- Lu, Kui, Sultan, Ibrahim, Phung, Truong
- Authors: Lu, Kui , Sultan, Ibrahim , Phung, Truong
- Date: 2023
- Type: Text , Journal article
- Relation: International Journal of Refrigeration Vol. 145, no. (2023), p. 467-480
- Full Text: false
- Reviewed:
- Description: As an emerging technology, the limaçon rotary compressor possesses great potential for fluid-processing applications. However, the technology and associated cost required to fabricate the limaçon machine could sometimes be beyond the capability of some manufacturers. To reduce the production cost, circolimaçon embodiment whose rotor and housing are constructed of circular arcs has been proposed. This paper is intended to investigate the viability of the circolimaçon embodiment of limaçon technology based on sealing performance. A nonlinear three-degree of freedom model is presented to describe the dynamic behaviour of the apex seal during the machine operation. Additionally, the leakage through the seal-housing gap is formulated by considering the inertia and viscous effects on the flow. A numerical illustration is offered to compare the performance of the circolimaçon embodiment with that of the limaçon-to-limaçon (L2L) type machine at different pressure ratios and operating speeds. The effect of limaçon aspect ratio on the apex seal dynamics is also investigated. Based on the results, it is found that the circolimaçon embodiment exhibits comparable performance to the L2L-type machine, despite having more significant seal vibrations. The differences in the volumetric and isentropic efficiencies between the two machines are found within 8% and 3%, respectively. Additionally, it is also discovered that the circolimaçon compressor with a small capacity undergoes lower level of seal dynamics, suggesting a better machine reliability. © 2022
Design and optimisation of the limaçon rotary compressor
- Lu, Kui
- Authors: Lu, Kui
- Date: 2022
- Type: Text , Thesis , PhD
- Full Text:
- Description: The limaçon positive displacement machine is characterised by its internal geometry and unique mechanical motion; both based on a mathematical curve known as the limaçon of Pascal. The limaçon technology offers many advantages, such as compact size and double‐acting functionality, and its great potential for fluid processing applications has been proven by a number of patents and innovative designs in engines, expanders, and pumps. However, no commercial application of the limaçon technology in the field of positive displacement compressors has been reported in the literature. This could be attributed to the fact that the potential of the limaçon technology for gas compression has not been established as yet. The process of establishing potential is necessary before funds and resources are dedicated to investing in prototyping and testing. This process entails a considerable amount of modelling, coding and analysis as one must ensure the embodiment is geometrically capable of delivering suction and compression strokes, ports can be arranged to support the workings of these strokes, a number of measurable parameters can be identified as impacting compressor performance and it is possible to calculate a set of parameters which optimise this performance. To achieve this objective, a comprehensive mathematical model of a limaçon machine, implemented as a compressor,was first developed. The model, which is multi‐physical in nature, spans such domains as kinematics, fluid dynamics, characteristics of the port flow, internal leakage due to seal vibration, dynamics of the discharge valve, and thermodynamics. Subsequently, the simulation of the model has been performed to numerically study the operational characteristics of the limaçon compressor and to investigate the effect of various parameters on the compressor performance. It was found that the increase in the operating speed and pressure ratio would lead to negative effects on machine performance, especially on volumetric efficiency. Additionally, the results of simulations indicated that the level of fluid over‐compression is influenced by the characteristics of the discharge valve. To ensure the suitability of limaçon technology for use in positive displacement compressors, a study was undertaken to determine whether such an embodiment lent itself to optimisation efforts. For this purpose, the thorough mathematical model which has been developed to simulate compressor workings was then used for optimisation purposes whereby a Bayesian optimisation procedure was applied. The optimisation procedure was conducted in a two‐stage fashion where the first stage optimises the machine dimensions to meet volumetric requirements specified by the designer; and the second stage focuses on revealing the optimum combination of port geometries that improves machine performance. A numerical illustration was presented to prove the validity of the presented approach, and the results show that considerable improvements in the isentropic and volumetric efficiencies can be attained. Moreover, the optimised design was tested under different operating speeds and pressure ratios to investigate its robustness. It was found that the optimised design can exhibit relatively stable performance when the working conditions vary within a small bandwidth around that used in the optimisation procedure. The limaçon technology has three embodiments, namely the limaçon‐to‐limaçon (L2L), the limaçon‐to‐circular, and the circolimaçon. The circolimaçon embodiment features using circular arcs, rather than limaçon curves, to develop profiles for the rotor and housing. This embodiment simplifies the manufacturing process and reduces the production cost associated with producing a limaçon technology. A feasibility study of the circolimaçon embodiment was conducted by comparing its performance with that of the L2L type device. The machine dimensions and port geometries obtained from the optimisation procedure were used in the comparative study. A nonlinear three‐degree of freedom model was presented to describe the dynamic behaviour of the apex seal during the machine operation. Additionally, the leakage through the seal‐housing gap was formulated by considering the inertia and viscous effects of the flow. The results from the case study suggest that the circolimaçon embodiment exhibits comparable performance to the L2L‐type machine, despite having more significant seal vibrations. Moreover, it was also discovered that the circolimaçon compressor with a small capacity undergoes a lower level of seal dynamics, indicating better machine reliability.
- Description: Doctor of Philosophy
- Authors: Lu, Kui
- Date: 2022
- Type: Text , Thesis , PhD
- Full Text:
- Description: The limaçon positive displacement machine is characterised by its internal geometry and unique mechanical motion; both based on a mathematical curve known as the limaçon of Pascal. The limaçon technology offers many advantages, such as compact size and double‐acting functionality, and its great potential for fluid processing applications has been proven by a number of patents and innovative designs in engines, expanders, and pumps. However, no commercial application of the limaçon technology in the field of positive displacement compressors has been reported in the literature. This could be attributed to the fact that the potential of the limaçon technology for gas compression has not been established as yet. The process of establishing potential is necessary before funds and resources are dedicated to investing in prototyping and testing. This process entails a considerable amount of modelling, coding and analysis as one must ensure the embodiment is geometrically capable of delivering suction and compression strokes, ports can be arranged to support the workings of these strokes, a number of measurable parameters can be identified as impacting compressor performance and it is possible to calculate a set of parameters which optimise this performance. To achieve this objective, a comprehensive mathematical model of a limaçon machine, implemented as a compressor,was first developed. The model, which is multi‐physical in nature, spans such domains as kinematics, fluid dynamics, characteristics of the port flow, internal leakage due to seal vibration, dynamics of the discharge valve, and thermodynamics. Subsequently, the simulation of the model has been performed to numerically study the operational characteristics of the limaçon compressor and to investigate the effect of various parameters on the compressor performance. It was found that the increase in the operating speed and pressure ratio would lead to negative effects on machine performance, especially on volumetric efficiency. Additionally, the results of simulations indicated that the level of fluid over‐compression is influenced by the characteristics of the discharge valve. To ensure the suitability of limaçon technology for use in positive displacement compressors, a study was undertaken to determine whether such an embodiment lent itself to optimisation efforts. For this purpose, the thorough mathematical model which has been developed to simulate compressor workings was then used for optimisation purposes whereby a Bayesian optimisation procedure was applied. The optimisation procedure was conducted in a two‐stage fashion where the first stage optimises the machine dimensions to meet volumetric requirements specified by the designer; and the second stage focuses on revealing the optimum combination of port geometries that improves machine performance. A numerical illustration was presented to prove the validity of the presented approach, and the results show that considerable improvements in the isentropic and volumetric efficiencies can be attained. Moreover, the optimised design was tested under different operating speeds and pressure ratios to investigate its robustness. It was found that the optimised design can exhibit relatively stable performance when the working conditions vary within a small bandwidth around that used in the optimisation procedure. The limaçon technology has three embodiments, namely the limaçon‐to‐limaçon (L2L), the limaçon‐to‐circular, and the circolimaçon. The circolimaçon embodiment features using circular arcs, rather than limaçon curves, to develop profiles for the rotor and housing. This embodiment simplifies the manufacturing process and reduces the production cost associated with producing a limaçon technology. A feasibility study of the circolimaçon embodiment was conducted by comparing its performance with that of the L2L type device. The machine dimensions and port geometries obtained from the optimisation procedure were used in the comparative study. A nonlinear three‐degree of freedom model was presented to describe the dynamic behaviour of the apex seal during the machine operation. Additionally, the leakage through the seal‐housing gap was formulated by considering the inertia and viscous effects of the flow. The results from the case study suggest that the circolimaçon embodiment exhibits comparable performance to the L2L‐type machine, despite having more significant seal vibrations. Moreover, it was also discovered that the circolimaçon compressor with a small capacity undergoes a lower level of seal dynamics, indicating better machine reliability.
- Description: Doctor of Philosophy
Mathematical modeling and parametric study of the limaçon rotary compressor
- Lu, Kui, Sultan, Ibrahim, Phung, Truong
- Authors: Lu, Kui , Sultan, Ibrahim , Phung, Truong
- Date: 2022
- Type: Text , Journal article
- Relation: International Journal of Refrigeration Vol. 134, no. (2022), p. 219-231
- Full Text:
- Reviewed:
- Description: In this paper, a class of rotary positive displacement compressors which is known as the limaçon compressor is introduced. The main feature of such a compressor is that profiles of its housing and rotor and the motion of its rotor are developed from a mathematical curve called the limaçon of Pascal. A mathematical model of the limaçon compressor, which incorporates the mass flow of the working fluid, the leakage loss, the dynamic response of the discharge valve, as well as the thermodynamic behaviors, is formulated, and the simulation of such a model has been performed to study the operational characteristics of the limaçon compressor. A parametric analysis is also conducted to investigate the effects of various parameters on the compressor performance. Based on the results, it is found that the machine performance deteriorates as the operating speed increases despite an initial rise in the volumetric efficiency. Additionally, the isentropic efficiency appears insensitive to the change of the pressure ratio, whereas a negative effect on the volumetric efficiency is noticed when the pressure ratio is increased. The effect of the valve diameter on the over-compression loss has also been studied, and the result indicates that a smaller valve diameter leads to a higher level of fluid over-compression. © 2021 Elsevier Ltd and IIR
- Authors: Lu, Kui , Sultan, Ibrahim , Phung, Truong
- Date: 2022
- Type: Text , Journal article
- Relation: International Journal of Refrigeration Vol. 134, no. (2022), p. 219-231
- Full Text:
- Reviewed:
- Description: In this paper, a class of rotary positive displacement compressors which is known as the limaçon compressor is introduced. The main feature of such a compressor is that profiles of its housing and rotor and the motion of its rotor are developed from a mathematical curve called the limaçon of Pascal. A mathematical model of the limaçon compressor, which incorporates the mass flow of the working fluid, the leakage loss, the dynamic response of the discharge valve, as well as the thermodynamic behaviors, is formulated, and the simulation of such a model has been performed to study the operational characteristics of the limaçon compressor. A parametric analysis is also conducted to investigate the effects of various parameters on the compressor performance. Based on the results, it is found that the machine performance deteriorates as the operating speed increases despite an initial rise in the volumetric efficiency. Additionally, the isentropic efficiency appears insensitive to the change of the pressure ratio, whereas a negative effect on the volumetric efficiency is noticed when the pressure ratio is increased. The effect of the valve diameter on the over-compression loss has also been studied, and the result indicates that a smaller valve diameter leads to a higher level of fluid over-compression. © 2021 Elsevier Ltd and IIR
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