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In the present paper, a new methodology for the estimation of the mass delivered by a single hole of a GDI injector is presented and discussed. The GDI injector used for the activity featured a five-hole nozzle characterized by three holes with the same diameter and two holes with a larger diameter. The different holes size guarantees a significant difference in terms of mass flow. This new methodology is based on global momentum flux measurement of each single plume and on its combination with the global mass measurement made with the gravimetric principle. The momentum flux is measured by means of a dedicated test bench that detects the impact force of the single spray plume at different distances. The sensing device is moved in different positions and, in each point, the force trace averaged over several injection events is acquired. The global mass delivered by the injector is measured by collecting and weighing the fuel flown during a defined number of consecutive injections.

One of the favored automotive exhaust aftertreatment solutions used for nitrogen oxides (NOx) emissions reductions is referred to as Selective Catalytic Reduction (SCR), which comprises a catalyst that facilitates the reactions of ammonia (NH3) with the exhaust nitrogen oxides (NOx). It is customary with these systems to generate the NH3 by injecting a liquid aqueous urea solution (AUS-32) into the exhaust. The urea solution is injected into the exhaust and transformed to NH3 by various mechanisms for the SCR reactions. Understanding the spray performance of the AUS-32 injector is critical to proper optimization of the SCR injection system. Results were previously presented from imaging of an AUS-32 injector spray under hot exhaust conditions at the injector spray exit for an exhaust injection application.

The recent implementation of new rounds of stringent nitrogen oxides (NOx) emissions reduction legislation in Europe and North America is driving the expanded use of exhaust aftertreatment systems, including those that treat NOx under the high-oxygen conditions typical of lean-burn engines. One of the favored aftertreatment solutions is referred to as Selective Catalytic Reduction (SCR), which comprises a catalyst that facilitates the reactions of ammonia (NH3) with the exhaust nitrogen oxides (NOx). It is customary with these systems to generate the NH3 by injecting a liquid aqueous urea solution, typically at a 32% concentration of urea (CO(NH2)2). The solution is referred to as AUS-32, and is also known under its commercial name of AdBlue® in Europe, and DEF - Diesel Exhaust Fluid - in the USA. The urea solution is injected into the exhaust and transformed to NH3 by various mechanisms for the SCR reactions.