﻿ 船用排气引射装置计算及优化改进
 舰船科学技术  2021, Vol. 43 Issue (7): 88-92    DOI: 10.3404/j.issn.1672-7649.2021.07.018 PDF

Calculation and improvement of a marine gasturbine exhaust injector
SHI Zhen, ZHANG Shan-ke, YUAN Wen-qi, MA Zheng-jun
The 703 Research Institute of CSSC, Harbin 150078, China
Abstract: When the marine gas turbine working in the case module, the high working temperature and the huge heat dissipation of the gas turbine let the temperature of the case module very high, this will affect the normal operation of the electronic components and accessories, it is not safe for the staff. So the exhaust injector is widespread used on the ship to cool the case module. In this thesis, the numerical simulation have been done with a marine gas turbine exhaust injector, the result show that the ejector coefficient is less than 10%, it can not meet the cooling requirement. In this paper, One-dimensional calculation has been done for the ejector and determined the optimum dimension of the structure, then, according to the real distribution, The three-dimensional flow field optimization calculation has been done to the improved exhaust ejector. The results show that the ejector coefficient of the improved structure raised, it can meets the design requirement, it is usefully to the structure design in the future.
Key words: exhaust injector     numerical simulation     improvement
0 引　言

1 原装置的数值分析 1.1 排气引射装置结构分析及建模

 图 1 燃气轮机排气引射系统模型 Fig. 1 Model of gas turbine exhaust ejector system

1.2 网格划分

 图 2 排气引射系统计算网格 Fig. 2 Grid of exhaust ejector system
1.3 计算原理和方法

 $\frac{{\partial \rho }}{{\partial t}} + \nabla \cdot (\rho \mathop V\limits^{\rightharpoonup} ) = 0,$ (1)
 $\frac{{\partial (\rho \mathop V\limits^{\rightharpoonup} )}}{{\partial t}} + \nabla \cdot (\rho \mathop V\limits^{\rightharpoonup} \mathop V\limits^{\rightharpoonup} ) = - \nabla p + \nabla \cdot \Pi,$ (2)
 $\frac{{\partial (\rho E)}}{{\partial t}} + \nabla \cdot (\rho \mathop V\limits^{\rightharpoonup} E) = \nabla \cdot \left[ {( - pI + \Pi ) \cdot \mathop V\limits^{\rightharpoonup} } \right] - \nabla \cdot \mathop q\limits^{\rightharpoonup},$ (3)
 $\frac{p}{\rho } = RT{\text{。}}$ (4)

 $\varPi = - \frac{2}{3}\mu (\nabla \cdot {\mathop V\limits^{\rightharpoonup}} )I + \mu (\nabla {\mathop V\limits^{\rightharpoonup}} + \nabla {{\mathop V\limits^{\rightharpoonup}} ^{\rm{T}}}),$ (5)
 $I = \left\{ {{\delta _{ij}}} \right\},$ (6)
 $E = e + \frac{1}{2}{\mathop V\limits^{\rightharpoonup}} \cdot {\mathop V\limits^{\rightharpoonup}},$ (7)
 $e = \frac{1}{{(\gamma - 1)}}\frac{p}{\rho },$ (8)
 ${\mathop q\limits^{\rightharpoonup}} = - k\nabla T{\text{。}}$ (9)

1.4 计算边界条件

 ${S_i} = - \left( {\frac{\mu }{\alpha }{v_i} + {C_2}\frac{1}{2}\rho \left| v \right|{v_i}} \right)\text{。}$ (10)

1.5 原型计算结果

2 排气引射装置设计计算

 图 3 引射器结构示意图 Fig. 3 Structure diagram of ejector
2.1 排气引射装置能力计算

 $({f_2}/{f_{11}})opt = ( - b + \sqrt {{b^2} - 4ac} )/2a,$ (11)

 $a = {\varphi _1}{\varphi _2},$ (12)
 $b = - \left\{ {}{\varphi _1}{\varphi _2} + 2{\varepsilon _{12}}\left[ \begin{gathered} \left( {\frac{1}{{{\varphi _3}}} - 0.5} \right)\frac{{{\upsilon _3}}}{{{\upsilon _1}}}{\left( {1 + n} \right)^2} \\ - \left( {{\varphi _2}{\varphi _4} - 0.5} \right)\frac{{{\upsilon _3}}}{{{\upsilon _1}}}{n^2} \\ \end{gathered} \right] {} \right\},$ (13)
 $c = 2{\varepsilon _{12}}\left( {\frac{1}{{{\varphi _3}}} - 0.5} \right)\frac{{{\upsilon _3}}}{{{\upsilon _1}}}{\left( {1 + n} \right)^2}{\text{。}}$ (14)

 $\frac{{\Delta p}}{{{p_2}}} = {k_p}{\Pi _{1*}}\frac{{{p_1}}}{{{p_2}}}\frac{{{f_{11}}}}{{{f_2}}}q_{12}^2\left[ \begin{split} &{\varphi _1}{\varphi _2}\frac{{{\lambda _{12}}}}{{{q_{12}}}} \\ &+ {\varepsilon _{1*}}\left( {{\varphi _1}{\varphi _2} - 0.5} \right)\frac{{{\upsilon _2}}}{{{\upsilon _1}}}\frac{{{f_{11}}}}{{{f_{12}}}}{n^2} \\ & - {\varepsilon _{1*}}\left( {\frac{1}{{{\varphi _3}}} - 0.5} \right)\frac{{{\upsilon _3}}}{{{\upsilon _1}}}\frac{{{f_{11}}}}{{{f_2}}}{\left( {1 + n} \right)^2} \\ \end{split} \right]{\text{。}}$ (15)

 $\frac{{\Delta p}}{{{p_2}}} = 0.037\;71,$ (16)
 $\Delta p = 0.037\;1{p_2} = 3\;804{\rm{Pa}},$ (17)
 ${p_3} = {p_2} + \Delta p = 0.104\;68{\rm{MPa}}\text{。}$ (18)

2.2 引射器结构尺寸计算

 ${l_{c1}} = \left[\sqrt {0.083 + 0.76n} - 0.29\right]{d_1}/0.16,$ (19)

 ${d_{c1}} = 3.4{d_1}\sqrt {0.083 + 0.76n},$ (20)

 ${D_1} = {d_1}\sqrt {{{({f_2}/{f_{11}})}_{opt}}} ,$ (21)

 ${l_{c2}} = ({d_{c1}} - {D_1})/2,$ (22)

 ${l_c} = {l_{c1}} + {l_{c2}}\text{。}$ (23)

2.3 引射器结构改进

3 排气引射系统改进计算分析

 图 4 改进后的几何模型 Fig. 4 Improved geometric model

 图 5 中截面速度矢量图 Fig. 5 Velocity vector diagram of middle section

 图 6 中截面静温分布图 Fig. 6 Static temperature of medium section

4 结　语

1） 将原型混合段改为和排气管轴线重合之后，虽然没有达到设计要求，但排气引射系数有所提高。在进行排气引射系统设计时，应尽量保持引射器管道与燃机轴线垂直，尤其是引射器混合段。

2） 可将排气引射系统按照方案2进行改进，即混合段改为与排气管轴线重合的圆柱管段，直径D1，长度1.87D1，增设扩压管段，此时排气引射系数为10.62%，达到10%以上的设计要求。

3） 根据方案2改进之后，排气管道的压力损失减小，排气管入口面的总压降低，即动力涡轮的背压减小，这有利于提高燃气轮机的性能。

4） 在进行排气系统的设计时，应综合考虑对排气引射性能及排气压力损失的影响，在安装允许的情况下，管道宜直而短，弯头和收缩段要少。

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