Research On Online Real-time Cross-Correlators

Two-phase flow system and multiphase flow system commonly exist in nature and industrial production. Because of the differences in both phase volume fractions and relative movement speeds, as well as the interface effects in two-phase flows, its flow characteristics are far more complex than that in single phase flows. This adds difficulties to the measurement of two-phase flow parameters. Theoretically, the cross-correlation techniques can be used to measure the flow of any fluid system, and it is remarkable for it wide measuring range, thus, it provides great support for solving the problems in related measurement in the two-phase flow system.In the cross correlation flowmeter technique,the successful design of inexpensive,fast and fully functional cross correlators for on-line measurement of flows has been considered a key factor in the popularization and application of this technique in related industry. To solve this problem, much research has been done, and consequently, with the booming microelectronics, great success has been achieved in this field in recent years. This paper proposes an implementation method of cross correlators, which is based on the embedded soft-core processor Niosâ…¡. More specifically, FPGA chip EP2C20Q240C8 SOPC of Cycloneâ…¡series of Altera Corporation is used, and aided by SOPC Builder, a soft-core processor based on the embedded soft-core processor Niosâ…¡has been set up in the design of the software of QUARTUSâ…¡. The main function of the soft-core processor is, firstly, to control the sampling process of A/D converter chips and data storage of upstream and downstream flow noise signals; secondly, to realize cross-correlation operations between sampling data of upstream and downstream in storage. The fluid velocity is obtained after peak searching and calculation of velocities. In the design discussed in this paper, the core program of cross correlation calculation is realized in C language under Nios II IDE development environment, and is downloaded to the embedded Niosâ…¡soft core processor after it is successfully complied.All the module functions of this design including A/D sampling control module and cross correlation calculation module have been correctly commissioned on the embedded Niosâ…¡development board. Also, the cross correlation calculations have been validated via Matlab.