No description available.

Particulate emissions from diesel engines have been a key issue for diesel engine developers in recent decades. Their work has succeeded in reducing the exhaust particles from the combustion of fuel, which has led to increasing interest in the contribution of particulates from lubrication oil. When discussing oil-related particulate emissions, hydrocarbon particles are customarily referred to. This thesis uses a broader definition, in which oil-related particulate emissions are modelled not only by the hydrocarbons, but also include the ash, carbons, and sulphate oil particulate emissions. The model developed in the project uses input data as oil consumption and oil ash content combined with tuning parameters, such as the oil ash transfer rate (ash emissions divided by oil consumption and oil ash content). Controlled engine tests have been performed to verify assumptions and fill knowledge gaps. The model can be applied to a variety of diesel engines, although the tuning factors might have to be reset. For example, introducing diesel particulate filters would dramatically reduce the oil ash emissions, since oil ash would accumulate in the filter. Oil consumption has played a central role in the present research. The modelling results indicate that special attention should be paid to oil consumption under running conditions with a low in-cylinder temperature, since the oil survival rate is high there. Under low-load and motoring conditions, hydrocarbons proved to be the main contributor to oil-related particulate emissions. At high engine load, oil ash emissions were the largest contributor to oil-related particulate emissions. / QC 20101103

<p>In recent decades much effort has gone into reducing particle emissions in the exhaust gases of heavy-duty diesel engines. Engine development has now reached the stage where it is worth to put heavy focus on the contribution of lubricating oil to particulate emissions in order to further reduce these emissions.</p><p> </p><p>A literature study demonstrates that the cylinder system is usually the largest source of oil-related particles. Oil consumption in the cylinder can be divided into <em>throw-off</em> effects when inertia forces act on the piston, piston rings and oil; <em>evaporation</em> from hot surfaces; <em>reverse blow-by</em> when gas pressure drives the oil consumption; and <em>top land scraping </em>when oil is scraped off the cylinder liner.</p><p> </p><p>The pressure between the compression rings strongly affects the stability and position of the upper compression ring as well as the oil consumption caused by the reverse blow-by. A method to measure the inter-ring pressure was developed and evaluated. The measurements showed that cycle-to-cycle variations were small, but that the inter-ring pressure varied over time. Calculations with AVL Excite Piston and Rings confirmed that ring gap positions can have a major influence on the inter-ring pressure.</p><p> </p><p>The measured particle size and number distributions at motoring conditions show interesting and unexpected results. The high number of particles with a diameter of around 100 nm was greatly reduced when the temperature in the diluter was increased. The mean number particle diameter decreased until 10 nm and then became stable independent of further temperature increase. Other authors have found that the small particles (nucleation mode) are reduced and the larger particles (accumulation mode) are more or less unaffected when exhaust gases are heated up and diluted.  </p><p> </p>

In recent decades much effort has gone into reducing particle emissions in the exhaust gases of heavy-duty diesel engines. Engine development has now reached the stage where it is worth to put heavy focus on the contribution of lubricating oil to particulate emissions in order to further reduce these emissions. A literature study demonstrates that the cylinder system is usually the largest source of oil-related particles. Oil consumption in the cylinder can be divided into throw-off effects when inertia forces act on the piston, piston rings and oil; evaporation from hot surfaces; reverse blow-by when gas pressure drives the oil consumption; and top land scraping when oil is scraped off the cylinder liner. The pressure between the compression rings strongly affects the stability and position of the upper compression ring as well as the oil consumption caused by the reverse blow-by. A method to measure the inter-ring pressure was developed and evaluated. The measurements showed that cycle-to-cycle variations were small, but that the inter-ring pressure varied over time. Calculations with AVL Excite Piston and Rings confirmed that ring gap positions can have a major influence on the inter-ring pressure. The measured particle size and number distributions at motoring conditions show interesting and unexpected results. The high number of particles with a diameter of around 100 nm was greatly reduced when the temperature in the diluter was increased. The mean number particle diameter decreased until 10 nm and then became stable independent of further temperature increase. Other authors have found that the small particles (nucleation mode) are reduced and the larger particles (accumulation mode) are more or less unaffected when exhaust gases are heated up and diluted. / QC 20101112

No description available.

Oil feed grooves are implemented in reciprocating compressor piston applications to assure a constant supply of lubricating oil on bearing surfaces and decrease friction loss. In a hermetically sealed compressor, due to small clearances encountered, oil supply becomes critical in order not to operate in boundary lubrication regime. Due to the small size of the piston and small piston &ndash / cylinder clearance, a partial lubrication regime is present. In the current study, a model that solves Reynolds&rsquo / equation for piston-cylinder lubrication and the average Reynolds&rsquo / equation that considers the effect of roughness on partially lubricated bearing for a compressor piston with oil feed grooves is developed. A parametric study is carried out to investigate the effects of piston design parameters and then arrive at an improved piston performance by using alternative designs for oil feed groove and the other design parameters.