Diesel exhaust fluid delivery system with pressure control

A diesel exhaust fluid delivery system and a dual-variable control strategy for adjusting the delivery pressure and the mass flow rate of the fluid passing through the sy stem. The method for operating the system using two operating modes: low flow rate and high flow rate. While operating in the low flow rate operating mode, the speed of a DEF pump remains constant and DEF delivery to the exhaust system is adjusted by controlling a backflow valve. While operating in the high flowr rate operating mode, the backflow valve is closed and the speed of the pump is adjusted to regulate DEF delivery to the exhaust system. 种柴油机尾气处理液输送系统和用于调整通过所述系统的流体的输送压力和质量流率的双变量控制策略。用于操作所述系统的方法使用两种操作模式：低流率和高流率。当以低流率操作模式操作时，DEF泵的速度保持恒定并且通过控制回流阀来调整向排气系统的DEF输送。当以高流率操作模式操作时，回流阀被关闭并且调整泵的速度以调节向排气系统的DEF输送。