Sliding Vane Rotary Compressor Research Articles

Performance investigation and design optimization of novel rotating-cylinder sliding vane rotary compressors

Novel rotating-cylinder sliding vane rotary compressors (RC-SVRCs) are promising machines in energy conversion systems due to extremely low friction. However, three-dimensional visual investigations on geometrical optimizations of RC-SVRCs are highly limited. Besides, most flow mechanisms and leakage flow affected by geometric structures have not been fully revealed yet. Therefore, the sliding vane number, gap heights at vane tips and length-to-diameter ratio are numerically studied in this work. The results show that more sliding vanes (4∼12) lead to more uniform flow and temperature fields, lower mass flow rates and outlet temperature, less leakage between rotor and rotating cylinder. The mass flow rate, leakage mL1 between rotor and cylinder and leakage mL2 at vane tip of 8-sliding-vane scheme are 2.944 × 10−2, 9.949 × 10−4 and 3.692 × 10−5 kg·s−1, respectively. Gap height at vane tips has vital effects on flow fields. As the gap increases (0.01∼0.05 mm), mass flow rate and isentropic efficiency are decreased by 12.68% and 18.26%, the outlet temperature, leakage mL1 and mL2 are increased by 91.5 K, 69.60% and 22 times, respectively. High-temperature areas and leakage flow increase with the increase of cylinder length, which is recommended no longer than 0.6 diameters. This work allows making recommendations for designing RC-SVRCs.

Analysis, modeling and simulations of an innovative sliding vane rotary compressor with a rotating cylinder

A novel sliding vane rotary compressor with a rotating cylinder is proposed in this paper. The sliding vane dynamics analysis reveals that, compared with the traditional compressor, the friction loss at the sliding vane tips and between rotor and cylinder can be reduced to 0.25% and 10.23%. To numerically investigate the internal flow mechanism, a reliable three-dimensional simulation method is developed via Fluent 2020R1. Three pressure ratios are considered. During transient calculations, all parameters begin to fluctuate periodically after the fourth round. Both temperature and pressure for a single chamber reach the maximum near the exhaust port. As the pressure ratio εp increases from 5, 10 to 15, the outlet temperature increases from 496.9, 623.0 to 754.4 K and the mass flow rate decreases from 0.03089, 0.02946 to 0.02764 kg/s, the volumetric efficiency and isentropic compression efficiency decrease, with the maximum values of 97.14% and 90.33%. The gaps between the rotor and the cylinder and at the vane tips are 0.03 and 0.01 mm, but the leakage mass of the former is one order higher than that of the latter. The research can provide guidance for the design and practical application of sliding vane rotary compressors.

Impact of discharge port configurations on the performance of sliding vane rotary compressors with a rotating cylinder

With the increasing requirements of compressed gas energy storage systems for compressors and expanders, sliding vane rotary compressors are worth trying. To study the influence of different configurations of discharge ports on the performance of compressors, numerical simulations are conducted on the innovative sliding vane compressors with a rotating cylinder. The reliable Renormalization Group k-ε turbulent model is adopted in Fluent 2020R1. The results show that as the coverage angle increases, the averaged mass flow rates increase, the averaged exhaust gas temperature decreases and the leakage between the rotor and rotating cylinder and at sliding vane tips decrease. When the coverage angle increases from 15° to 45° at the central position angle of −28°, the volumetric efficiency increases from 89.38% to 92.65% while the isentropic efficiency increases from 76.43% to 86.19%. When the central position angles range from −28°, −23° to −18° at the coverage angle of 30°, the farther the discharge port is to the narrowest gap between the rotor and cylinder, the lower the outlet temperature, the less the leakage flow, and the higher the isentropic efficiency. The scheme with the central angle of −28° and coverage angle of 45° is recommended as the best one.

Performance evaluation of a novel dual vane rotary compressor

Sliding-vane rotary compressors have considerable advantages in comparison with other positive displacement compressors in terms of volumetric efficiency, and continuity of flow without pulsations. However, sliding-vane rotary compressors have relatively low pressure ratio. This paper presents a novel design of a two-stage sliding-vane rotary compressor in attempt to elevate the pressure ratio of that type of compressors. The basic design features of the novel design are illustrated along with the adopted design geometry after studying the effects of several geometrical factors and their practicality. After several trials, the first prototype of the two-stage sliding-vane rotary compressor has been manufactured and tested experimentally to evaluate its performance. The paper reports the preliminary results of the flow rate, pressure rise and power consumption at different rotating speeds. Comparison of the performance of each stage is also included and the benefits of using the second stage are highlighted. The paper also summarizes the design challenges encountered during its manufacturing in addition to the challenges to reduce inter-stage leakage and the applied solutions.

An intracooling system for a novel two-stage sliding-vane air compressor

Lube-oil injection is used in positive-displacement compressors and, among them, in sliding-vane machines to guarantee the correct lubrication of the moving parts and as sealing to prevent air leakage. Furthermore, lube-oil injection allows to exploit lubricant also as thermal ballast with a great thermal capacity to minimize the temperature increase during the compression. This study presents the design of a two-stage sliding-vane rotary compressor in which the air cooling is operated by high-pressure cold oil injection into a connection duct between the two stages. The heat exchange between the atomized oil jet and the air results in a decrease of the air temperature before the second stage, improving the overall system efficiency. This cooling system is named here intracooling, as opposed to intercooling. The oil injection is realized via pressure-swirl nozzles, both within the compressors and inside the intracooling duct. The design of the two-stage sliding-vane compressor is accomplished by way of a lumped parameter model. The model predicts an input power reduction as large as 10% for intercooled and intracooled two-stage compressors, the latter being slightly better, with respect to a conventional single-stage compressor for compressed air applications. An experimental campaign is conducted on a first prototype that comprises the low-pressure compressor and the intracooling duct, indicating that a significant temperature reduction is achieved in the duct.

Model based design of an intercooled dual stage sliding vane rotary compressor system

Energy saving is currently one of the most important driving factors for innovation all over the world. With reference to global electricity consumptions, electrical energy for compressed air production accounts for 4-5%. Among the rotary compressor technologies, Sliding Vane Rotary Compressors (SVRC) are characterized by noteworthy specific energy consumptions and demonstrated an unforeseen energy saving potential thanks to some intrinsic features specifically related to this kind of machines. The paper presents a further reduction strategy to lower energy consumptions in compressed air systems using SVRCs that relies on the combination of the recent use of a pressure swirled oil injection technology and a dual stage intercooling. The synergy between technologies already mature approaches to the lowest energy consumption and candidates SVRCs as superior machines in the energy context. The saving potential compared to the technology at the state of the art was evaluated thanks to a comprehensive mathematical modeling of the two compressor sections and the intercooling heat exchanger and fan. Results showed a reduction of the electrical power required to drive the compressor system up to 9.5%. The overall approach represents a model-based design for a new machine which is under development.

Experimental investigation on materials and lubricants for sliding-vane air compressors

Positive-displacement compressors and, among them, sliding-vane rotary machines are widely used in the compressed air sector. As in many other industrial fields, the efficient utilization of energy has become a major goal also in this sector. The aim of the present activity is the experimental investigation on the influence of two vanes materials (cast iron and aluminium with anodized surface) and of four commercial lubricants (characterized by different formulations and additives concentrations) on the performance of a mid-capacity sliding-vane rotary compressor in a number of operating pressures. The performance is identified by both the volume flow rate and the absorbed mechanical power, evaluated according to the international standard ISO 5167 and ISO 1217. The campaign indicates that the considered lubricants do not affect appreciably the volumetric flow rate. On the other hand, the specific lubricants determine a variation of about 1% of the mechanical power for both materials, while the specific material a variation between 0.9% and 2.6%. The best performance is achieved by aluminium vanes and a synthetic poly-α-olefin lubricant.

Friction power modeling and measurements in sliding vane rotary compressors

In compressed air systems, mechanical and organic losses account for 15% of compressor energy consumption. In the current research, the energy saving potential achievable through friction power reduction in sliding vane rotary compressors was investigated using experimental and modeling approaches. Tests on a new mid-size industrial compressor operating at different steady conditions (outlet pressure 9, 12.5, 14.5 bar at 1000 and 1500 RPM) assessed the machine performance through measurement of mechanical power and the reconstruction of the pressure-volume diagram. An experimental methodology was also developed to quantify the power lost by friction and its measurement uncertainty using the concept of indicated mean effective pressure. Modeling the compressor blade dynamics allowed a friction power decomposition while an analysis of the hydrodynamic lubrication at the most severe friction location, namely between blade tip and stator wall, additionally provided the oil film thickness evolution along the contact surface. The agreement between modeling and experimental data identified a value for the friction coefficient of 0.065. Design suggestions on existing machines and new design solutions were eventually outlined varying blade mass, revolution speed and compressor aspect ratio. These improved configurations predicted an efficiency increase up to 6%.

Theoretical modeling and experimental investigations for the improvement of the mechanical efficiency in sliding vane rotary compressors

Positive displacement compressors lead the market of compressed air production for industrial applications. Among them, sliding vane rotary compressors represent an energetically virtuous alternative to the current compression technologies. In the present work, the effects of compressor design parameters were investigated through a comprehensive approach that aimed at addressing more efficient machines to promote sliding vane compressors as the key enabling technology in compressed air systems. A comprehensive mathematical model was developed to study the main phenomena occurring in this kind of compressors. The model provides the cell volume evolution over a whole rotation during which filling, compression and discharge processes occur. The first and latter phases are described by the quasi-propagatory approach that represents the inertial, capacitive and resistive features of one-dimensional unsteady flows. The dynamics of the compressor blades led to four different arrangements inside the rotor slots while an analysis of the hydrodynamic lubrication established between blade tip and stator wall focused on the oil film thickness evolution to prevent dry contacts. An extensive experimental campaign on a mid-size industrial compressor allowed the model validation at different outlet pressure levels and revolution speeds using a direct measurement of mechanical power and the reconstruction of the indicator diagram from piezoelectric pressure transducers. The friction coefficient at the contact points between blades with stator and rotor was estimated in 0.065 and further improvements of the mechanical efficiency were eventually addressed considering the roles of compressor aspect ratio, revolution speed, and blade tilt. The first two theoretical optimizations might lead to an increase of the compressor efficiency of 2 and 9 percentage points respectively. On the other hand, acting on the blade tilt would not produce relevant improvements.

Development of an internal air cooling sprayed oil injection technique for the energy saving in sliding vane rotary compressors through theoretical and experimental methodologies

The present work highlights the energy saving potential of the lubricant fluid supplied in Sliding Vane Rotary air Compressors. A Lagrangian theoretical model of a sprayed oil injection technology assessed the cooling effect of the lubricant due to the high surface to volume ratio of the oil droplets and predicted a reduction of the indicated power. The model validation was carried out through a test campaign on a mid-size sliding vane compressor equipped with a series of pressure swirl atomizers. The oil injections took place along the axial length of the compressor. The reconstruction of the indicator diagram and the direct measurement of the mechanical power revealed a reduction of the energy consumption close to 7% using an injection pressure of 20 bar. A parametric analysis on the injection pressure and temperature and on the cone spray angle was eventually carried out to identify an optimal set of operative injection parameters.

Energy saving in sliding vane rotary compressors using pressure swirl oil atomizers

In industrial contexts, electrical energy for compressed air represents an important share of the global electricity consumption: this figure accounts for 4–5% of the total. Among the existing compressor technologies, rotary volumetric machines proved to be more suitable than other types (dynamic, reciprocating, etc.) in terms of pressure and flow rate delivered. Even though not as widespread as screw machines, but thanks to the technological improvements made in the last two decades, sliding vane rotary compressors are characterized by premium specific energy consumptions and demonstrate an unforeseen potential in terms of energy saving due to some intrinsic features specifically related to these machines. The current research focuses on an innovative oil injection technology that is not only able to fulfill the sealing and lubrication requirements but also to cool the air during the compression phase. A comparison between the mathematical model of the new oil injection technology and the experimental p-V diagrams measured through a set of piezoelectric transducers is shown. The compression work reduction, predicted in the model and further measured at the shaft and observed in the indicator diagrams, gives a strong consistency to the injection technology.

Sliding vane rotary compressor technology and energy saving

Energy saving, CO2 reduction, and energy generation from renewable sources represent the three cornerstones of the energetic and environmental commitments of all the countries in the world. These three elements may give a quantitative contribution to the sustainability in an industrial environment. Among them, the most important one, that represents a driver in many sectors, is the limitation of the CO2 concentration in the atmosphere: most recent data (2013) from National Oceanic and Atmospheric Administration – Earth System Research Laboratory (NOAA-ERSL) set at 395.55 parts per million (ppm) the CO2 in the atmosphere and the continuous increasing trend will quickly allow to reach the 450 ppm level which is considered as a safeguard limit to avoid irreversible environmental and socioeconomics problems. Looking at the energy consumption side, energy saving is a key factor. Compressed air production does not escape this requirement and, for the compressor manufacturing industry, this can represent an opportunity with great potential benefits. Compressed air is produced by electrical energy and the consumption accounts as much as 10% of industrial consumption of electricity. A lower estimate places at 6% this share but an additional 12% is estimated to be associated with the commercial and residential markets (portable tools, air pumps, pneumatic heating, ventilation, air conditioning, etc.). Hence, the overall compressor needs are estimated equal to 20% of the industrial electricity needs. Considering that industrial consumption of electricity represents a given share of the overall electrical energy consumption (it depends on the geographical context, social development, industrial level, etc.), with good approximation, compressed air can be associated to the overall electricity consumption and to primary energy consumption too. So, it can be compared with the other energy alternatives when the data are reliable and referred to real situations, actions to promote energy efficiency in compressed air systems can be identified with their real importance and compared with all the other measures. From many independent studies the most important energy saving measures are associated to the: (1) reduction of leakages on the distribution lines, (2) a more appropriate compressed air system design, (3) use of adjustable speed drives, (4) waste heat recovery. All these aspects, in a 10-year period of operation, weigh 70–75% of the overall compressed air costs. Therefore, the compressor technology is a key factor to reduce energy consumption including in it load control, variable speed operation, compressor sizing, etc. A great potential saving is associated to leaks, friction pipes, etc. but these actions are downstream of the compressed air production. After having discussed some issues concerning the future overall energy consumption and CO2 emissions, considering the development of the electricity market in the world in the near future, and overall energy characteristics of existing machines widely used in the compressed air market, the article goes deep inside a specific compressor technology which is represented by the sliding vanes rotary type. Principal processes inside these machines are discussed in the light of the recent scientific literature advancement of a theoretical and experimental nature. The general idea was that these machines are not so well known and their use is not so widespread: thanks to a deeper scientific interest over the past few years, these compressors had a notable performance improvement, thus a greater potential in industrial applications. Thanks to some intrinsic aspects, some energy issues are presented and related to specific processes inside the machine and compared with other compressors. The potential further improvements in terms of specific energy are discussed and addressed in main future research directions.

Mechanical Efficiency Optimization of a Sliding Vane Rotary Compressor

This study presents the mechanical efficiency optimization of a sliding vane rotary compressor by using genetic algorithms. Relevant air properties, volume segments, vane loadings and stresses, friction forces, compression power, and power loss are calculated to determine the mechanical efficiency of a compressor. Design variables include the major axis length and minor axis length of the elliptical stator inner contour, thickness, depth and width of vanes, mechanical efficiency, rotor rotational speed, polytropic exponent, and angular locations of the inlet and outlet ports. The effects of the mutation rate, crossover rate, and population size of the genetic algorithms on these design variables are studied. The vane is thin and the variation effects of vane dimensions on the mechanical efficiency of the compressor are less significant than other design variables. Therefore, the dimensions of vanes can be eliminated as design variables. The mechanical efficiency of the compressor is 0.55. The optimum values of these design variables are recommended for further development of the compressor.

Impact Forces of Sliding Vanes on Rotor Slots in a Rotary Compressor

This study analyzes the impacts of vanes on rotor slots by simulating the impacts of two plates in a sliding vane rotary compressor. The Hertzian contact rule and the first order shear deformation plate theory incorporating the shear deformation and the rotary inertia are used to generate a mathematical model. Impact forces are calculated at various times and positions of the vane. Data generated from the model highly correlated with results obtained from ABAQUS software.

A measurement method for air pressures in compressor vane segments

This study presents a more accurate measurement method for measuring air pressures in the vane segments when a sliding-vane rotary compressor performs suction and compression phases in either stable or unstable rotational speeds. The air pressures in the vane segments when the compressor performs suction and compression phases can evaluate the intake effect of the inlet and seal effect of the vane segment of the compressor, respectively. Two strain gauge type pressure transducers were utilized with an encoder to measure air pressures in the vane segments. The measured air pressure in the vane segment when the compressor performed suction phase increased when the rotational speed increased up to 800 rpm. It decreased when the rotational speed was faster than 800 rpm. When the rotational speed was 1400 rpm, the air pressure in the vane segment reduced to 99.5 kPa compared with the ambient air pressure of 100.3 kPa. Therefore, the dimension or shape of the compressor inlet should be modified to provide the suction air pressure to be closed to the ambient air pressure. When the compressor performed compression phase at the rotational speed of 1400 rpm, the measured air pressure in the vane segment was 153 kPa compared with the designed air pressure of 244 kPa. Therefore, the manufacture precision of the compressor should be improved to reduce the air leakage.

Optimal Tolerance Allocation for a Sliding Vane Compressor

An optimization model has been built with consideration of the required reliability, the minimum machining cost, and quality loss. The normal and the lognormal distributions of tolerances that depend on the production types of components are used in the reliability model. Cost tolerance data obtained from Bjørke are used to calculate the machining cost. The asymmetric quadratic quality loss model is used to calculate quality loss caused by the deviation and the mean-shift of distributions. Tolerance allocation of a sliding vane rotary compressor is optimized for the required reliability, the minimum cost and quality loss, and optimum tolerances of components are recommended. The results show that high accuracies of the slot length, the vane thickness, and the slot width are required. Hence, their tolerances are smaller than other components. The effects of the correlation coefficient of the bottom cover plate and the top cover plate and the correlation coefficient of the front cover plate and the rear cover plate to total cost are insignificant. Further, the cost of quality loss is reduced when the weighting ratio of the quality loss function weighting coefficient to the machining cost function weighting coefficient is increased. The total cost is increased because tight tolerance allocation increases the machining cost.

A Recirculation Compressor for Hot Gases

A conventional sliding-vane rotary compressor was modified for use in recirculating hot gases at design temperatures up to 425°C. The compressor has performed well at 350°C with gaseous streams of H2S, SO2, COS, CO2, N2, H2O, and Sx. Completely free of lubricants, only stainless steel and graphite surfaces are exposed to hot gases. The unit may be mounted within a heating medium for isothermal operation.

Paper 17: Pressure–Volume Diagrams for Sliding Vane Rotary Compressors

Pressure–volume diagrams, usually associated with reciprocating machines, are valuable both as a means of investigating performance and in providing information for further design work. This paper describes the main features of a method for compiling rotor cell pressure–volume diagrams for sliding vane rotary compressors. Diagrams obtained for various compressor operating conditions are given and discussed.

4.可動翼形回転圧縮機 : 最近の空気機械の動向

4.可動翼形回転圧縮機 : 最近の空気機械の動向