快响应PSP技术用于高超声速圆柱绕流的非定常压力测量

压敏涂料(PSP)技术是飞行器风洞实验大面积定量测压和流动显示的重要工具。为了发展非定常流动压力测量和脉冲风洞中全局压力测量能力,航天空气动力技术研究院开发了快速响应压敏涂料技术,与中科院化学所共同合作开发的压敏涂料采用PtTFPP作为发光基团,稳定性较强,持续光照下发光强度衰减为1.5%/h。采用自主研制的静态标定设备在标定腔内测量不同温度和压力条件下20mm×20mm涂料样片的表面发光强度来确定涂料的压力响应特性和Stern-Volmer公式,并设计制作了2套快响应时间动态标定设备,测得涂料典型响应时间在0.2ms。在中国航天空气动力技术研究院FD-03高超声速风洞中对平板圆柱装置进行了Ma=5的 PSP 试验,利用高速相机采集图像数据后,经过批量数据处理,采集频率为250Hz,得到了间隔时间4ms 的连续压力场数据。结合纹影图像和油流图对得到的PSP结果进行了分析,利用同时采集的测压孔数据对PSP 结果进行了比较。试验结果表明,快响应PSP技术可以更详细地显示流场结构,并能同时得到很好的定量压力数据。

Unsteady pressure measurement around circular cylinder in hypersonic flows using fast response PSP

The fast response Pressure Sensitive Paint (PSP)was studied to develop the capa-bility of making global pressure measurements under unsteady and short duration flow condi-tions.Fast response PSP is necessary for measuring unsteady flow fields in hypersonic wind tun-nels and short-duration wind tunnels.By the use of the fast response PSP,unsteady flow field can be accurately measured.Various PSP formulations are under continuous development in col-laboration between CAAA and Institute of Chemistry China Academy of Science.These pressure sensitive paints use PtTFPP as luminophore,which is relatively photo-stable:the decay of lumi-nescent intensity with continuous illumination is 1 .5 percent/h.This paint can be sprayable on all kinds of model surfaces.It is durable enough to withstand the aerodynamic forces.With the development of porous PSP,there has been a need for accurate characterization of the response time of PSP.Dynamic calibration methods have been developed to meet this need.Response time of PSP was measured from a step change of pressure created by solenoid valve and pulsating jet. Two dynamic calibration devices were developed to test the response time of PSP.For unsteady calibration the paint was sprayed onto 20 mm × 20 mm aluminum plates.Photo multiplier tube (PMT)was used as the light detector,which is the most critical component in the dynamic cali-bration device.Several fast response PSP was developed and tested.The typical response time of PSP is 0.2ms.The static calibration system was used to get the relation between the pressure and luminescence intensity.PSP samples were installed in a pressure chamber in which both the pres-sure and temperature can be set.The sample was excited by UV light and its photoluminescence was detected by a CCD digital camera.The experiment was conducted at different pressures and temperatures.After data processing,the relationship between the luminescence intensity and pressure can be obtained.To demonstrate the capability of PSP for pressure measurements in hy-personic wind tunnel,a cylinder mounted on a flat plate was tested in a Mach 5 hypersonic wind tunnel.The experiment was conducted in the blow down hypersonic wind tunnel FD-03 of China Academy of Aerospace Aerodynamics (CAAA).The diameter of circular cylinder is 25mm.The pressure on the plate surface was measured by several pressure taps simultaneously.The temper-ature of the model was detected by a Pt100 temperature sensor in real time.A 200-mm-diameter observation window on the ceiling was used as the optical access.Two 450W xenon lamps with bandpass filter (365±10 nm)were used for excitation light.The emission from the PSP was de-tected by photron high-speed camera SA5 with 12-bit intensity resolution.A bandpass filter (650 ±10 nm)was placed in front of the camera lens.The surface pressure distributions were ac-quired.Unsteady pressure behavior around the cylinder measured by the unsteady PSP was shown clearly.The pressure distribution results were obtained at Ma= 5 ,and the unsteady PSP measurement frame rate was 250 frames/s.A detailed pressure distribution pattern of complex flow phenomena including shock wave/shock wave interactions could be clearly measured with PSP.It was confirmed that fast response PSP could be used for quantitative unsteady pressure distribution measurements in hypersonic wind tunnel.