Abstract: An underground ventilation system having a fan, a plurality of ducts for the delivery of air to an underground work space, flow control dampers at duct branches, a fan sensor module to detect velocity, pressure, temperature and/or humidity, a work space sensor in each work space, a connection panel in communication with the fan sensors and with each automated flow control damper and configured to exchange status and control information with the fan sensor, the flow control dampers, and work space sensors, a cabling system attached to the ducts and connected to the connection panel and to automated flow control dampers, and a display and control system in electronic communication with the fan, the fan sensor, the automated flow control dampers, and the work space sensors, via the connection panel.

Abstract: A fan blade that responds to external perturbations in a way that reduces the effect of the perturbations on the blade. The fan blade is designed so that the twist center is forward of the pressure center relative to the air flow direction, and the distance between the twist center and the pressure center is greater than zero. Fan blades having this feature will deform in a way to decrease aerodynamic load when conditions cause an increase in aerodynamic load and conversely increase aerodynamic load when conditions cause a decrease in aerodynamic load.

Abstract: A fan blade that responds to external perturbations in a way that reduces the effect of the perturbations on the blade. The fan blade is designed so that the twist center is forward of the pressure center relative to the air flow direction, and the distance between the twist center and the pressure center is greater than zero. Fan blades having this feature will deform in a way to decrease aerodynamic load when conditions cause an increase in aerodynamic load and conversely increase aerodynamic load when conditions cause a decrease in aerodynamic load.

Abstract: A method for making a fan blade or fan component of composite material including using a permanent core having a plurality of interconnected surface channels over its surface to facilitate resin flow; forming a reinforcing fabric envelope over the permanent core; closing a mold over the reinforcing fabric enveloped permanent core to form a mold cavity between a surface of the permanent core and an interior surface of the closed mold, and infusing a resin into an opening of the closed mold, allowing the resin to fill an entirety of the mold cavity via the permanent core surface channels, allowing said resin to cure, and releasing said fan blade or fan component from the mold; wherein said infusion of resin is accomplished with or without a positive pressure system and wherein said permanent core is not removed from said fan blade or fan component prior to use.

Abstract: A cooling tower fan hub having a ring and a disc in which in which hollows and recesses are opened in the ring and/or in the disc in order to decrease fan natural frequencies and avoid excitation by the several kind of loads that affect a fan during operation. The number, size and shape of the hollows can be adjusted to tune the fan natural frequencies around the original value.

Abstract: A cooling tower fan hub having a ring and a disc in which in which hollows and recesses are opened in the ring and/or in the disc in order to decrease fan natural frequencies and avoid excitation by the several kind of loads that affect a fan during operation. The number, size and shape of the hollows can be adjusted to tune the fan natural frequencies around the original value.