Air Supply Method Research Articles

Experimental study on the influence of flexible structure and gas supply method on the characteristics of aerostatic tilting-pad bearing

Purpose This paper aims to propose novel flexible structure-supported tilting-pad aerostatic bearings and to improve operational stability and vibration reduction of aerostatic bearings. Design/methodology/approach The authors established an aerostatic bearing-rotor test rig and designed two aerostatic tilting-pad bearings with different flexible support structure and an ordinary aerostatic tilting-pad bearing and then examined their effects in dynamic performance to assess the vibration reduction performance of different flexible structures. Furthermore, the authors proposed three gas supply methods and conducted experiments to study the influence of gas supply methods in the performance of bearings. Findings The experimental results show that among the three structures, the double-layer flexible structure-supported tilting-pad bearing demonstrates outstanding vibration damping performance and it significantly enhances the operational stability of the bearing-rotor system. Furthermore, the experimental results indicate that the gas supply method has a significant impact on the performance of the aerostatic bearing. There is a certain pressure difference between the gas supply pressure for the loading pads and that for the nonloading pads, which is advantageous for increasing the operational stability and reducing system vibration. Originality/value The authors designed novel flexible aerostatic tilting-pad journal bearing structures, which can enhance the operational stability and reduce vibrations of the bearing. Additionally, this article proposes an air supply method advantageous for increasing the stability of the bearing and reducing system vibrations.

Simulation and optimization design of air distribution in a cigarette production factory

Air-conditioning energy consumption accounts for a significant proportion of the total energy usage in large commercial buildings. This study utilizes computational fluid dynamics (CFD) to examine the airflow distribution in a cigarette factory with a high ceiling. Numerical simulations were performed to assess the effectiveness of various air supply methods. Using FLUENT, the researchers analyzed the uniformity of airflow, temperature and humidity fields under summer conditions. The findings indicate that employing an upper supply and lower return air method can decrease air-conditioning energy consumption by 7.25%. Field measurements were carried out to validate the numerical simulations, with the measured values used as initial parameters. The average deviation between the measured and simulated temperature and humidity in critical work areas was within 2%. The comparative analysis of the simulation and measurement results confirms the reliability and effectiveness of airflow organization simulations in large commercial buildings. These results offer a scientific foundation and computational guidance for designing and implementing energy-efficient upgrades to air-conditioning systems in similar industrial facilities.

New Makeup Air Method through Ceiling for Kitchen Ventilation in Severely Cold Regions and Its Effect on Air Environment

Severely cold weather reduces the willingness of residents to open windows while cooking. This results in an insufficient replenishment of makeup air and a reduction in the range hood discharge capacity. For an effective trade-off between indoor air temperature maintenance and air quality aggravation in winter, a new makeup air supply method (ceiling makeup air) was proposed and established both experimentally and numerically. The improvements in the kitchen air environment during cooking were studied through experimental tests and CFD simulations, considering different makeup air arrangements. The results reveal that the ceiling makeup air scheme can significantly reduce the concentration of PM2.5 compared with the cracks makeup air scheme (wherein the kitchen window and door are closed). Moreover, it increased the indoor temperature by over 11.9 °C compared with the open window makeup air scheme. The average relative error between the experimental and simulated data was within 6.1%. Among the considered factors, the size of the air inlet had the largest impact. This was followed by the layout, size, and shape of the ceiling inlets. The ceiling makeup air scheme demonstrated the potential for improving residential kitchen air environments in severely cold regions.

Experimental evaluation of the flow structure in a vertical conical diffuser with different air supply methods

Experimental evaluation of the flow structure in a vertical conical diffuser with different air supply methods

Simulation study on the impact of heat source intensity on the inhaled air quality of an innovative personalized air supply method

Abstract To improve the local microenvironment of the human body in industrial buildings with strong heat sources, this paper proposes a new personalized air supply method based on the attachment effect. The numerical simulation method is used to study the influence of heat source intensity on the inhaled air quality in this paper. Studies have shown that when the air supply speed is less than or equal to 0.5 m/s, the fresh air ratio decreases as the Gr number of the heat source increases. When the air supply speed is greater than or equal to 0.7 m/s, the fresh air ratio increases as the Gr number of the heat source increases.

Research on Non-isothermal Jet Air Supply Method for Human Thermal Comfort Regulation in Commercial Vehicle Based on Localized Air Conditioning System

Research on Non-isothermal Jet Air Supply Method for Human Thermal Comfort Regulation in Commercial Vehicle Based on Localized Air Conditioning System

Research on the Heating Effect of a Convection Radiator Based on a Human Thermophysiological Model

Forced convection is the most effective way to improve the thermal efficiency of a radiator under low-temperature conditions. This technical method differs significantly from the heating effects of general radiation and natural convection. Few studies have applied the objective evaluation method based on quantitative calculation to evaluate the effectiveness of indoor heating or optimize the technical parameters (air flow rate, air supply method, etc.) of heating systems. This article couples human metabolic factors with heating environmental factors and uses a 57-node human thermal physiological model to evaluate the effectiveness of forced convection radiator heating from the perspective of the local thermal comfort of the human body and demonstrates the feasibility of this scheme by comparing it with floor radiation heating. The research shows that the air supply speed of a radiator affects human thermal comfort. Continuing to increase the wind speed, at a speed of 3 m/s, the surface temperature of the human body reaches a high value and will then decrease, leading to a decrease in thermal comfort. Research on indoor air distribution shows that the use of bottom-side air supply provides better thermal comfort compared to top air supply. The local skin temperature distribution of the human body indicates that when the indoor average temperature is higher than 20 °C, the overall thermal comfort of convective radiator heating and floor radiant heating is comparable. The article provides a way of objectively calculating and directly quantifying the effect of heating equipment on human thermal physiological parameters.

Investigation of non-uniform temperature distribution in air-cooled proton exchange membrane fuel cells with multizone temperature measurement

ABSTRACT Open-cathode air-cooled proton exchange membrane fuel cell stack relies on air fans both for fuel supply and stack cooling. Inappropriate stack thermal management and non-uniform temperature distribution can lead to compromised stack performance, reduced lifespan, and even thermal runaway. Thus, temperature distribution measurement, investigation and analysis are essential for air-cooled PEMFC’s optimized operation and performance. This study uses a multi-zone temperature measurement approach to investigate the impact of air supply method, airflow, and output current on stack temperature distributions. The experimental results reveal that the highest stack temperature occurs at the cathode channel outlet, while the lowest temperature is near the hydrogen inlet. At a 75A load, the maximum temperature difference between the inlet and outlet is 17°C. Increasing fan speed from 4500 to 8800 r/min reduces temperature non-uniformity in cell 10, the most uneven among the 19 cells, by 11.2%. Comparing blowing and suction air supply modes, blowing enhances stack output performance by 2.1%, with smaller temperature differences. Specifically, cell 10 experiences a 7.5°C lower difference at 4500 r/min and a 3.6°C lower difference at 8800 r/min airflow. Under blowing air supply, temperature non-uniformity decreases by 36.95% at 4500 r/min and 29.2% at 8800 r/min.

Numerical investigation of multi-physical field dehumidification control technology for prefabricated chambers

High-temperature and high-humidity environments reduce the insulation characteristics of electrical equipment and seriously threaten the safe and stable operation of power equipment in prefabricated chamber substations. This paper adopts a numerical simulation method to analyze the influence of the thermal dissipation power of equipment and air supply conditions of air conditioners on condensation in the prefabricated chambers and optimize the air supply method. The results show that the increase of load power can effectively inhibit the condensation phenomenon in the chambers; when the relative humidity is constant, lowering the air conditioner outlet temperature and increasing the air velocity is conducive to reducing the amount of condensation, but the air velocity should not be lower than 1.5 m/s. Comparing the air supply modes of prefabricated chambers air conditioning, the dehumidification capacity and air supply uniformity using top air supply is better than lateral air supply, and the dehumidification capacity is significant when the air supply conditions are 20 °C, 70%, and 1.5 m/s. Compared with the lateral air supply, the average relative humidity on the surface of the equipment is less than 80% when the top air supply is used, which improves the safety performance of the equipment in high temperature and high humidity environments. The findings of the article provide a reference for the safe operation of the equipment in a confined space environment and the design of moisture-proof and condensation-proof.

Performance of an innovative personalized ventilation mode based on air attachment under non-isothermal air supply conditions

In view of the shortcomings of traditional personalized ventilation method, an innovative mode of personalized ventilation was explored in this study. To investigate the performance of the personalized ventilation mode, velocity field measurements were performed to examine the impact of the supply air temperature on the airflow distributions, and a tracer gas system was used to test the fresh-air ratio in the breathing zone. The results show that the critical supply air velocity increases as a function of the supply air temperature and that the position height of the air attachment formation is a decreasing function of the supply air temperature. The fresh-air ratio in the breathing zone was significantly correlated with the formation and height of the attachment. Furthermore, the higher the position of the air attachment formation, the greater the breathable fresh-air ratio. The breathable fresh-air ratios were 83.3 %, 82.3 % and 84.1 % at supply air velocities of 0.3 m/s, 0.4 m/s and 0.5 m/s, respectively, and a supply air temperature of 17 °C. Compared with the traditional air supply method, the ventilation effectiveness of the the air dress personalized ventilation(ADPV) method in this study is highest. Irritation in the eyes was weaker than that in other areas. Irritation in the lips and nose was an increasing function of the supply air velocity, and no obvious connection with the supply air temperature. Furthermore, the supply air velocity and temperature significantly influenced the sensation in the upper body; however, no obvious influence was observed on the sensation in the lower body. It was verified that the ADPV method was able to satisfy the requirements of human comfort and the breathable air quality simultaneously.

The Influence of Supply Channel Design on the Gas-Dynamic Structure of Air Flow in a Vertical Conical Diffuser

Vertical conical diffusers are used in power engineering, chemical industry, technological processes, and other industries. The efficiency of many machines and pieces of equipment is determined by the gas-dynamic and heat-exchange perfection of processes in diffusers. This study assesses the influence of the air supply method on flow structure in a diffuser. The studies were carried out on a test bench with thermal imaging for air flow rates ranging from 0.018 to 0.057 m3/s (42,500 < Re < 150,000). Two designs were examined: (1) a conventional air supply through one channel from below and (2) a nozzle air supply through four tubes at an angle of 45° to the vertical axis. In addition, the influence of the cross-sectional shape of the supply channels of both designs was studied. It is established that the use of a conventional air supply through one channel leads to the generation of a pronounced central flow along the vertical axis (all configurations of the supply channel) and the creation of stagnant zones in the corners of the diffuser (round and triangular channels; the use of a square supply channel causes the most uniform air distribution throughout the entire volume of the diffuser (while maintaining the central flow). It is found that with nozzle air supply, there are no stagnant zones in the corners and intense air movement generation in the centre of the diffuser (round and triangular tubes) can be observed; the use of square nozzle tubes causes intense flow movement at the base of the diffuser, which quickly collapses upstream, uniformly filling the entire volume of the diffuser’s cylindrical part. The presented data can be useful for designing various machines and pieces of equipment with vertical conical diffusers.

Personalized kitchen air supply for reducing individual thermal discomfort and cooking pollution intake

High ambient temperature and cooking activities that produce pollutants and waste heat usually make the indoor air quality and thermal environment of residential kitchen unfavorable in summer. Personalized kitchen air supply (PKAS) could be applied to relieve the thermal discomfort and cooking pollution intake of cooking staff. This paper investigated a personalized air supply method of residential kitchen in summer. The residential kitchen was depicted in computational fluid dynamics simulation by realizable k-ε model and discrete ordinate radiation model to reflect the complex thermal characteristics of stove. Based on orthogonal analysis, exhaust rate, exhaust outlet baffle width, and supply air angle were significant factors affecting the concentration of pollutant in kitchen space, whereas exhaust rate and air supply rate were significant factors affecting the intake fraction. Single-factor analysis was further conducted to find better parameter configurations of PKAS for pollutant control. Then, thermal comfort experiments with and without air supply were carried out. When the air supply volume was 280 m³/h and the air supply temperature was 21 °C, the thermal discomfort of subjects can be effectively improved against an uncomfortable condition of 30 °C background temperature, 80 % relative humidity, and a localized heat source intensity of 4.5 kW. The result of this paper can provide valuable information to develop PKAS for better thermal discomfort improvement and cooking pollutants control.

A New Optimization Design Method of Multi-Objective Indoor Air Supply Using the Kriging Model and NSGA-II

When using meta-heuristic optimization approaches for optimization, a large number of samples are required. In particular, when generating a subgeneration, the utilization of existing samples is low and the number of individuals is high. Therefore, surrogate-based optimization has been developed, which greatly reduces the number of individuals in the subgeneration and the cost of optimization. In complex air supply scenarios, single-objective optimization results may not be comprehensive; therefore, this paper developed a double-objective air supply optimization method based on the Kriging surrogate model and Non-dominated Sorting Genetic Algorithms-II. And it proposed the infill criteria based on clustering to advance the Pareto Frontier. The method was validated with an inverse prediction case, and in particular, the problems when based on 3D steady-state simulations were analyzed. The results showed that the method can quickly achieve an approximate prediction of the boundary conditions (when predictions were made based on experimental data, the number of simulations was 82 and the average error was 6.8%). Finally, the method was used to optimize the air supply parameters of a dual-aisle, single-row cabin, with only 118 samples used in the optimization process. The Pareto set suggested that an airflow organization with dual circulation may be optimal.

Experimental Study on Denitration Transformation of CFB Boiler Burning Fujian Anthracite

Two 75 t/h medium-temperature separated circulating fluidized bed boilers burning Fujian anthracite were upgraded with low NOx combustion (LNC). By reducing the effective cross-sectional area of the air distributor (from 13.43 m2 to 11.38 m2), improving the secondary air rate (from 40% to 45%), adjusting the secondary air supply method (adding a layer of upper secondary air, raising the height of the lower secondary air nozzle (0.4 m), and increasing the secondary air speed (from 48 m/s to 54 m/s), the reform of low nitrogen combustion was carried out. The transformation achieved remarkable results, i.e., the original NOx emission concentration can be controlled between 140–160 mg/m3 after the transformation, and the lowest value is below 120 mg/m3.

Impact of Primary Air Separation in a Grate Furnace on the Resulting Combustion Products

When burning fuel in grate furnaces, supplying the right amount of air to them is as important as the method of air supply. In a furnace with a fixed grate, the supply method of primary air is determined by the distribution of the supplied air stream over time, and in a furnace with a movable grate, the said method involves the distribution of the stream along the active length of the grate. The need to account for air distribution is attributable to complex processes that occur during the combustion process. The paper describes experimental studies aimed at determining the influence of the distribution of the supplied primary air on the emission of CO2, CO, SO2, NOx, and on the content of combustible parts in the slag. In all cases, the total amount of primary air supplied to the process as well as other process control parameters was identical, and only the distribution of primary air was different. The paper proposes the use of a generalized function to describe the distribution of air, defined by its total demand and the relative time R that fuel remains on the grate until the maximum air stream is obtained. The quantity R was accepted at the value ranging from 1/6 to 2/3. With the rise of R, the emissions of CO2, CO, and SO2 increased by 53%, 125%, and 27%, respectively, and the emissions of NOx and the share of combustibles in the slag decreased by 12% and 79%, respectively.

A dynamic pressure regain method for uniform air supply design

The Dynamic Pressure Regain Method, a new design method for uniform air supply, was proposed in this paper, based on the principle of total pressure balance. It can achieve uniform air supply by keeping equal dynamic pressure in adjacent sections of the main duct that opens up a new field for the design of uniform air supply duct system. Research was carried out through numerical simulation and full-scale experiment. First, the design steps of this method were proposed according to the flow characteristics in the duct. Then the recommended range of air velocity ratio was determined by numerical simulation calculation, and the resistance calculation formulas of the duct under this method were fitted. Finally, the full-scale experiment was carried out for the working conditions of inlet air velocity of 4 m/s and 5 m/s to verify the results of numerical simulation, including the total pressure balance, the uniformity of air supply system, the resistance calculation formulas of duct and the verticality of outlet airflow. The results showed that with a constant air velocity of the main duct sections, the variation of the total pressure loss was within 5 %, thus satisfying the total pressure balance; With a 0.6–1.0 air velocity ratio of the branch to main duct, the air volume imbalance rate of the branch duct was lower than 10 %; The error of local resistance calculation formulas of the duct system was no more than 3 %. The airflow deflection angle travelling out along the branch duct walls was within 20°. This complete design method of uniform air supply satisfies the total pressure balance and features simplicity, which decreases the air volume imbalance rate by 84 % compared with the static pressure regain method. Besides, when the size of the inlet duct remains constant, that of the design model will not change with the inlet air velocity. In addition, this study proposed the resistance calculation formulas that conform to the characteristics of its design model.

Design and operation of a fixed-bed pyrolysis-gasification-combustion pilot plant for rural solid waste disposal

This paper is to explore the use of rural solid waste (RSW) for pyrolysis-gasification-combustion in pilot plant scale aiming at sustainable management of rural waste in remote areas. Based on the experimental data obtained during pilot scale operation, the temperature in the furnace needs to be kept at least at 600 °C through analyzing the pyrolysis weight loss of the main combustibles in the RSW. Besides, the effects of the air supply method and ventilation rate on the pilot plant performance were explored. Results indicate that the active air supply method positively contributes to the performance of the pilot plant. The plant processed 10 t RSW/d, producing 12.82 g/Nm3 of tar with 1.75 % of ash. This study confirms the feasibility of the pilot plant for RSW disposal and provides theoretical support for the optimization of pilot plant operation.

Optimization of Cockpit Ventilation for Polar Cruise Ships in Combination with Windscreen Defogging and Cabin Comfort Considerations.

Polar cruise ships are exposed to extreme external conditions during voyages, resulting in cockpit windscreens that are prone to fogging and frosting, seriously affecting the driver’s vision and even threatening navigation safety. However, the current research mainly focuses on cabin comfort, ignoring the coupling of defogging and comfort. Accordingly, this paper combines cockpit-windshield-defogging design and cockpit comfort considerations, and proposes 108 orthogonal-ventilation design parameters based on the four basic ventilation methods. The effects of different air supply parameters on comfort and anti-fog characteristics are investigated by using fluid dynamics simulation methods. The entropy weight–TOPSIS algorithm is employed to find the optimal ventilation parameters. The results show that the “Down-supply up-return type vertical jet” air supply method corresponding to an air supply velocity of 1 m/s, an air supply temperature of 297 K, and an air supply relative humidity of 30% has the smallest Euclidean distance from the positive ideal solution, and the largest Euclidean distance from the negative ideal solution; thus, it obtains a higher and the highest priority. This air supply method provides the best thermal comfort for the drivers, as well as the best anti-fogging and defogging effect. The results can be useful to provide suggestions for the future design of the air-conditioning systems in polar cruise ships.

Research on a new optimization method for airflow organization in breeding air conditioning with perforated ceiling ventilation

Modern agricultural production puts forward higher requirement for environmental control. Uniform air distribution can form the stable temperature, humidity and velocity of indoor air, which is particularly important for agricultural production. In this paper, theoretical research is conducted on a nursery piggery and the velocity uniformity is defined to evaluate the performance of perforated ceiling ventilation. A new optimization method for airflow organization is developed, which improves the airflow organization based on the suitable air supply angle. It shows that the velocity uniformity is increased and then decreased with the increase of air supply angle, and the best air supply angle is around 35°. The optimal air supply angle changes with the plenum height, and there is a threshold for the plenum height. The best velocity uniformity can be achieved when the height of plenum is 0.5 m. Besides, the air supply velocity has almost no effect on the velocity uniformity. The optimization model for airflow organization based on the air supply angle is established and its accuracy is verified. Finally, a specific case is selected to compare and analyze the air distribution under different air supply methods, which verifies the feasibility of the optimization method proposed in this paper.

Research on the temperature field of grain piles in underground grain silos lined with plastic

AbstractTo investigate the temperature change in grain piles during underground grain storage, this study considers high‐moisture grain, and uses a combination of experiments and numerical simulation to study the change in the temperature field in the underground bin during the static storage and mechanical ventilation phases. The results show that during the static storage stage, grain respiration is strong. The grain pile first begins to heat up at the bottom and gradually forms a high‐temperature heat core; in the mechanical ventilation stage, the grain pile first cools down from the air outlet, and then gradually spreads to the entire silo. Inside, the study found that the diffusion path is related to the air duct setting. After being ventilated for 10 hr, the grain pile temperature in the test silo fell below 10°C from the middle to the bottom of the silo, and only reached 15°C above the return air outlet near the grain‐loading line. An increase in air supply accelerates the temperature decrease in the grain pile; the difference in the initial state of the grain pile has little effect on the cooling effect of mechanical ventilation. In the experiment and simulation, the mechanical ventilation adopts a uniform air supply method, which has a significant effect on reducing the grain pile temperature in the silo.Practical ApplicationsIn this study, a test platform is established for an underground silo lined with plastic. By monitoring the temperature in the test silo, the dynamic temperature changes in the grain pile can be analyzed, and the results are compared with the numerical simulation results to verify the model reliability. The temperature field simulation of grain piles under different conditions lays the foundation, and at the same time provides a basis for formulating relevant measures to achieve safe grain storage.