The Selective Catalytic Reduction (SCR) technology allows the transformation of the Nitrous Oxide emissions present in exhaust gases into gaseous nitrogen and water. 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 and to guarantee the 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 UWS injector, by means of measuring the spray momentum flux in order to understand the influence of different variables as injected fluid, injection pressure, counter pressure and cooling temperature of the injector on the flow characteristics. The tested injector was cooled at three different temperatures, 60, 90 and 120 °C, the injection pressure of the UWS was set at 5, 7 and 9 bar, with counter pressures of 750, 900, 1000 and 2000 mbar for the two tested fluids, water and UWS. The measurements were carried out using an experimental facility developed at CMT-Motores Térmicos for the determination of spray momentum flux, where a piezoelectric pressure sensor was located near the nozzle exit of the injector, which measures the impact force of the spray. Additionally, the proposed methodology allowed to determine the injected mass flow and to capture the transient injection events, such as the opening and closing stages. Moreover, mass flow rate measurements of the injector were performed under the same operating conditions, determining the influence of the injection pressure, cooling temperature, counter pressure and fluid properties. Regarding the pressure, the tendency was as expected, the higher the injection pressure the higher the Momentum flux and flow rate. Results showed that an increment of the cooling temperature of the injector induces the appearance of flash boiling conditions, having an impact on the total injected mass and momentum flux, changing the behaviour of the spray. For the same conditions, water has a higher momentum flux than the UWS due to differences in fluid properties and velocity at the nozzle exit.

选择性催化还原 (SCR) 技术允许将废气中的一氧化二氮排放物转化为气态氮和水。为了使 SCR 正常运行，尿素水溶液 (UWS) 喷射器必须将足够量的液体注入排气管，以避免形成沉积物并保证 SCR 系统效率。此任务需要了解喷油器的性能。然后，这项工作的目标是通过测量喷雾动量通量来研究 UWS 喷射器的水力性能，以了解喷射器的喷射流体、喷射压力、背压和冷却温度等不同变量的影响。关于流动特性。测试的喷油器在三种不同的温度下冷却，60、90 和 120 °C，UWS 的注入压力设置为 5、7 和 9 bar，两种测试流体（水和 UWS）的背压分别为 750、900、1000 和 2000 毫巴。测量是使用 CMT-Motores Térmicos 开发的用于确定喷雾动量通量的实验设备进行的，其中压电压力传感器位于喷射器的喷嘴出口附近，用于测量喷雾的冲击力。此外，所提出的方法允许确定注入的质量流量并捕获瞬态注入事件，例如打开和关闭阶段。此外，喷射器的质量流量测量是在相同的操作条件下进行的，以确定喷射压力、冷却温度、反压力和流体特性的影响。关于压力，趋势正如预期的那样，注射压力越高，动量通量和流速就越高。结果表明，喷射器冷却温度的增加会引起闪沸条件的出现，从而影响喷射的总质量和动量通量，改变喷雾的行为。对于相同的条件，由于喷嘴出口处流体性质和速度的差异，水具有比 UWS 更高的动量通量。