Gopichandra Surnilla

NOx Release Characteristics of Lean NOx Traps During Rich Purges

This paper summarizes results from a large study on the release of NO x from a lean NO x trap during rich purges. Under certain purge conditions, some NO x trap formulations have the propensity to release some of the NO x stored during previous lean operation without reducing it. This purge NO x release was examined for different NO x trap formulations. The purge NO x release was evaluated for one of the formulations as a function of several variables, including the aging condition of the trap, the trap temperature, the trap volume, the purge A/F ratio, the purge flow rate, and the amount of NO x stored. The effect of hot lean pretreatments on the purge NOx release was studied. In addition, the effect of the rhodium level on the purge NO x release was examined. Mechanisms for the NO x release are proposed that are consistent with the observed data. The results indicate that the purge NO x release is very low for thermally aged traps and is primarily a concern for fresh or stabilized traps. The release of NO x is a very strong function of temperature and increases as the oxygen storage capacity (OSC) of the trap increases. The NO x release can be minimized by using shorter lean periods (i.e., less NO x storage) and by performing very rich purges under high flow conditions. Larger trap volumes help to lower the NO x release at 400°C and below; the data suggest that some of the NO x released from the front of the trap is readsorbed and converted on subsequent sections of the trap. Higher loadings of rhodium help decrease the NO x release at low temperatures (e.g., 250°C). Hot lean pretreatments of even short duration increase the NO x release during the subsequent storage and purge cycle, presumably due to oxidation of the precious metal. At temperatures of 350°C and above, it is proposed that a major cause of NO x release is due to the reaction between the reductants (i.e., CO, HC, and H 2 ) and oxygen from the oxygen storage components in the washcoat. The resulting exotherm raises the local temperature of the washcoat, including the NO x storage sites nearby. If the temperature before the purge is higher than the peak storage temperature of the trap (i.e., in the range of decreasing NO x capacity) and the amount of NO x stored is near the maximum capacity at that temperature, then the exotherm causes NO x to be released in order to bring the amount of NO x storage back to the maximum level that can exist at the higher temperature. Similarly, the exotherm from reducing some of the stored NO x can cause NO x that is still stored to be released, particularly for large amounts of NO x storage. Another source of NO x release occurs at temperatures above 500°C because, as the front of the trap is being purged, the rear part of the trap is exposed to stoichiometric conditions with very low levels of oxygen and reductants. The adsorbed nitrates become unstable in the absence of oxygen, and at these high temperatures, the rate of nitrate decomposition becomes rapid enough to result in additional NOx release. Due to the low levels of reductants, the released NO x escapes from the trap without being reduced.

Vibration-based NVH control during idle operation of an automobile powertrain

A system and method of operating a vehicle powertrain that employs active control to reduce NVH, particularly during idle. The method includes selectively operating the powertrain in at least a non-idle condition and an idle condition; receiving vibration signals from a sensor disposed on an internal combustion engine; controlling spark timing of the internal combustion engine based on vibration signals received from the sensor; and during the idle condition, modifying a speed and/or a load of the internal combustion engine based on vibration signals received from the sensor.

Spark ignition engine torque management

Presented in this paper is a robust feedback controller design procedure to regulate the torque of a spark ignition engine equipped with an electronic throttle mass air flow controller. To this end, a system level model of engine torque production is experimentally determined. Next, a crank-angle domain H/sub /spl infin// controller is designed to control the engine torque with zero steady state errors while addressing the nonlinear system characteristics and pure delay. The controller design methodology applied to the torque control problem is presented and an interpretation of the controller provided. The engine dynamometer data acquired from a Ford 4.6L V8 engine demonstrates the H/sub /spl infin// controller successfully rejects the noise and disturbances while meeting transient and steady state performance objectives.

Characterization and Speciation of Fuel Oil Dilution in Gasoline Direct Injection (DI) Engines

Fuel dilution in oil is a known issue for gasoline direct injection (DI) engines especially in colder climates and for customers with short, lightly-loaded driving cycles. In this work, oil samples were generated using a cold oil fuel accumulation test. Gas chromatography (GC) was used to speciate the hydrocarbons accumulated in the oil and characterize their quantity, type, molecular weight distribution, and volatility. Further testing and analysis was done to characterize the fuel hydrocarbons that evaporate from oil during engine warm-up conditions. The results demonstrate how the wide range of gasoline hydrocarbon volatility leads to different behavior in the accumulation and subsequent evaporation phases. Lastly, a model was created to extend this analysis and estimate the evaporation of hydrocarbons from the oil.Copyright

Model-based ethanol blend estimation in flexible-fuel vehicles:

This paper presents a model-based strategy estimating the ethanol content of an ethanol–gasoline blended fuel in flexible fuel vehicles. A steady-state parametric model relating engine speed, throttle angle, and air–fuel ratio to the fuel injector pulse-width is developed from physics. The parameters of this model are adapted and linked to percentage of ethanol content via a suitably defined metric. The proposed steady-state model structure is experimentally validated on a 2005 5.4L V8 Ford engine. The developed ethanol content estimation methodology is justified based on the combustion chemistry and physics involved. The methodology developed has a distinct advantage over previously proposed methods as it uses only the existing sensor set on a production vehicle.

Model-based estimation of ethanol content in flexible fuel vehicles

Presented in this paper is a model-based method for accurately estimating the percent ethanol content of an ethanol-gasoline fuel blend used in flexible fuel vehicles (FFVs). Few methods exist in literature addressing the problem of ethanol estimation in production FFVs. The proposed approach has a distinct advantage as it uses the existing sensor set on a production vehicle. Measurements from the sensors are used to adapt a steady state parametric model relating the engine speed, throttle angle opening and the air-fuel ratio to the fuel injector pulse width command. A first-principles physics-based approach is used to develop the model structure. The fuel composition information is embedded in the adapted model coefficients whose variation is used for ethanol content estimation. The method is validated with experiments on a 2005 Ford 5.4-L V8 port fuel injected engine.