Weixiong Chen

Numerical Investigation of Two-Phase Flow in Natural Gas Ejector

Increasing production and recovery from the mature oil and gas fields often requires a boosting system when the gas pressure is lower than that demanded by the transportation or process system. The supersonic ejector, considered to be a cost-effective way to boost the production of a low-pressure gas well, was introduced into the industrial field. However, the exploitation of natural gas often accompanies with water. The computational fluid dynamics (CFD) technique was employed to investigate the two-phase effect (water droplets) on the performance of natural gas ejector for the motive pressure ranging from 11.0 MPa to 13.0 MPa, induced pressure from 3.0 MPa to 5.0 MPa, and backpressure from 5.1 MPa to 5.6 MPa, while the injected water flow rate was less than 0.03 kg s−1. The numerical results show that the entrainment ratio of the two-phase operation was higher than that of the single-phase operation with the variation of backpressure. Meanwhile, the entrainment ratio increased with the increase of injected water flow rate into the primary flow. When the water was injected into the secondary flow, the entrainment ratio decreased as the injected water flow rate increased, but the critical backpressure remained unchanged.

Experimental and Numerical Analysis on the Internal Flow of Supersonic Ejector Under Different Working Modes

ABSTRACT Supersonic ejectors involve very complex phenomena such as interaction between supersonic and subsonic flows, shock trains, instabilities, which strongly influences the performance of supersonic ejector. In this study, the static pressure distribution along the ejector wall and Mach number distribution along the axis are used to investigate the internal flow field of supersonic ejector. Results indicate that when the back pressure is much less than the critical back pressure, there are two series of shock trains, and the change of the back pressure will not affect the flow field before the effective area section, so the entrainment ratio would remain constant. The second shock train moves further upstream and is combined with the first shock train to form a single shock train as the back pressure rises. When the back pressure is greater than the critical back pressure, the position of the shock train, the static pressure at its upstream and the entrainment ratio, will be affected. The “effective area section” in the mixing tube is obtained. The effective area section position moves downstream with the increase of the primary flow pressure, while it moves upstream with the increase of the secondary flow pressure. The entrainment ratio shows inversely proportional relationship with the effective section position. Besides, the first shock train length increases with the increase of primary flow pressure or secondary flow pressure. The critical back pressure represents direct proportional relationship to the first shock train length.

Supersonic Ejector to Boost Production from Low Pressure Natural Gas Field

An effective way to boost natural gas production from low pressure gas field was introduced in the paper. The supersonic ejector used the energy of high pressure gas wells, which was generally wasted through the choke valve, as its power supply to boost the low pressure gas production. The field experiment of the natural gas ejector was carried out, and the performance of the ejector was also presented. Moreover, the production of low pressure natural gas well was compared when the natural gas ejector was used or not. The economic analysis shows that the recovery period of the capital was less than several months.

Defects in the apoptotic machinery are associated with hepatic damage

With roughly 2 billion people across the world infected with hepatitis B virus (HBV) and 350–400 million persons afflicted with chronic HBV infection, HBV persistence presents a significant global public health problem [1,2]. Three phases of chronic HBV infection have been characterized: immune tolerance, immune active and inactive [3]. It is hypothesized that with the phase transition host gene expression is largely altered. Microarray technology has made it possible to analyse simultaneously the expression of thousands of genes pertinent to various biological functions [4]. However, up to now, studies analysing differential gene expression profiles using clinical samples, which reflect the pathogenesis more physiologically, have not been reported. Here, we analysed the gene expression pattern between persons free of HBV infection and patients with chronic hepatitis B. Eleven patients chronically infected with HBV, four without liver inflammation (healthy carrier group), four with obvious liver inflammation (active liver disease group) and three persons free of HBV infection (control group), were included in this study. Informed consent was obtained from each patient. Total RNA was extracted from peripheral blood mononuclear cells (PBMCs). Microarray analysis was performed according to the Affymetrix instructions for eukaryotic sample preparation. Microarray data were generated using Affymetrix protocols (http://www.affymetrix.com). Absolute expression transcript levels were normalized for each chip by globally scaling all probe sets to a target signal intensity of 1000. To identify genes that were differentially expressed among the three groups of patients, the parametric Welch t-test and the Benjamini and Hochberg false discovery rate for multiple testing correlations were used. The analysis was performed using GeneSpring 7.2 software (Silicon Genetic, Redwood City, CA, USA). We functionally annotated the list of genes to obtain information on each gene (http://genome-www5.stanford.edu). A total of 20 probes involving host–pathogen interaction were statistically differentially expressed among the three groups (Fig. 1). Some of these genes were identified by Wieland et al. [5] and Wu et al. [6]. Even though our list of regulated genes is small, it is interesting to note that significant functional interactions between them have been reported in the literature. One pathway involved in cellular death is implicated by our data. Out of these 20 genes, 12 probes representing 10 human genes are involved in apoptosis (Fig. 2), as several probes contained sequences from the same gene. Genes inducing apoptosis such as TNFSF10, TNFRSF1A and TNFRSF10C were downregulated in the active liver disease group. Genes favouring apoptosis include members of the tumour necrosis factor (TNF) and TNF receptor (TNFR) super family (TNFSF10, TNFAIP6, TNFRSF1A and TNFRSF10C) and caspase 1. These genes were downregulated in the active liver disease group, while the expression of these genes remained almost unchanged in the healthy carrier group when compared with the control group. The finding that genes inducing apoptosis were downregulated in the active liver disease group indicates a correlation between decreased apoptosis in PBMCs and the damage of hepatocytes. The HBV replication cycle is not directly cytotoxic to cells [7]. It is now thought that host immune responses to viral antigens displayed on infected hepatocytes are the principal determinants of hepatocellular injury [8]. The immune responses to HBV and their role in the pathogenesis of hepatitis B are incompletely understood. Evidence exists to suggest that T-cell responses, especially the responses of cytotoxic T lymphocytes, play a central role in viral clearance [9]. Correlative clinical studies show that in acute, self-limited hepatitis B, strong T-cell responses to many HBV antigens are readily demonstrable in the peripheral blood [10]. In contrast, in chronic carriers of HBV, such virus-specific T-cell responses are greatly attenuated, at least as assayed in cells from the peripheral blood. The number of antigen-specific cells is the prominent determinants in the process of virus clearance [11]. Decreased T cell numbers usually lead to the inability of virus clearance and Abbreviations: HBV, hepatitis B virus; PBMCs, peripheral blood mononuclear cells; TNF, tumour necrosis factor; TNFR, TNF receptor. Journal of Viral Hepatitis, 2007, 14, 520–522 doi:10.1111/j.1365-2893.2007.00847.x