Seungjun Chung

Extraction and tribological investigation of top piston ring zone oil from a gasoline engine

Abstract With tightening emission regulations, increased expected fuel economy, and longer drain intervals impacting on lubricant formulation, greater understanding of how oil degrades in an automotive engine is becoming ever more important. Equally significant is the effect that this degraded lubricant has on the tribological operation of the engine, particularly its overall internal friction and component wear In a previous paper, four tests to degrade oil in a single cylinder engine were reported [1]. These tests were set up such that the lubricating oil was degraded in the ring pack before returning to the sump, where it was sampled and chemical and rheological analysis undertaken. This paper reports the extension of this work using the same Hydra engine and describes how oil has additionally been extracted from the rear of the top piston ring during engine operation. This extracted oil has then been subjected to similar analysis as the sump oil samples in the previous tests, along with additional analysis to look at the tribological properties of the oil using tribometers. The results clearly show significant differences in the rheological, tribological, and chemical properties of the fresh oil and used sump oil samples when compared with the top ring zone (TRZ) oil samples, particularly the effect of load on the levels of volatiles present in the TRZ samples and their effect on traction and friction coefficient values during tribological testing.

A robust, gravure-printed, silver nanowire/metal oxide hybrid electrode for high-throughput patterned transparent conductors

High-throughput patterning and enhanced mechanical stability are key to enabling large-area applications of metal nanowire mesh transparent electrodes. In this work, hybrid transparent conductors based on silver nanowires embedded in an indium zinc oxide matrix were prepared by high-speed gravure-printing (1.0 m s−1) from a single, stable liquid precursor. These gravure-printed films demonstrate excellent conductivity (9.3 Ω □−1) and transparency (T550nm ∼ 91%), as well as robust mechanical properties. The encapsulating indium zinc oxide matrix dramatically improves adhesion, surface roughness (Rq < 5 nm), film uniformity, and thermal stability (up to 350 °C) of the embedded silver nanowires. These properties of the hybrid films make them a suitable electrode material for a variety of printed electronic devices, such as flexible OLEDs and solar cells.

Exploitation of the coffee-ring effect to realize mechanically enhanced inkjet-printed microelectromechanical relays with U-bar-shaped cantilevers

We report a mechanically enhanced inkjet-printed microelectromechanical (MEM) relay with a U-bar-shaped cantilever by exploiting the coffee-ring effect. The printed cantilever shape, especially the effective thickness caused by the elevated walls, can be controlled during the drying process by outward convective flow of silver nanoparticles. This enhances mechanical stiffness to efficiently produce a strongly suspended cantilever that is immune to collapse- and curling-related failures. This approach to enhancing cantilever stiffness is unique to printing-based processes using metal-nanoparticle inks and is not feasible for conventional photolithography processes. The resulting printed MEM relays show a pull-in voltage of only 6.6 V and an on/off ratio of 108 with extremely low on-state resistance (∼14.3 Ω) and off-state leakage that is comparable to those of conventional silicon-based MEM relays.

The degradation of lubricants in gasoline engines: Development of a test procedure to evaluate engine oil degradation and its consequences for rheology

Tests have been undertaken to study the effects of engine parameters and lubricant blends on oil degradation and engine components. A single cylinder spark ignition research engine was used for this work. The cam shaft was run on fully formulated oil and the crank and piston ring pack on the test oils. Samples were extracted from the sump, whilst the engine was running under controlled conditions, and rheological and chemical analysis data obtained from these samples. The methodology behind the testing and the engine set up is presented, as are results for the viscosity, sump carbonyl concentration and the end of test component condition for the four tests undertaken. Comparisons between the oil blends, engine parameters and results are discussed before conclusions are drawn and areas for further work highlighted.

High-Performance Inkjet-Printed Four-Terminal Microelectromechanical Relays and Inverters

We report the first demonstration of inkjet-printed 4-terminal microelectromechanical (MEM) relays and inverters with hyper-abrupt switching that exhibit excellent electrical and mechanical characteristics. This first implementation of a printed 4-terminal device is critically important, since it allows for the realization of full complementary logic functions. The floated fourth terminal (body electrode), which allows the gate switching voltage to be adjusted, is bonded to movable channel beams via a printed epoxy layer in a planar structure, which can move downward together via the electrostatic force between the gate electrodes and body such that the channel can also actuate downward and touch the drain electrode. Because the body, channel, and drain electrodes are completely electrically separated, no detectable leakage or electrical interference between the electrodes is observed. The printed MEM relay exhibited an on-state resistance of only 3.48 Ω, immeasurable off-state leakage, subthreshold swing <1 mV/dec, and a stable operation over 10(4) cycles with a switching delay of 47 μs, and the relay inverter exhibits abrupt transitions between on/off states. The operation of the printed 4-terminal MEM relay was also verified against the results of a 3-dimensional (3D) finite element simulation.

Lubricant Degradation Studies Using a Single Cylinder Research Engine

With increasing pressure on engine oil manufacturers to extend oil drain intervals and reduce fuel consumption, whilst changing the composition of fully formulated oils to meet new CEC, ILSAC and OEM specifications, there is ever increasing need to understand the effect of oil degradation on the operating conditions and tribological performance of engines. This poster presents mechanical changes made to a single cylinder research engine to enable the study of lubricant degradation, its transport and how this links to piston assembly tribology. A summary of the research undertaken using these changes and a sample of results obtained to date are also presented.Copyright

Stress-tolerant fully inkjet-printed Reed Relays

A fully printed micro-electro-mechanical (MEM) Reed Relay is demonstrated to provide zero off-state leakage (IOFF), low on-state resistance (RON) (~15 Ω), and moderate switching delay (~32 μs), while offering excellent immunity to mechanical stress variations in the printed cantilevers. Leveraging the stress gradient in sintered metal nanoparticles films and using a novel device architecture, this device is promising for large area electronics.

The Tribological and Chemical Analysis of Top Ring Zone Samples of Fully Formulated Oil Taken From a Four Stroke Gasoline Engine

With increasing pressure on engine oil manufacturers to extend oil drain intervals and reduce fuel consumption, whilst changing the composition of fully formulated oils to meet the new CEC, ILSAC and OEM specifications, there is an ever increasing need to understand the effect of oil degradation on the operating conditions and tribological performance of engines [1]. This work samples oil from the rear of the top piston ring of an engine during the first 15 minutes from cold start and operating at steady state under three different loads. These samples, used 40 hour sump oil and fresh oil have been subjected to tribological tests and chemical analysis.Copyright