Enrico Corti

Automatic Combustion Phase Calibration With Extremum Seeking Approach

One of the most effective factors influencing performance, efficiency, and pollutant emissions of internal combustion engines is the combustion phasing: in gasoline engines electronic control units (ECUs) manage the spark advance (SA) in order to set the optimal combustion phase. Combustion control is assuming a crucial role in reducing engine tailpipe emissions and maximizing performance. The number of actuations influencing the combustion is increasing, and as a consequence, the calibration of control parameters is becoming challenging. One of the most effective factors influencing performance and efficiency is the combustion phasing: for gasoline engines, control variables such as SA, air-to-fuel ratio (AFR), variable valve timing (VVT), and exhaust gas recirculation (EGR) are mostly used to set the combustion phasing. The optimal control setting can be chosen according to a target function (cost or merit function), taking into account performance indicators, such as indicated mean effective pressure (IMEP), brake-specific fuel consumption (BSFC), pollutant emissions, or other indexes inherent to reliability issues, such as exhaust gas temperature or knock intensity. Many different approaches can be used to reach the best calibration settings: design of experiment (DOE) is a common option when many parameters influence the results, but other methodologies are in use: some of them are based on the knowledge of the controlled system behavior by means of models that are identified during the calibration process. The paper proposes the use of a different concept, based on the extremum seeking approach. The main idea consists in changing the values of each control parameter at the same time, identifying its effect on the monitored target function, and allowing to shift automatically the control setting towards the optimum solution throughout the calibration procedure. An original technique for the recognition of control parameters variations effect on the target function is introduced, based on spectral analysis. The methodology has been applied to data referring to different engines and operating conditions, using IMEP, exhaust temperature, and knock intensity for the definition of the target function and using SA and AFR as control variables. The approach proved to be efficient in reaching the optimum control setting, showing that the optimal setting can be achieved rapidly and consistently.

Remote Combustion Sensing Methodology for Non-Intrusive Cylinder Pressure Estimation in Diesel Engines

Abstract The pollutant emission reduction requested by future pollutant emission policies spawned a great deal of research in the field of combustion monitoring and closed-loop control. This is especially true for Diesel engine, since an important reduction in NOx and particular matter will be required. Many works demonstrate that a major engine-out emission reduction can be achieved through a closed-loop combustion control methodology based on cylinder pressure trace processing. However, the main obstacles to the use of cylinder pressure sensors for on-board application are measurement reliability over time and cost. Therefore, this paper describes the development of a methodology that allows estimating cylinder pressure through a proper combination of the information coming from low-cost sensors mounted on the engine.

Numerical Simulation of the Zefiro 9 Performance Using a New Dynamic SRM Ballistic Simulator

This work describes the application of a new three-dimensional ballistic model, named ROBOOST (ROcket BOOst Simulation Tool), developed at the Laboratory Propulsion and Mechanics of the University of Bologna (Department of Industrial Engineering), to the Vega Zefiro 9 Solid Rocket Motor, manufactured by the Avio company in Colleferro (Rome). The code uses an original graphical approach and a point-by-point description of the propellant burning surface regression. The main purpose of the newly developed model is to investigate non homogeneous behaviors of the surface regression rate or non-isotropic characteristics of the grain. A zero-dimensional unsteady thermo-dynamic model, coupled with a mono-dimensional quasi-steady one, computes the internal fluid-dynamics of the combustion chamber and contributions by igniter, nozzle erosion and thermal protections ablation are also considered. Comparisons with reference curves and experimental data, in terms of volume and surface regression and mean pressure time evolution, have been performed and final results are presented and discussed.