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Martin, Jay K.
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Ignition System Characteristics and Effects on Combustion for a Two-Stroke Engine

University of Wisconsin, Engine Research Center-David J. Grupp, Jay K. Martin
Published 2002-03-04 by SAE International in United States
Experiments were conducted using three different ignition systems on a single cylinder, two-stroke research engine. The ignition systems included a transistorized coil ignition (TCI), a capacitive discharge ignition (CDI), and a commercially available multistrike system (JCI). The sparks produced by each ignition system were characterized using three different types of spark plugs. Spark voltage and current data along with simultaneous high speed images of the spark process in a pressurized chamber were obtained. Each ignition system was evaluated in a two-stroke research engine in terms of cyclic variability, misfire rate, and indicated power produced. In addition, ion sensing was used to detect cycle misfires and various strategies were used to improve engine performance.
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A Comparison Between CFD Predictions and Measurements of Inlet Port Discharge Coefficient and Flow Characteristics

Briggs and Stratton Corp.-Paul Ruppel, Mark Meyer
Harley-Davidson Motor Co.-Allen Tang, Brad Tillock
Published 1999-09-28 by SAE International in United States
Predictions of the volume flow rate through an inlet port were produced by four different commercially available CFD programs suitable for use in a steady flow simulation. These predictions were compared with experimental measurements of an inlet port's discharge coefficients.The experiment performed was a typical steady state flow bench test for an inlet port. Volume flow rates were measured at five different valve lifts. The largest valve lift tested (12.24mm) was the maximum value of lift under actual operation. The smallest valve lift was typical of early valve opening. The tests were performed at two different pressure differences across the inlet port and valve at each of the five different valve lifts.All predictions were made using an RNG k-ε turbulence model. Standard wall functions were used to predict wall friction effects and the energy equation was included to account for compressibility effects. Also, a mesh sensitivity study and a study of the effect of different turbulence models was carried out.Ultimately, five different users using four different CFD programs produced predictions of the volume flow rates…
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Effects of Ignition Timing and Air-Fuel Ratio on In-Cylinder Heat Flux and Temperatures in a Four-Stroke, Air Cooled, Homogeneous Charge Engine

Briggs and Stratton Corp.-Art Poehlman, Doug Shears
Engine Research Center, University of Wisconsin-Madison-Brian P. Boyce, Jay K. Martin
Published 1999-03-01 by SAE International in United States
In-cylinder heat flux and temperature measurements were obtained in an air-cooled four-stroke utility engine for a range of air-fuel ratios. For these measurements, the magnitude of the integrated heat flux peaked at the stoichiometric air-fuel ratio, with an approximately linear decrease on either side of stoichiometric. Advancing the spark generally increased the magnitude of the integrated heat flux. Evaluation of the Brake Specific Integrated Heat Flux (BSIHF) mitigated these trends, and, the effects of changes in timing were eliminated for some operating conditionsExamination of the BSIHF from the compression and expansion stroke showed behavior mimicking the full cycle BSIHF. However, the fraction of the total flux contributed by this portion of the cycle varied greatly from approximately 98% of the total to approximately 75% of the total. In addition, BSIHF for the gas exchange portion of the cycle exhibited much different trends than the full cycle BSIHF, with the peak values occurring with mixtures lean of stoichiometric and retarded timings.Steady-state values of cylinder head temperatures near the surface were also obtained to observe how air-fuel…
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In-Cylinder Mixing Rate Measurements and CFD Analyses

Ford Motor Company-Jialin Yang, Richard Anderson
University of Wisconsin-Madison-Steven J. Lacher, Li Fan, Brad Backer, Jay K. Martin, Rolf Reitz
Published 1999-03-01 by SAE International in United States
Gas-phase in-cylinder mixing was examined by two different methods. The first method for observing mixing involved planar Mie scattering measurements of the instantaneous number density of silicon oil droplets which were introduced to the in-cylinder flow. The local value of the number density was assumed to be representative of the local gas concentration. Because the objective was to observe the rate in which gas concentration gradients change, to provide gradients in number density, droplets were admitted into the engine through only one of the two intake ports. Air only flowed through the other port.Three different techniques were used in analyzing the droplet images to determine the spatially dependent particle number density. Direct counting, a filtering technique, and autocorrelation were used and compared. Further, numerical experiments were performed with the autocorrelation method to check its effectiveness for determination of particle number density.Results from the three techniques for determining particle number density showed similar trends. The filtering and autocorrelation methods produced higher resolution than was obtainable with the direct counting methods.Engine speed, and throttle position influenced the…
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Steady-State Thermal Flows in an Air-Cooled, Four-Stroke Spark-Ignition Engine

Engine Research Center, University of Wisconsin-Madison-Brian P. Boyce, Jay K. Martin
Harley-Davidson Motor Company-Brad R. Tillock
Published 1999-03-01 by SAE International in United States
Measurements of the instantaneous heat flux at three positions on the cylinder head surface, and the steady-state cylinder head temperatures at four positions on the cylinder head have been obtained. Engine tests were performed for a range of air-fuel ratios including regimes rich of stoichiometric, stoichiometric, and lean of stoichiometric. In addition, ignition timing was advanced in increments from 22° BTDC to 40° BTDC.All tests were run with the throttle either fixed in the wide open position, or fixed in a position that produced 75% of the maximum power with the standard ignition timing and an air-fuel ratio of 13.5. This was done to ensure that changes in air mass flow rate were not influencing the results. In addition, all tests were performed with a fuel mixture preparation being provided by system designed to deliver a homogeneous premixed charge to the inlet port. This was done to ensure that mixture preparation issues were not confounding the results.Based on the results of the heat flux measurements, a phenomenological model for spatially resolved predictions of the steady-state…
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Inlet Port Geometry and Flame Position, Flame Stability, and Emissions in an SI Homogeneous Charge Engine

Engine Research Center, University of Wisconsin-Mitchell P. Patrie, Jay K. Martin
Kohler Co.-Thomas J. Engman
Published 1998-09-14 by SAE International in United States
This study investigates the relationship between intake port geometry, flame position and stability, and combustion rate and emissions in an air-cooled four-stroke engine where three intake ports of differing geometry have been tested. In particular, the production intake port geometry, and directed and helical intake port geometries were tested.It was a specific intent of this study to investigate the interaction between inlet port geometry, equivalence ratio and ignition timing, without interference from mixture preparation effects. Thus all tests were performed using a homogeneous mixture of propane and air.Significant differences in combustion stability, flame position and stability, burn rate and emissions were observed. For example, the flow induced by the helical port, which should be characterized by a dominant swirl motion, resulted in stabile, asymmetric flames at many of the operating conditions studied. In contrast, the production port generated a flow that resulted in more nearly symmetrical flame propagation, with slower rates of heat release, and generally higher variability. CO emissions were found to only a function of equivalence ratio, and independent of the port geometry…
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Mass-Related Properties of Atomizers for Direct-Injection SI Engines

Mercury Marine, Division of Brunswick Corp.-Sam W. Coates
University of Wisconsin, Madison-Jeffrey A. Hoffman, Farhan Khatri, Jay K. Martin
Published 1998-02-23 by SAE International in United States
Mass-related properties of four atomizers were estimated with the use of a mechanical transient patternator. The properties presented on a temporal and spatial basis are the axial liquid mass flux, liquid fuel to air ratio, and liquid axial velocity. The data are presented in two formats. The first format consists of the mass-related properties that occurred radially between two planes positioned 2.0 cm and 2.25 cm along the atomizer axis. A second format consists of interpolated contour plots of the axial liquid mass flux for all of the spray systems studied.The atomizers used in the study consisted of three liquid-only high-pressure systems and one air-assist system. Two of the liquid-only high-pressure systems and the air - assist system were operated with a volumetric delivery of 20 mm3 per injection while injecting into ambient conditions. A third liquid-only high-pressure system was operated with a delivery of 15 mm3 per injection.Ranges of 0 to 10 for the liquid fuel to air ratios, and 0 to 40 g/cm2/sec for the mass flux were observed. Average axial velocities were…
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In-Cylinder Heat Flux in a Four Stroke, Air-Cooled, Spark-Ignited Engine with Fixed Timing

Harley Davidson, Inc.-Bradley Tillock
University of Wisconsin - Madison-Jay K. Martin
Published 1997-09-08 by SAE International in United States
In-cylinder heat flux, cylinder pressure, and flame arrival and position data were obtained at air fuel ratios ranging from 11 - 16 at 3060 rpm and approximately 80% load. The engine used was a single cylinder, 5 hp, fixed timing, four stroke, overhead valve, air-cooled engine. Methods of mixture preparation include that produced with the stock carburetor, and with a system designed to provide the engine with a homogeneous mixture (HMS). Heat flux was measured using a thermopile device consisting of 300 thermocouple pairs. A thin film platinum RTD was used to measure the temperature at the thermopile and correct for sensitivity of the thermopile output to thermopile temperature. Flame arrival near the sensor was found through the analysis of an ion voltage signal from a probe located next to the heat sensor.An effort was made to identify and account for the variables which influence in-cylinder heat transfer. It was determined that with changing A/F mixtures, the dominant factor influencing heat transfer was variation in flame and pressure development which led to changes in both…
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Spray Combustion and Emissions in a Direct-Injection Two Stroke Engine With Wall-Stabilization of an Air-Assisted Spray

Mercury Marine Division, Brunswick Corp.-Sam W. Coates
Outboard Marine Corp.-Frank A. McGinnity
Published 1997-02-24 by SAE International in United States
Previous experiments using an air-assisted spray in a two-stroke direct-injected engine demonstrated a significant improvement in combustion stability at part-load conditions when a wide injection spray was used. It was hypothesized that the decrease in variability was due to the spray following the combustion chamber wall, making it less affected by variations in the in-cylinder gas flows.For this study, experiments were conducted to investigate engine spray combustion for cases where engine performance was not dominated by cyclic variation. Combustion and emission performance data was collected for a wide range of injection timings at several speed/load conditions. Experimental data for combustion shows that combustion stability is relatively unaffected by injection timing changes over a 40 to 100 degree window, and tolerant to spark gap projections over a range of 0.7 to 5.2 mm, depending on operating conditions. However, exhaust emissions are much more sensitive to injection timing. Spray characterization data shows that the air/fuel mixture exiting the injector tends to follow the hemispherical chamber walls, concentrating the fuel mass on the perimeter. The range of injection…
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Comparison Between Air-Assisted and Single-Fluid Pressure Atomizers for Direct-Injection SI Engines Via Spatial and Temporal Mass Flux Measurements

University of Wisconsin-Madison-Jeffrey A. Hoffman, Eric Eberhardt, Jay K. Martin
Published 1997-02-24 by SAE International in United States
Two distinct atomization strategies are contrasted through the measurement of time and spatially dependent mass flux. The two systems investigated include a pressure atomizer (6.9 MPa opening pressure) and an air-assist atomizer. Both systems have potential for use in direct injection spark ignition engines.The mass flux data presented were obtained using a spray patternator that was developed to allow phased sampling of the spray. The temporal mass related history of the spray was reconstructed as volume versus time plots and interpolated mass flux contour plots.Results indicate substantial differences in the distribution of both mass and mass flux in space and time for the two injection systems. For example, the pressure atomizer at high mass delivery rates produced a spray that collapsed into a dispersed cylindrical shape while at low rates, generated a hollow cone structure. In addition, the air-assist device discharges 87% of its injected volume within the first of three poppet oscillations while producing a wide hollow cone structure.
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