High Speed Video Measurements of a Heated Tip Urea Injector Spray 2012-01-1747
The recent implementation of new rounds of stringent nitrogen
oxides (NOx) emissions reduction legislation in Europe
and North America is driving the introduction of new automotive
exhaust aftertreatment systems.
One of these technologies comprises a catalyst that facilitates
the reactions of ammonia (NH₃) with the exhaust nitrogen oxides
(NOx) to produce nitrogen (N₂) and water (H₂O). This
technology is referred to as Selective Catalytic Reduction (SCR).
The ammonia is delivered by a separate fluid supply and injection
system to the exhaust in the form of AUS-32 (Aqueous Urea
Solution), and is also known under its commercial name of AdBlue®
in Europe, and DEF - Diesel Exhaust Fluid - in the USA.
The development and application of current production AUS-32
injection systems typically rely on spray diagnostics techniques
that were implemented for the gasoline port injector. These data
are often obtained under standard room temperature conditions.
These data are then used as initial conditions for Computational
Fluid Dynamics (CFD) simulations.
Up until the present, there had been only limited information
about urea injector spray quality as the fluid temperature in the
injector increased to typical hot levels in the exhaust-mount urea
injection applications. This paper presents results from high-speed
video imaging of an AUS-32 injector spray simulating the hot
conditions at the injector spray exit for an exhaust injection
The results show substantial structural differences in the
static spray between room temperature conditions, and conditions
where the fluid temperature is approaching and exceeding 100°C.
There are also noticeable differences in the post injection phase,
which are typically not taken into account by the CFD community,
but which could have a significant impact on mixing calculations
and prediction of deposits behavior.
The high-speed video imaging setup and results for various spray
configurations are described in this paper. The implications for
better understanding of spray-gas mixing and deposits formation are