针阀偏心程度对双孔喷嘴喷孔内流动及柴油喷雾的影响

The Effect of Needle Eccentricity Degrees on Flow and Diesel Spray Characteristics of a Dual-Hole Nozzle

为了研究柴油机多孔喷嘴喷雾的不对称性对柴油机热负荷、工作性能及使用寿命的影响,通过三维CFD数值模拟,研究针阀偏心运动时双孔喷嘴孔内流动及喷雾的分布情况。结果显示:针阀偏心程度∆X分别为0、0.02、0.04及0.06 mm时,偏离侧孔内燃油流量大、流速高,但沿程阻力的增大会造成出口处平均速度更小;偏心程度越大,两侧差异越明显。在固定的偏心程度下,孔内流动的不对称性仅与喷油压力有关,随着喷油压力及环境压力的增加,两侧喷雾体积分数及速度分布的不对称程度会加深。环境温度对喷雾不对称性有影响,但无确定规律。在针阀最大偏心程度为0.06 mm的条件下,随着喷油压力的增加,两孔的质量流量及燃油喷射总质量均增大,同时会加剧这两个参数的不对称性表现。

In order to study the influence of the asymmetry of the spray of the diesel engine multi-hole nozzle on the thermal load,working performance and service life of the diesel engine,the flow in the dual-hole nozzle and the distribution of spray when the needle valve moves eccentrically were studied through 3D CFD numerical simulation.The results show that:When the eccentricityΔX of the needle valve is 0,0.02,0.04,and 0.06 mm,the fuel flow volume in the deviation side hole is large and the flow rate is high,but the on-way resistance will cause the average velocity at the outlet to be smaller;The greater the degree of eccentricity,the more significant the difference on both sides.At a fixed eccentricity,the asymmetry of flow in the hole is only related to the injection pressure.With the increase of injection pressure and ambient pressure,the asymmetry of spray volume fraction and velocity distribution on both sides will increase.The ambient temperature has an effect on the asymmetry of spray,but there is no definite rule.Under the condition of a maximum eccentricity of 0.06 mm for the needle valve,as the injection pressure increases,the mass flow rate and total fuel injection mass of the two holes both increase,while exacerbating the asymmetry of these two parameters.