Loccioni Group has developed a automatic test bench that is able to measure the spray momentum of diesel and GDI injectors. The bench is composed of a positioning system that moves, inside the space in a spherical coordinate system, a piezoelectric force sensor with three ranges of 0-2/20/200 N with a linearity of ±1% FS.


Figure: 2 — Positioning system of the force sensor

The system is assembled in a steel vessel that can be pressurized by nitrogen, from

0. 2 bar abs to 80 bar abs, in order to simulate the air density inside the combustion chamber of an internal combustion engine.

The test bench is supplied by a pressure intensifier that can generates a rail pressure from 200 to 2500 bar with a pressure stability of ±0.05% FS in static regulation and ±0.2% FS in dynamic operation. The positioning of the sensor is based on a spherical coordinate system; the Z axis range is from 5 to 80 mm with an accuracy of 0.15 mm, the Phi axis range is from 0° to 90° with an accuracy of

0. 2° and the Theta axis range is from 0° to 360° with an accuracy of 0.2°.

The heart of the system is a piezoelectric force sensor on which two different devices can be mounted, one for the global measurement and one for the local measurement. The first one is a flat disk with a large diameter (greater than 10 mm) that deflects all of the spray, the second device is composed of a conical screen and a pin with a diameter of 1 mm; the conical element has hole in the centre into which the pin is inserted. The pin is in contact with the sensor and, during the spray impingement, it transmits the force to the sensor. Moving this device with a sensitive area of 0.78 mm2 inside the spray the system is able to represent the spray momentum distribution.


Figure: 3 — Devices for global (left) and local (right) spray momentum measurement

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