As components of pump-line-nozzle injection systems, conventional fuel injection valves ensure that when a defined opening pressure of the fuel supplied by the injection pump is exceeded, the fuel is injected very quickly in a uniform fine atomisation.
Here not only a precise begin of injection is very important but also fast closing at the end of the injection process. Proper static and dynamic design of the injection hydraulics prevents so-called needle shocks. This reliably prevents even very minor unintended post-injection with after-dribbling effects, something that is necessary to ensure smokeless engine operation.
During the injection process itself, optimum atomisation is particularly important. Very fine spray-hole intake geometries ensure a small droplet size distribution with a high spray impingement. This ensures optimum combustion with good volumetric efficiency and low fuel consumption. In addition, the even droplet size distribution in the engine combustion chamber prevents localized low excess air ratios, thus reducing the level of air pollutants. For many decades, our conventional fuel injection valves have undergone permanent further development relating to these key parameters. This results in high standards in terms of functional behaviour, wear and service life.
We have also developed multifunctional valve systems based on this product family which allow our customers to supply several types of fuel to the combustion chambers of their engines in parallel, under optimised conditions for each. These valve systems are based on multi-needle nozzles and offer maximum flexibility for engine operation.
As exhaust legislation has progressed along with the necessary combustion development, our customers are increasingly calling for independently adjustable injection rates with individually adjustable opening and closing flanks and a freely controllable injection duration independent of pressure levels. Here Woodward L'Orange made use of the electronic common-rail (CR) concept, which then became known throughout the world, in a series system for off-highway engines for the first time in 1997.
Two CR generations have been developed to date for diesel engines as well as for HFO engines. In the first generation, the fuel is stored in what has become the classic rail, and in the second generation, the accumulator is found in the injector, which is capable of even more stable multiple injections. A pre-injection reduces a too quick increase of pressure in the combustion chamber, thus reducing the engine’s component wear. Through a post-injection, shortly following the main injection, the soot resulting from the combustion is burned, so that the engine can run smoke-free at all load levels. Additionally, the integrated volume in the injector levels out any pressure peaks, so that in spite of higher system pressure in the injection system, equal or lower component wear occurs. With this combination of high system pressures and stable multiple injections, it is possible with the latest generation of CR systems to reduce fuel consumption along with nitrogen oxide and particle emissions.