An Oxygen Balance Method: Fuel Consumption Measurement for Fuel Cell Vehicles based on Exhaust Emissions with No Vehicle Modification

For the measurement of fuel consumption of fuel cell vehicles (FCV), ISO 23828 and SAE J2572 standards recommend three methods, the gravimetric, pressure and flow methods. These methods can measure with a high accuracy and have proven its practicability in the fuel economy test, but require the test vehicle to be modified to supply hydrogen from an external, rather than the on-board fuel tank. As these vehicle modifications necessitate technical assistance of the vehicle manufacturer, a simpler no-modification method such as the carbon balance method for gasoline- and diesel-fuelled vehicles is desired. Therefore, the authors have developed new method using only FCV exhaust emissions. This paper describes the principles behind the new method as well as test equipment and results, influence factors in error and issues. As a result, its real-time fuel consumption measurement characteristics were improved by reducing the volume of the gas sampling system and by correcting the time lag in oxygen concentration analysis. Error of the new method was from -3% to +1% as compared with the flow method for the fuel cell system operating in JC08 test cycle.