Another real gas effect is called ionization. Ionization is a process in which electrons orbiting about the nucleus of their atom are broken out of their orbits and become individual parts of the total gas mixture. Ionization progresses gradually, as does dissociation,and has an effect similar to that of dissociation on the gas properties."

另一个真实气体效应称为电离。电离是沿原子核周围轨道飞行的电子脱离自身轨道变成整个气体混合物中独立成分的过程。电离过程是逐渐进行的，就像离解过程一样，而且对于气体性质的影响也与离解的类似。

Understandably,when the air in the vicinity of a vehicle in flight is dissociated or dissociated and ionized,the validity of data taken in a wind tunnel at the same Mach number without dissociation is subject to question. Because of this, a tremendous effort has been devoted to the development of facilities that provide more realistic flow conditions. Unfortunately.no facility has yet been developed in which complete duplication of the flow conditions of flight can be

obtained at the higher Mach numbers. There are three prinary reasons for this. The first is the inability of available materials to withstand the extreme temperature and pressure environments without burning or some form of erosion. The result is much contamination of the flow and a rapid destruction of tunnel components at the higher temperatures. The second is the inability to maintain the high temperatures required long enough to obtain data because of extremely high heat losses from the air due to radiation. The third reason deals with the previously described dissociation phenomenon. After the air is heated it must be expanded through a nozzle in order to achieve high velocities. In the process of expansion through the nozzle it cools very rapidly. If this cooling were to take place at a slow enough rate, all of the dissociated molecules would recombine so that the air entering the test section and approaching the model would have the same composition as atmospheric air;that is, it would be a mixture of molecules of O2 and N2. However,it develops that the rate of cooling during the expansion in any practical nozzle is too fast for the recombination to occur. The result is that the air reaching the test section will be in the dissociated state at a low temperature. This phenomenon is called "flow freezing". Flow freezing affects the Mach number and other flow parameters in the test section and results in a test medjum that may differ a great deal from the desired mixture of molecules of O2 and N2.

可以理解，当飞行器飞行时，要是附近的空气处于离解或既离解又电离的状态，那么，从风洞中相同马赫数但未离解状态下测得的数据是否有效，就有问题了。由于这个原因，人们已经作了极大的努力去研制能够提供更加接近于实际气流条件的设备。遗憾的是，迄今尚未研制出任何可在高马赫数下完全复现飞行气流条件的设备。其主要原因有三个。第一是现有材料不能耐温度极高、压力极大的环境而不被烧坏或不受某种腐蚀。其结果是，在高温下，气流严重污染，而且风洞部件迅速损坏。第二是不能将所需的高温维持到足以测取数据那么长的时间，因为由于辐射，空气中的热损耗极大。第三个原因与前面所说的离解现象有关。在将空气加热之后，必须使其经过喷管膨胀以便达到高速。空气在通过喷管影胀的过程中会迅速冷却。如果这种冷却的速度低到足以使所有离解的分子再化合，那么，空气进入试验段到达模型时，其组成会与大气相同，也就是说，成为氧分子O2和氮分子N2组成的混合物。然而，实际情况是，任何实际喷管里气流膨胀时冷却速度都很快，使分子来不及重新化合。结果到达试验段的空气处于低温离解状态。这种现象称为“气流冻结”。气流冻结会影响试验段中的马赫数和其他气流参数，从而有可能使试验介质与预期的氧气和氮气分子的混合物大不相同。

Facilities which have been developed in the process of trying to provide realistic flow conditions at high speeds and which are now used fairly extensively in high-speed testing include hotshot tunnels, plasma jets, shock tubes, shock tunnels, and light gas guns. 

在试图提供实际高速气流条件的过程中，发展了一批设备、目前这些设备已相当广泛地用于高速试验；它们包括热射式风洞、等离子体射流、激波管、激波风洞以及轻气体炮等。

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