Field and CFD Study of Fuel Distribution in Pulverized Fuel(PF)Boilers

The article presents both field and CFD results of a new concept of a mechanical pulverized fuel(PF)distributor.The goal of the study was to improve the pulverized coal-air mixture separation in PF boilers where the fuel preparation and feeding system was operated in a combined coal and biomass grinding conditions.The numerical analysis was preceded after a field study,where measurements were carried out in a pulverized coal-fired(PC)boiler equipped with a technology of NOx reduction by means of primary methods.Proper distribution of a pulverized coal-air mixture to the individual burners is one of the fundamental tasks of the combustion systems where the primary methods are implemented to control the NOx emission.Problems maintaining the proper distribution of fuel to the burners related primarily to the boilers where the coal and biomass co-grinding is used.Changing the load of coal-mills and fuel type at the same time(i.e.,different types of biomass)could result in less effective separation of pulverized fuel particles in PF distributors.Selection of an appropriate construction of a distributor will allow the better control of the combustion process which results in decreased NOx emission while keeping the proper combustion efficiency,i.e.,less unburned carbon(UBC)in the fly ash.The results of the field measurements made it possible to create a CFD distribution base model,which was used for the analysis of a new splitter construction to be used in a PF distributor.Subsequent analysis of the numerical splitter enables precise analysis of its construction,including the efficiency of separation and the prediction of conveying of the coal and biomass particles.

Study on the Effects of Dome Fuel Distribution Ratio on Lean Blowout of a Model Combustor

The experimental studies and numerical simulation were conducted on the effects of the dome fuel distribution ratio on the lean blowout of a model combustor.The experimental results indicate that as the key parameter,the dome fuel distribution ratio,increases from 2.06%to 16.67%,the lean blowout equivalence ratio declines obviously at the beginning,and then the decrease slows down,in addition,the amplitude of the pressure fluctuation in the combustor reduces significantly while the dominant frequency keeps basically constant.In order to analyze the experimental results,the numerical simulation is adopted.The temperature and local equivalence ratio distributions are employed to explain the reason why the lean blowout performance improves with the increase of the dome fuel distribution ratio.

考虑燃料电池汽车加氢负荷的电-氢系统协同优化运行

在建设新型电力系统背景下,为提高能源利用率,降低交通系统碳排放,促进配电网与交通网络融合,考虑燃料电池汽车加氢行为影响下负荷时空分布特性,构建计及燃料电池汽车交通流量与加氢行为的优化调度模型。首先,采用起止点对刻画燃料电池汽车交通流量模型,为模拟燃料电池汽车出行,采用Dijkstra算法搭建燃料电池汽车最短加氢路径模型。其次,针对可再生能源出力不确定性,基于Wasserstein距离建立风电功率预测误差模糊集,考虑电力-交通网络约束,并构建含加氢站优化调度的分布鲁棒优化模型。最后,利用强对偶理论将分布鲁棒优化模型转化为混合整数线性规划模型进行求解,采用改进的33节点配电网和24节点交通网对调度方法进行验证。结果表明,所提方法相比于鲁棒优化系统总成本有所降低,加氢站调度方案在保守和乐观之间达到平衡,实现加氢站与上级网络之间良性互动。

基于分布鲁棒优化的电热综合能源配网系统与氢能源站协同优化

氢能源站(Hydrogen Fueling Station,HFS)对氢气生产和供应至关重要。然而HFS通常在午夜和凌晨生产氢气,同时由于热负荷处于高峰,热电联产(Combined-Heat-and-Power,CHP)机组的灵活性降低。在可再生能源比例较高的电热综合能源配网系统(Integrated Electricity-Heat Energy System,IEDS)中,CHP机组缺乏灵活性将不可避免地影响IEDS和HFS的经济和安全运行。先前的研究侧重于配电网系统和HFS的协同运行,而没有考虑灵活性问题。论文旨在提出IEDS和HFS的协同分布鲁棒协同调度模型,以实现协同优化运行,从而降低运营成本和安全运营。在该模型中,HFS中产生的废热被回收后注入热网系统。利用历史数据对风电场景进行聚类,构建风电不确定性集。并相应地提出了具有更好收敛速度的改进Benders分解算法,从而进一步以并行和分散式求解所考虑的优化模型。此外,基于综合能源测试系统实例进行了算例仿真,在考虑HFS协同调度的前提下,所提出的协同调度模型能够使运行成本降低7.8%,并分析了所提出的协同调度模型在处理风电不确定性方面的有效性。最后,相比经典Benders算法,论文提出的改进Benders分解算法求解时间降低了70%,迭代次数减少了50%,验证了分散式优化具有良好计算性能。

考虑用户响应不确定性的园区综合能源系统分布鲁棒低碳调度

电、气、冷、热等多种能源耦合的园区综合能源系统(IES)有助于提升对可再生能源发电的消纳,提高能源利用效率。文中提出基于分布鲁棒优化的园区IES日前低碳经济调度策略。首先,构建考虑碳交易和综合需求响应的园区IES的运行架构,并建立碳交易模型和基于用户用能习惯的综合需求响应模型。其次,以最小化运行成本为目标,并考虑园区IES运行约束和燃料掺氢的电转气(P2G)设备两阶段运行等约束,建立了园区IES日前低碳经济调度模型。然后,构建计及用户响应不确定性的园区IES分布鲁棒低碳经济调度模型,并利用对偶原理将该分布鲁棒优化模型转化为二阶锥优化模型,采用商业求解器CPLEX求解。最后,以包含电、气、冷、热多种能源耦合的典型园区IES为例,对所提优化模型的可行性和有效性进行了验证。算例结果表明,采用所提出的低碳经济调度策略可以有效提升园区IES运行的经济性和消纳可再生能源发电的能力,降低IES碳排放和运行风险。

Migration behavior of solid fuel particles during granulation process and its influence on combustion property

Iron ore sintering process is the main CO_(2) emission source throughout the integrate steelworks,which primarily comes from the combustion of solid fuels.Improving the combustion efficiency and reducing the solid fuel consumption are important ways to reduce the CO_(2) emission in the sintering process.Around the efficient combustion of fuel,the migration behavior and combustion characteristics of solid fuel in the granulation process were investigated.The results indicated that during the granulation process,fuel particles with size less than 0.5 mm mainly migrated into the granules with grain size of 1-3,3-5 and 5-8 mm;fuel particles with size of 0.5^(-1)mm mainly migrated into granules of 1-3 mm;fuel particles with size of 1-3,3-5 and 5-8 mm mainly entered the granules with the same grain size.With the increase in fuel particles grain size from-0.5 to+8 mm,the combustion efficiency exhibited a firstly-increasing and then decreasing tendency,while the NO_(x) exhibited a decreasing tendency.Potential reason can be described that finer fuel particles(-1 mm)easily distributed in the outer layer of the granules,which combusted fiercely due to its larger specific surface area,leading to the development of incomplete combustion and the conversion of fuel nitrogen;the combustion efficiency of larger fuel particles was restricted by the inner diffusion of O_(2),which then contributed to the reduction of NO_(x) under the inadequate combustion atmosphere.

Experimental study on combustion characteristics of supersonic combustor based on alternating-wedge strut

Acetone Planar Lase-Induced Fluorescence(PLIF)and OH-PLIF were employed to capture the fuel distribution and OH distribution downstream for the supersonic combustor based on the alternating-wedge strut.The combustion establishment process and combustion mode in the combustor under different fuel injection methods and different equivalence ratios were analyzed.Combined with the kerosene-PLIF and OH-PLIF results in the cavity combustor,a comparative analysis was conducted to understand the combustion characteristics and combustion modes between the alternating-wedge strut-based combustor and the cavity-based combustor.The results show that the combustor is in weak combustion mode in the case of low equivalence ratio,and the combustor is in intensive combustion mode in the case of high equivalence ratio.The lower limit of the equivalence ratio of the combustor to maintain the intensive combustion mode varies based on different fuel injection methods.The OH distribution under reacting condition has a strong correlation with the fuel distribution under non-reacting condition.The OH fluorescence signal near the injector is weaker when the fuel distribution is more concentrated.The injector position located at the base of the strut rear has better mixing performance,enabling the combustor to be in intensive combustion mode at a lower equivalence ratio.The combustion reaction in the alternating-wedge strut-based combustor is not necessarily dominated by mass transfer due to the mixing enhancement and premixed zone downstream of strut,while the combustion reaction process in the cavity-based combustor is mainly influenced by mass transfer.