Tribological investigations of the piston assembly and liner of a gasoline engine

The automotive industry is being forced towards greater efficiency, increased engine power from smaller engines and lower environmental impact by both governmental legislation and public opinion. Oil drain intervals are increasing whilst emissions legislation limit the use of current wear protection and antioxidant additives containing elements such as phosphorus and sulphur. To address these demands and challenges an increased understanding of the link between lubricant degradation, its transport and residence time, and the effect on piston assembly tribology is required. The aim of the work reported in this paper was to further develop the understanding of the effect degraded lubricants have on piston assembly tribology. The small oil volumes and environmental conditions in the piston assembly make the affective lubrication and protection of components in this region one of the most challenging areas of tribology. This was carried out through an extensive experimental programme using a research engine, tribometer testing and chemical and rheological analysis of lubricant samples

An innovation integrated approach to testing motorcycle drive chain lubricants

An innovative integrated approach to the testing and comparison of motorcycle drive chain lubricants is presented. This is a novel way of testing the lubrication by using loaded operating chains and sprockets. A test rig has been designed to operate chains and sprockets in a clean environment and allow direct comparison between different lubricants. The advantage of this method over previous techniques is that it allows the differentiation of lubricants in a more controlled operating environment and evaluates the overall lubricant performance as opposed to individual properties. The lubricants tested were a wax spray, PTFE spray and drip fed light oil. The test rig allowed measurement of the power saved by the lubricant in running the chains and sprockets. Chain length and component masses were also taken before and after running the chains and sprockets under load on the test rig. The results clearly show that any lubricant is preferable to none. The drip fed oil provided the greatest power saving and wear protection between the chain rollers and pins and the spray lubricants provided the highest level of protection between rollers and sprocket

Influence of gasoline engine lubricant on tribological performance, fuel economy and emissions

The requirement for increased performance, improved fuel economy and reduced emissions is constantly sustaining the demand for research into combustion, fuels and lubricants. Due to the nature of the operation of an engine and the current market climate the lubricant not only has to respond to these requirements, but also to changes in engine design, fuelling methods and fuel types, increased power densities and developments in emissions formation and after-treatment. This paper will describe advances made at the authors’ institution to elucidate the influence of gasoline engine lubricant on tribological performance, fuel economy and emissions, giving examples of work undertaken and then look to future possible lubricant demands

Lubricant degradation, transport and the effect of extended oil drain intervals on piston assembly tribology

There are ever increasing demands on lubricant manufacturers to meet governmental legislation and customer needs by improving fuel economy, engine durability and exhaust system compatibility as shown by the introduction of GF4 and move towards GF5 specification oils. This has created an ever increasing need to understand how oil degrades in an engine and how this degraded oil affects piston assembly tribology. This review conference paper will give an overview of a collaborative project that has been undertaken to further enhance the understanding of how lubricant degrades in an operating engine, its transport through the engine and effect upon piston assembly tribology

Charge and CP symmetry breaking in two Higgs doublet models

We show that, for the most generic model with two Higgs doublets possessing a minimum that preserves the $U(1)_{em}$ symmetry, charge breaking (CB) cannot occur. If CB does not occur, the potential could have two different minima, and there is in principle no general argument to show which one is the deepest. The depth of the potential at a stationary point that breaks CB or CP, relative to the $U(1)_{em}$ preserving minimum, is proportional to the squared mass of the charged or pseudoscalar Higgs, respectively

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

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

Effective Potential for Uniform Magnetic Fields through Pauli Interaction

We have calculated the explicit form of the real and imaginary parts of the effective potential for uniform magnetic fields which interact with spin-1/2 fermions through the Pauli interaction. It is found that the non-vanishing imaginary part develops for a magnetic field stronger than a critical field, whose strength is the ratio of the fermion mass to its magnetic moment. This implies the instability of the uniform magnetic field beyond the critical field strength to produce fermion pairs with the production rate density $w(x)=\frac{m^{4}}{24\pi}(\frac{|\mu B|}{m}-1)^{3}(\frac{|\mu B|}{m}+3)$ in the presence of Pauli interaction.Comment: 9 pages with 1 figur

Production of Neutral Fermion in Linear Magnetic Field through Pauli Interaction

We calculate the production rate of neutral fermions in linear magnetic fields through the Pauli interaction. It is found that the production rate is exponentially decreasing function with respect to the inverse of the magnetic field gradient, which shows the non-perturbative characteristics analogous to the Schwinger process. It turns out that the production rate density depends on both the gradient and the strength of magnetic fields in 3+1 dimension. It is quite different from the result in 2+1 dimension, where the production rate depends only on the gradient of the magnetic fields, not on the strength of the magnetic fields. It is also found that the production of neutral fermions through the Pauli interaction is a magnetic effect whereas the production of charged particles through minimal coupling is an electric effect.Comment: 11 pages, 2 figure

Monte Carlo Simulation of Sinusoidally Modulated Superlattice Growth

The fabrication of ZnSe/ZnTe superlattices grown by the process of rotating the substrate in the presence of an inhomogeneous flux distribution instead of successively closing and opening of source shutters is studied via Monte Carlo simulations. It is found that the concentration of each compound is sinusoidally modulated along the growth direction, caused by the uneven arrival of Se and Te atoms at a given point of the sample, and by the variation of the Te/Se ratio at that point due to the rotation of the substrate. In this way we obtain a ZnSe$_{1-x}$Te$_x$ alloy in which the composition $x$ varies sinusoidally along the growth direction. The period of the modulation is directly controlled by the rate of the substrate rotation. The amplitude of the compositional modulation is monotonous for small angular velocities of the substrate rotation, but is itself modulated for large angular velocities. The average amplitude of the modulation pattern decreases as the angular velocity of substrate rotation increases and the measurement position approaches the center of rotation. The simulation results are in good agreement with previously published experimental measurements on superlattices fabricated in this manner