Is the injection speed related to any certain factors?

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This post was last edited by ztj1118 on 2016-1-21 at 21:22. At the same rotational speed, the injection timing affects the effective length of the flow discharge channel; as a result, it influences the injection pressure and injection rate characteristics of the electronic control system. The variation characteristics of the nozzle tip pressure and fuel injection rate of plunger group 1# at 650 r/min as a function of fuel injection timing (T represents the fuel injection timing angle; an increase in T indicates earlier fuel injection). The injection timing is advanced, the effective length of the flow discharge channel increases, the initial low injection rate phase widens, the initial rate of increase in injection rate is slow, and a boot-shaped injection rate profile can be formed throughout the entire injection period. 　　As the injection timing is delayed, the width of the initial injection rate range gradually decreases, while the amplitude of the initial injection rate gradually increases. The injection timing is further delayed; by the time the control valve closes, the flow discharge path has risen entirely above the fuel inlet hole, rendering it ineffective for flow control. At this point, the injection rate characteristics are determined by the fuel supply characteristics of the oil pump. As the rotational speed changes, the aforementioned pattern also changes accordingly. Rotational speed and fuel injection rate: 1. Suppression and utilization of the pre-injection effect. After a drain channel is installed on the plunger, the flow rate of fuel supplied by the pump decreases during the initial stage of fuel supply, due to the draining effect of this channel. When the injection timing is advanced, within the range where the drain channel has an effect, the pressure wave generated at the pump end from the start of fuel supply until the control valve closes is somewhat suppressed. This pressure wave influences the magnitude of the initial pressure wave that propagates toward the nozzle when the valve closes; only at high speeds can this initial pressure wave reach the nozzle and cause pre-injection. When the plunger does not have a flow relief groove, the initial pressure wave is relatively large, allowing pre-injection to occur at lower rotational speeds; at higher speeds, the pre-injection effect is stronger and the fuel injection rate is higher, which does not meet the requirements for controlling the fuel injection rate. 　　2. Size of the drain groove and range of boot-shaped injection rates The size of the drain groove affects the initial fuel supply rate of the plunger, and thus also influences the speed range at which the boot-shaped injection rate is achieved. Tests have shown that when the discharge area of the flow discharge channel is small, a lower rotational speed is required to achieve a boot-shaped fuel injection pattern; to obtain such a pattern at high speeds, it is necessary to increase the discharge area of the channel and to appropriately lengthen its length as well.