1 一阶与二阶不平衡力矩发动机不平衡旋转及其往复质量将产生一阶与二阶不平衡力矩。(图1)。这意味着不平衡力矩分别以等于发动机转速或二倍于发动机转速的频率周期性地变动着。因为这些不平衡力矩相当大,在某些不利的情况下它们可能会激起船体振动。但必须指出4缸机的一阶不平衡力矩的大小仅约为二阶不平衡力矩之半。 1 first-order and second-order unbalanced torque Unbalanced rotation of the engine and its reciprocating mass will produce first-order and second-order unbalanced moments. (figure 1). This means that the unbalanced torque periodically fluctuates at a frequency equal to or twice the engine speed, respectively. Because of these considerable unbalance moments, they may in some adverse circumstances excite the hull vibration. However, it must be pointed out that the size of the first-order unbalanced torque of the 4-cylinder machine is only about half that of the second-order unbalanced torque.