Online Oil Dilution Measurement

Background

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As a result of the renewable energy directive 2009/28/EC the EU member states are required to raise the amount of renewables in the total final energy consumption to a mean 20 % until 2020. This directly affects the development of internal combustion engines.

Dilution of the engine oil by ethanol-containing fuels e.g. Super E10 and diesel fuels containing biodiesel e.g. B7 can significantly alter the lubricating properties and in turn cause engine damage. Due to ethanol having a higher enthalpy of evaporation and a lower vapor pressure fuels with higher ethanol contents tend to yield unfavorable mixtures compared to conventional gasoline especially during the cold start and warm-up phases of the engine. Thus, fuel ingress into the oil in these engine states becomes very likely. For diesel engines the post-injection states initiating DPF (Diesel Particulate Filter) regeneration are of particular interest. Though the chemical and physical properties of biodiesel and diesel components are similar biodiesel fuels also lean towards diluting the engine oil during DPF regeneration.

Other aspects in current combustion engine development such as applying new combustion methods and catalyst heating equally facilitate oil dilution - even when using standard gasoline. Finding strategies to counter or optimize dilution of the engine lubricants requires proper understanding of the oil ingress and egress mechanisms themselves. Therefore measurement instrumentation is needed that can determine the amount of fuel in engine oil and can preferably yield results in real time.

Solution

The V&F Online Oil Dilution Measurement System comprising the LubeSense and the LubeSampler provides automotive engineers with the opportunity to continuously determine the oil dilution. The LubeSampler consists of a separate oil circuit connected to the oil sump of the engine. A circulating pump causes good mixing of the oil. The small sample is taken by a dosage pump set to 1.0 ml/min. Via a connected dosage valve and driven by purge gas the sample is introduced into the thermo desorber where the oil is stripped of the characteristic volatile components resulting from the fuel diluting the oil. These volatile compounds depend on the fuel that is used. They are ethanol for ethanol-containing fuels, benzene, toluene and xylene for gasoline or hydrocarbons such as C4H10 for diesel B7.

The V&F LubeSense with its patented IMR-technology (Ion Molecule Reaction) is able to determine all these components down to the low ppb level in order to achieve detection limits of the oil dilution below 0.1 % fuel in oil. To calibrate the system mixtures with known contents of fuel in oil are prepared and following thermal desorption the signals of the marker components such as ethanol are quantified. Hence, signals of the sample with unknown concentrations of fuel in oil can be correlated.

Advantage

In contrast to conventional offline methods, the V&F LubeSense and LubeSampler yield real time results. Time profiles of the oil dilution mechanism for stationary and dynamic engine test cycles are displayed directly granting the engineer the possibility to develop strategies to minimize the dilution of engine oil by fuel. The LubeSense mass spectrometer with its IMR-technology - as opposed to FID determination of a sum HC signal – is cable of detecting the compounds desorbed from the oil selectively allowing detailed studies not only of time profiles but also of the chemistry involved in the oil dilution process.

Highlights

  • Real time oil dilution measurement
  • For diesel and gasoline engines
  • Direct sampling

Applicable instruments

AirSense
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