Experimental investigation on the failures of engine piston subjected to severe knock 2019-01-0705
The previous study indicates that the detonation waves generated by acetylene / oxygen mixture can converge in the combustion chamber. In order to verify the destructive effect of detonation wave convergence on piston materials, the detonation bomb device was modified to fundamentally investigate the material failures of aluminum alloy for pistons. The combustion chamber of the detonation bomb retains the essential features of the engine cone-roof combustion chamber. The test specimen made of aluminum alloy for real pistons acts as a piston to bear the detonation load. The results show that the specimens are destroyed in the middle and edge region after dozens of detonations, which is consistent with the typical characteristics of the piston failures in real engines. Therefore, the hypothesis that failures of piston material is caused by the detonation wave convergence is verified. The pressure measured at the cylinder head position is much less than that of the middle and edge region of the piston. The in-cylinder pressure signal at the cylinder head position can’t give a clear explanation of the damage mechanism of pistons. The detonation wave has the most destructive force when the convergence condition is most suitable. Compared with the hard aluminum alloy and the forged aluminum alloy, the eutectic aluminum alloy generally used for the piston of engines has the lowest strength to resist the detonation load.
Jian Gao, Anren Yao, Luyu Feng, Han Xu, Chunde Yao