Lube oil chemistry influences on autoignition as measured in an ignition quality tester

Derived Cetane Numbers (DCNs) of engine lubricating oil/multicomponent 95 Research Octane Number (RON) gasoline surrogate mixtures were measured in an Ignition Quality Tester (IQT). Measurements separately assess the effects of calcium- and magnesium-based detergent additive fraction, oil viscosity, oil degradation, and base oil classification on mixture ignition propensity at conditions with relevance to low speed pre-ignition (LSPI) in gasoline engines. Testing of 0–25% (by mass) oil blended into a six-component surrogate mixture representing an unleaded “average” European gasoline blend is used to determine sensitivity of DCN responses to variations in the properties. With one exception, mixture DCNs were found to increase with lubricating oil content. Despite variation in calcium and magnesium concentrations, DCN responses for all oil blends indicate no statistically significant effect of either calcium or magnesium. Similarly, neither aging of nor peroxide addition to the oil yields significant DCN changes compared to untreated oils. However, a distinct response is found for variations in the base lubricant chemical structural properties. At 25% oil blending with gasoline surrogate, the measured DCNs (RONs) of different group base oils range from 19.6 (95.7) to 42.1 (46.2). The DCN increases with increasing base oil API Group Number (I through IV); however, mixture DCN was found to decrease for a 25% blend of Group V-B with the gasoline surrogate. Using quantitative ¹H NMR, the Group Number trend is interpreted to be a consequence of linear vs. branched character of the paraffinic base oil composition. Taken together, the present results indicate that at ASTM D6890 DCN test conditions, there is no significant ignition effect attributable to reasonable variations in the lubricant's calcium or magnesium content, viscosity, or degree of degradation. Instead, the isomeric character of the paraffinic base oil appears to be most significant in controlling lubricant autoignition properties relative to those of gasolines.     

Relaxation and Creep of Dry Bulk Solids

In former investigations it has been shown that creep (constant stress, altering strain) and relaxation (constant strain, decreasing stress) can be observed with dry bulk solids. Both effects are covered when investigating the time dependent behaviour of bulk solids where time dependence can also mean an increase of the deformation resistance with increasing deformation rate. In this paper the investigated time dependent effects do not include time consolidation. The effects of creep and relaxation are often neglected for bulk solids because in many applications the influence of these time dependent behaviours is of minor importance. A deeper insight into the bulk solids flow characteristics and mechanisms can only be obtained when time dependence is taken into consideration.     

A low cost uncooled focal plane array test system

The commercial test equipments from Pulse Instruments, Lumitron and Electro Optical Industries Inc. are very expensive. So, we proposed a new method of very low cost test system for testing the non-uniformity and signal/noise (S/N) and other characteristics of the uncooled focal plane array (UFPA). It uses complex programmable logic device to generate the necessary pulse for the UFPA and the low noise low dropout micropower regulator to obtain the low noise bias. A proportional-integral-differential controlled thermal electrical cooler based on micro-processor unit stabilizes the UFPA. The National Instruments 6111E Data Acquisition Card is used to convert the analog output of UFPA into digital signal into computer. Its 12-bits conversion capability provides sufficient accuracy for evaluating the S/N ratio and non-uniformity of 128×128 pixels UFPA. Labview is used to analyze the signal. The instrument is fast and convenient to adapt the system to other types of UFPA. Further discussion is presented to determine factors that affect the accuracy of the tester.     

On the Development of a Mesoscale Friction Tester

MEMS and NEMS devices typically have a large surface area to volume ratio. As a result, a major concern in the development of such devices is friction. Contact radii in MEMS and NEMS devices are expected to range from 10⁻⁸<a<10⁻⁵ m. This regime, which generally lies between the limits of single asperity and macroscopic contact, has yet to be explored because the apparati used to characterize friction at these limits do not operate in the range of forces appropriate to these length scales. A Mesoscale Friction Tester (MFT) with smooth probe tip radii from 50 nm to 50 μm and capable of applying forces ranging from 10 nN to l mN over contact radii from 10 nm to 10 μm has been developed to address this need. With carefully planned experiments, this device has the potential to help answer unresolved questions regarding friction mechanisms in the mesoscale range.