The railway transportation industry has numerous applications for cooling fans. Although fans are fundamentally selected on the basis of volumetric air flow, static pressure and size, numerous other factors must be considered for railway applications. This article reviews some of the applications for cooling fans for railways and provides an overview of some of the criteria used in the selection of these fans.

With the numerous types, performance characteristics and fan sizes available, the fan selection process can be complicated and cumbersome, potentially leading to the selection of non-optimal systems. To address this problem, Rosenberg, a worldwide leader in the design, development and manufacturing of fans for a variety of applications, has created the RoVent10 software. This software can assist users in the selection of fan types and their performance characteristics and provide them with pertinent design information and specifications to simplify the cooling system design process. This article also highlights Rosenberg’s new, more powerful Generation 3 EC fan motor, which was selected as a finalist in the AHR 2020 Innovation Awards.

Railway fan applications

Railways have numerous requirements for cooling, including the driver’s cab and passenger compartment, the propulsion and braking systems, and onboard power systems and components. In the driver’s cab and passenger compartment, comfort and climate control are a top priority, requiring low noise yet high capacity fans to gather and distribute conditioned air throughout these areas. Cooling of the propulsion and braking systems is of utmost importance for passenger safety, as overheating of these elements can compromise system performance and lead to potentially catastrophic component failure. Onboard power systems and electronic components require cooling to ensure reliable and efficient operation.

With the greater reliance on railway transportation, it becomes increasingly important to ensure the reliable and efficient operation of railway system cooling fans. These fans must be capable of operating continuously in harsh environments over long periods of time. Unplanned system maintenance and repair can result in excessive system downtime, late schedules, customer aggravation and loss of revenue. Railway fans must also be compact and have low weight, as additional vehicle weight and volume reduces efficiency and can reduce the payload weight or number of passengers that the train can carry. They also must operate quietly and have high air-moving capacity to ensure passenger comfort.

Rosenberg fans can provide the required cooling capacity, low acoustical noise and ability to operate in harsh environments with corrosion protection. Furthermore, the worldwide availability of cooling components ensures high reliability, maintainability, modularity and supply of parts.

Types and configurations of fans

A variety of different fans in different configurations can be used in railway transportation applications, including axial fans, centrifugal fans and backward curved motorized impellers. An overview of the different types of fans that can be used in the above railway applications, including their principles of operation, is provided below.

Axial fans

Figure 1. Axial fan. Source: RosenbergAxial fans have blades that rotate around an axis that is parallel to the air flow (Figure 1). They are designed to produce a pressure differential between the front of the fan and the back, which causes air to flow through the fan. The performance and efficiency of axial fans is determined by the number, shape and angle of attack of the fan blades as well as the fan’s rotational speed. Among the advantages of axial fans are high efficiency, low noise and lower input power requirements compared with other fan types. While axial fans create airflow with high flow rates, the airflows have low pressure.

Centrifugal fans

Figure 2. Centrifugal fan. Source: RosenbergCentrifugal fans move air in a direction perpendicular to the axis of a fan wheel, which consists of a series of blades mounted on a circular hub (Figure 2). The incoming air enters through the center of the circular hub and is propelled outward in a radial direction by the fan blades. When compared to axial fans, centrifugal fans can develop higher pressure airflows, although at lower volumetric flow rates and because of the high number of blades, they do not have tonal noise peaks. Centrifugal fans are ideal for noise sensitive applications

Backward curved motorized impellers

Figure 3. Backward curved motorized impeller. Source: RosenbergBackward curved motorized impellers typically have between five and nine large blades curved away from the direction of rotation (Figure 4). When the fan rotates, a positive pressure is created on the leading (convex) side of the blade, which pushes the air outward in the radial direction. On the trailing (concave) side of the blade, a negative pressure is created, drawing the air into the space between the fan blades. This air is then picked up by the leading side of the trailing blade and forced outward in the radial direction. While axial and centrifugal fans have optimum regions on the fan curve where the highest efficiency is achieved, backward curved motorized impellers can be operated anywhere on the curve. This enables a high degree of flexibility and adaptability for the fan and allows it to be used across a wide range of applications.

Fan selection process

The selection of a fan for a particular railway application requires consideration of numerous technical challenges related to the equipment being cooled, packaging and operational constraints and environmental conditions. The type of equipment, including size, heat generation capability, duty cycle and operating temperature limits, is usually the prime consideration in the selection of a fan. However, the choice may be limited by packaging constraints, such as the fan location, maximum size and orientation. Operational constraints can further limit fan selection, and include such items as the maximum power available, maintainability and reliability. Environmental conditions, such as temperature extremes, operation in wet or humid environments, and the presence of harsh or corrosive chemicals and materials may further limit fan selection to the equipment designed and tested in these environments to ensure safe and reliable operation. Careful consideration must therefore be given to these technical challenges to properly select a fan with the appropriate size, speed, pressure, volumetric air flow rate, reliability and cost.

Rosenberg has simplified the fan selection and cooling system design process by creating the RoVent10 software, which is available for download to their customers. RoVent10 can automatically guide users to quickly select among more than 2,900 fan models by simply entering the type of fan and basic design constraints, such as power and motor type, and performance criteria, such as the pressure and volumetric flow rate. RoVent10 then provides a family of performance curves of several fans that satisfy the design and basic performance criteria (Figure 4). The user can select a fan that operates at peak efficiency, including accessories, such as sensors, controllers and other electronic modules that are compatible with the fan. RoVent10 also provides all the necessary documentation including drawings, solid models (if available), specifications, bills of materials, operating manuals, wiring diagrams and pricing information. This information can then be used to ensure that the fan can be properly packaged within the cooling system, and that all requirements and specifications are satisfied. The unique and advanced capabilities of RoVent10 greatly simplify the fan selection and cooling system design process.

Figure 4. RoVent10 fan curves. Source: Rosenberg

Generation 3 EC fan motor

Figure 5. Generation 3 EC motor. Source: RosenbergAs a leader in technology and innovation, Rosenberg recently introduced their Generation 3 electronically commutated (EC) fan motor, which was a finalist in the AHR 2020 Innovation Awards competition (Figure 5). EC motors are DC brushless motors that are controlled by an external electronic circuit board, which provides greater power, more precise control and higher efficiency. In fact, the new Generation 3 EC motor is 30% more powerful than the Generation 2 EC motor, offering users more sophisticated air movement for mission critical applications. Other advantages include the use of advanced ModBus RTU functionality, built-in preventive maintenance and reliability features (integrated inspection LED, electronic quick-change capability, IT network support) and increased failure safety.

The Generation 3 EC fan motor drives are used to drive axial fans and backward curved impellers in environments where power, reliability and control are critical. Advanced manufacturing technology enables 40% more motor winding density creating 20% to 30% increased power in the same footprint. Built-in sophisticated electronics are used for communication, control and greater reliability. These motors are 100% speed controllable and are CE, UL-R and RoHS approved.

Rosenberg overview

Rosenberg has been a worldwide leader in the development and manufacture of speed controllable external rotor motors, fans and air handling units since 1981. Headquartered in Künzelsau, Germany, engineering skills drive the company’s innovation and form the basis of their development and manufacturing work. Additionally, 70% of their products are exported worldwide, and the company is represented by 1,500 employees and 45 sales offices in Europe, Asia, North and South America, and Australia. Their diverse customer base includes the energy, railway, renewables, automotive, healthcare, industrial and building industries. More information about the company and their products is available on the Rosenberg website.