DIGITAL FEED-FORWARD CONTROL OF GAS MIXTURE WITH HIGH-SPEED VALVE SWITCHING

To address a need for digital gas mixture control, this paper presents a valve design for digital gas flow rate control without a feedback measurement. This design uses a transonic nozzle to regulate a constant flow rate with partial pressure recovery and a pulse-width modulation scheme to actuate flow rate without needing precise location of a throttle body. Experimental results from a prototype are presented showing linear variation of flow with respect to duty cycle and switching frequency consistent with the valve's theory of operation. Outliers are especially prominant as frequency is varied, and are believed to be due to acoustic effects in the supply line.