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Automotive fuel injectors have been adapted with electrodes that enable negative electric charge to be inserted into the fuel flowing through the injector. Because the fuel is electrically very insulating and flowing rapidly, a significant amount of charge is retained in the fuel as it issues from the injector. Once exposed to the atmosphere, the charge laden fuel both atomizes and spatially disperses due to electrostatic forces. By varying the amount of inserted charge, the spray pattern can be varied significantly. This added variability allows the possibility of changing the fuel presentation when fuel is injected into the intake port of a typical spark ignited engine. A variable presentation may be useful for optimizing fuel evaporation within the port, with a corresponding reduction of exhaust emissions, during the cold start period of the engine when those parameters affecting evaporation are changing both temporally and spatially.

Exhaust gas air-fuel ratio (A/F) sensors are common devices in powertrain feedback control systems aimed at minimizing emissions. Both resistive (using TiO2) and electrochemical (using ZrO2) mechanisms are used in the high temperature ceramic devices now being employed. In this work a new mechanism for making the measurement is presented based on the change in the workfunction of a Pt film in interaction with the exhaust gas. In particular it is found that the workfunction of Pt increases reversibly by approximately 0.7 V at that point (the stoichiometric ratio) where the exhaust changes from rich to lean conditions. This increase arises from the adsorption of O2 on the Pt surface. On returning to rich conditions, catalytic reaction of the adsorbed oxygen with reducing species returns the workfunction to its original value. Two methods, one capacitive and one thermionic, for electrically sensing this workfunction change and thus providing for a practical device are discussed.

A piezoelectrically driven vibrating cantilever blade is damped by a number of mechanisms including viscous damping in a still fluid and aerodynamic damping in a flow. By measuring the damping of devices operating at resonance in the 1 to 5 kHz region, one can measure such properties as mass flow, absolute pressure or the product of molecualar mass and viscosity. In the case of the mass flow measurement, the device offers a mechanical alternative to hotwire and hot film devices for the automotive application.

Two new, sensor concepts using small, piezoelectrically driven, vibrating cantilever blades are described. A magnetic-field sensor is realised by depositing a multiturn planar coil of aluminum on the blade. When the blade is driven at a cantilever resonance (1–3 kHz) in the presence of a magnetic field, an ac emf is induced in the coil proportional to the field strength at the site of the coil, Operation is exactly analogous to that of an ac generator. In a gas-sensitive device, an air gap is established by placing the blade of the cantilever a few millimeters from a multilayer ceramic piezoelectric actuator. When the actuator is driven at the resonance frequency of the blade, the vibration induced in the blade by means of the gas coupling is “read out” with a piezoelectric element attached to the base of the blade. The pressure or average atomic mass of the gas can be sensed by monitoring the amplitude of the blade.

An oxygen sensor based on electrochemical pumping is described which is capable of measuring with high sensitivity A/F over an extended range from very lean to very rich A/F values. The sensor output is approximately proportional to A/F, has a weak dependence on temperature and is essentially independent of the gas pressure.