Stable Airflow Research Articles

Effect of airflow velocity in vessel-pipelines on dust explosion during pneumatic conveying

In order to investigate the flame propagation and pressure characteristics of dust particles during airflow transportation, a dust explosion experimental apparatus simulating dust handling processes was designed. The system is supplied with a stable airflow by a high-pressure fan, capable of continuously transferring dust from the vessel to the pipeline at a controllable speed. Dust explosion experiments were meticulously executed by applying 1 kJ of ignition energy to the transported dust particles at airflow velocities of 5, 10, and 15 m/s. This study examines the effects of airflow velocity, pipe diameter, and ignition position on explosion characteristics and delves into the mechanisms of these effects through a detailed analysis of experimental results. For the maximum explosion pressure, an increase in airflow velocity causes the maximum explosion pressure to rise. As the pipe diameter increases, the maximum explosion pressure first rises and then falls. The maximum explosion pressure occurs in the case of bottom ignition. The range of maximum explosion pressure values is expected to provide a reference for explosion detection and explosion venting. For flame propagation, the flame undergoes five processes within the vessel, including ignition of dust particles, spherical flame development, flame stretching towards the mouth of the pipe, complete combustion of particles, and near exhaustion of particle combustion. The higher the airflow velocity and the larger the pipe diameter, the more pronounced the flame stretching and development towards the pipe opening become. Within the pipe, two distinct flame propagation behaviors were observed under conditions of high and low airflow velocities. Compared with the experimental results of high-pressure pneumatic powder spraying forming a dust cloud within a vessel-pipeline, this study measures the maximum explosion pressure at specific turbulence levels and establishes a quantitative relationship between airflow velocity and explosion characteristics. Utilizing this correlation can provide a reference for predicting industrial-grade dust explosion characteristics at different airflow velocity levels, thereby offering a more optimized design basis for the design and safety protection of industrial equipment.

Integrated CFD and MBD methods for dynamic performance analysis of a high-speed train transitioning through varied windbreak corridor designs

With increasing train speeds, the wind environment along routes has become complex, variable, and extreme. Constructing windbreak facilities is an effective strategy to enhance train operational safety in windy zones. Various windbreak designs exhibit notable differences in improving train dynamic performance, and economic considerations are also crucial. Utilizing the non-constant compressible Reynolds time-averaged equation URANS (Unsteady Reynold-averaged Navier–Stokes) alongside the shear-stress transport (SST) k-ω turbulence model, this study simulates the non-constant aerodynamic characteristics of a 350 km/h high-speed train traversing through different forms of windbreak corridors in a 30 m/s wind zone. The train's dynamic response was captured using a combined CFD–MBD (Computational Fluid Dynamics and Multi-Body Dynamics) offline time-domain simulation, the accuracy of which was verified experimentally. Results indicate that vortices of various positions and shapes form in the flow field along the windbreak corridor depending on the size of the openings. Using the no-windbreak corridor (Case 1) and the fully enclosed corridor (Case 4) as control groups, it was observed that smaller openings lead to more stable airflow, enhancing peak damping and fluctuation effects, albeit with varying stages of aerodynamic load fluctuation. The 1/3-opening windbreak corridor (Case 3) effectively mitigated the sudden aerodynamic load changes at the wind zone transition of the 2/3-opening windbreak corridor (Case 2), with the primary fluctuation area in Case 3 being the wind section. Dynamic analyses revealed that Case 2 exhibited insufficient lateral aerodynamic performance, raising derailment concerns. In contrast, Case 3 ensured travel safety and comfort effectively, while Case 4 offered excessive protective capacity. This study's findings serve as a valuable reference for designing windbreak corridors and ensuring the safe operation of trains in windy regions.

Enhancing pressure control of low-friction pneumatic actuator with eddy current damper via valve dead-zone compensation

This article addresses the high-performance pressure control of a pneumatic actuator that incorporates an air-bearing piston and an eddy current damper (ECD). After optimizing the pneumatic actuator, achieving precise pressure control relies on maintaining an accurate and stable airflow through the control valve. A terminal sliding mode adaptive control method (TSMAC) is proposed, proficiently integrating considerations for dead zone nonlinearities in the proportional valve and the effects of unmodeled disturbances in the pneumatic actuator. Using the opening area of the proportional valve as the input to the pneumatic system greatly simplifies the control process and reduces the workload required for valve parameter calibration. The Lyapunov-based stability analysis demonstrates that excellent asymptotic output tracking can be achieved with low steady-state error simply by knowing the boundaries of the valve opening area. The control effect of the proposed control strategy is compared with an adaptive backstepping sliding mode control method based on a linearly fitted proportional valve model on an established constant pressure control test bench. Experimental results under various loads and operating conditions illustrate the effectiveness of the proposed approach.

Sustainable Development Optimization of a Plant Factory for Reducing Tip Burn Disease

It is generally believed that stable airflow can effectively reduce tip burn, a common lettuce plant disease in closed plant factories that severely restricts the sustainable development of these factories. This study aims to achieve stable airflow in the cultivator by zoning the seedling and growth stage crops and installing differential fans, while ensuring comprehensive quality. In this study, a three-dimensional simulation plant factory model was created to simulate the airflow inside the cultivator, taking crop shading and heat dissipation from LED light sources into account. Experiments on photosynthetic physiology and airflow were used to determine environmental thresholds for crop growth, which were then used as CFD boundary conditions. After adopting the optimized cultivation model, the comprehensive quality of lettuce increased by 22.28% during the seedling stage, and the tip burn rate decreased to 26.9%; during the growth stage, the comprehensive quality increased by 25.72%, and the tip burn rate decreased to 23.2%. The zoning optimization cultivation method and differential fan arrangement used in this study to improve the airflow field of plant factories provide new ideas and reliable theoretical support for plant factories to combat lettuce tip burn disease.

High‐Resolution Aircraft Observations of Turbulence and Waves in the Free Atmosphere and Comparison With Global Model Predictions

AbstractHigh‐resolution flight data obtained from in situ measurements in the free atmosphere aboard the High Altitude and Long Range Research Aircraft (HALO) are used to determine eddy dissipation rates along extended flights during the recent Southern Hemisphere Transport, Dynamics, and Chemistry aircraft campaign (SOUTHTRAC) in the 2019 austral winter. These data are analyzed and correlated with quantities characterizing the ambient airflow and the magnitudes of vertical energy propagation through internal gravity waves. The observed turbulence events are strongly correlated with elevated shear values, and overturning gravity waves do not appear to play a role. A highlight of the analysis is the validation of a recently implemented Clear Air Turbulence (CAT) forecast index in the European Centre for Medium‐Range Weather Forecast integrated forecast system. Here we find a slightly better correlation of the CAT prediction with the HALO research aircraft observations compared to those of commercial aircraft. The observed turbulence during SOUTHTRAC was never stronger than moderate, as EDR values remained below 0.3 m2/3 s−1. In general, light and light‐to‐moderate turbulence events were extremely rare, occurring in only about 5% of the flight time, and stronger events in less than 0.2%. These results are also reflected in the local atmospheric conditions, which were dominated by a thermally very stable airflow with low vertical shear and large Richardson numbers.

Lean blowout characteristics of spray flame in a multi-swirl staged combustor under different fuel decreasing rates

Lean Blow Out (LBO) poses a significant safety hazard when occurring in aero-engines. Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative for safe operation. The objective of this work is to evaluate the effects of fuel decreasing rates and pressure drops of the injector on LBO performances in a multi-swirl staged combustor equipped with an airblast injector. A set of hardware and control system was developed to realize a user-defined fuel supply law. High-speed imaging was applied to record complete LBO processes under the conditions of linear fuel reduction and stable airflow. Partical Image Velocimetry (PIV) and Planar Mie (PMie) scattering were used to acquire the flow fields and spray fields under non-reacting conditions. Experimental results have shown that LBO limits extend to leaner conditions as the pressure drop of the injector increases. With an increase of the fuel decreasing rate, the exhaust temperature before flame extinction increases, and the LBO Fuel-to-Air-Ratio (FAR) decreases. The time evolution of the integral CH* intensity conforms to a linear function during the LBO process. Proper Orthogonal Decomposition (POD) was used to analyze the dynamic characteristics of lean-burn flames. Under different fuel decreasing rates and pressure drops of the injector, flames close to LBO present similar modal spatial distributions, alternately appearing axial, radial, high-order axial, and high-order radial oscillations.

Optimization Design of a Pneumatic Wheat-Shooting Device Based on Numerical Simulation and Field Test in Rice–Wheat Rotation Areas

In rice–wheat rotation areas of China, traditional wheat seeders have severe blockage, low working efficiency and poor seeding quality. In this study, a pneumatic shooting technology was designed, consisting mainly of a nozzle, shell and acceleration tube. To improve the sowing depth of the pneumatic shooting device, the response-surface methodology of structure parameters and CFD simulation technology was adopted in this work. The effects of working pressure, acceleration-tube diameter and throat distance on the steady airflow length (SAL) and steady airflow velocity (SAV) were studied by airflow field analysis, and the response-surface method was introduced to obtain the optimal parameter combination of the pneumatic shooting device for wheat. The optimal parameter combination was working pressure 686 kPa, acceleration tube diameter 8 mm and throat distance 20 mm. The simulation result showed that the optimized device of pneumatic shooting performs faster and has more stable airflow field characteristics in comparison to the initial device. The field test demonstrated that the optimized device has about 68% higher seeding depth than the initial device. The average field-seeding depth of the optimized device was 19.95 mm, which is about 68% higher than the initial device. The emergence rate for the optimized device was about 88.7% without obvious reduction. CFD and response-surface methods positively affect the optimization of pneumatic wheat-shooting devices, and the significance was also confirmed.

Non-invasive arterial pressure monitoring by a new pneumatic sensor and on-line analysis of pulse waveforms for a modern medical home care systems.

The development of the third-generation devices for medical home care systems is in the center of discussion. The results of developing non-invasive arterial pressure monitoring channel on the basis of the unique pneumatic sensor are discussed in detail. In particular, the main principles of operation, design features and testing results of a pneumatic sensor are considered. Namely, the issues of the stable air flow regime in the sensor’s working chamber are discussed. It is shown that the miniature size of the sensor and the possibility of its precise positioning directly in the measurement zone on small (< 1 mm) areas of the skin elastic surfaces result in improved quality of pulse wave shape recovery, the parameters continuity measured and the disturbances reduction. Measurement examples for some human superficial arteries are given. The possibility of continuous measurement of the actual value of blood pressure for radial and temporal arteries is confirmed.

Investigating the In-Flow Characteristics of Multi-Operation Conditions of Cross-Flow Fan in Air Conditioning Systems

Cross-flow fans are widely used in numerous applications such as low-pressure ventilation, household appliances, laser instruments, and air-conditioning equipment. Cross-flow fans have superior characteristics, including simple structure, small size, stable airflow, high dynamic pressure coefficient, and low noise. In the present study, numerical simulation and experimental research were carried out to study the unique secondary flow and eccentric vortex flow characteristics of the internal flow field in multi-operating conditions. To this end the vorticity and the circumferential pressure distribution in the air duct are obtained based on the performed experiments and the correlation between spectral characteristics of multiple operating conditions and the inflow state is established. The obtained results show that when the area of the airflow passage decreases while the area of the eccentric vortex area gradually increases, then the airflow of the cross-flow fan decreases, the outlet expands, and the flow pattern uniformity reduces. It was found that wakes form in the vicinity of the blade and the tail of the volute tongue, which generate pressure pulsation, and aerodynamic noise. The pressure distribution along the inner circumference shows that the total minimum pressure appears in the eccentric vortex near the volute tongue and the volute returns near the zone. Moreover, it was found that the total pressure near the eccentric vortex is significantly smaller than that of the main flow zone. As the flow rate decreases, the pressure pulsation amplitude of the eccentric vortex region significantly increases, while the static and total pressure pulsation amplitudes are gradually increased. Close to the eccentric vortex on the inner side of the blade in the volute tongue area, total pressure is low, total pressure on the outside of the blade is not affected, and pressure difference between the inner and outer sides is large. When the flow rate of the cross-flow fan is 0.4 Qd, there is no obvious peak at the harmonic frequency of the blade passage frequency. This shows that the aerodynamic noise is caused by the main unstable flow.

Effects of ridge height and spacing on the near-surface airflow field and on wind erosion of a sandy soil: Results of a wind tunnel study

In wind tunnel experiments, we measured the airflow field near the ground surface and the resulting sand transport rate over a sand bed that contained widely but uniformly spaced non-erodible ridges. We found that when airflow passed over the bed, the wind velocity changed drastically around the first ridge, but the magnitude of the change decreased gradually moving downwind until a relatively stable airflow developed, characterized by regular fluctuation over the uniformly spaced ridges. The distance from the first ridge to the zone of stable airflow increased with increasing ridge height or spacing between ridges. This airflow field led to a non-uniform distribution of wind erosion that affected total sediment transport from the sand bed. Using our wind tunnel simulation results as inputs for existing sediment transport equations, we developed a model to predict sediment transport (q) over a sand bed that contained widely spaced ridges: q=C'dDρgu*2u*-u*texp⁡(-aHu*3n). The model accounts for the ridge height (H), number of ridges per unit length (n), and the wind’s free-stream friction velocity (u*) and threshold friction velocity (u*t). We discussed the different mechanisms by which ridges influence the near-surface airflow at large spacing (> 5H) and small spacing (≤ 5H). The ridges appear to affect the airflow as roughness elements when the spacing is small, but act as barriers to the wind when the spacing is large.

Theoretical Study of the Effect of Instrument Parameters on the Flow Field of Air-Flow Impacting Based Mechanochemical Synthesis

The air-flow impacting based mechanochemical synthesis is an alternative strategy to traditional mechanochemical preparations, which has many advantages in terms of reaction temperature, preparation speed, and cleanness. Herein, we theoretically study the effect of instrument parameters, including the axial position of physical target, the diameter difference between nozzle throat and suction pipe, and divergence angles of uniform speed region, on the flow field of the air-flow impacting based mechanochemical synthesis. The optimized parameters have been obtained. Under the optimal conditions, a stable and high-speed air flow is obtained, in which the speed can achieve a Mach number of approximately 2.6. The high-speed air flow is able to easily carry the reacting substances to arrive at the physical target, triggering a chemical reaction. These findings undoubtedly provide a key guideline for further development and application of the air-flow impacting based mechanochemical synthesis.

The atmosphere under the waves: forgotten meteorology from Nazi Germany

Mountain waves are oscillations of stable airflow over mountains which remain roughly fixed relative to the ground as the airflows through them. They are significant to numerical weather models, ozone depletion, and aviation safety. Textbook descriptions of mountain waves assume laminar flow down to the mountain surface, following the classic theory of Scorer. However, there can be a region of non‐wavelike atmosphere under the mountain waves, such as convection, turbulent eddies and rotors in the boundary layer, implying a different paradigm to explain wave launching. This paper reviews how the existence of the atmosphere under the mountain waves was realised in Nazi Germany, where mountain waves were discovered using gliders in 1933 and studied in the run‐up to World War 2.1

Stability of large room airflow structures in a ventilated room

ABSTRACTThis paper presents a new set of experimental data for different kinds of room airflows in a ventilated room. The data are used to examine Archimedes number effects on the behaviour of large-scale flow structures and their stability versus time. All experiments are performed in a simplified room geometry, representing a small meeting room, a train or an airplane cabin. The supply air is introduced at the ceiling and the exhaust air leaves the room at the bottom zone. The heating power is realised by four controllable heat sources in the lower part of the model room. The experimental investigations apply different supply air set-ups as well as changing supply air velocities and a variation of the heating power. The data of the experiments indicate that the room geometry-based Ar number can be used to distinguish between unstable to stable room airflow structures. Low velocities and high thermal loads cause time depended, unstable room airflows. Neither the forced nor the free convection dominates the flow structure. By increasing the inlet velocity, the airflow structure gets more stable. Large eddies occur between the heat sources and the ceiling of the model room. This experimental investigation showed that it is possible to determine an Ar number for the room geometry under investigation, in the region where a transition takes place from instable to stable airflow. The value of this critical Ar number has been extracted from a qualitative velocity profile analysis.

Experimental study of high concentrations of coal mine methane behavior in downward ventilated tilted roadways

The movement and distribution of methane in coalmine roadways are major issues relating to coalmine safety. Once high concentrations of methane accumulate in downward ventilated tilted roadways, the movement of methane can be very special. A 1/50 experimental model was constructed for the study on high concentrations of methane behavior in downward ventilated parallel roadways. This experiment measured gas concentrations in the upper and lower parts of the methane accumulating roadway and the wind speeds both in the methane accumulating roadway and in its parallel roadway The experimental results indicate that the methane draft pressure (the additional natural draft pressure due to the density difference of methane and air when high concentrations of methane accumulate in tilted roadways) could lead to airflow reversion in a downward ventilated roadway; methane may flow with the reversed airflow into the parallel roadway. The reversed methane that flows into the parallel roadway could generate a new methane draft pressure, which would oscillate airflow under certain conditions. According to the experimental results with parallel roadways of different windage, a larger windage of the parallel branch could ensure a relatively stable airflow, and a smooth methane discharge process. Through analysis by oscillation theory and the Archimedes number, it is concluded that the parallel roadway windage affects the methane draft pressure-caused airflow disorder by two aspects: (1) a larger windage deceases the amplitude of airflow oscillation and (2) a larger windage decreases the methane flown into the parallel branch, which, in turn, decreases the critical wind velocity for airflow reversion in the parallel roadway. The effect of windage is proved by a numerical simulation of Jiulishan Mine at the end of this paper.

Active Airflow Generation to Assist Robotic Gas Source Localization: Initial Experiments in Outdoor Environment

Mobile robots that can search for gas sources are being developed to accomplish various tasks for protecting people’s safety, e.g., detecting gas leaks in industrial plants. If highly sensitive gas sensors are provided, robots will even be able to search for explosives set by terrorists in airports and find missing persons in disaster sites, just as trained dogs do. The use of these robots for monitoring gas emissions in landfill sites is also receiving a growing interest. In landfill sites, methane is produced by bacterial decomposition of organic waste. Since methane is flammable and has a strong greenhouse effect, methane emission monitoring is important not only for fire prevention but also for prevention of global warming. Gas molecules released in the air from their source are mainly carried by airflow, and form a plume in the downwind direction. Most gas source localization robots search for the location of a gas source by tracking a gas plume in the upwind direction. They succeeded in localizing a gas source in simplified environments, e.g., in a unidirectional airflow field in a wind tunnel. However, the direction of the airflow in the actual environments often fluctuates. Especially, the airflow direction in an open outdoor environment like a landfill site shows large fluctuations. It is difficult for the robot to track a gas plume in such an environment because the plume comes to have a complicated structure. In order to adapt to the complexity of the real environment, some robots use stochastic methods to estimate the location of a gas source. However, inaccurate modeling of the gas dispersal and/or the target environment may cause a significant drop in the performance of these robots. Instead, we propose a new robotic gas source localization method that uses actively generated airflow to regulate the airflow field. A swarm of mobile robots equipped with fans are deployed in the environment to generate a stable airflow field. A gas plume is stably formed in this modified airflow field, and therefore, a gas source localization robot can easily track the plume. In order to demonstrate the effectiveness of the proposed method, experiments were conducted in an outdoor courtyard on a moderate day. In the experiments, a robot explored on an open flat ground for a leak of flammable gas and tried to determine the direction of the leak location. The airflow velocity in this environment was 0.6 m/s on average during the experiments, and was 1.8 m/s at maximum. Four 40.8-W centrifugal fans (9BMB12PK01, SANYO DENKI) were used for active airflow generation, and were aligned on one side of a 2.8-m square experimental area. Each fan can make an airflow of 1 m/s at a point 2.5 m away from the fan. Saturated ethanol vapor was used as the detection target, and was released at a constant flow rate of 500 mL/min. The robot used in the experiments is equipped with an ultrasonic anemometer (WindSonic, Gill), and has four metal oxide gas sensors (TGS2620, Figaro) around the anemometer. Since the gas released from its source in the air is carried by the airflow, the robot can approach the gas source by moving against the wind and at the same time climbing up the gas concentration gradient. Therefore, the robot measures the airflow velocity and the gas sensor responses, and calculates the gas source direction vector by summing up the upwind vector and the gas concentration gradient vector. In the experiments, fifteen measurement points were set along two sides of the experimental area. The airflow velocity and the gas sensor responses were measured for three minutes at each measurement point. The angular difference between the actual direction of the gas source and the estimated gas source direction vector was calculated to examine the accuracy of the estimated direction. When the fans were deactivated, the estimated gas source direction vector was highly variable, although it roughly pointed to the actual location of the gas source from time to time. On the other hand, when the fans were activated, the estimated gas source direction vector pointed to the actual direction of the gas source most of the time. The results indicate that the variations of the airflow field in the outdoor environment was regulated by the airflow actively generated by the fans and that the direction of the gas source was successfully estimated in the regulated flow field. Figure 1

Active Airflow Generation to Assist Robotic Gas Source Localization: Initial Experiments in Outdoor Environment

A new gas source localization method that uses actively generated airflow is proposed. A gas source localization robot searches for the location of a gas source by tracking a gas plume in the upwind direction. However, the robot often fails in tracking the plume in an actual environment owing to the large fluctuations of the airflow field and the plume structure. To overcome this problem, we propose to deploy in the environment a swarm of mobile robots equipped with fans to generate a stable airflow field so that a stable gas plume will be formed and the robot can easily track it. Experimental results are presented to show that the variations of the airflow field can be suppressed by the actively generated airflow even in an outdoor environment. It is also shown that errors in the gas source direction estimated by the robot can be reduced by the proposed method.

Design and Implementation of Automatic Air Flow Rate Control System

Venturimeter is an apparatus that can be used to measure the air flow rate. In this experiment we designed a venturimeter which equipped with a valve that is used to control the air flow rate. The difference of pressure between the cross sections was measured with the differential pressure sensor GA 100-015WD which can calculate the difference of pressures from 0 to 3737.33 Pa. A 42M048C Z36 stepper motor was used to control the valve. The precision of this motor rotation is about 0.15 °. A Graphical User Interface (GUI) was developed to monitor and set the value of flow rate then an 8-bit microcontroller was used to process the control system In this experiment- the venturimeter has been examined to get the optimal parameter of controller. The results show that the controller can set the stable output air flow rate.

수치해석을 이용한 임시대피소 내 공기감염확산 저감장치의 성능 분석

Purpose : When natural disaster occurs, the victims are evacuated to temporary shelters such as indoor gymnasiums or large space buildings until their homes are recovered. If someone in this temporary shelter is infected with an airborne infectious disease, it becomes easier for the disease to spread to the other people in the shelter than it would be under normal conditions. Therefore, temporary shelters need to provide not only water and food but also hygienic indoor conditions. Methods : In this study, the use of mechanical systems such as ultraviolet germicidal irradiation (UVGI) systems and air cleaners were simulated using numerical analysis to find out how these systems can control airborne infection in temporary shelters. An indoor gymnasium was selected as a temporary shelter for the numerical simulation model considering Korea's post-disaster response system. Influenza A virus was assumed as an airborne infectious disease and the diffusion of the virus was made by one person in the shelter. Results : The result of this study showed that the UVGI systems disinfected the virus more effectively than the air cleaners by creating a more stable airflow after the disinfection process. The air cleaners could remove the virus but since it created an unstable airflow in the temporary shelter, the virus was condensed to a certain area to show a higher virus concentration level than the source location. Implications : In the temporary shelter, it is necessary to use UVGI systems or air cleaners for hygienic indoor conditions.

Improvement of thermal performance of a solar chimney based on a passive solar heating system with phase-change materials

Passive solar systems such as solar chimneys need solar radiation in order to work. Therefore, they cannot present stable natural ventilation when solar energy vanishes: to have a more robust and stable condition, solar energy should be stored during the day and released back during the night. Phase change materials can save additional thermal energy during the day and release it during the night in order to facilitate stable ventilation. In this study, a CFD simulation has been performed to investigate the effect of phase-change materials (PCM) utilization in the solar chimney to provide a stable temperature and air flow rate for a guardroom. The simulation was carried out for a whole day in winter in two cases: with and without PCM usage. The results show that use of PCM as an energy storage device significantly enhances the temperature stability of the guardroom.

Effects of air temperature and air flow rate control on the tipburn occurrence of leaf lettuce in a closed-type plant factory system

This study aimed to establish a practical method to reduce tipburn symptoms on leaf lettuce cultivars in a closed plant factory system, focusing on air temperature conversion at specific plant growth stages and artificial air flow application strategies using pre-screened tipburn-sensitive cultivars. Inter-conversion effect of day temperature among 18, 22, and 25°C, 12 days after transplanting on tipburn occurrences, were compared with stable day temperature condition. Horizontal air flow rates were controlled at 0.28 (Low), 0.55 (Medium), and 1.04 m·s−1 (High). Tipburn occurrences were highly variable depending on the lettuce cultivars tested. Following the initial screening of 28 leaf lettuce cultivars under 3 different light intensity conditions (ranging from 150 to 250 mol·m−2·s−1), two cultivars exhibiting relatively higher percentages of tipburn were selected for the following air temperature and air flow treatments. None of the temperature treatments effectively reduced tipburn symptom, while adjusting the temperature to a lower day temperatures at 12 days after transplanting only had a minor effect on lettuce growth and tipburn occurrence. In contrast, stable horizontal 24-hour air flow rates above 0.28 m·s−1 effectively reduced tipburn symptom, with no significant differences being found among the tested air flow rates, while above 65% of tipburned plants were found in the control plot of 0.08 m·s−1 flow rate. When stable air flow was applied, compared to the control, there was an increase in the absolute calcium content and a decrease in the calcium content difference between the inner and outer lettuce leaves. This calcium balance change may have occurred due to the enhanced transpiration in the inner parts of plants. This study showed that stable horizontal air flow application along cultivation beds is more effective than air temperature control in decreasing tipburn symptoms in a closed plant factory system.