﻿ 柴油机水下排气红外抑制仿真研究
 舰船科学技术  2019, Vol. 41 Issue (2): 89-92 PDF

Simulation of the infrared signature suppression of diesel exhaust under water
TANG Si-mi, XU Fei, CHEN Zhong-wei
Academy of Naval Research, Beijing 100161, China
Abstract: Based on the submarine infrared stealth, study on the method to control the infrared signature when the diesel exhaust under water. The model of two-phase flow was built, and a two-level temperature reduction scheme was proposed. The first, the water was projected in the vent-pipe of diesel. The second, applying the pore pipe to increase the mix of exhaust and water. The performance of infrared signature suppression was proved by simulation. The results show that the excellent performance of infrared signature suppression was proved, the temperature of exhaust was reduction greatly on the sea surface based on the method of two-level temperature reduction, the significance of the measure for infrared suppression was proved.
Key words: diesel     exhaust under water     infrared signature suppression     simulation
0 引　言

1 柴油机水下排气降温模型 1.1 Realizable k-ε湍流模型

 $\frac{{\partial \rho }}{{\partial t}} + \frac{\partial }{{\partial {x_i}}}\left( {\rho {u_i}} \right) = 0{\text{，}}$ (1)

 $\begin{split} & \frac{\partial }{\partial t}\left( \rho {{u}_{i}} \right)+\frac{\partial }{\partial {{x}_{j}}}\left( \rho {{u}_{i}}{{u}_{j}} \right)=-\frac{\partial P}{\partial {{x}_{j}}}+\\ & \frac{\partial }{\partial {{x}_{j}}}\left[ \mu \left( \frac{\partial {{u}_{i}}}{\partial {{x}_{j}}}+\frac{\partial {{u}_{j}}}{\partial {{x}_{i}}}-\frac{2}{3}{{\delta }_{ij}}\frac{\partial {{u}_{l}}}{\partial {{x}_{l}}} \right) \right]+\frac{\partial }{\partial {{x}_{j}}}\left( -\rho u_{_{i}}^{'}u_{_{j}}^{'} \right) \end{split}{\text{，}}$ (2)

 $\frac{\partial }{{\partial t}}\!\left( \!{\rho E} \!\right) \!+\! \frac{\partial }{{\partial {x_j}}}\!\left[\! {{u_i}\left( \!{\rho E \!\!+\!\! p} \!\right)} \!\right] \!\!=\!\! \frac{\partial }{{\partial {x_j}}}\!\left(\! {{k_{eff}}\!\frac{{\partial T}}{{\partial {x_j}}} \!+\! {u_i}{{\left(\! {{\tau _{ij}}}\! \right)}_{e\!\!f\!\!f}}} \!\right) \!\!+\!\! {S\!_h}\!{\text{，}}$ (3)

 $\begin{split} &\frac{\partial }{{\partial t}}\left( {\rho \kappa } \right) + \frac{\partial }{{\partial {x_i}}}\left( {\rho \kappa {u_i}} \right) = \frac{\partial }{{\partial {x_j}}}\left[ {\left( {\mu + \frac{{{\mu _k}}}{{{\sigma _k}}}} \right)\frac{{\partial k}}{{\partial {x_j}}}} \right]b +\\ & Gk + G - \rho \varepsilon - {Y_m} + {S_k}{\text{，}} \end{split}$ (4)

 $\begin{split} & \frac{\partial }{{\partial t}}\left( {\rho \varepsilon } \right) + \frac{\partial }{{\partial {x_i}}}\left( {\rho \varepsilon {u_i}} \right) = \frac{\partial }{{\partial {x_j}}}\left[ {\left( {\mu + \frac{{{\mu _\varepsilon }}}{{{\sigma _\varepsilon }}}} \right)\frac{{\partial \varepsilon }}{{\partial {x_j}}}} \right] + \rho {C_1}S\varepsilon- \\ & \rho {C_2}\frac{{{\varepsilon ^2}}}{{k + \sqrt {\nu \varepsilon } }} + {C_{1\varepsilon }}\frac{\varepsilon }{k}{C_3}{G_b} + {S_\varepsilon }{\text{。}} \end{split}$ (5)

 ${C_{1e}} = 1.44,{C_2} = 1.9,{\sigma _e} = 1.2,{\sigma _k} = 1.0{\text{。}}$

Realizable k-ε湍流模型的Realizable，是指该模型满足雷诺应力的一些数学限制，和现实物理现象中的湍流相容。该模型与标准k-ε模型和RNG k-ε模型相比，能够更准确地模拟湍流的扩散，同时在模拟包含旋流、边界层和强逆压梯度下的分离流、回流方面，表现出较好的精度。

1.2 液滴蒸发理论

 ${d_t} = \frac{{{c_p}{\rho _f}{R_s}{d_{{r_s}}}}}{{\lambda \ln \left[ {1 + \displaystyle\frac{{{\lambda _s}}}{\lambda }\displaystyle\frac{{{c_p}}}{L}\left( {T - {T_s}} \right)} \right]}}{\text{。}}$ (6)

1.3 液体喷雾理论

2 柴油机水下排气红外抑制优化设计

 图 1 柴油机水下排气模型 Fig. 1 The model of diesel exhaust under water

1）在排气管内部设置喷淋系统，充分利用水雾的汽化潜热首先吸收排气管内部的高温气体；

2）在排气管的末端设置了小孔排气装置，利用小孔将大团热气打散后排出，增加了气体与环境海水的交换效率，利用海水吸收大量热气，使得最终浮出水面的气体温度大大降低。

1）首先建立排气管内部喷淋的模型，以喷射水雾的汽化潜热效应最大化为目标，通过对比不同水流、水雾直径等参数，得到喷头参数设置；

2）然后建立小孔排气模型，以“湿气+水”作为输入量，通过条件不同的排气口直径、数量和排列方式，已浮出水面气体的温度为设计指标，得到小孔排气参数设置。

 图 2 排气管末端上温度分布 Fig. 2 The temperature distributing of exhaust pipe end

 图 3 轴线上温度分布 Fig. 3 The temperature distributing with the axes

 图 4 出口截面上水的体积分数分布 Fig. 4 The water volume fractional distributing on the end of outlet

 图 5 对称面上水的体积分数分布图（t=28.383 4 s） Fig. 5 The water volume fractional distributing on symmetry section (t=28.384 s)

 图 6 对称面上温度分布图（t=28.3834 s） Fig. 6 The temperature distributing on symmetry section (t=28.384 s)

 图 7 水平面最高温度随时间变化曲线 Fig. 7 The highest temperature record with time

3 结　语

潜艇的水下热排放是暴露其红外特征的重要因素，本文提出的内置喷淋+末端小孔排气方式对高温排气管进行冷却，通过建模并仿真计算，表明本文提出的降温方案有效，可以将排气管内的高温气体降低至常温左右，大大降低了水面尾迹的红外辐射强度，是一种对潜艇红外尾迹有效控制的手段。

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