Search Results

In a Diesel engine, temperature reduction on a power cylinder unit (PCU) is an important demand due to increasingly engine load and performance of modern engines. Both piston and piston ring pack need to be prepared to attend this demand. In general, Diesel engine pistons use cooling galleries to remove heat from high temperature regions and, therefore, reduce tensions on piston combustion bowl and bowl rim. Piston concept gallery was designed to improve piston performance: it consists on more efficient heat dissipation through an elevation of the gallery and new shape. The elevated piston promoted a temperature reduction of 39°C in the maximum temperature region without compromising product robustness and, thus, an improvement on lifetime prediction in 2 times in the piston combustion bowl region. Furthermore, a reduction on carbon build-up on ring belt region was also observed.

Modern engine manufacturers are under pressure to continuously improve the performance of diesel engines. Government requirements and customer demands drive significant changes to power cylinder designs. Great efforts are being made to reduce emission levels and increase operating efficiencies. The power cell unit (PCU) environment is becoming more aggressive at the same time that peak cylinder pressures are increasing. Engines are expected to perform at this high level throughout their operating life with little to no degradation in performance. Besides that, greater emphasis is also being placed on fuel efficiency of the engine. In order to meet these challenges the design of a modern ring pack should consider the utilization of high wear resistance coatings aligned with new geometries to enhance oil film control and reduce friction.

Modern SI engines focusing on CO2 emission reduction has been applying flex fuel technology to enable burning biomass fuels. The prime route is the use of ethanol fuel on these engines. The action of designing an engine to run with ethanol and gasoline (Flex-Fueled Engines) affects powercell components in different ways. The mechanical loads are higher to ethanol fuel. The combustion pressure can be increased without the risk of knocking for ethanol while for gasoline the compression rate of the piston is limited due to knocking occurrence. The spark time also occurs earlier which impacts components lubrication once the maximum load happens near the top dead center (TDC) where the sliding speed is lower and consequently there is lower oil film thickness. Such combination of spark time and sliding speed may also affect dynamics which can affect inertia and load composition of engine components.

Stricter emission regulations on Heavy-Duty Diesel (HDD) engines have brought more demanding conditions to the engine piston ring pack. This work shows and discusses some of the new features of modern HDD ring packs. The presented ring pack comprises a fully nitrided, PVD (Physical Vapor Deposition) coated, top ring. The second ring can still be a cast iron, Chromed Plated but there are also nitrided steel projects for higher durability and robustness. The oil control ring is a narrow, for better conformability, I-Shaped nitrided. Some of the ring characteristics are discussed in the paper: the PVD coating showed excellent compatibility with the smoother cylinder finishes that are being used to reduce Lube Oil Consumption. PVD coated top rings also presented lower radial wear when compared with the traditional Ceramic-Chromium coating.