指定流量分配系数的多回流出口边界算法

doi:10.7527/S1000-6893.2022.26830

Abstract

Abstract:

The treatment of boundary condition at multiple outlets is one of the key issues in the numerical simulation of aero-engine combustors， as the mass flow ratios need to be within the engineering design limits， and the numerical stability needs to be ensured with recirculating flow at the outlets. In the present paper， an incompressible flow outlet boundary condition algorithm is developed to treat the boundary condition at multiple outlets with recirculating flow and specified flow ratios. The results of a series of numerical experiments show that stable and convergent solutions can be obtained using the proposed method. Cases of tetrahedral/hexahedral meshes and the mass flow ratio ranging from 0 to 1.0 are simulated， and the obtained maximum deviation is <0.001%. When the mass flow ratios at the multiple outlets are fixed， the resulted velocity profiles are not obviously affected by the location of outlet boundaries when the flows at the boundaries are not fully-developed or even recirculating. The proposed method is applied to the simulation of TECFLAM swirl burner. The predicted velocity components agree well with the experimental data even when the computational domain is truncated to one third of the original size. Compared to the conventional treatment of outlet boundary conditions， the method proposed enables to specify the mass flow ratios at multiple outlets and to adjust computational domain sizes according to the engineering design limits， which contributes to significant reduction of the overall computational cost.

Key words: free outlet boundary, mass flow ratio, recirculating flow, combustor simulation, incompressible flow

CLC Number:

V231.3

Kailong XU, Zaigang LIU, Shengli JIANG, Xing WANG, Pan ZHANG. Treatment of boundary condition at multiple outlets with recirculating flow and specified flow ratios[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2023, 44(5): 126830.

Figures/Tables 16

Fig. 1

Fig. 2

Fig. 3

Table 1

Mass flow rate statistics results of duct case with 90° T-branch

$α 1 ∶ α 2$	$0 ∶ 1.0$	$0.2 ∶ 0.8$	$0.4 ∶ 0.6$	$0.5 ∶ 0.5$	$0.6 ∶ 0.4$	$0.8 ∶ 0.2$	$1.0 ∶ 0$
入口流量/（kg∙s^-1）	0.667 805	0.667 805	0.667 805	0.667 805	0.667 805	0.667 805	0.667 804
出口1流量/（kg∙s^-1）	-0.000 005	0.133 561	0.267 119	0.333 895	0.400 683	0.534 243	0.667 805
出口2流量/（kg∙s^-1）	0.667 810	0.534 244	0.400 686	0.333 909	0.267 121	0.133 562	0.000 001
计算 $α 1$	-0.000 008	0.200 000	0.399 995	0.499 989	0.600 000	0.799 999	0.999 999
计算 $α 2$	1.000 008	0.800 000	0.600 005	0.500 010	0.399 999	0.200 001	0.000 001
流量误差/%	0.000 76	0.000 04	0.000 46	0.001 03	0.000 08	0.000 08	0.000 09

Table 1

Fig.4

Fig. 5

Table 2

Mass flow rate statistics results of duct case with 60° Y-branch

$α 1$ ∶ $α 2$	0∶1.0 图 5　60°Y形分叉管算例不同流量分配下速度分布 Fig. 5　Velocity distribution of duct case with 60° Y-branch at various mass flow ratios	0.1∶0.9 图 5　60°Y形分叉管算例不同流量分配下速度分布 Fig. 5　Velocity distribution of duct case with 60° Y-branch at various mass flow ratios	0.2∶0.8	0.3∶0.7	0.4∶0.6	0.5∶0.5
入口流量/（kg∙s^-1）	9.238 5×10^-4	9.238 5×10^-4	9.238 5×10^-4	9.238 5×10^-4	9.238 5×10^-4	9.238 5×10^-4
出口1流量/（kg∙s^-1）	-6.301 5×10^-9	9.238 4×10^-5	1.847 7×10^-4	2.771 6×10^-4	3.695 4×10^-4	4.619 3×10^-4
出口2流量/（kg∙s^-1）	9.238 6×10^-4	8.314 7×10^-4	7.390 8×10^-4	6.467 0×10^-4	5.543 1×10^-4	4.619 3×10^-4
计算 $α 1$	-0.000 007	0.099 999	0.200 000	0.300 001	0.400 000	0.500 000
计算 $α 2$	1.000 007	0.900 001	0.800 000	0.699 999	0.600 000	0.500 000
流量误差/%	0.000 7	0.000 1	0	-0.000 1	0	0

Table 2

Table 3

Test cases and sampling positions for truncation of computational domain

算例编号	W/m	$L i n / W$	$L m / W$	$L s / W$	出口边界条件	取样位置x/m
算例编号	W/m	$L i n / W$	$L m / W$	$L s / W$	出口边界条件	1.0	1.5	3.0	6.0
1	1	3	10	10	充分发展	√	√	√	√
2	1	3	10	10	本文方法	√	√	√	√
3	1	3	10	5	本文方法	√	√	√	√
4	1	3	10	3	本文方法	√	√	√
5	1	3	10	2	本文方法	√	√	√
6	1	3	10	1	本文方法	√	√
7	1	3	10	0.5	本文方法	√	√

Table 3

Fig. 6

Fig. 7

Fig. 8

Fig. 9

Fig. 10

Fig. 11

Fig. 12

Fig. 13

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Treatment of boundary condition at multiple outlets with recirculating flow and specified flow ratios

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