Low Air Consumption Research Articles

Study on energy-saving applications of vacuum ejectors across various operational demands

Vacuum suction technology is a pivotal innovation within the Industry 4.0 revolution. Ejectors serve as the core of vacuum systems with distinct advantages such as simple structure, low cost, and ease of operation. However, traditional fixed ejectors suffer from low efficiency, energy waste, and poor adaptability. This study aims to optimize the design of vacuum ejectors to meet various requirements, achieving energy efficiency and high performance in automated production. On this basis, an energy-saving vacuum system based on dual ejectors is proposed, which can switch between single and dual ejectors depending on different working stages. When the vacuum reaches 90 kPa, the required motive pressure and the entrainment ratio are selected as the screening indicators for the vacuum ejector. A two-dimensional axisymmetric model is established and verified through experimentation. The key parameters are identified through a single-factor analysis. A multi-factor analysis is employed to determine the recommended values for each parameter and their respective applications. The energy-saving effects of the optimized ejectors are evaluated in conjunction with the automated processes. The findings indicate that the vacuum system based on dual ejectors can achieve rapid response and low air consumption. This paper contributes to advancing the research on energy-saving applications of ejectors.

Аналіз впливу похибок вимірювання на абсолютні похибки експериментального визначення ККД вентилятора

The subject of research in this article is the experimental determination of the characteristics of fans of turbofan engines with a high and ultra-high bypass ratio. Increasing the efficiency of fans of engines of the specified class requires solving many complex interrelated problems, one of which is the determination of characteristics based on test results. The goal is to substantiate the need to use a method based on the determination of torque and the formation of requirements for the accuracy of its measurement. Tasks: clarification of previously obtained relationships between measurement errors and accuracy of determination of efficiency and air flow, formation of universal dependencies that allow analysis of absolute errors of determination of efficiency of any fan or compressor based on known measurement errors, analysis of the accuracy of alternative methods of organization of measurements and calculations the specified parameters, a comparative study of the specified methods and the formation of recommendations for their practical use on the example of the characteristics of a real fan. The following results have been obtained: the formulas that relate the absolute errors of calculating the efficiency and air flow with the absolute errors of the measured parameters (mathematical models of errors) have been clarified, as well as the requirements for the accuracy of the torque measurement necessary to determine the efficiency with the specified accuracy have been specified. The scientific and practical novelty of the results obtained is as follows: the mathematical models of errors in determining the efficiency and air flow in the fan have been clarified, which connect the errors of the calculation results with the errors of the measured parameters, because of the use of these models, experimental methods of determining the characteristics of compressors and fans have been developed; for the first time, the distribution of errors in the entire area of determining the characteristics of a specific fan was analyzed in detail. It is shown that the errors in determining the efficiency of the fan depend significantly on the degree of pressure increase and air flow. At small values of these parameters, the errors increase significantly. In the area of low engine operating modes (close to the area of the low air consumption), the errors in determining the efficiency based on the processing of the measurement results are so large that a reliable determination of the efficiency becomes practically impossible without the involvement of additional information, which can be used as the calculated characteristics of the fan, and as well as the mathematical model of the engine and the results of measuring parameters of the work process in other nodes, except for the fan itself.

Research into the Aerodynamic Attenuation of Hot-Melt Adhesive Fibers Produced by Multihole Melt-Blowing Nozzles

Air consumption in the melt-blowing process represents one of the major costs involved in the production of thin fibers. In the present work an experimental study is conducted on two multihole melt-blowing nozzles for manufacturing styrene–butadiene–styrene based hot-melt adhesive fibers in order to assess their fiber attenuation capability. With this purpose in mind, fiber diameter, fiber temperature, fiber bending, and air velocity were measured experimentally, and the steady-state quasi-one-dimensional longitudinal momentum equation of the slender fiber was integrated numerically in the nozzle postextrusion region and solved for aerodynamic force prefactor K, as it appears in Matsui’s drag coefficient correlation. A measure of fiber attenuation efficiency is proposed in terms of prefactor K and other nozzle geometrical and process operating parameters, which indicates the capacity of the nozzle to produce thin fibers with low air consumption. The results indicate that increasing nozzle air tilt angle, prefactor K, and air–polymer kinematic viscosity ratio in turn increases fiber attenuation efficiency. Working conditions are provided for each nozzle design that allow thin hot-melt-adhesive melt-blown fibers to be produced in a cost-effective manner. Furthermore, a formula is provided for estimating the melt-blown fiber attenuation rate in terms of multihole nozzle geometrical and process operating parameters. The results obtained in this work will help to reduce unnecessary energy consumption of melt-blowing equipment.

Water spray reactor for ammonia removal via air stripping: An evaluation on mass transfer and process efficiency

This paper offers a technical assessment of a developed reactor for ammonia removal via air stripping method. Optimum operational conditions were determined by experimenting numerous major parameters such as water flow, air flow, initial TAN (Total Ammonia Nitrogen) concentrations, pH, and orifice diameter of nozzles. It was found that water flow of 10 L/min, air flow rate at 120 L/min, and pH 11 were of significant parameters that facilitated higher ammonia removal efficiency up to 99 % after 7 h of experimental run with KLa = 0.0114 min-1. Empirical mathematical expression generated by employing Buckingham’s π theorem was shown to be a good fit (R2 = 0.992) to identify the relationship among Reynolds number, Weber number, and mass transfer coefficient KLa. Our newly developed reactor demonstrated satisfying performance with relatively lower air consumption (2016 L air/L liquid) compared to that of jet loop reactor (2266 L air/L liquid) and water-sparged aerocyclone (2394 L air/L liquid). The future development of this air stripping device is propitious since our reactor also enables advantages e.g., adjustable input volume and simple maintenance from scaling and fouling.

Parameter Sensitivity Analysis on Dynamic Coefficients of Partial Arc Annular-Thrust Aerostatic Porous Journal Bearings

Aerostatic bearings are widely used in high-precision devices. Partial arc annular-thrust aerostatic porous journal bearings are a prominent type of aerostatic bearings, which carry both radial and axial loads and provide high load-carrying capacity, low air consumption, and relatively low cost. Spindle shaft tilting is a resource-demanding challenge in numerical modeling because it involves a 3D air flow. In this study, the air flow problem was solved using a COMSOL software, and the dynamic coefficients for tilting degrees of freedom were obtained using finite differences. The obtained results exhibit significant coupling between the tilting motion in the x-and y-directions: cross-coupled coefficients can achieve 20% of the direct coefficient for stiffness and 50% for damping. In addition, a nonlinear behavior can be expected, because the tilting motion within 3°, tilting velocities within 0.0012°/s, and relative eccentricity of 0.2 have effects as large as 20% for direct stiffness and 100% for cross-coupled stiffness and damping. All dynamic coefficients were fitted with a polynomial of eccentricity, tilting, and tilting velocities in two directions, with a total of six parameters. The resulting fitting coefficient tables can be employed for the fast dynamic simulation of the rotor shaft carried on the proposed bearing type.

Test of a New Low-Speed Compressed Air Engine for Energy Recovery

The paper presents a new design solution for the multi-cylinder compressed air engine, described in the PL 216801 patent. A characteristic feature of the engine is its double-piston operation with pistons working in pairs in opposition and a reciprocating movement in toroidal cylinders. The energy of compressed air was used more effectively in the described engine than in the solutions known so far. Comparing the engine built in accordance with the PL 216801 patent with the parameters of the MP165 and MP3000 engines, lower air consumption in relation to the power generated on the shaft is demonstrated. The described engine uses only one crankshaft and one straight complex shaft, which constitutes an innovative combination of pistons, while maintaining the same engine operation as in the case of two crankshafts operating with phase shift and working chamber shift. Such a solution results in a reduction in the harmful space occurring at the beginning of the power stroke to the value close to “zero”—the necessity to maintain the minimum distance between the pistons working in one cylinder when they are at their closest exists only to for the sake of collision-free operation—which is very desirable for the compressed engine operating with a shift of the working chamber. The mechanical efficiency of the engine has also been improved by guiding the pistons on the complex shaft, and the number of kinematic nodes was decreased by applying only three connecting rods supporting six pistons, which also makes it possible to improve the power and mass relation by approximately 25% in comparison with the currently known engines of similar power.

Effect of Critical Variables on Air Dense Medium Fluidized Bed Coal Drying Efficiency and Kinetics

Calorific value, as a key component for fuel quality assessment, directly affects the thermal power plants' efficiency. While high-quality coal is consumed as metallurgical coal, low-rank coals are used by coal-fired power plants. The high moisture content of the thermal coals significantly influences their heating values. In this study, the drying performances of the fixed bed and air dense medium fluidized bed (ADMFB) dryers were investigated under the superficial air velocity of 15-18 cm/s, inlet air temperature of 55-75 oC, and up to 80 minutes of operation. Low air consumption is an intrinsic characteristic for ADMFB, while a low-temperature range for drying air was selected to address the coal-fired power plants' waste heat. It was found that an increase in air velocity and temperature favored the drying efficiency of both systems (i.e., 18 cm/s and 75 oC), with the temperature being more effective than the air velocity. The ADMFB dryer removed comparatively more moisture than the fixed bed for the shorter drying durations. For example, for 10% moisture reduction at 75 °C, the ADMFB dryer needed 5 minutes less time than the fixed bed. The fitting quality and goodness of serval well-known thin-layer models for describing fluidized bed and ADMFB coal drying kinetics were assessed by several models and statistical evaluators, respectively. It was found that the Middilli & Kucuk model best describes the fixed bed coal drying (i.e., R2=0.999, RSE=0.001, RMSE=0.008), while the Page model much properly simulates the ADMFB coal drying (i.e., R2=0.998, RSE=0.002, RMSE=0.009).

STUDY OF THE EFFECT OF AIR CONSUMPTION, LIQUID LAYER HEIGHT AND TEMPERATURE ON THE PROCESS OF FLOTATION SEPARATION OF GROUND PLASTICS

For separation of plastic wastes (polyamide (PA), acrylonitrile butadiene styrene (ABS) andpolystyrene (PS)), a flotation method is proposed. Using this method, the effect of air consumption, liquid layerheight and temperature were studied. As surface-active substances (surfactants), polidocanol, sulphanole and amixture of surfactants containing sodium laureth sulfate and diethanolamide were used.To analyze the research results of flotation separation of a mixture of ground plastic wastes, the extraction of thefloating component e and the purity of the concentrate β were calculated.The research results on the extraction of polystyrene from the air consumption at various concentrations of amixture of surfactants show that the extraction has a maximum at a certain air consumption. At low air consumption,the process is inefficient, since the working volume of the liquid is not saturated enough with gas bubbles. If theoptimum value of air consumption is exceeded, many gas bubbles are formed that are not involved in the flotationprocess. Such bubbles, moving through a liquid, can create turbulent flows that impede flotation of particles. Whenmoving in a turbulent liquid flow, the bubble-particle complex is prone to destruction, as particles and bubbles havedifferent inertia (mass). In addition, it may be concluded that the air consumption value at which the maximumextraction of the floating component is achieved depends on the type of polymer and surfactant. The air consumptioneffect nature at different concentrations of surfactants is not changed – only the floating component extractionchanges.The research results on the extraction of polystyrene from the aerated liquid layer height at variousconcentrations of a mixture of surfactants indicate that at a low height of the aerated liquid layer the probability ofcollision of a plastic particle with an air bubble is low and some potentially floating particles sink to the bottom ofthe device, without having time to collide with an air bubble. The optimum height of the processed liquid layercorresponds to a certain air consumption. When the liquid layer height is less than optimal, the achievement of therequired extraction degree of the dispersed phase is possible, for example, with an increase in air consumption.When assessing the effect of liquid temperature on the flotation process, it was found that increasing the liquidtemperature above 20°C leads to a sharp decrease in the ABS and PS extraction. This is possibly due to the fact thatthe dependence of the foaming capacity of surfactants on temperature is characterized by solubility curves and formost surfactants they have an extremum. Probably, an increase in the solution temperature leads to the dehydrationof the dissolved surfactant molecules. Moreover, they separate as an independent macrophase, which leads to adecrease in the number of surfactant molecules involved in the flotation process.

Numerical Modelling and Analysis of Hydrostatic Thrust Air Bearings for High Loading Capacities and Low Air Consumption

The paper presents a numerical simulation study on hydrostatic thrust air bearings to assess the load capacity, compressed air consumptions, and the dynamic response. Finite Difference Method (FDM) and Finite Volume Method (FVM) are combined to solve the non-linear Reynolds equation to find the pressure distribution of the air bearing gas film and the total loading capacity of the bearing. The influence of design parameters on air film gap characteristics, including the air film thickness, supplied pressure, depth of the groove and external load, are investigated based on the proposed FDM model. The simulation results show that the thrust air bearings with a groove have a higher load capacity and air consumption than without a groove, and the load capacity and air consumption both increase with the depth of the groove. Bearings without the groove are better damped than those with the grooves, and the stability of thrust bearing decreases when the groove depth increases. The stability of the thrust bearings is also affected by their loading.

Analysis of the Weft Insertion Process and Development of a Relay Nozzle Concept for Air-Jet Weaving

Air jet weaving is the most productive method for the production of fabrics. However, the energy consumption of air jet weaving machines is signifi cantly higher than the consumption of other weaving machines. Almost 80% of the energy consumed can be attributed to the losses at the relay nozzles. At the Institut fur Textiltechnik of RWTH Aachen University, Aachen, Germany diff erent novel relay nozzle geometries with lower air consumption have been developed on the basis of simulations and trials. The simulations have shown potential energy savings up to 50% compared to conventional relay nozzles. Furthermore, practical validations of the results of these simulations have been done. The velocity, stagnation pressure and volume fl ow were measured in the reed channel. In addition, an energetic and economic evaluation of the best relay nozzle geometry was done. The evaluations have shown that up to 50% of the energy can be saved.

Energy-saving compression valve of the rock drill

The relevance of the research is due to the necessity to create pneumatic rock drills with low air consumption. The article analyzes the reasons for low efficiency of percussive machines. The authors state that applying a single distribution body in the percussive mechanism does not allow carrying out a low-energy operating cycle of the mechanism. Using the studied device as an example, it is substantiated that applying a compression valve with two distribution bodies separately operating the working chambers makes it possible to significantly reduce the airflow. The authors describe the construction of a core drill percussive mechanism and the operation of a compression valve. It is shown that in the new percussive mechanism working chambers are cut off the circuit by the time when exhaust windows are opened by the piston and air is not supplied into the cylinder up to 20% of the cycle time. The air flow rate of the new mechanism was 3.8 m3/min. In comparison with the drill PK-75, the overall noise level of the new machine is lower by 8-10 dB, while the percussive mechanism efficiency is 2.3 times higher.

Comparison of an Effervescent Nozzle and a Proposed Air‐Core‐Liquid‐Ring (ACLR) Nozzle for Atomization of Viscous Food Liquids at Low Air Consumption

AbstractRecent results regarding the effervescent atomization of viscous food‐based liquids reveal that an unfavorable slug flow is formed inside the nozzle for low gas to liquid ratios (GLRs). As a result, a very unsteady spray drop size is formed, which leads the nozzle to be unsuitable for an implementation in spray drying. In this study, we propose a modified nozzle design named ACLR (Air‐Core‐Liquid‐Ring) to establish the favorable annular flow inside the exit orifice. High‐speed imaging proved that the desired flow pattern was present in the investigated GLR range of 0.015–0.414 and for liquid viscosities of 0.001–0.308 Pa·s. Comparison with a conventional effervescent nozzle showed similar values of the time averaged Sauter mean diameter of the spray drops. Considering the temporal unsteadiness of the spray drop size, a considerable reduction can be achieved for viscous liquids and low GLRs by the proposed ACLR nozzle.Practical ApplicationsFor an economic spray drying process, the highest possible dry matter content prior to drying is aspired. However, as feed viscosity increases rapidly with an increase in dry matter content, atomization is considerably hindered. The effervescent nozzle, originally invented in the field of combustion science, is reported to atomize viscous liquids into small spray drops at low gas consumption. Recent results of our group reveal that an unsuitable slug flow is formed inside the nozzle when food‐based liquids with elevated viscosities are atomized at low gas to liquid ratios. Consequently, the effervescent nozzle is not suitable for an implementation in spray drying. In this study, we propose a modified nozzle design that overcomes the drawbacks of a conventional effervescent nozzle. The Air‐Core‐Liquid‐Ring nozzle offers the possibility to save large amounts of drying energy of existing spray dryers as higher concentrated feeds might be used.

Low air consumption control in pneumatic positioning system

The paper presents an idea of an open-loop control of a pneumatic positioning system consisting of a pneumatic cylinder, inexpensive measurement system and four on-off switching valves. A strategy of four pulses on-off control trajectory for implementation of a determined piston displacement without an overshoot is presented. Parameters for the control are determined by the application of artificial neural nets that have to be trained before the application. The strategy is nearly time-optimum one and results in a short control time, a quiet valves action and a significant reduction of the compressed air consumption in the comparison to algorithms used in pneumatic positioning systems. This way of control was investigated in many simulation experiments and in tests performed in a laboratory as well. It can be a basis for construction and development attractive, low-cost, economic pneumatic positioning systems.

A lateral active suspension for conventional railway bogies

The present paper describes an active centring system for railway vehicles. The proposed solution is based on lateral pneumatic actuators placed between bogie and car body connected to the vertical secondary suspension air springs. The objective of the developed centring system is twofold: the improvement of the curving behaviour of the train and the decrease of the lateral acceleration perceived by the passenger in curve negotiation thanks to the reduction of the ‘souplesse’ coefficient. The system is described in detail in the paper. Results from simulations are included considering a bidimensional model of the vehicle, and a detailed model of the air spring and control valves. The performance in curve negotiation of a vehicle equipped with this system and a conventional one is compared. Specifically, lateral displacements of the secondary suspension, roll angle and lateral accelerations are analysed. The results show noticeable performance improvements in the vehicle curving behaviour. The proposed centring system can be implemented in a conventional bogie without special design requirements; and due to the low air consumption, additional pressurised reservoirs are not required.

Designing an energy-saving pneumatic vacuum pad using computational fluid dynamics for automated manufacturing system

The current paper is concerned with the development of a new energy-saving vacuum pad using computational fluid dynamics (CFD)-technique. CFD which is a powerful tool to provide an effective insight into the flow field numerically. Nowadays, application of pneumatic vacuum pads may be found in many different real industries, especially in the field of automated manufacturing system, like the automatic conveyer system, automatic assembly line, semiconductor industry as well as wafer factory, etc. Traditional vacuum pads generally utilize nozzles to create the effect of vacuum. In the current paper, however, a new idea to generate the effect of vacuum is proposed by designing a structure similar to that of an aerostatic bearing. In details, the air is guided to flow through a well-designed restrictor inside the vacuum pad and flow out through the outlet between the vacuum pad and the sucked workpiece. Therefore, according to Bernoulli's equation, the air pressure near the centre-line of the vacuum pad decreases because of the increased airflow velocity. Consequently, the effect of vacuum is generated. To achieve two preset requirements, that is, large suction-force output and low air consumption, the commercial CFD-RC software is utilized to simulate the airflow field and design the optimal geometry inside the vacuum pad. Experimental results further prove that the new vacuum pad with two significant features is successfully developed and implemented in the current study.

Determination of Characteristics for Electrically Modulated Pneumatic Control Valves using Isothermal Chambers

In the present paper, an automatic test bench is developed for determining the main characteristics of electrically modulated pneumatic control valves using isothermal chambers. In particular, the pressure-flow rate characteristics can be obtained by simply measuring the pressure response inside the isothermal chamber during charge and discharge of air to the chamber. The proposed test bench has a shorter measurement time of only seconds and a lower air consumption as compared to the improved conventional method. Furthermore, the frequency dynamic characteristics with volume load can be measured more accurately owing to the use of an isothermal chamber as a load chamber. The high measurement efficiency and energy savings of the developed test bench are demonstrated herein.

A Steam-Augmented Gas Turbine with Reheat Combustor for Surface Ships

The steam-augmented gas turbine (SAGT) concept has attracted attention because of its benign level of NOx emission, its increased fuel efficiency, and significant, cost-effective increments of output power, particularly when moisture injection is increased to levels approaching 50% of air flow. Such high levels of moisture consumption distinguish the SAGT engine from commercial steam-injected gas turbines where steam flow may be less than 15% of air flow. At the high 50% levels, the SAGT burner would operate near stoichiometric combustion ratios with specific powers exceeding 570 hp-sec/lb. In a previous study, an intercooled, steam-augmented, gas-turbine concept was examined for its applicability in the Navy's DDG-51 class ship environments, which achieves efficiencies approaching the Navy's intercooled regenerative (ICR) engine, and an impressive compactness that arises from the high specific power of steam and low air consumption. A newer SAGT engine concept, described herein, dispenses with the intercooler, but adds a low-pressure reheat combustor. At the most efficient operating points, the efficiency of this new reheat SAGT engine at 43% exceeds the efficiency of the ICR engine, while exhibiting the compactness of the previous SAGT concept. Tabular and graphical simulation data comparing the baseline engine, with the ICR and other engine simulations, show that the maximum efficiency of the new SAGT engine occurs at powers required for cruising speeds. Since a DDG operates near cruise conditions for the majority of its mission time, a SAGT plant uses less fuel than the ICR plant. Moreover, since it eliminates the intercooler, developmental work on member elements, largely derivable from off-the-shelf components, is reduced. Even with conservative cost estimates, the SAGT plant is quite competitive on a first-acquisition cost basis with the current gas turbine in the fleet.

振動条件下における“スタンドライシール”の特性と就航実績

New types of oil lubricated stern tube seal, Type EVS, EVS II, EVS III, which consist of lip seals and segmented circumferencial seals, have been developed. In the new seal, compressed air is supplied to the seals to maintain a stable air barrier between sea water side and oil side of the stern tube bearing, separating them completely.These new types of stern tube seal have employed segmented circumferencial seals as one of the sealing elements possessing many improved features compared with the conventional lip type stern tube seals, which seal both sea water and lubricating oil by narrow contacting area of the lips on the surface of the sleeve liner.This paper presents air consumption and seal performance of Type EVS under special vibrating conditions given at the laboratory test, and also presents the same air consumption and seal performance of Type EVS and EVS II in practical use on the vessels.The test results show good seal performance, and low air consumption within the range where no influence is given to the pneumatic equipments on the vessels. The results of practical use on the ships have also showed good seal performance and low air consumption, same as the results under the abovementioned bench-testing.

An Improved Spinning Top Homogeneous Spray Apparatus

An apparatus is described which produces homogeneous mists or clouds of solid particles of any desired size. As in Walton's original model liquid is sprayed by a Beams high speed air-driven top, but an improved performance has been achieved by utilizing a property of high speed air films so that automatic extraction of unwanted satellite droplets, better running characteristics over a wider range, simplified construction, and low air consumption are obtained.