In Aerospace development and testing, there are frequently occasions where aerodynamicists need to pressurize a large volume (>100 Liters) to high pressures (>150 PSIG). These aerospace applications require both high flow rates, as well as high pressures. For these aerospace pressure control applications, there can be limits on the mass flow that can be achieved while routing gas through the pressure controller.
While it’s simple for an aerodynamicist to pressurize an aerospace device under test (DUT) with an Alicat PCD series pressure controller, restrictions on mass flow can place limitations on the speed with which the tank filling can be accomplished. These restrictions on flow can be due to the construction of the device, but are more commonly due to limitations related to the valve. Very often, the best way to get around this conundrum for aerospace companies is to allow the DUT to pressurize through a high-flow bypass valve, and then use a high-precision pressure controller to perform the requisite pressure maintenance. This method allows for the fastest possible tank filling, coupled with the highest precision pressure control.
A common application is pressurization of a gas reservoir prior to high-speed aerodynamic testing. A customer approached Alicat with this exact type of project: they needed to pressurize a 200 Liter reservoir to 1000 PSIG, upstream of a high-speed wind tunnel. Then, via a rupture disk, they would quickly release the trapped gas into a wind tunnel to produce a high Mach number hypersonic flow.
To pressurize such a large volume quickly requires a high flow / high pressure device. Unfortunately, Alicat’s high flow Rolamite valves only operate at pressures under 500 PSIG. Rather than decline the application, Alicat’s application engineers proposed an alternate idea: pressurize the chamber through a solenoid valve to 980 PSIG, close the valve, and then allow an Alicat PCDH-1000PSIG-D to finish filling the chamber to the exact pressure needed for the test. The PCDH is a specialized pressure controller that utilizes dual side-by-side valves (hammerhead) to achieve control times under 30 ms, even at high pressures. This solution led to a very responsive and more streamlined procedure that enhanced the reproducibility of the customer’s hypersonic wind tunnel experiments, by providing a more consistent flow, and therefore a more consistent windspeed.
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