bluuebunny/crossref_metadata_2025 huggingface dataset:
PADRAM: Parametric Design and Rapid Meshing System for Turbomachinery Optimisation
Authors: Shahpar Shahrokh , Lapworth Leigh
Published: February 2009

A parametric design system suitable for inclusion in an automatic optimization process is presented. The system makes use of a multi-block structured grid generation system specially designed for the rapid meshing of two-dimensional, quasi-three-dimensional, and three-dimensional single passage as well as multi-passage, multi-row turbomachinery blades. Full annulus viscous meshes of the order of five to ten million mesh points for the complete bypass assembly of the low pressure compression (LPC) system can be generated in a matter of minutes. PADRAM offers a major new design capability where the optimisation of multi-passage three-dimensional blades and its circumferential pattern is done simultaneously in one system. Successful usage of PADRAM in a number of design, optimisation and analysis applications has recently been demonstrated and reported herein.
Development of the 8000 kW Class Hybrid Gas Turbine
Authors: Nagata Hitoshi , Karasawa Wataru , Ichikawa Yoshihiro , Tsuruzono Sazo , Fukudome Takero
Published: February 2009

Based on the successful result of the Japanese national project for 300 kW class ceramic gas turbine development (this project was finished in March 1999), the New Energy and Industrial Technology Development Organization (NEDO) contract project “Research and Development on Practical Industrial Co-generation Technology”, funded by the Ministry of Economy, Trade and Industry (METI), started in August 1999. This project is a five-year plan until the end of the 2003 fiscal year. The objective of this project is to encourage prompt industrial applications of co-generation technology that employs a hybrid gas turbine (HGT; using both metal and ceramic parts in its high-temperature section) by confirming its soundness and reliability. The development activities are performed through ceramic material evaluation test and long-term operation test for the HGT of the medium size (8,000-kW class). It is expected that the development can realize low pollution and reducing the emission of CO2 with highly efficient use of energy. To grasp the material characteristic of the ceramic, the tensile creep rupture test, cyclic fatigue test, sub-critical crack growth test, and exposure test had been carried out. Sub element tests, such as Sector Model Text and Pre-test were carried out prior to the operation study. The operation study was started in the 2002 fiscal year. The operation tests to 5/8-load (about 5,000-kW) had been carried out as of February 2003. This paper gives the progress of the developments of the HGT.
Intermittency Transport Modeling of Separated Flow Transition
Authors: Vicedo J. , Vilmin S. , Dawes W. N. , Savill A. M.
Published: February 2009

An intermittency transport model is proposed for modeling separated-flow transition. The model is based on earlier work on prediction of attached flow bypass transition and is applied for the first time to model transition in a separation bubble at various degrees of free-stream turbulence. The model has been developed so that it takes into account the entrainment of the surrounding fluid. Experimental investigations suggest that it is this phenomena which ultimately determines the extent of the separation bubble. Transition onset is determined via a boundary layer correlation based on momentum thickness at the point of separation. The intermittent flow characteristic of the transition process is modeled via an intermittency transport equation. This accounts for both normal and streamwise variation of intermittency and hence models the entrainment of surrounding flow in a more accurate manner than alternative prescribed intermittency models. The model has been validated against the well established T3L semicircular leading edge flat plate test case for three different degrees of free-stream turbulence characteristic of turbomachinery blade applications.
Fault Diagnosis of Combined Cycle Gas Turbine Components Using Feed Forward Neural Networks
Authors: Camporeale S. , Dambrosio L. , Milella A. , Mastrovito M. , Fortunato B.
Published: February 2009

A diagnostic tool based on Feed Forward Neural Networks (FFNN) is proposed to detect the origin of performance degradation in a Combined Cycle Gas Turbine (CCGT) power plant. In such a plant, due the connection of the steam cycle to the gas turbine, any deterioration of gas turbine components affects not only the gas turbine itself but also the steam cycle. At the same time, fouling of the heat recovery boiler may cause the increase of the turbine back-pressure, reducing the gas turbine performance. Therefore, measurements taken from the steam cycle can be included in the fault variable set, used for detecting faults in the gas turbine. The interconnection of the two parts of the CCGT power plant is shown through the fingerprints of selected component fault models for a power plant composed of a heavy-duty gas turbine and a steam plant with a single pressure recovery boiler. The diagnostic tool is composed of two FFNN stages: the first network stage is addressed to pre-process fault data in order to evaluate the influence of the single fault variable on the single fault condition. The second FFNN stage detects the fault conditions. Tests with simulated data show that the the diagnostic tool is able to recognize single faults of both the gas turbine and the steam plant, with a high rate of success, in case of full fault intensity, even in presence of uncertainties in measurements. In case of partial fault intensity, faults concerning gas turbine components and the superheater, are well recognized, while false alarms occur for the other steam plant component faults, in presence of uncertainties in data. Finally, some combinations of faults, belonging either to the gas turbine or the steam plant, have been examined for testing the diagnostic tool on double fault detection. In this case, the network is applied twice. In the first step the amount of the fault parameters that originate the primary fault are estimated. In the second step, the diagnostic tool curtails the contribution of the main fault to the fault parameters, and the diagnostic process is reiterated. In the examined fault combinations, the diagnostic tool was able to detect at least one of the two faults in about 60% of the cases, even in presence of uncertainty in measurements and partial fault intensity.
Closed Loop Performance of a Slotless Lorentz Self-Bearing Motor
Authors: Chin Hooi-Mei , Stephens L. Scott
Published: February 2009

In previous work the authors presented a Lorentz self-bearing motor design targeted for precision pointing and smooth angular slewing applications. The motor also offers potential advantages when operated as a synchronous machine at high speed including larger power densities and shorter shafts. In this paper, the closed loop performance of the motor at low transient speeds (0–588 rpm) is presented. Using these results, several challenges to achieving high-speed rotation are identified and discussed. The most significant is the heavy cross coupling within the actuator which limits bearing stiffness and stability, and is amplified at rotor natural frequencies resulting in potential loss of levitation when passing through critical speeds. Of particular interest is the discovery of a significant cross coupling effect between the radial and tangential directions. A theory is put forth explaining this effect.
Experimental Construction of Reduced Mathematical Models of Rotating Equipments in Operation
Authors: Goncalves D. E. , Sanjuan J. D. , Di´az S. E. , Pacheco M.
Published: February 2009

An experimental method is proposed to obtain simplified mathematical models of rotating equipment systems. The Instrumental Variable Filter (IVF) method is applied to estimate mass, damping and stiffness force coefficients within a frequency range, through experimental measurements. This method is based on the least squares approximation technique and it uses analytical weight functions to reduce the effect of noise in the measurements. The experimental data is obtained for different configurations of rotating equipments, which consist of rigid wheels, a flexible shaft supported by bushing bearings, an electrical motor, a base-plate, and a concrete foundation. Frequency response functions (FRF) were obtained by impact excitation techniques. In the tests, the unbalanced response measurements were compared with the ones predicted by the IVF model. The method allows the study of mass, damping and stiffness force coefficients as a function of excitation frequency. Linearities and non-linearities of phenomena are identified, and the method sums up all the individual components into a definition for the system. The tests were conducted by operating, or not, the motor, in order to evaluate the IVF method in both cases. The high correlation between the IVF (FRF, and unbalance responses) and the actual measurements of the FRF and unbalance responses, shows that the method generates useful mathematical models of dynamic systems, that can have industrial applications. Modal analysis methods were used to compare the natural frequencies and the damping ratios, obtained by dynamic coefficients estimation.
Validation of Diagnostic Data With Statistical Analysis and Embedded Knowledge
Authors: DePold Hans , Seigel Jason , Volponi Allan , Hull Jonthan
Published: February 2009

The method described in this paper is intended to improve data stability and reduce dispersion of a given parameter signal by replacing any point deemed to be noise (e.g. an outlier) with an estimate of the parameter based on its recent history. This method determines a point is an outlier by utilizing learning and analytical elements that automatically adjust to the dispersion of the input data and automatically model the underlying process. The analytical elements of this method contain two types of embedded knowledge. The first is physics based engineering knowledge based on known interrelationships between the parameters to provide evidence when a parameter data point is physically unexplainable. It also contains the rule-based knowledge of real gas turbine trend characteristics such as persistency, polarity, and monotonic direction. Once a parameter data point is suspected to be noise, the system validates that assessment with a persistency check. If no parameter trend shift is occurring, as determined by a lack of persistency, the parameter is deemed noise and is replaced with the parameter’s last good state. Persistency checks enable removing noise without obscuring shifts in data that could be occurring due to real system changes. The process is designed to decide within two points if a data point should be considered noise. The goal of the process presented here for improving the quality of gas generator data is to automatically replace all probable noise without distorting the underlying parameter signals. The metrics for success are a 25% reduction in the dispersion (e.g. scatter) of the data with no bias in the parameter central tendency (e.g. mean value), with no reduction the granularity of the parameter signal (visibility of anomalies), and with no delay in the detection of a real trend change.
Aerodynamic Blade Row Interactions in an Axial Compressor: Part I — Unsteady Boundary Layer Development
Authors: Mailach Ronald , Vogeler Konrad
Published: February 2009

This two-part paper presents experimental investigations of unsteady aerodynamic blade row interactions in the first stage of the four-stage Low-Speed Research Compressor of Dresden. Both the unsteady boundary layer development and the unsteady pressure distribution of the stator blades are investigated for several operating points. The measurements were carried out on pressure side and suction side at midspan. In part I of the paper the investigations of the unsteady boundary layer behaviour are presented. The experiments were carried out using surface-mounted hot-film sensors. Additional information on the time-resolved flow between the blade rows were obtained with a hot-wire probe. The unsteady boundary layer development is strongly influenced by the incoming wakes. Within the predominantly laminar boundary layer in the front part of the blade a clear response of the boundary layer to the velocity and turbulence structure of the incoming wakes can be observed. The time-resolved structure of the boundary layer for several operating points of the compressor is analyzed in detail. The topic “calmed regions”, which can be coupled to the wake passing, is discussed. As a result an improved description of the complex boundary layer structure is given.
A New Method to Control High Temperature Corrosion in Gas Turbines Resulting From Alkali Sulfates
Authors: Schofield Keith
Published: February 2009

A quantitative program has been completed concerning the detailed chemistry of alkali sulfate deposition onto surfaces immersed in hot flame gases. It has been irrefutably proven that the process is heterogeneous. It is the surface and the alkali that are the predominant controlling features. It is insensitive to the sulfur or any of the flame parameters. The nature of the surface is not important and it uses the flame gases solely as a source of ingredients. Alkali speciation in the flame gases is irrelevant. The chemistry is rapid and shows no activation energy. Formation of sulfate appears to be driven largely by thermodynamic stability considerations. The alkali deposit that results depends on what is available in the hot flame gases. A preferential ranking is observed showing the pronounced trend of sulfate>chloride>carbonate>hydroxide. Consequently, additives have been sought and found that the alkali prefers to sulfur to in this way modify and control the deposition chemistry. It has been determined that the only such candidate species originate in the first few columns of the transition elements. Of these, salts of niobium, tantalum, molybdenum and tungsten are successful. Molybdenum and tungsten salts are the more readily available. When these are added to the burned gases at a concentration twice that of the alkali, on an atomic basis, it is observed that no alkali sulfate or chloride is formed. Instead benign alkali polymolybdates or polytungstates are produced. It appears reasonable to expect similar behavior on thermal barrier coatings.
Aircraft Gas Turbine Soot Emission Tests Under Technical Relevant Conditions in an Altitude Test Facility and Validation of Soot Measurement Technique
Authors: Wahl Claus , Aigner Manfred
Published: February 2009

An aircraft gas turbine was tested in an altitude test facility under technical relevant flight conditions. Test points are the ICAO power settings IDLE, TAKE OFF, CLIMB and DESCENT, as well as CRUISE conditions. The used measurement techniques are Scanning Mobility Particle Sizer (SMPS) [1] and Scanning Electron Microscopy (SEM). It is shown, that the relative Soot Emission Index (compared to take off conditions) is increasing with power setting. The mean diameter of the particles is also increasing with power setting. The particles show a lognormal size distribution for most of the test points. Under TAKE OFF conditions (100% power setting) we found a bimodal size distribution. The SEM pictures show the fractal character of the soot particles with 10 to 15nm primary particles as well as the agglomerates. To validate the measurement techniques a variable soot generator [2] for nanoparticles was developed. This soot generator was used to check sample line losses. In an additional experiment we used this soot generator to test the trapping efficiency of the recommended filters for the so called ICAO Smoke Number which is the same as SAE – Smoke Number [3] or EPA – Smoke Number [4].
A Potential Oxide/Oxide Ceramic Matrix Composite for Gas Turbine Applications
Authors: Go¨ring Ju¨rgen , Kanka Bernd , Schmu¨cker Martin , Schneider Hartmut
Published: February 2009

WHIPOX® (Wound Highly Porous Oxide CMCs) are oxide/oxide composites which are composed of highly porous alumino silicate or alumina matrices and of alumino silicate (Nextel 720, 3M) or alumina (Nextel 610, 3M) fibers. The materials are fabricated by a computer-controlled winding technique, developed at DLR. After eventual forming and joining steps, the green prepegs are pressureless sintered in air at 1300°C. The high temperature behavior of the CMCs is mainly controlled by the thermo-mechanical properties of the oxide fibers. For long-term use (>10,000 h) an application limit for the composite of about 1100°C is expected. It can, however, be improved by external thermal barrier coatings up to a maximum surface temperature of 1300°C. Gas burner tests show that the composites are extremely resistant against thermal fatigue. Therefore it is a material with a high potential for the use under the long-term high temperature conditions of gas turbine engines.
Comparison of Rotordynamic Analysis Predictions With the Test Response of Simple Gas Hybrid Bearings for Oil Free Turbomachinery
Authors: Wilde Deborah A. , San Andre´s Luis
Published: February 2009

Current applications of gas film bearings in high-speed oil-free micro-turbomachinery (<0.4 MW) require calibrated predictive tools to successfully deploy their application to mass-produced systems, for example oil-free turbochargers. The present investigation details the linear rotordynamic analysis of a test rotor supported on externally pressurized gas bearings. Model predictions are compared with the test rotordynamic response determined through comprehensive experiments conducted on a small rotor supported on three lobed hybrid (hydrostatic/hydrodynamic) rigid gas bearings. Predictions for the rotor-bearing system synchronous response to imbalance show good agreement with measurements during rotor coast downs, and manifest a decrease in damping ratio as the level of external pressurization increases. The rotor-bearing eigenvalue analysis forwards natural frequencies in accordance with the measurements, and null damping ratios evidence the threshold speeds of rotordynamic instability. Estimated whirl frequency ratios are typically 50% of rotor speed, thus predicting sub synchronous instabilities at lower rotor speeds than found experimentally when increasing the magnitude of feed pressurization. Rationale asserting the nature of the discrepancies calls for further analysis.
Analysis of Singas FED Gas Turbine Performance Depending on Ambient Conditions
Authors: Brusca S. , Lanzafame R.
Published: February 2009

It is well known that gas turbine performance is quite influenced by ambient conditions such as pressure, air temperature and relative humidity. This paper deals with the effects of ambient conditions on performance of gas turbine fired with syngas. A mathematical model of the engine has been implemented within GateCycle workspace and using experimental data, it has been finely tuned and tested. Results analysis showed that it is able to simulate engine running in on–design and off–design conditions (maximum relative error is about 1%). Thus, gas turbine running simulations depending on ambient temperature and relative humidity have been carried out. Results analysis showed that at high air temperatures (higher then the one corresponding to maximum IGV opening) performance reduction occur. On the contrary, high values of relative humidity allow to reduce power losses in the same temperature range. In conclusion, the developed mathematical model is able to simulate gas turbine running with low relative errors. So that, it could be used in order to optimise engine performance at the ambient conditions that occur for the site of the IGCC Complex in which gas turbine is integrated.
Recession Rate Prediction for Ceramic Materials in Combustion Gas Flow
Authors: Yuri Isao , Hisamatsu Tohru
Published: February 2009

The influence of various basic factors of combustion gas flow conditions on the recession rate of silicon nitride, silicon carbide, and alumina has been experimentally clarified, and the recession rate equation is deduced using the dependence of influential factors on the recession rate and the mass transfer theory. The exposure tests are performed under various gas flow conditions (T = 1100–1500 °C, P = 0.3–0.7 MPa, V = 40–250 m/s, PH20 = 30–120 kPa, PO2 = 20–45 kPa). Recession rates mainly depend on water-vapor partial pressure, pressure, gas temperature, and Reynolds number in the gas flow conditions inside the specimen holder. The dependent on oxygen partial pressure is extremely low for silicon nitride and silicon carbide. The recession rates of silicon nitride, silicon carbide, and alumina in combustion gas flow are expressed in the form exp(−E/RT)·(PH20)n· Re0–8/P, and the predicted recession rates of silicon nitride shows good agreement with reported exposure test results under gas turbine conditions.
Leading Edge Modification Effects on Turbine Cascade Endwall Loss
Authors: Becz S. , Majewski M. S. , Langston L. S.
Published: February 2009

Experimental results are presented which provide area-averaged total pressure loss coefficient measurements for four different turbine airfoil leading edge configurations. A baseline (Langston) configuration, two leading edge bulbs, and a leading edge fillet were tested in a large-scale, low aspect ratio, high turning linear cascade. Results show that both the small bulb and fillet geometries each reduced area averaged total loss by 8%, while the large bulb exhibited a slight increase in total loss. Contour plots for all geometries are presented and the major differences between each are discussed. Through investigation of pitch averaged loss profiles it is found that the area of greatest reduction differs between the small bulb and fillet, leading to the possibility that the mechanisms through which each is affecting the flow may be different. This provides hope that the best features of each may potentially be combined to determine an optimum shape for secondary flow loss reduction.
The Evaluation of CFCC Liners After Field Testing in a Gas Turbine – IV
Authors: Kimmel Josh , Price Jeffrey , More Karren , Tortorelli Peter , Sun Ellen , Linsey Gary
Published: February 2009

Under the Ceramic Stationary Gas Turbine (CSGT) and Advanced Material Program sponsored by the U.S. Department of Energy (DOE), a team led by Solar Turbines Incorporated (Solar) has successfully designed engines utilizing silicon carbide/silicon carbide (SiC/SiC) continuous fiber-reinforced ceramic composite (CFCC) combustor liners. Their potential for low NOx and CO emissions was demonstrated in nine field-engine tests for a total duration of more than 52,000-hours. In the first four engine tests, the durability of the liners was limited primarily by the long-term stability of SiC in the high steam environment of the gas turbine combustor. Consequently, the need for an environmental barrier coating (EBC) to meet the 30,000-hour life goal was recognized. An EBC developed under the National Aeronautics & Space Administration (NASA) High Speed Civil Transport, Enabling Propulsion Materials program was improved, optimized and applied on the SiC/SiC liners by United Technologies Research Center (UTRC) from the fifth engine test onwards. The results of the evaluation after the seventh engine test with greater than 15,000-hours is compared against the results of a previous engine test with approximately 14,000-hours.
Optimizing the Vane-Endwall Junction to Reduce Adiabatic Wall Temperatures in a Turbine Vane Passage
Authors: Lethander Andrew T. , Thole Karen A. , Zess Gary , Wagner Joel
Published: February 2009

Secondary flows in airfoil passages have become increasingly important in the design of modern gas turbines due to several fundamental trends in gas turbine engine development. Driven to achieve higher engine efficiencies and specific thrust output, the gas turbine industry is continually pushing the envelope of maximum allowable turbine inlet temperature. While many researchers have worked to gain an understanding of secondary flows and their effects on turbine heat transfer, very few have pursued ways to passively mitigate their detrimental effects. While considerable attention has been given to techniques of secondary flow reduction in order to minimize the associated aerodynamic losses, the objective of this study was to improve the thermal environment for a turbine vane. In particular, this objective was achieved through optimizing a fillet in the vane-endwall juncture to minimize adiabatic wall temperatures. The approach taken was to employ a commercial optimization software package in conjunction with a computational fluid dynamics (CFD) package in the design of the fillet. Results indicate that a significant reduction in adiabatic wall temperatures can be achieved through application of an optimized fillet.
A Unique Solution to Low Cost SOFC Hybrid Power Plant
Authors: Agnew Gerry D. , Moritz Robert R. , Berns Colin , Spangler Alan , Tarnowski O. , Bozzolo Michele
Published: February 2009

The inherently clean and efficient nature of fuel cell systems makes them highly attractive for electrical power generation applications, subject to overcoming their disadvantage of high initial cost. Rolls Royce has been working for 10 years to create a fuel cell stack design of much lower cost, having a structure both tolerant to sharp changes in operating temperature and fully durable when used in load-following applications requiring moderate cycling of stack conditions. The effort was launched as a company supported research initiative but has also attracted substantial European Commission funding, with emphasis on developing low manufacture cost stack technologies. This paper describes how chemical and physical features of the stack, and the technologies selected for the integrated plant system, have achieved major strides in cost reduction. The design and development of the system using this technology has been transitioned to an European/USA industry development team whose goal is commercialization of the product within five years. Manufacture will use both European and USA facilities. Market opportunities for fuel cell hybrids are briefly discussed.
HSCT Forward Swept Fan Performance
Authors: Neubert Robert J. , Gendrich Charles P.
Published: February 2009

Previous experimental and analytical studies have demonstrated the potential for significant improvements in efficiency and stall margin with forward swept rotor blading. This paper extends the assessment to a light weight, low noise two stage fan designed and fabricated under the NASA High Speed Civil Transport program. The experimental investigation evaluates the effect of forward sweep on efficiency and stall margin relative to the predicted levels for a radial fan designed for the same requirements. Efficiency was above multi-stage fan state of the art and stall margin was significantly greater than predicted based on radial fan experience. In addition, the effects of increasing the axial gap between the IGV and rotor 1, as well as R1 to S1 axial gap are evaluated. The increased axial gap between R1 & S1 had a much greater effect on performance than increasing the IGV to R1 gap. And, 3D Navier-Stokes flow solver analysis was performed for comparison to test results.
Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach
Authors: Dogu Yahya
Published: February 2009

The flow behavior through a brush seal has been investigated by developing a flow analysis procedure with a porous medium approach. In order to increase the brush seal performance and use at more severe operating conditions, the complex flow in the bristle pack has become the major concern affecting seal features such as blow-down, hang-up, hysteresis and bristle flutter. In this study, an axi-symmetric CFD model is employed to calibrate anisotropic permeability coefficients for the bristle pack based on available experimental data; leakage, axial pressure on the rotor surface and radial pressure on the backing plate. A simplified form of the force balance equation is introduced for the flow in the porous bristle pack. Different sets of permeability coefficients are defined for fence height region below the seal backing plate and the upper region of the seal to correlate the different physical structures and behavior of these regions during operation. The upper region is subject to more stiffening due to backing plate support while fence height region is free to spread and bend in the axial direction. It is found that flow resistance for upper region should be 20% higher than fence height region in order to match the experimental pressure within the bristle pack. Analysis results prove that the brush seal is well represented as a porous medium with this approach. Based on the model developed, characteristic flow and pressure fields in the entire bristle pack have been explored.
A Review of Some Early Design Practice Using CFD and a Current Perspective
Authors: Horlock J. H. , Denton J. D.
Published: February 2009

In the early development of gas turbines, many empirical design rules were used; for example in obtaining fluid deflection using the deviation from blading angles, in the assumption of zero radial velocities (so-called radial equilibrium) and in expressions for clearance loss (the Lakshminarayana formulae). The validity of some of these rules, and the basic fluid mechanics behind them, is examined by use of modern ideas and CFD codes. A current perspective of CFD in design is given, together with a view on future developments.
Some Basic Elements to Achieve a Future 1D Simulation of Wave Propagation in I.C.E. Pipes
Authors: Chalet David , Chesse Pascal , Hetet Jean-Franc¸ois , Tauzia Xavier
Published: February 2009

The assumption of one-dimensional unsteady flows in the inlet and exhaust systems of turbocharged diesel engines is widely used although multi-dimensional simulations using fluid dynamics are also possible. However, difficulties persist concerning the boundary conditions, particularly at the pipe ends (inflow or outflow) and at the intra-pipe boundary conditions (sudden or gradual area changes, bends, junctions, etc.). This paper focuses on the two first steps leading to a 1D flow simulation code: the selection of a numerical scheme and the study of an open end boundary condition. The first section compares several numerical algorithms, including Lax-Wendoff, Flux-Corrected-Transport methods (FCT), and Harten-Lax-Leer (Riemann solver), extended to the second order. The selection criterion is the best compromise between numerical instabilities and computational time. A numerical study using the Fluent CFD code is then presented on a constant area duct in order to determine some characteristics at the pipe end, specifically the dead zone length and the throat area. Finally, a model parameterized by the pressure ratio between inlet and outlet is proposed.
A “Hot and Cold” Experimental Analysis of Flow Distribution in a “Close Coupled” Catalytic Converter
Authors: Cardone M. , Cioffi V. , Fiorenza R. , Gaudino P. , Senatore A. , Torella E.
Published: February 2009

The tighter limits introduced by EURO3 and EURO4 regulations involve the adoption of exhaust configurations, in which the converter is located close to the manifold, in order to reduce light off time, and so to obtain lower emissions. This type of configuration introduces new problems relative to optimisation of the exhaust manifold geometry, which is no longer only linked to engine performance, but also has to guarantee the best possible operation of the exhaust gas treatment system. Critical parameters include lambda probe positioning and impingement of the gas flow, along with establishment of a flow field that corresponds to the catalytic converter intake area, as imposed by well known requests of reliability and functionality. The present work is aimed at integrated modelling and experimental optimisation of exhaust manifold geometry, with regard to oxygen sensor positioning and catalyst intake flow distribution, to find the best compromise between engine performance and exhaust emissions control.
Assessing Double Injection and Intake Air Temperature Effects on Gasoline HCCI Engine Performance and Emissions Using Fully-Automated Experiments and Micro-Genetic Algorithms
Authors: Canakci Mustafa , Hruby Eric , Reitz Rolf D.
Published: February 2009

Homogeneous charge compression ignition (HCCI) is receiving attention as a new low emission engine concept. Little is known about the optimal operating conditions for this engine operation mode. Combustion at homogeneous, low equivalence ratio conditions results in modest temperature combustion products, containing very low concentrations of NOx and PM as well as providing high thermal efficiency. However, this combustion mode can produce higher HC and CO emissions than those of conventional engines. An electronically controlled Caterpillar single-cylinder oil test engine (SCOTE), originally designed for heavy-duty diesel applications, was converted to a HCCI direct-injection gasoline engine. The engine features an electronically controlled low-pressure common rail injector with a 60°-spray angle that is capable of multiple injections. The use of double injection was explored for emission control, and the engine was optimized using fully-automated experiments and a micro-genetic algorithm (μGA) optimization code. The variables changed during the optimization include the intake air temperature, start of injection timing, and split injection parameters (percent mass of the fuel in each injection, dwell between the pulses). The engine performance and emissions were determined at 700 rev/min with a constant fuel flow rate at 10 MPa fuel injection pressure. The results show that significant emissions reductions are possible with the use of optimal injection strategies.
Effects of Coolant Temperature on the Performance and Emissions of a Diesel Engine
Authors: Abdelghaffar Waleed A. , Osman Mohsen M. , Saeed Mohamed N. , Abdelfatteh Abdelfattah I.
Published: February 2009

Experiments were conducted on a four-cylinder, four-stroke, direct-injected diesel engine to study the effects of engine coolant temperature on both performance parameters and exhaust emissions. The energy balance is discussed on the bases of first-law analysis and second-law analysis. The range of speed investigated was 1000–2000 RPM for the torque range of 25–152 N.m. The coolant temperature was varied from 50 to 95 °C. The present study shows that the coolant temperature has a significant effect on the volumetric efficiency. It also shows that increasing coolant temperature decreases the mass flow rate of fuel consumption and the cooling losses. As a result, the brake specific fuel consumption decreases and the brake thermal efficiency increases. A chart was developed for showing the relationship between the coolant temperature, equivalence ratio, brake torque, and brake specific fuel consumption. The study shows that the coolant temperature has a significant effect on NOx emissions and minor effects on the volumetric percentages of oxygen, carbon dioxide, and carbon monoxide. The unburned hydrocarbons show insignificant variation. This work also shows that increasing coolant temperature slightly increases the availability of the coolant and decreases the total availability losses.
Crankshaft Torsional Vibration Characteristics in a Vee-Type Six-Cylinder Diesel Engine
Authors: Kimura Jouji , Kobayashi Shinichirou , Shiono Kazuhiro
Published: February 2009

Engines have been designed to avoid low-harmonic-order resonant torsional vibration in a commonly-used engine speed range, but the authors have found that, in some engines, especially turbo-charged engines, a significant degree of a low-harmonic-order exciting torque acts on the crankshaft. In these engines, the amplitude of non-resonant low-harmonic-order torsional vibration is almost as large as that of the resonant one and the amplitude of non-resonant vibration can not be controlled by a damper. Accordingly, to investigate the characteristics of non-resonant low-harmonic-order torsional vibration is important. This paper describes the characteristics of non-resonant and resonant torsional vibration for a vee-type six-cylinder diesel engine.
Crank-Angle Resolved Oilfilm Thickness Measurement Between Piston Ring and Cylinder Liner in a Spark Ignition Engine
Authors: Weimar Hans-Joachim , Spicher Ulrich
Published: February 2009

A new measuring technique has been developed in order to determine the oilfilm thickness between piston ring and cylinder liner in a combustion engine by use of laser-induced fluorescence (LIF) technique. In clear contrast to further investigations, where optical probes have been mounted at a fix position in the cylinder liner allowing single measurements at defined times of the piston stroke, only, the optical probes used in the presented work are mounted in the piston and the piston ring. Fiber optics, led via a grasshopper-link, carry the exciting laser radiation (λ = 488 nm) to the probes and backwards the fluorescence radiation (λ ∼ 540 nm) to a photomultiplier. Thus, the developed measuring system allows a continous, crank-angle resolved measuring of the oilfilm thickness. As the LIF-technique is a relative measuring technique, calibration work, especially in the combustion engine, had to be done. Using eddy current sensors at a fix position in the cylinder liner the oilfilm in a single point could be determined. Grooves of defined depth in the cylinder liner provided the fluorescence signal amplification in each stroke so that adverse influences of oil pollution or temperature could be eliminated. A method has been developed to eliminate transmission influences contributed to the grasshopper link system. The measuring technique adapted to a single-cylinder SI engine has been tested under motored and fired conditions. Parameters under motored conditions were engine speed, oil- and coolant-temperature and throttle position. Experiments under fired conditions (part load) have been done varying oil and coolant temperature. Correlations between oilfilm thickness and HC-emissions under motored conditions have been found. Incylinder pressure, oil-temperature and engine speed are the most influencing parameters.
Experimental Results From a Two-Stroke Gasoline Direct-Injected Engine Prototype
Authors: Bartolini Carlo Maria , Caresana Flavio , Pelagalli Leonardo
Published: February 2009

Recently, research on internal combustion spark-ignited engines has focused increasingly on charge control by means of direct injection. The concepts proposed in this field involve in most cases high-cost systems which do not seem to be widely applicable, especially to small, low-cost engines. In this respect, the challenge is to avoid complicating the existing power systems that make of simplicity and low cost their better qualities. The paper reports on the design and realization of a two-stroke gasoline direct-injection engine prototype which employs a Water-Hammer effect injection system. The experimental data obtained with the prototype are presented showing how the system significantly reduces hydrocarbon emissions and specific fuel consumption.
A Fluid Model for Simulation of Diesel Injection Systems in Cavitating and Non-Cavitating Conditions
Authors: Dongiovanni Claudio , Negri Claudio , Roberto Roberta
Published: February 2009

This paper presents a new fluid mathematical model for the numerical simulation of a hydraulic system that can work in cavitation. The fluid model proposed allows to obtain physical properties, such as density, bulk modulus, void fraction and sound speed, of a liquid-vapor-gas mixture so that the mixture itself can be treated as a homogeneous fluid. Thanks to the relationships proposed by the authors, it is possible to study a fluid system while in any operating condition (i.e. in cavitating or in non-cavitating conditions) using the same fluid-model and a unique set of equations. The model takes into consideration the evolution of the vapor and gas bubbles as a consequence of pressure and temperature variations, and its parameters are the physical properties of the mixture components, i.e. liquid, vapor and dissolved gas. The model was applied in the numerical analysis of diesel injection systems. The conservation laws that describe the fluid flow along the pipes were discretized by means of a semi-discrete finite volume method of second-order accuracy both in space and time. The algebraic system obtained was finally solved by means of a predictor-corrector fully implicit iterative method. The algorithm described was tested for several injection-system operative conditions. Such conditions involve high pressure as well as cavitation phenomena.
Impact of Fuel Preparation System on Combustion Process and Exhaust Emissions
Authors: Pischinger S. , Umierski M.
Published: February 2009

In the past decade, the quality of Heavy Fuel Oil (HFO) has not improved or even declined in general. The progress in refinery techniques allowed to use a higher percentage of the crude oil for light fuels and other components. Therefore, the concentration of heavy components and agglomerates in the residual fuel increased. On the other hand, a better exhaust quality without compromising the superior fuel consumption of HFO-fuelled engines can only be gained by improved fuel injection. High injection pressures, rate shaping and electronic control of injection timing as well as new injection techniques like Common-Rail will be common features of engines for the next decades. Unfortunately, electronic controlled unit pumps and moreover, Common Rail systems are very sensitive to fuel quality, especially the content of water, sediments, agglomerates and other sludge. If ran on fuel processed by today’s fuel preparation system, wear would be excessive or damages will take place. On the other hand, if conventional on-board purification is intensified, the percentage of fuel deposit will rise and lower the over-all efficiency. To observe effects of fuel composition, a single cylinder research engine (250 mm bore/320 mm stroke) is fuelled by HFO in typical operation modes including different speeds and loads. Diesel fuel was also used to compare the results with another fuel of e.g. different sulphur content to separate effects on particulate matter. The high, typical sulphur content of the used HFO of about 3% increases the particulate matter; approx. 30% are sulphur products. The Soluble Organic Fraction (SOF, unburned fuel and oil) of PM is significantly higher compared to diesel fuel (50...70% to 10%). This impacts the particulate size distribution as well: although the main fraction of particulates consist of a size from 100...400nm for diesel and HFO, the number of small particulates (approx. 50 nm) is different, depending on the Sulphur content as this size consists of small condensates; therefore, the number may also be impacted by ambient air humidity. By use of different components for fuel preparation, the size, distribution and content of agglomerates can be impacted, but re-agglomeration occurs fast within minutes and must be taken into account. The differences in agglomerates does not result in a different total exhaust particulate mass. The slight effects found within the test are not significant and are in addition to that affected by ambient conditions. The fuel preparation, especially the use of homogenization equipment, needs more development efforts. For example, a mechanical homogenization apparatus can crack agglomerates and improve fuel homogeneity, but may fail to bring the size of agglomerates to a dimension that the filter is relieved.
Transient and Unstable Torsional Vibrations on a 4-Stroke Marine Diesel Engine
Authors: Lee D. C. , Yu J. D.
Published: February 2009

Under steady state condition, unstable torsional vibration normally does not occur in shafting systems using 4stroke diesel engine due to hysteresis damping of shafting system and relative damping of standard fitted damper. However, the unstable torsional vibration occurs on marine propulsion shafting systems due to slippage of a multi-friction clutch installed between increasing gear box and shaft generator. To identify this unstable vibration and make proper counter measure, the simulation for transient torsional vibration using the Newmark method is introduced in this paper. The mechanism of this unstable vibration is verified by vibration and noise measurements of the shafting system.
Investigation on Realizing Fuel Rate Shaping Using a Common Rail Injector
Authors: Carlucci Paolo , Ficarella Antonio , Giuffrida Antonio , Lanzafame Rosario
Published: February 2009

The present work deals with the first researches into the real capabilities of an electronically controlled injector for common rail systems in realizing a proper shaping of the fuel rate with particular reference to its rising profile. Injectors equipped with standard and geometrically modified control valves have been investigated in detail by means of computer modeling and simulation. Experiments have been carried out in order to validate the feasibility of such a shaping and the injection rate meter based on the method proposed by Bosch was used. The main result of this work is a noteworthy dependence of the fuel rate on geometrical modifications in the piloting stage of the injector, since a certain difference in the slope of the first part of the fuel rate has been attained. The injector model has been finally used to investigate further geometrical modifications to be realized in order to achieve the desired fuel rate shaping.
Firing Order Selection in Relation to Vibration Aspects
Authors: Ro̸nnedal Per , Nielsen Hans Bo̸je
Published: February 2009

Selecting the optimum firing order for a combustion engine is an important decision to make when developing an engine. Typically, the optimum choice is made on the basis of a weighted balance between a number of interrelated engine vibration characteristics, such as: balancing, free forces and free moments, guide force distribution, inner bending moments, bearing load, and torsional and axial vibration behaviour. Also gas dynamic properties making each cylinder do the same amount of work is considered. In addition to the traditional firing sequence selection, implying the same firing interval between cylinder units, also so-called irregular firing orders, characterized by different intervals between the individual firings, are considered. Various methods and strategies can be applied, considering that different engine applications exhibit completely different vibratory behaviour, e.g. marine propulsion plants compared with stationary installations. This paper will give examples relating to various applications for both two-stroke and four-stroke engines. Four-stroke: Realizing that the engine is often an integrated part of a complex system, it is demonstrated in this paper that analysing the whole system in terms of linear vibrations, the optimum firing order is different from the firing order determined with traditional methods. The system analysed here is a genset for marine or stationary application consisting of a 9-cylinder diesel engine, alternator and base frame. All three parts are bolted together as one unit, resiliently mounted on a ship or a land-based foundation. Two-stroke: The traditional 7-cylinder marine propulsion engine firing sequence is modified in order to be able to run safely directly at a two-node torsional resonance without installing a T/V damper. The 12-cylinder stationary engine has been modified so as to reduce installation costs and improve the coupled torsional-axial vibratory behaviour. The 10-cylinder marine engine firing sequence has been modified in order to achieve more favourable structural vibration characteristics.