Air Supply System Research Articles

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.

Evaluation of antibacterial and antiviral barrier function of the conceptual model of a pneumatic helmet

Annotation. The global pandemic has necessitated the development of new respiratory protective equipment that seems to combine reliability and ergonomics. The article tests an innovative conceptual model of a pneumatic helmet with a laminar air supply system for its permeability to bacteria Micrococcus luteus and antistaphylococcal bacteriophages. The latter were fed in the form of an aerosol to the external filter of the working device with subsequent titration and seeding. Evaluation of bacterial infection is performed by counting the units that form colonies by multiplying the above indicator by the degree of dilution. The presence of bacteriophages and their number was determined by the Grace method with the calculation of plaque-forming units in the culture of Staphylococcus aureus. Statistical processing of the results was performed on a personal computer Intel Core i3 using one- and multi-factor analysis of variance (licensed software packages Microsoft Office 2016 and Statistica 10). In the full and partial configuration of the device (if there is only an external or internal filter), the penetration of microorganisms into the internal space is not detected. The results of the study confirmed the reliability of the protection system for 6 hours of continuous operation, which makes the conceptual model of a pneumatic helmet a more ergonomic alternative to the usual means of respiratory protection.

Air flow and pressure optimization for air supply in proton exchange membrane fuel cell system

To study the air supply of proton exchange fuel cell (PEMFC) system to avoid air starvation, a proton PEMFC system model mainly including the stack (30 kW, 240 cells, 190 cm2 activation area) and air supply system is developed. Model's average relative errors of output mass flow and pressure are 2.9% and 0.756% respectively. Model' saverage relative error of output voltage is 2.678%. Subsequently, the influence of operating parameters (air excess ratio and air pressure) on output performance (dynamic response of stack voltage and on net output power of PEMFC system) is analyzed. When air excess ratio is 4 and pressure is 1.7 bar respectively, voltage's dynamic response reaches the best level. Optimal pressure to output maximum net power is always located in lower value region and optimal flow shows a tendency to be gradually larger as current increases. Then the optimization model to determine working points of each parameter aiming at comprehensively improve voltage's dynamic response and net output power of PEMFC system simultaneously is presented. Based on this, an optimized air supply strategy of replenishing air upon loading is innovatively proposed. This research can be further used to guide the development of control strategy of air supply.

Coordinated control of gas supply system in PEMFC based on multi-agent deep reinforcement learning

In proton exchange membrane fuel cells (PEMFCs), the hydrogen supply system and air supply system jointly impact the output characteristics, and there is a coordination problem between these two systems. To solve this coordination problem, an intelligent control framework is presented that considers the coordination between the air flux controller and hydrogen flux controller in PEMFCs, and an ensemble imitation learning multi-trick deep deterministic policy gradient (EILMMA-DDPG) is advanced for this framework. The algorithm proposed here complies with an ensemble imitation learning policy, i.e., exploiting multiple reinforcement learning explorers that contain actor networks to perform distributed exploration in the environment, thereby improving the exploration efficiency. Moreover, a control algorithm explorer that contains various conventional control algorithms is presented to create model samples over a range of scenarios in an attempt to address sparse rewards and improve the training efficiency in conjunction with an experience probability replay mechanism. Next, multiple tricks are adopted to improve the overestimated Q value. Finally, a model-free intelligent control algorithm capable of coordinating controllers and exhibiting a better global searching ability is developed. In addition, the proposed algorithm is adopted in the control framework of the air and hydrogen supply system in PEMFCs. Furthermore, as revealed from the simulated results, the proposed intelligent control framework can more effectively control the oxygen excess rate (OER) and output voltage.

Investigation of the influence of the configuration of the fire furnace chamber on the temperature regime during the implementation of tests for fire resistance

The issue related to the conditions for creating the required temperature regime of fire when testing structures for fire resistance has not been studied in detail up to now. That necessitated determining the technical conditions under which it is possible to comply with the standard temperature regime of fire in the fire chamber of the furnace. The influence of the design parameters of the fire furnace chamber on the condition of compliance with the standard fire temperature regime when tested for fire resistance has been established. One of the most effective methods for examining such an impact is computer simulation. A computer model of the fire furnace was built on the basis of a comprehensive analysis and earlier work on the study of such furnaces, taking into consideration technical characteristics, in particular, geometrical parameters, fuel and air supply systems. The obtained research results are a prerequisite for scientific substantiation of the design parameters of fire furnaces and their engineering systems, which is necessary to comply with the standard temperature regime of fire in the furnace fire chamber. This makes it possible to provide the necessary conditions for testing building structures for fire resistance in compliance with the requirements of the relevant standards. The computer model constructed makes it possible to create the necessary temperature regime in the fire chamber of the furnace (in this study, the standard temperature of fire). As a result of the study, the technical parameters of the fuel supply and ventilation system were determined, which ensure compliance with the standard temperature regime in the fire chamber of the furnace. That makes it possible to build an automated complex of the testing process for fire resistance of building structures. In addition, the data obtained can be the basis for the design of such fire furnaces with the ability to comply with different fire temperature regimes without the intervention of the operator.

Ultrafine particle levels measured on board short-haul commercial passenger jet aircraft

BackgroundAirline crew members report adverse health effects during and after inhalation exposure to engine oil fumes sourced to the air supply system onboard commercial and military aircraft. Most investigations into the causal factors of their reported symptoms focus on specific chemical contaminants in the fumes. The adverse health effects reported in aircrew exposed to the aircraft air supply, bled unfiltered off the engine or Auxiliary Power Unit (APU) may be related to particulate exposures, which are widely known to effect health. While oil contaminates the aircraft air supply, some suggest that this will only occur when there is a bearing seal failure, others document that there is low level oil contamination of the air supply during normal engine operation. This brief pilot study explores whether particulate exposure may be associated with the normal engine/APU and air supply operation and to therefore increase the understanding that UFP exposures may have on crew and passengers.MethodsAn ultrafine particle counter was utilised by an experienced airline captain in the passenger cabin of four short-haul commercial passenger aircraft. All flights were under 90 min on aircraft from two different carriers ranging from 7 months to 14 years old.ResultsUFP concentrations showed maximum concentrations ranging from 31,300 to 97,800 particles/cm3 when APU was selected on as a source of air on the ground and with engine bleed air and the air conditioning packs selected on during the climb. In 2 of the 4 flights the peaks were associated with an engine oil smell. Increases in UFP particle concentrations occurred with changes in engine/APU power and air supply configuration changes.ConclusionsThis study identified increases in UFP concentrations associated with engine and APU power changes and changes in air supply configuration. These results correlated with times when engine and APU oil seals are known to be less effective, enabling oil leakage to occur. The concentrations reached in the passenger cabins exceeded those taken in other ground-based environments. UFP exposures in aircraft cabins during normal flight indicates there will be health consequences for long serving aircrew and some passengers.

Thermal and mechanical improvement of the air supply system of a turbocharged piston engine

A method of thermomechanical improvement of pulsating air flows in the intake system of a turbocharged piston engine is described. The main objective of this study is to develop a method for suppressing the rate of heat transfer to improve the reliability of a piston turbocharged engine. A brief review of the literature on improving the reliability of piston engines is given. Scientific and technical results were obtained on the basis of experimental studies on a full-scale model of a piston engine. The hot-wire anemometer method was used to obtain gas-dynamic and heatexchange characteristics of gas flows. Laboratory stands and instrumentation facilities are described in the article. The data on gas dynamics and heat exchange of stationary and pulsating air flows in gas-dynamic systems of various configurations as applied to the air supply system of a turbocharged piston engine are presented. A method of thermomechanical improvement of flows in the intake system of an engine based on a honeycomb is proposed in order to stabilize the pulsating flow and suppress the intensity of heat transfer. Data were obtained on the air flow rate and the local heat transfer coefficient both in the exhaust duct of the turbocharger compressor (i.e., without a piston engine) and in the intake system of a supercharged engine. A comparative analysis of the data has been carried out. It was found that the installation of a leveling grid in the exhaust channel of a turbocharger leads to an intensification of heat transfer by an average of 9%. It was found that the presence of a leveling grid in the intake system of a piston engine causes the suppression of heat transfer within 15% in comparison with the baseline values. It is shown that the use of a modernized intake system in a diesel engine increases its probability of failure-free operation by 0.8%. The data obtained can be extended to other types and designs of air supply systems for heat engines.

APPLICATION OF EXERGETIC METHOD FOR EVALUATION OF PROCESS PERFECTION IN DIESEL ENGINE SUPERCHARGING SYSTEM

One of the most important trends of the modern combat vehicles is increasing their mobility for the security of the crew and for fast movement in different types of terrain. Compliance with these criteria is ensured by the engine of the armored vehicle. The competitiveness of domestic engines for armored vehicles should be ensured by the creation of new structures, their constant modernization and further improvement of performance. One of such engines is a forced diesel engine 6DN12/2x12 with a capacity of 1100 kW. In order to improve its performance and increase the level of forcing, it is proposed to improve the air supply system of the engine. Evaluating the effectiveness of the system can identify nodes that need changing design parameters. Therefore, such a qualitative analysis also indicates the feasibility and the possibility of further modernization of the system design. The qualitative analysis of the turbocharger is carried out on the basis of exergy method, which allows identifying sources of energy losses in the system design and determines the degree of perfection of processes. The application of the exergy method is due to the purpose of determining the reserves to improve the efficiency of the turbocharger elements, the magnitude of the supplied exergy and exergy efficiency in the nodes of the air supply system. According to the method, an exergy scheme of the supercharging system was constructed, on the basis of which the energy-exergy balance of each compressor unit was derived. The results of the analysis allowed to determine the parameters of the flow of the working fluid in the characteristic sections of the compressor and turbine and exergetic efficiency of the supercharging system. The calculated data obtained by exergetic analysis provide an estimate of the distribution of energy losses and allow determining the areas for further improvement of the air supply system and providing an opportunity to choose such design parameters that achieve the most effective improvement of the system.

Hybrid diagnosis method for initial faults of air supply systems in proton exchange membrane fuel cells

Fault diagnosis technology has been developed to improve the reliability of fuel cell systems in pursuit of successful commercialization. In this study, a hybrid fault diagnosis method is proposed to improve diagnosable fault magnitudes and diagnostic accuracy. Six types of faults in the air supply system of a proton exchange membrane fuel cell system were therefore defined and diagnosed according to the relevant components and locations as actuator, sensor, and piping faults. The proposed method applies an artificial neural network classifier as a data-based diagnostic tool within a model-based diagnosis method that relies upon residual patterns to address the limitations of the model-based diagnosis method (insufficient accuracy for initial fault diagnosis) and the data-based diagnosis method (need for a large dataset to generate a classifier). The proposed method is shown to improve the diagnostic accuracy and decrease the diagnosable fault magnitude compared to solely model-based and data-based methods. Moreover, the proposed method enables a faster diagnosis of air supply system faults, preventing loss of system efficiency and stack degradation. By providing fast and accurate diagnoses, the proposed method is expected to help develop an effective fuel cell health management system.

EVALUATION AND ANALYSIS OF THE SUSTAINABLE WASTE-TO-ENERGY SYSTEM PERFORMANCE FOR THE POULTRY FARM

Poultry litter is one type of biomass and waste generated from the poultry farms. However, excess land application of poultry litter caused eutrophication problems of surface waters coming from the watershed and destroyed the aquatic ecology. Co-combustion of poultry litter and coal were widely studied in fluidized bed combustor as an alternative disposal method during last two decades. However, there are severe environmental problems (i.e., gaseous emissions) and public health impact associated with the poultry litter and coal co-combustion process. In this study, poultry litter and natural gas co-combustion was investigated in the lab-scale waste-to-energy system to provide a sustainable and cost-effective disposal route for poultry farms. This waste-to-energy system integrates the Stirling Engine (SE), Shell-Tube Heat Exchanger (STHE) and the lab-scale Swirling Fluidized Bed Combustor (SFBC) with other systems (e.g., cyclone, air supply system, fuel feeding system). Measures of heat transfer effect, electricity output and gas emissions levels were used to evaluate the lab-scale waste-to-energy system performance. Results indicated that lab-scale waste-to-energy system can produce electricity (close to 1 kW) and hot water (57.2°C) while reducing NOx and SO2 emissions during the poultry litter and natural gas co-combustion process. In addition, energy flow analysis indicated that SE and STHE system might use 14.7% and 21.0% of total energy input in fuels, respectively, to generate useful energy. In addition, a sustainable life cycle of poultry litter was built and suggested to process poultry wastes in the poultry farms.

Full-scale experimental investigation on smoke spreading and thermal characteristic in a transversely ventilated urban traffic link tunnel

Transverse ventilation system is an effective method to control the smoke propagation in tunnel fires. In the current research, 14 full-scale burning tests were conducted in an urban traffic link tunnel in Chongqing, China. Temperature and velocity profiles, as well as the smoke stratification characteristics affected by the transverse ventilation were successively explored. Results underlined that 1) Fire location and air supply system have limited influence on the induced air velocity while the induced air velocity slightly decreased as heat release rate increased. When more smoke outlets were activated, the induced air velocity increased; 2) Ceiling temperature was very sensitive to the fire location, smoke extraction, and air supply system. A distinct temperature decrease was observed when (a) the fire moved closer to the outlet; (b) more outlets were activated; (c) supply vents near the fire were opened; 3) Thermal stratification could be well predicted by the temperature quotient proposed by Newman. Considering the transverse ventilation, the relationship between temperature ratio ΔTcf/ΔTavg and Froude number Fr accounting for the transverse ventilation was modified based on the present measurements.

Data-driven reconstruction of interpretable model for air supply system of proton exchange membrane fuel cell

Appropriate air supply system controller is of great significance to improve the performance of proton exchange membrane fuel cell. Most of controllers rely on the high-precision, simple, and interpretable model. It is particularly important to establish the model for the fuel cell air supply system. Since the high-precision physically interpretable control-oriented model can provide an understanding of the underlying phenomena apart from computational tractability for aerodynamic problems. Data-driven sparse identification based on auto-encoder method is proposed to establish the model. It can be divided into the four steps. Firstly, collect data from a simulation model and the actual fuel cell system, and auto-encoder network is used to discover a coordinate transformation into a reduced space. Secondly, dictionary library is constructed from candidate terms based on system analysis. Thirdly, air supply model reconstruction problem is transformed into a sparse identification problem. Finally, the developed model is verified by two datasets. Compared with other methods, the results show that mean absolute error and root mean squared error of the three variables for proposed method are the smallest under both simulation data and real data. And the reconstruction results perfectly agree with the original simulation and the real data. Especially, the proposed method can be easily extended to other system modeling studies, such as the hydrogen supply system model and thermal management system model of the fuel cell system.

Research on silent steady flow quick closing check valve for rail vehicle

a kind of air valve which can prevent gas backflow is used in the track air supply system. Check valve is the basic component of fluid control engineering, which is widely used. It plays a role in determining the direction of fluid flow, protecting other fluid machinery and pipeline safety by preventing the reverse flow of fluid[1]. For example, drilling tool check valves commonly used in oil fields include arrow type valve, float valve and input type check valve [2-3]. The check valve developed by our company is mainly used for gas medium, suitable for high-pressure gas transmission, and plays the role of preventing gas backflow.

An adaptive approach to duct optimization of an industrial boiler air supply system using airfoils

The purpose of this paper is to examine the pressure drop caused by placing an airfoil at different angles of attack in the straight part of the rectangular air duct, as the first step of investigating the possibility of using a staggered cascade of airfoils for gradual deflection of the air-flow in radial elbows of an air supply system used in industrial boilers. The initial problem was approached by using the commercial CFD code based on the finite volume method to numerically simulate a 2-D incompressible turbulent flow and by conducting direct experimental measurements in the wind tunnel. The results of CFD simulations have been compared to experimentally measured data for two considered cases of inlet velocities and five different angles of attack. Numerical solutions show an adequate level of agreement with experimental measurements. The obtained results indicate the possibility of using a staggered cascade of airfoils for gradual deflection of the air-flow.