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Environmentally acceptable hydraulic fluids are increasingly specified for use in hydraulic equipment working in environmentally sensitive areas. This paper describes the research methodology that was used to develop a high performance synthetic, environmentally acceptable hydraulic fluid. Product development consisted of: (1) setting the standards for environmental acceptability, (2) screening base fluids and additives for technical performance and minimal impact on the environment, (3) designing a formulation to meet these targets and (4) field experience. Test results demonstrating the high performance and low environmental impact of the new fluid are discussed. A key challenge when formulating an environmentally acceptable hydraulic fluid is to achieve satisfactory oxidation stability. The absence of a suitable oxidation stability test, which can differentiate between environmentally acceptable fluids and correlate with field performance, has been an issue for several years.

Environmentally adapted diesel fuels defined by the Swedish Government contain extremely low levels of sulphur and have limited aromatics contents. Road trials and pump durability tests of these fuels revealed unacceptable wear in injection pumps due to low lubricity. Additive solutions were identified using bench tests and then proven in field trials. Market experience has substantiated the findings that fuels using the chosen additive give fully satisfactory performance. This paper illustrates how practical solutions to lubricity questions can be found, and is applicable wherever specifications demand fuels requiring a high degree of hydroprocessing.

Mid-infrared reflection-absorption spectroscopy, has been applied for the first time to the measurement of lubricant degradation products in the ring pack of a firing single-cylinder, IDI diesel. An IR-transmitting window, mounted in the cylinder wall, enables illumination of the moving piston by a broadband IR source located on the engine exterior. Light reflected from the piston is analysed in three wavebands to measure carbonyl oxidation products and oil volumes. Intra-cycle observations reveal differences in the apparent extent of lubricant oxidation between strokes and at different spatial locations in the ring pack. The data are interpreted in terms of a non-homogeneous sample.

In order to estimate the influence of the fuel composition on speciated hydrocarbon emissions from gasoline engines a model has been developed for the processes undergone by the fuel which escapes the main combustion event. One of the most important ways that this occurs is by trapping in crevices followed by mixing and partial oxidation with the hot burnt gas during the power and exhaust strokes. This complex process has been modelled by recognising some important characteristics. It is observed that the fraction of a fuel species emitted is well correlated with its rate constant for reaction with OH radicals and that this is independent of the rest of the fuel composition. This means that (a) the chemistry is significant (not just mixing) and (b) the radicals carrying out the oxidation originate from the burnt gases. The decoupling of radical concentrations from the fuel composition considerably simplifies the modelling.

The transport of fuel droplets into the combustion chamber of an SI engine and their subsequent evaporation has been studied, using a new optical diagnostic technique, Interferometric Laser Imaging for Droplet Sizing (ILIDS), which allows temporally and spatially resolved measurements of droplet size distributions. The measurement technique and its application to in-cylinder engine measurements are described. Measurements were made under warmed-up conditions, with open valve injection timing, in a Ricardo Hydra single cylinder engine. The results showed differences in the evolution of the droplet size distribution in cylinder with variations in load and speed. At 1200 rpm under full load, droplets arrived quickly into the cylinder, and were small, the Sauter Mean Diameter (SMD) being in the region 10-12 μm on arrival, so that mixture preparation was good.

The development of cross-flow single overhead camshaft designs of engines led to the introduction of pivoted cam followers with pads that were subjected to uni-directional rolling/sliding under heavy contact loads. Such components were prone to wear failure by a mechanism involving severe surface roughening. The initiating wear mechanism was eventually shown to be a form of “mild” wear and the Archard wear equation was used successfully to model the pattern of wear seen on cams and followers. The use of rigs to assess the wear performance of different lubricants has hitherto been a very poor predictor of engine performance, because of the complex interaction of materials, kinematics and forces in real engines. As a result, most automotive lubricant development relies on engine testing, which is expensive and time-consuming. Also, the complexities of the engine environment make it difficult to obtain much scientific insight into the tribological processes involved.

A unique time-resolved Fourier Transform InfraRed (FTIR) spectrometry technique has been developed to obtain full mid-IR lubricant spectra directly from the ring-pack region of a firing, single cylinder, diesel engine. Initial studies of the detailed spectra show a growth of oxidation products, as indicated by a strong carbonyl absorption peak, observed to increase with load close to the top ring location, for both power and exhaust strokes. Similarly, the formation of alcohol, ketone, aldehyde and carboxylate oxidation products is accessible. Thus it is possible to gauge gross changes to lubricant composition as a function of spatial location through the ring-pack, engine stroke and the severity of engine operation.

Departures from optimum stoichiometry during transients (acceleration and deceleration) and cold start can lead to significant degradation in driveability and emissions control. Such departures occur as a result of a complex interplay between fuel transport mechanisms and the fuelling strategy. The relative contributions of several of these mechanisms are affected by fuel composition. To help understand these effects an open-path differential infra-red absorption technique has been used to monitor the transient evolution of the fuel vapour phase directly within the combustion chamber. The sensor projected a narrow infra-red beam which traversed the cylinder of an optical access engine along an open path under the head, and measured the path-integrated attenuation caused by absorption of the infra-red radiation by the fuel vapour. It operated in the near infrared (NIR) spectral region around 2.3 μm, an absorption band in hydrocarbon species containing methyl groups.

This paper discusses in detail a new technique for air-fuel mixture entering individual cylinders of a multicylinder engine. The method described provides estimates of the weights of both air and fuel entering individual cylinders and the proportions of the fuel that are present as liquid at points just upstream of the inlet valves. The technique has been developed for steady-speed conditions and is not applicable to transient operating conditions.

A 1.8 litre four-cylinder engine with a slice between the head and the block carrying instrumented plugs has been used to study the growth of combustion chamber deposits and some of their effects on engine operation. Different techniques for measuring deposit thickness, knock onset and deposit effects on the thermal characteristics of the cylinder have been developed. Deposit growth as measured by deposit weight on the plugs is reasonably repeatable from run to run and cylinder to cylinder. The presence of deposits already in the cylinder does not affect deposit growth on clean plugs introduced into the combustion chamber. Deposit thickness and morphology vary substantially at different locations, the thickness being greatest at the coolest surfaces. Deposits increase the flame speed and reduce the metal temperatures just below the surface. They also reduce the mean heat flux away from the cylinder.