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This paper reports high-speed (10 kHz and 100 kHz) 2-D Raman/Rayleigh measurements of a hydrogen (H2) jet issued from a Bosch HDEV4 hollow-cone piezo injector in a high-volume constant pressure vessel. During the experiments, a Pa = 10 bar ambient environment with pure nitrogen (N2) is created in the chamber at T = 298 K, and pure H2 is injected vertically with an injection pressure of Pi = 51 bar. To accommodate the transient nature of the injections, a kHz-rate burst-mode laser system with second harmonic output at λ = 532 nm and high-speed CMOS cameras are employed. By sequentially separating the scattered light using dichroic mirrors and bandpass filters, both elastic Rayleigh (λ = 532 nm) and inelastic N2 (λ = 607 nm) and H2 (λ = 683 nm) Raman signals are recorded on individual cameras. With the help of the wavelet denoising algorithm, the detection limit of 2-D Raman imaging is greatly expanded.

The principal objective of the present work is to investigate the fundamental characteristics of a commercially available outwardly opening twin-fluid injector, which utilizes air-assisted atomization principle to attain pulse-type injection of fuel-air mixture. The electromagnetic characteristics of this injector were simulated and the effects of dominating parameters on the electromagnetic force to drive injector were ascertained. On that basis, this paper elaborates on the fundamental characteristics of air-assisted spray using gasoline and kerosene with the employment of two types of optical testing techniques. The spray morphological evolution under varied fuel injection durations and ambient pressures were captured with high-speed shadowgraph thus the corresponding external macroscopic characteristics were obtained and further compared. Spray droplet velocity and diameter at fixed monitoring location were measured by using PDPA (Phase Doppler Particle Analyzer).

Partially premixed compression ignition (PPCI) engines operating with a low temperature highly homogeneous charge have been demonstrated previously using conventional diesel fuel. The short ignition delay of conventional diesel fuel requires high fuel injection pressures to achieve adequate premixing along with high levels of EGR (exhaust gas recirculation) to achieve low NOx emissions. Low load operating regions are typified by substantial emissions of CO and HC and there exists an upper operating load limitation due to very high rates of in-cylinder gas pressure rise. In this study mixtures of gasoline and diesel fuel were investigated using a multi-cylinder light duty diesel engine. It was found that an increased proportion of gasoline fuel reduced smoke emissions at higher operating loads through an increase in charge premixing resulting from an increase in ignition delay and higher fuel volatility.

Highly homogeneous compression ignition is difficult to achieve in a direct injection diesel engine. The difficulty of achieving adequate fuel vaporization and the problems of fuel spray wall impingement are the main factors. Limitation of the maximum operating load results from high rates of pressure rise that occur in this combustion regime. The levels of HC and CO emissions are raised substantially when compared with conventional combustion and remain a significant emission factor. In this study, two methods of achieving highly homogeneous combustion in a direct injection diesel engine were investigated, Nissan MK type and early injection. The effects of fuel injection pressure, injection timing, EGR level, EGR cooler efficiency and compression ratio were examined using a conventional 4 cylinder 2.0L common rail diesel engine with 18.4:1 and 14.4:1 compression ratios.

A novel Fast Response Chemiluminescence Detector and a Fast Flame Ionization detector have been used to examine the instantaneous NO and unburnt hydrocarbon concentration in the cylinder and exhaust port of a DI Diesel engine. The in-cylinder results indicate very high levels of NO in the premixed phase of combustion, followed by generally lower levels during the diffusion burning phase. Hydrocarbon signals also indicate significant detail. The in-cylinder uHC signal is consistent with the probe location being between two of the fuel sprays. Both in-cylinder and exhaust results indicate rather high cyclic variability in the NO levels at steady conditions. Variations in the timing and structure of the exhaust uHC signal during the valve open period with load may give insight into the fuel spray/air motion.

The paper presents a computer simulation of flow and heat transfer phenomena in the intake port of a spark ignition engine with port fuel injection. Engine cold starting conditions are studied including the effects of in-cylinder mixture back flow into the port. One dimensional air flow and wall fuel film flow models and a two dimensional fuel droplet flow model have been developed using a combination of finite difference approaches. As a result, predictions are obtained that provide detailed picture of the air-fuel mixture properties along the intake port. The model may be of special importance for exhaust gas ignition system simulation as it will provide data concerning mixture formation under conditions of excessive fuel injection during engine start-up. The calculations performed are shown to be phenomenologically correct.

The flow and heat transfer phenomena in the intake port of a spark ignition engine with port fuel injection play a significant role in the mixture preparation process, especially at part load. The backflow of the hot burned gas from the cylinder into the intake port when the intake valve is opened breaks up any liquid film around the inlet valve, influences gas and wall temperatures, and has a major effect on the fuel vaporization process. The backflow of in-cylinder mixture with its residual component during the compression stroke prior to inlet valve closing fills part of the port with gas at higher than fresh mixture temperature. To quantify these phenomena, time-resolved measurements of the hydrocarbon concentration profile along the center-line of the intake port were made with a fast-response flame ionization detector, and of the gas temperature with a fine wire resistance thermometer, in a single-cylinder engine running with premixed propane/air mixture.