Abstract
This paper presents changes in the tightness of a combustion chamber during a 1200-hour bench durability test. The study was conducted on three four-cylinder turbocharged DI diesel engines with a capacity of 1.3 dm3. The changes in the tightness were determined on the basis of the results ofperiodical measurements of the blow-by flow rate under different conditions of engine operation and measurements of maximum compression pressure in the cylinders. The results showed that the maximum compression pressure remained at the same level during a long period of engine operation, corresponding to a distance of150 000 km covered by a car. After that period, the pressure started to decrease (after a distanceof200 000 km, it had dropped by 10 %). The blow-by flowrate decreased in the initial period of engine operation and then it started to rise linearly atfull engine load. The rate of increase depended on engine speed - it was the smallest at low speeds (20 % increase in the time range of100-1200 hours, which corresponded to a distance of16 000-192 000 km covered by a car - at 1000 rpm), and the highest at 4000 rpm (an increase of 70% in the same time range).
Highlights
The tightness of the combustion chamber is an important characteristic which determines the technical condition of an internal combustion engine
Znajomość szybkości zmian szczelności w funkcji czasu pracy silnika pozwoli na ocenę poprawności wyników uzyskiwanych w symulacyjnych badaniach zmian szczelności komory spalania z wykorzystaniem analitycznego modelu uszczelnienia pierścieniowego [2, 3, 8]. 2
We analysed the results of measurements of the blow-by flow rate at full and low engine loads and of maximum compression pressure performed periodically on three engines during a prolonged durability bench test
Summary
The tightness of the combustion chamber is an important characteristic which determines the technical condition of an internal combustion engine. Tightness deteriorates mainly due to wear on the pistonrings-cylinder assembly, as well as to the valves and valve seats. The decrease in tightness affects engine performance, fuel and oil consumption, and toxic emissions. In the case of diesel engines, decreased tightness impairs the start-up performance of a cold engine [1, 6, 7]. Engine constructors endeavour to maintain – despite the inevitable wear of components – the tightness of the combustion chamber at the highest level for a long period of an engine’s life. Deterioration of the above parameters, resulting from the decrease in the tightness of the combustion chamber, is often the reason for deeming an engine to be defective and withdrawing it from operation [4, 7]
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