Air Supply System Research Articles

Simulation on air temperature and particle distribution under natural make-up air in indoor environment with a Chinese-style residential kitchen

Kitchen is an important place in Chinese residential building. However, unfavourable thermal environment and unsatisfied air quality occur during cooking. Studies on kitchen environment are experimentally investigated with enough make-up airflow. But mostly normal kitchens are merely installed with a exhaust hood and have not installed air supply system. This work carried out numerical simulation to investigate kitchen indoor environment under natural air make-ups. Air inflow under window fully open, insufficient air inflow from window crack and well-controlled constant inflow volume from window opening are included. Results show that there was a uniform temperature distribution in occupant’s working zone under window open condition. Vertical temperature differences were 4.0 °C under insufficient air make-up. In breathing zone, temperature difference was 6.0 °C and 4.7 °C under uncontrolled and well-controlled airflow, respectively. Mean particle concentration could be largely reduced under controlled and well-organized enough make-up air in kitchen.

Numerical Simulation of Bus Bar Hole Ventilation in Jinghe Dongzhuang Hydropower Station

Based on the boundary conditions obtained from the actual measurements during the infrastructure period of Jinghe Dongzhuang Power Station, a calculation model of the predicted bus bar hole environment was established, and a full-scale numerical simulation of the bus bar hole environment was performed based on CFD to analyze the effect of air supply velocity changes on the temperature and velocity fields in the working area. The ventilation effect is evaluated and compared by calculating the inhomogeneity coefficient and air distribution characteristic index. The study shows that an appropriate increase in air velocity can reduce the thermal impact of the internal heat source on the surrounding environment and can effectively control the air quality in the work area. Considered comprehensively, the work area has better comfort when V/V0 is slightly greater than 1. The research results have some guiding significance for the design of bus bar hole air supply system in Jinghe Dongzhuang Power Station.

Decreasing NOx Emissions by Way of the Staged Fuel Combustion

The purpose of this scientific paper was to analyze the mathematical model built for the staged arrangement of the fuel combustion system and calculate the formation of nitrogen oxides throughout the boiler furnace height for the different distributions of thermal loadings along the full vertical extent of the combustion chamber. The obtained results enable the determination of the overall amount of nitrogen oxides formed in the boiler and it allows us to provide appropriate ecological indices for the boiler when regulating the air concentration in the burner rows. In practice, to suppress the formation of nitrogen oxides we often use such basic methods as low-toxic burners, staged fuel combustion, flue gas recirculation, etc. The analysis of the computations done allows us to draw a conclusion that the operation of the boiler with ecological indices that satisfy standard values of the European Directive 2010/75/EU is only possible for the load below 40 %. After reconstruction of the burner system and adjustment of the air supply system with the observation of above ecological norms the boiler power can be increased up to 80 % using the staged fuel burning with the ensurance of environmental performances during its operation. Computational and experimental data errors varied in the range of 8 % to 12 %. With the increase in the overall chemical incomplete combustion by 40 % to 60 % (q3) these losses are compensated by a decrease in absolute losses due to the boiler aggregate load and the losses through external walls (q5) due to an increase in the boiler power.

Fault-tolerant control through dynamic surface triple-step approach for proton exchange membrane fuel cell air supply systems

Due to complex electrochemical and thermal phenomena, varying operations towards automotive applications, and vulnerable ancillaries in proton exchange membrane fuel cells (PEMFCs), fault diagnosis and fault-tolerant control (FTC) design have become important aspects to improve the reliability, safety and performance of PEMFC systems. This paper presents a novel FTC scheme for automotive PEMFC air supply systems via coordinated control of the air flow rate and the pressure in cathodes. A dynamic surface triple-step approach is first proposed considering nonlinear dynamics and the multi-input multi-output (MIMO) property, which combines the advantage of dynamic surface control in avoiding an “explosion of complexity” and the advantage of triple-step control in guaranteeing a simple structure and high performance. The normal case, the faulty case at the supply manifold and the faulty case in the back pressure valve are considered in the FTC design, with the stability of the overall system proved using Lyapunov methods. MATLAB/Simulink simulations with a high-fidelity PEMFC model verify the effectiveness of the proposed FTC scheme in regulating the air flow rate and oxygen excess ratio and maintaining the pressure of the cathode at a desired level even under faulty conditions.

Novel Hybrid Control Scheme of a Proton Exchange Membrane Fuel Cell Air Supply System

A hybrid control scheme of the fuel cell air supply system based on model predictive control (MPC) and proportional integral differential (PID) control is proposed for adjusting the oxygen excess ratio at a given setpoint in this paper. In the proposed scheme, the cooperative control of air compressor and back pressure valve in the fuel cell air supply system is realized by MPC. When the system is in steady state under the MPC, PID is introduced, so that the steady‐state error, which is caused by the mismatch between the control model in MPC and the controlled system during MPC control, can be eliminated. To reduce the mismatch between the control model and the controlled air supply system, back propagation neural network and look‐up table method based on bilinear interpolation are used to calculate the output air flow rate and efficiency of the air compressor in the air supply system. Simulation results show that the proposed control scheme has a better performance compared with proportional integral control, active disturbance rejection control, and single MPC. In addition, the proposed control scheme also shows good fault tolerance in the case of air supply system failure.

APPLICATION OF FUZZY ANALYTIC HIERARCHY PROSES FOR ERROR DETECTION OF AUXILARY SYSTEMS OF SHIP MAIN DIESEL ENGINES

Ship engine room has a structure which has to meet a number of needs with regard to administrative conditions. Therefore, when the complicated structure of engine room are considered, even a simple mechanical failure, if no measures taken abruptly, grows into irreversible condition, causing losses that cannot be compensated. A well-qualified ship engine conductor along with an effective error detection system is needed to detect failure and act immediately against any engine impairments possible. This study aims to manage troubleshooting in main engine auxiliary systems which cover cooling, lubricating and cooling oil and fuel systems. The study is also thought to be a good reference for maintenance processes for marine engineering operators. Breakdown of main engine equipment are examined and troubles hooting program is developed for using Fuzzy Analytic Hierarchy Process (F-AHP) determine solution methods and causes of such breakdowns. In this paper, a fuzzy Multi Criteria Decision Making (MCDM) methodology was proposed to determine the most effected system of the ship main diesel engine. The results showed that fuel system was the most effected alternative, as being followed subsequently by cooling system, governor system, air supply system and oiling system. The results were based upon the opinions of three experts groups who ranked the ship main diesel engine systems alternatives according to twenty-nine criteria expert selected.

Обеспечение ресурса и надежности клапанных механизмов на разных этапах развития двигателей внутреннего сгорания

The main directions of the development of internal combustion engines (ICE) are to increase the specific power and efficiency, as well as to meet the ever-tightening environmental standards. From the very beginning, the improvement of the internal combustion engine was accompanied by an increase in the parameters and design development of air supply and gas exchange systems, including valve mechanisms and corresponding actuators. The process of developing an internal combustion engine based on changes in the design, the level of forcing, and the technologies used should be divided into four stages.

Coordinated Control of the Fuel Cell Air Supply System Based on Fuzzy Neural Network Decoupling.

In order to achieve the goal of carbon neutralization, hydrogen plays an important role in the new global energy pattern, and its development has also promoted the research of hydrogen fuel cell vehicles. The air supply system is an important subsystem of hydrogen fuel cell engine. The increase of air supply can improve the output characteristics of a fuel cell, but excessive gas supply will destroy the pressure balance of the anode and cathode. In the actual operation of a proton-exchange membrane fuel cell, considering the load change, it is necessary not only to ensure the stability of reactor pressure but also to meet the rapid response of inlet pressure and flow in the process of change. Therefore, the coordinated control of the two is the key to improving fuel cell output performance. In this paper, the dynamic model of the intake system is built based on the mechanism and experimental data. On this basis, the double closed-loop proportion integration differentiation (PID) control and feedforward compensation decoupling PID control are carried out for the air supply system, respectively. Then, the fuzzy neural network decoupling control strategy is proposed to make up for the shortcomings that the double closed-loop PID cannot achieve decoupling and the feedforward compensation decoupling does not have adaptability. The results show that the fuzzy neural network control can realize the decoupling between air intake flow and pressure and ensure that the air intake flow and pressure have a good follow-up, and the system’s response speed is fast.

Energy balance of the airflow boundary layer in the brake disc ventilation

Airflow through the brake disc ventilation causes the formation of a boundary layer at the walls. It affects both the dynamic processes related to air exchange in the space between the walls and thermal processes associated with air insulation of the heated surfaces of the ventilation ducts. The present paper aims to develop a model for calculating plane airflow in a ventilation duct in polar coordinates. Using the Navier-Stokes equations and the equations of the energy balance of the airflow boundary layer, we succeeded in determining the elements that affect the intensity of changes in the air masses in the boundary layer and the elements that are responsible for the thermal conductivity of the thermal boundary layer of the airflow. Besides, we obtained an energy balance equation, which takes into account the enthalpy and thermodynamic parameters of the thermal boundary layer, as well as found the possibilities of influencing the heat exchange processes by minimizing factors of the heat-insulating boundary layer. Finally, we specified the dependence of the boundary layer temperature on the temperature of the walls of the brake disc ventilation. The obtained dependences lay the ground for formulating variants of the influence on the heat-insulating boundary layer of the airflow, namely, the design of a forced air supply system at different angles of attack into the ventilation cavity of the brake disc or the manufacture of ventilation ducts with complex geometry.

Performance study of centrifugal air compressor for proton exchange membrane fuel cell systems

AbstractAir supply systems are essential subsystems in proton exchange membrane (PEM) fuel cell systems. Compressors are the key devices of air supply systems that greatly influence the characteristics of fuel cells. The simulation and experimental researches on a small centrifugal compressor with high rotation speed have been presented in this paper. Firstly, the input parameters of a compressor are obtained based on the output power and operating pressure of PEM fuel cells. Then, a prototype of small centrifugal compressors applied in PEM fuel cells is designed, simulated with the computational fluid dynamics (CFD) method, and tested in actual working conditions. Finally, the simulation results show that the internal flow in compressors affects the performance strongly. The discharge pressure of the simulation is close to the test data in the studied working conditions, and the maximum error is less than 6%.

Thermal Comfort and Energy Analysis of a Hybrid Cooling System by Coupling Natural Ventilation with Radiant and Indirect Evaporative Cooling

A hybrid cooling system which combines natural ventilation with a radiant cooling system for a hot and humid climate was studied. Indirect evaporative cooling was used to produce chilled water at temperatures slightly higher than the dew point. With this hybrid system, the condensation issue on the panel surface of a chilled ceiling was overcome. A computational fluid dynamics (CFD) model was employed to determine the cooling load and the parameters required for thermal comfort analysis for this hybrid system in an office-sized, well-insulated test room. Upon closer investigation, it was found that the thermal comfort by the hybrid system was acceptable only in limited outdoor conditions. Therefore, the hybrid system with a secondary fresh air supply system was suggested. Furthermore, the energy consumptions of conventional all-air, radiant cooling, and hybrid systems including the secondary air supply system were compared under similar thermal comfort conditions. The predicted results indicated that the hybrid system saves up to 77% and 61% of primary energy when compared with all-air and radiant cooling systems, respectively, while maintaining similar thermal comfort.

RE-DESIGN SOLID BOX AND AIR BAG CONFIGURATIONS ON UNSINKABLE SMALL PASSENGER BOAT

Previous works were conducted by the authors concerning the performance of unsinkable small passenger boat. The boat was designed and constructed in model scale and full-scale ship. The model was tested in tank and full-scale ship was tested at open sea to verify the design parameters. The research is continued in order to improve the boat performance. A re-design process was executed in order to modify the boat, air bags and centralised air supply system. The modified unsinkable boat was tested with the full passengers at sea for floating and sinking purposes. The required volume of solid boxes and air bags on board and outside are1.12 m3, 0.563 m3 and 0.213 m3 respectively. The result of test at sea showed that the modified boat was floating, unsinkable at static condition even with full water in board and keep running with flooding conditions. It is found that the boat is stable due to its positive value of GMt and GZ. The recommendation was made for future application for the stakeholders.

An adaptive sliding mode observer based near-optimal OER tracking control approach for PEMFC under dynamic operation condition

Tracking control of oxygen excess ratio (OER) is crucial for dynamic performance and operating efficiency of the proton exchange membrane fuel cell (PEMFC). OER tracking errors and overshoots under dynamic load limit the PEMFC output power performance, and also could lead oxygen starvation which seriously affect the life of PEMFC. To solve this problem, an adaptive sliding mode observer based near-optimal OER tracking control approach is proposed in this paper. According to real time load demand, a dynamic OER optimization strategy is designed to obtain an optimal OER. A nonlinear system model based near-optimal controller is designed to minimize the OER tracking error under variable operation condition of PEMFC. An adaptive sliding mode observer is utilized to estimate the uncertain parameters of the PEMFC air supply system and update parameters in near-optimal controller. The proposed control approach is implemented in OER tracking experiments based on air supply system of a 5 kW PEMFC test platform. The experiment results are analyzed and demonstrate the efficacy of the proposed control approach under load changes, external disturbances and parameter uncertainties of PEFMC system.

Analysis of Optimal Oxygen Excess Ratio and Nonlinear Tracking Control of Vehicle PEMFC Air Supply System

To a large extent, the efficiency and durability of the proton exchange membrane fuel cell (PEMFC) depend on the effective control of air supply system. However, dynamic load scenarios, internal and external disturbances, and the characteristics of strong nonlinearity make the control of complex air supply systems challenging. This paper mainly studies the modeling of PEMFC air supply system and the design of a nonlinear controller for oxygen excess ratio tracking control. First, we analyze and calibrate the system’s optimal oxygen excess ratio control target and explore how the system temperature and humidity impact it, respectively; second, a second-order affine oriented control model which can represent the static and dynamic characteristics of the air supply system is derived, and a disturbance observer is designed to estimate and compensate the “lumped error” online. Then, aiming at the problem of unmeasurable cathode pressure, a state observer based on Kalman optimal estimation algorithm is proposed to realize the real-time estimation of cathode pressure; finally, a dynamic output feedback control system based on observer and backstepping nonlinear controller is proposed, and the comparison and evaluation of two control strategies based on constant oxygen excess ratio tracking and optimal oxygen excess ratio tracking are carried out. The simulation results show the effectiveness and superiority of the designed control system compared with the reference controller.

Улучшение динамических свойств среднеоборотного дизеля при использовании регулируемого турбонаддува

The article presents the results of a computational study of the possibilities of improving the dynamic properties of diesel engines by using a controlled turbocharger. A promising medium-speed diesel engine 12 ChN 26.5 / 31, operating in ship conditions was researched. A mathematical model has been developed for a combined engine as a part of a complex adaptive control system with channels for regulating the speed of rotation and turbocharging. The computer model was implemented in the MATLAB / Simulink software package. Calculated transient processes of the working process parameters of a diesel engine were considered for two methods of turbocharging control: multistage turbocharging and variable geometry turbines – turbines with a variable position of the guide vanes. The effect of pneumatic correction of the fuel supply on the dynamic characteristics of the engine under consideration was studied. The obtained results were analyzed. A comparison of various options for regulating the air supply system in terms of the efficiency of improving the dynamic properties of diesel engines was performed.

Feedforward-decoupled closed-loop fuzzy proportion-integral-derivative control of air supply system of proton exchange membrane fuel cell

Effective control strategies of air supply system are the key to guaranteeing reliability and efficiency of the operation of the proton exchange membrane fuel cell (PEMFC) system. The novelty of this article is to design a fuzzy proportion-integral-derivative (PID) controller for the PEMFC air supply system combining the feedforward decoupled method. Aiming at strong coupling of parameters in the air supply system, we have proposed a feedforward decoupled controller to achieve independent control of air flow and pressure, so that the entire system can get better control effect. Aiming at time-varying, hysteresis, and randomness of interference in the air supply system, we have designed a fuzzy-PID controller based on the decoupled controller to achieve better dynamic response and stability, so that the possibility of air starvation can be reduced and the stack durability can be improved. The step load test reveals that the time to reach steady state, the overshoot, and the steady-state error are much smaller under the decoupled fuzzy-PID control compared that under the decoupled PID control. The New European Driving Cycle (NEDC) test further verifies that the system with the decoupled fuzzy-PID controller can quickly follow the variable load demand without system response oscillation and steady-state error.

Investigation of inter-zonal heat transfer in large space buildings based on similarity: Comparison of two stratified air-conditioning systems

Stratified air-conditioning (STRAC) has been deployed in large space buildings to achieve vertical thermal stratification with significant energy-saving potential. This research focuses on two typical STRAC systems: floor-level sidewall air-supply system (FSAS) and nozzle sidewall air-supply system (NSAS). By employing experiment and CFD methods, airflow pattern and heat transfer between the unoccupied and occupied zone under the two air supply systems are investigated in a reduced-scale laboratory. The geometric models of the prototype building, with a geometrical scaling factor of 4:1, are established according to similarity principles and studied by CFD simulation. The results demonstrate that the two scales have similar indoor thermal performances. The numerical simulation results of the prototype building provide and compare commonly used inter-zonal heat transfer coefficients of actual large space buildings with the two typical STRAC systems. For FSAS, heat conduction caused by temperature gradient dominates the inter-zonal heat transfer. In NSAS, both heat conduction due to temperature gradient and heat convection due to airflow contributes equally to this heat transfer. The inter-zonal heat transfer coefficient Cb is affected by the airflow pattern and zonal division, and closely associated with local turbulence intensity.

Modeling and Fuzzy Feedforward Control of Fuel Cell Air Supply System

As an important part of the fuel cell subsystem, the air supply system of the proton exchange membrane fuel cell (PEMFC) plays an important role in improving the output performance and durability of fuel cells. It is necessary to control the oxygen excess ratio of fuel cell systems in the process of variable load, preventing the oxygen starvation in the loading process and excessive parasitic power consumption caused by oxygen saturation. At this time, the modeling of fuel cell systems and the development of control strategies are critical. The development of a control strategy depends on the construction of the control model. Aiming at the difficulty of air supply system modeling, this paper uses radial basis function (RBF) neural network and state equation method to establish the dynamic model of air supply systems. At the same time, PID, fuzzy logic plus PID (FL + PID), feedforward plus PID (FF + PID), fuzzy feedforward plus fuzzy PID (FF + FLPID) control strategy are proposed to control the oxygen excess ratio of the system. The simulation results show that fuzzy feedforward plus fuzzy PID (FF + FLPID) has the best effect and the oxygen excess ratio can be followed in 1 s.

Data-Driven Control for Proton Exchange Membrane Fuel Cells: Method and Application

A data-driven optimal control method for an air supply system in proton exchange membrane fuel cells (PEMFCs) is proposed with the aim of improving the PEMFC net output power and operational efficiency. Moreover, a marginal utility-based double-delay deep deterministic policy gradient (MU-4DPG) algorithm is proposed as a an offline tuner for the PID controller. The coefficients of the PID controller are rectified and optimized during training in order to enhance the controller’s performance. The design of the algorithm draws on the concept of marginal effects in Economics, in that the algorithm continuously switches between different forms of exploration noise during training so as to increase the diversity of samples, improve exploration efficiency and avoid Q-value overfitting, and ultimately improve the robustness of the algorithm. As detailed below, the effectiveness of the control method has been experimentally demonstrated.

Tailored Centrifugal Turbomachinery for Electric Fuel Cell Turbocharger

Hydrogen fuel cell technology is identified as one option for allowing efficient vehicular propulsion with the least environmental impact on the path to a carbon-free society. Since more than 20 years, IHI is providing charging systems for stationary fuel cell applications and since 2004 for mobile fuel cell applications. The power density of fuel cells substantially increases if the system is pressurized. However, contaminants from fuel cell system components like structural materials, lubricants, adhesives, sealants, and hoses have been shown to affect the performance and durability of fuel cells. Therefore, the charging system that increases the pressure and the power density of the stacks inevitably needs to be oil-free. For this reason, gas bearings are applied to support the rotor of a fuel cell turbocharger. It furthermore comprises a turbine, a compressor, and, on the same shaft, an electric motor. The turbine utilizes the exhaust energy of the stack to support the compressor and hence lower the required electric power of the air supply system. The presented paper provides an overview of the fuel cell turbocharger technology. Detailed performance investigations show that a single-stage compressor with turbine is more efficient compared to a two-stage compressor system with intercooler. The turbine can provide more than 30% of the required compressor power. Hence, it substantially increases the system efficiency. It is also shown that a fixed geometry turbine design is appropriate for most applications. The compressor is of a low specific speed type with a vaneless diffuser. It is optimized for operating conditions of fuel cell systems, which typically require pressure ratios in the range of 3.0.