Development of a fuel sensor technology for a Variable-blend Natural Gas Vehicle

Natural gas vehicles (NGVs) with the ability to accept a broader range of fuel specifications can play a significant role in increasing Renewable Natural Gas (RNG) utilization in the transportation sector. The Wobbe Index is a critical factor in evaluating the interchangeability between different high methane fuels. This study details the development and testing of a compact, reliable Wobbe Index sensor for use in NGVs. The concept uses a combination of a thermal conductivity and an infrared sensor together with temperature and pressure measurement. The signals from these sensors are indexed in an algorithm that estimates the Wobbe Index in real time. The sensor was confirmed to operate over a temperature range of -20 degrees C to 70 degrees C under pressures of up to similar to 3600 psi. A multivariate algorithm was developed to estimate the fuel Wobbe Index from the measured temperature, pressure and thermal conductivity data. The accuracy was improved to +/-1% using the CH4 concentration data from the IR sensor additionally. Compared to the existing methods, this sensor provides a cost-effective, ruggedized solution that can be used to develop a "Variable-blend Natural Gas Vehicle"(VNGV), allowing refueling from a broad range of natural gas sources. This technology has the potential to significantly increase RNG usage for transportation purposes. (C) 2016 Elsevier B.V. All rights reserved.