柴油机水下排气海水倒灌现象的理论分析

柴油机水下排气时存在海水由排气管倒灌入柴油机进而导致柴油机严重损坏的风险。通过分析管内气液两相逆向流动特性和国内外相关研究成果,指出水下排气管内海水倒流的物理机制,并给出了基于Wallis无因次气相速度的水下排气管海水倒流判断准则。进而以某柴油机排气参数为基础,计算分析了排气管管径、排气口水位深度及排气温度等因素对管内倒流界限气速的影响,所得结果对水下排气柴油机防止海水倒灌具有指导意义。

Theoretical Analysis of Seawater Backflow Phenomena of a Diesel Engine Using Submerged Exhaust

For a diesel engine using submerged exhaust, there is a risk to damage the diesel engine seriously when seawater flows back into it though the exhaust pipe. Based on the analysis of the characteristics of gas-liquid counter current flow and the review of the relevant study results in literatures, the physic mechanism, as well as a judging criterion using the well-known Wallis parameter, of seawater backflow in an exhaust pipe were proposed in this paper. Then, the effects of the relevant factors such as exhaust pipe diameters, gas vent underwater depths and exhaust temperatures on the critical superficial gas velocity for preventing water backflow were calculated and discussed with the use of the exhaust parameters of a real diesel engine. The results of this paper are instructive to enhance the safe and reliable operation of a diesel engine using the submerged exhaust method.