Overcoming the challenges of high-speed aerodynamic tests using pressure control
In aerospace development and testing, aerodynamicists frequently occasions need to pressurize large volumes to high pressures: often volumes of greater than 100 L, pressurized to over 150 PSIG. These aerodynamic tests generally require high flow rates in addition to high pressures. However, there can be limits on the mass flow that can be achieved while routing gas through the pressure controller, most often attributable to the limitations of the valve.
While it’s simple for the aerodynamicist to pressurize a device under test (DUT) using a PCD-Series differential pressure controller, the mass flow limitations will restrict the speed at which the tank can be filled. Often, this challenge is circumvented by pressurizing the DUT through a high-flow bypass valve. Once the DUT is fully pressurized, a high-precision pressure controller is able to perform any necessary pressure maintenance. This method allows for the fastest possible tank filling, coupled with the highest precision pressure control.
Example: gas reservoir pressurization
Gas reservoirs present an example of this application: the reservoir must be pressurized prior to high-speed aerodynamic tests can be conducted. A customer approached Alicat looking to pressurize a 200 L gas reservoir to 1000 PSIG, upstream of a high-speed wind tunnel. The gas held in the reservoir would then be quickly released into a wind tunnel (via a rupture disc), which would produce a hypersonic flow with a high Mach number.
Pressurizing the large volume of the reservoir requires a high flow/high pressure device. However, Alicat’s standard high-flow Rolamite valves are only operable at pressures under 500 PSIG.
Alicat’s application engineers proposed an alternate solution
The reservoir chamber could be pressurizing chamber through a solenoid valve to 980 PSIG. At that point, the valve could be closed and an an Alicat PCDH-1000PSIG pressure controller would finish filling the chamber to the precise pressure needed for the test. The PCDH is a pressure controller specialized past the standard dual-valve pressure controller which we recommend for closed volumes. It utilizes dual, side-by-side valves (hammerhead) to achieve control times under 30 ms, even at high pressures.
This solution led to a highly responsive aerodynamic test process which was more streamlined than the original procedure. Perhaps more importantly, it enhanced the reproducibility of the customer’s hypersonic wind tunnel experiments by providing a more consistent flow – and therefore a more consistent windspeed.