Expansion Of Air Research Articles

Experimental evaluation of compressed air energy storage as a potential replacement of electrochemical batteries

This work reports on an experimental compressed air energy storage system used to run a three-phase electric generator to feed AC loads. The same loads are also supplied by a battery-inverter setup and both are compared in terms of performance and also from a physical footprint. At operating pressure of 10–12 bar and storage pressure of 80–100 bar, a 12 V battery is equivalent to 12 m3 of air storage space. This space is a function of the air motor power and also coupling with the generator, if it is direct or through a gearbox. The mathematical calculations estimated 27 % higher energy and power results, which are attributed to kinetic and mechanical losses in the air expansion and gearbox friction, respectively. This work is expected to pave the way for further experiments and innovation in specialized air handling turbines for large-scale energy storage. The physical footprint of the conversion system is relatively small, especially if provisions for storage tanks are made underground like gas station tanks.

Experimental Study on the Propagation Law of Explosive Stress Wave in Cement Mortar with Weak Layers

The weak layer has good attenuation performance when it comes to the explosive stress wave, which can be used in protective structures. In this paper, a cement mortar specimen was designed, cast, and tested. Under inner explosion, due to the expansion of air in the explosive hole, the tensile cracks formed around the explosive hole are mainly in a damage pattern. In ordinary cement mortar, the transmittance is decreasing as the distance increases. At a distance of 8 cm to 14 cm from the explosive center, the average transmittance is 50.16%, 12 cm to 18 cm, while the average transmittance is 62.89%, increasing by 12.73%. Adding one weak layer into the cement mortar, the transmittance of one weak layer is 43.37%. The effect of increasing weak layers in short spacing is not obvious, and the transmittance of the second and third weak layer is about 80%, much less than the first layer. The softer the weak layer and the larger the wave impedance, the smaller the transmission coefficient is. The research proves that the weak layer has excellent attenuation performance when it comes to the explosive stress wave.

Climatic Effects of the Indian Ocean Tripole on the Western United States in Boreal Summer

Abstract The Indian Ocean tripole (IOT) is an independent mode of ocean–atmosphere circulation centered on the tropical Indian Ocean. This study explores the physical mechanisms of the IOT affecting the western United States climate variation during the boreal summer. We find that the IOT is significantly correlated with both western United States summer surface temperature and precipitation anomalies. During positive IOT events, the westerly wind anomalies over the northern Indian Ocean are intensified by two cross-equator airflows over the tropical eastern Indian Ocean and the east coast of Africa. The resulting convergence of air over the northern Bay of Bengal–Indochina Peninsula–northern South China Sea (NBB–IP–NSCS) region (15°–25°N, 80°–125°E) exacerbates the surplus precipitation there. Serving as a heat source, these NBB–IP–NSCS precipitation anomalies can excite a circumglobal teleconnection (CGT)-like pattern that propagates eastward from west-central Asia toward North America along the Asia subtropical westerly jet, further influencing local circulation anomalies. Development of strong anticyclonic circulation over the western United States enhances descending motion and divergence there, resulting in negative precipitation anomalies. This circulation anomaly also induces the diabatic heating anomalies through allowing more solar radiation to reach the ground surface, further increasing the surface temperature anomalies. Meanwhile, the increased tropospheric temperature also raises local surface temperatures by modulating the adiabatic air expansion and compression. Ultimately, the CGT-like pattern associated with NBB–IP–NSCS precipitation anomalies sets up an atmospheric bridge by which the IOT can impact summer climate in the western United States.

Features of Pyrite Thermal Expansion in Air

Features of Pyrite Thermal Expansion in Air

Experimental Regulating Parameters of Bladder-Type Hydraulic Accumulator

Experimental regulating parameters of the non-stationary expansion of air inside a bladder-type hydraulic accumulator, working with the simple short pipeline, are presented in the paper. The technique of continuous online monitoring of changes in time of volume and absolute air pressure inside the hydraulic accumulator during the discharge process has been improved. Three series of experimental studies of transient gas processes inside the accumulator at different values of the average volume flow rate are made. Tendencies of change of the integral parameters of the hydraulic accumulator are obtained and analyzed depending on the serial number of the discharge cycle. A general dependence of dimensionless storage volume <i>Kreg</i> on the polytropic index <i>n</i> in series # 1–3, approximated by single power-law dependence, is obtained. The systematic changes of integral parameters in each subsequent discharge cycle can be explained by the non-stationary transient thermodynamic processes in air inside the accumulator until the thermodynamic equilibrium with the ambient air parameters is reached.

A Review of Recent Research and Application Progress in Screw Machines

Screw machines, mainly including single-screw type and twin-screw type, have gone through significant development and improvement during the past decade. This paper reviews the relevant studies available in the open literature for acquiring insight into and to establish the state of the art of the research and application status of screw machines. The related research on different aspects, which would affect the performance and reliability of screw machines includes rotor profile and geometric characteristics, thermodynamic modelling, vibration and noise, lubrication and wear, control of capacity and built-in volume ratio, and liquid injection technology. In the aspect of thermodynamic modelling, the available methods, i.e., empirical or semi-empirical model, lump model, and 3D CFD model, adopted for the performance prediction and optimal design of screw machines are summarized. Then, the review covers the application status of screw machines in the fields of air compression and expansion, refrigeration and heat pump, organic Rankine cycle (ORC), and other popular applications, with an emphasis on the reported performance and progress in technologies of screw machines. Finally, conclusions and perspectives for future research in the area of screw machines are presented. The review provides readers with a good understanding of the research focus and progress in the field of screw machines.

Performance and economic evaluation of CO2 (R744) air conditioning system driven by compressed air engine

Traditional building air conditioning uses electricity or thermal energy to drive the refrigeration cycle. The energy released by the expansion of compressed air can also be used for driving the refrigeration cycle. Moreover, the expanded low-temperature air can be used in the air conditioning system too. In this paper, three forms of CO2 air conditioning systems driven by novel reciprocating piston compressed air engines were designed, namely EAGC (Exhaust Air for Gas Cooler), EAS (Exhaust Air for Sub-cooler), and EASC (Exhaust Air for Space Cooling), to analyze the performance and economics of CO2 air conditioning systems combined with compressed air energy storage technology. Twenty-seven typical cities were selected in different climate regions in China to evaluate the systems' performance and running cost under outdoor temperature changes and different electricity prices. The results show that compared with the electricity-driven CO2 air conditioning system, the three systems can greatly improve the system COP (Coefficient of Performance) but still cannot reach the performance level of the conventional freon refrigeration systems. However, in cities like Beijing and Shanghai with the large peak-to-valley electricity price difference, EASC system compared to the electricity-driven R410A air conditioning system running costs are lower, the average running cost per hour can be saved 11.96% and 16.35%, respectively. This means that the CO2 air conditioning system with compressed air energy storage technology has a certain economic application value and can be popularized on reasonable occasions. This innovative system design can help solve the contradiction between supply and demand of building energy, realize leisure energy consumption, and reduce the economic cost of energy consumption on the demand side.

Study on some aspects of Stirling engine: A path to solar Stirling engines

The present work emphasises on energy conversion through Stirling engines that have the ability to utilise renewable heat sources more easily and economically, making less noise. It's a heat engine working by compression and expansion of air or other gases in a cyclic pattern, creating a temperature gradient. These engines can also be considered as one of the best sources of clean energy systems that may have potential to play a vital role in upcoming years. In this paper, we will look at the history of the Stirling engine, its working methodology, and the numerous configurations that it can be built in. We will also look at the advantages and disadvantages of the Stirling engine, how it can be used in different ways, and how new technology is being made using the Stirling model, especially in the field of Solar Stirling engines.

Research on the Mechanism of Rijke Tube Self-excited Sound

Combustion equipment generates self-excited vibration called combustion vibration. The noise generated by this ｒ vibration is undesirable because it can damage structures and degrade their performance. Because this vibration phenomenon is complex, it is very difficult to model. Therefore, the purpose of this study is to attempt modeling of Rijke tubes, which are prone to combustion vibration from the perspective of heat transfer engineering, and to reproduce the sound pressure waveform of Rijke tubes using the cellular automaton (CA) method. Since previous studies have summarized the properties of a Rijke tubes and the rules of the CA method, we referred to them and incorporated them into this study. Previous studies have shown that the particle velocity in the heat source section including time delay causes self-excited oscillation. In this study, we derived an equation for the particle velocity with time delay by using heat transfer engineering based on the expansion and contraction of air. The sound pressure waveform of the Rijke tube could be quantitatively reproduced by numerically calculating the time of passage through the heat source and determining the number of time delay from time to time．

Thermodynamic investigation of asynchronous inverse air cycle integrated with compressed-air energy storage

A novel integrated system for heating, cooling, and compressed-air energy storage (CAES) is analysed from a thermodynamic perspective. The system is based on asynchronous air compression and expansion to take advantage of daily ambient temperature oscillations, electricity pricing variations, and the discontinuous availability of renewable sources. Furthermore, the integration of CAES with an open inverse air cycle eliminates grid and generator losses incurred in the supply of thermal energy for end-use heating and cooling applications. The novelty is represented by using the storage vessel as a heat exchanger interfaced with the external environment, which acts as a heat source or sink in relation to the ambient conditions and phase of operation. To ensure wide applicability, the analysis is kept on a fundamental level, without explicit reference to specific technical details of the components. The sole technical premise is represented by a commercially available vessel for air storage featuring a volume of 10 m3 and a maximum operating pressure of 12 bar. This choice may be interpreted as a constituent unit for a modular system that can be easily scaled-up to the required capacity. Two configurations are proposed: one for air conditioning and sanitary water production, and the other for refrigeration. The first configuration yields a global COP of 1.49 and a second law efficiency of 0.149. The second one may produce heating at temperatures as high as 400 °C and refrigeration at -90 °C with a global COP of 1.30 and a second law efficiency of 0.192. The effects of losses in the compressor, expander, and heat exchangers, as well as heat transfer in storage vessel, are discussed, accounting also for condensation/evaporation due to the air humidity.

Periodic forced flow in a nanosecond pulsed cold atmospheric pressure argon plasma jet

This paper is devoted to the study of the argon flow modification in a cold atmospheric pressure plasma jet driven by nanosecond high voltage (HV) pulses, from single to multiple HV shots applications. A schlieren optical bench has been designed in order to visualize the argon flow downstream expansion in quiescent air, for moderate flow rates below 1 standard liter per minute. A coupled approach is used between charge coupled device (CCD) schlieren imaging and intensified CCD (ICCD) plasma plume imaging, both time-resolved. It is shown that the application of only one HV pulse (i.e. single HV shot) is enough to disturb the flow. The disturbed flow exhibits ripple propagation, on a timescale similar to the flow velocity. When operating in double HV shots, the second ionization wave can be used as a probe, to instantly visualize the flow structure any time after the first HV pulse application. For some flow rates, the ripple can increase in amplitude up to the point when it strongly deforms, or even stops, the plasma plume expansion, after which it is entrained by the flow and the plasma plume retrieves its full usual expansion. When a series of HV pulses are applied, the maximal disturbance of the flow is achieved for a certain pulse repetition frequency (PRF), specific of each flow rate. It is associated with ripples alternation in the plasma plume, in a 3D helical-like arrangement. For greater PRF, the ripples progressively vanish, and the flow is clearly less disturbed. Once the ripples have vanished, increasing further the PRF does not change the plasma plume and flow structures. We suggest that the repetitive plasma ignition mechanically forces the flow inside the capillary with consequences on the global flow structure, similarly to a forced backward-facing step flow with actuator.

An approach for waste heat recovery of internal combustion engine: In-cylinder steam-air expansion

• An approach based on CSAE cycle was proposed for IC engine WHR. • Steam temperature has a greater effect on WHR potential compared with steam amount. • The NA mode is recommended for the steam expansion cylinder. • Engine brake efficiency can be increased by 7.0 percent points at most by CSAE cycle. • The proposed WHR approach has little effect on the engine BMEP. To recover waste heat and increase the fuel efficiency of internal combustion engines, an approach based on in-cylinder steam–air expansion is proposed, which has simpler design but higher practicality than previous methods. In the multi-cylinder engine, a cylinder is specially used for steam expansion (called steam expansion cylinder) without fuel entry and firing. The high-temperature steam generated by engine waste heat is injected into the steam expansion cylinder, in which it expands together with air and outputs effective work. The energy-saving potential and influencing factors of this approach were investigated on a six-cylinder natural gas engine through the simulation and some interesting findings were obtained. At the same engine operating conditions, the steam temperature has greater effects on waste heat recovery potential than steam amount. The cycle work of the steam expansion cylinder is improved largely by introducing air. However, if further increase intake pressure (e.g., greater than 0.4 bar), the improvement of cycle work in the steam expansion cylinder is not obvious, thus the naturally aspirated mode is recommended. When this approach is applied, the maximum brake mean effective pressure is approximately equal to the level of the original engine at 1600 rpm and 2000 rpm but slightly lower at 1200 rpm. Nevertheless, the brake efficiency of the engine has an obvious rise at all three speeds, which could increase by up to 5.7, 7.0 and 6.8 percentage points at 1200 rpm, 1600 rpm and 2000 rpm, respectively. Therefore, the proposed approach can effectively recover engine waste heat with little effect on power performance.

Identification of energy wastes through sound analysis in compressed air systems

This paper proposes a new approach which is able to identify energy losses of compressed air in any CAS based on acoustic energy emission. By means of a previously validated mathematical model, the inverse problem that finds air power lost over time from the sound generated by air expansion is solved. The developed method is tested in a laboratory scale while a tank is being emptied through artificial holes with different diameters in a pipe. Two supplying cases: continuous supply of compressed air to the tank and single filling of the tank are considered. All measurements are made in an anechoic chamber to record pure air expansion noise without any background sounds. The analysis shows that over certain range of leakage hole diameters there is a dependence between the generated sound pressure level and the mass flow and, therefore, the power loss. Thus, acoustic monitoring could be effective in leakage diagnosing in CASs, which is important for production energy efficiency management.

Development of a moving model rig with a large Reynolds number and measurement of aerodynamic drag

AbstractThe principles and techniques for developing a moving model rig (MMR) driven by compressed air were introduced for moving model tests at large Reynolds numbers (). A corresponding methodology for the accurate measurement of the aerodynamic drag was developed. The main functions of the MMR included the acceleration of the trailer and the model, the deceleration of the trailer, and the deceleration of the model. The acceleration power was provided by the expansion of the compressed air in a pipe, and the deceleration of the model came from the relative motion between the permanent magnet and the static iron deceleration floor. The braking of the trailer was supplied by either a magnetic damping force or the compression of the air in the pipeline by the trailer piston. The free motion of the model in the test section followed the Davis equation. Based on this, a method for the measurement of the model aerodynamic drag using the measured acceleration data was proposed and experimentally demonstrated in an MMR developed in this work.

Adiabatic compressed air energy storage technology

Adiabatic compressed air energy storage technology

ENERGY BALANCE ANALYSIS BETWEEN ENERGY CONSUMED FOR THE COMPRESSION OF ATMOSPHERIC AIR UP TO 200 BAR, AND THE ENERGY PRODUCED FROM ITS EXPANSION DOWN TO ATMOSPHERIC PRESSURE ON NICHOLAS PITTAS’ PATENT ABOUT STORAGE AND CONTINUOUS PRODUCTION ENERGY SYSTEM

This paper provides the theoretical foundation the patents , of Nicholas Pittas related to storage and continuous production of energy via compressed air. Specifically, the energy balance between consumed energy, used for the compression of atmospheric air to high pressure and heat production within a specific number of stages, and the energy produced during the expansion of compressed air to atmospheric pressure. The heat produced is transported, via a thermal vector, to the expansion process to prevent ice formation in the .

Microtextural evidence for vesiculated tuff formation in Songaksan tuff ring, Jeju Island, Korea

Vesiculated tuff, containing submillimeter-size vesicles, is commonly found in Surtseyan and phreatomagmatic deposits. However, the processes and conditions of vesicle formation and preservation in granular substances have been poorly explored so far in spite of their potential importance in understanding the eruptive and depositional processes of these deposits. This study provides a detailed account of a vesiculated tuff in Songaksan tuff ring, Jeju Island, Korea, together with comparison with non-vesiculated tuffs. The vesiculated tuff, which is interpreted to have been emplaced by a wet pyroclastic surge, is poorer-sorted, poorer in fines, richer in coarser particles, and has lower porosity than the non-vesiculated tuffs. The pores are closed and have round margins surrounded by a fine-grained matrix. On the other hand, non-vesiculated tuffs, emplaced by either pyroclastic surges or fall, are composed of loosely packed ash aggregates and have large interconnected pores. We interpret that the vesicle formation in granular substances is possible only when the pores are water-saturated and airtight. Expansion of trapped gases is also necessary to produce the generally round shape of the vesicles. The gas expansion is possible only when the heat is transferred from the surrounding hotter pyroclasts into the gas bubbles. Vaporization of liquid water and gas exsolution from pyroclasts can be ignored. In order for the heat transfer to take place, the pyroclastic surge needs to be non-isothermal, having different temperatures of the solid and gas phases. The thermal disequilibrium of the surge can be maintained by continual mixing of cold ambient air and thermal expansion of the surge. The pyroclasts deposited from the surge need to increase the temperature of the trapped air/gases by only 3 K. Then, the trapped air/gases can overcome the yield strength of the surrounding wet ash matrix and expand. The essential conditions for vesiculated tuff formation, such as water saturation of pyroclasts and thermal disequilibrium of surge, are closely related with the properties of the diatreme-filling materials and the behavior of pyroclastic surges. Therefore, vesiculated tuffs can provide useful information on the eruptive and transport processes of Surtseyan and phreatomagmatic deposits in addition to the wet nature of tephra.

The multi-harmonic excitation characteristic of airflow piezoelectric generator

In order to improve the adaptive range of airflow velocity, an airflow piezoelectric generator based on multi-harmonic excitation is proposed. The flow field characteristics are obtained by CFD method, the acoustic vibration characteristics and variation with velocity of the excitation frequency are studied. The result shows that periodic compression and expansion of air are presented and a standing wave is formed inside the resonator, which can provide stable excitation source. The excitation frequencies are distributed on the acoustic modes of the resonator and captured. With different velocity segment, the excitation frequencies are different, and frequency conversion is presented from the first-order to the third-order and from the third-order to the first-order. The conclusions verify the feasibility of the multi-harmonic excitation energy exchange scheme, which is helpful to improve the flow velocity adaptive range of the airflow-induced vibration piezoelectric generator.

Experimental investigation of internal air flow during slow piston compression into isothermal compressed air energy storage

Compressed air could be a solution for the future mass storage of renewable energies. The isothermal compression and expansion of air by liquid piston is a solution that offers good performance and significant power. Lengthening the compression chamber and slowing down piston displacement may be advantageous for quasi-isothermal development. Presented here is an analysis of the internal air flow during slow piston compression inside a compression chamber with a very low stroke-to-bore ratio. The existence of two consecutive flow regimes is produced repeatably by 2D PIV (particle image velocimetry) measurement. First, a highly-structured regime develops with air speeds significantly higher than the piston advance speed, and a general recirculation of the air. The symmetry of this structure is confirmed with a simple flow distribution model. A second, more disorderly, flow regime then takes over for the remainder of the compression. The transition between the two regimes observed is also described, highlighting instabilities in the high shear zones in the transition from the first regime to the second.

Effect of an entrapped air pocket on hydraulic transients in pressurized pipes

The current research focuses on the analysis of different dynamic effects of an air pocket located at mid-pipe length on transient pressures based on experimental data. Different flow rates and air pocket volumes are analysed. Several features are identified in the pressure-head signal associated with the air pocket: initial pressure drop, higher maximum overpressure peaks, increased pressure wave damping and delay. These features result from the superposition of pressure waves associated with the entrapped air contraction and expansion. Smaller air pockets generate minor reflections, whereas larger air-pockets tend to disperse and artificially attenuate maximum pressures. Video recording images of the air pocket during the transient event allow observation of two types of behaviour: one associated with lower transients, characterized by an air pocket volume variation with a clear air–water interface; and another one associated with more severe transients in which air mixes with water. Finally, there is a critical air pocket volume, independent of the initial flow rate, that leads to the highest overpressures.