Screw compressors [...] Mathematical modelling and performance calculation

The first part of "Screw Compressors" gives a review of recent developments in screw compressor design. The second part presents a generalized mathematical definition of screw machine rotors and describes some well known lobe shapes in detail. The third part treats the mathematical modelling of the thermodynamics and fluid mechanics of compression and expansion processes. This includes discussion of the issues addressed in order to be able to predict the optimum rotor size and speed and built-in volume ratio and, in the case of oil flooded machines, the injection position and jet diameter. The fourth and fifth parts discuss the principles used and describe the application of the analytical procedures and rotor profiling techniques, presented in the earlier chapters, to the design of a number of twin screw compressors, currently manufactured including the examples of combining expansion and compression in the same machine. Althoughtheprinciplesofoperationofhelicalscrewmachines,ascompressors or expanders, have been well known for more than 100 years, it is only during the past 30 years that these machines have become widely used. The main reasons for the long period before they were adopted were their relatively poor e?ciency and the high cost of manufacturing their rotors. Two main developments led to a solution to these di?culties. The ?rst of these was the introduction of the asymmetric rotor pro?le in 1973. This reduced the bl- hole area, which was the main source of internal leakage by approximately 90%, and thereby raised the thermodynamic e?ciency of these machines, to roughly the same level as that of traditional reciprocating compressors. The second was the introduction of precise thread milling machine tools at - proximately the same time. This made it possible to manufacture items of complex shape, such as the rotors, both accurately and cheaply. From then on, as a result of their ever improving e?ciencies, high rel- bility and compact form, screw compressors have taken an increasing share of the compressor market, especially in the ?elds of compressed air production, and refrigeration and air conditioning, and today, a substantial proportion of compressors manufactured for industry are of this type. Despite, the now wide usage of screw compressors and the publication of many scienti?c papers on their development, only a handful of textbooks have been published to date, which give a rigorous exposition of the principles of their operation and none of these are in English.

This book - the authors' second book on screw compressors – presents the results of the most up to date methods of three-dimensional modeling of the fluid dymanics and the solid-fluid interaction within these machines, which are still being developed. By including them in the design process, it is possible, not only to predict flow patterns more accurately, and hence improve the design of the critical components, but also to determine how the pressure and temperature distribution within the compressor distorts the rotors and casing and how this, in turn, has an interactive effect on the performance.

Such calculating facilities are especially valuable for oil free machines, in which temperature changes are much larger and thus make thermal distortion effects more significant. However, it confers advantages in all cases, as improved machine tools enable manufacturing tolerances to be reduced and hence compressors can be built with smaller clearances. Four examples outline the scope of the applied mathematical model for three dimensional calculation of fluid flow and stresses in the solid parts of the screw machine.

This book - the authors'second book on screw compressors – presents the results of the most up to date methods of three-dimensional modeling of the fluid dymanics and the solid-fluid interaction within these machines, which are still being developed. By including them in the design process, it is possible, not only to predict flow patterns more accurately, and hence improve the design of the critical components, but also to determine how the pressure and temperature distribution within the compressor distorts the rotors and casing and how this, in turn, has an interactive effect on the performance. Such calculating facilities are especially valuable for oil free machines, in which temperature changes are much larger and thus make thermal distortion effects more significant. However, it confers advantages in all cases, as improved machine tools enable manufacturing tolerances to be reduced and hence compressors can be built with smaller clearances. Four examples outline the scope of the applied mathematical model for three dimensional calculation of fluid flow and stresses in the solid parts of the screw machine. This book - the authors' second book on screw compressors - presents the results of the most up to date methods of three-dimensional modeling of the fluid dymanics and the solid-fluid interaction within these machines, which are still being developed. By including them in the design process, it is possible, not only to predict flow patterns more accurately, and hence improve the design of the critical components, but also to determine how the pressure and temperature distribution within the compressor distorts the rotors and casing and how this, in turn, has an interactive effect on the performance. Such calculating facilities are especially valuable for oil free machines, in which temperature changes are much larger and thus make thermal distortion effects more significant. However, it confers advantages in all cases, as improved machine tools enable manufacturing tolerances to be reduced and hence compressors can be built with smaller clearances. Four examples outline the scope of the applied mathematical model for three dimensional calculation of fluid flow and stresses in the solid parts of the screw machine "The first part of "Screw Compressors" gives a review of recent developments in screw compressor design. The second part presents a generalized mathematical definition of screw machine rotors and describes some well known lobe shapes in detail. The third part treats the mathematical modelling of the thermodynamics and fluid mechanics of compression and expansion processes. This includes discussion of the issues addressed in order to be able to predict the optimum rotor size and speed and built-in volume ratio and, in the case of oil flooded machines, the injection position and jet diameter. The fourth and fifth parts discuss the principles used and describe the application of the analytical procedures and rotor profiling techniques, presented in the earlier chapters, to the design of a number of twin screw compressors, currently manufactured, including examples of combining expansion and compression in the same machine."--Résumé de l'éditeur "The first part of "Screw Compressors" gives a review of recent developments in screw compressor design. The second part presents a generalized mathematical definition of screw machine rotors and describes some well known lobe shapes in detail. The third part treats the mathematical modelling of the thermodynamics and fluid mechanics of compression and expansion processes. This includes discussion of the issues addressed in order to be able to predict the optimum rotor size and speed and built-in volume ratio and, in the case of oil flooded machines, the injection position and jet diameter. The fourth and fifth parts discuss the principles used and describe the application of the analytical procedures and rotor profiling techniques, presented in the earlier chapters, to the design of a number of twin screw compressors, currently manufactured, including examples of combining expansion and compression in the same machine."--BOOK JACKET The first part of "Screw Compressors" gives a review of recent developments in screw processor design. The second one presents the method of mathematical definition of a general case of screw machine rotors and describes the details of lobe shape specification. The third part treats the model of the thermodynamics and compression-expansion process, discusses some modelling issues and compares the shapes of new and conventional profiles. The fourth part presents the design of a high efficiency twin screw compressor with new rotor profiles. A well proven mathematical model of the compression process within positive displacement machines was used to determine the optimum rotor size and speed, the volume ratio and the oil injection position and jet diameter. TOC:Introduction.- Screw Compressor Geometry.- Calculation of Screw Compressor Performance.- Principles of Screw Compressor Design.- City Screw Compressor Designs.- Conclusions "This book - the authors' second book on screw compressors - presents the results of the most up to date methods of three-dimensional modeling of the fluid dymanics and the solid fluid interaction within these machines, which are still being developed. By including them in the design process, it is possible, not only to predict flow patterns more accurately, and hence improve the design of the critical components, but also to determine how the pressure and temperature distribution within the compressor distorts the rotors and casing and how this, in turn, has an interactive effect on the performance."--Jacket The operating principle of screw machines, as expanders or compressors, has been known for over 120 years.