Study on unsteady flow collaborative characteristics of semi-open impeller and diffuser in a centrifugal compressor
Centrifugal compressor, as the significant equipment in the energy field, is of very complexity in its structure. Good collaboration of individual components determines the good aerodynamic performance and running security of the compressor. Unsteady simulations were performed, based on the platform of CFX and through the UDF interface program, to evaluate the 3D collaborative aerodynamic characteristics of a semi-open impeller and diffuser in a large centrifugal compressor, and the numerical study was focused on the impeller-diffuser interaction. The result obtained from flow structures shows the development of low-velocity vortexes in the diffuser flow passage is affected by impeller-diffuser interaction. The low-velocity vortex may increase flow resistance of the flow passage, however, improving at some extent the flow condition of the neighbor one, which generates a kind of low-frequency interference. In addition, the strongest interface effect is located on the rotor blade trailing edge and the diffuser vane leading edge. Amplitude-frequency characteristics converted from the pressure pulsation on monitor points indicate that the rotor wake flow and potential repercussion of diffuser work together to generate strong vibration and excitation force. The impeller-diffuser interaction is stronger under winter operating condition than it is under design condition. Meanwhile, the impact of diffuser exerts dominating effects on the excitation force near the impeller, which should be considered when exploring the impeller damage accident causes under winter operating condition.
Survey of Failure of Large Process Compressor in Chinese and Failure Prevention Countermeasure
Based on the surveys of failures of large process compressors in petrochemical plants,the failure mode and the failure cause of the critical components of compressors were analyzed and the general problems existed in process compressors were represented.Then the countermeasures of long-term operation of compressor under extreme and complex conditions were pointed out.Lastly,the prospects of key and common technologies of process compressors need to further develop were presented.
Accurate measurements of output characteristics and detonations of motorbike high-speed racing engine and their optimization at actual atmospheric conditions and combusted mixture composition
Abstract At a motorbike high speed racing engine there is very important an output engine characteristics which depends significantly on a detonation combustion rate, atmospheric conditions and a combusted mixture composition. The combustion process has got a relevant influence on a wear degree of main engine parts or on their damage eventually. The detonation combustion rate is very important because this kind of burning can be not only destructive but a useful phenomenon, as well. If the process of detonation burning is kept on a certain level, it can help significantly to the next increasing of an engine power output. In this article there is described the measurements of output characteristics of a high-speed racing engine which were performed by means of a data-recording system and the detonation combustion was evaluated using a quantitative method. The actual values of atmospheric conditions and the mixture composition were added to the measured values. Then the obtained values are compared visually with a damage degree of an engine piston caused by the detonation burning. The result is a limit value expressed in a number of detonation units related to a run distance interval of the vehicle driven by the high-speed racing engine. In framework of this run distance interval there is the process of detonation burning profitable. As well as it increases an engine power output and together it is not destructive with regard to engine design parts.