Part 39 - Impeller blade outlet angle. Forward curved and Backward curved vanes

Summary

This video explains the impact of impeller blade outlet angles in centrifugal compressors and pumps. It discusses how these blades transform mechanical energy into pressure by imparting kinetic energy to the gas. The impeller beta angle is explored, including differences between forward and backward curved veins. Forward veins typically consume more power, whereas backward veins are more efficient and non-overloading, making them better suited for high-pressure applications. The video also highlights the relationship between power demand and discharge flow, with backward curved veins outperforming forward curved ones in efficiency and noise reduction.

Takeaways

• 😀 Impeller blade outlet angle (beta angle) plays a crucial role in centrifugal compressors and pumps, affecting fluid flow and efficiency.
• 😀 The impeller beta angle is the angle between the fluid flow direction and the tangent to the impeller blade at its outlet.
• 😀 Forward curved veins have a blade outlet angle greater than 90°, while backward curved veins have a blade outlet angle smaller than 90°.
• 😀 The 'head' in a compressor or pump refers to the pressure increase the system generates as it compresses the fluid or gas.
• 😀 High head compressors are capable of generating greater pressure differentials, making them suitable for applications requiring higher pressures.
• 😀 Forward curved veins generally consume more power compared to backward curved veins in compressors and pumps.
• 😀 Backward curved veins perform better in terms of efficiency due to lower power demand at a wider flow range.
• 😀 Backward inclined impeller veins have a non-overloading nature, as they do not overload the motor due to changes in static pressure.
• 😀 The power demand for backward curved veins increases more gradually with increasing flow, whereas forward curved veins see a more significant power increase.
• 😀 Backward curved veins tend to have higher efficiency and lower noise compared to forward curved veins.
• 😀 The relationship between impeller blade outlet angle, power demand, and flow is critical for understanding the overall performance of compressors and pumps.

Q & A

What is the impeller blade outlet angle?

The impeller blade outlet angle, also known as the impeller beta angle, refers to the angle between the direction of the fluid flow and the tangent to the impeller blade at its outlet.

How does the impeller blade outlet angle affect the compressor's performance?

The impeller blade outlet angle influences the efficiency and power demand of the compressor or pump. A larger outlet angle (forward-curved blades) may increase the pressure but tends to consume more power, while a smaller outlet angle (backward-curved blades) typically results in better efficiency with lower power demand.

What is the difference between forward-curved and backward-curved impeller veins?

Forward-curved veins have a blade outlet angle larger than 90°, while backward-curved veins have a blade outlet angle smaller than 90°. Forward-curved veins tend to generate higher pressure but consume more power, while backward-curved veins are more efficient and consume less power.

What does the term 'head' refer to in a compressor or pump?

In a compressor or pump, 'head' refers to the pressure head, which is the pressure developed by the compressor. It represents the amount of pressure increase that the compressor can generate as it compresses gas or fluid.

Why is a high head compressor or pump suitable for applications requiring higher pressures?

A high head compressor or pump is capable of generating a greater pressure differential, which makes it suitable for applications that require higher pressures.

Why might one initially think that forward-curved veins are better than backward-curved veins?

At first glance, one might think that forward-curved veins are better than backward-curved veins because they typically generate higher pressure. However, forward-curved veins consume more power and are less efficient.

How does the power demand compare between forward-curved and backward-curved impellers?

Backward-curved impellers typically require less power and achieve peak power consumption earlier in their flow range. In contrast, forward-curved impellers require increasing power as the flow increases, making them less efficient overall.

What does it mean that backward-curved veins are 'non-overloading'?

Backward-curved veins are considered 'non-overloading' because changes in static pressure do not lead to an overload of the motor, making them more stable during operation.

What are the key advantages of backward-curved impellers over forward-curved impellers?

Backward-curved impellers offer higher efficiency, lower power consumption, and reduced noise. They also achieve optimal power consumption early in their flow range, making them more efficient than forward-curved impellers.

How does the efficiency of backward-curved veins compare to forward-curved veins?

Backward-curved veins generally have higher efficiency compared to forward-curved veins, especially at lower flow rates, and produce less noise, making them more suitable for many applications.