Air Cushion Pressure Research Articles

Modeling and experimental study of the cushion lift dynamics system of a polar hovercraft

This paper investigates the cushion lift dynamics of a polar hovercraft. The motion of the flexible skirt on the ice surface is simplified and a mathematical model is established to study the dynamic response characteristics of the hovercraft in the process of lifting and moving over ice. This model considers the pressure/flow characteristics, skirt pressure, air cushion pressure, and flow rate of the fan of the hovercraft, and establishes a simulation using a C++program. When the hovercraft is pushed by the propeller, a thrust of 10 kN will cause a pressure difference of about 450 Pa between the front and rear chambers, 0.06 m in the height of the upstream and downstream discharge flows, and a decrease of about 0.4° in the longitudinal inclination angle. Changing the pitch angle to 0.5° creates a pressure difference of about 500 Pa between the chambers and a height difference of 0.07 m between the discharge. When the hovercraft speed is low, the wind speed has a small impact on the air cushion pressure of the lift system. The results of this research provide important technical and experimental foundations for further studies on the ice surface kinematics and safety control strategy of polar hovercraft.

Experimental study on wave motion of partial air cushion supported catamaran

To study the performance of partial air cushion-supported catamaran (PACSCAT), which is sailing with a flexible air seal in waves, this paper uses the model tests, and research the motion characteristics of PACSCAT at different wavelengths, by monitoring the boundaries of heave, pitch, acceleration, air cushion pressure. Firstly this paper introduces the test situation of PACSCAT in the towing tank and introduces the test method, equipment, and test conditions. Second, this paper extracts the test data, analyzes the features of heave, pitch, acceleration, and air cushion pressure, and studies their linear and nonlinear changes in regular waves. Thirdly this paper analyzes the nonlinear air leakage flow of the bow of PACSCAT in detail under the test conditions and studies the internal and external free liquid surface under different conditions.

Nonlinear air dynamics of a surface effect ship in small-amplitude waves

In many existing works, the seakeeping motions and air dynamics of a surface effect ship (SES) were assumed to be linear under small-amplitude waves (wave amplitude to wave length ratio ≤ 5%) to enhance the computational efficiency. However, according to SES model test results, it was found that even in small-amplitude waves, the fluctuating air cushion pressure shows significantly nonlinear effects. To precisely reveal this distinctive feature, the origin of nonlinearity was carefully investigated and the air leakage was considered as the main source of nonlinearity based on mathematical analysis in this paper. The reason is that the variance of clearance height under seals is comparable to the clearance height at equilibrium state in small-amplitude waves, which makes the air leakage area intermittently equal to zero without any harmonic variance. Therefore, an efficient partial nonlinear numerical model for the SES dynamics was proposed by combining a linear frequency-domain hydrodynamic model based on the efficient 2.5D methods with a nonlinear time-domain air dynamic model. The nonlinear parts of numerical results from the partial nonlinear model, including the fluctuating air pressure and midship accelerations, agree well with experimental results. The results demonstrate the effectiveness of the partial nonlinear model on the SES seakeeping performance prediction, and confirm that its nonlinearity mainly originates from the air leakage.

Experimental investigations on the resistance performance of a high-speed partial air cushion supported catamaran

The partial air cushion supported catamaran (PACSCAT) is a novel Surface Effect Ship (SES) and possesses distinctive resistance performance due to the presence of planing bottom. In this paper, the design of PACSCAT and air cushion system are described in detail. Model tests were carried out for Froude numbers ranging from 0.1 to 1.11, the focus is on the influence of air cushion system on resistance characteristics. Drag-reducing effect of air cushion system was proved by means of contrast tests in cuhionborne and non-cushionborne mode. Wave-making characteristics reflect that the PACSCAT would eventually enter planing regime, in which the air could just escape under the seals and the hull body could operate in a steady state. To acquire different air cushion pressure, air flow rate and leakage height were adjusted during tests. Experimental results show that the resistance performance in planing regime would decrease evidently as the increased air flow rate, however, the scheme with medium leakage height presents the best resistance performance in the hump region.

A Study on the Motion of Partial Air Cushion Support Catamaran in Regular Head Waves

In this paper, the motion of partial air cushion support catamaran (PACSCAT) sailing in regular waves was firstly investigated by the experimental method. The monitored histories of heave, pitch, midship acceleration, and air cushion pressure in towing tests are performed to analyze the influence of air cushion on the periodicity feature of hull body motion. Subsequently, using the finite volume method (FVM)-based CFD software Star-ccm, numerical simulations are carried out for the PACSCAT model with a simplification of the air cushion system. The detailed flow information of wave evolution, pressure, and velocity distribution is investigated. The calculated oscillation characteristics of different motion parameters are compared with those from experiment and show good agreement. The numerical method also has good capacity in the prediction of amplitude response of heave and midship acceleration; however, large error is found when calculating resistance and amplitude response of pitch.

Water resistance forecasting of the icebreaking aircushion platform

The forecasting resistance method of the icebreaking platform, based on dummy tests in NSTU experimental model ice basin is proposed in the article. Experimental research data of ice breaking air cushion platforms resistance in calm water are presented. The dummy tests main results taking into account the key parameters influencing the platform resistance are given. The effect analysis of aircushion pressure, airflow, icebreaking platform velocity, aircushion size ratio in plan and the variable basin depth on wave resistance is made. The formula of water resistance calculation is proposed.

Discuss on the method of adjusting the inflatable pressure of pressure sore air cushion bed based on patients' BMI

Objective To verify the validity of standard air cushion inflation method, and to explore the relationship between patients' body mass index (BMI) and the optimal air cushion inflation pressure. Methods A total of 90 orthopedic patients who were treated in Liangxiang Hospital of Fangshan District in Beijing from June 2017 to March 2018 were randomly divided into experimental group and control group, with 45 cases in each group. The control group used air cushion bed routinely according to the experience of nurses, while the observation group used standard air cushion bed inflation method according to previous research. Comparing the skin pressure and the feeling of using the mattress softness and hardness between the two groups, and analyzing the relationship between the pressure value of the mattress and the BMI of the patients in the observation group, the regression equation was obtained. Results The local skin redness rate of the observation group was 4.4%, 2.2% and 4.4% after 2, 48 and 72 hours of using air cushion mattress, which was lower than that of the control group 22.2%, 31.1% and 33.3%. The result was statistically significant (P<0.01) . Within 72 hours, the satisfaction degree of the observation group was higher than that of the control group, and the difference was statistically significant (P < 0.05) . The BMI of the patients in the observation group was linearly correlated with the optimal air cushion pressure (R2=0.962) . The air cushion pressure (kpa) =3.835+BMI×0.379. Conclusions Reasonable adjustment of the pressure of the air cushion bed can improve the effect of using air cushion bed. The method of adjusting the pressure of the air cushion bed based on patient BMI is convenient for nurses to master and operate. Key words: Pressure injury; Pressure sore; Body mass index; Air cushion bed; Correlation analysis

The effect of air cushion bed manual alternating inflation in preventing pressure ulcers in patients receiving microneurosurgery

Objective To explore the effect of manual inflation for air cushion bed in preventing pressure ulcers in patients receiving miconeurosurgery. Methods Totally 86 patients who received microneurosurgery were selected by convenient sampling from January to June 2017 and randomized into a control group (n=43) and a treatment group (n=43) according to the random number table. Patients in both groups used inflatable air cushion for pressure ulcer prevention and routine nursing. Alternating inflation was shut down in the air cushion used in the control group, maintaining proper pressure in air cushion, while in the treatment group, in addition to routine nursing, the air cushion was manually and alternatingly inflated at the right time. After relevant training and learning, nurses collected data and made sure if the patients sustained pressure ulcers, and identified their location and stage. Results The incidence of pressure ulcers of the treatment group (11.6%) was lower than that of the control group (P<0.05) , which was 30.2%. Conclusions By manual alternating inflation, surgical patients can change their pressed parts regularly, thereby reducing the incidence of pressure ulcers significantly in the patients who received microneurosurgery. Key words: Pressure ulcer; Neurosurgery; Perioperative nursing

THE AIR-PADDED HEADBOX AS PLANT OF THE MASS HEAD CONTROL

For papermakers the headbox is plant of exceptional importance, because it forms a thin jet of mass, which then enters the paper machine mesh on which it turns into paper. In the past, this process was almost on the brink of craft and art, but contemporary engineers have made a significant contribution to the systematization of the means and methods on which the headboxes operate or are controlled. The task is not only to make the headboxes easier to operate, but also to increase productivity and accuracy with which they can work.To control the headbox, two input control actions are required (the position of control member for air supply and the position of control member for mass feed). Unfortunately, each of the output variables (mass level, air cushion pressure and mass head) is influenced by all two input actions. For instance, if the position of air supply control members is changed, they will cause a change not only in the air pressure, but also disrupt the mass level and the mass flow in a significant range. Therefore, such an automatic control system calculation and setting can be very tedious. Thus, it is very important to have dynamic characteristics for all control variables, depending on each input action.The description of some methods that are suitable for solving this problem is the main content of this article.Keywords: paper machine, air-padded headbox, control system.

THE AIR-PADDED HEADBOX AS PLANT OF THE MASS HEAD CONTROL

For papermakers the headbox is plant of exceptional importance, because it forms a thin jet of mass, which then enters the paper machine mesh on which it turns into paper. In the past, this process was almost on the brink of craft and art, but contemporary engineers have made a significant contribution to the systematization of the means and methods on which the headboxes operate or are controlled. The task is not only to make the headboxes easier to operate, but also to increase productivity and accuracy with which they can work.To control the headbox, two input control actions are required (the position of control member for air supply and the position of control member for mass feed). Unfortunately, each of the output variables (mass level, air cushion pressure and mass head) is influenced by all two input actions. For instance, if the position of air supply control members is changed, they will cause a change not only in the air pressure, but also disrupt the mass level and the mass flow in a significant range. Therefore, such an automatic control system calculation and setting can be very tedious. Thus, it is very important to have dynamic characteristics for all control variables, depending on each input action.The description of some methods that are suitable for solving this problem is the main content of this article.

A robust neuro-based adaptive control system design for a surface effect ship with uncertain dynamics and input saturation to cargo transfer at sea

This paper is concerned with the problem of safely cargo transfer over a ramp between a cargo vessel and a lighter surface effect ship (SES). For this purpose, an adaptive neural network (NN) controller is proposed to control of ramp motions in the presence of entirely unknown dynamics and disturbances wherein the controller is subject to input saturation constraint. In this regard, we develop a novel non-affine nonlinear SES model by considering the nonlinear relationship among the air cushion pressure, the air flow into and out of the air cushion and the air cushion volume. To deal with the saturation constraint, an auxiliary system is proposed. To ensure the system stability, Lyapunov’s direct method is employed to investigate the uniformly ultimately boundedness (UUB) of all closed-loop system states. The simulation results demonstrate the effectiveness of the proposed controller in critical sea conditions, including regular and irregular waves with high frequencies and large amplitudes. A comparative analysis with model-based approaches including Proportional Integral Derivative (PID) and Linear-Quadratic Regulator (LQR) control systems are given to highlight the performance of the controller.

Mathematical Model of Dynamics of Air Cushion Vehicle with Ballonet Type Skirt on Water

The mathematical model of the dynamics of an Air Cushion Vehicle with a ballonet type skirt is presented. This model incorporates a number of interrelated submodels representing different constituents of ship dynamics: rigid body, air cushion, propulsion system, ballonet, underlying surface, aerodynamics, yaw rudder. The proposed model is capable of predicting all major characteristics of the ship movement such as trajectory, forces, moments, air cushion pressure, subject to different operating conditions. Both controlled and uncontrolled movement may be simulated. The suggested approach is based on the numerical integration of the equations of motion as well as the equation describing the pressure evolution in the air cushion. The verification of the model was carried out and the results of model towing tests are presented.

Sequential Injection Chromatography with post-column reaction/derivatization for the determination of transition metal cations in natural water samples

In this work, the applicability of Sequential Injection Chromatography for the determination of transition metals in water is evaluated for the separation of copper(II), zinc(II), and iron(II) cations.Separations were performed using a Dionex IonPACTM guard column (50mm×2mm i.d., 9 µm). Mobile phase composition and post-column reaction were optimized by modified SIMPLEX method with subsequent study of the concentration of each component. The mobile phase consisted of 2,6-pyridinedicarboxylic acid as analyte-selective compound, sodium sulfate, and formic acid/sodium formate buffer. Post-column addition of 4-(2-pyridylazo)resorcinol was carried out for spectrophotometric detection of the analytes׳ complexes at 530nm.Approaches to achieve higher robustness, baseline stability, and detection sensitivity by on-column stacking of the analytes and initial gradient implementation as well as air-cushion pressure damping for post-column reagent addition were studied.The method allowed the rapid separation of copper(II), zinc(II), and iron(II) within 6.5min including pump refilling and aspiration of sample and 1mmol HNO3 for analyte stacking on the separation column. High sensitivity was achieved applying an injection volume of up to 90µL. A signal repeatability of<2% RSD of peak height was found. Analyte recovery evaluated by spiking of different natural water samples was well suited for routine analysis with sub-micromolar limits of detection.

Motion Compensation System for a free floating Surface Effect Ship

This paper deals with vertical motion compensation, or motion damping, on a free-floating Surface Effect Ship (SES) at zero speed. The Motion Compensation System (MCS) works by varying the air cushion pressure of a Surface Effect Ship (SES) to minimize vertical motion due to sea waves. We present a control system which guarantees Global Exponential Stability for the closed-loop state space system and ultimately boundedness for the perturbed system. A study of the performance of the control system is demonstrated through model-test results of a 3 meter long SES.

Simulator and Control System Design for a Free Floating Surface Effect Ship at Zero Vessel Speed

This paper covers vertical motion damping of a free floating Surface Effect Ship (SES) at zero vessel speed. Vertical motion damping is requested at the bow deck of the SES during offshore wind turbine docking operation. Vertical motion damping provides a safer transfer of personnel and goods from vessel to the wind mill in moderate/rough sea states. This will provide an increased operational weather window access for maintenance and repair.The paper has two main contributions. 1) A simulator model for a SES. This is referred to as the cushion process plant model and provides a valid simulation tool for the control system. 2) A simple controller for actuating air cushion pressure. The presented controller actively controls the air flow actuators to the air cushion in order to minimize vertical motions at the vessel bow. A numerical stability investigation for the controller is included.

Experimental Research on Air Cushion Lamination Process

The application of air cushion in lamination process in the printing and packaging field is still a new attempt. In order to further understand the effect of air cushion lamination process in practical application, an experimental research is made on air cushion lamination. The air pressure distribution simulation results are verified using experimental device, and the pressure, thickness and lamination time of air cushion are varied. In addition, a process test is made over the adhesion of the corrugated core paper and surface paper using orthogonal experiment. The results show that the air cushion lamination process is feasible for lamination and the simulated air-cushion pressure distribution is consistent with the measured results. In this experiment 1000 pa air-cushion pressure, 2 mm air cushion thickness, 3 min lamination time, selected as the process parameters for the adhesion of corrugated paper, are appropriate.

Heave Motion Estimation on a Craft Using a Strapdown Inertial Measurement Unit

This paper deals with heave position and heave velocity estimation on a craft. The estimation is done without any knowledge of the specified craft. An accurate estimation of these signals is useful when one wants to control or monitor the heave motions on a platform or a ship such as in a active heave compensated systems. The necessary sensor input for the proposed guidance system is a strapdown inertial measurement unit (IMU) which consists of three gyroscopes and three accelerometers. In this case study, the heave motion estimation is required as input for a control system on a Surface Effect Ship (SES) where it is desired to control the air cushion pressure in order to damp vertical motions. The motions are induced by sea wave propagations. A SES will experience high frequency accelerations on the hull compared to other vessels. A lift fan sets up these accelerations or process disturbances and complicates the performance of the estimation. The estimation is performed using an observer. The observer model is based on a set of superimposed sinusoidals, each with a different excitation frequency. The sum of these denotes the actual heave motion. The estimation algorithm is adaptive in terms of changes in the sea states. Results will be given using real experimental data from model tests of a 3 meter long SES.

A Study on Stoma Arrangement of Air-Cushion Lamination and Numerical Simulation of the Pressure Field

Cushion has a wide range of applications in engineering. It is a new attempt to use it in the field of printing and packaging lamination process, to get a numerical simulation study analyzes for the distribution of the formation pressure of the air cushion pressure chamber. On the basis of analysis of the principle of air-cushion laminated device, make it clear for the requirements of the air cushion pressure distribution, pressure distribution from a single stomatal mathematical model, using ANSYS finite element software, numerical simulation of multi-stoma pressure distribution. The results showed that: stomata arranged in the form of cushion thickness, stomatal spacing and stomatal row spacing uniformity of the distribution greater impact on the cushion pressure; small stomatal spacing and stomatal row spacing will help improve the air cushion pressure distribution uniformity; reasonable cushion thickness stomatal spacing and stomatal row spacing, the selected diameter of the pores smaller cushion pressure distribution uniformity.

Intelligent air-cushion tracked vehicle performance investigation: neural-networks

Intelligent Air-Cushion Tracked Vehicle (IACTV) is intended as an alternative to conventional off-road vehicles, which are driven by track system and air-cushion system. To make IACTV as efficient as possible, proper investigation of vehicle performance is essential. However, most relevant factors that affect the competitive efficiency of the air-cushion tracked vehicle are the tractive effort, motion resistance and power consumption. Therefore, an Artificial Neural-Network (ANN) model is proposed to investigate the vehicle performance. Cushion Clearance Height (CH), and Air-Cushion Pressure (CP) are used at the input layers while Power Consumption (PC), Tractive Effort (TE) and Motion Resistance (MR) are used at the output layers. Experiments are carried out in the field to investigate the vehicle performance and compared with the results obtained from ANN.

Cushion pressure control system for an intelligent air-cushion track vehicle

This paper presents the control system of cushion pressure for the developed intelligent air-cushion track vehicle (IACTV) for operating on swamp terrain and wet fields. A novel auto-adjusting supporting system is designed for the vehicle’s intelligent air-cushion system. Focusing on minimizing the total power demand of the vehicle, an optimization model has been established, for examining the effects of vehicle parameters and load distribution on power consumption by controlling air-cushion pressure. Then optimum cushion pressure is determined based on the developed optimum pressure — sinkage relationship and the pressure in the cushion chamber is controlled by the Fuzzy controller by maintaining volume flow rate and continuously monitored by the pressure sensor attached with the cushion chamber. The ultrasonic displacement sensor is used to measure the sinkage of the vehicle. The output voltages of the ultrasonic displacement are used to operate the pull-in solenoid switch through the microcontroller which closes the circuit of the compressor motor. Distribution of vehicle load to the air-cushion system is controlled by Fuzzy Logic controller by maintaining the inside pressure of the cushion.