Measures to improve the performance of scroll air compressor
The backflow from the impeller is accompanied by a large amount of energy loss. If the backflow is properly prevented, the performance improvement of the scroll air compressor can be expected.
In order to prevent the cycle, the push flow device used to prevent the cycle can be set directly in front of the impeller inlet.
However, in this part, the impact loss is large, and the efficiency will be reduced. If a proper static wing or other device is used to replace the rectifier device, the performance of the scroll air compressor, especially the head flow characteristics, will be changed.
This paper describes the method of setting a circular flow reduction plate of appropriate size at the inlet of impeller to prevent reverse flow from making the performance of Fusheng air compressor upward.
The diameter of the shrinkage cavity is divided into seven types, and its head, shaft power and efficiency are calculated for each type.
According to the different output flow, when the contraction is not sufficient, the backflow from the impeller flows into the suction pipe through the contraction hole, which causes the generation of the cycle and the rise of the claw force on the wall.
There is not much difference between the head of the lift and that of the flow without constriction, and the power is saved because of the relationship between the flow with constriction. The value is about 40% of P when the gate is fully closed.
The energy carried by the backflow is about equal. In the best condition, the average flow velocity through the contraction part is equal to the average flow velocity in the suction pipe at the rated flow.
In order to improve the suction performance of the centrifugal scroll air compressor, the method of increasing the pressure by setting an axial-flow impeller in front of the impeller of the scroll air compressor, i.e. an inducer, is adopted. Because this inducer is an impeller, if it is not applied to the flow corresponding to the inducer within the working range of the centrifugal scroll air compressor, it is the same as the main impeller of the scroll air compressor, Impact at the entrance.
Therefore, when the inducer works at a flow rate less than the rated flow rate, the same as the ordinary impeller described before, in the inducer, there will also be backflow of flow work from the inlet to the upstream of the suction pipe.
According to Dadao, if the axial flow impeller (inducer) is adopted, the flow will be reversed at the suction pipe when the flow is less than 1 / 2 of the rated flow. He also assumes that the maximum flow of the centrifugal vortex air compressor (main impeller) is at most within 1.5 times of the rated flow, and the inducer is designed with 3 times of the rated flow as the rated flow of the inducer.
Furthermore, an appropriate size of flow reduction plate is set in front of the inducer, so that the efficiency of the scroll air compressor will not be too low. Compared with the case without flow reduction, it successfully improves the suction performance.
There is no inducer and inducer in front of the main impeller, and then there is a shrinkage plate. For these situations, the effective suction head and suction specific speed are respectively obtained at the suction critical point (this is the point where the field value is reduced by 3% in each flow rate from the field value when cavitation does not occur).