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Transient behavior of the engine is one of the most crucial factors for motorcycle features. Characterization of the fuel film with port fuel injection (PFI) is necessary to enhance this feature with keeping others, such as high output, low emissions and good fuel consumption. In order to resolve the complicated phenomena in real engine condition into simple physical issues, a simulated intake port was used in our research with Laser Induced Fluorescence (LIF) technique to allow accurate measurement of the fuel film thickness, complemented by visualization of the film development and spray behavior using high-speed video imaging. Useful results have been conducted from the parametric studies with various sets of conditions, such as injection quantity, air velocity and port backpressure.

Measurements of flow, spray, combustion and performance characteristics are reported for a Hydra direct-injection diesel, based on the Ford 2.5 L, engine and equipped with a variable-swirl port, a unit fuel injector and optical access through the liner and piston. The results provide links between the pre-combustion and combustion flow and, at the same time, between purpose-built single-cylinder optical engines and multi-cylinder production engines of nearly identical combustion chamber geometry. In particular, the spray penetration was found to depend on engine speed, rather than load, with velocities up to around 260 m/s at atmospheric pressure and temperature which are reduced by a factor of 2.5 under operating conditions and seem to be unaffected by swirl. The duration of combustion was reduced with increasing swirl and ignition delay increased linearly with engine speed.

Local measurements of the mean and rms velocities have been obtained by laser Doppler velocimetry in the coolant passages of a transparent model of a Ford 2.5L diesel cylinder head and block at a steady flowrate of 6.83 × 10-4 M3/s. The simulation of the coolant fluid by a mixture of hydrocarbon fluids at a predetermined constant temperature allowed accurate matching of the refractive index to that of the acrylic model, thus providing optical access for LDV measurements of the internal flow in sensitive areas where cooling is essential to prevent metal-fatigue failure. The results were obtained in sufficient detail to allow further validation of CFD coolant flow models.

By using empirical and semi-empirical relationships previously reported in the literature, non-linear viscoelastic properties of a number of lubricants have been determined from their linear viscoelastic behaviour, as measured by an oscillatory rheometer. Similarly to polymeric viscosity index improved (VII) lubricants, non-polymeric mineral blends were also shown to display viscoelastic behaviour. A general equation is suggested that allows the first normal stress difference which characterises the viscoelastic behaviour of lubricants to be expressed as a function of the shear viscosity.

Direct flame imaging and pressure analysis were applied to the combustion of gasoline and compressed natural gas (CNG) in a single-cylinder, four-valve spark-ignition engine equipped with optical access via quartz windows in the cylinder liner and piston crown. Tests were performed at three engine speed/load conditions and at equivalence ratios of 1.0, 0.9 and 0.8. The four-valve head incorporated two different port geometries, with and without metal sleeves to deflect the intake air flow, in order to investigate the effect of tumble strength on combustion and engine-out emissions of unburned hydrocarbons and NOx. The results showed that sleeving of the intake ports produced a significant increase in IMEP and a reduction in CoV IMEP for both CNG and gasoline, due to the greatly reduced bum duration.

Laser Doppler velocimetry, phase Doppler anemometry and Mie scattering were applied to a single-cylinder, four-valve, spark-ignition gasoline research engine equipped with a fully transparent liner and piston, to obtain information about the tumble flow and the droplet size and velocity distributions during induction and compression, for lean air/fuel mixture ratios of 17.5 and 24 and with closed-valve and open-valve fuel injection. The mixture distribution obtained with the two injection strategies was correlated with flame images, pressure analysis and exhaust emissions which confirmed the advantages of combining open-valve injection with tumble to allow stable and efficient engine operation at an air/fuel ratio of 24 through charge stratification and faster flame growth.

The ability of certain induction systems to enhance turbulence levels at the time of ignition, through formation of long-lived tumbling vortices on the plane of the valve and cylinder axes, has been investigated in a two-valve spark-ignition engine by rotating the intake port at 90° and 45° to the orientation of production directed ports. Detailed measurements of the three velocity components, obtained by laser velocimetry, revealed that the 90° port generated a pure tumble motion, with a maximum tumbling vortex ratio of 1.5 at 295°CA, zero swirl, and 42% turbulence enhancement relative to the standard configuration, while the 45° port gave rise to a combined tumble/swirl structure with a maximum tumbling vortex ratio of 0.5 at 285°CA, swirl ratio of 1.0 at TDC, and turbulence enhancement of 24%. The implications of the two types of flow structures for combustion are discussed.

The spatial and temporal characteristics of a diesel spray injected into the atmosphere through a multi-hole nozzle used in small DI Diesel engines have been investigated by laser techniques as a function of pump speed and load. The results showed that spray tip penetration and velocity depend on injection frequency rather than injected volume and the spray is asymmetric during the early and main part of the injection period. In the time/space domain different structures have been identified within the injection period, with the early injection period characterized by a well atomized cloud of droplets, the main period by the spray head and a dense core and the late injection period by the disintegrating dense core and the spray tail. IN DIRECT-INJECTION DIESEL ENGINES for passenger cars, fuel is injected through multi-hole nozzles at high pressure to promote mixing with the rapidly swirling air inside the combustion chamber.

The performance of multi-hole injectors designed for use in second-generation direct-injection gasoline engines has been characterised in a constant-volume chamber. Two types of multi-hole injector have been used: the first has 11 holes, with one hole on the axis of the injector and the rest around the axis at 30 degrees apart, and the second has 6 asymmetric holes located around the nozzle axis. Measurements of droplet axial and radial velocity components and their diameter were obtained using a 2-D phase Doppler anemometer (PDA) at injection pressures up to 120 bar, chamber pressures from atmospheric to 8 bar, and ambient temperatures. Complementary spray visualisation made use of a pulsed light and a CCD camera synchronised with the injection process.

A transparent enlarged model of a six-hole injector used in the development of emerging gasoline direct-injection engines was manufactured with full optical access. The working fluid was water circulating through the injector nozzle under steady-state flow conditions at different flow rates, pressures and needle positions. Simultaneous matching of the Reynolds and cavitation numbers has allowed direct comparison between the cavitation regimes present in real-size and enlarged nozzles. The experimental results from the model injector, as part of a research programme into second-generation direct-injection spark-ignition engines, are presented and discussed. The main objective of this investigation was to characterise the cavitation process in the sac volume and nozzle holes under different operating conditions. This has been achieved by visualizing the nozzle cavitation structures in two planes simultaneously using two synchronised high-speed cameras.

The near nozzle exit flow and spray structure generated by an enlarged model of a second generation pintle type outwards opening injector have been investigated under steady flow conditions as a function of flow-rate and needle lift. A high resolution CCD camera and high-speed video camera have been employed in this study to obtain high-magnification images of the internal nozzle exit flow in order to identify the origin of string ligaments/droplets formation at the nozzle exit. The images of the flow around the nozzle seat area showed clearly that air was entrained from outside into the nozzle seat area under certain flow operating conditions (low cavitation number, CN); the formed air pockets inside the annular nozzle proved to be the main cause of the breaking of the fuel liquid film into strings as it emerged from the nozzle with a structure consisting of alternating thin and thick liquid filaments.

A laser-induced fluorescence (LIF) system has been developed to obtain measurements of the instantaneous lubricant film thickness in the piston-cylinder assembly of a firing single-cylinder, direct-injection diesel engine. Measurements were made at top-dead-centre (TDC), mid-stroke and bottom-dead-centre (BDC) position by means of three fibre optic probes inserted into the cylinder liner and mounted flush with its surface. Following extensive repeatability tests, the cycle-averaged lubricant film thickness was estimated for different multi-grade oils as a function of engine speed, load and temperature. The results quantified the dependence of the film thickness ahead, under and behind the piston rings on oil chemistry and viscometric properties, thus confirming the important role of the LIF technique in the development and formulation of new engine oils.

Laser induced fluorescence (LIF) was used in the cylinder liner of a firing single-cylinder direct-injection diesel engine to characterise the development of the lubricant film during the first 200 engine cycles under cold-start conditions. The results have provided information on the rate of oil film development which has proved to be a highly unsteady process due to the complicated oil transport processes through the ring-pack.

The in-cylinder flow, mixture distribution, combustion and exhaust emissions in a research, five-valve purpose-built gasoline engine are discussed on the basis of measurements obtained using laser Doppler velocimetry (LDV), fast spark-plug hydrocarbon sampling, flame imaging and NOx/HC emissions using fast chemiluminescent and flame ionisation detectors/analysers. These measurements have been complemented by steady flow testing of various cylinder head configurations, involving single- and three-valve operation, in terms of flow capacity and in-cylinder tumble strength.

The health threat from sub-100 nm particulates, emitted in significant numbers from gasoline vehicles, and anticipated changes in legislation to address this, have prompted investigation of techniques capable of trapping and oxidizing particulates from gasoline engines. Numerical studies have indicated that cooling to encourage particle capture by thermophoresis is less effective than use of electrostatic fields. A laboratory wire-cylinder electrostatic trap is under development, showing promising initial results. As an alternative trapping technique, the effectiveness of a cordierite wall-flow filter has been demonstrated, in simulation experiments and on a GDI-engined vehicle. Catalysts have been identified for particulate oxidation at typical exhaust temperatures, using water vapour and carbon dioxide as the oxygen source and retaining activity after short-term high-temperature aging.

Motivated by the possibility of future emission regulations based on particle number as well as mass, after-treatment of ultrafine particles by a cordierite wallflow filter has been investigated. In a laboratory simulation, synthetic carbon particles of known size and concentration in air were captured with number-based efficiency exceeding 70% in the 20–100 nm size range. Effects of temperature, up to 400°C, filter loading time and ambient-temperature sample dilution have been quantified. Steady-speed and European drive cycle results for the same filter fitted to a passenger car with gasoline direct-injection engine have shown promising reductions in emissions, except at the highest speed of the cycle.

A comprehensive set of computational and experimental results for high- pressure diesel sprays are presented and discussed. The test cases investigated include injection of diesel into air under both atmospheric and high pressure/temperature chamber conditions, injection against pressurized and cross-flowing CF6 simulating respectively the density and flow conditions of a diesel engine at the time of injection, as well as injection into the piston bowl of both research and production turbocharged high-speed DI diesel engines. A variety of high-pressure injection systems and injector nozzles have been used including mechanical and electronic high-pressure pumps as well as common-rail systems connected to nozzles incorporating a varying number of holes with diameters ranging from conventional to micro-size.

The initiation and development of cavitation in enlarged transparent acrylic models of six-hole nozzles for direct injection Diesel engines has been visualised by a high-speed digital video camera in a purpose-built refractive index matching test rig. The obtained high temporal resolution images have allowed improved understanding of the origin of the cavitation structures in Diesel injector nozzles and clarification of the effect of sac geometry (conical mini-sac vs. VCO) on cavitation initiation and development in the nozzle holes. The link between cavitation and flow turbulence in the sac volume and, more importantly, in the injection holes has been quantified through measurements of the flow by laser Doppler velocimetry (LDV) at a number of planes as a function of the Reynolds and cavitation numbers.

An investigation into the spray structure generated by two swirl pressure atomisers under various operating conditions in a constant-volume chamber and the in-cylinder flow pattern in an optical research direct-injection gasoline engine has been performed using CCD camera and laser Doppler velocimetry, respectively. The results provided detailed information about the effect of back pressure on the spray structure generated by the two injectors and the in-cylinder flow field which the sprays encounter following fuel injection into the cylinder during the induction and compression strokes.

The numerical methodology used to predict the flow inside pressure-swirl atomizers used with gasoline direct injection engines and the subsequent spray development is presented. Validation of the two-phase CFD models used takes place against film thickness measurements obtained from high resolution CCD-based images taken inside the discharge hole of a pressure swirl atomizer modified to incorporate a transparent hole extension. The transient evolution of the film thickness and its mean axial and swirl velocity components as it emerges from the nozzle hole is then used as input to a spray CFD model predicting the development of both non-evaporating and evaporating sprays under a variety of back pressure and temperature conditions. Model predictions are compared with phase Doppler anemometry measurements of the temporal and spatial variation of the droplet size and velocity as well as CCD spray images.