Turbomachinery is used in a very wide variety of industries and applications. While applications like aerospace ‘jet engines’ or powerplant steam turbines are the applications that come to mind for a lot of people, turbomachinery is integrated with or buried in a huge range of other equipment, and often transparent to the user. I give a talk to local middle school sciences classes on what turbomachinery is, and give a quiz at the end of the talk where I ask them to list every piece of turbomachinery in their home. The students have surprised me with their understanding and reasoning ability, and I now have a list of 20 to 30 examples of turbomachinery running in their homes.
Medical devices are an area where turbomachinery is often used, but sometimes is not visible or recognized as turbomachinery. While some of these applications use small positive displacement type pumps, as opposed to classic turbomachinery (using a rotating bladed impeller, for example), there are hundreds of applications that rely on classic turbomachinery. Heart pumps are one example where it’s a bit more obvious – a centrifugal or axial pump can be used in this application as an assist heart pump or a main heart pump, and indeed we have been involved with several projects to design or modify heart pumps using either centrifugal or axial turbomachinery. There are other medical devices where the turbomachinery is buried and not as obvious. One of the more interesting medical devices we worked on was an artificial lung, which used turbomachinery related principles to pump the blood in a mass-exchange device which oxygenated blood.
Another class of medical device that uses turbomachinery, that we have all read about extensively lately due to COVID19, are ventilators, respirators, and other types of medial blowers, all of which can use turbomachinery to move or pressurized air. Another specific example of a medical device which can use turbomachinery is a CPAP (continuous positive airway pressure) blower used to treat sleep apnea. We recently performed the design of such a blower for an advanced version of this type of medical equipment.
What is unique about designing turbomachinery for the medical industry? When it comes down to basic aerodynamic or hydraulic design goals, not much. Typical design considerations such as good performance (high efficiency and wide range) often apply to medical device design, especially when the device is battery powered and long run time is critical. Material choice is often an important design choice, to avoid interaction with and contamination of the fluids being pumped or compressed. Noise level is typically a concern for medical applications, so first principles in low noise turbomachinery design are always applicable. Aside from these typical and general turbomachinery design considerations, there are sometimes unique considerations for medical applications. For instance, in blood pumps damage to the blood cells due to high shear stress or even blood coagulation/thrombosis in any areas of recirculation or low velocity are of concern, so the turbomachinery design must focus on avoiding these concerns. But design issues such as this are not totally unique to medical devices – Concepts NREC has designed industrial/chemical pumps that operate with liquids that can harden if not in motion, so areas of recirculation must be avoided in these industrial applications too. Indeed one of the more interesting aspects of our work is seeing crossover in design technology in unexpected places.
Our design software, and engineering design practices, are all very well suited to design turbomachinery for application to medical devices. If you have a need to design pumps, blowers, compressors, or even turbines for use in any medical device, consider giving us a call for a demonstration of design practices and design software for your specific medical application.
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