New OEM Cummins 3095773 Fuel Injector For Cummins engine KTA38 KTA50 QSK19 QSK38 QSK50

Modelling the High-speed Injector for Diesel ICE （part 3）

The following components may be referred to the structural features of the injector: Spring 5, multiplier, needle 7. The needle spring for the injector operation is mandatory and shall be installed around the multiplier to prevent the valve from reopening due to pressure waves when resetting. The closing multiplier increases the closing force acting on the needle. Unlike pressure-driven closing when the pressure is applied to the full area of the needle, this design allows for a large range of closing forces with the same pressure change.

The inertia of the multiplier slightly impairs the system response. Also, the multiplier forms a precision pair with the case and increases the dimensions. Its main purpose is that increasing the ratio of the multiplier diameter to the diameter of the needle makes the process more controllable, accurate, and shorter. When fuel is injected, the multiplier, with its upper end, tends to close the axial orifice leading to the ball valve 4. It may not be fully realized, since high pressure is restored through the jet and the multiplier is force up to the orifice. However, there is a real benefit from this equilibrium stabilization process: fuel flow for control becomes limited (from the battery through the jet, valve to drain). The multiplier is a needle extension with a spring. From the point of view of the operating speed, it is an increase of the moving mass. The need to use the multiplier is stipulated by its suitability for a wide range of operating pressures.

The needle closing multiplier results increasing the closing force with the same pressure acting in the control chamber and, thus, accelerating the the needle closing. Even considering the weighting of the mass moving with the needle, the operating speed increases. The EHI is unserviceable for a highspeed diesel if the closing multiplier is omitted. Even if it is possible to ensure its operability, the delivery stability is low with respect to the wave processes, process deviations, etc.