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Technical Paper

Fuel Economy Benefit of Cylinder Deactivation - Sensitivity to Vehicle Application and Operating Constraints

2001-09-24
2001-01-3591
A Variable Displacement Engine (VDE) improves fuel economy by deactivating half the cylinders at light load. The actual fuel economy benefit attained in the vehicle depends on how often cylinders can be deactivated, which is a function of test cycle, engine size, and vehicle weight. In practice, cylinder deactivation will also be constrained by NVH (noise, vibration, and harshness). This paper presents fuel economy projections for VDE in several different engine and vehicle applications. Sensitivity to NVH considerations is quantified by calculating fuel economy with and without cylinder deactivation in various operating modes: idle, low engine speed, 1st and 2nd gear, and warm-up after cold start. The effects of lug limits and calibration hysteresis are also presented.
Technical Paper

Effects of Fuel Properties on the Mixture Formation under the Stratified-Charge Combustion Condition of Direct-Injection Gasoline Engine

2001-09-24
2001-01-3590
In order to clarify the effects of fuel properties on the mixture formation under the stratified-charge combustion condition in a direct-injection gasoline engine, fuel concentration measurement in the vicinity of the ignition plug was established using a fast response flame Ionization detector (FID). A single-cylinder direct-injection gasoline engine, for which a Toyota D-4 engine was modified, was used. Paraffin, olefin, naphthene and ether having a boiling point of approximately 50°C, and paraffin, olefin and an aromatic compound having a boiling point of approximately 100°C were used as candidate fuels. As a result, the effect of boiling point on the mixture formation was clarified.
Technical Paper

Understanding Oil Aging in Extended Drain Axle & Transmission Applications

2001-09-24
2001-01-3592
Extended drain of axle and transmission lubricants has gained wide acceptance in both passenger car and commercial vehicle applications. Understanding how the lubricant changes during extended drain operations is crucial in determining appropriate lubricants and drain intervals for these applications. A suitable aging screen test with an established relationship to field performance is essential. Over the years numerous methods have been studied (DKA, GFC, ISOT, ASTM L-60) with varying degrees of success1,2,3. Current methods tend to be overly severe in comparison to field experience, hence the need for further work in this area. As a result of recent work, a lubricant aging test method has been developed which shows good correlation with field experience, giving us an effective tool in the development of long drain oils.
Technical Paper

ATF Additive Effects on Hot Spot Formation in Wet Clutches

2001-09-24
2001-01-3594
Wet clutch interfaces that operate in high-energy environments experience significant frictional heating. Under such conditions, thermoelastic or thermoplastic instabilities may lead to a transition from evenly distributed surface contacts to unevenly distributed regions that manifest themselves as hot spots on the separator plate. The critical power at which these instabilities occur depend on the thermal conductivity, thermal expansion, and stiffness of the components. Modeling has shown that for wet clutch interfaces the stiffness of the friction material has a dominant influence on the critical power. We have found that the lubricant additive package also plays a significant role in the onset of hot spots. In this paper, we report the influence of antiwear systems on the occurrence of hot spots.
Technical Paper

Contribution of Liquid Fuel to Hydrocarbon Emissions in Spark Ignition Engines

2001-09-24
2001-01-3587
The purpose of this work was to develop an understanding of how liquid fuel transported into the cylinder of a port-fuel-injected gasoline-fueled SI engine contributes to hydrocarbon (HC) emissions. To simulate the liquid fuel flow from the valve seat region into the cylinder, a specially designed fuel probe was developed and used to inject controlled amounts of liquid fuel onto the port wall close to the valve seat. By operating the engine on pre-vaporized Indolene, and injecting a small amount of liquid fuel close to the valve seat while the intake valve was open, we examined the effects of liquid fuel entering the cylinder at different circumferential locations around the valve seat. Similar experiments were also carried out with closed valve injection of liquid fuel at the valve seat to assess the effects of residual blowback, and of evaporation from the intake valve and port surfaces.
Technical Paper

Thermochemical Behaviour of Producer Gas from Gasification of Lignocellulosic Biomass in SI Engines

2001-09-24
2001-01-3586
A study about the utilisation of producer gas from gasifiers for obtaining mechanical energy in a SI engine is presented in this work. Therefore, the influence of the gas composition and its thermodynamic properties on the combustion characteristics and on the engine performance are analysed. A home-made chemical equilibrium model which considers 28 chemical species was used to calculate the gas composition as a function of the gasification conditions, and to study the influence of the gas composition on some thermochemical parameters such as adiabatic flame temperature and heat release. The chemical kinetic package CHEMKIN III was also used to study its autoignition behaviour. Finally, a quasi-dimensional two-zone model for SI engines was used to calculate the knock tendency and to analyse the effect of fuel composition on some combustion parameters related to engine performance (IMEP, cylinder pressure, etc.).
Technical Paper

No Major Backsliding in Air Quality when Replacing MTBE with Isooctane in CARB Gasoline

2001-09-24
2001-01-3588
Plans to ban MTBE (Methyl tertiary-Butyl Ether) have led to discussions on how the gasoline in California will be formulated without any backsliding in air quality. One possibility is to replace MTBE with isooctane. Exhaust emissions using California Phase II gasoline with MTBE, were compared to a gasoline where MTBE had been replaced with isooctane. Regulated, particulate, carbon dioxide, and PAH (polyaromatic hydrocarbons) emissions were measured at 22 °C temperature for 8 vehicles using the European cycle for year 2000 (ECE+EUDC). One of the vehicles was a GDI (Gasoline Direct Injection), one was a carbureted model without a catalytic converter, and the others were equipped with multi point fuel injection and catalytic converters. Results indicate that no major backsliding in air quality can be expected when replacing MTBE with isooctane. NOx (nitrogen oxides) emissions were reduced in all vehicle types. CO emissions increased in the vehicle without a catalytic converter.
Technical Paper

Hybrid Fuel Technique for CO2 Reduction in SI Engines

2001-09-24
2001-01-3589
This paper describes a new hybrid fuel technique for improving the thermal efficiency and fuel economy of SI engines. A new type of fuel additive that has friction modification effects was evaluated. By treating gasoline with this additive, a fuel economy benefit of up to 2.4%, which means a 2.4% reduction in carbon dioxide emissions from vehicles, has been attained in a modified Japanese 10-15 mode test. Improvements in the engine power and vehicle acceleration were also observed due to application of this technique. No-harm tests were also conducted, and it was found that this technique exhibited no significant harmful side effects in the tests conducted in this program.
Technical Paper

Considering the Effects of Cyclic Variations when Modeling the Performance of a Spark Ignition Engine

2001-09-24
2001-01-3600
Abstract An approach for simulating cyclic variations in spark ignition engines is described. It is based on a stochastic modeling coupled to a comprehensive model developed for predicting engine performance, mainly for gas-fueled engine applications. Such an approach is shown capable of generating cycle to cycle variations of pressure-time development records that are in good agreement with experiment. An account of the corresponding extent of cyclic variation in major performance parameters can be also established. It is demonstrated that the probability of the incidence of knock can be determined for any set of operating and design conditions while using this approach with sufficiently comprehensive detailed chemical kinetics. Examples involving mainly methane operation are shown.
Technical Paper

Improvement of Engine Heat-Transfer Calculation in the Three-Dimensional Simulation Using a Phenomenological Heat-Transfer Model

2001-09-24
2001-01-3601
Improvement of heat-transfer calculation for SI-engines in the three-dimensional simulation has been achieved and widely been tested by using a phenomenological heat-transfer model. The model is based on the local application of an improved Re-Nu-correlation (dimensional analysis) proposed by Bargende [1]. This approach takes advantage of long experience in engine heat transfer modeling in the real working process analysis. The results of numerous simulations of different engine meshes show that the proposed heat-transfer model enables to calculate the overall as well as the local heat transfer in good agreement with both real working process analyses and experimental investigations. The influence of the mesh structure has also been remarkably reduced and compared to the standard wall function approach, no additional CPU-time is required.
Technical Paper

Numerical Analysis of Gas Exchange and Combustion Process in a Small Two-Stroke Gasoline Engine

2001-09-24
2001-01-3602
This paper analyses the scavenge process of a conventional two-stroke engine in order to find ways to significantly reduce the scavenge losses by applying a combination of 1D and 3D simulation procedures. A special evaluation method was developed which allows a clear distinction between the main hydrocarbon loss mechanisms. Furthermore, the paper presents an approach to simulate the highly turbulent combustion at a speed of 9000 rpm. The results of the numerical investigations are compared with experimental results. The engine chosen for this purpose was a 64 cm3 four-port production two-stroke engine. The CFD calculations were performed using the finite volume CFD code STAR-CD. The mesh generation process was automated using pro*am. Combustion was modelled with the one-equation Weller flamelet model. The results of the present study show that the combination of 1D and 3D simulation procedures is a powerful tool for further investigations (e.g. stratified charge, GDI).
Technical Paper

Measurement and Simulation of Turbulent Flame Propagation in a Spark Ignition Engine by Using Fractal Burning Model

2001-09-24
2001-01-3603
The several burning models based on the wrinkled laminar flame concept had been proposed and applied to the turbulent premixed flame in a spark ignition engine. Fractal burning model is one of the flamelet burning models. However the formulations of fractal characteristics such as fractal dimension, inner cutoff scale and outer cutoff scale weren't established. These formulations based on the results of the fractal analysis in a constant volume vessel and a spark ignition engine were proposed in this study. The fractal dimension is expressed as a function of non-dimensional turbulence intensity and the density of mixture. Non-dimensional inner cutoff scale is expressed a function of Karlovitz number. Outer cutoff scale is equal to the flame radius. Finally the quasidimensional model for turbulent combustion was performed by using the fractal burning model with our formulations.
Technical Paper

Comparison of Extended Service Lubricants for Heavy-Duty Transmissions and Axles

2001-09-24
2001-01-3595
Over the past several years, economic pressures have driven fleets to substantially increase their maintenance intervals. To meet this challenge, both the Original Equipment Manufacturers (OEMs) and the lubricant suppliers have developed new and better products to give fleet users the benefits of extended service intervals, while at the same time maintaining equipment life and providing the potential for reduced operating costs. Through the selection of proper lubricants, fleets can now minimize their total operating costs with products that meet the OEM extended service specifications, have demonstrated equipment durability, and are formulated using base oil and additive components to minimize the cost of the lubricant. This paper will examine the options available for formulating extended drain transmission and axle lubricants. It will explore the selection of the lubricant base oil as well as the additive system.
Technical Paper

A Hydrodynamic Contact Algorithm

2001-09-24
2001-01-3596
Today, mechanical systems such as the piston groups of internal combustion engines are simulated using Multiple Body-System (MBS) - approaches. However, the use of these models is restricted to a few problems as their adaptability is limited. The simulation of mechanical systems only by means of finite elements shows great promise for the future. In order to consider lubrication effects between two touching bodies of a mechanical system, a hydrodynamic contact algorithm (HCA) for finite element (FE) applications was developed. This paper discusses the technical background and first results for the simulation of a piston group using this new approach.
Technical Paper

IP 451 Aromaticity as an Alternative Base Oil Quality Parameter for ASTM D 2007 Saturates

2001-09-24
2001-01-3598
This paper describes the relation between the ASTM D 2007 saturates and the IP 451 aromaticity by molecular modeling and by a direct correlation using a wide range of commercial base oils. The correlation shows that the 90 % mass ASTM D 2007 limit defined in the API and ATIEL base oil group definitions corresponds with a 1.7 % mole IP 451 limit. The results demonstrate that the IP 451 aromaticity can be used to replace the ASTM D 2007 saturates content in the API and ATIEL base oil quality definitions and interchange guidelines. This method provides advantages in terms of precision and is also more significant in describing base oil oxidation performance.
Technical Paper

Quantification of Active Antioxidants by FTIR Spectroscopy and the Correlation to Measured TBN Values

2001-09-24
2001-01-3599
Total base number (TBN) measurement is traditionally used to assess the ability of an engine oil to neutralize the generated acids during engine operation. Although such measurements are informative, they can only determine the total quantity of the remaining antioxidants in the engine oil, and not the amount of active antioxidants that can effectively neutralize the acids. The work presented here investigates the activity of antioxidants in fresh and used engine oils by Fourier Transformed Infrared Spectroscopy (FTIR) and their correlation to the TBN values obtained by titration. The method is based on the reaction of an acid solution with the alkaline ingredient of the engine oil in a non-polar solvent that mimics the actual environment experienced by the antioxidants. FTIR Spectroscopy is used to monitor the consumption of the acid. The decrease in peak intensity of the acid is then employed to quantify the remaining active antioxidants through a calibration curve.
Technical Paper

Ammonia Emissions from the EPA's Light Duty Test Vehicle

2001-09-24
2001-01-3538
Ammonia (NH3) emissions were measured from the EPA's Light Duty Test Vehicle while operated on a chassis dynamometer. The vehicle's (1993 Chevrolet equipped with a three-way catalyst) emissions were measured for three transient (urban driving, highway fuel economy, and hard acceleration) cycles and steady state operation. Previous research1, 2 has shown that NH3 is predominately emitted from vehicles with a catalyst (three-way or dual-bed). The vehicle's catalyst is designed to reduce nitrogen oxides (NOx) to nitrogen (N2) and oxygen (O2) during normal operation. The reduction of NOx to NH3 occurs during periods of reducing conditions when insufficient O2 is available. NH3 emissions were measured during fuel-rich/reduced-O2 conditions (open-loop control scheme). The results demonstrate that NH3 production is correlated to combustion conditions3.
Technical Paper

Air-to-fuel Ratio Modulation Experiments over a Pd/Rh Three-way Catalyst

2001-09-24
2001-01-3539
The benefits of deliberately modulating air-to-fuel ratio over a three-way catalyst are disputed. In this work, engine test cell experiments were carried out to assess the performance of a warmed-up Pd/Rh three-way catalyst. The objectives were threefold: first, to determine the best mode of operation; second, to determine if air-to-fuel ratio modulation enhances robustness to transient air-to-fuel ratio disturbances; third, to determine if the conversion efficiency can be manipulated by controlling the shape of the air-to-fuel ratio oscillation. It was observed that the highest conversion efficiency is obtained using a steady air-to-fuel ratio just rich of stoichiometric; however, this mode of operation lacks robustness with respect to transient disturbances and UEGO sensor errors. Robustness can be improved using an oscillating air-to-fuel ratio, but with a sacrifice in peak conversion efficiency.
Technical Paper

Relationships Between Instantaneous and Measured Emissions in Heavy Duty Applications

2001-09-24
2001-01-3536
Selective Catalytic Reduction (SCR), using urea injection, is being examined as a method for substantial reduction of oxides of nitrogen (NOx) for diesel engines, but the urea injection rates must be controlled to match the NOx production which may need to be predicted during open loop control. Unfortunately NOx is usually measured in the laboratory using a full-scale dilution tunnel and chemiluminescent analyzer, which cause delay and diffusion (in time) of the true manifold NOx concentration. Similarly, delay and diffusion of measurements of all emissions cause the task of creating instantaneous emissions models for vehicle simulations more difficult. Data were obtained to relate injections of carbon dioxide (CO2) into a tunnel with analyzer measurements. The analyzer response was found to match a gamma distribution of the input pulse, so that the analyzer output could be modeled from the tunnel CO2 input.
Technical Paper

Operating Envelopes of Hybrid Bus Engines

2001-09-24
2001-01-3537
Recent chassis testing of hybrid buses demonstrated the potential of hybrid technology to reduce emissions and raise fuel economy relative to conventional buses. However, hybrid buses represent a certification quandary because the engines must be certified using the accepted Federal Test Procedure (FTP), without regard for benefits that may arise from less transient engine operation. Actual engine operating data from series configuration hybrid buses were analyzed to determine the envelopes of torque and speeds covered by the engine. Transient engine operation was also considered in terms of rates of change of torque, power and speed. These measures did not compare closely with similar measures computed from the FTP because the series hybrid engines explored a more structured zone of operation than the FTP implied and because the FTP represented more transient operation.
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