Introduction to Commonly Used Stainless Steel Centrifugal Fans

Introduction to Commonly Used Stainless Steel Centrifugal FansStainless steel centrifugal fans are mechanical devices capable of discharging a certain volume of gas at a specific pressure. Common stainless steel centrifugal fans are categorized based on the pressure they generate: - Low-pressure models typically operate below 10 kPa; - Medium-pressure models range from 10 to 300 kPa; - High-pressure compressors exceed 300 kPa; - Ultra-high-pressure compressors surpass 10 MPa. This classification is not strictly defined. Sometimes centrifugal fans are also called blowers. Those that generate negative pressure and exhaust cold air are called air pumps or vacuum pumps. Centrifugal fans with pressures not exceeding 10 kPa are classified as low-pressure fans, defined as having pressures below 981 Pa [100 mm1-1201]. Medium-pressure stainless steel centrifugal fans operate at pressures between 981 Pa and 2943 Pa. High-pressure stainless steel centrifugal fans exceed 2943 Pa. The principle of centrifugal stainless steel centrifugal fans involves using a rotating impeller to propel gas particles, generating centrifugal force. This increases both the gas's pressure energy and kinetic energy. The sum of these is termed the fan's total static pressure. As the stainless steel centrifugal fan impeller rotates, gas disperses outward under centrifugal force. This causes the gas near the shaft center to become rarefied. Consequently, air is continuously drawn in through the fan inlet to replenish the air supply. To facilitate the smooth entry of air expelled by the impeller into the exhaust duct, the casing is often designed as a spiral chamber, known as a volute. The outlet is a circular diffuser. The gas velocity decreases within the diffuser, converting part of the kinetic energy into pressure energy. As gas flows through the fan, mechanical energy is transferred to the gas particles due to the pushing action of the rotating blades, increasing both kinetic and pressure energy. When pressure energy increases, specific volume decreases, density increases, and the degree of temperature drop also increases. In low- and medium-pressure stainless steel centrifugal fans, the gas compressibility can be neglected since the pressure increase through the fan is minimal. However, this compressibility must be considered in high-pressure stainless steel centrifugal fans. The average values at the inlet and outlet can be used to calculate gas density. The blades of centrifugal stainless steel fans are categorized as forward-curved, radial, or backward-curved. See Figure 5.12: Fan with forward-curved and radial blades. As airflow increases, the fan's power consumption N rises sharply, potentially causing motor overload. Curved-disc fan. When airflow 2 increases, n rises slowly before showing a downward trend. To prevent excessive motor overload, centrifugal stainless steel fans should be started at low airflow f, i.e., when the damper is fully closed.