Aeroacoustics of Three-Stream Jets
Aeroacoustics of Three-Stream Jets
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三流射流气动声学
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发表时间：
2012
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通讯作者：
B. Henderson
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文献类型：
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作者：
B. Henderson
* 给出了在亚音速条件下工作的加热、三流、共环排气系统辐射噪声的声学测量结果。这些实验是在一系列堆芯、旁路和三次流温度和压力下进行的。该喷管系统的风扇-核心面积比为2.92，三级-核心面积比为0.96。当第三流速度低于旁路流速度时，引入第三流对辐射噪声的影响是降低宽边和峰值喷气噪声角处的高频噪声级。在后观察角处的中频噪声辐射受到第三流条件的影响。核心速度对峰值噪声水平的影响最大，而旁路与核心质量流量比对峰值喷气噪声方向的水平有轻微影响。第三流射流条件对峰值噪声水平没有影响。在存在模拟前飞气流的情况下引入第三喷流限制了第三喷流对辐射噪声的影响。对于等效的理想推力条件，双流和三流射流可以产生类似的声学频谱，虽然高频噪声水平往往是较低的三流射流。I.介绍UTURE涡轮发动机架构可以提供第三排气流，这将可用于潜在的降噪技术。使用第三流作为附加的旁路流允许降低旁路流和环境空气之间的速度剪切速率，并且还可以允许改变芯和旁路速度同时保持推力，从而也允许降低芯和旁路流之间的速度剪切速率。然而，三流射流的噪声特性（和潜在的降噪）是未知的。本文研究了在亚音速排气条件下，一个加热的、三股流、共环喷流的噪声特性。研究未来超音速飞机性能和噪声之间的权衡的系统研究将需要用于三流射流的噪声预测工具。目前的预测工具解决单1，2，3和双流1，4，5射流。为了将这些工具应用于三股射流，有必要假设三股射流中的两股完全混合，这一假设可能不适用于某些未来的发动机排气。以前的三股流实验集中于使用第三股流来降低外流边界处的剪切速率，并修改反向速度剖面、超音速、双流射流中的射流激波结构6。未对亚音速排气条件进行研究。开发新的半经验预测工具将需要获得相关的噪声数据库，这些数据库可用于模型开发、校准和验证。这些数据库并不存在，因此目前无法扩展现有的预测工具或开发新的工具。本文所报道的工作的目的是研究具有与未来超音速商用飞机相似的喷管面积比的三流排气系统的噪声特性。这项研究的重点是亚音速喷气排气，因为未来的超音速商用飞机将具有高亚音速或低超音速的起飞发动机排气。这项研究将包括喷流速度、喷流速度比和前飞对远场噪声的影响。二.实验方法实验是在美国宇航局格伦研究中心的航空声学推进实验室（AAPL）进行的，如图1所示。AAPL是一个半径为66英尺的测地线圆顶，采用声学楔形物处理。AAPL包含喷嘴声学测试装置（NATR），可产生直径53英寸的模拟向前飞行流，马赫数达到0.35。高流量喷气出口试验台（HFJER）是一种双流道喷气发动机模拟器，能够模拟大多数商用涡轮风扇发动机的温度和压力[见参考文献（7）]，位于 * 研究员声学分支，MS 54-3，21000 Brookpark Rd.，克利夫兰，俄亥俄州44135。
*Results from acoustic measurements of noise radiated from a heated, three-stream, coannular exhaust system operated at subsonic conditions are presented. The experiments were conducted for a range of core, bypass, and tertiary stream temperatures and pressures. The nozzle system had a fan-to-core area ratio of 2.92 and a tertiary-to-core area ratio of 0.96. The impact of introducing a third stream on the radiated noise for third-stream velocities below that of the bypass stream was to reduce high frequency noise levels at broadside and peak jet-noise angles. Mid-frequency noise radiation at aft observation angles was impacted by the conditions of the third stream. The core velocity had the greatest impact on peak noise levels and the bypass-to-core mass flow ratio had a slight impact on levels in the peak jet-noise direction. The third-stream jet conditions had no impact on peak noise levels. Introduction of a third jet stream in the presence of a simulated forward-flight stream limits the impact of the third stream on radiated noise. For equivalent ideal thrust conditions, two-stream and three-stream jets can produce similar acoustic spectra although high-frequency noise levels tend to be lower for the three-stream jet. I. Introduction UTURE turbine-engine architectures may provide a third exhaust stream that will be available for potential noise reduction technologies. Using the third stream as an additional bypass stream allows for the reduction of the velocity shear rate between the bypass flow and the ambient air and may also allow for alteration of the core and bypass velocities while maintaining thrust, thus allowing for reduced velocity shear rates between the core and bypass flows as well. However, the noise characteristics (and potential noise reduction) of three-stream jets are unknown. The current study investigates the noise characteristics of a heated, three-stream, co-annular jet operated at subsonic exhaust conditions. System studies that investigate the trades between performance and noise for future supersonic aircraft will need noise prediction tools for three-stream jets. Current predictive tools address single 1,2,3 and dual-stream 1,4,5 jets. To apply these tools to three-stream jets, it is necessary to assume that two of the three jet streams are fully mixed, an assumption that may be inadequate for some future engine exhausts. Previous three-stream experiments focused on using the third stream to reduce the shearing rate at the outer flow boundary and modify the jet shock structure in an inverted-velocity-profile, supersonic, dual-stream jet 6 . Subsonic exhaust conditions were not investigated. The development of new semi-empirical prediction tools will require the acquisition of relevant noise databases that can be used for model development, calibration, and validation. These databases do not exist so extension of existing prediction tools or the development of new tools is not currently possible. The purpose of the work reported here is to investigate the noise characteristics of a three-stream exhaust system with nozzle area ratios similar to those that may be used for future supersonic commercial aircraft. The study focuses on subsonic jet exhausts as future, supersonic, commercial aircraft will have takeoff engine exhausts that are at high subsonic or low supersonic speeds. The study will include the impact of jet velocities, jet velocity ratios, and forward flight on far-field noise. II. Experimental Approach The experiments were conducted in the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center shown in Fig. 1. The AAPL is a 66 ft radius geodesic dome treated with acoustic wedges. The AAPL contains the Nozzle Acoustic Test Rig (NATR), which produces a 53 inch diameter simulated forward-flight stream reaching Mach numbers of 0.35. The High Flow Jet Exit Rig (HFJER), a dual-stream jet engine simulator capable of replicating most commercial turbo-fan engine temperatures and pressures [see Ref. (7)], is centered in the * Researcher, Acoustics Branch, MS 54-3, 21000 Brookpark Rd., Cleveland, OH 44135.