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The pre-chamber combustion (PCC) concept is a proven lean or diluted combustion technique for internal combustion engines with benefits in engine efficiency and reduced NOx emissions. The engine lean operation limit can be extended by supplying auxiliary fuel into the pre-chamber and thereby, achieving mixture stratification inside the pre-chamber over the main chamber. Introducing liquid fuels into the pre-chambers is challenging owing to the small form factor of the pre-chamber. With a conventional injector, the fuel penetrates in liquid form and impinges on the pre-chamber walls, which leads to increased unburned hydrocarbon emissions from the pre-chamber. In this study, a prototype liquid fuel injector is introduced which preheats the fuel within a heated chamber fitted with an electrical heating element before injecting an effervescently atomized spray into the pre-chamber.

NOx pollution from diesel engines has been stated as causing over 10 000 pre-mature deaths annually and predictions are showing that this level will increase [1]. In order to decrease this growing global problem, exhaust after-treatment systems for diesel engines have to be improved, this is especially so for vehicles carrying freight as their use of diesel engines is expected to carry on into the future [2]. The most common way to reduce diesel engine NOx out emissions is to use SCR. SCR operates by injecting aqueous Urea solution, 32.5% by volume (AUS-32), that evaporates prior the catalytic surface of the SCR-catalyst. Due to a catalytic reaction within the catalyst, NOx is converted nominally into Nitrogen and Water. Currently, the evaporative process is enhanced by aggressive mixer plates and long flow paths.

The ideal attributes of light weight, low cost and high power density have made the 2-stroke engine unrivalled in the scooter and moped market for many years. However, the challenges of meeting new emissions regulations, especially the latest Euro III emission test cycle have reduced the 2-stroke's dominance and it is now often considered to be too dirty and inefficient to have a future. As a result its product placement is on the decline. This paper introduces and discusses the latest application of a low-cost high-frequency injection system (Pulse Count Injection [ 1 , 2 ]) to both the fuel flow and lubrication oil flow of a 2-stroke scooter; allowing both fluids to be individually mapped and optimised for the complete engine operating range. This in turn enables the 2-stroke engine to pass the latest Euro III test whilst improving the fuel economy by a considerable margin, without changing the architecture of the engine.

Small engines (<19kW) are used in many off-road applications, in both the domestic and industrial markets. The dominant driving force in these markets is cost; therefore the vast majority of these engines still use low cost carburettors to meter the fuel into the intake port. However all these engines are now facing increasingly strict emission targets and hence require new technologies to meet these new regulations, but any new technology must be extremely cost effective to be applicable. The conventional fuel injection solutions used for many years in the automotive market require complex systems including a fuel pump, pressure regulator, and fuel injector coupled to a sophisticated control module and a multitude of sensors. This type of solution is far too complex and expensive for the vast majority of engines in the small engines market, and would cost significantly more than the engine itself. A novel solution to this problem is high-frequency Pulse Count Injection (PCI).

Most small engine manufacturers are looking to introduce fuel control technology to reduce engine out emissions, however most available conventional fuel injectors consume high levels of power to achieve controlled injection and suitable atomisation of the fuel. Typical fuel injection pressures of 300kPa are required to achieve pulsed injection and up to 10MPa to achieve full atomisation. The addition of an extra air delivery system at pressures of 600kPa can also be employed to atomise the fuel. These methods require many 100's of Watt's of power making them unsuitable for the vast majority of small engine applications. This paper presents experimental data from a novel electrostatic atomiser designed specifically for application to small engines, with very low power requirements and excellent fuel atomisation.