Development and experimental validation of a one-dimensional dynamic hygrothermal modeling based on air humidity ratio

A modified one-dimensional transient hygrothermal model for multilayer wall was proposed using air humidity ratio and temperature as the driving potentials.The solution for the governing equations was obtained numerically by implementing the finite-difference scheme.To evaluate the accuracy of the model,a test system was built up to measure relative humidity and temperature within a porous wall and compare with the prediction of the model.The prediction results have good agreement with the experimental results.For the interface close to indoor side,the maximum deviation of temperature between calculated and test data is 1.87 K,and the average deviation is 0.95 K;the maximum deviation of relative humidity is 11.4%,and the average deviation is 5.7%.For the interface close to outdoor side,the maximum deviation of temperature between prediction and measurement is 1.78 K,and the average deviation is 1.1 K;the maximum deviation of relative humidity is 9.9%,and the average deviation is 4.2%.

Adaptive Air-Fuel Ratio Control with MLP Network

This paper presents an application of adaptive neural network model-based predictive control (MPC) to the air-fuel ratio of an engine simulation. A multi-layer perceptron (MLP) neural network is trained using two on-line training algorithms: a back propagation algorithm and a recursive least squares (RLS) algorithm. It is used to model parameter uncertainties in the nonlinear dynamics of internal combustion (IC) engines. Based on the adaptive model, an MPC strategy for controlling air-fuel ratio is realized, and its control performance compared with that of a traditional PI controller. A reduced Hessian method, a newly developed sequential quadratic programming (SQP) method for solving nonlinear programming (NLP) problems, is implemented to speed up nonlinear optimization in the MPC. Keywords Air-fuel ratio control - IC engine - adaptive neural networks - nonlinear programming - model predictive control Shi-Wei Wang PhD student, Liverpool John Moores University; MSc in Control Systems, University of Sheffield, 2003; BEng in Automatic Technology, Jilin University, 2000; Current research interests automotive engine control, model predictive control, sliding mode control, neural networks.Ding-Li Yu obtained B.Eng from Harbin Civil Engineering College, Harbin, China in 1981, M.Sc from Jilin University of Technology, Changchun, China in 1986 and PhD from Coventry University, U.K. in 1995, all in control engineering. He is currently a Reader in Process Control at Liverpool John Moores University, U.K. His current research interests are in process control, engine control, fault detection and adaptive neural nets. He is a member of SAFEPROCESS TC in IFAC and an associate editor of the IJMIC and the IJISS.

Air flow control based on optimal oxygen excess ratio in fuel cells for vehicles

Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio （OER） is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.

Transient Air-Fuel Ratio Control in a CNG Engine Using Fuzzy Neural Networks

The fuzzy neural networks has been used as means of precisely controlling the air-fuel ratio of a lean-burn compressed natural gas (CNG) engine. A control algorithm, without based on engine model, has been (utilized) to construct a feedforward/feedback control scheme to regulate the air-fuel ratio. Using fuzzy neural networks, a fuzzy neural hybrid controller is obtained based on PI controller. The new controller, which can adjust parameters online, has been tested in transient air-fuel ratio control of a CNG engine.

磁共振AIR-魔毯线圈在胸椎结核扫描中的应用价值

目的探讨联合应用AIR-魔毯线圈磁共振成像(MRI)对胸椎结核扫描图像信噪比(signal to noise ratio,SNR)、对比噪声比(contrast to noise ratio,CNR)和脂肪抑制成像效果的价值。方法选取我院80例经手术病理证实为胸椎结核患者,按1:1随机分为两组,应用常规线圈(脊柱相控阵线圈,头颈联合线圈)、常规线圈联合AIR魔毯线圈对两组患者分别进行扫描。扫描序列包括胸椎矢状位T_(2)WI,T_(1)WI,T_(2)FLEX,进一步测量、比较SNR,CNR及脂肪抑制效果,分析MRI多序列诊断胸腰椎结核的准确率、特异度和灵敏度。结果常规线圈联合AIR-魔毯线圈扫描组,胸椎矢状位图像的SNR、CNR及压脂效果优于常规线圈组。结论联合应用AIR-魔毯线圈的图像SNR、CNR得到提高,脂肪抑制效果稳定良好。

The Effect of Mass Ratio and Air Damper Characteristics on the Resonant Response of an Air Damped Dynamic Vibration Absorber

In this paper, it is shown that, a road vehicle 2DOF air damped quartercar suspension system can conveniently be transformed into a 2DOF air damped vibrating system representing an air damped dynamic vibration absorber (DVA) with an appropriate change in the ratio μ of the main mass and the absorber mass i.e. when mass ratio μ >> 1. Also the effect of variation of the mass ratio, air damping ratio and air spring rate ratio, on the motion transmissibility at the resonant frequency of the main mass of the DVA has been dis- cussed. It is shown that, as the air damping ratio in the absorber system increases, there is a substantial decrease in the motion transmissibility of the main mass system where the air damper has been modeled as a Maxwell type. Optimal value of the air damping ratio for the minimum motion transmissibility of the main mass of the system has been determined. An experimental setup has been designed and developed with a control system to vary air pressure in the damper in the absorber system. The motion transmissibility characteristics of the main mass system have been obtained, and the optimal value of the air damping ratio has been determined for minimum motion transmissibility of the main mass of the

Effects of Free-air CO2 Enrichment on Root Characteristics and C:N Ratio of Rice at the Heading Stage

A hydroponics experiment was conducted to investigate the rice root growth in FACE （free-air carbon dioxide enrichment）. The root biomass, root volume, ratio of root/shoot, number of adventitious roots and root diameter significantly increased under FACE conditions, while the CO2 enrichment decreased the N concentration in rice roots without any change in the C content, leading to an increase in root C：N ratio. Moreover, the elevated CO2 resulted in a remarkable decrease of root activity, expressed as per unit root dry weight, which might be responsible for decreased N concentration in roots.

Sensitivity and effect of key operational parameters on performance of a dual-cylinder free-piston engine generator

The free-piston engine generator(FPEG)is regarded as the next generation of energy conversion system which may replace traditional engines in the future.The effect of key operational parameters like excess air ratio of input mixture and ignition position on the engine performance of a dual-cylinder FPEG was investigated,and their sensitivity was analyzed in this paper.The operating compression ratio of the system is susceptible to changes in excess air ratio and ignition position.At the same time,it decreases from 15.8 to 6.6 when excess air ratio increases from 0.85 to 1.15,but it increases from 6.1 to 13.3 as ignition position increases from 15 mm to 20 mm.The operating frequency and indicated power are more sensitive to changes in excess air ratio than ignition position.But it is the opposite for the indicated thermal efficiency and friction loss.Excess air ratio and ignition position have a quite similar influence on heat transfer.Therefore,from the perspective of system operation and performance,it is preferable to keep excess air coefficient slightly below 1.0.In contrast,when selecting ignition position,it is of great importance to comprehensively consider the risk of structural damage caused by the increase in the compression ratio and in-cylinder gas pressure.

Effect of Air Injector on the Performance of an Air-lift for Conveying River Sand

An air-lift has been more recently applied in the dredging, deep-seated beach placer mining and underground mining engineering. However, the influence and mechanism of various parameters on the air-lift performance are not quite clear, especially the influence of flow pattern on lifting efficiency. Focusing on the problems mentioned above, the key part of the air-lift （namely, the air injector） was proposed aimed to reduce friction loss in the inner pipe according to improving flow field performance, thus increase the lifting efficiency. The study of relative factors of the performance of an air-lift is performed and the river sand is used as simulation of underground ore bed. The total lifting height of the experimental system is 3 m, the water flux, mass flow of solid particles, concentration of particles and lifting efficiency are measured under the same submergence ratios by changing the air injector, which is divided into nine specifications of air injection in this research. The experimental results indicate that the optimal air flow rate corresponding to excellent performance of the air-lift can be obtained in the range of 35-40 m3/h. The air injection method has a great effect on the performance of the air-lift, the air injector with three nozzles is better than that in the case of one or two nozzles. Further more, the air injection angle and arrangement of air injection pipes also have great effect on the performance of an air-lift. The proposed research results have guiding significance for engineering application.

Design, Development and Testing of an Air Damper to Control the Resonant Response of a SDOF Quarter-Car Suspension System

An air damper possesses the advantages that there are no long term changes in the damping properties, there is no dependence on working temperature and additionally, it has less manufacturing and maintenance costs. As such, an air damper has been designed and developed based on the Maxwell type model concept in the approach of Nishihara and Asami [1]. The cylinder-piston and air-tank type damper characteristics such as air damping ratio and air spring rate have been studied by changing the length and diameter of the capillary pipe between the air cylinder and the air tank, operating air pressure and the air tank volume. A SDOF quarter-car vehicle suspension system using the developed air enclosed cylinder-piston and air-tank type damper has been analyzed for its motion transmissibility characteristics. Optimal values of the air damping ratio at various values of air spring rate have been determined for minimum motion transmissibility of the sprung mass. An experimental setup has been developed for SDOF quarter-car suspension system model using the developed air enclosed cylinder-piston and air-tank type damper to determine the motion transmissibility characteristics of the sprung mass. An attendant air pressure control system has been designed to vary air damping in the developed air damper. The results of the theoretical analysis have been compared with the experimental analysis.

Study on a Closed-Loop Air-Fuel Control System of Gasoline Engines by Simulation

In order to study the factors that influence the air fuel ratio(A/F), the amplitude and frequency of A/F fluctuation, to reform the control strategy, and to improve the efficiency of three way catalyst(TWC), a model of closed loop control system including the engine, air fuel mixing and transportation, oxygen sensor and controller, etc., is developed. Various factors that influence the A/F control are studied by simulation. The simulation results show that the reference voltage of oxygen sensor will influence the mean value of A/F ratio, the controller parameters will influence the amplitude of A/F fluctuation, and the operating conditions of the engine determine the frequency of A/F fluctuations, the amplitude of A/F fluctuation can be reduced to within demanded values by logical selection of the signal acquisition method and controller parameters. Higher A/F fluctuation frequency under high speed and load can be reduced through software delay in the controller. The A/F closed loop control system based on the simulation results, accompanied with a rare earth element TWC, gives a better efficiency of conversion against harmful emissions.

Flame Propagation Characteristics of Propane-Air Mixture in Ducts with Obstacles

An experimental study on acceleration mechanism of flame propagation of propane-air mixture in ducts with obstacles was conducted. The acceleration mechanism of flame propagation is mainly due to the positive feedback of the turbulence region induced by obstacles for combustion process. It can be seen from the experimental results that the maximum explosion pressure can increase by 20%, the maximum rate of pressure rise can increase by 10 times and the flame propagation velocity can increase by 20 times when obstacles are present.

STUDY OF THE HEAT AND HUMIDITY TRANSFER PROCESSES BETWEEN AIR AND WATER IN THE AIR WASHER

The processes of heat and humidity transfer between air and water are what to be studied mainly in the paper, we put forward some main factors which influence the processes of heat and humidity transfer in the air washer. We come to the conclusion that we can change these main factors to achieve different heat and humidity transfer processes and decide processes of heat and humidity transfer of air and water with the initial temperature of spraying water in the air washer. All these results can make things convenient for the air conditioning management.

Numerical Investigation into the Effect of Air Voids on the Anisotropy of Asphalt Mixtures

The aim of this study is to investigate the asphalt mixture anisotropy of both the modulus and Poisson＇s ratio due to air voids using a discrete element modeling simulation method. Three three-dimensional cubic digital samples of asphalt mixture with different shapes of single air void were built using discrete element software PFC^（3D）. The aggregate gradation, air voids and mastic included in the digital samples were modeled using different contact models, with due consideration of the volumetric fractions of the different phases. Laboratory uniaxial complex modulus test and indirect tensile strength test were conducted to obtain material input parameters for numerical modeling. Simulation of the uniaxial cyclic compressive tests was performed on the three cubic samples loaded in three different directions. Dynamic modulus in three directions and Poisson＇s ratio in six directions were calculated from the compression stress-strain responses. Results show that both the modulus and Poisson＇s ratio are dependent on the preferential orientation of air voids. The anisotropy of the modulus and Poisson＇s ratio increases as the pressure loading on the asphalt mixture increases. Compared to the modulus, Poisson＇s ratio due to air voids has been shown to be more anisotropic. The maximum of Poisson＇s ratio and modulus is shown to be up to 80% and 11% higher than the minimum, respectively.

Solution of idle LBO problem for high FAR aero combustor

The paper sheds light on the idle lean blow off(LBO)problem for high fuel air ratio(FAR)com⁃bustor,which is impossible to be addressed with traditional aero combustor design.A significant improvement in aero combustor design is required to resolve the idle LBO issue.The authors detailed a practical and efficient solu⁃tion,which not only solved the idle LBO issue but also defined the aero-thermal design for high-FAR combustor.The design will usher in a new era of aero combustor.

Performance of Heat Pipe Utilized for Atmospheric Air Heating

The objective of the present experimental work is to investigate the performance of a wrapped screen heat pipe for atmospheric air heating to compare with the limits of this pipe. The experiment was conducted using copper pipe material and acetone as working fluid at different vapor temperatures. The testing also consists of a heater, a blower for heat removal (condenser), temperature measuring device, a vapor temperature probe, acetone charging system, and a vacuum pump. The copper outside diameterof the pipe is 0.022 m, with a total length of 0.6 m. The results showed that the pipe wall temperature (Tw) for a wrapped screen heat pipe has a rapid increase and takes 50 min to reach steady state at (Q = 63 W). The vapour temperature of working fluid increases as the heat load increases at constant air velocity. It was also been found that the range of vapour temperature deceases as the filling ratio increases that means the increasing of the filling ratio results the decrease of the maximum vapour temperature and the variation in the vapour temperature. The best recorded filling ratio is 0.6 which has the lowest vapour temperature at highest heat load. The maximum heat transport limit for this pipe is 80 W and the maximum temperature difference for air is 5。C.

特长跨海公路隧道竖井组协同风量与防排烟设计研究

青岛第二海底隧道首创性地在两管隧道排烟道上纵向间隔设置联络烟道,将南北线烟道联通,以提高通风效率。因此,亟须明确不同竖井组协同风量对联络烟道风量的影响规律,确定最佳的南北线风量配比和两线竖井风量配比。对比不同风量配比对联络烟道风速、利用率的影响,结果表明,南北线风量配比的变化对联络烟道风速的影响较小,但能一定程度上缓解南北两线隧道因两侧风量相同而相互抽吸导致的隧道中心位置风速过低的情况。两线的风量配比对联络烟道风速有较大影响,当两线竖井风量配比由5∶5逐渐变化到2∶8时,联络烟道中间排烟道平均风速由0.89 m/s提升到1.18 m/s,提升幅度约为32.58%,联络烟道利用率由41.18%提升到54.75%,推荐使用不均衡的两线竖井风量配比模式,两线竖井风量配比为2∶8时具有最高的联络烟道利用率。并采用缩尺寸模型试验,验证了该风量配比设计的合理性。

提质培优背景下高职“课堂革命”的实践研究——以汽车专业空燃比传感器检修课程教学为例

在提质培优背景下,以抚顺职业技术学院汽车制造与试验技术专业(以下简称“汽车专业”)的核心课程汽车发动机电控系统检修为研究对象,针对该课程在传统教学中存在的实际问题,选取汽车空燃比传感器检修任务模块,深入开展课堂革命,分别从课程思政、教学设计、教学模式、教学环境和教学评价等方面进行创新研究,探索课堂教学改革新路径,构建“岗课赛证”融合育人模式,设计“三段十步”教学过程,打造有德、有用、有趣、有景、有效“五有”课堂,凸显职业教育教学特色,提高汽车专业人才培养质量和就业质量。

Window Air Conditioners Transition and Restriction in Saudi Arabia

This paper will provide a proposed solution for saving energy consumption due to residential air conditioners by reducing the window air conditioners type which is the most consumed energy and has a big percent of spreading inside KSA than the split type, also it will discuss some restrictions for trading and manufacturing of air conditioner devices inside KSA besides some restrictions on market and buildings to achieve the objective of reducing the consumption of energy which become a big trend in kingdom vision 2030. The results of this suggesting solution will help the decision-makers to start its plan for execution as it has a big difference between using window type from 2022 till 2030 and if we stop its sales and replace by an efficient one of split AC type in energy consumption in addition to CO2 emission reduction and decreasing of energy cost, hence our kingdom can save petroleum raw materials and keeping the environment to become clean from pollutants so that these resources are delivered to successive generations correct and clean as we received them from those before us.

湿空气含湿量对燃气轮机透平叶片复合冷却性能影响的实验与数值研究

为了探究以湿空气作为冷却介质时透平叶片冷却的复合冷却性能,结合实验和数值方法探究了湿空气含湿量对透平叶片湿空气冷却性能的影响。以GE-E 3叶型为基础,建立了带有冲击冷却、U型带肋通道冷却、柱肋冷却、尾缘劈缝以及气膜冷却结构的复合冷却透平叶片。测量了不同冷气与主流质量流量比条件下,采用不同湿空气含湿量的湿空气作为冷却工质时50%叶高处叶片表面温度分布。实验结果表明,在不同的主流温度下,增加湿空气含湿量均能降低叶片表面温度。在主流进口温度分别为473、873 K条件下,采用含湿量分别为163.0、173.8 g/kg的湿空气作为冷却工质时,相较于17 g/kg的湿空气冷却工况,叶片表面冷却效率分别提高了9%~11%和7%~9%,叶片表面温度分别降低了4.1~5.2 K和19.0~21.3 K。数值研究结果表明:带γ-θ转捩模型的SST k-ω模型能够更为准确地预测湿空气冷却时的叶片表面的温度分布;湿空气含湿量的增加能够整体提高叶片表面冷却效率,叶片表面冷却效率的变化在气膜覆盖区域更为显著。