Abstract
Since 2014, Formula 1 engines have been turbocharged spark-ignited engines. In this scenario, the maximum engine power available in full-load conditions can be achieved only by optimizing combustion phasing within the cycle, i.e., by advancing the center of combustion until the limit established by the occurrence of abnormal combustion. High in-cylinder pressure peaks and the possible occurrence of knocking combustion significantly increase the heat transfer to the walls and might generate hot spots inside the combustion chamber. This work presents a methodology suitable to properly diagnose and control the occurrence of pre-ignition events that emanate from hot spots. The methodology is based on a control-oriented model of the ignition delay, which is compared to the actual ignition delay calculated from the real-time processing of the in-cylinder pressure trace. When the measured ignition delay becomes significantly smaller than that modeled, it means that ignition has been activated by a hot spot instead of the spark plug. In this case, the presented approach, implemented in the electronic control unit (ECU) that manages the whole hybrid power unit, detects a pre-ignition event and corrects the injection pattern to avoid the occurrence of further abnormal combustion.
Highlights
To promote research and development in the field of internal combustion engines, the FederationInternational de l’Automobile (FIA) has recently revised the Formula 1 sporting regulations [1,2].As a result, since 2014, the spark-ignited internal combustion engine (ICE) has been downsized to a 1.6 L engine with a V6 layout
The abnormal combustion processes can be divided into two main mechanisms: end-gas auto-ignition and surface ignition [8]
First level of recovery: If one pre-ignition event is diagnosed in one cylinder, a 5% fuel reduction is applied to the fuel injected into that cylinder; Second level of recovery: When one pre-ignition event is diagnosed and another event has already been diagnosed in the last 50 cycles, a further fuel reduction is applied
Summary
To promote research and development in the field of internal combustion engines, the Federation. Once the occurrence of end-gas knock has been detected, a specific control strategy needs to manage the proper spark advance reductions to avoid the risk of engine damage (retarding the combustion process within the cycle) [14]. Once the pre-igniting cycles have been identified, the controller performs a proper reduction of the injected amount of fuel, the goal being to immediately reduce the temperature of the hot spots and avoid consecutive abnormal combustions. A pre-ignition due to a hot spot can result in increased heat transfer to the piston (increasing the local temperature) and result in end-gas knock in the following cycles For this reason, the controller needs to react immediately after the detection and perform a fuel reduction compatible with the intensity and frequency of the abnormal combustion detected. The discussed approach is methodological and could be applied to standard spark-ignited engines (with different architectures) used in common automotive applications
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