A Methodology for the hydraulic characterization of a Urea-Water Solution injector by means of Spray Momentum Measurement
Raul Payri  1@  , Gabriela Bracho  1, *@  , Jaime Gimeno  1@  , Armando Moreno  1@  
1 : Universitat Politecnica de Valencia
Camino de Vera, s/n46022 Valencia -  Spain
* : Corresponding author

Selective Catalytic Reduction (SCR) is a technology that allows the internal combustion engines to comply with the stringent regulations set for exhaust gasses, specifically Nitrous Oxides (NOx) emissions. For a proper operation of the SCR, a urea-water solution (UWS) injector must dose an adequate amount of liquid into the exhaust pipe in order to avoid deposit formation that can compromise the engine and SCR system efficiency. This task requires the knowledge of the performance of the injector. Then, the goal of this work is to study the hydraulic performance of a Urea-Water Solution injector, by means of measuring the spray momentum flux, in order to understand the influence of different variables as injection pressure and temperature on the flow characteristics. The tested injector was cooled at different temperatures ranging from 20° to 90° C and the injection pressure of the urea-water solution was set at 4, 6 and 8 bar for each measured temperature during the tests. The measurements were carried out using an experimental facility developed at CMT-Motores Térmicos for the determination of the UWS Spray Momentum flux, where a piezo-electric pressure sensor was located near the nozzle exit of the injector, which measures the impact force of the spray. Additionally, mass flow rate measurements of the injector were performed under the same operating conditions, determining the influence of the injection pressure and the cooling temperature. Regarding the pressure, the tendency was as expected, the higher the injection pressure the higher the flow rate. On the other hand, when the temperature was increased the mass flow was slightly reduced. Additionally, the proposed methodology allowed to determine the injected mass flow, capturing the transient events of the injection, such as the opening and closing stages.

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