Analysis of Clearances in Combined Screw Machines

2005 ◽  
Author(s):  
Ahmed Kovacevic ◽  
Nikola Stosic ◽  
Elvedin Mujic ◽  
Ian K. Smith
Keyword(s):  
Software Package ◽  
Linear Expansion ◽  
Performance Estimation ◽  
Estimation Model ◽  
Discharge Temperature ◽  
Twin Screw ◽  
Simple Expansion ◽  
Differential Thermal Expansion ◽  
Free Machine ◽  
Differential Expansion

Changes caused by differential expansion between the rotors and the casing occur in the high pressure clearances in both the compressor and expander sections when expansion and compression are performed together in a single oil free machine of the twin-screw type. These are more difficult to control than when the two functions are carried out in separate machines. The clearance changes affect both the performance and reliability of the machine but can be controlled by using different materials of construction for each section. Clearances, predicted by the assumption of linear expansion of the components, were included in a well-proven software package for performance estimation of both screw compressors and expanders and the results compared with experimental data. It was found that the clearance in the machine, being dependent on the temperature, could be estimated fairly accurately by matching measured discharge temperature and the temperature obtained by the estimation model. Therefore, a simple expansion analysis of the main machine clearances appeared to be an adequate tool for use in the design of these machines in order to optimise performance and prevent the machine seizing as a result of differential thermal expansion during operation.

scholarly journals Categorification of the Müller-Wichards System Performance Estimation Model: Model Symmetries, Invariants, and Closed Forms

Systems ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 6
Author(s):  
Allen D. Parks ◽  
David J. Marchette
Keyword(s):  
Closed Form ◽  
System Performance ◽  
Algebraic Method ◽  
Expressive Power ◽  
Computer Applications ◽  
Performance Estimation ◽  
Parallel Computer ◽  
Estimation Model ◽  
Data Movement ◽  
Fundamental Symmetry

The Müller-Wichards model (MW) is an algebraic method that quantitatively estimates the performance of sequential and/or parallel computer applications. Because of category theory’s expressive power and mathematical precision, a category theoretic reformulation of MW, i.e., CMW, is presented in this paper. The CMW is effectively numerically equivalent to MW and can be used to estimate the performance of any system that can be represented as numerical sequences of arithmetic, data movement, and delay processes. The CMW fundamental symmetry group is introduced and CMW’s category theoretic formalism is used to facilitate the identification of associated model invariants. The formalism also yields a natural approach to dividing systems into subsystems in a manner that preserves performance. Closed form models are developed and studied statistically, and special case closed form models are used to abstractly quantify the effect of parallelization upon processing time vs. loading, as well as to establish a system performance stationary action principle.

Analytical Model for High–Level Area Estimation of FPGA Design

2016 ◽  
Vol 7 (2) ◽  
pp. 35-44
Author(s):  
Rachna Singh ◽  
Arvind Rajawat
Keyword(s):  
Early Stage ◽  
Estimation Error ◽  
Research Work ◽  
Performance Estimation ◽  
Estimation Accuracy ◽  
Accurate Estimation ◽  
Fpga Design ◽  
Estimation Model ◽  
Area Estimation ◽  
High Level

FPGAs have been used as a target platform because they have increasingly interesting in system design and due to the rapid technological progress ever larger devices are commercially affordable. These trends make FPGAs an alternative in application areas where extensive data processing plays an important role. Consequently, the desire emerges for early performance estimation in order to quantify the FPGA approach. A mathematical model has been presented that estimates the maximum number of LUTs consumed by the hardware synthesized for different FPGAs using LLVM.. The motivation behind this research work is to design an area modeling approach for FPGA based implementation at an early stage of design. The equation based area estimation model permits immediate and accurate estimation of resources. Two important criteria used to judge the quality of the results were estimation accuracy and runtime. Experimental results show that estimation error is in the range of 1.33% to 7.26% for Spartan 3E, 1.6% to 5.63% for Virtex-2pro and 2.3% to 6.02% for Virtex-5.

Performance and Bearing Load Analysis of a Twin Screw Air Compressor

1999 ◽  
Vol 15 (2) ◽  
pp. 69-78 ◽  
Author(s):  
W. S. Lee ◽  
R. H. Ma ◽  
W.F. Wu ◽  
S.L. Chen ◽  
H.W. Hsia
Keyword(s):  
Measured Data ◽  
Specific Power ◽  
Design Parameters ◽  
Air Compressor ◽  
Operational Conditions ◽  
Discharge Temperature ◽  
Oil Flow ◽  
Twin Screw ◽  
Computer Simulation Program ◽  
Bearing Loads

ABSTRACTTo study the performance and estimate the oscillating bearing loads of a twin screw air compressor, a theoretical model is proposed in this paper. Based on the model, a computer simulation program is developed and effects of different design parameters such as rotor profile, geometric clearance, oil injected position, oil temperature, oil flow rate and other operational conditions are investigated. Output variables such as bearing loads, specific power, compression efficiency, volumetric efficiency, discharge temperature are obtained. Some of the results are then compared with experimentally measured data, and good agreements are found between the simulation results and the measured data.

scholarly journals Application of modelling approaches of twin-screw compressors: thermodynamic investigation and reduced-order model identification

2021 ◽  
Vol 312 ◽  
pp. 05001
Author(s):  
Edoardo Di Mattia ◽  
Agostino Gambarotta ◽  
Mirko Morini ◽  
Costanza Saletti
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Pressure ◽  
Operating Conditions ◽  
Simplified Model ◽  
Computational Time ◽  
Discharge Temperature ◽  
Twin Screw ◽  
Shaft Power

Refrigeration is an essential part of the food chain. It is used in all stages of the chain, from industrial food processing to final consumption at home. In these processes, mechanical refrigeration technologies are employed, where compressors increase gas pressure from evaporation to condensation. In industrial refrigeration systems, twin-screw compressors represent the most widely used technology. A detailed mathematical model of a twin-screw compressor has been developed in Simulink® using differential equations for energy and mass balances to simulate the compression cycle that includes suction, compression and discharge phases. Gas pressure and enthalpy can be calculated as time functions during the cycle. However, the computational times obtained limit the possibility to extend the use of the model in the development of control strategies for the whole refrigeration plant in its real operating conditions. Therefore, the detailed model has been used to train a simplified model developed in Matlab®: the simulated mass flow rate, shaft power and the fluid discharge temperature have been employed to identify several geometrical and thermodynamic parameters of the simplified model. The latter relies on non-linear algebraic equations and, thus, requires a very short computational time. A limited performance dataset has been used to train the model, and a different dataset to test it: the results of the models have been compared, and small errors in mass flow rate, shaft power and fluid discharge temperature have been observed.

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