Optical and Energetic Investigation of an Advanced Corona Ignition System in a Pressure-Based Calorimeter

Abstract

In recent years, radio-frequency corona igniters have been extensively studied for their capability to ensure an effective ignition also in lean or diluted mixtures. Corona ignition is volumetric, with streamers coming from a star-shaped electrode. During the discharge, many radicals and excited species, able to speed up the combustion onset, are generated. At the same time, corona igniters are able to release a considerable amount of thermal energy inside the combustion chamber. The correct determination of such energy is crucial to evaluate the effectiveness of the ignition. In this work, corona discharge is experimentally evaluated inside an optical vessel. In this apparatus, the released thermal energy is measured by means of pressure-based calorimetry, and at the same time the natural luminosity of the streamers is recorded with a high-speed camera. The goal is to find a relationship between thermal energy release and streamers luminosity. Tests are performed using nitrogen as medium, at different pressure levels inside the vessel. The peak electrode voltage is varied to characterize the igniter behaviour in different operating conditions. The results of this work can be used to quantify the corona ignition capabilities to involve a wide amount of medium while releasing a high amount of thermal energy. A repeatability evaluation of streamer evolution is investigated as well.

Detecting the Flame Front Evolution in Spark-Ignition Engine under Lean Condition Using the Mask R-CNN Approach

“…Corona behavior is controlled by managing two setting parameters: duration (t on ) and driving voltage (V d ) [53,54]. The first one represents the activation time of the igniters and plays an important role in reducing the cycle-to-cycle variability [55]. The second one, proportional to the electrode voltage [49], is responsible for the corona development around the igniter copula.…”

Thermal Energy and Luminosity Characterization of an Advanced Ignition System Using a Non-Intrusive Methodology in an Optically Accessible Calorimeter

“…A sensitivity campaign was preliminarily realized on the filter type (median, gaussian or no filter at all) and filter order to determine the best setting. Gaussian filter with σ value equal to 1 belongs to a typical range that ensures effective Gaussian filtering [47] and, for this work, it was found to be a good compromise between noise cancellation and boundary conservation. This step allows artifacts and occasional spare pixels to be excluded, which could wrongly influence the final results.…”