缸内流动对对置活塞二冲程发动机换气效果的影响

王苏飞; 章振宇; 张付军

doi:10.13224/j.cnki.jasp.20220094

缸内流动对对置活塞二冲程发动机换气效果的影响

doi: 10.13224/j.cnki.jasp.20220094

王苏飞^1,,
章振宇¹,
张付军^{1, 2,*, ,}

1.
北京理工大学机械与车辆学院，北京 100081
2.
北京理工大学深圳研究院，广东深圳 518057

详细信息

作者简介:
王苏飞（1990-），男，博士生，主要从事内燃机进排气及燃烧研究

通讯作者:
张付军（1966-），男，教授、博士生导师，博士，主要从事发动机电控相关研究。E-mail：zfj123@bit.edu.cn

中图分类号: V234；TK421
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出版历程
- 收稿日期: 2022-02-28
- 网络出版日期: 2023-02-11

Effect of in-cylinder flow on gas exchange efficiency of opposed-piston 2-stroke engines

WANG Sufei^1
,,
ZHANG Zhenyu¹,
ZHANG Fujun^{1, 2,*
, ,}

1.
School of Mechanical Engineering，Beijing Institute of Technology，Beijing 100081，China
2.
Shenzhen Research Institute， Beijing Institute of Technology，Shenzhen Guangdong 518057，China

摘要

摘要:
换气过程中的缸内流动及废气分布对对置活塞二冲程（OP2S）发动机换气效果的影响规律目前缺乏充分的研究。采用CONVERGE建立了OP2S发动机的CFD模型并通过仿真计算研究了扫气口倾角、扫气口构型及转速通过改变扫气气流组织影响换气效果的规律。结果表明扫气口倾角对OP2S发动机缸内流动有显著且非单调的影响。扫气口倾角$ \mathrm{\alpha } $≤5°时，扫气气流聚集于气缸轴线，缸壁附近存在周边废气滞留区；当扫气口倾角$ \mathrm{\alpha } $>5°时，换气过程初期扫气气流在扫气口附近汇聚为环状进气涡流，在该进气涡流中心产生低压区，并导致气缸中心流动方向与外围的扫气气流方向相反，最终导致气缸轴线出现柱状的中心废气滞留区。随着扫气口倾角增大，周边滞留区逐渐减小消失，而中心滞留区出现并增强，两者的变化规律共同造成了残余废气系数的非单调变化规律。大扫气口倾角下复合式气口的扫气气流可兼顾气缸中心和外围，换气效果显著优于单层气口。相较于倒置组合气口，组合气口的缸内流动组织更为合理，扫气效率更高。
- 对置活塞 /
- 二冲程 /
- 扫气 /
- 缸内流动 /
- 残余废气
Abstract:
The effect of in-cylinder flow and residual distribution on gas exchange of opposed-piston 2-stroke （OP2S） engines is yet to be thoroughly studied. The effects of scavenge port angle, scavenge port structure and engine speed on scavenge efficiency by directing scavenge flow in OP2S engine were investigated by modeling and CFD simulation with CONVERGE software. Result showed that scavenge port angle had significant and non-monotonic effect on in-cylinder flow. For scavenge port angle $ \mathrm{\alpha } $≤5°, scavenge flow was collected around cylinder axis and a border residual area appeared next to liner; for scavenge port angle $ \mathrm{\alpha } $>5°, scavenging flow formed a circular downward flow around cylinder axis at the early stage of scavenging. A low-pressure area was induced by this circular flow at its center and drew nearby gas upwards, forming a column of central residual area along cylinder axis. As scavenge port angle increased, the border residual area declined and disappeared while central residual area came into being and got strengthened. The combined effects of both residual areas resulted in the non-monotonic trend in residual ratio. Composite scavenge port produced drastically lower residual ratio than simple port at relatively larger scavenge port angle, since uniform scavenge flow suppressed the low-pressure area, weakening central residual area. This effect was less prominent for reversed composite scavenge port, rendering it less effective than composite scavenge port.
- opposed-piston /
- 2-stroke /
- scavenging /
- in-cylinder flow /
- residual gas

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图 1 OP2S发动机气缸结构

Figure 1. Cylinder structure of OP2S engine

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图 2 扫气口倾角

Figure 2. Scavenge port angle

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图 3 三种扫气口结构

Figure 3. Three different scavenge ports

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图 4 单元尺寸为1.4～4 mm的计算结果对比

Figure 4. Comparison of computational results from cell size 1.4—4 mm

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图 5 模型验证

Figure 5. Model validation

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图 6 转速及扫气口结构对残余废气系数的影响

Figure 6. Effect of engine speed and scavenge port structure on residual ratio

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图 7 缸内中心低压区的建立过程（N=4500 r/min，α=20°）

Figure 7. Establishing of central low-pressure area （N=4500 r/min，α=20°）

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图 8 曲轴转角上止点后168°时刻扫气口倾角对缸内轴向速度分布的影响（N=4500 r/min）

Figure 8. Effect of scavenge port angle on axial velocity distribution at 168° after top dead center （N=4500 r/min）

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图 9 扫气口倾角对换气过程中缸内废气分布的影响（N=4500 r/min）

Figure 9. Effect of scavenge port angle on residual distribution during scavenging （N=4500 r/min）

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图 10 转速对换气过程中缸内废气分布的影响（α=20°）

Figure 10. Effect of engine speed on residual distribution during scavenging （α=20°）

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图 11 扫气口倾角对组合气口缸内当量比分布的影响（N=1500 r/min）

Figure 11. Effect of scavenge port angle on equivalence ratio distribution for composite port （N=1500 r/min）

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图 12 扫气口倾角对组合气口缸内轴向速度分布的影响（N=1500 r/min）

Figure 12. Effect of scavenge port angle on axial velocity distribution for composite port （N=1500 r/min）

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图 13 扫气口倾角对倒置组合气口缸内当量比分布的影响（N=1500 r/min）

Figure 13. Effect of scavenge port angle on equivalence ratio distribution for reversed composite port （N=1500 r/min）

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图 14 扫气口倾角对倒置组合气口缸内轴向速度分布的影响（N=1500 r/min）

Figure 14. Effect of scavenge port angle on axial velocity distribution for reversed composite port （N=1500 r/min）

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