Continuous Online Oil Consumption Measurement with the SO ₂ Tracer Method 2011-01-2404

Environmental issues have a significant influence on the development of modern combustion engines. Particularly the tightening of emission limits in Europe and the USA have to be considered in the development process. One issue that influences the emissions of engines is the oil consumption of the engine and thus the reduction of the oil consumption of combustion engines has gained importance in recent years. In order to optimize the oil consumption of the engine a measurement technique is needed that allows a very accurate detection of the engine oil consumption for steady state as well as for transient engine operation points. Since conventional measurement techniques provide only limited accuracy at long measuring times and are only applicable for steady state engine operation new methods for the online detection of the engine oil consumption have to be established. New methods for the oil consumption measurement are the tracer methods. Here, a tracer substance in the oil is used that can be detected in the exhaust gas. The actual oil consumption of the engine can then be calculated with the measured concentration of the tracer substance. One of the tracer methods is the SO2 tracer method. For this method sulfur is used as tracer in the engine oil. The oil consumption is calculated with the occurring sulfur dioxide (SO₂) in the exhaust gas.

The aim of this study was the implementation of the SO₂ tracer method at the Combustion Engines and Emission Control Laboratory at the University of Applied Sciences Regensburg. The detection of the SO₂ concentration in the exhaust gas was done by means of an IMR mass spectrometer. For the implementation and validation of the measurement setup was done by comparing the achieved results of the SO₂ tracer method to gravimetric oil consumption measurement results. For this purpose measurements with steady state and transient engine operation were carried out with the parallel measurement of the engines oil consumption with both techniques. Thereby the main focus was on low engine operation points because there low oil consumption rates are supposed to occur and thus the oil consumption measurement is most challenging there. Besides the validation of the measurement setup the influence of the engine operation mode and cylinder modifications was investigated. Therefore measurements with steady state and transient engine operation as well as single cylinder measurements on cylinders, on which special modifications had been applied, were carried out using the SO₂ tracer method for calculation the oil consumption.