The Time Domain of Centrifugal Compressor and Pump Stability and Surge

1977 ◽  
Vol 99 (1) ◽  
pp. 53-59 ◽  
Author(s):  
R. C. Dean ◽  
L. R. Young
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Time Domain ◽  
Flow Model ◽  
Centrifugal Compressors ◽  
Stable Regime ◽  
Compliant Systems ◽  
The Time Domain ◽  
New Evidence

New evidence about the time domain operation of centrifugal compressors and pumps in compliant systems is presented. Data from Toyama [1,2] plus unpublished data from another compressor indicate that the flow rate oscillates continuously, at large amplitudes, when a compressor is operating in its supposedly stable regime. A tentative flow model predicts similar oscillations. The model assumes that the compressor operation at all times is described by its quasi-steady characteristic; no hysteresis or complex aerodynamic phenomena have been invoked.

Well Testing Applications of Numerical Laplace Transformation of Sampled-Data

1998 ◽  
Vol 1 (03) ◽  
pp. 268-277 ◽  
Author(s):  
M. Onur ◽  
A.C. Reynolds
Keyword(s):  
Parameter Estimation ◽  
Flow Rate ◽  
Time Domain ◽  
Laplace Transformation ◽  
Numerical Inversion ◽  
Rate Data ◽  
Sampled Data ◽  
Laplace Domain ◽  
The Time Domain ◽  
Measured Pressure

Abstract In recent years, the numerical Laplace transformation of sampled-data has proven to be useful for well test analysis applications. However, the success of this approach is highly dependent on the algorithms used to transform sampled-data into Laplace space and to perform the numerical inversion. In this work, we investigate several functional approximations (piecewise linear, quadratic, and log-linear) for sampled-data to achieve the "forward" Laplace transformation and present new methods to deal with the "tail" effects associated with transforming sampled-data. New algorithms that provide accurate transformation of sampled-data into Laplace space are provided. The algorithms presented can be applied to generate accurate pressure-derivatives in the time domain. Three different algorithms investigated for the numerical inversion of sampled-data. Applications of the algorithms to convolution, deconvolution, and parameter estimation in Laplace space are also presented. By using the algorithms presented here, it is shown that performing curve-fitting in the Laplace domain without numerical inversion is computationally more efficient than performing it in the time domain. Both synthetic and field examples are considered to illustrate the applicability of the proposed algorithms. Introduction Due to its efficiency, the Stehfest algorithm for the numerical inversion of the Laplace transform is now a well established tool in pressure transient analysis research and applications. Roumboutsos and Stewart showed that convolution and deconvolution in Laplace domain with the aid of the numerical Laplace transformation of measured pressure and/or rate data is more efficient and stable than techniques based on the discretized form of convolution integral in the time domain. Use of the numerical Laplace transformation of tabulated (pressure and/or rate) data has become increasingly popular in recent years for other well testing analysis purposes in a variety of applications; see for example, Refs. 3-10. Guillot and Horne were the first to use piecewise constant and cubic spline interpolations to represent measured flow rate data in Laplace space for the purpose of analyzing pressure tests under variable (downhole or surface) flow rate history by nonlinear regression. Roumboutsos and Stewart were the first to introduce the idea of using the numerical Laplace transformation of measured data for convolution and deconvolution purposes. They presented an algorithm based on piecewise linear interpolation of sampled-data, which can be used to transform measured pressure or rate data into Laplace space. Mendes et al. presented a Laplace domain deconvolution algorithm based on cubic spline interpolation of sampled-data. By considering deconvolution of DST data, they showed that Laplace domain deconvolution is fast and more stable than deconvolution methods based on the discretized forms of the convolution integral in the time domain. However, they noted that noise in pressure and flow rate measurements can also cause instability in Laplace space deconvolution methods, but they did not present any specific results on this issue. Both Corre and Thompson et al. showed that the convolution methods based on a representation of the linear interpolation of the tabulated unit-rate response solution and numerical inversion to the time domain are far more computationally efficient for generating variable rate solutions for complex well/reservoir systems (e.g., partially penetrating wells and horizontal wells) than convolution methods based on the direct use of analytical solutions in Laplace space. Using the numerical Laplace transformation of measured pressure data, Bourgeois and Horne introduced the so-called Laplace pressure and its derivative, and presented Laplace type curves based on these functions for model recognition and parameter estimation purposes. They also deconvolved data using these Laplace pressure functions in the Laplace domain without inversion to the time domain. Wilkinson investigated the applicability of performing nonlinear regression based on the Laplace pressure as suggested in Ref. 7 for parameter estimation purposes.

Experimental research on stability enhancement for centrifugal compressors using active control casing treatment system

2017 ◽  
Vol 231 (5) ◽  
pp. 333-343 ◽  
Author(s):  
Yuanyang Zhao ◽  
Qichao Yang ◽  
Liansheng Li ◽  
Jun Xiao ◽  
Yue Shu ◽  
...  
Keyword(s):  
Active Control ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Gas Flow ◽  
Treatment System ◽  
Stable Operation ◽  
Centrifugal Compressors ◽  
Rotating Speed ◽  
Casing Treatment ◽  
Operating Stability

Centrifugal compressors are widely used in many fields, where they become unstable when operated at the edge of the surge line. This paper presents a method, which is based on the active control casing treatment to enhance the operating stability of the centrifugal compressor. To investigate the effect of the active control casing treatment system on the performance of a centrifugal compressor, a test rig with rotating speed of 15,000 r/min was built up. The experimental results show that the active control casing treatment system can significantly decrease the surge flow rate and extend the envelope of stable operation via injecting gas (so-called the control gas) into the casing of the centrifugal compressor. The tested maximal enhancement ability is 30.55% at the condition of 10,586 r/min when the flow rate of the control gas is 2.5 m3/min. It was found that the enhancement ability increases with the decrease of the rotating speed of the centrifugal compressor. The increment of the control gas flow rate results in a smaller surge flow rate of the centrifugal compressors.

Slip Factor of a Centrifugal Compressor and Its Variation with Flow Rate

1974 ◽  
Vol 188 (1) ◽  
pp. 415-421 ◽  
Author(s):  
A. Whitfield
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Flow Model ◽  
Design Flow ◽  
Wake Flow ◽  
Flow Rates ◽  
One Dimensional ◽  
Slip Factor ◽  
Performance Map ◽  
The Many

To predict the complete performance map of turbocharger centrifugal compressors, it has been found essential to include a procedure for estimating the slip factor at off-design flow rates. The many correlations available for the slip factor only concern themselves with design-point operation and consequently only provide a single value for the slip factor. The approach presented here attempts, within the confines of a one-dimensional procedure, to recognize the changing flow pattern at the impeller discharge in order to predict the variation of slip factor with flow rate. The procedure is based upon the well-established jet-wake flow model of Dean and the overall slip factor calculated from the jet slip factor. Experimental and theoretical slip factors are presented for three impellers with 34, 30 and 12 radial blades, respectively. The complete performance map of the 12-bladed turbocharger compressor and the effect of using a constant and varying slip factor on the predicted performance are presented.

scholarly journals Modeling and Design of a Controller for a Dehumidifier

2020 ◽  
Author(s):  
Vijaya Saraswathi R J ◽  
Sukambika S ◽  
Wilcy Theresa F ◽  
Ishwarya M ◽  
Srinithi T
Keyword(s):  
Flow Rate ◽  
Cold Storage ◽  
Time Domain ◽  
Output Signal ◽  
Centrifugal Separator ◽  
Set Point ◽  
Input Signals ◽  
Humidity Chamber ◽  
Secondary Air ◽  
The Time Domain

Many industries like pharmaceutics, plastics, food and confectionery, tobacco and cold storage, maintaining the humidity at the desired level is very important. The aim of this paper is to process the model and to design a controller for a dehumidifier to control the humidity at the desired set point. The air is humidified using a humidity chamber. This humid air which is the primary air is mixed with secondary air from the compressor and sent to the dehumidifier. The dehumidifier used here is a centrifugal separator. The humidity of the dehumidified air is measured using a sensor. The output signal of the sensor is compared to the set point. If the output measured exceeds the set point, accordingly the flow rate of the secondary air to the dehumidifier is varied until it reaches the desired set point .The model of the process is identified from the response of the process to the input signals. The controller is designed for the model obtained and the performance of the controller based on the time domain specification is compared.

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