开放式喷射汽车风洞的尺寸和效率

Size and Efficiency of Open Jet Automotive Wind Tunnels

摘要:

近年来，世界各地汽车企业已建成许多汽车风洞，并在不久的将来会有更多汽车风洞的规划与建设。在风洞规划设计阶段确定的许多功能与参数决定了其整个运行生命周期，并影响建设和运行成本。本文研究通过适当选择3/4开口风洞的试验段几何尺寸，可以使早期的传统风洞中因有限截面发生的流动干扰在很大程度上得到补偿或减少到可忽略不计的程度。研究表明：对于具有不同堵塞度的各种车辆，流动干扰误差出乎意料地可以忽略，因此不需要对试验数据进行修正，这使得汽车风洞试验形成“自由”气流条件；试验阶段的初步尺寸可以比如今常见的情况小很多，也不影响测量结果的准确度，这带来了更低的建设成本，也降低了风洞系统运行的能源需求；自由射流的不稳定性必须被考虑，且射流长度不应该超过某个上限。

Abstract:

In recent years， a number of new wind tunnels for the automotive industry have been built across the world， and more such facilities are planned for the near future. Many decisions made in the early planning phase of the wind tunnel shape the facility throughout its operating life and contribute to both the construction and operating costs of the wind tunnel. The intent of this paper is to outline that with an appropriate choice of the test section geometry of 3/4 open-jet wind tunnels. The flow interferences that occur due to the finite cross section of the jet in a conventional wind tunnel can be largely compensated for or reduced to a negligible extent. It is shown that for a wide range of vehicles with varying degrees of blockage， residual interference becomes surprisingly negligible， so that a correction of the measured quantities is not required and conditions of “free” air flow are generated in the test section. Furthermore， it is shown that the coarse dimensions of a test section can be much smaller than is often the case today without affecting the quality of the measurement results， which leads to lower construction costs， but above all to lower energy requirements for the operation of the system. It is shown that the instabilities of the free jet must also be assumed， which results in an upper limit for the jet length that should not be exceeded.