Building a mathematical model of the destruction of a connecting rod-piston group in the car engine at hydraulic lock

Abstract

This paper investigates the process of destruction of parts of the connecting rod-piston group of the engine due to hydraulic lock after the ingress of liquid into the cylinders of the engine. Comparing expert data on actual engine destruction due to hydrolock with existing estimation models has made it possible to identify a number of significant contradictions affecting the objectivity and accuracy of the destruction assessment. To resolve the existing contradictions, a mathematical model for reconstructing the destruction of the connecting rod-piston group of the engine during a hydraulic lock has been improved. Unlike the existing ones, the model makes it possible to take into consideration not only the static deformation of the connecting rod but also to give a comprehensive assessment of the deformations of the connecting rod, piston pin, and piston at different volumes of hydrolock fluid. Underlying the model is the hypothesis assuming that the deformation of the piston pin under excessive load caused by hydraulic lock leads to the emergence of tension and an increase in the friction in the mated pin-piston. The calculation from the condition of differential change in the amount of friction in the mated pin-piston produced a satisfactory result that does not contradict the practical data and has confirmed the working hypothesis. By calculation, the onset of the destruction of engine parts during hydrolock at a pressure in the cylinder close to 17.3 MPa, at a crankshaft angle of about 346°, was revealed. In addition, it was found that in the case of violating the operating conditions, due to friction, the mated pin-piston is exposed to the lateral force on the skirt that reaches 17.2 MPa, which exceeds the permissible one, calculated according to known procedures, by 2.8 times. The results reported here are confirmed by known practical data, which makes the devised model applicable to the practice of expert studies into the causes of engine malfunctions when violating the operating conditions of a car

Method for expert evaluation of the technical con-dition of the cylinder-piston group of automotive engines after hydrolock

“…Однак, кількісні оцінки та, тим більше перевірки тих чи інших даних, пов'язаних з величиною компресії, надзвичайно затратні, оскільки вимагають експериментальних досліджень великого обсягу та складності. Крім цього, у відомих джерелах немає жодних рекомендацій щодо діагностики гідроудару та деформації шатуна при попаданні рідини в циліндр [19], зокрема, за допомогою вимірювання компресії. Звідси виникає потреба у розрахункових моделях процесу вимірювання компресії та їх теоретичному обґрунтуванні.…”

Determination of gas parameters in resonant pipes and channels of engines with a periodic workflow using the piston analogy method

“…Due to the averaging of instantaneous parameters, such models provide little detail of the processes, and some parameters can only be obtained experimentally. However, the use of 0-dimensional models can be very effective not only for preliminary research and creating the appearance of a prototype; with their help, it is also possible to study various types of engines or devices that have a volume or cylinder with an unsteady working process [10,11].…”