Wybrane kierunki działań tribologii w silniku spalinowym.

W opracowaniu przedstawiono wybrane kierunki działań tribologii w silnikach spalinowych. Punktem wyjścia do ich określenia jest analiza sprawności silnika spalinowego. Drogą poprawy sprawności mechanicznej jest komponowanie nowych materiałów, które współpracują w obecności olei smarujących o stabilnych własnościach temperaturowych. Autor pracy opracował uszczelniający pierścień tłokowy, którego boczna powierzchnia jest pokryta powłoką z azotku tytanu. Współpraca tak powstałego pierścienia z tuleją cylindrową pozwala wydatnie obniżyć straty tarcia w węźle pierścień tłokowy-tuleja cylindrowa-tłok. Nowe materiały muszą pracować w obecności nowych olei smarujących, przejmujących w znacznym stopniu funkcję chłodzącą. To kolejny z kierunków prac tribologii w silniku spalinowym i jednocześnie możliwość podniesienia jego sprawności. W opracowaniu przedstawiono, oprócz możliwych do realizacji zmian w układzie korbowym silnika, również zmiany w układach zasilania zarówno silników o zapłonie samoczynnym, jak i silników o zapłonie iskrowym.

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In the papers presented are selected activity directions (activities) of tribology of combustion engines. Starting point to specify them is analysis of the combustion engine's efficiency. Engine's efficiency depends on of assumed thermal cycle (Otto, Diesel, Sabathe), real behavior of the combustion process and mechanical efficiency. Based on current knowledge the efficiency of a combustion engine can reach approx. 0,55 but assuming mechanical efficiency equals to 1. The way to enhance mechanical efficiency is composing new materials, which work in presence of oils of stable temperature properties. The author has developed the piston ring which face is covered with Titanium Nitrid layer. Cooperation of such ring with the cylinder sleeve (liner) allows for great reduction in friction of piston ring-liner-piston assembly. This assembly shows around 50 per cent of overall friction loss of combustion engine. The new face of the piston ring forces developing of new materials for the cylinder sleeves. Presented are developed for new range of Daimler-Chrysler engines cylinder barrels made of aluminium alloy. Received material (aluminium alloy) is plastic, highly small-grain, shows (according to the authors) negligible wear on the engine. The new materials need to work with presence of new oils, taking over also the cooling function. This is the next direction in research of tribology of combustion engine and simultaneously a way to increase its efficiency. Allowing for higher operating temperatures of piston ring, especially in the TDC of the fire ring, can leads to mentioned above increase in thermal efficiency which results in better fulfilling of the theoretical thermal cycle realized in real cycle of the combustion engine. This article presents besides feasible changes in the piston-piston ring-cylinder system also changes in the supply system of high-pressure and petrol engines. In the high-pressure engines used are currently high pressure (135/200 MPa) injection supply system. Simultaneously available are fuels with reduced to the minimum sulphur contents. At such high injection pressure and low sulphur contents can appear problems with lubricating in injectors and injector pumps of the supply systems. In the petrol engines two companies (Mitsubishi and PSA) have released engines with direct injections of fuel into the combustion chamber. Injection's pressure equals 60 MPa. Lead free petrol shows low lubricating properties and hence can appear tribological problems. The main fields of interest of tribological research related to combustion engines are summarized in following groups: - developing of modern base of synthetic oil resistant to higher operating temperatures of engine components, particularly piston ring and cylinder sleeve, - applying of ceramic composites in form of antiwear coatings and developing new tribological pair working with them in presence of synthetic oils, - developing new concepts of engines working without lubricating and cooling systems, - other works leading to complete eliminating of sulpur from the diesel fuels.