Low Power Piezoelectric Micro Mass Flow Controller for Liquid Fuel Injection

Utilization of an ethanol driven, combustion-based power generator promises high-efficiency combustion in diesel-like engines and avoids problems connected to shrinking supplies of fossil fuels since fuels like ethanol or dimethyl ether can be produced from renewable resources. Fuel injection into such generator through a piezoelectric micro mass flow controller (MMFC) features low power consumption and enables self-sustaining operation: Only a negligible amount of generated power is re-used for injection and combustion control. A micro-machined MMFC with power consumption during steady state operation of 20 muW at 120 V is presented herein. The MMFC, which is designed like a normally-closed, on-/off-operating valve is connected to a pressurized fuel tank for testing and operation. Integrated piezoresistors are used for flow rate feedback control and an implemented pn-diode (sensitivity: -2.5 mV/K) enables on-chip temperature monitoring. Ethanol flow rates of up to 70 mul/s at 100 kPa fuel pressure have been demonstrated.