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This paper proposes a simple analytical method for determining the viscosity index (VI) that effectively aligns with results obtained from the applicable standards. This method simply needs the kinematic viscosity of the tested oil at 40 and 100 °C as input parameters and does not need to use tables that are an integral part of the mentioned standards. This work presents a method and evaluates the accuracy of determining auxiliary parameters in the form of kinematic viscosity values at 40 °C for two hypothetical oils. These oils have a kinematic viscosity at 100 °C equal to that of the oil under testing and have VI = 0 and 100. The relative fitting error percentage and the coefficient of determination are found for the specified auxiliary indicators. The method is validated using data obtained from previous studies in the form of the kinematic viscosity of lubricating oil–diesel mixtures. The mixtures of viscosity grades SAE 30 and SAE 40 lubricating oil with diesel oil at concentrations of 0, 1, 2, 5, 10, 20, and 50% w/w are tested. The viscosity index for each mixture is determined using a standard-based manual calculation using the Anton Paar viscosity index calculator and the proposed method. The results obtained from the proposed analytical method are compared with those from two other methods. The maximum percentage relative fitting error (δmax ≈ 1%) and the coefficient of determination (R2 > 0.999) are determined. The obtained results demonstrate a very good fit and, thus, confirm the usefulness of the proposed approach.

This article presents the verification of the hypothesis on using certain approximation curves in the evaluation of used lubricating oil. These curves are plotted for fresh lubricating oil to approximate the parameters of lubricating oil diluted with diesel oil. To confirm the hypothesis, an experiment is conducted to determine the flash point, initial boiling point, density at 15 °C, kinematic viscosity at 40 °C and 100 °C, and viscosity index. The analysis covers fresh oil and used SAE 30 grade Marinol CB-30 RG1230 oil taken from the circulating lubrication system of a supercharged, trunk-piston, 4-stroke ZUT Zgoda Sulzer 5 BAH 22 engine that is located in the Marine Power Plant Laboratory of the Maritime University of Szczecin. Undiluted lubricating oils (both fresh and used) and mixtures of lubricating oils with diesel oil are examined for diesel oil concentrations in the mixture equal to 1, 2, 5, 10, 15, and 20% m/m. Orlen Efecta Diesel Biodiesel is used to prepare the mixtures. The functions approximating the parameters for fresh oil are determined and adapted to describe the variation of the same parameters for the used lubricating oil. For each case, the coefficient of determination, the maximum relative error of the model fitting to the experimental results, and the root mean square error (RMSE) are determined. In the experiment, the variation in the parameters of the used lubricating oil remained the same as for fresh oil parameters. Thus, the research hypothesis is confirmed.

This article presents the results of research on the impact of changing the cross-section of an atomizer’s flow channel, which is caused by changing the flow geometry of the passive part of the needle on the drop diameter distribution of the fuel spray. A three-hole type H1LMK, 148/1 atomizer with hole diameters, dN, equal to 0.34 mm, is analyzed. A nozzle with a standard (i.e., unmodified) needle and three nozzles using needles with a modified profile in the flow part of the needle, marked by the code signatures 1L, 2L, and 3L, are tested. An increasing level of fuel turbulence characterizes the needles during the flow along their flow part due to the use of one (1L), two (2L), and three (3L) de Laval toroidal nozzles, respectively, obtained by mechanically shaping the outer surface of the flow part of the spray needle. The spray produced is tested using the Malvern Spraytec STP 500 device cooperating with the dedicated Malvern version 4.0. During the tests, measurements and an analysis of the spray droplet size distribution over the entire injection duration, equal to 7 ± 2 ms, are made for each nozzle. The experiment makes it possible to determine the effect of the nozzle needles’ profiles on the time distribution of the actual droplet diameters; the time distribution of the Sauter mean droplet diameters, D[3,2]; the percentile shares of the droplet diameters Dv (10), Dv (50), and Dv (90); the distribution span during the development of the spray stream; and the time distribution of the shares of the droplets with diameters belonging to selected diameter classes D[x1−x2] in the spray. The results of the measurements of the drop diameter distribution indicate that using atomizers with a modification to the flow channel allows for an increase in the share of droplets with smaller diameters compared to the standard atomizer.

This article proposes using the Arrhenius model for estimating the viscosity of a mixture of two liquids in the quantitative assessment of the physicochemical properties of lubricating oils in the context of assessing the level of dilution of lubricating oil with diesel oil. Dynamic are made of mixtures of lubricating oil and diesel oil with known concentrations of 0, 1, 2, 5, 10, 20, 50, and 100% m/m of the diesel oil content in the mixture. Mixtures of the most popular oils (viscosity classes SAE 30 and SAE 40) with diesel oil that meet the requirements of the DMX of the marine distillate fuels category are prepared and tested. Viscosity measurements are performed at 40, 50, 60, 70, 80, 90, and 100 °C temperatures. The Arrhenius model is used to estimate the viscosity of the mixtures with an assumed diesel oil content and to estimate the diesel oil concentration in the mixtures with a known measured viscosity value. In both cases, the absolute estimation error is determined, and the accuracy of the estimation is assessed against the known concentration of diesel oil in the mixture with lubricating oil and the temperature at which the viscosity is measured. The estimated concentrations of diesel oil in mixtures with lubricating oil are useful to assess the condition of the lubricating oil (for concentrations of diesel oil lower than 5% m/m). The method is proposed to be used in practice to support standard laboratory oil analysis.

The rheological, ignition, and tribological properties of lubricating oils diluted with biodiesel were analyzed. The flash point tFP, calculated cetane index CCI, density ρ, coefficient of the temperature density change ε, kinematic viscosity ν, dynamic viscosity η, viscosity index VI, and lubricity during a High-Frequency Reciprocating Rig (HFFR) test (x, y, WSD, and WS1.4) and lubricating conditions during an HFFR test (oil film resistance FILM and friction coefficient μ) were determined. The test was performed for the oil mixtures of the lubricating oil of the SAE 30 and SAE 40 viscosity grades, which were diluted with the biodiesel blend (D93B7—diesel oil with 7% v/v fatty acid methyl esters, FAME) at concentrations of diesel oil in the mixture equal to 0% (pure lubricating oil), 1%, 2%, 5%, 10%, 20%, 30%, 50%, and 75% m/m, respectively. The experiment confirmed the existence of clear relationships between the increase in the dilution of lubricating oil with tested biodiesel blend and tFP, ρ, ε, ν, η, and VI, and the deterioration of lubrication conditions. It is recommended to take remedial action even in the case of low diesel oil concentration (tFP, ν, and η changes. Simultaneously, the tests showed no significant effect on the lubricity and the CCI. The critical contamination of oil with fuel in the range of 2–5% by weight, as indicated in the literature, still allowed for a certain “safety margin” regarding these parameters. However, when the concentration of diesel fuel in the lubricating oil exceeded 5–8% m/m, the deterioration of the lubrication was expressed by a decrease in FILM and an increase in μ was observed; hence, such a contamination should be considered excessive. When the concentration of diesel fuel exceeds 10% by weight, there is a serious risk of engine damage during operation.

This article presents research results on mechanically generated oil mists. The research was carried out for oil mixtures for the Agip/Eni Cladium 120 SAE 40 API CF oil for industrial and marine engines diluted with diesel oil Orlen Efecta Diesel Bio at diesel oil concentrations of 2%, 5%, 10%, 20%, and 50% m/m. Pure lubricating oil and pure diesel oil were also tested. Droplet size distributions were determined for the reference moment at which residual discrepancies R between the measurement data and the sprayed pure diesel oil calculation model obtained the lowest value. For mechanically generated oil mists, the light transmission coefficient through the oil mist T, the specific surface area of the oil mist SSA, and the volumetric share of drops DV(V%) for 10%, 50%, and 90% of the total volume of the generated oil mist were determined. The span of the volumetric distributions of droplet sizes SPAN, Sauter mean diameter D[3,2], De Brouckere mean diameter D[4,3], the volumetric and mass percentage of droplets with diameters ≤5 μm (diameters necessary for a crankcase explosion), the minimum difference between the measurement results, and the calculation model used by the residual error measuring device were determined. The best fit in each measurement cycle (the smallest R value was analyzed. For specific indicators, correlations with diesel oil levels in the mixture were determined using the Pearson rXY linear correlation coefficient. Those results confirmed an increase in smaller-diameter droplets, an increase in the number of droplets with diameters up to 5 μm, and an increase in the span of the oil mist droplet diameter distribution with additional diesel oil. This confirmed a relationship between an increased lubricating oil dilution and an increased explosion risk in the crankcase.

Fuel contamination of engine lubricating oil has been previously determined to arise from two independent phenomena: the effect on oil flash point, and the effect of changing lubrication conditions on tribological pairs. This paper combines these effects and holistically analyzes the consequences of fuel in the lubricating oil of a trunk piston engine on the risk of crankcase explosion. The author hypothesized that diesel fuel as an oil contaminant increases the risk of an explosion in the crankcase of an engine due to the independent interaction of two factors: (1) changes in the oil’s combustible properties, and (2) deterioration of the lubrication conditions of the engine’s tribological nodes, such as main bearings, piston pins, or crank bearings. An experiment was performed to evaluate the rheological, ignition, and lubrication properties of two oils (SAE 30 and SAE 40) commonly used for the recirculation lubrication of marine trunk piston engines for different levels of diesel contamination. The hypothesis was partially confirmed, and the results show that contamination of the lubricating oil with diesel fuel in an amount of no more than 10% does not significantly affect the risk of explosion in the crankcase. However, diesel concentrations above 10% call for corrective action because the viscosity index, lubricity, coefficient of friction and oil film resistance change significantly. Deterioration of the tribological conditions of the engine bearings, as seen in the change in viscosity, viscosity index, and lubricity of the oil, causes an increase in bearing temperature and the possibility of hot spots leading to crankcase explosion.

This article provides a brief introduction to the indicators of the volatility and flammability of lubricating oils and fuels. It is proposed that the initial boiling point be used as an indicator of the contamination of lubricating oil with distillate fuel (i.e., diesel biofuel oil) in the context of the rapid detection of explosion risks in the crankcase. Detailed tests were carried out on lubricating oil samples (SAE 30 and SAE 40 grades, which are most commonly used in the lubrication systems of marine trunk engines) diluted with diesel oil at selected mass concentrations (0, 1, 2, 5, 10, 20, 50, and 100%). The oils were tested to determine their relevant properties: the flash point temperature and the initial boiling temperature. The flash point was determined in a closed crucible using the Pensky–Martens method, which is in accordance with PN-EN ISO 2719. The differences between the initial boiling point and the flash point of the tested lubricating oils were determined for different dilution levels of lubricating oil in diesel fuel. An approximate method for the calculation of the flash point of the oil based on the initial boiling point is proposed. The results of oil flash point measurements are compared with values calculated as a function of the boiling point for both lubricating oils tested. An evaluation of how well models fit the experimental results is reported. Conclusions are presented on the applicability of the proposed method during operational practice.

This article suggested broadening the standard methods for diagnosing the technical condition of diesel engines to include an analysis of the instantaneous rotational speed of compression combustion engines with the use of a novel algorithm. The authors revised the subject concerning the use of the analysis of instantaneous changes in the rotational speed of an engine when assessing its technical condition and the location of the malfunction. An algorithm and its practical implementation in a prototype diagnostic system called SpeedMA were presented. This article reported the test results of the prototype in the context of indicating the engine cylinder in which ignition failed to occur. Tests were carried out for two marine engines: a low-speed trunk engine directly driving the fixed-pitch propeller and a medium-speed trunk engine driving the alternator. For each case, an analysis was carried out for different engine loads and at individual cylinders in which combustion failed to occur. The experimental results showed an unambiguous relation between the combustion process of the examined engines and changes in the instantaneous rotational speed. The results also confirmed the usefulness of the proposed method and showed the correct operation of the presented diagnostic algorithm. The proposed diagnostic system could be used during the operation of engines running in real ship engine rooms.

The article suggests and supports a simulation-based methodology for determining whether the dynamic strength of tire inflation restraining devices for tire inflation meet quality requirements and ensure operator safety during a potential tire explosion. Dynamic strength tests using an NM-600 safety shield and NK-0728 safety cage during a 29.5 R25X tire explosion at a pressure of 10 bar were presented as an example application of this methodology. The shield was subjected to destructive tests involving the use of a 2200 kg impactor, dropping it so that the minimum kinetic energy reached 20 kJ at the time of impact. Analyzed devices were constructed of S355 steel in accordance with EN 10025. The Cowper−Symonds model of material for strain rate phenomena was used in the calculations. Simulations of a 20 kJ ring impact against the cage were performed. The equivalent stress distribution was determined, and displacement contour lines for the maximum dynamic deformation value and plastic deformation were calculated. The plastic displacement obtained in numerical tests was equal to the permanent deformation recorded in the experimental test. Further, the simulations showed that the examined cage met the assumed strength criteria. The conducted tests confirmed the usefulness of the proposed methodology for assessing the dynamic strength of safety cages and shields for tire inflation. The full-scale, physical cage testing is difficult to implement because it requires placing a ring impacting the cage wall. This is a major boundary for closed cages, as considered in this publication. Thus, simulation-based methods are becoming a principal tool for safety assessment of tire inflation restraining devices.

Tyre replacement and inflation is a common occurrence in the transportation, construction and mining industries, but in commercial, off-highway, or earth-moving vehicles, the rupture of an inflated tyre can cause serious or even fatal injuries to an operator. This paper highlights the consequences of a burst tyre based on a real case. The presented analytical approach is based upon an assumed adiabatic process and continuum mechanics using Bernoulli’s flow equations. A numerical analysis of a tyre burst was performed using multibody and finite element methods to reconstruct the fatal accident. It was shown that tyre-blast injuries may lead to lethal head trauma and bodily injuries, since the potential energy stored in large, over-pressured tyres can exceed 1 MJ.