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Technical Paper

Flow, Combustion and Emissions in a Five-Valve Research Gasoline Engine

2001-09-24
2001-01-3556
The in-cylinder flow, mixture distribution, combustion and exhaust emissions in a research, five-valve purpose-built gasoline engine are discussed on the basis of measurements obtained using laser Doppler velocimetry (LDV), fast spark-plug hydrocarbon sampling, flame imaging and NOx/HC emissions using fast chemiluminescent and flame ionisation detectors/analysers. These measurements have been complemented by steady flow testing of various cylinder head configurations, involving single- and three-valve operation, in terms of flow capacity and in-cylinder tumble strength.
Technical Paper

An Experimental Study of Knock in a Natural Gas Fuelled Spark Ignition Engine

2001-09-24
2001-01-3562
Experiments were conducted on a single cylinder SI engine fuelled by natural gas. Equivalence ratios varying from 0.7 to 1.0 were used and the spark timing was changed from no knock to high knock conditions. Pressure crank angle data from 160 consecutive cycles was analysed. It was found that coefficient of variation of peak pressure (COVPP) and standard deviation of the angle of occurrence of peak pressure (SDAPP) can be used to set the engine for knock free operation. These parameters show a sudden rise from a minimum value that they attain near a spark timing where knock sets in. When the average knock intensity is low, there are two groups of cycles. The first comprises of non-knocking to slightly knocking ones. The other contains cycles with relatively high knock intensity. The sudden emergence of two groups is responsible for the observed trends of SDAPP. At high overall knock intensities the first group is absent.
Technical Paper

Low-Order Map Approximations of Lean Cyclic Dispersion in Premixed Spark Ignition Engines

2001-09-24
2001-01-3559
We investigate lean-fueling cyclic dispersion in spark ignition engines in terms of experimental nonlinear mapping functions representing the connection between past and future combustion events. Nonlinear mapping functions provide a relatively easy method for identifying the deterministic dynamics associated with lean combustion instability, even in the presence of very high levels of noise. Observed experimental maps appear to have strong similarities to those predicted by an existing nonlinear spark ignition engine model. Differences between the observed map and model predictions become more pronounced at very lean fueling and high residual fraction. Map function details are shown to be useful in model validation, identifying model deficiencies, and comparing the characteristics of different engines. We expect that such maps will also be useful for developing real-time control strategies.
Technical Paper

Experiment and Numerical Simulation of Unsteady Temperature Fields in Automotive Catalytic Converters

2001-09-24
2001-01-3563
This paper measured unsteady temperature fields of uncoated-monolith and catalytic monolith under real engine operating conditions using thermocouples. A multi-dimensional flow mathematical model of the turbulence, heat and mass transfer, and chemical reactions in monoliths was established using a computational fluid dynamics (CFD) code and numerically solved in the whole flow field of the catalytic converter. The purpose of this paper is to study unsteady warm-up characteristics of the monoliths and to investigate effects of inlet cone structure on temperature distribution of the catalytic converter. Experimental results show that the warm-up behaviors between uncoated-monolith and catalytic monolith are quite different. Simulation results indicate that the established model can qualitatively predict the warm-up characteristics.
Technical Paper

Analysis of Degree of Constant Volume and Cooling Loss in a Hydrogen Fuelled SI Engine

2001-09-24
2001-01-3561
This study analyzes the factors influencing the thermal efficiency of a homogeneous charge spark-injection (SI) engine fuelled with hydrogen, focusing on the degree of constant volume and cooling loss. The cooling loss from the burning gas to the cylinder walls is quantitatively evaluated by analyzing the cylinder pressure diagram and exhaust gas composition. The degree of constant volume burning and constant volume cooling are also obtained by fitting the Wiebe function to the rate of heat release calculated using the cylinder pressure diagram. A comparison of combustion and cooling characteristics of hydrogen and methane combustion reveals that cooling loss in hydrogen combustion is higher than that of methane combustion due to the short quenching distance and rapid burning velocity during hydrogen combustion. It is also suggested that the high cooling loss observed during hydrogen combustion reduces thermal efficiency.
Technical Paper

Plasma-Enhanced Adsorption and Reduction on Lean NOx-Catalysts

2001-09-24
2001-01-3567
The influence of adsorption and desorption processes on the non-thermal plasma enhanced catalytic reduction of NOx on NaZSM5- and Al2O3-based lean-NOx catalysts (Pt-NH4ZSM5, Cu-NaZSM5, Fe-NaZSM5, Pt-Al2O3, Pd-Al2O3, CuO-Al2O3, Ag-Al2O3) was investigated by temperature programmed reaction experiments in the temperature range from 100 °C to 600 °C. Dodecane was used as a reducing agent. Strong HC adsorption- and desorption effects were observed on the zeolite catalysts, which were not influenced by plasma-pretreatment. Adsorption of NO2 and desorption of NO occurred on Al2O3-based catalysts. By plasma-pretreatment adsorption of NO2 was induced at low temperatures. NOx-reduction rates of the catalysts Cu-NaZSM5, Fe-NaZSM5, and the Ag-Al2O3 were increased substantially by plasma-pretreatment. Both plasma-induced and catalytic oxidation of HCs were limiting factors of the NOx-reduction obtained on these catalysts.
Technical Paper

Effects of Intake Valve Closing Timing on Gasoline Engine Performance and Emissions

2001-09-24
2001-01-3564
This paper presents a study of the influence of intake valve closing (IVC) timing on the performance of the high-speed spark ignition (SI) engine, such as the output of torque and power, fuel consumption and emissions. An electrically controlled Variable Valve Timing (VVT) system based on the variable working position belt extender was developed and its pro-type was successfully set up in a 5-valve, double overhead cam (DOHC) SI engine. Test results showed that the IVC timing plays an important role in increasing the power output, decreasing the fuel consumption and CO and HC emissions under both high- and low-speed conditions as compared to the fixed IVC timing. The control of intake valve closing timing is a simple and effective means to improve engine's performance.
Technical Paper

The role of NO Selective Catalysts in the Plasma Enhanced Removal of NOx and PM from Diesel Exhausts

2001-09-24
2001-01-3568
Non-thermal plasma (NTP) systems are attracting increasing interest as candidates for future generation diesel exhaust aftertreatment technologies. Strategies are being investigated for lean NOx reduction, particulate (PM) oxidation and for combined NOx and PM aftertreatment. One approach for plasma-catalyst NOx reduction is to convert NO to NO2 with a plasma and then reduce the NO2 over a suitable catalyst. However, it has been recently suggested that particulate in the diesel exhaust may inhibit the NTP conversion of NO into NO2 in a plasma regenerating diesel particulate filter (DPF). In addition some NO2 selective catalysts are demonstrating high levels of N2O production rather than being selective to N2. It has been suggested that combined NOx and PM removal could be achieved by employing an NO selective reduction catalyst in combination with a plasma DPF. Silver-doped alumina (Ag-Al2O3) is shown to be a particularly effective catalyst for NO reduction.
Technical Paper

Hydrocarbon Reactivity in a Plasma-Catalyst System: Thermal Versus Plasma-Assisted Lean NOx Reduction

2001-09-24
2001-01-3565
The steady-state reduction of NOx at temperatures between 150-300°C has been investigated under simulated lean-burn conditions using a two-stage transient flow reactor system consisting of non-thermal plasma in combination with a sodium Y zeolite catalyst. Reactivity comparisons were made with and without plasma operation in order to identify the plasma-generated hydrocarbon species necessary for the selective catalytic reduction (SCR) of NOx. With propene as the hydrocarbon in the feed, NO is completely oxidized to NO2 in the plasma and the formation of oxidized carbon-containing species include formaldehyde, acetaldehyde, carbon monoxide, carbon dioxide, and methanol. Fourier transform infrared (FTIR) measurements indicate a close carbon balance between plasma inlet and outlet gas feed concentrations, signifying the major species have been identified.
Technical Paper

Investigation of Augmented Mixing Effects on Direct-Injection Stratified Combustion

2001-09-24
2001-01-3670
The effects of augmented mixing through the use of an auxiliary gas injection (AGI) were investigated in a direct-injection gasoline engine operated at a 22:1 overall air-fuel ratio, but with retarded injection timing such that the combustion was occurring in a locally rich mixture as evident by the elevated CO emissions. Two AGI gas compositions, nitrogen and air, were utilized, the gas supply temperature was ambient, and a wide range of AGI timings were investigated. The injected mass was less than 10% of the total chamber mass. The injection of nitrogen during the latter portion of the heat release phase resulted in a 25% reduction in the CO emissions. This reduction is considered to be the result of the increased mixing rate of the rich combustion products with the available excess air during a time when the temperatures are high enough to promote rapid oxidation.
Technical Paper

3-D PIV Analysis of Structural Behavior of D.I. Gasoline Spray

2001-09-24
2001-01-3669
Three-dimensional behaviors of direct injection (D.I.) gasoline sprays were investigated using 2-D and 3-D particle image velocimetry (PIV) techniques. The fuel was injected with a swirl type injector for D.I. gasoline engines into a constant volume chamber in which ambient pressure was varied from 0.1 to 0.4 MPa at room temperature. The spray was illuminated by a laser light sheet generated by a double-pulsed Nd:YAG laser (wave length: 532 nm) and the succeeding two tomograms of the spray were taken by a high-resolution CCD camera. The 2-D and 3-D velocity distributions of the droplet cloud in the spray were calculated from these tomograms by using the PIV technique. The effects of the swirl groove flows in the injector and the ambient pressure on the structural behavior of the droplet cloud in the spray were also examined.
Technical Paper

Characterisation of DISI Emissions and Fuel Economy in Homogeneous and Stratified Charge Modes of Operation

2001-09-24
2001-01-3671
An experimental study of the performance of a reverse tumble, DISI engine is reported. Specific fuel consumption and engine-out emissions have been investigated for both homogeneous and stratified modes of fuel injection. Trends in performance with varying AFR, EGR, spark and injection timings have been explored. It is shown that neural networks can be trained to describe these trends accurately for even the most complex case of stratified charge operation with exhaust gas recirculation.
Technical Paper

Modeling of DISI Engine Sprays with Comparison to Experimental In-Cylinder Spray Images

2001-09-24
2001-01-3667
In modeling of engine fuel-air mixing, it is desired to be able to predict fuel spray atomization under different injection and ambient conditions. In this work, a previously developed sheet atomization model was studied for this purpose. For sprays from a pressure-swirl injector, it is assumed in the model that the fuel flows out the injector forming a conical liquid film (sheet), and the sprays are formed due to the disintegration of the sheet. Modified formulations are proposed to estimate sheet parameters including sheet thickness and velocity at the nozzle exit. It was found that the fuel flow rate of a swirl injector satisfied the correlation well. Computations of correlation well. Computations of the sprays injected in an engine with a side-mounted injector were performed for conditions that duplicated a set of experiments performed in an optical engine. The computed results were compared with the spray images obtained from the optical engine using elastic (Mie) scattering.
Technical Paper

Bench Scale NOX Trap System For Diesel Applications

2001-09-24
2001-01-3666
A NOX storage and reduction approach addresses NOX emissions from mobile diesel sources. A bench scale rig system has been constructed, allowing experiments with real diesel exhaust gases under well defined conditions. The system consists of a 50 cm3 NOX storage and reduction catalyst located in a temperature controlled oven, and has the possibility of adding reducing agents, both gaseous (i.e. propene) and liquid diesel-like (e.g. heptane), into the gas stream upstream of the catalyst to subsequently react with NOX on the catalyst. A similar laboratory scale system, using a 6 cm3 NOX storage and reduction catalyst, has been used with synthetic gases of diesel exhaust-like composition, with the possibility to add a gaseous reducing agent. Factorial NOX storage and reduction experiments have been performed in the two systems.
Technical Paper

Numerical Prediction and Validation of Fuel Spray Behavior in a Gasoline Direct-Injection Engine

2001-09-24
2001-01-3668
Analysis of flow field and charge distribution in a gasoline direct-injection (GDI) engine is performed by a modified version of the KIVA code. A particle-based spray model is proposed to simulate a swirl-type hollow-cone spray in a GDI engine. Spray droplets are assumed to be fully atomized and introduced at the sheet breakup locations as determined by experimental correlations and energy conservation. The effects of the fuel injection parameters such as spray cone angle and ambient pressure are examined for different injectors and injection conditions. Results show reasonable agreement with the measurements for penetration, dispersion, global shape, droplet velocity and size distribution by Phase Doppler Particle Anemometry(PDPA) in a constant-volume chamber. The test engine is a 4-stroke 4-valve optically accessible single-cylinder engine with a pent-roof head and tumble ports.
Technical Paper

NOx Storage and Reduction on Differentiated Chemistry Catalysts for Lean Gasoline Vehicles

2001-09-24
2001-01-3665
NOx storage and reduction (NSR) catalysts are a widely investigated solution for lean gasoline applications. Open coating on metallic substrates gives a new opportunity to combine low and high temperature NSR catalysts into a converter by using differentiated chemistry on separate foils. A wide operation window for NOx conversion between 200-600°C was reached with alumina based NSR catalyst in appropriate conditions. Differentiation on separate foils can be made by NOx adsorption compounds, active metals (Pt, Rh), exhaust gas conditions or desulfation strategy. The desulfation, particularly from potassium-containing high temperature NSR catalysts, was decreased by 100°C by the addition of a small amount of TiO2. The combination of 3-way and NSR catalyst was designed by the size and lean-rich timings in laboratory and engine conditions. Low OSC PdRh (7:1) catalysts with higher loadings were used as 3-way catalysts.
Technical Paper

Integration of Engine Controls, Exhaust Components and Advanced Catalytic Converters for ULEV and SULEV Applications

2001-09-24
2001-01-3664
Development of integrated engine controls, exhaust components and advanced catalytic converters was demonstrated on a 1998 full size luxury sedan with a gasoline PFI 4.4 L V8 engine. This level of emissions management was targeted for ULEV and SULEV emission standards. An air gap, dual exhaust, six-catalyst system, was modified in stages to reduce the number of catalysts and associated controls/hardware. Engine controls and calibration were developed to reduce cold-start emissions, catalyst light-off time and tailpipe emissions. Systems integration involved reduced precious metal loading, secondary AIR and modification of emission control devices. The thermal mass of the air gap exhaust pipes was reduced by approximately 30 percent, which contributed to improved catalyst heat-up time. A vacuum-insulated catalytic converter with phase change material was used to store exhaust heat and resist heat loss during times of dwell/soak.
Technical Paper

Designed Experiment to Evaluate the Canning Strength of Various High Cell Density / Ultra Thin Wall Ceramic Monoliths

2001-09-24
2001-01-3663
High cell density (HCD) (≥ 600 cpsi) and /or ultra thin wall (UTW) (≤ 4 mil) extruded ceramic monolith substrates are being used in many new automotive catalyst applications because they offer (1) increased geometric surface area, (2) lower thermal mass, (3) increased open frontal area and (4) higher heat and mass transfer rates. Delphi has shown in previous papers how to use the effectiveness, NTU theory, to optimize the various benefits of these HCD / UTW catalysts. A primary disadvantage of these low solid fraction substrates is their reduced structural strength, as measured by a 3-D hydrostatic (isostatic) test. The weakest of these new substrates is only 10 to 20% as strong as standard 400 × 6.5 substrates. Improved converter assembly methods with lower, more uniform forces will likely be required to successfully assemble converters with such weak substrates in production.
Technical Paper

A Comparison of Steady, Pulsating Flow Measurements and CFD Simulations in Close Coupled Catalysts

2001-09-24
2001-01-3662
Performance improvements of automotive catalytic converters can be achieved by improving the flow distribution of exhaust gases within the substrate. The flow distribution is often assumed to be adequately described by measurements obtained from steady flow rigs. An experimental study was carried out to characterise the flow distribution through the substrate of a close-coupled catalytic converter for both steady and pulsating conditions on a flow rig and on a motored engine. Computational fluid dynamic (CFD) simulations were also performed. On the flow rig, the flow from each port was activated separately discharging air to different regions of the substrate. This resulted in a high degree of flow maldistribution. For steady flow maldistribution increased with Reynolds number. Pulsating the flow resulted in a reduction in flow maldistribution. Different flow distributions were observed on the motored engine when compared to composite maps derived from the rig.
Technical Paper

An Approach to Clean Snowmobile Design: Implementation of a 4-Cycle Low Emission Vehicle Engine

2001-09-24
2001-01-3661
The purpose of this document is to give the reader brief insight into the basic concepts, principles, and reasoning as applied to environmentally sensitive snowmobile design. Although a snowmobile is a conglomeration of multiple systems and components, the focus of this article shall be upon the design of components that form the foundation for a successful Clean Snowmobile Challenge entry-the powerplant. This paper briefly covers the conceptual design process, and a rationalized powerplant solution for a clean, quiet snowmobile. In addition, a detailed description of a four-stroke, three-cylinder powerplant implementation and the required modifications to an Arctic Cat snowmobile chassis are included. The results of the modified snowmobile's performance at the Clean Snowmobile Challenge 2001 are visited. In general, the overall performance of the modified snowmobile was satisfactory; its strengths are: reliability, robust construction, aesthetic appearance, and noise suppression.
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