Tennessee Wastewater Operator Practice Exam

How is the discharge pressure of a multistage centrifugal blower increased?

1. By reducing the inlet pressure

2. By adding stages to the blower

3. By increasing the motor size

4. By using a larger impeller

The correct answer is: By adding stages to the blower

In a multistage centrifugal blower, increasing the discharge pressure is primarily achieved by adding more stages to the blower. Each stage consists of an impeller and a diffuser; as air or gas passes through each stage, it receives an additional boost in pressure due to the increase in kinetic energy imparted by the impeller and the subsequent conversion of this kinetic energy into pressure energy in the diffuser. More stages allow the blower to achieve a higher total pressure by effectively multiplying the pressure increase across each impeller stage. This design helps in applications requiring higher pressure outputs than what a single-stage blower can provide. While other factors, such as motor size and impeller size, may influence performance, they are not the primary method for achieving increased discharge pressure specifically in a multistage system. Increasing motor size can enhance overall performance but doesn’t directly influence the pressure increase mechanism in the stages themselves. Similarly, using a larger impeller can improve flow rate and efficiency, but again, it does not replace the basic principle of pressure enhancement provided by multiple stages.