A single-cylinder four-stroke engine equipped with variable valve actuating system was used to study the characteristics of combustion and pressure oscillation in different combustion modes

including homogeneous charge compression ignition（HCCI)

gasoline compression ignition（GCI)

turbulent jet ignition（TJI) and spark ignition（SI). Results show that different combustion modes have different statistical characteristics. Among them

the knock distribution in HCCI

GCI and TJI modes is relatively concentrated

rarely accompanied by occasional high knock intensity combustion cycles. But in SI mode

the knock distribution is relatively discrete

usually with higher maximum knock intensity and 99% quantile

as well as strong occasional high knock intensity combustion cycles

and also shows a very high maximum knock intensity and a very low 99% quantile under low-speed pre-ignition conditions. Moreover

in terms of the evaluation of knock conditions

based on the improvement of the traditional arithmetic average method and the knock cycle occupancy method

two new knock evaluation methods

the weighted average method and the destructive cyclic average method are proposed

so that the accuracy and adaptability of knock determination in HCCI

GCI

TJI and SI modes are greatly improved than before the improvement. But the use of destructive cyclic average method cannot accurately identify the destructiveness of knocking under low-speed pre-ignition conditions

while the weighted average method still has a very good effect.