Calculation of mass emissions, oxygen mass fraction and… gas exchange in the lungs occurs in the

New computational procedures are proposed for experimentally evaluating air–fuel ratio and mass fractions of exhaust emissions as well as EGR rate, oxygen mass fraction and thermal capacity of the inducted charge in IC engines running with diesel oil, gasoline or any alternative liquid or gaseous fuel, such as LPG or CNG. Starting from the chemical reaction of fuel with air, from gaseous and smoke level measurements in the raw gases, the procedures calculate the volume fractions of oxygen in the combustion air and of compounds in the exhaust gases, including those that are not usually measured, such as water, nitrogen and hydrogen. The methods also take the effects of various fuel and combustion air compositions into account, as well as to the presence of water vapor, CO2, Ar and He in the combustion air.The algorithms are applied to four different automotive engines under wide ranges of steady-state operating conditions: three turbocharged diesel engines featuring high-pressure cooled EGR systems, and an SI naturally aspirated bi-fuel engine running on either gasoline or CNG. The computed air–fuel ratios are compared to those obtained from directly measured air and fuel mass-flow rates as well as from more conventional UEGO sensor data. The mass emissions are worked out in terms of both brake specific mass emissions and emission indexes of each pollutant species, and the results are compared to those obtained by applying SAE and ISO recommended practices. The computed oxygen mass fraction of the inducted charge was then compared to that derived from direct measurement of O2 concentration in inlet manifold. Finally, the sensitivity of results to the main engine working parameters, the influence of environmental conditions (in particular the effect of air humidity on NOx formation) and the experimental uncertainties are determined.

…  " The basic principles of the technique are relatively straightforward and the probes are difficult to damage if reasonable care is taken. " [33]  Low airflow restrictions  Low sensitivity to mounting location and orientation  No moving parts so less risk  Relatively inexpensive compared to alternatives  Measurements independent of the air density [34] Disadvantages  Very sensitive to contamination by dust, smoke, and oil vapour particles in air flow, varying with operation time o " it is advisable to calibrate the gauge prior to and after measurements and to filter thoroughly the air in the volume being investigated so that no particles larger than 0.2D in size are found in the flow. " [36]  Installation requires a laminar flow across the hot-wire  Can be fragile sensors  Only abe to measure magnitude, not direction unless multiple sensors used but the spatial resolution of this method is relatively poor [37]  Heat transfer occurs between the heating element and the cylinder walls that must be compensated for, normally using a variation of King’s law [37]  To optimise the frequency response, the sensor needs minimal thermal inertia [37]  Frequency distortion is also common when the sensor starts to fail [38] …