飞机液压系统固体颗粒污染分析与控制

针对飞机液压系统固体颗粒污染,分析了固体颗粒污染物的来源及其危害,进而提出了控制飞机液压系统固体颗粒污染的方法.这对分析与解决飞机液压系统故障,确保飞机的飞行安全有着重要的意义.     

Intrinsic kinetics of the oxidative reaction of dichloroacetic acid employing hydrogen peroxide and ultraviolet radiation

In a previous work it has been shown that the combination of H₂O₂ and low wavelength UV radiation is a suitable process for degrading dichloroacetic acid (DCA). The final result provided a validated and complete reaction scheme. That proposal included two possible ways for the hydroxyl radical to react with DCA [Zalazar, C., Labas, M., Brandi, R., Cassano, A., 2007. Dichloroacetic acid degradation employing hydrogen peroxide and UV radiation. Chemosphere 66, 808-815].This work was directed to a single objective: to derive, from the previous reaction sequence, a mathematical model able to represent the kinetics of DCA oxidation and validate its predictive quality with experiments. This representation of the reaction must include all the required variables for an ulterior reactor design and scale-up and, consequently, the kinetic model parameters must be independent of the shape, size and configuration of the laboratory reactor.Working with a complete set of experimental runs that included all the involved variables, the unknown kinetics parameters of the DCA degradation were obtained by comparing predicted concentrations by the model (represented by a set of two ordinary differential equations and two algebraic equations coupled with a mass and a radiation balance inside the reactor) with the experimental values, employing a multi-parameter non-linear regression analysis. Experimental values confirmed the validity of the proposed mechanism. Additionally, an optimal concentration ratio of hydrogen peroxide with respect to DCA was obtained (r=CH₂O₂/C_DCA≈8).The intermediate results of the numerical solution of the complete system of differential and algebraic equations representing the proposed complete reaction mechanism were useful to find simplified, analytical expressions for the reaction rates of DCA and H₂O₂. The obtained rates resulting from these simplifications were compared with those of the complete system showing a very satisfactory concordance. This outcome is, at the same time, a clear indication of the significant influence of the radical in the reaction evolution.     

The future challenges for “clean coal technologies”: Joining efficiency increase and pollutant emission control

Coal offers an abundant widely spread fossil energy resource. It is available at a quite-stable price from many international suppliers and it will continue to play a significant role in new generating capacity, if security and diversity of supply remain fundamental. In this paper we point out the state of the art in the field of “clean coal technologies” evidencing the perspectives of improvement and the critical elements. Both the emission control of NO_x, SO_x, and particle matter and the advanced coal conversion pathways like ultra-supercritical (USC), pressurized fluidized bed combustion (PFBC), and integrated gasification combined cycle (IGCC) are reviewed and analyzed. At the end some elements concerning the perspectives of CO₂ emission control strategies are outlined.     

污染气体红外光谱仿真及参数设置研究

利用红外辐射传输理论,阐述了污染气体红外光谱仿真的基本模型,提出了在已知背景光谱和干扰物光谱的情况下进行污染气体红外光谱仿真的方法。仿真结果与实测光谱进行了验证比较,说明了仿真方法的可行性。研究了大气温度及浓度程长积等参数设置对仿真光谱的影响,通过大气温度对仿真光谱的影响研究解释了特征峰消失和反转现象;通过浓度程长积对仿真光谱研究解释了饱和现象。本文的方法可以应用于各种污染气体的光谱仿真、探测和识别。     

DEM-LES simulation of coal combustion in a bubbling fluidized bed Part II: coal combustion at the particle level

The discrete element method-large eddy simulation (DEM-LES) is used to model coal combustion at the particle level in a bubbling fluidized bed. The gas phase is modelled as a continuum and the solid phase is modeled by DEM. Chemical reactions consist in the heterogeneous reactions of char with O₂, CO, CO₂, NO, and N₂O, and in the homogeneous reactions involving CO, O₂, NO, and N₂O. The colliding particle-particle heat transfer is based on the analysis of the elastic deformation of the spheres during their contact. The model predicts the effects of the particle heterogeneous flow structure on the thermal characteristics of coal particles when heating and burning, and the gaseous emissions from a fluidized sand-coal binary mixture. The heating rates are 1627 and for, respectively, 0.8 and diameter coal particles fed into the fluidized bed. The instantaneous contribution of the collision heat transfer is weak, less than 5.0% of the total power exchanges (coal combustion, radiation, convection and collision) during the heating and 1.5% during the combustion. The temperature of the coal particles exceeds the bed temperature, which is in qualitative agreement with experimental data from literature. The effects of the diameter of coal particles, of the bed temperature, and of the inlet gas velocity on the thermal characteristics are also studied.     

Using photoelectrochemical measurements for distinguishing between direct and indirect hole transfer processes on anatase: Case of oxalic acid

Photocurrents collected from an interface between polycrystalline anatase and an aqueous solution of oxalic acid were measured as a function of oxalic acid concentration and photon flux at 365 nm. According to a kinetic model previously developed, such data can be used as a diagnostic tool for distinguishing between direct oxidation involving valence band holes and an indirect process, involving (surface bound) OH radicals. In the case of oxalic acid studied here, from the linear relation between initial slopes of photocurrent versus concentration and photon flux, a direct process is indicated.     

加力燃烧室污染特性计算

通过数值模拟方法，预估某型涡扇发动机加力燃烧室污染性能。采用κ－ε双方程模型描述紊流特性；采用修正的κ－ε－ｇ紊流燃烧模型和两步反应系统，来估算燃烧流场。其中ＣＯ和ＮＯ浓度都通过求解其紊流输运方程得到，而碳粒浓度采用多维经验分析法获取。对最大状态和加力状态等１８种飞行工况下加力室流场和污染性能进行了数值计算。     

Incentive pricing and economic profitability of load management program

This study considers both the internal and external costs of the utility in deriving the avoided capacity cost (ACC) and the avoided operating cost (AOC) induced in the power system in Taiwan (Taipower) caused by the implementation of load management (LM) program. The ACC comprises the avoided generation cost and the avoided network capacity cost. Meanwhile, the AOC is calculated by considering the differences between the total and specific time period energy consumption ratios before and after the implementation of the LM program. This study also develops a financial analysis method using least-cost and benefit-cost models to assess the financial profitability of implementing LM program from a participant's point of view. The design and construction of a partial load-leveling eutectic salt cooling energy storage air conditioning (CES) system in a target office building in Kaohsiung, Taiwan, is discussed in order to simulate the cost-benefit of the CES system from the perspective of the utility and from that of the participant. The results of this case study confirm the effectiveness of the developed models in simulating the economic benefits of implementing LM program from the perspectives of both the utility and the participant.     

地下车库排风量的计算和污染物扩散过程模拟

对5种常用地下停车库通风换气量计算公式的比较表明,因公式中系数取值的差异而导致不同公式计算结果相差悬殊。对密闭大空间、对怠速行驶条件下汽车排气污染物排气尾流中的扩散过程进行了数值模拟,分析了CO在排气尾流中的浓度分布及扩散特性。结果表明单车尾气动量小,温度低,形成的烟羽流经过一段距离之后,迅速扩散,其扩散及其分布对合理的布置排风口位置具有重要的影响。     

Prompt tracking of indoor airborne contaminant source location with probability-based inverse multi-zone modeling

Indoor air quality (IAQ) has a significant influence on occupants' comfort, health, productivity, and safety. Existing studies show that the primary causes of many IAQ problems are various airborne contaminants that either are generated indoors or penetrate into indoor environments with passive or active airflows. Accurate and prompt identification of contaminant sources can help determinate appropriate IAQ control solutions, such as, eliminating contaminant sources, isolating and cleaning contaminated spaces. This study develops a fast and effective inverse modeling method for identifying indoor contaminant source characteristics. The paper describes the principles of the probability-based adjoint inverse modeling method and formulates a multi-zone model based inverse prediction algorithm that can rapidly track contaminant source location with known source release time in a building with many compartments. The paper details the inverse modeling procedure with modification of an existing multi-zone airflow and contaminant transport simulation program. The application of the method has been demonstrated with two case studies: contaminant releases in a multi-compartment residential house and in a complex institutional building. The numerical experiments tested the source identification capability of the program for various contaminant sensing scenarios. The investigation verifies the effectiveness and accuracy of the developed method for indoor contaminant source tracking, which will be further explored to identify more complicated indoor contamination episodes.