Effects of different hole structures of pre-chamber with turbulent jet ignition on the flame propagation and lean combustion performance of a single-cylinder engine

•A multi-hole structure with different apertures of pre-chamber is proposed.•The effects of active pre-chamber structures on flame propagation characteristics with gasoline fuel.•The apertures of 3 mm and 4 mm are more suitable for the TJI combustion in the present test engine.•A proper jet hole structure can increase the combustion rate, reduce fuel consumption and emissions. Turbulent jet ignition is an advanced pre-chamber approach for improving combustion rates and extending lean burn limitations. The hot flows jetted from the pre-chamber through jet hole act as a distributed ignition source, igniting the mixture in the main chamber. In this paper, the effects of structures on flame propagation and engine performance are systematically studied based on an optical constant volume combustion chamber and a single cylinder engine. Firstly, the visualization of the effects of pre-chamber hole apertures and jet hole numbers on flame propagation is realized. Then, the effects of pre-chamber hole structures on engine performance are studied. The results show that small jet hole aperture could lead to flame quenching while too large aperture may cause low flame speed, both of which will decrease combustion rates. Moreover, the disturbance zone formed by cold jet flow could help maintain the jet flame speed induced by hot jet. Meanwhile, adopting multi jet hole structure could improve combustion in main chamber while modifying jet hole structure considering combustion chamber of real engine helps to achieve lower fuel consumption and emissions. TJI engine has great potential for achieving low fuel consumption and low NOx emissions without severe engine knock when the excess air coefficient ranges from 1.4 to 1.7.