Air-Fuel Ratio Sensor Utilizing Ion Transportation in Zirconia Electrolyte

Sasayama, Takao; Yamauchi, Teruo; Byers, R. Lee; Suzuki, Seikoo; Ueno, Sadayasu

doi:10.4271/910501

Cited by 6 publications

(6 citation statements)

References 2 publications

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“…The emf of the sensing cell is normally fixed at 300-450 mV with respect to the air reference, which gives an oxygen pressure of about 10 −7 -10 −10 atm in the cavity at 800°C. The current that must pass through the pumping cell to maintain a constant oxygen pressure (10 −7 -10 −10 atm) in the sensing cell is used as an output of the sensor [28][29][30][31]. In the oxidizing atmosphere of a lean combustion gas, oxygen has to be pumped out to reduce the oxygen pressure in the cavity as shown in Fig.…”

Section: Oxygen Sensormentioning

confidence: 99%

Solid-state electrochemical gas sensors

Park

Fergus

Miura

et al. 2009

Ionics

137

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The solid-state electrochemical principle has been a selective and accurate way of sensing chemical components in various environments, including liquid metal, for an extended period of time. Since after Carl Wagner's interpretation of zirconia, there appeared many advances in chemical sensor applications. The electrochemical techniques for the chemical measurements have, in general, several major advantages compared to other methods. The information of interest is directly converted into electrical signal which may be employed in electronic circuits. Electrochemical measurements are always selective for the quantities that undergo the electrochemical redox reaction. In most cases, reactions at equilibrium are considered, but techniques have also been developed to be able to use kinetic limit. Furthermore, the signal is independent of materials properties, such as the ionic conductivity or impurity as long as it is a predominant ionic conductor. Depending on the type of application, voltage or current measurements are employed. While potentiometric method commonly allows measuring chemical species over a wide range of concentration, amperometric sensors generally cover a quite limited range but have a much higher resolution. In this paper, various principles of electrochemical techniques to measure the chemical quantities are introduced. And there are many examples of the status of researches on electrochemical sensors, such as oxygen sensor, carbon dioxide sensor, NO x sensor, SO x sensor, and hydrogen sensor.

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Section: Oxygen Sensormentioning

confidence: 99%

Solid-state electrochemical gas sensors

Park

Fergus

Miura

et al. 2009

Ionics

137

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“…Using the potential condition in Eq. 21, one can now reformulate the boundary condition 20 at the working electrode, Y = 1, as [21] = + exp[2C - [22] exp[2((1) -)1j] [33] [ 23] and this equation, together with Eq. 27-31 for the gas phase can be solved for 'I'(l) and the mole fractions x1 at the electrode surface.…”

Section: Simplifications Of the Model Equationsmentioning

confidence: 99%

“…The key assumption is that ECe and €Ch are negligibly small in comparison to C.,, so that, by electroneutrality, C., is equal to the constant doping concentration. The concentrations Ce and Ch generally take their maxima at one of the electrodes, and these values can be determined from the potential condition 21 C3=-+11 ZhDht(l) requirement that C,, and C3 have their reference values at the counterelectrode (Y = 0). For the base case discussed in the next section, C3 = C3 250 at the counterelectrode.…”

Section: Simplifications Of the Model Equationsmentioning

confidence: 99%

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Theory and Simulation of Solid‐Electrolyte Wide‐Range Sensors for Combustion‐Gas Streams

Baker

1996

J. Electrochem. Soc.

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Clarification of the complex chemical processes governing polarized wide-range air-to-fuel-ratio sensors should enable one to determine characteristics of the system geometry and physical properties necessary for successful sensor operation. To develop a mathematical description of these sensors, we have combined well-established theories for electron, electron-hole, and oxygen-vacancy transport within yttria-stabilized zirconia with transport equations that apply to gaseous diffusion within the dense, porous layer that covers the solid electrolyte. Along the interface between the solid electrolyte and the porous layer, a thin platinum electrode catalyzes various chemical reactions and an electrochemical charge-transfer reaction. The model equations have been simplified using an asymptotic analysis which is valid over a broad range of conditions of practical interest; in particular, it is valid for all simulations presented in this work. Model calculations are shown to compare well with experimental data, and acceptable ranges for the four dimensionless groups that dictate sensor performance are considered.lnfroduction The need to improve fuel economy and reduce unwanted emissions associated with internal combustion engines has promoted research into sensors that can determine airto-fuel ratios over a wide range of operating conditions, which can lead to an improved closed-loop control system.' It is possible that a wide-range sensor (WRS) will eventually replace the present potentiometric exhaustoxygen sensor (EOS),2-4 which provides only a binary response that indicates whether the engine is operating lean or rich.58 Before a WRS is to become used widely, it is likely that an economical catalyst system capable of reducing nitrogen oxides in a lean exhaust stream will be required, so that advantages such as fuel savings and reductions in hydrocarbon emissions obtained by operating an engine in the lean condition can be realized without excessive nitrogen oxide emissions.9 Conversely, when high power is demanded from an engine, a feed stream rich in fuel is often required; under such conditions, a WRS could determine quantitatively the degree to which the exhaust is rich in combustibles, and the resulting airfuel control system could reduce hydrocarbon emissions.A schematic illustration of a WRS based on an oxygentransporting solid electrolyte is shown in Fig. 1. The importance of these sensors has led to a large number of publications and patents over the past 20 years. The patent by Bhagat and Howarth'2 and those by Wang et al.13 provide a substantial listing of early United States patents issued on this topic area. References 14-27 describe sensors constructed with materials and geometries close to or analogous to that which is addressed in this communication, and references cited in these documents can be consulted for related studies. In addition, a number of relatively recent review articles discuss the construction and operation of zirconia-based wide-range sensors,2831 and the reviews in Ref. 32-35 presen...

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“…It is interesting to note that the relationship between the equivalence ratio and the exhaust gas composition is independent, to good approximation, of the engine's revolutions per minute and other operating conditions. (See, for example, Figure 6 of Sasayama et al, 1991. ) A typical plot of the exhaust-gas concentrations considered in this work vs. the equivalence ratio is given in Figure 1 (Logothetis, 1981).…”

Section: Introductionmentioning

confidence: 99%

Mathematical analysis of potentiometric oxygen sensors for combustion‐gas streams

Baker

1994

AIChE Journal

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Air-Fuel Ratio Sensor Utilizing Ion Transportation in Zirconia Electrolyte

Cited by 6 publications

References 2 publications

Solid-state electrochemical gas sensors

Solid-state electrochemical gas sensors

Theory and Simulation of Solid‐Electrolyte Wide‐Range Sensors for Combustion‐Gas Streams

Mathematical analysis of potentiometric oxygen sensors for combustion‐gas streams

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