Venturi meters are playing an increasingly important role in wet gas metering in natural gas and oil industries. Convincible measurement of the flowrate of wet gas requires two parameters, namely, the whole mass flowrate and its quality. It is commonly believed that the two parameters can be obtained if the Venturi meter is combined with another device of a different principle. However, this is not always the case. Owing to the complexity of the model for wet gas metering, the problem of multiple solutions may occur. Proceeding from a static model on the differential pressure (DP) signal of the Venturi meter, a dynamic model is presented that can provide an extra functional relation to resolve this problem without the need of adding a third device. This functional relation monotonously maps the relative fluctuation of the DP signal to the quality of the wet gas and simplifies the selection of the true solution. Experiments have been carried out within static pressure range of 0.3-0.8 MPa, gas flowrate range of 50-100 m3/h and quality range of 0.06-0.412. Emphasis of the experiments has been on the demonstration of the validity of the static and dynamic models. Finally, appropriate discussions and conclusions are given. © 2003 Elsevier Ltd. All rights reserved.

Presented in this paper is a distortion-free filtering approach for cancellation of sinusoidal harmonic interference using wavelet packet decomposition (WPD). Under a special sampling condition, the transform coefficients of the harmonic interference in each subband become a constant, exhibiting as a shift of the baseline of the WPD coefficients in that subband. The harmonic interference is thus removed by shifting the baselines back to zero. Unlike the use of a notch or a comb filter, the new approach does not cause any distortion to the original signal in principle. This advantage makes this approach especially suitable for the removal of harmonic interference that is located within the spectrum of the original signal. Evaluation of the new approach has been conducted using a simulated piecewise smooth signal and a real, irregularly pulsating signal. Results obtained from the studies have demonstrated the effectiveness of the new approach.

The oscillation frequency of a combustion flame that is directly measured from the spectrum of a flame signal often depends on the level of white noise in the signal and the sampling rate. As long as the signal contains white noise, the "true" value of the oscillation frequency will never be known. However, the effect of the white noise and sampling rate on oscillation frequency measurement can be minimized by incorporating a new computing algorithm into the measurement software. The algorithm is developed by making two improvements to the original direct calculation method. One of the improvements is the wavelet-based prefiltering of the raw flame signal. The other is an adaptive truncation of the spectrum of the filtered signal. The improved algorithm is evaluated by using a flame signal that is acquired from an industrial-scale combustion test facility. Results that are obtained are reported and discussed.

In this paper, we present a new flame monitor that uses three photovoltaic cells covering the ultraviolet (UV), visible, and infrared (IR) spectral bands. A gain-adjustable amplifier is incorporated into the monitor so that it is applicable to the coal, oil, or gas-fired flames. Self-checking of the monitor is implemented through cross correlation of the signals from the three cells, and hence, no additional self-checking hardware is required. Both the oscillation frequency and the brightness of the flame are used to monitor flame stability and to detect flame presence as well as sighting-tube blockage. Unlike conventional single-cell flame detectors, the new multicell devices can still be in operation before being repaired, after a cell-failure alarm has gone off. Experiments were carried out on an industrial-scale combustion test facility in order to demonstrate the operability and efficacy of the new flame monitor.

The progress of process tomography provides a new method for two-phase flow measurement. The dual-plane electrical resistance tomography (ERT) is combined with the correlation measurement technique to carry out the two-phase flow measurement in which the continuous phase is conductive liquid. The method of the estimation of void fraction and the disperse phase velocity by extracting the eigenvalue of the dual-plane ERT boundary measured data is presented. This method is applied to the transient flow-rate measurement of the air-water two-phase flow in vertical pipe. The information of disperse phase void fraction and distribution variation with time change can be considered adequately, and the estimated value of disperse phase void fraction and velocity can be gained fairly accurately in this method, which provides the data for the calculation of the transient flow-rate. The experiment results indicate that this kind of measurement method is valid when the distance between the upstream and downstream measured cross section is short enough. © 2005 Elsevier Ltd. All rights reserved.

Multielectrode inductance flowmeters were brought forward toward coping with the problem of flow regime dependence of traditional inductance flowmeters. Design of the electrode array is of great importance in construction of a multielectrode inductance flowmeter. The number of electrodes and electrode size are two primary parameters of the array. In this paper, the governing equation of the multielectrode inductance flowmeter was solved using a finite difference method. The chord measurement method was employed to analyze the influences of both parameters on the estimation of mean flow velocity. Based on the quantitative calculation of the influences of the two parameters on measurement error, criteria for the design of the electrode array were presented.

A parallel-plate capacitance-based sensor configuration which can be used to measure low mass concentrations down to a few tens of g/m3 for gas-particle systems and to study the influence of the particle characteristics such as particle size, packing or agglomeration on the effective permittivity of the mixture was developed. In this sensor a two channel symmetric structure and an AC bridge circuit were adopted to minimise the influence from the surrounding factors such as temperature, pressure and humidity. The inner diameter of the flow pipeline is 18mm, the dimension of the capacitance plate is 100mm 50mm and the distance of the two plates is 10mm. To measure the concentration of particles an in situ two-step measurement was proposed, i.e. zero point and loading measurements. Emphasis was made on estimation of the static and dynamic performance of the capacitance sensor and configuration. The baseline drift of the sensor and the influence of surrounding factors were studied. Dynamic experiments show a relative measurement error of 8% in the range from 10 to 300g/m3. Static experiments for locally packed particle-gas systems show that the response of the sensor depends not only on particle material but also on particle size.

This paper presents a novel approach for on-line fuel identification using digital signal processing (DSP) and fuzzy inference techniques. A flame detector containing three photodiodes is used to derive multiple signals covering a wide spectrum of the flame from infrared to ultraviolet through visible band. Advanced digital signal processing and fuzzy inference techniques are deployed to identify the dynamic "fingerprints" of the flame both in time and frequency domains and ultimately the type of coal being burnt. A series of experiments was carried out using a 0.5-MWth combustion test facility operated by RWE Innogy plc, U.K. The results obtained demonstrate that this approach can be used to identify the type of coal being burnt under steady combustion conditions.

In this paper a dual-channel pseudo-random signal generator is presented for the calibration of cross-correlators such as cross-correlation-based flowmeters. In this signal generator, the two channels have completely identical hardware structures so that they generate two identical sequences of pseudo-random signals to simulate two signals obtained from the upstream and downstream sensors of a cross-correlator, respectively. Special control strategies both in hardware and software have been implemented in such a way that the control error of time delay between the two channels can be reduced to less than a microsecond. The shift frequency and sequence length of each signal channel and the time delay between the two channels can be adjusted in wide ranges to satisfy majority of practical requirements. The start/stop control of each channel of signal and adjustments of the above parameters are carried out by a micro-controller with a dedicated keyboard and an LED display. The instrument has been evaluated by using a digital storage oscilloscope (Tektronix TDS220). Results obtained show that the control precision of the time delay is better than 0.05% when the time delay is 1ms and over. Comparison with an E+H commercial noise signal generator and an MP noise generator shows that the error of the new generator is much smaller than those of the other two.