Potential of SI Pre-Chamber Thermal Management

2023

RESEARCH ASSOCIATION FOR COMBUSTION ENGINES EV

INV. COMPETITIVA PROYECTOS

Desantes Fernández José María

In the field of spark-ignition (SI) engines, the pre-chamber (PC) combustion process offers significant efficiency potential compared to current technologies. Therefore, it is currently being intensively researched. Spark ignited PC combustion processes are characterized by a quick conversion of the air-fuel mixture. The heat release rate is getting close to an isochoric combustion of the ideal Otto cycle and thus reduces risks of engine knocking, which allows to increase the compression ratio of the engine. The high energy of the hot and turbulent gas jets allows even lean mixtures to be ignited reliably. All these characteristics create the prerequisite for a high thermal efficiency. A main development focus for pre-chamber spark plugs (PCSP) are additional wall heat losses compared to conventional ignition systems for two reasons. Firstly, the ignition along the highly turbulent hot gas jets near the wall provoke significantly increased heat losses in the main combustion chamber (mainly on the piston). Secondly, a PCSP adds surface area to the cylinder head, resulting in higher wall heat losses to the coolant. Both issues lead to lower efficiency gains than theoretically possible and to combustion instability specially at low loads during cold start. This project will study and combine two innovative measures to address these issues. It involves an active thermal management of a PCSP manufactured by rapid-prototyping processes by using a nucleate boiling cooling circuit and an innovative piston coating. Both measures will be investigated numerically with 3DCFD/ CHT and by experiments on a single cylinder research engine. The active participation of SMEs allows the practical development of the technologies used. Of particular interest are coating and additive manufacturing technologies located in industries in which SMEs are strongly represented. The harsh test conditions grant SMEs empirical values that go far beyond the intended scope of research, enabling systematic improvement of the whole product range. The planned method and the gained knowledge will help to increase thermal efficiency and therefore reduce CO2 emissions for future combustion engines, including applications that cannot be electrified. These engines must use sustainable, but in the short and medium-term limited fuels (e.g., Hydrogen, Methanol, Ammonia), therefore increasing efficiency through the use of a PCSP is a key element in further reducing CO2 emissions. This research project, which will be carried out jointly by Technische Universität Berlin (FZA) and Universitat Politècnica de València (CMT) is to be financed from various sources.