​Introduction to Parallel Operation Characteristics of Multi-Blade Fans

Introduction to Parallel Operation Characteristics of Multi-Blade FansWhen two or more multi-blade fans draw air from the same suction pipe or suction chamber and simultaneously deliver air to a common duct, this configuration is termed a parallel connection of multi-blade fans. In practice, during parallel operation of two multi-blade fans, the impact on parallel performance varies regardless of whether the models are identical. The following analysis explains this phenomenon. First, if two parallel multi-wing fans share the same equipment model, the performance characteristics of the fans after parallel connection can be obtained using graphical methods to derive the parallel characteristic curve of centrifugal pumps. Analysis indicates that the air volume and pressure of the system increase after parallelization. However, after parallel connection, the air intake of each multi-wing fan unit is less than when a single fan is operating. Nevertheless, when two identical multi-wing fans are connected in parallel in this manner, the air pressure of each fan increases compared to operating a single fan. After connecting two identical multi-wing fans in parallel, it is observed that the total airflow is not double that of a single fan operating independently, but less than double. The airflow after parallel connection does not reach the level of a single fan. Note that when two identical centrifugal fans are connected in parallel, the actual increase in airflow often directly affects the steepness of the duct system characteristic curve. Generally, systems with steeper duct characteristic curves—meaning higher impedance—experience smaller airflow increases after parallel connection. Conversely, systems with flatter curves yield larger airflow gains. Therefore, using parallel connection to increase airflow must be applied in systems with low duct resistance. Failure to do so may render parallel connection economically inefficient. In other scenarios, two different types of multi-wing fans are connected in parallel. For example, a large fan and a small fan are connected in parallel. At this point, it is impossible for the small centrifugal fan to operate without supplying any gas. The gas merely circulates back and forth within the fan, generating heat, while only the multi-wing fan is actually conveying gas within the system.