Marek J. Głogowski

Correlation between electrical, mechanical and chemical properties of fresh and used aircraft engine oils

In this paper the results are presented of measurements of electrical, mechanical and chemical properties of fresh and used aircraft engine oils. Oils were used in a four-stroke aircraft engine and their samples were taken after the 50-hour work of the engine. The resistivity, permittivity and viscosity of oils were measured as a function of temperature. Additionally, some measurements of the absorbance spectra and size of particles contained in the oils were carried out. The significant reduction in the resistivity of the used Total oil was observed. The relative permittivity of both used oils was slightly increased. The oils relative viscosity depends on temperature of oil and given time that elapsed from the very first moment when the shear force was applied in a rheometer. The results obtained allowed one to identify more precisely the chemical and physico-chemical interactions occurring in the tested samples, as compared with a typical infrared spectroscopy.

Electrostatic and tribological phenomena and their effect on the braking torque in the shaft-oil-lip seal system

The former research [1] was carried out on the influence of tribocharging in a system: metal rotating shaft-oil-lip seal on its work, especially on changes in the shaft braking torque with the increasing angular shaft velocity and oil temperature. The results obtained suggested that there be a possibility of reducing the braking torque by an external electric field. The compensation for the electric field generated in the system by natural tribocharging was proposed. The reduction in the braking torque seemed possible while applying an external DC electric field to the system. In general, the torque tended to increase with the increasing DC electric field for a variety of the oils and lip seals used and for different shaft angular velocities (rotational speeds) and oil temperatures. The braking torque reduction was achieved only for one lip seal and some different oils, which was and is a promising, expected result. The research results were yet presented elsewhere [1–3] and here some novel attempt has been made to interpret the results obtained in their physical—tribological and especially electrostatic—aspects since there has been a lack of such an interpretation in the literature of the subject.

Anti-wear additive content in fully synthetic PAO and PAG base oils and its effect on electrostatic and tribological phenomena in a rotating shaft-oil-lip seal system

The paper presents the results of experiments on electrostatic and tribological aspects of different anti-wear additives contents when an additive is blended with different fully synthetic (poly-α-olefin) and PAG (polyalkylene glycol) base oils in a rotating shaft–oil and oil–lip seal interfacial system. The experimental results are the relationships of electric potential induced in a lip seals stiffening ring to angular velocity of a rotating metal shaft and to temperature of the oils tested. The braking torque of a shaft is measured with a torquemeter sensor connected directly with a microprocessor-based system for controlling the rotational speed and for measuring the shafts braking torque and oil temperature. The beneficial and promising results are obtained for PAG when an external DC electric field is applied to the system and the braking torque is then reduced for a certain combination of the base oil and additives contents. On the basis of the former and present research results an analysis is made to permit one to show how the type of the oils and additives tested can affect both interfaces: rotating shaft–oil and oil–lip of the lip seal and especially the braking torque.

Additives contents in PAG and synthetic motor base oils and their effect on electrostatic phenomena in a rotating shaft-oil-lip seal system

The paper presents the results of experiments on the electrostatic aspects of anti-wear (AW) and friction modifier (FM) additives (agents) when these are added to PAG (polyalkylene glycol) and PAO 6 (synthetic) motor base oils to obtain their blends. Experiments are carried out in a rotating shaft-oil-lip seal system (a friction junction) which is a specially built experimental facility to be the simplified model of an engine crankcase in the interior of which an earthed metal shaft rotates at given angular velocities from 500 up to 1000 rpm. The AW and FM additives contents in blends are 0.1 and 0.5 wt%. Oil temperature is controlled electronically and changed from 60 up to 110°C. An 88-mm diameter lip seal is used in the experiments. Electric potential of a stiffening ring of the lip seal tested is measured directly with an electrometer. The experimental results are the relationships of the potential induced in a stiffening ring to shafts angular velocity and to the temperature of pure base oils and their blends with AW and FM agents.

Effects of engine base oil type and ZDDP on the electrical double layer in the rotating shaft-oil-lip seal system with and without an external DC electric field

The paper presents the results of experiments on tribo-charging of a blend of mineral base oil and different zinc dialkylditophosphate (ZDDP) contents. Experiments were carried out on the specially built experimental facility to be a simplified model of an engine crankcase in whose interior an earthed metal shaft rotated at given angular velocities. The potential of a stiffening ring of a lip seal was measured directly with an electrometer. The experimental results are presented in the form of some characteristics that are relationships of the potential induced on the stiffening ring to the oil temperature for different angular shaft velocities and the ZDDP contents. Also the effects of an external DC electric field on the braking torque of the steel shaft were examined for a range of oil temperatures, angular velocities, and ZDDP contents. An analysis of the research results obtained permitted one to show how the ZDDP content in a blend with the base oil tested, angular velocity, and oil temperature could affect charging in the interface system: rotating shaft-oil and oil-lip seal, as well as the whole oil film in between and both electrical double layers (EDL) at the surfaces of the shaft and of the lip of a lip seal.