Showing items 1 - 5 of 5

A study on the use of machine learning methods to improve reciprocating compressor reliability via torque tailoring

- Lu, Kui, Sultan, Ibrahim, Phung, Truong

  • Authors: Lu, Kui , Sultan, Ibrahim , Phung, Truong
  • Date: 2021
  • Type: Text , Conference paper
  • Relation: 2021 International Conference on Maintenance and Intelligent Asset Management, ICMIAM 2021, Ballarat, Australia, 12-15 December 2021, 2021 International Conference on Maintenance and Intelligent Asset Management, ICMIAM 2021
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  • Description: Reciprocating compressors have found popularity in applications where compressed air is required at high pressure levels with moderate flow rates. The mechanical drives used for these compressors are based on the traditional slider-crank linkage which, despite its simplicity, does not lend itself to optimization effort aimed at improving the compressor reliability and performance. The work presented in this paper adopts the notion that the mechanical reliability of the compressor drive is limited by the level and cyclical variability of the loads transmitted through its members and the effectiveness of its cooling system. In the paper, machine learning methods will be employed to craft an objective function suitable to use in a Bayesian optimization effort undertaken to produce a more reliable compressor drive. A numerical example is presented to prove the validity of the presented method and its suitability for use in real life compressor designs. © 2021 IEEE.

Design and optimisation of the limaçon rotary compressor

- Lu, Kui

  • Authors: Lu, Kui
  • Date: 2022
  • Type: Text , Thesis , PhD
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  • 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

On the design of a class of rotary compressors using bayesian optimization

- Lu, Kui, Phung, Truong, Sultan, Ibrahim

  • Authors: Lu, Kui , Phung, Truong , Sultan, Ibrahim
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Machines Vol. 9, no. 10 (2021), p.
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  • Description: The optimization process of compressors is usually regarded as a ‘black-box’ problem, in which the mathematical form underlying the relationship between design parameters and the design objective is impractical and costly to be obtained. To solve the ‘black-box’ problem, Bayesian optimization has been proven as an accurate and efficient method. However, the application of such a method in the design of compressors is rarely discussed, particularly no work has been reported in terms of the positive displacement type compressor. Therefore, this paper aims to introduce the Bayesian optimization to the design of positive displacement compressors through the optimization process of the novel limaçon compressor. In this paper, a two-stage optimization process is presented, in which the first stage optimizes the geometric parameters as per design requirements and the second stage focuses on revealing an optimum setting of port geometries that improves machine performance. A numerical illustration is offered to prove the validity of the presented approach. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

The orbital displacer : Implications and applications

- Spark, Ian, Lu, Kui

  • Authors: Spark, Ian , Lu, Kui
  • Date: 2019
  • Type: Text , Book chapter
  • Relation: Positive displacement machines : Modern design innovations and tools Chapter 1 p. 3-35
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  • Description: In 1972 the orbital engine invented by Sarich (1970, 1973) was widely publicized in Australia. As a result of this publicity two mechanical engineering students at the Gippsland Institute of Advanced Education decided to make the orbital engine the subject matter of their final year project in 1973. Since publicity indicated that Sarich was concentrating his efforts on the development of a four-stroke orbital engine, the students (Joe Rosin and Robert Sincich) and the first author decided to concentrate their efforts on the design of an orbital two-stroke engine.

The orbital displacer: Implications and applications

- Spark, Ian, Lu, Kui

  • Authors: Spark, Ian , Lu, Kui
  • Date: 2019
  • Type: Text , Book chapter
  • Relation: Positive Displacement Machines: Modern Design Innovations and Tools p. 3-35
  • Full Text: false
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  • Description: The significance of the orbital displacer may well extend well beyond its application as the basis of a four-stroke internal combustion engine. For example, its inherently high swept volume to total volume ratio can be further increased by combining the original orbital displacer with an everted (i.e. inside-out) orbital displacer to form a hybrid orbital displacer with an even higher swept volume to total volume ratio. Furthermore, the orbital motion of the piston can be used to open and close ports to produce any desired port timing with the same frequency as the orbiting of the piston. These together with other pertinent features will be considered under the following headings: 1. Introduction, 2. Swept volume to total volume ratio, 3. Working volume as a function of crank angle, 4. Minimum geometrically necessary clearance volume as a function of displacer geometry, 5. Valveless port timing, 6. Support of the orbiting piston and vanes, 7. Balancing of the orbital piston and vanes, 8. Sealing of the working volume, 9. Frictional losses and lubrication, 10. Combustion in orbital displacers, 11. Cooling of orbital engines, 12. Manufacturing processes and materials. The above pertinent features will be discussed with reference to the following applications of the orbital displacer: orbital two-stroke engine, orbital hydraulic pumps and motors, orbital pneumatic compressors and motors, orbital Rankine (steam) engine, and orbital 6 cc model aircraft engine. Engineering students have found orbital displacer projects stimulating in the originality required, as they invariably had to go back to first principles to solve problems. © 2020 Elsevier Inc. All rights reserved.
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