the non-compounded row for M>1.

Two inline rows of fan-shape holes delivered less effectiveness than the corresponding single row at the same spanwise distance for a given jet fluid mass, or blowing ratio with twice the jet fluid mass. For equal blowing ratios and equal flow rates the fan-shaped hole gave a much higher effectiveness.
Shock Wave - Film Cooling Interactions in Transonic Flows
Authors: Ligrani P. M. , Saumweber C. , Schulz A. , Wittig S.
Published: July 2014

Interactions between shock waves and film cooling are described as they affect magnitudes of local and spanwise-averaged adiabatic film cooling effectiveness distributions. A row of three cylindrical holes is employed. Spanwise spacing of holes is 4 diameters, and inclination angle is 30 degrees. Freestream Mach numbers of 0.8 and 1.10–1.12 are used, with coolant to freestream density ratios of 1.5–1.6. Shadowgraph images show different shock structures as the blowing ratio is changed, and as the condition employed for injection of film into the cooling holes is altered. Investigated are film plenum conditions, as well as perpendicular film injection cross-flow Mach numbers of 0.15, 0.3, and 0.6. Dramatic changes to local and spanwise-averaged adiabatic film effectiveness distributions are then observed as different shock wave structures develop in the immediate vicinity of the film-cooling holes. Variations are especially evident as the data obtained with a supersonic Mach number are compared to the data obtained with a freestream Mach number of 0.8. Local and spanwise-averaged effectiveness magnitudes are generally higher when shock waves are present when a film plenum condition (with zero cross-flow Mach number) is utilized. Effectiveness values measured with a supersonic approaching freestream and shock waves then decrease as the injection cross-flow Mach number increases. Such changes are due to altered flow separation regions in film holes, different injection velocity distributions at hole exits, and alterations of static pressures at film hole exits produced by different types of shock wave events.
Effect of Crossflows on the Discharge Coefficient of Film Cooling Holes With Varying Angles of Inclination and Orientation
Authors: Gritsch Michael , Schulz Achmed , Wittig Sigmar
Published: July 2014

Measurements of discharge coefficients for five configurations of cylindrical film cooling hole geometries are presented. These comprise holes of varying angles of inclination (α= 30, 45, and 90deg) and orientation (γ= 0, 45, and 90deg) which are tested over a wide range of engine like conditions in terms of internal and external crossflow Mach numbers (Mam=0…1.2, Mac=0…0.6) as well as pressure ratios (ptc/pm=1…2.25).

Results show that discharge coefficients do not solely depend on hole geometry but are also profoundly affected by the internal and external crossflow conditions. The effect of increasing the orientation angle on the discharge behavior is very similar to the effect of increasing the inclination angle. Both result in higher losses particularly at the cooling hole inlet while the losses at the hole exit are only slightly affected.
Film Cooling Discharge Coefficient Measurments in a Turbulated Passage With Internal Cross Flow
Authors: Bunker Ronald S. , Bailey Jeremy C.
Published: July 2014

Gas turbine blades utilize internal geometry such as turbulator ribs for improved cooling. In some designs it may be desirable to benefit from the internal cooling enhancement of ribs as well as external film cooling. An experimental study has been performed to investigate the effect of turbulator rib placement on film hole discharge coefficient. In the study a square passage having a hydraulic diameter of 1.27 cm is used to feed a single angled film jet. The film hole angle to the surface is 30° and the hole length-to-diameter ratio is 4. Turbulators were placed in one of three positions: upstream of film hole inlet, downstream of film hole inlet, and with the film hole inlet centered between turbulators. For each case 90° turbulators with a passage blockage of 15% and a pitch to height ratio of 10 were used. Tests were run varying film hole-to-cross flow orientation as 30°, 90°, and 180°, pressure ratio from 1.02 to 1.8, and channel cross flow velocity from Mach 0 to 0.3. Film hole flow is captured in a static plenum with no external cross flow. Experimental results of film discharge coefficients for the turbulated cases and for a baseline smooth passage are presented. Alignment of the film hole entry with respect to the turbulator is shown to have a substantial effect on the resulting discharge coefficients. Depending on the relative alignment and flow direction, discharge coefficients can be increased or decreased 5 to 20% from the non-turbulated case, and in the worst instance experience a decrease of as much as 50%.
Measurements Over a Film-Cooled, Contoured Endwall With Various Coolant Injection Rates
Authors: Oke Rohit , Simon Terry , Shih Tom , Zhu Bin , Lin Yu Liang , Chyu Minking
Published: July 2014

This paper presents the results of a study of film coverage for coolant injection through an axisymmetric, contoured endwall of a high-pressure turbine first stage vane row. Tests are done on a low speed, linear cascade. The injection is either through a single slot upstream of the leading edges of the vanes or through two slots, one upstream of the other. Because the contouring begins upstream of the leading edges, injection is in an accelerating flow region. The effects of such injection on the secondary flows within the vane cascade are inferred by means of contours of dimensionless temperature. These thermal measurements are made by slightly heating the injection stream above the main flow temperature and documenting the temperatures inside the coolant-mainstream mixing zone. The thermal results are complemented with three-component, hot-wire measurements taken near the exit plane. Performance with different injection rates is discussed. The secondary flow seems to affect the cooling flow strongly when the momentum of the injected flow is small, compared to the main flow momentum. As a result, coolant coverage is non-uniform, with most of the coolant accumulating near the suction side of the passage. As the injection momentum is increased, some pressure-side accumulation of coolant is observed. However, non-uniformity still exists, with a lesser amount of coolant in the central region and more near the suction and pressure surfaces. For the same ratio of coolant to mainstream mass flow rates, cooling through a single slot seems to give more cooling towards the pressure side than does cooling through two slots. With the same mass flow rate, the one-slot case has higher injection momentum than does the two-slot case. This indicates that momentum flux is an important parameter in establishing the distribution of the coolant within the passage.
Film-Cooled Turbine Endwall in a Transonic Flow Field: Part II — Heat Transfer and Film-Cooling Effectiveness
Authors: Nicklas Martin
Published: July 2014

Thermodynamic and aerodynamic measurements were carried out in a linear turbine cascade with transonic flow field. Heat transfer and adiabatic film-cooling effectiveness resulting from the interaction of the flow field and the ejected coolant at the endwall were measured and will be discussed in two parts. The investigations were performed in the Windtunnel for Straight Cascades (EGG) at the DLR, Goettingen. The film-cooled NGV endwall was operated at representative dimensionless engine conditions of Mach and Reynolds number Ma2is=1.0 and Re2=850,000 respectively.

Part II of the paper discusses the thermodynamic measurements. Detailed temperature measurements were carried out on a turbine stator endwall. In order to determine the surface heat transfer and adiabatic film-cooling effectiveness, an infrared camera system in a rectilinear wind tunnel measured the endwall temperatures in the transonic flow field. The adiabatic film-cooling effectiveness was determined using the superposition method. Measurements were carried out to first, validate the assumptions of theory and second, analyse the error associated with the measurements. Effects of coolant ejection from a slot and three rows of holes were investigated and compared with each other. The influence of Mach number and blowing ratio on the heat transfer were further aspects of the investigation. Strong variations in heat transfer and film-cooling effectiveness due to the interaction of the coolant air and the secondary flow field were found. Based on the results of this investigation an improved cooling design will be investigated in a follow-up project.