The fuel injector nozzle is critical to the performance and emissions of diesel engines. Some of the important injector nozzle parameters—including details of the injector seat, the injector sac and nozzle hole size and geometry—affect the combustion characteristics of the diesel engine, as well as the stability of the emissions and performance over the lifetime of the engine and the mechanical durability of the injector.
In some cases the actual pump may be sealed and immersed inside the fuel tanks on a site, in which case it is known as a submersible pump. In general, submersible solutions in Europe are installed in hotter countries, where suction pumps may have problems overcoming cavitation with warm fuels or when the distance from tank to pump is longer than a suction pump can manage.
In some countries, pumps are able to mix two fuel products together before dispensing; this is referred to as blending or mixing. Typical usages are in a “mix” pump to add oil to petrol for two-stroke motorcycles, to produce an intermediate octane rating from separate high and low octane fuels, or to blend hydrogen and compressed natural gas (HCNG). The benefit of blending for retailers is that it allows them to offer 3 grades of fuel while only having to maintain inventory of two grades. This frees up both working capital and tank capacity and improves fuel turnover.
Typically, individual pumps must be certified for operation after installation by a government weights and measures inspector, who tests that the pump displays the same amount that it dispenses. Measurement Canada is the federal agency responsible for pump regulations in Canada and stickers are displayed on the pumps.
An effort to standardize this in the 1990s resulted in the International Forecourt Standards Forum, which has had considerable success in Europe, but has less presence elsewhere. (“Forecourt” refers to the land area on which the fuel dispensers are located.)
The nozzles are usually color-coded to indicate which grade of fuel they dispense, however the color-coding differs between countries or even retailers. For example, a black hose and handle in the UK indicate that the fuel dispensed is diesel, and a green dispenser indicates unleaded fuel; the reverse is common.
All nozzles must produce a fuel spray that meets the requirements of the performance and emissions goals of the market for which the engine is produced regardless of details of the fuel system design (i.e., regardless if the fuel system is of the common rail, unit injector, unit pump or pump-line-nozzle type). Additionally, specific requirements for injection nozzles can also depend on the fuel system type :
