Technical Information of Impeller:

Impellers can be classified into three types based on the curvature of their blades: backward-curved blades (a), radial blades (b), and forward-curved blades (c). The fundamental difference among these three blade types lies in the direction of curvature at the blade outlet. Blades curved in the same direction as the impeller rotation are called forward-curved blades; those curved opposite to the rotation direction are backward-curved blades; and blades with the outlet direction aligned with the impeller diameter are radial blades.

For impellers with these three different blade curvatures, under the same peripheral velocity and airflow relative velocity conditions, backward-curved blade impellers have relatively small outlet absolute velocity and its peripheral component. Forward-curved blade impellers exhibit larger outlet absolute velocity and its peripheral component, while radial blade impellers fall between backward-curved and forward-curved types.

However, in terms of overall compressor stage efficiency, under the same impeller peripheral velocity and blade outlet airflow relative velocity conditions, the outlet absolute velocity of forward-curved blades is significantly higher than that of backward-curved blades. For compressor stages with forward-curved blades, pressure rise largely relies on the high impeller outlet velocity being decelerated and diffused in stationary components. Yet, during the diffusion process in stationary components, flow losses are substantial, especially at high impeller peripheral velocities where high Mach numbers can lead to significant flow losses, reducing overall stage efficiency.

For backward-curved blades, due to the low airflow velocity at the impeller outlet, stage pressure rise is primarily achieved through centrifugal force within the rotating impeller and flow diffusion inside the impeller. Experimental data indicate relatively low flow losses during the pressurization process within the impeller. Therefore, for compressor stages with backward-curved blades, stage pressure rise mainly occurs in the impeller with minimal flow losses. The airflow outlet velocity is much lower than that of forward-curved blades, significantly reducing flow losses in stationary components. Thus, from an efficiency perspective, backward-curved blade impellers are more likely to achieve higher stage efficiency.

For impellers, increasing peripheral velocity is an effective way to achieve the highest possible stage pressure ratio. However, due to strength constraints of the shroud, peripheral velocity is limited, with closed impellers generally operating below 320 m/s. To maximize stage pressure ratio, impellers without a shroud, known as semi-open impellers (a), can be used. This design is advantageous from a strength perspective, allowing peripheral velocities of 450–500 m/s. However, in terms of stage efficiency, direct friction between airflow in the impeller passage and stationary walls, as well as leakage through gaps between blades and stationary walls, results in lower efficiency compared to closed impellers.

To accommodate large-flow compressor stages, impellers can also be designed with a double-entry configuration (b). This design not only suits high-flow stages but also offers the advantage of self-balancing axial forces. However, it presents drawbacks in terms of manufacturing complexity and structural intricacy.To accommodate large-flow compressor stages, impellers can also be designed with a double-entry configuration (b). This design not only suits high-flow stages but also offers the advantage of self-balancing axial forces. However, it presents drawbacks in terms of manufacturing complexity and structural intricacy.

Packaging of Impeller: 

Shanghai Metal Products are packed and labeled according to the regulations and customer's requests. Great care is taken to avoid any damage which might be caused during storage or transportation. In addition, clear labels are tagged on the outside of the packages for easy identification of the product I. D. and quality information.

1) Shanghai Metal Standard

2) Customization