Estimating IC engine exhaust gas lambda and oxygen from the response of a universal exhaust gas oxygen sensor

Abstract

Universal exhaust gas oxygen sensors (UEGOs) are in widespread use in internal combustion engines where they are used to measure lambda (the non-dimensional air–fuel ratio) and oxygen concentration (). The sensors are used on production engines and for research and development. In a previous paper, a model of the UEGO sensor was presented, based on a solution of the Stefan–Maxwell equations for an axisymmetric geometry, and it was shown that for a known gas composition, predictions of the sensor response agreed well with experiment. In the present paper, the more ‘practical’ problem is addressed: how well can such a model predict λ and based on the sensor response? For IC engine applications, a chemistry model is required in order to predict λ, and such a model is also desirable for an accurate prediction of . A fast (matrix exponential) method of solving the Stefan–Maxwell equations is also introduced, which offers the possibility of a near real-time computation of λ and , with application, for example, to bench instruments. Extensive results are presented showing how the interpretation of the UEGO response may be compromised by uncertainties. These uncertainties may relate not only to the sensor itself, such as temperature, pressure and mean pore diameter, but also the chemistry model.

Internal combustion engine exhaust gas analysis

“…An immediate conclusion is that only the Spindt method has resulted in a realistic prediction of l. There is no doubt that the engine is running at very close to l = 1. The Spindt relationship gives l = 0:9997 (the slightly richer UEGO result of 0.9948 is expected, as is argued in a recent paper 9 ). The fact that the Spindt method makes a good prediction of l in this case is unsurprising -from the Spindt relationship (equation 22) in approximate form (see also the aside following equation B9), it is apparent that for conditions where the noxious emissions and oxygen are virtually negligible that l 6 ¼ f(X CO 2 ).…”

“…The Spindt prediction is from the raw data and is thus identical to that in Figure 1. It is intriguing that the UEGO l measurement is not the same as that predicted from the gas analysis but is almost identical to that of a UEGO model (green dots), described in Collings et al 9 Perhaps, most surprising is the 'error' at l;1, which is about 0.01. This bias is due to the fact that X CO ;8000 ppm and X H 2 ;2300 ppm at this condition -much bigger values than these would be predicted at equilibrium.…”

Laser-Induced Fluorescence Detection of Hot Molecular Oxygen in Flames Using an Alexandrite Laser

“…Hot oxygen, i.e., oxygen in excited vibrational and electronic states, is of particular interest, for instance, in plasma physics, 1 where it is generated when oxygen atoms recombine or an oxygen molecule collides with an electron, 2 in atmospheric chemistry, 3 where photolysis of ozone by ultraviolet (UV) radiation is a common mechanism to form excited oxygen in the stratosphere and mesosphere; 4 and in combustion technology, where excited oxygen molecules are used in plasma-assisted flames 5 and residual oxygen in the hot exhaust gas is a key parameter in judging the performance of a combustor. 6 This work is concerned with the latter area. In most technical combustors (cold) oxygen from air is the oxidizer reacting with the fuel to form products such as carbon dioxide and water.…”