bluuebunny/crossref_metadata_2025 huggingface dataset:
State Space Identification of Nonlinear Hydrodynamic Bearing by Eigensystem Realization Algorithm (ERA)
Authors: Shiau T. N. , Tsai M. S. , Cheng C. H.
Published: February 2009

Large vibration of a rotor-bearing system excited by unbalance of rotor shaft or external forces can deteriorate the performance and shorten the lifetime of the system. The hydrodynamic bearing can provide desirable damping for a rotor-bearing system. In order to fully utilize the function of the hydrodynamic bearing for vibration reduction, a state-space technique is developed to identify the parameters (stiffness and damping) of the linearized hydrodynamic bearing. The eigensystem realization algorithm (ERA) is adopted to find the discrete state space model of system. It is shown that the ERA approach can be a very effective way for identification of the rotor-bearing system. The discrete state space model is further transformed to the continuous model that can be utilized to obtain the coefficients for the hydrodynamic bearing system. By comparing the output signal of the identified system and the nonlinear rotor-bearing dynamic model, the identification accuracy is verified. More simulation results on different values of eccentricity are also plotted to show the characteristic of a hydrodynamic bearing.
Rotordynamic Forces Due to Rotor Sealing Gap in Axial Turbines
Authors: Kim Woo June , Song Seung Jin
Published: February 2009

Turbines have been susceptible to flow-induced vibration. In such vibrations, direct damping and cross stiffness effects of aerodynamic forces determine rotordynamic stability. Previous research efforts have been focused mostly on either isolated labyrinth seals or unshrouded turbines. Recently, steady flow in a turbine with a statically offset shrouded rotor has been modeled, and some stiffness predictions have been obtained. The model couples the seal flow to the main passage flow and uses a small perturbation approach to determine non-axisymmetric flow conditions. Seal gland pressure asymmetry and tangential force asymmetry were found to be responsible for the destabilizing stiffness force generation. However, aerodynamic damping (i.e. unsteady) effects in shrouded turbines with whirling rotors have not yet been examined. Therefore, this paper presents a new model to predict unsteady flow field response in such turbines. The model uses basic conservation laws. Input parameters include aerodynamic parameters, geometric parameters, and a prescribed rotor whirl. From the calculated unsteady perturbations in velocity and pressure, the damping effects of aerodynamic forces have been analyzed for the first time. The results show that aerodynamic damping is primarily due to the variation in the magnitude of seal gland pressure asymmetry. Also, damping in shrouded axial turbines is found to be much smaller than that in unshrouded turbines.
Measurement of Smoke Particle Size and Distribution Within a Gas Turbine Combustor
Authors: Brundish K. D. , Miller M. N. , Wilson C. W. , Hilton M. , Johnson M. P. , Jefferies M.
Published: February 2009

The objective of the work described in this paper was to identify a method of making measurements of the smoke particle size distribution within the sector of a gas turbine combustor, using a Scanning Mobility Particle Sizing (SMPS) analyser. As well as gaining a better understanding of the combustion process, the principal reasons for gathering these data was so that they could be used as validation for Computational Fluid Dynamic (CFD) and chemical kinetic models. Smoke mass and gaseous emission measurements were also made simultaneously. A “water cooled,” gas sampling probe was utilised to perform the measurements at realistic operating conditions within a generic gas turbine combustor sector. Such measurements had not been previously performed and consequently initial work was undertaken to gain confidence in the experimental configuration. During this investigation, a limited amount of data were acquired from three axial planes within the combustor. The total number of test points measured were 45. Plots of the data are presented in 2 dimensional contour format at specific axial locations in addition to axial plots to show trends from the primary zone to the exit of the combustor. Contour plots of smoke particle size show that regions of high smoke number concentration once formed in zones close to the fuel injector persist in a similar spatial location further downstream. Axial trends indicate that the average smoke particle size and number concentration diminishes as a function of distance from the fuel injector. From a technical perspective, the analytical techniques used proved to be robust. As expected, making measurements close to the fuel injector proved to be difficult. This was because the quantity of smoke in the region was greater than 1000 mg/m3. It was found necessary to dilute the sample prior to the determination of the particle number concentration using SMPS. The issues associated with SMPS dilution are discussed.
Large Eddy Simulation of Film Cooling Flow From an Inclined Cylindrical Jet
Authors: Acharya Sumanta , Tyagi Mayank
Published: February 2009

Predictions of turbine blade film cooling have traditionally employed Reynolds averaged Navier Stokes (RANS) solvers and two-equation models for turbulence. Evaluation of several versions of such models have revealed that the existing two equation models fail to resolve the anisotropy and the dynamics of the highly complex flow field created by the jet-crossflow interaction. A more accurate prediction of the flow field can be obtained from large eddy simulations (LES) where the dynamics of the larger scales in the flow are directly resolved. In the present paper, such an approach has been used, and results are presented for a row of inclined cylindrical holes at blowing ratios of 0.5 and 1, and a Reynolds number of 11100 and 22200 respectively based on the jet velocity and hole diameter. Comparison of the time-averaged LES predictions with the flow measurements of Lavrich and Chiappetta [1] shows that LES is able to predict the flow field with reasonable accuracy. The unsteady three-dimensional flow field is shown to be dominated by packets of hairpin shaped vortices. The dynamics of the hairpin vortices in the wake region of the injected jet and their influence on the unsteady wall heat transfer is presented. Generation of “hot spots” and their migration on the film-cooled surface is associated with the entrainment induced by the hairpin structures. Several geometric properties of a “mixing interface” around hairpin coherent structures are presented to illustrate and quantify their impact on the entrainment rates and mixing processes in the wake region.
Blade Excitation by Aerodynamic Instabilities: A Compressor Blade Study
Authors: Kielb Robert E. , Barter John W. , Thomas Jeffrey P. , Hall Kenneth C.
Published: February 2009

In this paper, we investigate non-synchronous vibrations (NSV) in turbomachinery, an aeromechanic phenomenon in which rotor blades are driven by a fluid dynamic instability. Unlike flutter, a self-excited vibration in which vibrating rotor blades and the resulting unsteady aerodynamic forces are mutually reinforcing, NSV is primarily a fluid dynamic instability that can cause large amplitude vibrations if the natural frequency of the instability is near the natural frequency of the rotor blade. In this paper, we present both experimental and computational data. Experimental data was obtained from a full size compressor rig where the instrumentation consisted of blade-mounted strain gages and case-mounted unsteady pressure transducers. The computational simulation used a three-dimensional Reynolds averaged Navier-Stokes (RANS) time accurate flow solver. The computational results suggest that the primary flow features of NSV are a coupled suction side vortex shedding and a tip flow instability. The simulation predicts a fluid dynamic instability frequency that is in reasonable agreement with the experimentally measured value.
Results and Experience From Operation and Testing of ALSTOM’s 30 MW GT10C Gas Turbine
Authors: Hellberg Anders , Norden Georg , Andersson Mats , Widgren Thomas , Hjalmarsson Christer , Jansson Jan , Andersson Lennart , Ignell Lars-Erik
Published: February 2009

ALSTOM’s new gas turbine, the GT10C, is a 30 MW industrial gas turbine for mechanical drive and power generation, which has been upgraded from the 25 MW GT10B. The thermal efficiency of the new gas turbine is 37.3% at ISO inlet conditions with no losses. The GT10C features a dual-fuel dry low emission gas turbine, with emissions values of 15 ppm NOx on gaseous fuel and 42 ppm NOX on liquid fuel (also dry). The GT10C was first started and operated on load in November 2001 and the test program is ongoing until the fall of 2002. The program covers a complete package test, including gas turbine, auxiliaries and control system, to ensure package availability. For the tests, a new test rig has been built in Finspong, Sweden, for testing on both natural gas and liquid fuels. The tests have been very successful, achieving the product targets, for example below 15 ppm NOx, without combustor pulsations. This paper discusses operation experience from the test rig, where the engine has been tested on both natural gas and liquid fuel over the whole load range. The engine has been equipped with over 1200 measuring points, covering the complete gas turbine. All critical parameters have been carefully verified in the test, such as turbine blade temperature and stresses, combustor temperatures and dynamics and engine performance. Results from the tests and measurements will be discussed in this paper. Performance and emissions will also be evaluated.
Simplified Simulation Block Diagram of Twin-Shaft Gas Turbines
Authors: Bozzi Luca , Crosa Giampaolo , Trucco Angela
Published: February 2009

This paper provides a simplified mathematical model of twin shaft gas turbine suitable for use in dynamic studies of both electric power generation plants and variable speed mechanical drive applications. The main purpose was to define a simulation block diagram, constituted by algebraic equations and simplified transfer functions, which can be easily derived from the gas plant design data utilising the suitable equations and nomographs presented in the paper. The 3 to 30 MW power range of twin shaft gas turbines is covered. The set-up parameters and details applicable to the model are listed, in the paper, for the various machine sizes and model series. The dynamic model has been developed by simplifying a more detailed one, also here presented, with relatively little loss in dynamic accuracy but considerable advantages in terms of computational time. In the proposed test case, the results of both models have been compared simulating the transient response of a twin shaft gas turbine powering a water-jet propulsor for high-speed ships. The accurate performance prediction capability of both models is verified, for a wide range of operating conditions, by comparison with test results from actual field installations.
Design of the 6C Heavy-Duty Gas Turbine
Authors: Harper David , Martin Devin , Miller Harold , Grimley Robert , Greiner Fre´de´ric
Published: February 2009

The MS6001C gas turbine combines the proven reliability of the General Electric gas turbine family with the advanced technology developed for the FA, FB and H machine designs. The engine configuration is a single shaft bolted rotor, driving a 50 or 60 Hz. generator though a cold end mounted load gear. Rated at 42.3 MW, with a thermal efficiency of 36.3%, the MS6001C will provide greater than a four percent increase in efficiency over the MS6001B. This paper is focused on the design and development of the MS6001C gas turbine, highlighting the commonality between this and other General Electric Power Systems (GEPS) and General Electric Aircraft Engines (GEAE) designs, as well as introducing some new and innovative features. The new high efficiency, 12 stage, axial flow compressor, features a 19:1 pressure ratio with three stages of variable guide vanes. The can annular, six chamber, Dry Low NOx (DLN-2.5H) combustion system is scaled from field proven, low emission technology. The turbine incorporates three stages, two cooled blade rows, and operates at a 1327°C firing temperature. After a thorough factory full speed no load test has been conducted, the first MS6001C engine will be shipped to a customer site in Kemalpasalzmir Turkey, where an instrumented full load test will be conducted to validate the design.
Firing Low Viscosity Liquid Fuels in Heavy Duty Gas Turbines
Authors: Stalder Jean-Pierre , Roberts Phil
Published: February 2009

Sustained economic growth has created a strong demand for electrical energy worldwide. Security of fuel supply and cost are therefore very often critical issues for thermal capacity additions. Also the distance from fuel sources and available fuel transport infrastructure is an important factor in the cost of generation. Many plant locations have only limited supplies of conventional gas turbine fuels, namely natural gas and distillate fuels, thus a drive to diversify the fuels involved. For other electricity producers, the optimal use of existing or potential fuel resources is a must for economical reasons. Therefore, the possibility of using alternative gas turbine liquid fuels, such as volatile and/or low viscosity fuels like naphtha, gas condensates, kerosene, methanol, ethanol, or low lubricity distillate fuels; refinery by-products such as BTX fuels (benzene-toluene-xylene mixtures), LCO-light cycle oil, or in the future synthetic fuels (GTL) are particularly interesting for their ability to be fired in heavy duty gas turbines. However, the practical use of these fuels creates specific issues such as low lubricity properties which can affect sensitive key components like fuel pumps and flow dividers. This paper addresses the many practical aspects of using fuel lubricity additives for reduced component wear in gas turbine fuel systems, and for reliability and successful plant operation on these alternative gas turbine liquid fuels. Also an overview of acquired experience is given.
An Investigation of the Heat Transfer for Full Coverage Film Cooling
Authors: Kelly Grady B. , Bogard David G.
Published: February 2009

An experimental study was conducted on the heat transfer to a film-cooled flat plate with a full coverage array of normal holes. The film cooling array consisted of ten staggered coolant rows, and each coolant hole had an L/D = 1.0 and an injection angle of α = 90°. Measurements of the heat transfer coefficient with and without film cooling were taken, in order to determine the increase in the heat transfer coefficient due to coolant injection. These experiments were conducted with heated and unheated starting lengths, and with low and high mainstream turbulence levels. The heat transfer coefficient ratios were used in conjunction with adiabatic effectiveness data taken in a previous study to determine the distributions of the overall heat load reduction. Heat transfer coefficient data from a single row of coolant holes were also taken. These data were used to evaluate several concepts for predicting full coverage heat transfer coefficient distributions based on the single row data.
A Detailed Experimental Investigation of a Perforated Heat Transfer Surface Applied to Gas Turbine Recuperators
Authors: Adams Juan C. , Ireland Peter T. , Cerza Martin , Oswald James
Published: February 2009

An effort is made to explain and improve the understanding of the mechanisms behind the thermo-hydraulic performance of perforated extended surfaces used in compact heat exchangers in the laminar flow regime (ReD = 400–2500). A transient liquid crystal technique, which uses Helium as operating fluid, together with digital image photographic processing have been used to provide measurements of local heat transfer coefficients for this geometry. This work has found that through the use of perforated surfaces there exists a local heat transfer enhancement benefit. It has also been found that although perforations cause a partial restart of the thermal boundary layer, a significant overall surface heat transfer enhancement may not be achieved over plain surfaces. It was also found that the distance between the fin’s leading edge and the point of last significant enhancement resulting from a perforation, linearly depends on Reynolds number. Local heat transfer coefficient measurements were validated by single blow experimentation of similar geometries. The transient single blow technique used the curve-matching method to compare predicted and experimental temperatures.
Large Eddy Simulation of Impinging Jets in Crossflow
Authors: Spencer Adrian , Adumitroaie Virgil
Published: February 2009

Large Eddy Simulations and RANS predictions have been carried out for a generic primary zone type jet configuration, for which significant LDA experimental data is available. It consists of an annular passage feeding a row of ports that issue jets into a confined crossflow. A bleed flow of 50% past the ports in the feed annulus and a jet to cross flow ratio of 5 are set-up in order to be representative of annulus fed primary jets. Time averaged inlet boundary conditions have been taken from experimental data and have had time-correlated fluctuations with the correct RMS values and time scales imposed on them. Calculations have been performed on a modest PC cluster using the CFD-ACE+ flow solver package. Results show that LES is able to surpass RANS quantitatively and qualitatively. At the time-average impingement point of the jets the LES predicted normal stresses are in considerably better agreement with experimental data than is RANS, which is to be expected considering the limitations of k-ε models relying upon linear stress-strain relationships. Phenomena impossible to capture using RANS are also well predicted by LES, such as bimodal pdf’s that have been witnessed at the time average stagnation point where the cross flow and jet back flow meet. By solving for a conserved scalar it has also been possible to examine mixing rates within the recirculation zone.
Inlet Fogging for a 655 MW Combined Cycle Power Plant: Design, Implementation and Operating Experience
Authors: Gajjar Hemant , Chaker Mustapha , Dighe Ajay , Meher-Homji Cyrus B.
Published: February 2009

The design, installation, commissioning and operation of a fogging system for a large 655 MW combined cycle power plant is described. Technical details and practical installation issues are discussed. Special considerations as to how the fogging system could help in the augmentation of power during high temperature and low frequency operation of the gas turbine is discussed. Finally a discussion is made regarding the importance of inlet filtration and the proper selection of blade coatings.
Experiences With Microturbine Generator Systems Installed in the South Coast Air Quality Management District
Authors: McDonell V. G. , Hack R. L. , Lee S. W. , Mauzey J. L. , Wojciechowski J. S. , Samuelsen G. S.
Published: February 2009

A comprehensive field data collection campaign is reported on in which operational data are being obtained from microturbine generators located in the South Coast Air Quality Management District (AQMD). The data obtained are archived in a SQL database, which provides the ability to look at various performance aspects as a function of many parameters interactively on the Internet. An overview of the program is provided along with details regarding the data collection and archiving strategies. To provide a framework relative to optimal operation of these systems in the region, economics associated with various operational schedules as a function of various rate structures in Southern California are provided. In addition to quantitative operational characteristics and performance results, some general end-user impressions of the technology and of the overall installation process are also documented. Details from three representative sites are presented.
Measurements and Predictions of Heat Transfer on Rotor Blades in a Transonic Turbine Cascade
Authors: Giel Paul W. , Boyle Robert J. , Bunker Ronald S.
Published: February 2009

Detailed heat transfer measurements and predictions are given for a power generation turbine rotor with 127 deg of nominal turning and an axial chord of 130 mm. Data were obtained for a set of four exit Reynolds numbers comprised of the facility maximum point of 2.50 × 106, as well as conditions which represent 50%, 25%, and 15% of this maximum condition. Three ideal exit pressure ratios were examined including the design point of 1.443, as well as conditions which represent −25% and +20% of the design value. Three inlet flow angles were examined including the design point and ±5 deg off-design angles. Measurements were made in a linear cascade with highly three-dimensional blade passage flows that resulted from the high flow turning and thick inlet boundary layers. Inlet turbulence was generated with a blown square bar grid. The purpose of the work is the extension of three-dimensional predictive modeling capability for airfoil external heat transfer to engine specific conditions including blade shape, Reynolds numbers, and Mach numbers. Data were obtained by a steady-state technique using a thin-foil heater wrapped around a low thermal conductivity blade. Surface temperatures were measured using calibrated liquid crystals. The results show the effects of strong secondary vortical flows, laminar-to-turbulent transition, and also show good detail in the stagnation region.
Gas Turbine Intake Systems: High Velocity Filtration for Marine GT Installations — Part 2
Authors: Hiner S. D. , Mudge R. K.
Published: February 2009

Following the development of a high velocity spray eliminator system for marine gas turbines, a sea trial has been completed on board a Royal Navy vessel, for back to back comparison with a unit of conventional design. This paper, will give a brief overview of the trial fit to HMS Coventry. It will then continue by presenting in detail the data obtained throughout the trial and showing the resulting comparisons between the new high velocity and conventional designs. The initial and final inspections of both engines will be presented and the appraisal by Rolls Royce, the engine design authority, will be discussed. Conclusions will be drawn detailing the suitability of the new high velocity design for use onboard RN vessels, to protect their gas turbine intakes. Design parameters for the intakes of the WR21 will be proposed to demonstrate the system’s potential benefits.
The Feasibility of Using an Air Turbine to Drive an Afterburner Fuel Pump
Authors: Backus N. E. , Ramsden K. W. , Yates M. K. , Laskaridis P. , Pilidis P.
Published: February 2009

Current fighter engine designs extract power to drive the afterburner fuel pump through the use of a gearbox. The presence of the gearbox only allows the fuel pump to operate at a fixed proportion of engine speed. In addition the fuel pump is continually rotating, although not pumping fuel, even when the afterburner is not engaged. This article investigates the feasibility of using an air turbine to drive the afterburner fuel pump in preparation for supporting an all-electric engine. Utilising performance data for a typical modern military engine, 1-dimensional design techniques were used to design several radial turbines to power the afterburner fuel pump. A choice of an axial or a radial air turbine is possible. Both were reviewed and it was determined that a radial turbine is optimum based on manufacturability and (theoretical) efficiency. Several design iterations were completed to determine the estimated weight and size based on various air off-take locations, mass flows, and rotational speeds. These iterations showed that increasing mass flow allows for lower rotational speeds and/or smaller diameter rotors, but with a corresponding increases in thrust penalties.
Adjoint Harmonic Sensitivities for Forced Response Minimization
Authors: Duta Mihai C. , Campobasso Michele S. , Giles Michael B. , Lapworth Leigh B.
Published: February 2009

This paper presents an adjoint analysis for 3d unsteady viscous flows aimed at the calculation of linear worksum sensitivities involved in turbomachinery forced response predictions. The worksum values are normally obtained from linear harmonic flow calculations but can also be computed using the solution to the adjoint of the linear harmonic flow equations. The adjoint method has a clear advantage over the linear approach if used within a rotor forced vibration minimization procedure which requires the structural response to a large number of different flow excitation sources characterized by a unique frequency and inter-blade phase angle. Whereas the linear approach requires a number of linear flow calculations at least equal to the number of excitation sources, the adjoint method reduces this cost to a single adjoint solution for each structural mode of rotor response. A practical example is given to illustrate the dramatic computational saving associated with the adjoint approach.
Application of CFD Analysis for Rotating Machinery: Part 1 — Hydrodynamic, Hydrostatic Bearings and Squeeze Film Damper
Authors: Guo Zenglin , Hirano Toshio , Kirk R. Gordon
Published: February 2009

The traditional method for bearing and damper analysis usually involves a development of rather complicated numerical calculation programs that may just focus on a simplified and specific physical model. The application of the general CFD codes may make this analysis available and effective where complex flow geometries are involved or when more detailed solutions are needed. In this study, CFX-TASCflow is employed to simulate various fixed geometry fluid-film bearing and damper designs. Some of the capabilities in CFX-TASCflow are applied to simulate the pressure field and calculate the static and dynamic characteristics of hydrodynamic, hydrostatic and hybrid bearings as well as squeeze film dampers. The comparison between the CFD analysis and current computer programs used in industry has been made. The results show reasonable agreement in general. Some of possible reasons for the differences are discussed. It leaves room for further investigation and improvement on the methods of computation.
Micro, Industrial, and Advanced Gas Turbines Employing Recuperators
Authors: Kesseli James , Wolf Thomas , Nash James , Freedman Steven
Published: February 2009

Recuperators increase system efficiencies in gas turbine engines by recovering exhaust heat to the compressor discharge stream. In this study, the performance and economics of recuperation are evaluated and presented for a practical range of effectiveness with typical pressure-loss-fractions. The strong correlation between recuperator cost and engine specific-power is shown, using a recuperator designed and manufactured at a highly automated facility by Ingersoll-Rand. This commercially available recuperator is also described, with specific emphasis on features contributing to its exceptional durability.
Coal-Based Power Plant System Configurations for the 21st Century
Authors: Rao A. D. , Samuelsen G. S. , Robson F. L. , Geisbrecht R. A.
Published: February 2009

Under the sponsorship of the U.S. Department of Energy/National Energy Technology Laboratory, a multi-disciplinary team led by the Advanced Power and Energy Program of the University of California at Irvine is defining the system engineering issues associated with the integration of key components and subsystems into power plant systems that meet performance and emission goals of the Vision 21 program. Earlier tasks of the program have narrowed down the myriad of fuel processing, power generation, and emission control technologies to selected scenarios that identify those combinations having the potential to achieve the Vision 21 program goals of high efficiency and minimized environmental impact while using fossil fuels. These analyses have been extended to consider coal gasification processes combined with the advanced power cycles previously identified. The technology levels considered are based on projected technical and manufacturing advances being made in industry and on advances identified in current and future government supported research. Examples of systems included in these advanced cycles are solid oxide fuel cells, advanced cycle gas turbines, membrane separation of gases and oxygen-enhanced combustion.
The Analysis and Design of Saturators for Power Generation Cycles: Part 2 — Heat and Mass Transfer
Authors: Aramayo-Prudencio A. , Young J. B.
Published: February 2009

The introduction of water into a gas turbine circuit is known to provide benefits of increased efficiency and specific work output. There are several methods of humidification but the use of a pressurised saturator in an evaporative cycle offers many attractive features. This two-part paper presents an in-depth study of the saturator, in Part 1 via a thermodynamic approach and in Part 2 via a detailed heat and mass transfer analysis. The analysis in Part 2 starts from a rigorous control volume formulation and includes a derivation of the entropy production equation in keeping with the theory of irreversible thermodynamics. The specification of the heat and mass transfer coefficients is discussed and an analytical expression derived for the liquid-gas interface temperature. A novel numerical procedure for solving the equations is then presented which provides more flexibility than the traditional method of solution. After a discussion on the possibility of occurrence of supersaturated vapour states, results are presented showing the effects of variation of saturator height. The limiting condition when the water exit temperature falls to the inlet vapour adiabatic saturation temperature is also discussed.
Installation and Operation of Simple Cycle Gas Turbine Power Plants Utilizing SCR and CO Catalyst for Reduction of NOx and CO Emissions
Authors: Kaufman A. J. , Moen David
Published: February 2009

Older gas turbines can meet strict, present day emission standards by the addition of such emission reducing technologies as water injection, reduced emission combustion components, CO reduction catalyst and selective catalytic NOx reduction (SCR). The following is a description of a gas turbine peaking plant using SCR and a CO catalyst reduction system to allow 30 year old gas turbines to attain very low levels of NOx and CO emissions. Installation, startup and day-to-day operation are described, as well as operation with anhydrous ammonia.
Identification of the Maximum Responding Blade in Mistuned Bladed Disks
Authors: Xiao Bing , Rivas-Guerra Alejandro J. , Mignolet Marc P.
Published: February 2009

This paper focuses on the identification/prediction of the blade exhibiting the largest response in mistuned bladed disks. This information is very important in experimental/testing efforts as it permits the most effective positioning of a few gages to capture the maximum response on the disk. In computational statistical analyses, knowing the highest responding blade is also quite valuable as it may lead to computational savings in the determination of the maximum response. Different strategies are proposed here for the experimental and computational contexts. In the former situation, mistuning is typically unknown but only one or a few disks must be considered. The proposed solution is then to estimate the mistuned blade properties and to rely on this identified bladed disk model to predict the blades that are likely to exhibit the largest responses through exact, full disk solutions. On the contrary, in computational statistical analyses, mistuning is specified but a potentially large number of disks must be analyzed and it is desired to bypass the ensemble of full disk solutions. Accordingly, a novel, computationally very efficient algorithm is proposed for a preliminary estimation of the forced response of mistuned disks from which the blades that are likely to exhibit the largest responses can be predicted. Examples of application on single- and two-degree-of-freedom per blade models and a reduced order model of a blisk demonstrate the reliability of the proposed strategies.
Experimental Investigation of SI Engine Performance Using Oxygenated Fuel
Authors: Al-Farayedhi Abdulghani A. , Al-Dawood Ali M. , Gandhidasan P.
Published: February 2009

The current experimental study aims to examine the effects of using oxygenates as a replacement of lead additives in gasoline on performance of a typical SI engine. The tested oxygenates are MTBE, methanol, and ethanol. These oxygenates were blended with a base unleaded fuel in three ratios (10, 15, and 20 vol.%). The engine maximum output and thermal efficiency were evaluated at a variety of engine operating conditions using an engine dynamometer set-up. The results of the oxygenated blends were compared to those of the base fuel and of a leaded fuel prepared by adding TEL to the base. When compared to the base and leaded fuels, the oxygenated blends improved the engine brake thermal efficiency. The leaded fuel performed better than the oxygenated blends in terms of the maximum output of the engine except in the case of 20 vol.% methanol and 15 vol.% ethanol blends. Overall, the methanol blends performed better than the other oxygenated blends in terms of engine output and thermal efficiency.
The Effect of Parametric Variations on Formaldehyde Emissions From a Large Bore Natural Gas Engine
Authors: Olsen Daniel B. , Willson Bryan D.
Published: February 2009

Formaldehyde is a hazardous air pollutant (HAP) that is typically emitted from natural gas-fired internal combustion engines as a product of incomplete combustion. The US Environmental Protection Agency (EPA) is currently developing national emission standards to regulate HAP emissions, including formaldehyde, from stationary reciprocating internal combustion engines under Title III of the 1990 Clean Air Act Amendments. This work investigates the effect that variations of engine operating parameters have on formaldehyde emissions from a large bore natural gas engine. The subject engine is a Cooper-Bessemer GMV-4TF two-stroke cycle engine with a 14″ (36 cm) bore and a 14″ (36 cm) stroke. Engine parameter variations investigated include load, boost, ignition timing, inlet air humidity ratio, air manifold temperature, jacket water temperature, prechamber fuel supply pressure, exhaust backpressure, and speed. The data analysis and interpretation is performed with reference to possible formaldehyde formation mechanisms and in-cylinder phenomena.
Supersonic Injection of Gaseous Fuel Described as Possible Solution for NOx Emissions From Large-Bore Gas Engines
Authors: Borissov Anatoli , McCoy James J.
Published: February 2009

Both physical and mathematical models were built to describe the main processes in large-bore gas engines. Based on the detail modeling and analysis of cylinder airflow, fuel injection, mixing, combustion and NOx generation, it was possible to pinpoint the problem of abnormal NOx production, even for lean mixtures, that occurs in these engines. In addition, analysis of the experimental data of jet mixing using high-speed photographic evidence, as well as engine performance data, has helped in the understanding of the mixing process. This has resulted in the development of a new way of the mixing of fuel and air utilizing multiple-nozzle supersonic injection. The fuel injection system is designed to optimize the mixing of the methane fuel with the air in the cylinder of a large bore natural gas engine. The design goals of low-pressure (<130 psi), all-electronic valve actuation, and optimal mixing were all achieved with a unique valve/nozzle arrangement. Later, a laser induced fluorescence method was used to take high-speed photographs of the development of the fuel jet exiting the newly developed supersonic electronic fuel injector (SSEFI). This result, together with the results of numerous experimental testing of SSEFI on different engines (GMVH-6, GMW-10, V-250, UTC-165) are presented as evidence of the success of the SSEFI application for the improvement of engine performance, engine control and NOx reduction.
Maritime Administration’s Formulation of a Maritime Energy and Clean Emissions Program
Authors: Gore Daniel J.
Published: February 2009

The Environmental Protection Agency promulgation of “Control of Emissions of Air Pollution from New Marine Compression Ignition Engines at or above 37 kW,” on December 29, 1999, marked the first time federal air pollution regulations were directly applied to marine engines for commercial U.S. ships. Perhaps surprisingly, these regulations are not having as much impact as are individual State Implementation Plans (SIP) for Nitrogen Oxides (NOx) attainment, and local political pressures. These regional plans and pressures are forcing many domestic marine operators and ports to get a quick education on the cause and mitigation of air pollution. Cases in point, include: • The State of Alaska now fines passenger vessels that enter ports with greater than allowable stack gas opacities. One cruise operator has opted to plug into shore power when its vessels are tied up to pier. • In the Ports of Los Angeles and Long Beach vessel operators have been asked to slow vessel speeds below normal while entering and exiting in a voluntary attempt to reduce NOx emissions. • Environmentalists in the San Francisco Bay Area are applying significant political pressures to ensure proposed new ferry systems emit a minimum of air pollution. • The State of Texas briefly considered stopping all industrial equipment in the Port of Houston for twelve hours per day as a method of decreasing area ozone formation. • Potential NOx emissions generated during imminent channel dredging in the Port of New York and New Jersey is impeding the development of the latest State Implementation Plan. Local pressures are likely to continue to grow, federal regulations are set to become more stringent, and international conventions loom on the horizon. However, as expected in such a competitive industry, concerns are often focused on the bottom line in which cost of operations is a pre-eminent factor. It was in view of these dynamics that the federal Maritime Administration (MARAD) recently launched the Maritime Energy and Clean Emissions Program. This paper introduces the Program, including the background, evolution, and progress of each strategic goal. This paper is intended to be an overview. Attention is paid to the potential transferability and/or development of technologies not previously deployed in the U.S. marine environment. Any of the specific projects described could become the basis for a separate technical paper.
Experimental Method for the Determination of Instantaneous Diesel Engine Pollutant Emissions During Transients
Authors: Thouvenel Nicolas , Tauzia Xavier , Chesse Pascal , Hetet Jean-Franc¸ois
Published: February 2009

This paper presents a method to estimate instantaneous diesel engine emissions during transients using analytical means usually adopted for steady state investigations. The initial emphasis is on the inability of the conventional analysis systems to directly provide instantaneous levels of gaseous emissions during transients. In the ensuing section, a signal reconstruction technique used to rebuild instantaneous pollutant emissions at the engine exhaust is described. This reconstruction is based on a transfer function, which is the ratio of known measured and applied pollution signals. As a validation of this technique, the inversion of the transfer function is then applied to measurements obtained during basic tests consisting of steps and ramps. Finally, a method for estimating diesel particulates during transients through a correlation established from the measurements of carbon monoxide and smoke opacity is presented.
Three-Dimensional Forced Air Cooling System Analysis of a Scooter Engine
Authors: Carnevale Ennio , Migliorini Giacomo , Zecchi Stefano , Olmi Bart
Published: February 2009

Internal combustion engines must match several requirements such as good efficiency and low fuel consumption rate; when they are applied on scooter they are subject to some other restrictions. Nowadays, both low pollutant emissions and low noise level are requested for this engine since scooters are usually city vehicles. To match these requirements several aspects must be investigated: one of these may be the cooling system. There are usually three cooling methods, i.e. free stream air cooling, liquid cooling and forced air cooling. The first one is usually not employed in scooter engines because of its arrangement inside the scooter body (due to functionality and aestheticism). The second one may present some plant complications caused by the heat exchanger and ducts. A forced air cooling system presents usually lower complication, lower weight and greater reliability. Nevertheless, in order to keep engine temperatures below lubricant and structural limit, high mass flow rate may be necessary since air has smaller coolant efficiency compared to liquids. Moreover cooling air, supplied by a fan, requires high pumping power which may be excessive at high rotational speed; the fan itself may produce excessive noise reducing comfort. Sometimes, it may be hard to define the air flow demands in order to properly cool the critical parts (i.e. cylinder head); poor design may result in an excessive air mass flow demand and high pressure losses. Consequently the fan requires an excessive power and emits high noise level. Proper coolant distribution around the cylinder and the engine head reduces the overall air mass flow demand, rising indirectly engine efficiency. Usually the geometry of a forced air cooled engine is quite complex because of fins and other internal passages. To study coolant distribution and heat transfer a three-dimensional approach is then required. Computational fluid dynamic calculations, provided by commercial codes, can give useful suggestions about flow distribution around a finned cylinder. This paper will show an analysis of a typical air cooled scooter engine. Air mass flows and cooling efficiency are shown at several engine rotational speeds.
An Application of Multi-Criteria Genetic Algorithms to the Optimization of a Common-Rail Injector
Authors: de Risi Arturo , Donateo Teresa , Laforgia Domenico
Published: February 2009

The aim of the present investigation is to optimize the injection profile and the time response of a high pressure common rail injection system by adjusting the geometric and dynamic characteristics of an electronically controlled injector. The optimization method is based on the use of genetic algorithms which include the operators of crossover, mutation and elitist reproduction. As evaluation function for the GA a 1D simulation code of the injection systems, developed and extensively tested by the authors, has been used. The 1D model is based on the concentrated volume method and includes the effect of friction on the dynamics of the movable parts. Cavitation is also taken into account by the code as well as the effect on pressure wave propagation of the air and vapor mass fraction in the fuel. Conservation equations are integrated by using the characteristic method. The electromagnetic force generated by the solenoid on the head of the injector is simulated with an empirical function obtained by fitting experimental data. The optimized injection profile was defined by evaluating the predicted performance of a small bore DI diesel engine in terms of Brake Mean Effective Pressure (BMEP), soot and NOx emissions using a modified version of the KIVA-3V code. For the definition of the best injection profile injected quantity and start of injection were kept constants and only single-injection strategies were considered. The geometric and dynamic parameters (i.e. spring stiffness) of a commercial five holes VCO injector were used as baseline case. An optimized configuration of the selected parameters has been found. The optimized combinations of the investigated parameters are compared with the original values of the commercial injector as well as their predicted performance on the engine application.
Analysis of Low Cycle Liner Flange Fatigue in Locomotive Engines
Authors: Herdin G. R. , Tomsik H. , Katzmann B. , Gatterer F. , Traunbauer J.
Published: February 2009

In locomotive diesel engines the cracking of the flange of the cylinder liner is well known as a cause of failure. As a result of installing a new engine in an older type locomotive of the O¨BB (Austrian Federal Railways, locomotive type 2143) by Simmering-Graz-Pauker AG (SGP), and after running distances up to 250,000 km individual cases of liner flange cracks occurred that were not explainable prior to detailed measurements. Through the take-over of this particular engine series by Jenbacher AG and the usage of this type of engine in another locomotive type (O¨BB type 2068), this problem was not experienced. As a result of the problems with the older type locomotive, the firms ECS, JAG and O¨BB carried out a mutual research project aimed at solving this problem. Besides FEA calculation methods, very complicated strain gauge measurements (in the fillet of the flange) were carried out on the locomotive during various operational modes and then analyzed. The cause was a low cycle fatigue brought about primarily by the particular type of cooling system in combination with the very stiff construction of the crankcase. This publication focuses especially on the transient load of locomotive operation affecting the stress of the liner flange.
Simulation of the Airflow Characteristics of a Two-Stroke Natural Gas Engine With an Articulated Crank
Authors: Adair J. , Kirkpatrick A. , Olsen D. B. , Gitano-Briggs H.
Published: February 2009

The topic of this paper is the simulation of the airflow characteristics of a large bore two stroke natural gas fueled engine. The modeling was performed with the program WAVE, a computer code developed for engine cycle simulations. The engine studied was a four cylinder Cooper GMV engine. This engine has an articulated crankshaft connecting even and odd bank cylinders. Due to the articulation, the even bank cylinders have different piston profiles, port profiles, and compression ratios than the odd bank cylinders. Due to the non-symmetric timing and articulated geometry of the odd and even banks, the gas flow processes are not the same for each cylinder bank. The different manifold and port pressure profiles result in different amounts of trapped mass in the odd and even banks. The even bank is predicted to have a smaller amount of trapped mass and slightly lower trapping and scavenging efficiencies. Finally, the model predicts that the even bank cylinders attain higher maximum temperatures, which would produce increased NOx.
Analysis and Modeling of Plain Open Ends and Bends Inside the Piping Systems of Internal Combustion Engines
Authors: Chalet David , Chesse Pascal , Hetet Jean-Franc¸ois , Inozu Bahadir , Roy Philippe
Published: February 2009

Controlling the pressure wave propagation inside the inlet and exhaust systems of internal combustion engines is essential for the optimization of the cylinder filling and emptying as well as the combustion process. In this objective, the authors have been developing a new one-dimensional simulation code for several years. This paper presents an investigation of plain open end boundary conditions and bend elements. First, the pressure waves at the pipe inlet are analyzed with the Fluent CFD code. It appears that the losses can be modeled with the use of a coefficient that depends on the Mach number as well as the ratio between the pipe diameter and thickness. Then, the paper focuses on the modeling of bends. The losses in this type of elements can be modeled by the addition of a friction factor in the gas dynamics equations. This factor depends on the bend angle and the ratio between the tube radius of curvature and diameter. Finally, an experimental study aimed at evaluating the accuracy of the 1D simulation code is presented. The code enhancements significantly improve flow calculations and allow for the optimization of the inlet and exhaust systems of internal combustion engines.