Development of common rail lube oil injector for large two-stroke marine diesel engines

Abstract

The two-stroke crosshead diesel engines, nowadays moving the majority of merchant vessels, have lubrication systems which significantly contribute to their overall emissions, since they work on total loss basis: a relevant fraction of lubricant enters the exhaust duct, increasing total exhaust emissions. This paper demonstrates that a viable solution to reduce lubrication system related emissions can be found in the application of a new common rail type ( CR) lubrication system. Particularly, in the first part of this study, a common rail injector was simulated and numerically optimized by means of AMESim. The main parameters influencing lube oil injected mass were identified, with the purpose to design a highly time responsive injector. Therefore, a CR injector was realized and experimentally characterized by means of a dedicated test cell, defining the lube oil injection map over the entire engine load range. Finally, full scale engine tests allowed to evaluate oil loss at exhaust, proposing, and applying the Sulfur tracing methodology. A comparison with a pulse jet lubrication system demonstrated a relevant reduction in oil loss: 100% engine load testes demonstrated decreases ranging from 56.2% to 63.3%, while once fixed the lube oil feed rate to 0.8 g/kWh a maximum reduction in oil loss equal to 66.7% was reached. These results allow nominating the common rail lubrication system as a feasible solution to significantly reduce oil loss at exhaust of large two-stroke marine diesel engines.

Starved lubrication analysis for the top ring and cylinder liner of a two-stroke marine diesel engine considering the thermal effect of friction

“…In the 2-stroke marine diesel engines, lubricant is injected into the liner wall, the injected lubricant is no longer recycled, to reduce oil consumption and its harmful emissions, the control of oil injection quantity is very strict. 9 So, the PRCL system suffers starved lubrication. Especially for the top ring, some relevant experimental studies have also verified its starved lubrication state.…”

Cylinder Spray Lubrication of Two-Stroke Diesel Engines: Investigation of Scavenging Air, Droplet Movement and Nozzle Flow

“…They found that for lower pressure in the rail, reducing the dwell time between the first and second pulses resulted in a faster start of injection for the second event. While the experimental techniques outlined were developed for and have almost exclusively been used to study fuel injectors, some authors have also looked at lubrication oil injectors using a simulation approach [61,62]. Stark et al [61] simulated the hydraulic characteristics of a lubrication oil injector using the 1D LubeFluid code.…”

“…The injector was simulated at an injection pressure of 900 bar, which is a very large injection pressure for a lubrication oil injector. Milanese et al [62] also simulated the hydraulic response of a lubrication oil injector. They used a software called AMESim to simulate the injector.…”

“…It was found that the common rail injector had a more stable spray angle and a more abrupt ending compared to the non-return version of the valve. Milanese et al [62] investigated a lubrication system based on a common rail principle, where one pipe feeds all the lubrication oil injectors on a cylinder. The pipe is kept at constant pressure, and the oil dosage is determined by how long the injectors are kept open.…”

“…The most recent development in cylinder lubrication systems for marine two-stroke diesel engines uses the common rail principle [24,62]. The common rail principle fundamentally changes how the lubrication oil injectors function.…”