Wavesurfer angular25/16/2023 ![]() ![]() ![]() ![]() For all operating tested points, the air-fuel ratio was changed by fixing the throttle position in order to maintain the same turbulence level inside the chamber. Starting from this air/fuel value, a comparison between the results obtained at different operating loads was carried out. In this latter case, the lean stable limit was found to be λ = 1.6 for the CSI and λ = 1.55 for the BDI both higher than the one obtained with a conventional spark (λ = 1.4). Tests were performed at 1000 rpm at medium load (from now on ML), starting from the results obtained in low-load (from now on LL). As already found in our previous work, the optimal IT of the CSI is closer to the TDC than the BDI one because of the faster flame development showed off in the first part of the combustion by the corona-streamer type. Therefore, upon setting the IT, if the 1% threshold was exceeded, the test point was discarded and then repeated with lower V D. The ACIS ECU features an arc-detection algorithm that counts and stores the number of arc events. All of the quantities were acquired by a fast oscilloscope (Teledyne LeCroy Wavesurfer 3000) with a sampling frequency of 10 MHz, about ten-times bigger than the frequency of the current ( Figure 3). bar −1 of sensitivity and ≈10 −5 bar of resolution) recorded the pressure fluctuations inside the chamber due to the discharge events and an Amplifier (Kistler Type 5011) converted the charge transmitted by the pressure sensor into a proportional voltage signal.A piezoelectric pressure transducer (Kistler Type 7261, 2200 pC Concerning the experimental apparatus, each discharge event was triggered by means of a TTL signal produced by an arbitrary wave generator (HP 33120A) and the current supply to the igniter coil was recorded by a current probe (Teledyne LeCroy CP030, accuracy ☑.5% full scale). ![]() The corona devices were tested on a plexiglass constant volume vessel (V c = 22.5 cm 3) able to ensure low thermal conductibility (0.187 Wm −1K −1), using air as medium at steady-state conditions, without charge motions. The target was to give an estimation of the thermal energy released during the discharge and then to compare their capability to provide high-stability energy. The corona igniters were tested on a constant volume calorimeter as well, reproducing the engine pressure conditions at the corresponding ignition timing. For each operating point, the devices’ control parameters were set to ensure maximum energy releasement into the medium with the aim of investigating, at the extreme operating conditions, the capability of the devices to extend the lean stable limit of the engine. In this work two corona igniters, namely a Barrier Discharge Igniter and a Corona Streamer Igniter, were tested in a single-cylinder research engine fueled with gasoline at different engine loads in order to investigate the igniters’ performance through indicated analysis and pollutant emissions analysis. Kinetic, thermal, and ionic effects, together with the peculiar configuration of the devices, allow the combustion process to start in a wider region than the one involved with the traditional spark. These igniters are able to extend the lean stable limit by increasing the early flame growth speed. Currently, the Radio-Frequency Corona Ignition systems represent an important solution for reducing pollutant emissions and fuel consumption related to Internal Combustion Engines, while at the same time ensuring high performance. ![]()
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