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.
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.
Description:
The limaçon positive displacement technology has been featured in a number of patents over the last 100 years. The technology offers a two-lobe rotor that slides and rotates in a rounded cavity so as to create a pair of variable-volume chambers suited for fluid processing. As such, it can be employed to manufacture gas expanders to extract work from low-grade heat or other heat resources. Positive displacement gas expanders are applied to small-scale power generation plants which can be used for a number of applications such as to improve the energy efficiency of existing thermal processes. This thesis features work undertaken to develop models to inform and enhance the design process such that an optimised limaçon machine is produced. The models developed in the thesis efficiently predict and characterise the performance of the limaçon gas expander irrespective of the working fluid used or the phase transformation that takes place during the working of the expander. The models developed are multiphysics in nature as they incorporate the vibration analysis of the apex seals with the thermodynamical differential description of the working medium together with the dynamical characterisation of an electro-mechanical control valve fitted to regulate the amount of fluid allowed into the working chamber. Chapter 1 starts with a problem statement that addresses the questions which the author aims to answer upon the completion of this project. The chapter offers a detailed background on the limaçon technology and where it falls in relation to other fluid processing machines. Chapter 1 is also a literature review which spans such aspects as:
Description:
The limaçon positive displacement technology has been featured in a number of patents over the last 100 years. The technology offers a two-lobe rotor that slides and rotates in a rounded cavity so as to create a pair of variable-volume chambers suited for fluid processing. As such, it can be employed to manufacture gas expanders to extract work from low-grade heat or other heat resources. Positive displacement gas expanders are applied to small-scale power generation plants which can be used for a number of applications such as to improve the energy efficiency of existing thermal processes. This thesis features work undertaken to develop models to inform and enhance the design process such that an optimised limaçon machine is produced. The models developed in the thesis efficiently predict and characterise the performance of the limaçon gas expander irrespective of the working fluid used or the phase transformation that takes place during the working of the expander. The models developed are multiphysics in nature as they incorporate the vibration analysis of the apex seals with the thermodynamical differential description of the working medium together with the dynamical characterisation of an electro-mechanical control valve fitted to regulate the amount of fluid allowed into the working chamber. Chapter 1 starts with a problem statement that addresses the questions which the author aims to answer upon the completion of this project. The chapter offers a detailed background on the limaçon technology and where it falls in relation to other fluid processing machines. Chapter 1 is also a literature review which spans such aspects as:
Description:
Positive displacement machines have acquired particular popularity with the current push for sustainable energy production and consumption. It is currently not acceptable to waste energy available in high-pressure gasses throttled or vented to atmosphere in industrial processes (Samuel, 2007; Shu, Yu, Tian, Wei, & Liang, 2014) or blown out of cylinders in large diesel engines (Amann, 1987; Panesar, 2015; Karvountzis-Kontakiotis, Pesiridis, Zhao, Alshammari, et al., 2017). For such applications, a suitably sized positive displacement machine would be employed to harvest energy from these gases and transform it into useful forms. Turbines that are traditionally employed in massive power plants cannot be used for energy harvesting applications due to their inability to handle neither two-phase vapors (Groniewsky, Gy€orke, & Imre, 2017) nor flow occurring at small rates. For these applications, a gas expander, which is a positive displacement machine is usually employed. In relation to pressure creation, positive displacement pumps and compressors are commonly employed to impart pressure to respectively gaseous and liquid fluids flowing at rates which are required by most industries. This chapter presents the limac¸on rotary positive displacement machine, which can be employed for energy production (i.e., as a gas expander) and energy consumption (i.e., as a compressor or a pump) with equal ease and effectiveness. The limac¸on machine (Sultan, 2005) offers a straightforward technology, which has occurred to many creative minds as evident by patents which can be traced back to the 19th century. However, it is unfortunate that such technology did not make it to mass production due to the lack of mathematical understanding of their geometric characteristics and unavailability of manufacturing tools required to machine their chambers. Recently, however, with technical papers published on the topic, industry take-up of the technology has started to emerge. A good example of this take up is shown by the patent of Nystrom (2016).
Description:
Sustainable practices within the mining and energy sectors are assuming greater significance due to uncertainty and change within the global economy and safety, security, and health concerns. This book examines sustainability issues facing the mining and energy sectors by addressing six major themes: Mining and Mineral Processing; Metallurgy and Recycling; Environment; Energy; Socioeconomic and Regulatory; and Sustainable Materials and Fleets. Emphasizing an integrated transdisciplinary approach, it deliberates on optimizing mining productivity and energy efficiency and discusses integrated waste management practices. It discusses risk management, cost cutting, and integration of sustainable practices for long-term business value. It gives a comprehensive outlook for sustainable mineral futures from academic and industry perspectives covering mine to mill optimization, waste, risk and water management, improved efficiencies in mining tools and equipment, and performance indicators for sustainable developments. It covers how innovation and research underpin management of natural resources including sustainable carbon management.
Description:
This chapter is intended to show that it is possible to obtain a considerable improvement in compressor performance and reliability by modifying the design of the compressor drive. Instead of the traditional slider-crank mechanism, which has been used as a drive since the compressor industry started, it is now possible to replace this drive by more sophisticated ones which offer more flexible stroke design. Such replacement has been made possible by the modern manufacturing methods and analysis tools which are currently at the disposal of industry and research bodies. Earlier work in the domain of proposing new linkages to drive positive displacement machines can be found in the work by Ooi and Wan (2000) who presented a proposal to drive the compressor piston directly from the back using a camlike mechanism. Also, Mimmi and Pennacchi (2001) proposed a pump drive that produces four variable-length strokes per crank revolution. On the other hand, Sultan and Kalim (2011) presented a five-bar geared linkage which can be used to drive a reciprocating compressor instead of the conventional slider-crank mechanism. The next section will present a mathematical model for the compressor operation.
Description:
Rotary machines, and limaçon machines in particular, offer a better power to weight ratio compared to reciprocating machines; however, leakage due to improper apex and side sealing have prevented rotary machines from thriving. In this paper, a modelling approach is presented to analyse the vibration of apex seal during the machine operation and the power loss caused by the seal friction. The seal and spring are modelled as a spring-mass system in which the seal deformation is negligible. The seal-groove relative positions have then been categorised into nine different possible cases based on the number of contact points between the seal and the seal groove. A case study has been presented to demonstrate the reliability of the model.
Description:
Positive Displacement Machines are based on the concept of changing the volume available for fluid processing in a manner which produces matching variations in the pressure of that fluid. This is achieved by the use of mechanical linkages specially designed to optimize the pressure-volume relationships in order ofr the machine to perform efficiently. This volume explains the workings of a variety of positive displacement machines which include pumps, compressors, and gas expanders. Presented at a mathematical and technical level, the most influential research in this field over the past decade or so is examined, along with best practice from industry. The work featured here highlights the importance of using the latest computation techniques, and following proper design procedure to achieve the desired outcome.