Date of Graduation
Statler College of Engineering and Mineral Resources
Mechanical and Aerospace Engineering
Marc Cyrill Besch
Exhaust gas flow rate from a vehicle tailpipe has a great influence on emission mass rate calculations, as the emission fractions of individual gases in the exhaust are calculated by using the measured exhaust flow rate. The development of high-end sensor technologies and emission pollutant measurement instruments, which can give instantaneous values of volume concentration of pollutants flowing out of the engine are gaining importance because of their ease of operation. The volume concentrations measured can then be used with the instantaneous exhaust flow rate values to obtain mass flow rates of pollutants.
With the recent promulgation of real world driving (RDE) emissions, it is of significance to gain a real-time measurement or estimation of fuel consumption and mass emission numbers for the tailpipe constituents. Adhering to the packaging complexity and cost involved in affixing the vehicles with accurate flow meters, the methodologies to predict the same using existing vehicle infrastructure has been constantly evolving and investigated. Towards realizing such an effort, the present work is directed towards investigating a few improved approaches towards estimating exhaust flow values, including the challenging vehicle operation regimes such as, light load activity and start-stop idle conditions which is prone to fluctuations in the flow behavior. Also, the fact that the exhaust gas flow rate plays a key role in determining actual amounts of mass flow rates of pollutants, provides scope for the development of new methods to estimate exhaust flow rates.
In this report, three different methodologies to estimate the exhaust flow rate from the vehicle tailpipe have been developed and investigated. The estimations were obtained by using the on-board diagnostics (OBD) data collected from the engine control unit (ECU). Mass flow rate of fuel and other parameters necessary to calculate the intake flow rate to the engine, and parameters which can be used directly for estimation of exhaust flow rate, were obtained from the ECU. Based on these values the exhaust gas flowing out of vehicle tailpipe was estimated and corrected.
The estimations made by methodologies under study were found to match the measured exhaust flow, measured using an industry standard Portable Emissions Measurement System (PEMS) exhaust flow device, in its best within 1% along Regional and Port: Local routes and the least accurate estimations were observed to be happening in vehicle activity along Highway route with highest difference of 13.3% respectively. However, the developed methods serve as alternative methodologies, as the exhaust flow rate values are calculated without usage of any additional flow meters and flow sensors, and by just using the ECU data, eventually providing a reliable means to help in calculating the mass flow rates of pollutants flowing out of vehicle tailpipe.
Vardhireddy, Chakradhar Reddy, "Investigation and Development of Exhaust Flow Rate Estimation Methodologies for Heavy-Duty vehicles" (2019). Graduate Theses, Dissertations, and Problem Reports. 7423.