Increasing Flashback Resistance in Lean Premixed Swirl-Stabilized Hydrogen Combustion by Axial Air Injection
Increasing Flashback Resistance in Lean Premixed Swirl-Stabilized Hydrogen Combustion by Axial Air Injection
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DOI：
10.1115/1.4029119
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发表时间：
2014-06
影响因子：
1.5
通讯作者：
T. Reichel;S. Terhaar;Oliver Paschereit
中科院分区：
文献类型：
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作者：
T. Reichel;S. Terhaar;Oliver Paschereit
由于稀薄预混燃烧允许燃料效率和低排放，因此其是固定式燃气轮机中的当今技术水平。从长远来看，这也是航空发动机的一种很有前途的方法，因为可以克服预混合器中的贫油熄火（LBO）和火焰回火等安全问题。虽然对于氢的使用，LBO限制被延长，但是回火倾向增加。因此，应用轴向空气喷射以消除燃烧预混氢的旋流稳定燃烧室中的回火。轴向喷射在径向旋流发生器中心轴上形成非旋流射流，影响涡流破裂位置。在目前的工作中，流场的变化及其对模型燃烧室回火极限的影响进行了评估。首先，参数研究进行等温试验条件下，在水洞采用粒子图像测速（PIV）。变化的参数是轴向喷射的空气量和涡流数。随后，在大气燃烧室试验台中，在轴向空气喷射的情况下评估回火安全性，并记录稳定性图。使用高速OH* 化学发光成像测量火焰结构。通过对反应流场的同步高速PIV测量，可以深入了解时间分辨的反应流场，并通过定性光片（QLS）技术评估原始PIV图像的Mie散射来指示火焰位置。等温试验确定了轴向空气喷射克服喷嘴出口处轴向速度不足的潜力，这被认为是至关重要的，以便提供回火安全性。轴向空气喷射的这种效果示出在火焰的存在下占上风。通常，逆燃安全性被示出受益于轴向空气喷射量的提高和较低的涡流数。注意，后者也导致增加的NOx排放，而轴向空气喷射不会。此外，燃料动量表示，以积极影响回火阻力，虽然基于不同的机制，建议的解释。总之，在入口温度为620 K和高达化学计量条件下，在试验台的整个操作范围内实现了燃烧器的防回火操作，同时保持个位数的NOx排放低于2000 K的火焰温度。
Since lean premixed combustion allows for fuel-efficiency and low emissions, it is nowadays state of the art in stationary gas turbines. In the long term, it is also a promising approach for aero engines, when safety issues like lean blowout (LBO) and flame flashback in the premixer can be overcome. While for the use of hydrogen the LBO limits are extended, the flashback propensity is increased. Thus, axial air injection is applied in order to eliminate flashback in a swirl-stabilized combustor burning premixed hydrogen. Axial injection constitutes a non-swirling jet on the central axis of the radial swirl generator which influences the vortex breakdown position. In the present work changes in the flow field and their impact on flashback limits of a model combustor are evaluated. First, a parametric study is conducted under isothermal test conditions in a water tunnel employing particle image velocimetry (PIV). The varied parameters are the amount of axially injected air and swirl number. Subsequently, flashback safety is evaluated in the presence of axial air injection in an atmospheric combustor test rig and a stability map is recorded. The flame structure is measured using high-speed OH* chemiluminescence imaging. Simultaneous high-speed PIV measurements of the reacting flow provide insight in the time-resolved reacting flow field and indicate the flame location by evaluating the Mie scattering of the raw PIV images by the means of the Qualitative Light Sheet (QLS) technique.The isothermal tests identify the potential of axial air injection to overcome the axial velocity deficits at the nozzle outlet, which is considered crucial in order to provide flashback safety. This effect of axial air injection is shown to prevail in the presence of a flame. Generally, flashback safety is shown to benefit from an elevated amount of axial air injection and a lower swirl number. Note, that the latter also leads to increased NOx emissions, while axial air injection does not. Additionally, fuel momentum is indicated to positively influence flashback resistance, although based on a different mechanism, an explanation of which is suggested. In summary, flashback-proof operation of the burner with a high amount of axial air injection is achieved on the whole operating range of the test rig at inlet temperatures of 620 K and up to stoichiometric conditions while maintaining single digit NOx emissions below a flame temperature of 2000 K.Copyright © 2014 by ASME