On line engine oil consumption monitoring via the gaseous total sulfur signal SO2 in the raw exhaust of the engine utilizing the sensitive ion molecule reaction mass spectrometry

Abstract

The dynamic monitoring of oil consumption in IC engines is approached with various techniques ranging from radioactive counting to detection of halogenated tracer compounds or polyaromatic hydrocarbon tracers, to monitoring unburned hydrocarbons as residues from engine oil. This article discusses the method of gaseous SO2 measurement in raw exhaust its benefits and limitations of todays status. Modern engines consume about 2 to 5 g/h of engine oil under low and medium load but consumption may go up to 130 g/h in negative load conditions. Particulate filters must be desulfated every 5000 km even when sulfur free fuel is in use. For the oil measurement in the raw exhaust all possible Sulfur compounds are converted to SO2 in a hot oxidizing atmosphere. Additional pure oxygen in the form of ozone is added to the oxidizer for very low lambda engine conditions and the conversion of sulfur on particulates into SO2. A sensitive mass spectrometer operating in an ion molecule ionization mode measures gaseous SO2 from concentrations of 0.02 ppm to 50 ppm in measurement cycles from 2 Hz to 0.2 Hz depending on if long term measurement or dynamic operation is chosen. Technical description of pressure reduction, gas transfer, oxidation efficiencies and lower detection levels of the instrumentation are given as well as data on a complete engine map and data on reproducibility of the SO2 method are presented.