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Fundamental Study on Combustion Diagnostics Using a Spark Plug as Ion Probe

Okayama University-Sadami Yoshiyama, Eiji Tomita
Polytechnic College Okayama-Yoshisuke Hamamoto
Published 2000-10-16 by SAE International in United States
In order to investigate the relation between ion current and combustion characteristics, the ion current signal from a spark plug as an ion probe, pressure history and flame development were measured in a homogeneous propane-air mixture in closed combustion chambers. The flame propagation was measured by Schlieren photography technique. When negative bias is applied to the central electrode of the spark plug, the ion current flows only due to an early flame kernel existing near the spark plug. When positive bias is applied to the central electrode, the ion current flows from the central electrode to the combustion chamber wall and to the ground electrode. Consequently, the ion current is dominated by the contact area between the flame and the combustion chamber wall. The appearance period of ion-current is related to the combustion duration. This method was applied to the combustion analysis of the spark ignition engine.
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Analysis of Oil Consumption at High Engine Speed by Visualization of the Piston Ring Behaviors

Nippon Soken, Inc.-Masatoshi Basaki, Kimitaka Saito, Tatsushi Nakashima
Toyota Motor Corp.-Takao Suzuki
Published 2000-10-16 by SAE International in United States
In internal combustion engine, it is well-known that oil infiltrates the combustion chamber through the clearance between the piston ring and the cylinder bore with vertical reciprocating motion of the piston, leading to an increase in oil consumption. The deformation of the cylinder bore is inevitable to some extent in the actual engine because of the tightening of cylinder head bolt and heat load._As to the function of the piston ring, it is desirable that it conforms to such bore deformation. The author et al. made a glass cylinder engine in which closed piston ring gap could be visualized, based on the idea that piston ring conformability to the sliding surface of bore could be evaluated from minute changes of the piston ring gap. This newly-devised visualized engine was an in-line 4-cylinder engine, capable of running up to 6,000 rpm, in which the closed gap of piston ring could be observed minutely during engine operation. As the result of the evaluation of the piston ring conformability to bore with this equipment, it was found that…
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A Theoretical Study of the Potential of NOx Reduction by Fuel Rate Shaping in a DI Diesel Engine

Lund Institute of Technology-Rolf Egnell
Published 2000-10-16 by SAE International in United States
In this paper, a theoretical study is presented where fuel rate shaping is analyzed in combination with EGR as a method for reducing NOx formation. The analytical tools used include an empirically based model to convert fuel rate to heat release rate, and a zero dimensional multizone combustion model to calculate combustion products, local flame temperatures and NOx emissions at a given heat release rate. The multizone model, which has been presented earlier, includes flame radiation and convective heat losses.Several geometrical shapes of the fuel rate are tested for different combustion timings and EGR rates. It is found that the fuel rate giving the lowest NOx formation varies with the injection timing. In order to lower the NOx emissions at normal and advanced injection timings, the fuel rate should have a rather long duration, and start at its maximum level followed by a slow decay. At later timings, however, the fuel rate should be more even and, in some cases, have its maximum rate at the end of injection.The reason why maximum fuel rate, at…
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Intake-Port Design for Mitsubishi GDI Engine to Realize Distinctive In-Cylinder Flow and High Charge Coefficient

Mitsubishi Automotive Engineering Corp.-M. Yokoe
Mitsubishi Motors Corp.-K. Kuwahara, T. Watanabe, H. Tanada, K. Ueda, H. Ando
Published 2000-10-16 by SAE International in United States
The Mitsubishi GDI engine has adopted a pair of upright intake ports, to induce a rotating in-cylinder flow, reverse tumble, and control air fuel mixing with this flow. The port design of the GDI engine was optimized for achieving a high intensity of the reverse tumble while maintaining a high charge coefficient, by means of modeling of in-cylinder flow and experiment with a steady flow rig.First of all, the ideal design of the upright ports was discussed. It was found that for enhancing the reverse tumble, it is more effective to arrange a pair of the ports parallel, than to arrange them convergent. The parallel arrangement leads to the smoother flows passing through the intake sides of the intake valves, and then descending on the cylinder liner, that is turning toward the rotation direction of the reverse tumble, because of less impingement of the flows through a pair of the valves.Actually, however, the completely parallel arrangement of the ports is not adoptable, because of interference of the ports with the spark plug located at the…
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An Evaluation of Natural Gas versus Diesel in Medium-Duty Buses

Dept. of Mech. and Aerospace Eng., College of Engineering and Mineral Resources West Virginia Univ. (WVU)-Nigel N. Clark, Donald W. Lyons
National Renewable Energy Laboratory (NREL)-Mike Frailey, Paul Norton
Published 2000-10-16 by SAE International in United States
Significant numbers of transit buses now operate on natural gas. With support of the U.S. Department of Energy, the National Renewable Energy Laboratory has evaluated the cost, performance, and emissions of alternative fuel buses around the country. In this study, three natural gas and three closely matched diesel buses were compared. The buses, built by World Trans, were 26′5″long and used 1997 Cummins B-series engines. Particulate matter and oxides of nitrogen emissions from the natural gas buses were significantly lower than those from the diesel buses. However, the diesel buses had lower operating costs and higher fuel efficiency than the natural gas buses.
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Demonstration of HCCI Using a Single Cylinder Four-stroke SI Engine with Modified Valve Timing

Ford Motor Co.-Tom Ma
University of Cambridge-George Kontarakis, Nick Collings
Published 2000-10-16 by SAE International in United States
A standard port fuel injected, unthrottled single cylinder four-stroke SI engine, with a compression ratio of 10.3:1, and using standard gasoline fuel, has been adapted to operate in the homogeneous charge compression ignition (HCCI) mode, by modifying the valve timing. It has been found that over a speed range of between 1300 and 2000 rpm, and lambda values of between 0.95 and 1.1, stable operation is achieved without spark ignition. The internal EGR rate was estimated to be about 60%, and emissions of NOX were typically 0.25 g/kWh.Practical implementation of this HCCI concept will require variable valve timing, which will also enable reversion to standard SI operation for maximum power.
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Experiments and Simulation of a Six-Cylinder Homogeneous Charge Compression Ignition (HCCI) Engine

Division of Combustion Engines, Lund Institute of Technology-Jan-Ola Olsson, Olof Erlandsson, Bengt Johansson
Published 2000-10-16 by SAE International in United States
A 6-cylinder truck engine was modified to run in HCCI-mode. The aim was to show whether or not it is possible having HCCI run a multi-cylinder engine, to provide brake values of emissions and efficiency and to verify models for engine system simulation.The work proved that it is feasible to use HCCI in multi-cylinder engines with high brake efficiency. Emissions' strong dependence on inlet temperature and octane number was demonstrated. The numerical models simulated the mean effective pressure with high precision, while inlet and exhaust pressures were less accurate, mainly due to the limitations of the turbo maps used.
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Effect of Reverse Squish on Fuel Spray Behavior in a Small DI Diesel Engine under High Pressure Injection and High Charging Condition

Isuzu Motor Co. Ltd.-Toshitaka Minami
Kitami Institute of Technology, Japan-Rahman Md. Montajir, Hideyuki Tsunemoto, Hiromi Ishitani
Published 2000-10-16 by SAE International in United States
Modern small DI diesel engines are operated at high loads and high speeds. In these engines the spray spreading on the cavity walls during the main combustion is kept approximately constant at all engine speeds to optimize the air utilization. However, spray spreading on the wall during the early and late part of combustion changes with engine speed due to the changes in air motion. At the end of impingement much of the spray moves outside the cavity due to a strong reverse squish when the injection timing is set near TDC. This causes incomplete combustion of fuel and increase emissions of HC and soot. Therefore, the study of the behavior of spray affected by the reverse squish is very important.In this study the fuel spray development under high injection pressure and high gas charging pressure was investigated photographically in a small direct injection diesel engine with a common rail injection system. Improvements in the spray distribution inside the cavity were attempted by changing the lip shape, side wall shape, and injection angle. It was…
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A Study on Trap Mechanism of Ceramic Foam*

Engineering College of Transportation-Zhang Chunrun, He Yu, Li Shumin
National Key Laboratory of Automotive Safety & Energy, Tsinghua Univ.-Zi Xinyun
Published 2000-10-16 by SAE International in United States
A three-dimension physical model of ceramic foam and a gas/solid two-phase flow model are established, in which the diesel particulate diffusion trapping and inertia collision trapping are concerned. The gas/solid flow in the three-dimension model is simulated. The diffusion trapping efficiency and inertia collision trapping efficiency are calculated under different gas flow velocities, particulate sizes and ceramic foam parameters using the numerical model. The research results deepen the understanding of trap mechanism of ceramic foam and provide the scientific basis for selecting ceramic foam parameters and designing a particulate trap that uses ceramic foam.
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Characteristics of Air Flow Surrounding Non-Evaporating Transient Diesel Sprays

University of Wisconsin-Madison-Dong-Ryul Rhim, Patrick V. Farrell
Published 2000-10-16 by SAE International in United States
Airflow characteristics surrounding non-evaporating transient diesel sprays were investigated using a 6-hole injector. Particle Image Velocimetry (PIV) was used to measure the gas velocities surrounding a spray plume as a function of space and time.A hydraulically actuated, electronically controlled unit injector (HEUI) system was used to supply the fuel into a pressurized constant volume chamber at room temperature. The chamber gas densities in this study were 10 kg/m3, 20 kg/m3 and 30 kg/m3. The injection pressure was 96.5 MPa. Two frequency doubled (532 nm) Nd:YAG lasers were used to create coincident laser sheets to illuminate the test section at two instances after start of injection (ASI). The double exposed images of sprays and Al2O3 seed particles were developed and velocity vectors of the gas surrounding the transient diesel sprays were obtained using a numerical autocorrelation PIV method.A conical control surface surrounding the spray plume was chosen as a representative entrainment surface. The maximum velocities normal and tangential to the conical control surface near the spray plume showed little variation with chamber density. Large differences between…
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