射流控制水翼空化流动的多工况适应性研究

Adaptability of Cavitation Flow Controlled by Active Jet under Multi-cavitation Conditions

空化时常会使船舶推进器、泵、水轮机等水力机械部件产生噪声、振动和腐蚀,导致设备总体性能的大幅下降,甚至破坏,因此开展空化流动控制具有重要意义。借助高速全流场测试技术,获得NACA66(MOD)原始水翼及射流水翼表面的空化形态,研究射流控制参数对空化抑制的影响规律,分析主动射流在变工况下对空化流动控制的适应性。研究发现:在不同工况下,主动射流均可以取得明显的空化抑制效果,当射流流量及射流位置不同时,空化流动控制效果不同。在云空化阶段,射流水孔与水翼前缘距离与弦长比值为0.19(H1模型)可以收到较好的空化抑制效果,且始终优于H2模型;而在片空化阶段,射流水孔与水翼前缘距离与弦长比值为0.45(H2模型)空化抑制效果更优。不同的射流流量系数可以实现对空化流场的主动控制,且存在最佳射流流量系数,使空化抑制效果最优。在给定射流位置(H1模型)和射流流量(流量系数为0.0245)时,在空化不断发展过程中(0.83≤σ≤1.46),空化抑制效果较为稳定,与实验获得最佳空化抑制有效性参数的偏差均在0.06以内,H1模型表现出良好的工况适应性,可实现多工况下空化的流动控制。

Cavitation often causes noise,vibration and corrosion of hydraulic mechanical components such as ship propellers,pumps,and turbines,and causes the overall performance of the equipment to be greatly reduced,or even destroyed.Therefore,it is of great significance to carry out cavitation flow control.The method of arranging injection water holes on the suction side of the hydrofoil can effectively block the re-entrant jet to suppress cavitation.Through the high-speed visual flow field test technology,the cavitation morphology of NACA66(MOD)original hydrofoil and jet hydrofoil surfaces was obtained.The influence of jet control parameters on cavitation suppression was studied,and the adaptability of active jet to cavitation flow control under varying operating conditions was analyzed.It was found that under different cavitation conditions,the active jet significantly reduced the cavity length around the suction surface of the hydrofoil,and the cavitation suppression effect was significant.When the jet coefficient and jet position were different,the effect of cavitation flow control was also different.In the cloud cavitation stage,the jet of 0.19 chord-length position from the leading edge of the hydrofoil(H1 model)can achieve the best cavitation suppression effect,and it was always better than that of the H2 model in the range of cavitation numberσ≤1.28.In the sheet cavitation stage,σ>1.44,the jet of 0.45 chord-length position from the leading edge of the hydrofoil(H2 model)was more effective in suppressing cavitation.When the fixed jet position(H1 model)and jet flow rate(flow coefficient was 0.0245),simplified flow control process,during the continuous development of cavitation(cavitation number was with 0.83≤σ≤1.46),the cavitation suppression effect was relatively stable,the deviation from the best suppression effect was within 0.06,which showed that the H1 model had good adaptability to working conditions.The research results provided a direction for exploring the active control technology of cavitation flow.