Predictive NOx emission control of a diesel-HEV for CO2 and urea consumption reduction

open5noThis activity has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 724095 – ADVICE and the intellectual property of this work belongs to Alma Automotive s.r.l.In recent years, researchers and manufacturers have increased their interest on predictive control strategies for light-duty vehicles, based on electronic horizon availability. Despite this involvement, the on-board implementation of predictive features is still limited in modern automotive control systems. This paper deals with the development of a predictive NOx emissions control function for a diesel hybrid electric vehicle, equipped with an electrically heated after-treatment system composed by a Diesel Oxidation Catalyst (DOC), a Diesel Particulate Filter (DPF), and a Selective Catalytic Reactor (SCR). Such function makes use of an a-priori-known vehicle speed trajectory that would be made available by the electronic horizon provider, and it presents two main sections. The first one predicts the aftertreatment system temperature and the NOx emissions both at the engine out and at the tailpipe over the prediction horizon. The second section defines the powertrain and after-treatment control policy, with the objective of minimizing after-treatment electric heating energy and SCR urea consumption, while respecting the legal NOx limits for the given mission. Furthermore, if the estimated pollutant production exceeds the limits even if the aftertreatment system is operated in the highest efficiency conditions, the predictive control function redefines the torque demanded to the internal combustion engine (and the one requested to the electric motor) to match the legal limits. In terms of results, this novel approach to emissions control shows the benefits coming from the usage of predictive information in combination with powertrain hybridization, and it can be applied to any HEV configuration.embargoed_20201217Caramia G.; Cavina N.; Moro D.; Patassa S.; Solieri L.Caramia G.; Cavina N.; Moro D.; Patassa S.; Solieri L

Low thrust chemical rocket technology

An on-going technology program to improve the performance of low thrust chemical rockets for spacecraft on-board propulsion applications is reviewed. Improved performance and lifetime is sought by the development of new predictive tools to understand the combustion and flow physics, introduction of high temperature materials and improved component designs to optimize performance, and use of higher performance propellants. Improved predictive technology is sought through the comparison of both local and global predictions with experimental data. Predictions are based on both the RPLUS Navier-Stokes code with finite rate kinetics and the JANNAF methodology. Data were obtained with laser-based diagnostics along with global performance measurements. Results indicate that the modeling of the injector and the combustion process needs improvement in these codes and flow visualization with a technique such as 2-D laser induced fluorescence (LIF) would aid in resolving issues of flow symmetry and shear layer combustion processes. High temperature material fabrication processes are under development and small rockets are being designed, fabricated, and tested using these new materials. Rhenium coated with iridium for oxidation protection was produced by the Chemical Vapor Deposition (CVD) process and enabled an 800 K increase in rocket operating temperature. Performance gains with this material in rockets using Earth storable propellants (nitrogen tetroxide and monomethylhydrazine or hydrazine) were obtained through component redesign to eliminate fuel film cooling and its associated combustion inefficiency while managing head end thermal soakback. Material interdiffusion and oxidation characteristics indicated that the requisite lifetimes of tens of hours were available for thruster applications. Rockets were designed, fabricated, and tested with thrusts of 22, 62, 440 and 550 N. Performance improvements of 10 to 20 seconds specific impulse were demonstrated. Higher performance propellants were evaluated: Space storable propellants, including liquid oxygen (LOX) as the oxidizer with nitrogen hydrides or hydrocarbon as fuels. Specifically, a LOX/hydrazine engine was designed, fabricated, and shown to have a 95 pct theoretical c-star which translates into a projected vacuum specific impulse of 345 seconds at an area ratio of 204:1. Further performance improvment can be obtained by the use of LOX/hydrogen propellants, especially for manned spacecraft applications, and specific designs must be developed and advanced through flight qualification