kinematic times dynamic viscosity meaning

Yet, it is an expensive and logistically complex undertaking, requiring a relatively large sample size and a team of qualified analysts. A viscosity assessment usually involves conducting tests in specialized research laboratories that have appropriate equipment. Therefore, fresh oil control is important to obtain a reference value for proper viscosity monitoring. It is, however, worth noting that the viscosity of fresh oil, as given in the standards, may differ from its nominal value by up to 20%, while a change in viscosity of 10% during the operation may often be considered critical. The monitoring of oil viscosity consists in determining the changes in viscosity during the operation compared to the viscosity of fresh oil, i.e., the starting value corresponds to the viscosity of the fresh oil, while the critical values for the decrease and increase in viscosity are established.

Viscosity measurements are important in many industries, as they are a very fast, accurate, and very reliable way to analyze important factors affecting the machine performance. Where C is the viscometer calibration constant, mm 2/s, and t is the arithmetic mean of the outflow time, s. Determination of viscosity by capillary method is based on Poiseuille’s law and expressed as Determining the kinematic viscosity is based on measuring the flow of the tested liquid through a channel with a given geometry using a device called a capillary viscometer. Kinematic viscosity is a measure of the resistance to flow of a fluid under the influence of gravity. In terms of viscosity measurements, the following methods are also used: sensing body displacement, acoustic, and vibrational methods. They use different measurement principles depending on the parameter to be monitored, e.g., optical properties (light scattering) or electrical properties (transmittance and conductivity). The sensors are directly installed in the vehicle to constantly monitor the condition of oil. In recent years, the demand for online oil measurement and data management has been increasing. The assessment of oil viscosity makes it possible to select an appropriate interval between subsequent oil changes, which has a significant impact on the operating and maintenance costs (operation and maintenance). Therefore, a regular replacement of oil forms an essential part of a car maintenance program. An increase in kinematic viscosity is associated with oxidation processes at elevated temperatures and a decrease with oil shear or dilution with unburnt fuel. Viscosity values may increase or decrease during operation. In fact, in the automotive industry, monitoring the viscosity of lubricants is considered a principal indicator of oil quality. It is then particularly important to monitor the properties of oil especially, as its degradation can eventually lead to engine damage or failure. High temperature solid impurities (such as soot, coke, products of tribological wear of the engine, corrosion products, etc.) and the external ones (moisture, air dust, air, and other gases), as well as shear, oxidation, and nitration processes are some of the key factors contributing to the degradation of engine oil. The study fills an important gap in empirical research in the context of the reliability of measurement results obtained using various research techniques.Įngine oil ensures smooth engine operation through its lubricating and cooling effects yet, with time and use, it becomes subject to degradation processes. Therefore, a very careful approach is suggested when choosing these instruments. It was also found that the results obtained with the use of the mid-FTIR spectrophotometer were burdened with a very large measurement error. Consistent outcomes were obtained for the Stabinger viscometer only, whereas the microchannel viscometer and the mid-FTIR spectrophotometer were not as precise as the reference method. The main data analysis tools used in the study were multiple regression, Mahala Nobis distance, post-hoc analysis, and the Wilcoxon signed-rank test with the Bonferroni correction. The study material comprised 42 fresh engine oils, all of which are commercially available. The following instruments were selected to measure: a mid-FTIR spectrophotometer, a microchannel viscometer, and a Stabinger viscometer. The aim of this paper is to compare the results of kinematic viscosity of lubricating oils measurements at 40 ☌, obtained with three different rapid evaluation devices, and the standardized method using an Ubbelohde Capillary viscometer.

Kinematic times dynamic viscosity meaning