four) placed in a tier (on one side of the furnace). The furnaces have the same total outlet cross-sectional areas of the nozzles (ΣFb) and the same jet velocities related to these areas (wb). The well-known swirl furnace of the TsKTI has a design close to the furnace arrangement under consideration. According to the data of [1], the air fraction βair that characterizes the mixing and enters through once through burners into the furnace volume beneath them can be estimated using the formula βair = 1 – (3) which has been verified in the range = 0.03–0.06 for a furnace chamber equipped with two frontal once through burners. Obviously, if we increase the number of burners by a factor of 2, their equivalent diameter, the length of the initial section of jets S0 and the area they “serve” will reduce by a factor of Then, for example, at = 0.05, the fraction βair will decrease from 0.75 to 0.65. Thus, Eq. (3) may be written in the following form for approximately assessing the effect of once through burners on the quality of mixing in a furnace:βair = 1 – 3.5f nb ' ,where is the number of burners (or air nozzles) on one wall when they are arranged in one tier both in onesided and opposite manners.
The number of burners may be tentatively related to the furnace depth af (at the same = idem) using the expression (5)
It should be noted that the axes of two large opposite air nozzles ( = 1)—an arrangement implemented in an inverted furnace—had to be inclined downward by more than 50° [8].
One well-known example of a furnace device in which once through jets are used to create a large vortex covering a considerable part of its volume is a furnace with tangentially arranged burners. Such furnaces have received especially wide use in combination with pulverizing fans. However, burners with channels having a small equivalent diameter are frequently used for firing low-calorific brown coals with high content of moisture. As a result, the jets of air-dust mixture and secondary air that go out from their channels at different velocities(w2/w1 = 2–3) become turbulence and lose the ability to be thrown a long distance; as a consequence, the flame comes closer to the water walls and the latter are contaminated with slag. One method by which the tangential combustion scheme can be improved consists of organizing the so-called concentric admission of large jets of air-dust mixture and secondary air with the fuel
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and air nozzles spaced apart from one another over the furnace perimeter,
accompanied by intensifying the ventilation of mills [9, 10]. Despite the fact that the
temperature level in the flame decreases, the combustion does not become less stable because the fuel mixes with air in a stepwise manner in a horizontal plane.
Vortex furnace designs with large cortices the rotation axes of which are arranged transversely with respect to the main direction of gas flow have wide possibilities in terms of controlling the furnace process. In [1], four furnace schemes with a controllable flame are described, which employ the principle of large jets colliding with one another; three of these schemes have been implemented. A boiler with a steam capacity of 230 t/h has been retrofitted in accordance with one of these schemes (with an inverted furnace) . Tests of this boiler, during which air-dust mixture was fed at a velocity of 25–30 m/s from the boiler front using a high concentration dust system, showed that the temperature of gases at the outlet from the furnace had a fairly uniform distribution both along the furnace width and depth . A simple method of shifting the flame core over the furnace height was checked during the operation of this boiler, which consisted of changing the ratio of air flow rates through the front and rear nozzles;this allowed a shift to be made from running the furnace in a dry-bottom mode to a slag-tap mode and vice Versace. A bottom-blast furnace scheme has received rather wide use in boilers equipped with different types of burners and mills. Boilers with steam capacities ranging from 50 to 1650 t/h with such an aerodynamic scheme of furnaces manufactured by ZiO and Bergomask have been installed at a few power stations in Russia and abroad . We have to point out that, so far as the efficiency of furnace process control is concerned, a combination of the following two aerodynamic schemes is of special interest: the inverted scheme and the bottom-blast one. The flow pattern and a calculation analysis of the furnace process in such a furnace during the combustion of lean coal are presented in [13].
Below, two other techniques for controlling the furnace process are considered. Boilers with flame–stoker furnaces have gained acceptance in industrial power engineering, devices that can be regarded to certain degree as controllable ones owing to the presence of two zones in them . Very different kinds of fuel can be jointly combusted in these furnaces rather easily. An example of calculating such a furnace
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device is given in [2]. As for boilers of larger capacity, work on developing controllable two-zone furnaces is progressing slowly . The development of a furnace device using the so-called VIR technology (the transliterated abbreviation of the Russian introduction, innovation, and retrofitting) can be considered as holding promise in this respect. Those involved in bringing this technology to the state of industry standard encountered difficulties of an operational nature (the control of the process also presented certain difficulties). In our opinion, these difficulties are due to the fact that the distribution of fuel over fractions can be optimized to a limited extent and that the flow in the main furnace volume has a rather sluggish aerodynamic structure. It should also be noted that the device for firing the coarsest fractions of solid fuel in a spouting bed under the cold funnel is far from being technically perfect.
Centrifugal dust concentrators have received acceptance for firing high-reactive coals in schemes employing pulverizing fans to optimize the distribution of fuel as to its flow rate and fractions. The design of one such device is schematically shown in [9]. Figure shows a distribution of fuel flow rates among four tiers of burners that is close to the optimum one. This distribution can be controlled if we furnish dust concentrators with a device with variable blades, a solution that has an adequate effect on the furnace process.
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燃煤锅炉的燃烧进程控制
存在于火电厂的市场的燃料供应，某些操作参数需要改变（或保留）的情况下 ，以及经济和环境方面倾向的要求使他们变得更加严格的不稳定趋势是导致使控制燃烧与传热过程炉设备非常紧迫的主要因素。解决这个问题的办法有两个方面。第一阶段包括发展燃烧技术和当新装置设计时高炉的设计。第二阶段包括现有的现代化设备。在两种情况下，技术精髓的采用必须通过类似试验与计算研究的使用来证实。有着丰富经验的机组研究和生产协会（ TsKTI ）和齐奥专家取得锅炉操作和实验进行了调查，他们的模式使他们能够提出一些新设计的混和机动性，换言之，可控炉装置已在发电站投入使用多年，与此同时，一种近似零一维，锅炉炉膛燃烧进程总线计算模型在TsKTI 已经研制成功，这一模型允许Tsk-ti 专家获取计算这一进程中的主要参数，计算研究炉膛采用不同技术时的发射与燃烧方式。当然，火炉燃烧进程的调整方法有诸如改变空气过剩系数，烟气再循环率，燃料和空气在锅炉空间内的分配，以及其它在锅炉运行期间书面的控制图表。然而，它们对进程的影响自然是有限的。另一方面，控制锅炉的燃烧进程很可能意味着在某种条件下发成实质性改变，在这种条件下发生燃烧和传热，目的是大幅度扩大负荷量，尽量减少热损失，减少炉渣的污染程度，减少排放的有害物质，并且转型成再燃物。这种控制，可利用以下三个主要因素:
(i)流动的氧化剂和气体以一种期望的空气动力学方式在火焰中流动 (ii)将燃料供应到火炉的方法并证实燃料已经供应到地方了 (iii)经过研磨的优良燃料
后者意味着火炉床的方法被用作带有火焰的燃料燃烧过程。流化床燃烧的方法可以实施三个设计版本：带有密集床的机械炉，流化床锅炉，以及喷动床炉。
正如一下所要展示的，第一个因素可以通过在锅炉装置周围建立一些庞大的漩涡转移大量的空气和燃烧产品来实现。如果燃料进给是在火焰中进行，最佳的进给方式是将其进给到漩涡中心区域附近，这种方式特别适用在高度密集炉设备中。在这一区域的燃烧过程具有较低的空气过剩因数??1，在这一很长过程时这一因素有助于使燃烧过程更稳定和减少排放的氮间内这些成分都要存在于此，氧化物 。
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同样重要的是，对于锅炉燃烧控制过程，当固体燃料燃烧时，也要优化将燃料碾磨精化。如果我们要尽量减少不完全燃烧，燃料的研磨程度应该与位置相协调，在这一位置上，燃料被送进炉膛，同时供应燃料应讲究方法，因为碳的不完全燃烧不但是因为大型燃料组分不完全燃烧，而且还因为某些经过研磨的细质不燃烧的缘故。（特别是某些挥发性的成分Vdaf<20%）。
由于存在绘画般的显示流体运动的可能性，锅炉空气动力学吸引了大量研究人员和设计师的关注，他们一直致力于发展和改进锅炉设备。与此同时，锅炉空气动力学的关键在于混合中心（集中的传递），这一过程的可估计的定量参数，只能间接或特殊的测量。成分在炉膛内混合的质量严格上取决于数量，布局，还有从个别炉膛和喷嘴喷射出来的流体动力，以及它们与流动的废气或与墙壁的相互作用。
有人建议，气体喷射距离可以作为参数确定气体燃烧器通道中燃料与空气的混合程度。这种如何估计有效混合的做法可以在一定的程度上用于混合装置的炉的分析。显然，越大的喷射距离（和其势头），造成的在炉膛内持续存在的速度梯度的时间越长，一个参数，确定如何流动中完全混合。注意，在喷嘴或燃烧器出口的喷射高度越高，它涵盖的距离越短，因此，组成部分不完全是在炉体内混合。一旦通过燃烧器便在漩涡这方面具有优势。
还有人提议，因为它们以速度w2和密度ρ2渗透变成横向（漂移）流移动速度w1和密度ρ1，所以在喷嘴混合的程度与气体喷射距离密切相关，以下列方式：公式（1）
Ks是相称的因素，取决于射流轴线之间的距离（Ks= 1.5至1.8）天然气与空气在炉中混合，然后在炉中使用不完整的混合技术的实验研究结果作为一个参数在[5]报告。
第一轮曾经是密集射流与周围介质以其最初的形式混合的熔炉，在这里喷气轴的流速仍然是等于在喷嘴孔半径r0的速度W2。喷嘴吹入到炉的速度下降非常迅速，超越了最初一节的限制，壁挂式燃烧器的轴弯曲对准炉的出口。
有人可能会认为，有三个理论模型用于分析流量G2和流量G1混流喷射的原理。第一种模式是喷射流入“自由”空间的情况（ G1= 0 ）；第二个模型是喷射流入横向（漂移）的情况下，当前的流量G1?G2 ；第三个模型是当喷射流入漂移流的情况下，此时流量G1 10