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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.

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.

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 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 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.

The diesel engine is the most efficient user of fossil fuels for vehicle propulsion and seems to best fulfill the requirements of the future. It is for this reason that Volkswagen has initiated a very broad research programme for diesels. The purpose of this paper is to build a bridge between fundamental research and technical developments which could allow evaluation of the prospects of direct- injection diesels as powerplants of choice for passenger cars in the turn of the century. The current knowledge on mixture formation, combustion and pollutant formation in diesel engines is presented and discussed with special emphasis given to the concept of the direct-injection diesel engine.

The injection rate signals from a commercial diesel fuel injection system, based on a distributor pump driven by a DC motor, were characterised independently and consecutively by two injection rate meters based on the Zeuch and Bosch methods. The signals were first analysed in terms of their shot-to-shot variations over 64 consecutive injections and the correlations between needle lift and injection rate over a range of pump speeds and loads quantified by Fast Fourier Transform. A direct comparison of the injection rate signals on a cycle-resolved basis was achieved by connecting two consecutive injectors from the pump-line-nozzle injection system to a Bosch- and a Zeuch-based injection rate meters. The signals were acquired over a large number of injections in terms of mean and rms of the injected quantity, mean injection rate, maximum injection rate, average cumulative fuel injected and average injection duration.

The continuity and momentum equations for a pump-pipe-nozzle fuel injection system have been solved by a computer simulation program employing both the Runge-Kutta method and the more widely used method of characteristics. This allows the prediction of fluid phenomena and the dynamics of the mechanical components based on the geometry of the FIE system. The simulation includes the effects of possible cavitation, system leakage as well as variations in fuel density and bulk modulus. The computer model has been made as flexible as possible by using a modular format and inputting the system parameters from external files or dialog boxes. Experimentation was done on a Bosch VE type distributor pump supplying a multi-hole type nozzle which allowed preliminary evaluation of the model by comparing the predicted and measured injection rates and line pressures over a range of pump speeds and loads.

The effect of inlet port design on swirl generation has been investigated for four helical ports from production, prototype and research Dl diesel engines by analyzing experimentally measured steady flow velocity distributions at the inlet valve curtain area and comparing their swirl characteristics in terms of the calculated in-cylinder angular momentum components and swirl ratio under operating conditions.