许磊,张翼,徐春龙,宋猛,庞浩宇,张宇,唐诗泽,雷丽军.某柴油喷油嘴新冲蚀寿命预测模型及瞬态特性数值模拟[J].表面技术,2023,52(1):121-131, 177.
XU Lei,ZHANG Yi,XU Chun-long,SONG Meng,PANG Hao-yu,ZHANG Yu,TANG Shi-zhe,LEI Li-jun.Prediction Model of New Erosion Life and Numerical Simulation of Transient Characteristics of a Diesel Fuel Injector[J].Surface Technology,2023,52(1):121-131, 177 |
| 某柴油喷油嘴新冲蚀寿命预测模型及瞬态特性数值模拟 |
| Prediction Model of New Erosion Life and Numerical Simulation of Transient Characteristics of a Diesel Fuel Injector |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.01.013 |
| 中文关键词: 空化流动 水锤压力 喷嘴喷孔 冲蚀 寿命预测 |
| 英文关键词:cavitation flow water hammer pressure nozzle orifice erosion life prediction |
| 基金项目:山西省科技重大专项(MQ2016-02-01);山西省“百人计划”创新团队项目资助 |
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| Author | Institution |
| XU Lei | School of Energy and Power Engineering, North University of China, Taiyuan 030051, China |
| ZHANG Yi | School of Energy and Power Engineering, North University of China, Taiyuan 030051, China |
| XU Chun-long | China North Engine Research Institute, Tianjin 300400, China |
| SONG Meng | School of Energy and Power Engineering, North University of China, Taiyuan 030051, China |
| PANG Hao-yu | School of Energy and Power Engineering, North University of China, Taiyuan 030051, China |
| ZHANG Yu | School of Energy and Power Engineering, North University of China, Taiyuan 030051, China |
| TANG Shi-zhe | School of Energy and Power Engineering, North University of China, Taiyuan 030051, China |
| LEI Li-jun | School of Energy and Power Engineering, North University of China, Taiyuan 030051, China |
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| 中文摘要: |
| 目的 针对柴油喷油嘴喷孔内部空化现象及冲蚀磨损问题，建立了考虑近壁面不同边界层内群气泡溃灭产生冲蚀影响的柴油喷油嘴瞬态特性仿真模型。探究柴油喷油嘴内部冲蚀磨损程度的影响因素，并对喷孔内部冲蚀磨损寿命进行预测。方法 首先，采用MATLAB对不同近壁面距离的空化泡对壁面作用压力及射流速度进行函数拟合，结合传统经验公式，推导了可考虑距壁面不同距离的群空泡阻力修正经验公式。其次，利用Fluent中UDF建立了基于阻力修正经验公式以及网格自适应算法的有限元模型，用Rrs冲蚀风险预测模型和冲蚀疲劳试验结果对本文提出的新模型进行验证。在此基础上讨论了喷嘴孔圆锥度Kfac及动态特性对喷孔冲蚀磨损的影响。结果 Rrs冲蚀磨损风险预测模型和冲蚀磨损疲劳试验结果与本文提出的新模型结果有较好的一致性，证明了该新模型的可行性。有限元仿真结果显示，当喷嘴形状相同时，随着针阀向上移动，空化现象被有效地抑制，逐渐向喷孔的入口处收缩，其上最大射流速度和水锤压力会略微增加，但总体空化区域多集中于喷孔入口上表面处。随着喷嘴几何尺寸从Kfac0增加至Kfac2、Kfac4，其上喷孔的气泡溃灭最大微射流速度及最大水锤压力分别减少11.29%、1.4%。当无量纲距离δ=1.3时，其最大速度和压力值仅为无量纲距离δ=1.0时的2.6%，故可忽略无量纲距离δ>1.3时的气泡溃灭对壁面的冲蚀磨损影响。随着喷嘴几何尺寸从Kfac0增加至Kfac2、Kfac4，其上喷孔内壁面最小寿命分别提升了18.17%及32.32%。结论 喷嘴孔圆锥度Kfac及动态特性均对近壁面空化冲蚀磨损程度产生影响。总体空化冲蚀磨损区域多集中于喷孔入口上表面处，可对此采取措施以提高总体喷嘴寿命，疲劳寿命计算时可忽略距壁面无量纲距离δ>1.3时气泡对壁面产生的影响，喷嘴喷孔圆锥度的增加可降低喷孔内侧冲蚀磨损程度，显著提升喷嘴寿命。 |
| 英文摘要: |
| Aiming at the cavitation phenomenon and erosion wear problem in the nozzle hole of diesel fuel injector, by introducing the research theory of the pressure and jet velocity of cavitation bubbles with different distance near the wall, the traditional empirical formula is modified, and the transient characteristic simulation model of diesel fuel injector considering the erosion effect caused by the collapse of group bubbles in different boundary layers near the wall is established. Using the method of simulation, the influencing factors of the internal erosion wear degree of diesel fuel injection nozzle are explored, and the erosion wear life of the nozzle hole is predicted. Firstly, based on the research conclusions of the pressure and jet velocity of cavitation bubbles with different distance to the wall, the function fitting of the pressure and jet velocity of cavitation bubbles with different distance to the wall is carried out by using MATLAB software. Combined with the traditional empirical formula, the resistance correction empirical formula of group cavitation considering different distances from the wall surface is derived. Secondly, the finite element model based on resistance correction empirical formula and grid adaptive algorithm is established by using UDF in fluent. The Rrs cavitation risk prediction model is established by using the theory of representing erosion risk by steam mass condensation rate. The new model proposed in this paper is verified by Rrs cavitation risk prediction model and cavitation fatigue test results, It is proved that the new model proposed in this paper has good accuracy. Based on the calculation results of this model, the effects of nozzle orifice conicity Kfac and needle valve dynamic characteristics on orifice erosion wear are discussed. As the geometric size of the nozzle increases from Kfac0 to Kfac2 and Kfac4, the cross-sectional area of the orifice becomes smaller along the flow direction, the reflux near the wall and the separation of the boundary layer are restrained, the cavitation will be restrained, and the bubble interaction area near the wall will be reduced. At the same time, the fluid is more likely to generate eddy currents at the axis of the orifice, which will reduce the bubbles near the wall of the orifice, bubbles tend to be far away from the wall, so as to effectively inhibit the interaction between bubbles and the wall near the wall. The maximum jet velocity and water hammer pressure near the wall will be reduced, and the bubble collapse of the upper orifice will be reduced by 11.29% and 1.4% respectively; when the nozzle shape is the same, with the upward movement of the needle valve, the fluid area from the surface of the needle valve to the inner shell of the nozzle head increases, and the fluid has more space and time to adjust the flow path before flowing into the nozzle hole, which can flow into the nozzle hole at a smaller included angle with the axis of the nozzle hole, so that the backflow in the nearby area is weakened, the cavitation phenomenon is effectively restrained, and gradually shrinks towards the inlet of the nozzle hole. The effects of dimensionless distance on the transient maximum jet velocity and water hammer pressure at different distances from the wall are also studied. When the dimensionless distance δ=1.3, the maximum velocity and pressure are only 2.6% of that when the dimensionless distance δ=1.0. Therefore, the effect of bubble collapse at dimensionless distance δ>1.3 on erosion wear of wall surface can be ignored. Finally, the influence of nozzle hole conicity on nozzle hole life is explored. With the increase of nozzle geometric size from Kfac0 to Kfac2 and Kfac4, the minimum life of the inner wall surface of the upper nozzle hole is increased by 18.17% and 32.32% respectively. From the analysis results, it can be seen that the erosion wear area is mainly located at the upper wall near the inlet orifice. Therefore, it can be considered to do surface treatment on the wall near the inlet orifice to reduce the overall cavitation wear of the orifice, or appropriately increase the taper of the orifice during design and processing, so as to reduce the cavitation wear of the orifice and improve the service life of the orifice. |
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