1) The calculation model analysis of the excavator multi-way valve rotary joint spool moves to the right by 4mm into the oil inlet and the median return oil.The excavator multi-way valve rotary joint spool moves to the right by 4mm model boundary condition setting: set the inlet speed to 10.04m / s, the outlet pressure is 0MPa, that is, the rotary motor is empty. The turbulence intensity is 10%, and the inlet and outlet hydraulic diameters are 00073m and 0012m, respectively.
(1) Static pressure distribution diagram 42 shows the static pressure cloud diagram of the original excavator multi-way valve rotary coupling spool shifted to the right by 4mm axial section (unit:
MPa; hereinafter referred to as the original right-shifted 4mm static pressure cloud diagram) From the figure a, we can know that its inlet pressure reaches 2MPa. After passing through the variable U-shaped throttling groove, the pressure loss totals 22MPa; After the throttle groove, the pressure loss is 22MPa.This is because there is a vortex field in the upper part of the throttle groove, and a negative pressure is locally formed, which causes the generation of cavitation and greatly affects the performance of the valve: from the c diagram, we can know that the pressure oil passes through the oil return After the U-shaped throttle groove, the pressure loss is 2MPa. The negative pressure generated locally is relatively small, but at this time the return flow area is larger than the inlet flow area, so the pressure loss is smaller than the inlet U-shaped throttle. It is known from the figures b) and c) that the pressure loss is mainly at the joint surface of the orifice and the inner cavity of the main spool. The pressure gradient at the inlet is large and the pressure gradient at the outlet is small.
Figure 4-3 shows the static pressure cloud diagram (unit: MPa; hereinafter referred to as the new right-shift 4mm static pressure cloud diagram) of the new excavator multi-way valve rotary coupling spool shifted to the right by 4mm axial section.
From the figure a), we can know that the inlet pressure reaches 1MPa after passing through the variable U-shaped throttle, the total pressure loss is lPa: from b), we can know that after the pressure oil passes through the inlet U-shaped throttle, the pressure loss is IMPa, This is because there is a vortex field in the upper part of the throttle groove, and a negative pressure is locally formed, thereby causing the generation of cavitation, which greatly affects the performance of the valve; from the c) figure, we can know that after the pressure oil passes through the return U-shaped throttle groove, the pressure Loss of IMPa. The negative pressure generated locally is small, but at this time the overflow area is larger than the oil inlet overflow area, so the pressure loss is smaller than the oil inlet U-shaped throttle. It is known from the figures b) and c) that the pressure loss is mainly at the joint surface of the orifice and the inner cavity of the main spool. The pressure gradient at the inlet is large and the pressure gradient at the outlet is small.
(2) Velocity distribution
Figure 44 shows the velocity cloud diagram of the original excavator multi-way valve rotary coupling spool shifted to the right by 4mm axial section (unit: s; hereinafter referred to as the original right shifted 4mm velocity cloud diagram)
It can be known from the diagram a) that the inlet speed is 10ms (the full speed grade is not shown in the bar chart) .When the oil passes through the minimum of the variable U-shaped throttle groove, the speed can reach 240ms: from the diagram b) the pressure oil passes After entering the U-shaped throttling groove, the speed rapidly increased from 40m / s to 240m, which caused a local temperature rise. It can also be seen from the graph of c) that after the pressure oil passes through the return U-shaped throttle groove, the speed rises rapidly from 20m / s to 240m / s, which produces a local temperature rise, and the area of the high-speed oil area is larger than the oil inlet state. From the graphs b) and c), it is known that the velocity is mainly generated at the minimum flow area of the throttle groove, which is also consistent with the flow continuity equation, indicating the correctness of the flow field analysis. The local high speed leads to a local temperature rise of the oil, which oxidizes the oil and causes local thermal expansion and deformation of the valve body, resulting in stuck valves.
Figure 45 shows the velocity cloud diagram of the new excavator multi-way valve rotary coupling spool to the right 4mm axial section (unit m / s; hereinafter referred to as the new right shift 4mm velocity cloud)
It can be known from the diagram a) that the inlet speed is 10ms. When the oil passes through the minimum of the variable U-shaped throttle groove, the speed can reach 100m / s; from the diagram b), it can be known that the pressure oil passes through the inlet U-shaped throttle groove , The speed rises rapidly from 40ms to 160ms to produce local temperature rise. It can also be seen from the graph of c) that after the pressure oil passes through the return U-shaped throttle groove, the speed rises rapidly from 30ms to 160ms to produce a local temperature rise, and the area of the high-speed oil area is smaller than the oil inlet state. From the graphs b) and c), it is known that the velocity is mainly generated at the minimum flow area of the throttle groove, which is also consistent with the flow continuity equation, indicating the correctness of the flow field analysis. The local high speed leads to a local temperature rise of the oil, which oxidizes the oil and causes local thermal expansion and deformation of the valve body, resulting in stuck valves.
