Optimum positioning of ports in the limaon gas expanders
- Authors: Sultan, Ibrahim , Schaller, Carl
- Date: 2011
- Type: Text , Journal article
- Relation: Journal of Engineering for Gas Turbines and Power Vol. 133, no. 10 (2011), p.
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- Description: Positive displacement expanders are quickly gaining popularity in the fields of micropower generation and refrigeration engineering. Unlike turbomachines, expanders can handle two-phase flow applications at low speed and flow rate levels. This paper is concerned with a simple-design positive displacement expander based on the lima̧on of Pascal. The paper offers an insight into the thermodynamic workings of the limaison gas expander and presents a mathematical model to describe the manner in which the port locations affect the expander performance. A stochastic optimization technique is adopted to find the locations, for the expander ports, which produce best expander performance for given chamber dimensions. The operating speed and other parameters will be held constant during the optimization procedure. A case study is offered in this paper to prove the validity of the presented approach, and comments are given on how various operating parameters affect system performance in the limaison design. © 2011 American Society of Mechanical Engineers.
On the kinematics and synthesis of a geared five-bar slider-crank mechanism
- Authors: Sultan, Ibrahim , Kalim, Azfar
- Date: 2011
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science Vol. 225, no. 5 (2011), p. 1253-1261
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- Description: The geared five-bar mechanism possesses kinematic abilities that qualify its utility in various industrial applications. Small changes to the mechanism topology or dimensions create new designs with different motion characteristics. This article presents design-orientated kinematical insights and mathematical treatments for the embodiment of the mechanism in which the end gear is eccentrically pivoted to a sliding element. For its synthesis, a kinematic classification is introduced and approximate curves are used to guide the motion of the slider. A gradient-based Levenberg-Marquardt formulation is employed for the optimization procedure. Geometric, mobility, and dimensional constraints are utilized together with numerical position equations for the analysis. Two case studies are presented at the end of this article to highlight the versatility of the mechanism and prove the validity of the presented mathematical model.
Evaluation of slug flow-induced flexural loading in pipelines using a surrogate model
- Authors: Sultan, Ibrahim , Reda, Ahmed , Forbes, Gareth
- Date: 2013
- Type: Text , Journal article
- Relation: Journal of Offshore Mechanics and Arctic Engineering Vol. 135, no. 3 (2013), p. 8
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- Description: Slug flow induces vibration in pipelines, which may, in some cases, result in fatigue failure. This can result from dynamic stresses, induced by the deflection and bending moment in the pipe span, growing to levels above the endurance limits of the pipeline material. As such, it is of paramount importance to understand and quantify the size of the pipeline response to slug flow under given speed and damping conditions. This paper utilizes the results of an optimization procedure to devise a surrogate closed-form model, which can be employed to calculate the maximum values of the pipeline loadings at given values of speed and damping parameters. The surrogate model is intended to replace the computationally costly numerical procedure needed for the analysis. The maximum values of the lateral deflection and bending moment, along with their locations, have been calculated using the optimization method of stochastic perturbation and successive approximations ( SPSA). The accuracy of the proposed surrogate model will be validated numerically, and the model will be subsequently used in a numerical example to demonstrate its applicability in industrial situations. An accompanying spreadsheet with this worked example is also given.
- Description: C1
Characterization of limacon gas expanders with consideration to the dynamics of apex seals and inlet control valve
- Authors: Phung, Truong , Sultan, Ibrahim
- Date: 2018
- Type: Text , Journal article
- Relation: Journal of Engineering for Gas Turbines and Power Vol. 140, no. 12 (2018), p. 1-11
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- Description: Limacon machine, of which the relative motion between the rotor and housing follows the limacon curve, belongs to a class of rotary positive displacement machines. The profiles of rotors and housings of those machines can be constructed of either limacon or circular curves, hence the names: limacon-to-limacon, circolimacon, and limacon-to-circular machines. This paper presents the investigation into the thermodynamic performance of the limacon-to-circular machines with the presence of apex seals and inlet valve. This paper sets out by briefly introducing the limacon technology and the construction of the limacon-to-circular machine working volume. The mathematical descriptions of ports positions and areas have also been introduced. The paper then discusses the flow and phase composition of working fluid through the working chambers as well as how the fluid velocity is modeled and calculated. Then the seal dynamic model and response of inlet valve are presented followed by the machine thermodynamic model. A case study has also been presented to show the responses of seals and inlet valve during the machine operation.
On the design of a class of rotary compressors using bayesian optimization
- 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.