Characteristics of the Water Steam Turbocompressors Applied in the Concentrator Systems

The main geometrical and operating parameters of the water steam centrifugal compressors working in various concentrator operating conditions are realized in this paper. The interdependence between centrifugal stage pressure ratio, peripheral Mach number and impeller peripheral speed, as well the influence of the concentrator system capacity on the dimensions of the centrifugal compressor are determined to obtain the range of reasonable usage of the centrifugal thermocompression systems in the industrial concentrators. The high peripheral impeller speed, high Mach number and high pressure ratio cause separated jet-wake flow and transonic flow phenomena in the water steam centrifugal compressor flow field. The calculating methods for 3-D viscid unsteady transonic fluid flows in the turbocompressors are discussed and the results of CFD simulations and experimental investigations are used for optimal design of the water steam centrifugal compressor flow field. The application of the centrifugal compressor in the industrial concentrators with thermocompression systems and the influence on the energy efficiency of the systems are analyzed. Significant increment of the energy efficiency of the industrial concentrators can be achieved by introduction of the thermocompression systems.

A New Simplified Model of Post Stall Transients inAxial Compression Systems

Based on the theory developed by Moors and Greitzer, a new simplifying approximation, which takesinto account the influence of higher harmonics of rotating waves, is proposed in this paper to get a simplified model of post stall transients in axial compression systems. This approximation leads to a set ofthree simultaneous nonlinear first order partial differential equations. The further investigation of poststall behavior for different response modes of instabilities (rotating stall and/or surge), recoverability,prestall period during stall inception, and the effect of compression system parameters on them canbe carried out by this model and has been discussed in detail in the present paper. It has been foundthat stall inception exhibits a large prestall period in the region with small slope of compressor characteristic, and in this region, final throttle setting, compressor characteristic and time-lag parametershave a strong influence on the period. The inertia parameters of blade rows have a strong influenceon the recoverability of compression systems and the blockage of stall cell at recovery point. Somequalitative comparisons with available experimental results and experience are made, and it shows thatthe proposed model is very simple and reliable.

Numerical Simulation of Active Suppression of Rotating Stallin Axial Compression Systems

In the present paper, a theoretical model is proposed to analyze the transient behavior of suppression of rotating stall in axial compression systems through the use of an additional disturbance. The governing equations of the model are a set of simultaneous nonlinear first order partial differential equations,and for numerical calculations, a simple explicit time marching method can be used. The influence of system parameters on the suppression effectiveness and the interaction between rotating stall and surge have been discussed initially. The analysis of the influence of system parameters presents that both the B parameter and axisymmetric compressor characteristic have significant effect on the stabilization effectiveness of a control strategy. The effectiveness decreases as the value of B and the number of stages or stage loading of the compressor increase. It has been found that the onset flow rate of rotating stall and surge in a compression system may be different, and there is a strong interaction between these two kinds of instabilities. The onset flow rate of pure one dimensional surge depends on the value of B and axisymmetric compressor characteristic, besides the slope of the compressor characteristic.In some cases, when rotating stall which is the natural mode of instability in a compression system is suppressed, one dimensional surge can occur. It often limits the effectiveness of a control strategy to suppress rotating stall. But when surge is initiated by rotating stall, it is also possible to inhibit the occurrence of surge by suppressing rotating stall in a compression system.