The Birman Turbocharger:What happened to it?

[Conslaw]

The XF4U-3 and XF6F-2 were equipped with an experimental Birmann turbocharger. Apparently sn experimental F4U with the Birman. turbocharger hit 480 mph at 40,000 feet. What was unique about the Birman turbocharger? Did this turbocharger ever see success in any installation? What happened to Birman and his turbochargers after the war?

 

[ThomasP]

AFIK, the primary difference from the standard turbocharger was that the Birman was a 'mixed flow' type - it used both centrifugal and axial flow compressor components. I believe the basic idea became fairly common in some types of superchargers/turbochargers after the war, but I do not know how similar the designs that saw service were to the original Birman design.

The only advantage that I am aware of is that some of the air from the centrifugal compressor component is directed into the turbine stage of the turbocharger in order to cool the turbine. This can give a significant increase in mechanical efficiency/pressure ratio of the turbocharger and/or service life of the turbine components.

This method is used in many modern diesel applications (particularly 2-stroke types) due to the high temperatures of the exhaust gases used for driving the turbine. It has been applied to gasoline engines as well, but I do not know how common it is in everyday automotive or aircraft turbochargers.

Incidentally, the basic concept is used in some (many? most?) current aircraft turbine engines - in low-high bypass designs for sure, not sure about non-bypass type turbojets.