A Fuel Quality Sensor for Fuel Cell Vehicles, Natural Gas Vehicles, and Variable Gaseous Fuel Vehicles

There are many possible applications for the discrete acoustic wave and phase detection (DAWPD) sound speed sensor. The DAWPD sensor is a compact sensor that measures the sound speed of gases. The sound speed of gaseous fuels can be related to various properties of a fuel including composition. A sound speed sensor can be used as a fuel quality sensor in natural gas vehicles (NGVs), variable gaseous fuel (VGF) vehicles (a VGF vehicle uses a mixture of hydrogen and natural gas fuel), and proton exchange membrane (PEM) fuel cell vehicles (FCVs). In a NGV the DAWPD sensor can be used to measure the methane number, Wobbe number, and hydrogen-to-carbon ratio of the natural gas. The DAWPD sensor can also be used to find the composition of the fuel used in VGF vehicles. In PEM fuel cell vehicles small amounts of CO (>25 ppm) can poison the fuel cell. The DAWPD sensor can measure the amount of CO in the hydrogen fuel in order to control the fuel reforming process. For all three applications the DAWPD sensor can be used in conjunction with a feed-forward control system to optimize the performance of the vehicles. This paper presents the theory relating the sound speed of gaseous fuels to the property of interest for each powertrain. Experimental results are presented for measurements of nitrogen/methane mixtures (representative of natural gas) and methane/hydrogen mixtures as used in NGV and VGF vehicles, respectively. The experimental results show that the DAWPD sensor has adequate accuracy for use in NGV and VGF vehicles. Theoretical results show that the DAWPD sensor also has adequate accuracy for PEM FCVs.