XPrize Vehicle 100mpge City-Highway Math Model Electric-Hybrid Vehicles

摘要

XPrize Vehicle Foundation guidelines include two vehicle categories: 'mainstream' and 'alternative'. 'Mainstream' four-wheel vehicles carry four-passengers and have 200mile range. 'Alternative' vehicles have no minimum wheel requirement, carry two or more passengers and require a 100mile range. However, both categories have the same fuel economy and emission requirements e.g., 100mpge (miles per gallon equivalent) or greater. A math model was developed to determine theoretical ideal mpge (assuming 100% o/a system drive line efficiency) and ideal maximum miles range given EPA FTP city/highway driving schedules. This study shows road load traction force is a function of driving schedule and specific vehicle design parameters, e.g., driving schedule acceleration cycles, vehicle test mass, tire rolling resistance drag coefficient, aerodynamic drag coefficient, equivalent flat plate frontal area and vehicle velocity. Overall power train system mechanical and electrical component losses are assumed to be ideal 100% efficient. Based on this math model and FTP city/hwy driving schedules sixteen commercially available battery electric and hybrid vehicles were evaluated to establish a reference baseline. Given vehicle EPA fuel economy label mpge ratings and this math model ideal mpge values, practical o/a mean effective mechanical-electrical system power train efficiency was found to be about 55% for electric and hybrid propulsion systems. Modest budget high school and amateur XPrize vehicle teams do not have access to wind tunnel nor EPA chassis dynamometer test facilities. This math model offers an effective method to estimate ideal mpge, ideal range, propulsion energy distribution: e.g, tire, aerodynamic, acceleration, regenerative braking energy recovery, for XPrize vehicle designs prior to competition.