bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Flux Sensor With Minimal Impact on Boundary Conditions
Authors: Saidi Arash , Kim Jungho
Published: December 2008

A technique for determining the heat transfer on the far surface of a wall based on measuring the heat transfer and temperature on the near wall is presented. Although heat transfer measurements have previously been used to augment temperature measurements in inverse heat conduction methods, the sensors used alter the heat flow through the surface, disturbing the very quantity that is desired to be measured. The ideal sensor would not alter the boundary condition that would exist were the sensor not present. The innovation of this technique in that it has minimal impact on the wall boundary condition. Since the sensor is placed on the surface of the wall, no alteration of the wall is needed. The theoretical basis for the experimental technique as well as experimental results showing the heat flux sensor performance is presented.
Scaling of Natural Circulation Boiling Systems
Authors: Iyer Kannan N. , Kadengal Aboobacker
Published: December 2008

This paper lays out the procedure for arriving at the dimensions of a model facility to simulate a pressure tube type reactor. The Advanced Heavy Water Reactor, whose design is being evolved in the Indian scenario, is used as a basis for the evolution of the model facility. The non-dimensional groups that need to be preserved are identified and the design is evolved by satisfying these non-dimensional groups. The inevitable distortions that get introduced are discussed and a suitable compensation procedure evolved. Finally, the evolved model is shown to satisfy both steady state and characteristic equation similarity.
Simulation of the Effect of Inlet Blocking on NO Formation in a Swirl Coal Combustor
Authors: Zhou L. X. , Zhang Y. , Zhang J.
Published: December 2008

To develop low-pollution burners, the effect of inlet blocking on NO formation in a swirl coal combustor is studied by numerical simulation. An algebraic unified second-order moment turbulence-chemistry model and a simplified Solomon model of HCN release for NO formation are proposed. These models are incorporated into a full two-fluid model of reacting gas-particle flows and coal combustion. The sub-models are the k-ε-kp two-phase turbulence model, the EBU-Arrhenius volatile and CO combustion model, the six-flux radiation model, coal devolatilization model and char combustion model. The effect of inlet blocking position on NO formation in a swirl coal combustor is studied. The predicted temperature, turbulence intensity, coal concentration and NO concentration were obtained. The prediction results for typical cases are in good agreement with the experimental results reported in references, indicating that the numerical models are appropriate. The prediction results indicate that the blocking between the primary-air flow and the secondary-air flow will increase the turbulence intensity, but increase the coal concentration and reduce the temperature in the near-inlet zone, hence can remarkably reduce the NO formation.
Braking System Cooling Time Simulation
Authors: Neto Luiz Tobaldini , Papa Ramon , de Castro Santos Luis C.
Published: December 2008

Aircraft braking pads are subject to an extremely severe thermal environment. During a typical landing the carbon brake pads can reach temperatures up to 700–800 K or even more. Between landings during the taxi and parking phase the brakes have to cool off back to their operational limits in a time interval consistent with the average operational time. In order to evaluate the impact of design modifications on the wheel mounting and fairings, without the need of extensive laboratory and flight campaigns, a CFD (Computational Fluid Dynamics) based methodology was developed. Due to the geometry complexity the need of a geometrically representative, but simplified model comes up, in order to capture the major features of the natural convection flow and temperature fields and can be used to evaluate the influence of design changes on the braking system cooling times. A calibration procedure is carried out, aiming a better representation of the transient phenomenon, using a thermal resistances setting up feature from the solver used. An example of the application of this methodology is presented. A computational grid of over 700,000 tetrahedral elements was constructed and the Navier-Stokes equations are solved using a commercial package (FLUENT). The computational cost for a time accurate solution demands the use of parallel processing in order to complete the analysis in a typical industrial environment timeframe. Comparison with both laboratory and flight data calibrate and validate the results of the computational model. This paper describes the details of the construction of the CFD model, the setting of the initial and boundary conditions and the comparison between measured and simulated parameters.
Time and Space Series Analysis of Spectral Radiation Intensities for a Partially Premixed Turbulent Flame
Authors: Zheng Yuan , Gore Jay P.
Published: December 2008

A recently developed technique called time and space series analysis was used to calculate the mean and fluctuating spectral radiation intensities leaving diametric and chord-like paths in turbulent partially premixed flames. A standard flame (Flame D) from Sandia Workshop on Turbulent Non-premixed Flames was selected to allow an evaluation of the radiation calculations at least at the single point statistics level. Measurements of spectral radiation intensities using a fast infrared array spectrometer provide an evaluation of the computations and also allow estimation of the length and time scales of scalar fluctuations, which appear as model parameters in the time and space series analysis modeling.
Numerical Solution of Ocular Fluid Dynamics in a Rabbit Eye
Authors: Kumar Satish , Acharya Sumanta , Beuerman Roger , Palkama Arto
Published: December 2008

Numerical calculations of the aqueous humor dynamics in the anterior chamber of a rabbit’s eye are presented to delineate the basic flow mechanisms. The calculations are based on a geometrical model of the eye, which represents the Trabecular mesh (TM) as a multi-layered porous zone of specified pore sizes and void fraction. The outer surface of the cornea is assumed to be at a fixed temperature (corresponding to the ambient temperature), while the iris surface is assumed to be at the core body temperature. Results are obtained for both the horizontal upward-facing orientation of the eye, and the vertical orientation of the eye. Parameters varied include: the pore size in the TM to understand how TM blockage influences the flow pattern and the intra-ocular pressure (IOP) distribution; the temperature difference between the iris and the cornea to underscore the important role of buoyancy in driving the aqueous humor flow; and, the pupil size reflecting different levels of ambient light. Buoyancy is observed to be the dominant driving mechanism for the convective motion in both orientations of the eye. Reducing the TM pore size does not appear to have a significant influence on the IOP until the pore size drops below 1 micron beyond which a significant increase in IOP is observed. Variations in the pupil size appears to have little influence on the IOP or flow distributions in view of the dominant role of buoyancy in controlling the flow motion.
Time and Space Resolved Heat Transfer Measurements Under Nucleate Bubbles With Constant Heat Flux Boundary Conditions
Authors: Myers Jerry G. , Hussey Sam W. , Yee Glenda F. , Kim Jungho
Published: December 2008

Investigations into single bubble pool boiling phenomena are often complicated by the difficulties in obtaining time and space resolved information in the bubble region. This usually occurs because the heaters and diagnostics used to measure heat transfer data are often on the order of, or larger than, the bubble characteristic length or region of influence. This has contributed to the development of many different and sometimes contradictory models of pool boiling phenomena and dominant heat transfer mechanisms.
Numerical Simulation of Femtosecond Laser Ablation of Copper: Comparison Between Molecular Dynamics and Finite Difference Calculations
Authors: Cheng Changrui , Chowdhury Ihtesham H. , Xu Xianfan , Murthy Jayathi , Grama Ananth , Wang Xinwei
Published: December 2008

Molecular Dynamics (MD) and Finite Difference (FD) methods are applied to investigate femtosecond laser ablation of copper. Laser induced heat transfer, melting, vaporization, and material ablation are studied. Phase change relevant parameters, such as the velocity of solid-liquid and liquid-vapor interfaces are reported. It is shown that results of MD and FD are in good agreement before strong material removal occurs. However, only MD is capable of capturing the ablation phenomena accurately.
Testing Altitude Effects on Locomotive Emissions
Authors: Glenn W. Doug , Casabianca Jose M. , Gallagher Shawn M. , Dillen Eric
Published: December 2008

The Environmental Protection Agency (EPA) has regulated that locomotives must comply with emissions regulations from sea level up to 2133 meters (7000 feet) altitude. GE Rail has assembled a mobile emissions test laboratory that can be taken by rail to desired testing locations of varying altitude anywhere in North America. This paper gives an overview of the mobile test laboratory’s make up and locomotive preparation for test. Testing was conducted as part of GE Rail’s development of 21st Century Locomotive. The paper presents test results of altitude effects on GE’s Evolution Series Locomotive including regulated emissions and engine performance. The Evolution Series Locomotive meets EPA Tier 2 locomotive emissions regulations applicable to new locomotives manufactured after January 1, 2005.
Numerical Simulation and Experiments of Reformed Fuel Blends in a Lean-Burn Spark-Ignited Engine
Authors: Fiveland Scott B. , Bailey Brett M. , Willi Martin L. , Hiltner Joel D. , Parsinejad Farzan , Metghalchi Hameed
Published: December 2008

Premixed, lean burn combustion research has focused for years on extending the lean flammability limit while maintaining both stables ignition and turbulent flame propagation. Operating with a leaner air-fuel mixture results in a lower temperature conversion of reactants to products (i.e. reduced NOx) while maintaining thermal efficiency. The lean limit, at some level, is dependent on both the fuel transport and chemical properties. This work sets out to numerically explore the effect of reformed fuels on both fundamental flame stability and the performance/emissions tradeoffs of the engine. The numerical simulations were conducted for a range of reformed fuel blends (10–40%) as well as mixture equivalence ratios (0.35–0.6). The laminar flame speed results clearly define the regime of stable flame propagations for equivalence ratio/reformed fuel blend combinations. Subsequently, a validated and predictive quasi-dimensional engine simulation is used to simulate the performance/emissions characteristics of the complete engine system operating on the reformed fuel blends (10–50%) for a range of ignition timings, and air-fuel ratios. The performance trends define not only the misfire and detonation limits associated with the air-fuel blends but also the thermal efficiency/NOx tradeoffs.
Optimization of a Non-Fueled Prechamber Ignition System for a Lean-Burn, Industrial Natural Gas Engine
Authors: Honl Corey A.
Published: December 2008

A non-fueled prechamber ignition system was developed to provide for controlled and stable combustion to best support the goals of both Waukesha Engine and the ARES program. This paper will provide details and results of efforts undertaken in optimization of the following design aspects: tangential angle of prechamber orifice channels in relation to head-induced cylinder swirl, prechamber orifice diameter, prechamber volume (spark plug recess in precombustion chamber), and recession of the entire precombustion chamber into the cylinder head. A number of important conclusions will be verified and presented based on the development work done on a laboratory engine.
Reducing Cylinder-to-Cylinder Variation in a V-8 Natural Gas Engine With Cycle Simulation Techniques
Authors: Eubanks Jeremy , Branyon David , Smith Jack
Published: December 2008

During a recent project at Southwest Research Institute® (SwRI®), a medium-duty turbo-charged V-8 diesel engine was converted to natural gas operation for low-emission power generation applications. Initial cycle simulation studies indicated significant levels of cylinder-to-cylinder variation with the stock induction and exhaust system, which can limit the potential performance gains of a lean-burn spark-ignited engine due to spark knock and lean misfire. Cycle simulation techniques were used to investigate the sources of the cylinder-to-cylinder variation and determine potential solutions. The results indicated that significant improvements could be made with new intake and exhaust manifolds and a different turbocharger configuration.
Cycle-Controlled Water Injection for Steady-State and Transient Emissions Reduction From a Heavy-Duty Diesel Engine
Authors: Stanglmaier Rudolf H. , Dingle Philip J. , Stewart Daniel W.
Published: December 2008

A system for co-injecting mixtures of diesel fuel and water into a heavy-duty diesel engine has been developed and evaluated at the Southwest Research Institute. This system features prototype Lucas EUI injectors, full electronic control, and can vary the percentage of water in the mixture on a cycle-resolved basis. Tests of this system were conducted on a production Volvo D-12 engine, and have produced very encouraging results. Water-diesel co-injection yielded a considerable improvement in NOx-smoke and NOx-BSFC trade-offs under steady-state engine operation. In addition, control of the water percentage on a cycle-resolved basis was shown to be an effective method for mitigating NOx and smoke emissions over step-load transients. Results from this work show that a combination of aggressive EGR and diesel+water co-injection is very promising for producing very low levels of engine-out exhaust emissions, reducing the water storage requirements, and improving fuel efficiency. Further refinement of this injection technology is in progress.
A New Criterion to Determine the Start of Combustion in Diesel Engine
Authors: Katrasˇnik Tomazˇ , Rodman Opresˇnik Samuel , Trenc Ferdinand , Sˇkific´ Nedjeljko
Published: December 2008

A new criterion for the determination of the start of combustion (SOC) from the diesel engine in-cylinder pressure diagram was developed. It is defined as the maximum of the third order derivative of the cylinder pressure with respect the crank angle. This criterion declares SOC more precisely than other previously published criterions based on pressure diagnostics. This fact was proven analytically and was discernable from the analysis of the experimental data. Beside its accuracy it is also robust enough to allow automatic evaluation of the SOC during processing of the pressure data for a large number of cycles. Analysis of the first law of thermodynamics applied to the engine cylinder showed that the third order derivative of the cylinder pressure with respect to the crank angle is the most suitable criterion for determination of the SOC from the cylinder pressure diagram. Subsequently the criterion was validated through experimental data analysis of the cylinder pressure diagrams for various engine speeds and loads. Cylinder pressure diagrams were processed with a computer code based on the first law of thermodynamics to evaluate the rate of heat release (ROHR), which formed the base for experimental validation. The cylinder pressure was measured with an advanced piezoelectric sensor at the resolution 0.1 deg. CA. Top dead center was determined with the capacitive top dead center sensor. Due to the analytic foundation of the developed method and its validation through highly accurate experimental data it can be concluded that new criterion is credible for the determination of the SOC.
Vehicle Simulation on the Test Bench
Authors: Corti Enrico
Published: December 2008

International emission tests (EPA, SFTP, MVEG-B, J-10.15, etc.) are carried out with vehicles running on the rolls dynamometer. Results, in terms of total emissions, are influenced by vehicles parameters such as mass, gear ratios, front surface, drag coefficient, etc. It would be useful, in the automobiles design phase, to have information about the impact of these parameters on total emissions. The obvious solution would be to build up a complete vehicle model to simulate performance and emission levels. Engine pollutants production modeling is the weak point, since it is difficult to obtain reliable results. Anyway it is possible to avoid pollutants production simulation, testing the actual engine under the same operating condition it would face inside the car’s hood. This paper describes a methodology whose aim is to test the engine on a standard test bench, simulating on-board operating conditions. An equivalence condition has to be satisfied in order to guarantee the methodology effectiveness: engine speed and Manifold Absolute Pressure (MAP) must always match for the two types of test performed on the same driving cycle. Engine speed and torque can be controlled through the bench actuators, their values depending on the simulated vehicle motion: once the car dynamics are simulated by means of a model, engine speed and torque corresponding to the given driving cycle can in fact be evaluated. The model is solved in real time, its output being the brake load torque value satisfying the equivalence condition. The brake controller, used as a slave, regulates the engine operating conditions consequently. The global model incorporates tires, aerodynamic forces, clutch, gearbox and driveline behaviors simulation: its response has been first validated comparing its outputs with data measured on board, and then it has been used to control an eddy current brake, for vehicle test simulation on the test bench. Two different control philosophies can be used: either a human driver or an automatic controller can ride the simulated car. The influence of vehicle parameters and gearshift mode on fuel consumption and pollutant emissions can be investigated.
On Combustion Invariants for MBT Timing Estimation and Control
Authors: Haskara Ibrahim , Zhu Guoming G. , Daniels Chao F. , Winkelman Jim
Published: December 2008

An MBT timing control criterion has been studied through burn rate analysis using pressure measurements. The optimal spark timing which maximizes the power output mainly depends on engine speed, load and mixture composition among others. A combustion invariant at MBT timing is sought to characterize the MBT combustion. Specifically, it has been shown that the maximum mass fraction acceleration point occurs around TDC at MBT timing by analytically processing the wide range spark sweep data.
Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines
Authors: Tissera Chamila A. , Swartz Matt M. , Tatli Emre , Vellaisamy Ramprabhu , Clark Nigel N. , Thompson Gregory J. , Nine Ralph D. , Atkinson Richard J.
Published: December 2008

NOx control in a lean burn natural gas engine is typically achieved with appropriate management of air/fuel ratio and ignition timing. A novel approach for further reduction involves the capture of NOx by first adsorbing the NOx from the exhaust stream, followed by the periodic desorption of NOx from an aftertreatment medium. Then, by passing the desorbed NOx gas into the intake air stream and back through the engine, a percentage of the NOx will be converted to harmless gases during the combustion process. The objective of this paper is to report the NOx conversion phenomenon during a lean combustion process. The results of this testing will be used to develop an optimal system for the conversion of NOx with a NOx adsorber. A 1993 Cummins L10-G spark ignited natural gas engine was used to conduct the experiments. Commercially available nitric oxide (NO, 98.8% purity) was injected into the engine intake to mimic the NOx stream from the desorption process to obtain NO conversion rates at various steady-state engine operating points. The NO injection system was capable of injecting NO at varying flow rates and time intervals. NO was injected into the intake manifold for ten and twenty second periods, and the conversion rates were calculated. When the injected NO amount increased from 0.22 g/s to 1.2 g/s and engine loads varied from 200ft-lb to 400ft-lb at 800 RPM, the NO conversion rates increased from 5% to 47%. It was observed that the air/fuel ratio, injected NO quantity and the engine load greatly effected the NO conversion rates. It was also noted that engine speed had a negligible affect when the intake NO concentration was held constant.
Examination of Knock Limits of a Spark Ignited Natural Gas Engine
Authors: Soylu Seref
Published: December 2008

A zero-dimensional two-zone thermodynamic model was used to examine knock limits of a spark ignited natural gas engine. Experimentally based burning rate models were used for flame initiation and propagation calculations. A knock integral was incorporated with the zero-dimensional model. Comparison of the measured and calculated cylinder pressure data indicated that the model is able to match the measured cylinder pressure data with less than 8% error in magnitudes if the computations are started at experimental spark timing. The knock predictions were agreed with the measurements, also. With the established knock model, it is possible not only to investigate if knock is observed with changing operating and design parameters, but also to evaluate their effects on the maximum possible knock intensity.
Sensitivity Analyses of NOx Formation in Micro-Pilot Ignited Natural Gas Engines
Authors: Yang Huateng , Krishnan S. R. , Srinivasan K. K. , Midkiff K. Clark
Published: December 2008

A sensitivity analysis of NOx formation in micro-pilot ignited natural gas dual fuel engines is performed based on a phenomenological combustion model. The model’s NOx formation mechanism incorporates a super-extended Zel’dovich mechanism (up to 43 reactions). The sensitivity analysis compares the contribution of each major reaction to NOx formation, and identifies the rate controlling NOx formation reactions. The formation rates for reactions involving NOx are also investigated to reveal the primary NOx formation paths. Results show that there are two main NOx formation paths both in the packets zone and the burned zone. The rate limiting reactions for the packets zone are identified as: O+N2=NO+NN2+HO2=NO+HNO Rate limiting reactions for the burned zone are: N2O+M=N2+O+MN2+HO2=NO+HNO Since the aforementioned reaction significantly influence the net NOx prediction, it is important that the corresponding reaction rates be determined fairly accurately. Finally, because the quasi-steady-state assumption is commonly used for certain species in NOx modeling, a transient relative error is estimated to evaluate its use. The relative error in NOx prediction with and without this assumption is of the order of 2 percent. Clearly, sensitivity analysis can provide valuable insight into understanding the possible NOx formation pathways in engines and improve the status of current prediction tools to obtain better estimates.
Application of Adaptive Control to Reduce Cyclic Dispersion Near the Lean Limit in a Small-Scale, Natural Gas Engine
Authors: Edwards K. Dean , Wagner Robert M.
Published: December 2008

Predictive feedback control is applied to achieve reduction in cyclic dispersion in an analytical, lean, spark-ignition model and a two-cylinder, four-stroke, natural gas Kohler Command 25 engine operating at lean conditions. Recent observations of the combustion dynamics are used to define a desired target point for control and to predict future combustion events which may stray from the target point. Fueling perturbations are applied to steer the system back toward the desired behavior. Overall control perturbations are constrained to maintain a constant average fuel-to-air ratio. We present two methods for obtaining the prediction of future combustion events. In the first method, the recent history of cycle heat release is used to construct an adaptive, low-order map which relates the current-cycle heat release to the next-cycle heat release. The second method uses symbolic analysis to determine the relative frequency of successive-cycle combustion events and predict the most probable successor to the current cycle. Results are presented which show a moderate reduction in cycle-to-cycle variation near the lean limit in both the model and the engine. Similarities in behavior have been shown to exist-ignition engines suggesting that a similar prediction strategy could be successfully applied to control cyclic dispersion in large-scale reciprocating engines.
An Estimation of 3-Way Catalyst Performance Using Artificial Neural Networks During Idle Speed
Authors: Botsaris P. N. , Bechrakis D. , Sparis P. D.
Published: December 2008

The intelligent control as fuzzy or artificial is based on either expert knowledge or experimental data and therefore it possesses intrinsic qualities like robustness and ease implementation. Lately, many researchers present studies aim to show that this kind of control can be used in practical applications such as the idle speed control problem in automotive industry. In this study, an estimation of an automobile three-way catalyst performance with artificial neural networks is presented. It may be an alternative approach for an on board diagnostic system (OBD) to predict the catalyst performance. This method was tested using data sets from two kind of catalysts, a brand new and an old one on a laboratory bench at idle speed. The catalyst operation during the “steady state” phase (the phase that the catalyst has reached its operating conditions and works normally) is examined. Further experiments are needed for different catalyst typed before the methods is proposed generally. It consists of 855 elements of catalyst inlet-outlet temperature difference (DT), hydrocarbons (HC), and carbon monoxide (CO) and carbon dioxide (CO2) emissions. The simulation: detects the values of HC, CO, CO2 using the DT as an input to our network forms a neural network. Results showed serious indications that artificial neural networks (or fuzzy logic control laws) could estimate the catalyst performance adequately depending their training process, if certain information about the catalyst system and the inputs and output of such system are known. In this study the “steady state” period experimental results are presented. In this paper the “steady state” period experimental results are presented.
Size Distribution of Diesel Particulate Matter From a Heavy Duty Diesel Engine During FTP Transient Cycle
Authors: Tatli Emre , Clark Nigel N. , Atkinson Richard J. , Thompson Gregory J.
Published: December 2008

Researchers concerned both with diesel exhaust health effects and with mechanisms of particulate matter (PM) formation have an interest in gaining understanding of PM size distributions from heavy-duty on-road diesel engines. Prior research has been done on particulate size measurement but the results fall short in understanding PM size distributions because of the response time or size range of the instruments used. This study reports the transient size distributions of PM from a 1992 Detroit Diesel Series 60 on an engine dynamometer from a full flow dilution tunnel for a FTP Transient Cycle using a Cambustion ® Differential Mobility spectrometer (DMS 500). The size bins selected for this study for the nucleation and accumulation modes were 20nm and 60nm bins, respectively. The accumulation mode during the accelerations and the nucleation mode during the decelerations were clearly observed from the distributions with respect to time. Distributions were also observed during the test cycle showing the transition between the two modes. From the results obtained from the analysis, no strong correlation between the 60nm particles and engine speed was observed even though higher counts of accumulation particles were observed at the same time that the vehicle activity occurred. Similarly, there was no correlation between the accumulation mode particles and power. When the distributions of nucleation and accumulation mode particles were plotted against each other, there was no correlation or anti-correlation. The average size distributions were also analyzed during the four periods of the FTP Transient cycle and the highest counts were observed during the Los Angeles Freeway (LAF) period. Also, higher counts at the second New York Non Freeway (NYNF) were observed during the cycle.
A Catalyst Surface Control Automation System for Emission Reduction During Cold Start
Authors: Karkanis Anastasios N. , Botsaris Pantelis N. , Sparis Panagiotis D.
Published: December 2008

This paper presents and discusses experimental data obtained during test simulating the test cycle ECE-15 for a relatively simple method for the reduction of pollutant emissions during a cold start. During a cold start the volume of the exhaust gases is considerably smaller than the ones under full load. Therefore, only a small portion of the catalyst active surface is used to process the gases at the cold start phase. After the light-off at the initial surface the exhaust gases pass from the total catalytic surface which is already pre-heated from the first phase. The experimental results presented here indicate that there is a reduction of the pollutant emissions during the cold start of an engine. The developed system uses the 20% of the catalyst active surface during start-up and the rest of the catalyst surface after this phase, controlled by a proper automation system. At the cold start phase the system focusing the gas flow towards the center core of the monolith, so there is a quicker warm-up of the catalyst and a faster initiation of catalysis in this area. So when the remaining ceramic body of the catalytic converter is used, it is already warmed and the catalysis starts almost immediately.
Characterization of Erosion Mechanisms of Natural Gas Engine Spark Plugs
Authors: Richards Roger K. , Layton David M. , Lin Hua-Tay , Brady Michael P.
Published: December 2008

J-type spark plugs composed of Ni-base alloy electrodes with a pure Ir tip in the center electrode and a Pt-W alloy tip in the ground electrode were examined as-manufactured and after use in natural gas reciprocating engines by spectroscopic and metallurgical techniques. The spectroscopic examination indicated Ni emission from the Ni alloy electrodes in new plugs, but a strong Ca signal in engine used plugs. This was confirmed by metallurgical examination, which showed the presence of Ca containing glassy oxide phase(s) (with the electrode alloy components) in the used spark plug electrodes. Intergranular cracking was observed on the Ir and Pt-W alloy electrode insert tips. The interface between the Pt-W insert and the Ni alloy ground electrode also became a site for extensive cracking and oxidation during service. These oxidation/corrosion and metallurgical issues may represent a significant component of the wear mechanism of these plugs in natural gas engines.
The Reliability Improvement of a Conventional Cast Iron Exhaust Manifold for a Small Size Gasoline Engine
Authors: De Angelis Giuseppe , Palomba Fernando
Published: December 2008

This paper describes a challenging phase of the development of a cast iron exhaust manifold for a FIAT FIRE 16v engine. On these engine family, a close-coupled catalyst directly connected to the manifold is used. Conventional cast iron could be considered an obsolete material to realize modern car engine exhaust manifolds, but it’s still considerable as a profitable technology due to relatively low processing and part costs. Moreover, due to actual exhaust emission regulation, the engine calibration determinates higher temperature values and gradients on the exhaust system than in the past. Consequently thermal fatique life, weight and manifold wall thickness limits become some of the main concerns for the engine designer when conventional cast iron is considered. To improve the actual cast iron manifold, according to the engine program timeline, a simplified, fast approach to thermal fatigue life improvement has been used, involving only in-house resources to achieve a further cost-time reduction in the definition and implementation of the necessary design changes. By means of Infrared Thermography, the distribution of the external surface of the exhaust manifold was acquired, on the engine bench, in-firing conditions, during specific accelerated thermal fatigue test cycle. The 2D surface temperature distribution was properly elaborated to obtain a 3D temperature distribution and a thermostructural FE Analysis has been developed to predict the critical areas of the component, considering the variation of the relevant material properties with temperature. The evaluation of the regions where thermal crack initiation and propagation were expected has been done considering the stress distributions in the high-temperature phase and during the cool-down phase of the test cycle. The comparison with the cracked manifold returned from the road test has shown a good agreement with the first results obtained from the analysis. For the optimisation, the same temperature acquisition and analysis were performed considering the manifold, made of the same material, used for a similar application for which no failures occurred during tests, obtaining information about the safe combination of stress and temperature level for the specific spheroid cast iron used. Those data were applied to validate the improved design that passed the following endurance tests, with only a minor acceptable impact in terms of weight, costs and development time.
Use of Railplugs to Extend the Lean Limit of Natural Gas Engines
Authors: Gao Hongxun , Matthews Ron , Hari Sreepati , Hall Matt
Published: December 2008

Ignition of extremely lean mixtures is a very challenging problem, especially for the low speed, high load conditions of large-bore natural gas engines. This paper presents initial results from testing a high energy ignition system, the railplug, which can assure ignition of very lean mixtures by means of its high energy deposition and high velocity jet of the plasma. Comparisons of natural gas engine tests using both a spark plug and a railplug are presented and discussed in this paper. The preliminary engine test show that the lean stability limit (LSL) can be extended from an equivalence ratio, φ, of ∼0.63 using a spark plug down to 0.56 using a railplug. The tests show that the railplug is very promising ignition system for lean burn natural gas engines and potentially for other engines that operate with very dilute mixtures. The ignition characteristics of different railplug geometric and circuit designs are also discussed.
Reduction of Emissions From a High Speed Passenger Ferry
Authors: Thompson Gregory J. , Clark Nigel N. , Gautam Mridul , Carder Daniel K. , George Sam
Published: December 2008

Emissions from marine vessels are being scrutinized as a major contributor to the total particulate matter (TPM), oxides of sulfur (SOx), and oxides of nitrogen (NOx) environmental loading. Fuel sulfur control is the key to SOx reduction but NOx and PM production are primarily engine design dependent. Significant reductions in the emissions from on-road vehicles have been achieved in the last decade and emissions from these vehicles will be reduced by another order of magnitude in the next five years. These improvements have served to emphasize the need to reduce emissions from other mobile sources, including off-road equipment, locomotives, and marine vessels. Diesel-powered vessels of interest include ocean-going vessels with low- and medium-speed engines, as well as smaller vessels with medium- and high-speed engines. A recent study examined to use of intake water injection (WIS) and ultra low sulfur diesel (ULSD) fuel to reduce the emissions from a high-speed passenger ferry in southern California. One of the four Detroit Diesel 12V92 two-stroke, high-speed engines that power the ferry was instrumented to collect intake airflow rate, fuel flow rate, shaft torque, and shaft speed. Engine speed and shaft torque were uniquely linked for given vessel draft and prevailing wind and sea conditions. A raw exhaust gas sampling system was utilized to measure the concentration of NOx, carbon dioxide (CO2), and oxygen (O2), with a mini dilution tunnel sampling a slipstream from the raw exhaust was used to collect TPM on 70 mm filters. The emissions data were processed to yield brake-specific mass results. The emissions measurement system that was employed allowed for redundant data to be collected for quality assurance and quality control. To acquire the data, the ferry was operated at five different steady-state speeds. Three modes were executed in the open sea off Oceanside, CA, idle and harbor modes were also selected for the test matrix. Data have showed that the use of ULSD along with water injection (WIS) could significantly reduce the emissions of NOx and PM while not affecting fuel consumption or engine performance, when compared to baseline marine diesel fuel. The results showed that a normal 40% reduction in TPM was realized when switching from marine diesel fuel to ULSD. A small reduction in NOx was also shown between the marine fuel and the ULSD. The implementation of the WIS reduced NOx by 11% to 17%, depending upon the operating condition. With the WIS, TPM was reduced by a few percentage points, which was close to the confidence level of the measurements.
Enhanced Application and Emission Control Possibilities With Electronically Controlled Low Speed Diesels
Authors: Gro̸ne Ole , Aabo Kjeld , Skjoldager Peter
Published: December 2008

Two-stroke low speed diesels dominate the main propulsion engine market, being selected for nearly 80% of all ocean-going vessels. The main reason is the simplicity of the direct-coupled installation, the high reliability and the high thermal efficiencies. Four-stroke medium speed engines take the last 20%, except on the LNG carrier propulsion field where steam turbines, while being threatened, still prevail. The occasional exception to the above is a few gas turbines in passenger (cruise) vessels. Recently, two-stroke low speed diesels have been developed for electronically controlled fuel injection systems, and such engines are now gaining momentum in the industry. The electronically (rather than cam) controlled fuel injection systems bring with it many operational benefits, which will be outlined in the paper. One such feature is the ability to inject very small fuel amounts safely through the same injectors as those able for full power operation. This paves the way for a more simple and safe version of large low speed dual fuel gas engines for propulsion of LNG carriers, representing significant fuel and gas saving possibilities, reducing CO2 emissions, and also opening new frontiers for low emission high-efficiency ship propulsion systems in other vessel types, including the largest types, as well as land based power generation. The paper will outline the technology, especially with a view of emission control and its economical and environmental potential.
Bifunctional Catalysts for the Selective Catalytic Reduction of NO by Hydrocarbons
Authors: Neylon Michael K. , Castagnola Mario J. , Kropf A. Jeremy , Marshall Christopher L.
Published: December 2008

Novel bifunctional catalysts combining two active phases, typically Cu-ZSM-5 and a modifier, were prepared and tested for the selective catalytic reduction of nitrogen oxides using propylene in order to overcome the hindering effects of water typically seen for single-phase catalysts such as Cu-ZSM-5. The catalysts were made by typical preparation techniques, but parameters could be varied to influence the catalyst. The physical characterization of the materials showed that the modification phase was added strictly to the external surface of the zeolite without hindering any internal surface area. Chemical characterization by temperature-programmed reactions, DRIFTS and x-ray absorption spectroscopy indicated strong interaction between the two phases, primarily producing materials that exhibited lower reduction temperatures. Two improvements in NOx reduction activity (1000 ppm NO, 1000 ppm C3H6, 2% O2, 30,000 hr−1 GHSV) were seen for these catalysts compared with Cu-ZSM-5: a lower temperature of maximum NOx conversion activity (as low at 250°C), and an enhancement of activity when water was present in the system. The use of a second phase provides a way to furthure tune the properties of the catalyst in order to achieve mechanistic conditions necessary to maximize NOx remediation.
Film Thickness and Friction Measurement of Piston Ring Cylinder Liner Contact With Corresponding Modeling Including Mixed Lubrication
Authors: Bolander Nathan W. , Steenwyk Brian D. , Kumar Ashwin , Sadeghi Farshid
Published: December 2008

An experimental apparatus and an analytical model have been developed to investigate and determine the lubrication condition and frictional losses at the interface between a piston ring and cylinder liner. The experimental apparatus features twin fiber optic displacement sensors to accurately measure the lubricant film thickness and a tri-axial piezoelectric force transducer to simultaneously measure frictional force. An analytical mixed lubrication model featuring Elrod cavitation and a stochastic/deterministic approach for asperity contact was used to investigate the effects of boundary and mixed lubrication conditions at the ends-of-stroke. A comparison between experimental and analytical results indicated that they are in good agreement. The results illustrate the transition through all of the different lubrication regimes (i.e. boundary, mixed and hydrodynamic lubrication) the piston ring and liner experience during a stroke. The twin displacement sensor arrangement is capable of producing accurate, repeatable measurements of lubricant film thickness that are in agreement with the analytical predictions. The analytical model developed for this study can capture the different lubrication regimes that the piston ring and liner experience.
Numerical Analysis of Swirl Control Strategies in a Four Valve HSDI Diesel Engine
Authors: Fontanesi S. , Mattarelli E. , Montorsi L.
Published: December 2008

Recent four value HSDI Diesel engines are able to control the swirl intensity, in order to enhance the in-cylinder flow field at partial load without decreasing breathing capabilities at full load. Making reference to a current production engine, the purpose of this paper is to envestiage the influence of port design and flow-control strategies on both engine permeability and in-cylinder flow field. Using previously validated models, 3-D CFD simulations of the intake and compression strokes are performed in order to predict the in-cylinder flow patterns originated by the different configurations. The comparison between the two configurations in terms of airflow at full load indicates that Geometry 2 can trap 3.03% more air than Geometry 1, while the swirl intensity at IVC is reduced (−30%). The closure of one intake valve (the left one) is very effective to enhance the swirl intensity at partial load: the Swirl Ratio at IVC passes from 0.7 to 2.6 for Geometry 1, while for Geometry 2 it varies from 0.4 to 2.9.
Combustion Monitoring of Lean-Burn Gas Engines With Ion Feedback
Authors: Tozzi Luigi , Benson Kelly , Viele Matthew
Published: December 2008

For many years ion feedback has been utilized on spark ignited gasoline engines running at stoichiometric air-fuel ratios.1,2,3,4 When used in conjunction with proper ion signal detecting circuitry, the spark plug serves as an effective combustion ion sensor and can detect certain characteristics about combustion. Ion sensing has also been employed on stoichiometric natural gas engines with very positive results. However, attempts to extract useful ion signals from high BMEP lean-burn gas engines have previously proven to be unsuccessful. Recently developments in signal recognition, along with correlations between combustion chamber and spark plug design have made ion sensing for lean-burn gas engines a realistic diagnostic technique. Algorithms have been demonstrated for misfire, knock and combustion quality. Test results show that ion sensing can produce combustion monitoring for lean-burn gas engines that previously required cylinder pressure transducers. With proper integration into the ignition controller and engine management system, the ion feedback signal can allow gas engines to operate at the limit of misfire and knock. This allows minimizing of NOx emissions and fuel consumption.
In-Cylinder Fuel-Air Mixture Investigation by Particle Image Velocimetry in a GDI Engine
Authors: Valentino G. , Auriemma M. , Caputo G. , Corcione F. E.
Published: December 2008

The present paper aims at providing experimental results on the spray structure and its interaction with the air flow generated by the intake ducts of a commercial light duty gasoline direct injection (GDI) engine head. The investigation was carried out by the Particle Image Velocimetry (PIV) technique to investigate the air flow and fuel droplets velocity evolution within a prototype cylinder with optical accesses. Experiments were carried out at various operating conditions reproducing the mixture preparation for an early injection strategy. The PIV technique was applied in a flow test rig assembled with a blower, which supplied the intake flow rate, connected to the intake manifold of a commercial 4-valve direct injection gasoline engine head modified to lay down an external driving control system for the valves motion. Experiments were taken equipping the engine head with a common rail injection system able to work up to 10 MPa, and a swirled type injector having a nozzle diameter of 0.50 mm and a nominal cone angle of 60°. Tests were taken, on a plane crossing the cylinder and the injector axes, supplying to the prototype cylinder an intake flow rate of 29 m3/h and spraying the gasoline at two injection timings in a range of injection pressure of 6, 8, and 10 MPa. The results provided detailed information on the intake flow field behavior and the evolution of fuel jet within the air flow. The intake flow velocity distribution, acquired at different cam angle during the induction, showed the development of an initial clockwise tumble flow with a tendency to produce two large flow structures: a main counter clockwise vortex and a clockwise ones located at the opposite side of the field of view. Images of the interaction of the fuel with the tumble motion displayed, firstly, a fuel jet shape that traveled not affected by the tumble motion because of its high momentum. Later during the intake, the fuel was strongly distorted by the air motion with the formation of clusters detached from the main jet and spread within the cylinder so allowing to hypothesize that the intake bulk flow may be a crucial parameter to control the fuel penetration and the droplets distribution within the cylinder.
An Experimental Investigation of NOx Emission Reduction From Automotive Engine Using the Miller Cycle
Authors: Wang Yaodong , Ruxton Tom
Published: December 2008

An experimental investigation of NOx emission reduction from automotive (petrol) engine using the Miller Cycle was carried out. Two versions of Miller Cycle were designed and realized on a petrol engine. The tests were carried out on the test rig. The test results showed that applying Miller Cycle could reduce the emission of nitrogen oxides from petrol engine.