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Colorectal cancer (CRC) is the most common tumor of the digestive system and the third most common tumor worldwide. To date, the prognosis of CRC patients remains poor. It is urgent to identify new therapeutic targets for CRC. As a tumor suppresser, microRNA (miRNA) miR-502-5p is downregulated in CRC tissues. Nevertheless, the role of miR-502-3p in CRC is largely unclear. Besides, the transcript factor forkhead box protein O1 (FOXO1) could suppress the CRC cell growth. However, the effect of FOXO1 on miR-502-3p in CRC remains unknown. By contrast, cyclin-dependent kinases 6 (CDK6) promotes the CRC cell growth. Yet the regulatory effect of miR-502-3p on CDK6 in CRC has not been reported. Thus, the primary aim of this study was to investigate whether FOXO1 enhanced miR-502-3p expression to suppress the CRC cell growth by targeting CDK6. Here, RNA level and protein level were detected by quantitative reverse transcription-PCR (qRT-PCR) and western blot (WB), respectively. Besides, the cell growth was detected by Cell Counting Kit 8 (CCK8) assay. Moreover, the regulatory effect of FOXO1 on miR-502-3p or miR-502-3p on CDK6 was determined using dual-luciferase reporter gene (DLR) assay. Results revealed that miR-502-3p and FOXO1 were downregulated in CRC cells. Besides, miR-502-3p suppressed the CRC cell growth. Moreover, FOXO1 could increase the miR-502-3p level through facilitating MIR502 transcription in CRC cells. In addition, miR-502-3p could suppress the CRC cell growth by targeting CDK6. These findings indicated that FOXO1 induced miR-502-3p expression to suppress the CRC cell growth through targeting CDK6, which might provide new therapeutic targets for CRC.

Colorectal cancer (CRC) is the most common malignant tumor occurred in digestive system. However, the prognosis of CRC patients is poor. Therefore, it is urgent to illuminate the mechanism suppressing CRC and explore novel targets or therapies for CRC treatment. MicroRNAs (miRNAs) are a class of non-coding RNAs with a length of 20-23 nucleotides encoded by endogenous genes, which are associated with the development of a variety of cancers, including CRC. Studies have shown that miR-19a is identified as oncogenic miRNA and promotes the proliferation, migration and invasion of CRC cells. However, the relationship between miR-19a and ferroptosis in CRC remains unknown. Here, we reported that iron-responsive element-binding protein 2 (IREB2), as an inducer of ferroptosis, was negatively regulated by miR-19a. IREB2 is a direct target of miR-19a. In addition, ferroptosis was suppressed by miR-19a through inhibiting IREB2. Thus, we proposed a novel mechanism of ferroptosis mediated by miR-19a in CRC cells, which could give rise to a new strategy for the therapy of CRC.

In clinical practice, we found that microRNA (miR)-146a-5p is significantly up-regulated in peripheral blood mononuclear cells (PBMCs) of primary sjögren’s syndrome (pSS) patients. In vitro experiments confirmed that miR-146a-5p promotes T helper 17 (Th17) cell differentiation, but the specific mechanism is still unknown. To solve this problem, 20 pSS patients and 20 healthy subjects were enrolled in this study and PBMCs were isolated from their blood. The expression of the membrane IL-23 R (mIL-23 R) in PBMCs was determined. CD3+ T cells were also isolated and used to further analyze the relationship between the ectodomain shedding of mIL-23 R and a disintegrin and metalloprotease 17 (ADAM17). Finally, miR-146a-5p inhibitor and mimics were transfected into PBMCs to evaluate the relationship between ADAM17 and mIL-23 R, and explore the role of mIL-23 R and ADAM17 in Th17 cell differentiation. Our results revealed a significantly increased expression of miR-146a-5p in PBMCs from pSS patients and significantly increased percentage of Th17 cells compared to PBMCs from healthy controls. Under polarization culture conditions, pSS patient-derived PBMCs can more easily differentiate into Th17 cells, which was, to a great extent, attributable to the increased expression of mIL-23 R. Moreover, ADAM17, an ectodomain sheddase of mIL-23 R, was targeted and negatively regulated by miR-146a-5p, which reduced the ectodomain shedding of mIL-23 R. Overall, our results suggested that miR-146a-5p could promote Th17 cell differentiation through targeting and negatively regulating ADAM17. Thus, these results might offer a new approach in the treatment of pSS., Graphical abstract

In order to improve the standardization and accuracy of business process management of laboratory department in hospitals, combined with convolutional neural networks (CNN) and face recognition technology, an association application system of laboratory face recognition and test-tube barcode is designed by inputting patient’s face and blood test-tube barcode into the system for storage. When the patient logs into the system again, the system uses the patient’s face to automatically search for a matching test-tube barcode to obtain the test results. The simulation results show that the system can accurately recognize the face and match the corresponding test-tube barcode, and the accuracy and ROC of face recognition are 0.85 and 0.94, respectively. In addition, when the patient’s face is within 5 m from the system camera, the accuracy of face recognition can reach 100%. It can be seen that the system designed in this paper shows good performance.

In view of the problems of low signal-to-noise ratio and low resolution of seismic data in shallow-thin reservoir in Chunfeng Oilfield of Junggar Basin, stepped and detailed data processing and interpretation technologies are proposed for shallow-thin reservoir prediction. The overlapping type offset packet processing technology can increase seismic fold from 8 to 16 times and increase signal to noise ratio by 1.4 times at local low noise ratio area by fine processing including frequency upgrade and de-noise imaging techniques. This study established three-level prediction techniques including pre-stack improving resolution target processing, post-stack wavelet reconstruction frequency extension, pre-stack and post-stack joint inversion, which can increase sand resolution from 12 m to 2 m and improve the identification accuracy of reservoir efficiently. The shallow-thin reservoirs after frequency extension have continuous and defined reflections, which are well coincided with actual exploration. The seismic data have well ability of preserving amplitude, and achieve good application effects. Key words: Junggar Basin, Chunfeng oilfield, Miocene Shawan Formation, reservoir prediction, wavelet reconstruction, pre-stack and post-stack joint inversion

MicroRNA (miRNA) play a pivotal role in the development of liver fibrosis. However, the functions of miRNA in hepatitis C virus (HCV)-related liver fibrosis remain unclear. In this study, we systematically analyzed the microarray data of the serum miRNA in patients with HCV-induced hepatic fibrosis. Among 41 dysregulated miRNA, miR-1273g-3p was the most significantly upregulated miRNA and correlated with the stage of liver fibrosis. Overexpression of miR-1273g-3p could inhibit translation of PTEN, increase the expression of α-SMA, Col1A1, and reduce apoptosis in HSCs. Hence, we conclude that miR-1273g-3p might affect the activation and apoptosis of HSCs by directly targeting PTEN in HCV-related liver fibrosis.

Objective To investigate the regulation mechanism of T cell immunoglobulin and mucin domain-3 (Tim-3) combined with toll-like receptor 3 (TLR3) or TLR4 on antiviral immune and inflammatory response in patients with chronic hepatitis C virus (HCV) infection. Methods Patients with chronic HCV infection and healthy control subjects were recruited. Patients received interferon (IFN)-α based therapy. Plasma galectin-9 (Gal-9) was quantitated. Peripheral blood mononuclear cells (PBMCs) were cultured with TLR3 or TLR4 agonists, alone or in combination with Tim-3 antagonist. Levels of IFN-α, TNF-α, and 2′-5′ oligoadenylate synthetase (2′-5′OAS), myxovirus resistance protein A (MxA) and suppressor of cytokine 1 (SOCS1) RNA in PBMC cultures were evaluated. Results Plasma Gal-9 levels were increased in patients ( n = 52) compared with controls ( n = 20) and significantly declined at treatment week 12 and 24 weeks post-treatment. IFN-α, 2′-5′OAS, MxA, TNF-α and SOCS1 were upregulated by TLR3 and TLR4 agonists. TNF-α and SOCS1 levels were suppressed by the addition of Tim-3 antagonist. Conclusions Tim-3 blockade in combination with TLR activation induces the expression of antiviral molecules without a significant increase in TNF-α or SOCS1.

It has been reported that treatment with telbivudine might be associated with a significant improvement of renal function in patients with chronic hepatitis B. To confirm this finding, a systematic literature review was conducted. Four online databases (PubMed, CNKI/FMJS, Ovid and SpringerLink) were searched. Serum creatinine, glomerular filtration rate and estimated glomerular filtration rate changes from baseline to the end of the treatment were analyzed. A total of seven full-text articles and 13 abstracts with sample sizes ranging from 15 to 689 patients fulfilled the selection criteria for review. The results showed that long-term treatment with telbivudine, either as monotherapy or combined with other nucleos(t)ide analogs, can significantly improve renal function in chronic hepatitis B patients, particularly those at high risk of renal impairment.

Previous studies using microRNA (miRNA or miR) microarrays have demonstrated that miR-1273g-3p is upregulated in patients with hepatitis C virus (HCV)-associated fibrosis. As miRNAs have been suggested to be promising non-invasive biomarkers, the aim of the present study was to assess whether miR-1273g-3p may be useful as a potential indicator of fibrosis progression in patients with HCV. Liver biopsies were performed on 112 patients with chronic hepatitis C (CHC) and liver stiffness measurements (LSM) were performed using FibroTouch. Liver fibrosis was determined based on Meta-analysis of Histological Data in Viral Hepatitis classification, and the aspartate aminotransferase (AST)-to-platelet count (PLT) ratio index (APRI) and Fibrosis-4 score (FIB-4) were calculated. The diagnostic performance of miR-1273g-3p, LSM, APRI and FIB-4 in predicting fibrosis stage were evaluated and compared by receiver operating characteristic (ROC) analysis. It was demonstrated that miR-1273g-3p levels were significantly positively correlated with the liver fibrosis stage (r=0.657, P

Activation of the innate immune system is involved in the development of chronic liver diseases, including nonalcoholic steatohepatitis. Toll‑like receptor 4 (TLR4) is one of the sensors of the innate immune system. The aim of the present study was to elucidate the role of the TLR4‑dependent signaling pathway, and examine the effect of pioglitazone on hepatic fibrosis, through modulation of the TLR4 pathway in a mouse model of nutritional fibrotic steatohepatitis. Male C57BL/6J mice were fed a methionine‑choline deficient (MCD) diet for 8 weeks to induce nonalcoholic fibrotic steatohepatitis. The PPARγ agonist, pioglitazone, and PPARγ inhibitor, GW9662, were administered to the mice, respectively. The effects of the induction of PPARγ on liver biochemistry and histology, the modulation of TLR4 and its downstream pathway, and the expression levels of inflammatory and fibrogenic genes were assessed using reverse transcription‑quantitative polymerase chain reaction and Western blot analyses. The MCD‑fed mice exhibited progressive hepatic steatosis, necrotic inflammation and fibrosis, along with increase levels of serum alanine aminotransferase and aspartate aminotransferase, accompanied by the upregulation of TLR4, the TLR4‑myeloid differentiation primary response gene 88‑dependent pathway and downstream genes, and proinflammatory and profibrotic genes; and downregulation of basic membrane protein and activin membrane‑bound inhibitor. The administration of pioglitazone was found to reverse hepatic nutritional fibrosis via restoration of the expression levels of proinflammatory and profibrotic genes in the MCD‑fed mice. The results of the present study provide novel evidence supporting the protective role of pioglitazone in ameliorating nutritional fibrotic steatohepatitis, through modulation of the TLR4‑mediated signaling pathway.

Objective To evaluate whether gamma-glutamyl transpeptidase to platelet ratio index (GPRI) can diagnose the extent of liver fibrosis in Chinese patients with chronic hepatitis B (CHB) infection. Methods This prospective observational study used liver biopsy results as the gold standard to evaluate the ability of GPRI to predict hepatic fibrosis compared with two other markers, the aspartate aminotransferase (AST) to platelet ratio index (APRI) and fibrosis-4 score (FIB-4). The clinical and demographic factors that affected GPRI, independent of liver fibrosis, were assessed using multivariate linear regression analyses. Results This study enrolled 312 patients with CHB. GPRI had a significantly positive correlation with liver fibrosis stage and the correlation coefficient was higher than that for APRI and FIB-4. The areas under the receiver operating curves for GPRI for significant fibrosis, bridging fibrosis, and cirrhosis were 0.728, 0.836, and 0.842, respectively. Of the three indices, GPRI had the highest diagnostic accuracy for bridging fibrosis and cirrhosis. Age, elevated AST and elevated total bilirubin levels were independent determinants of increased GPRI. Conclusion GPRI was a more reliable laboratory marker than APRI and FIB-4 for predicting the stage of liver fibrosis in Chinese patients with CHB.

Mounting evidence indicates that dysregulated microRNAs (miRNAs) are important in the etiology and pathogenesis of steatohepatitis. However, the functions of miRNAs in the pathophysiological process of non-alcoholic steatohepatitis (NASH) are poorly understood. In this study, C57BL/6J mice were fed a methionine-choline‑deficient (MCD) diet for eight weeks in order to induce hepatic steatohepatitis. Using reverse transcription polymerase chain reaction, the hepatic expression levels of miR-199a-5p, miR-122 and miR-221 in the mice were examined. Bioinformatic analysis of dysregulated miR-199a-5p was performed to predict the potential role of miR‑199a‑5p in NASH. The MCD diet was found to significantly reduce miR-122 expression levels and significantly increase miR‑199a-5p expression levels in mouse livers, compared with those of mice fed a control diet. In the bioinformatic analysis, miR‑199a‑5p was identified to be predominantly involved in transcription, protein serine/threonine kinase activity, insulin signaling, and the Wnt and mitogen‑activated protein kinase signaling pathways. The regulation of nuclear receptor corepressor 1 (NCOR1) by miR‑199a-5p was also examined by silencing and overexpressing this miRNA in LX-2 cells. The data revealed that NCOR1 protein levels were significantly reduced and enhanced by miR-199a-5p mimic and inhibitor, respectively. These findings suggest a key role for miR-199a-5p in the progression of NASH through inhibition of NCOR1 translation, and provide novel insights into NASH pathogenesis.

Interleukin-23 (IL-23) and its downstream factor IL-17 are the key cytokines involved in immune and inflammatory response in chronic liver diseases. This study aimed to investigate the role and molecular mechanisms of the IL-23/Th17 axis in chronic hepatitis C virus (HCV) infection, and the efficacy of IL-23/Th17 modulation in response to anti-HCV therapy. Sixty-six HCV-infected patients and 20 healthy controls were enrolled. The patients received PegIFNa-2a and ribavirin therapy for at least 48 weeks. The plasma level of IL-23 and the number of IL-17A-, IFN-γ-, and IL-21-producing peripheral blood mononuclear cells (PBMCs) at baseline and 12, 24, and 48 weeks following treatment were determined. The mRNA level of Th17 immune-associated molecules in PBMCs was evaluated by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) following treatment with IL-23 agonist or antagonist. Our data showed that, compared to healthy controls, HCV-infected patients had an increased plasma level of IL-23 and increased frequencies of IL-17A- and IFN-γ-producing PBMCs, whereas the HCV patients exhibited a reduced number of IL-21-producing PBMCs. However, the baseline frequencies of IL-21-producing PBMCs were markedly higher in HCV patients who achieved rapid virological response (RVR) than those without RVR. Additionally, the mRNA expressions of IL-21, IFN-γ, myxovirus resistance protein A (MxA), and suppressor of cytokine signaling 3 (SOCS3) were significantly upregulated in PBMCs, while FoxP3 expression was suppressed by IL-23 agonist. Thus, the IL-23/Th17 axis plays an important role in development of chronic HCV infection and antiviral response. IL-23 may enhance the antiviral activity of interferon-based therapy by modulating the expression of Th17 cells-associated molecules in HCV-infected patients.

Long non-coding RNA (LncRNA)-activated by transforming growth factor-beta (LncRNA-ATB) is a key regulator of transforming growth factor-beta (TGF-β) signaling pathway, and is positively correlated with the development of liver cirrhosis and vascular invasion of hepatocellular carcinoma (HCC). However, the role of LncRNA-ATB in hepatitis C virus (HCV)-related liver fibrosis remains largely unknown. In the present study, we confirmed a high expression level of LncRNA-ATB in the liver tissues and plasma samples of patients with HCV-related hepatic fibrosis, and the plasma level of LncRNA-ATB was significantly correlated with liver fibrosis stages. Furthermore, increased expression level of LncRNA-ATB was also present in activated hepatic stellate cells (HSCs), and knockdown of LncRNA-ATB inhibited the expression of alpha-smooth muscle actin (α-SMA) and alpha-1 type I collagen (Col1A1). LncRNA-ATB was found to share the common miRNA responsive element of miR-425-5p with TGF-β type II receptor (TGF-βRII) and SMAD2. Ectopic expression of LncRNA-ATB in HSCs could upregulate the protein expression of TGF-βRII and SMAD2 by inhibiting the endogenous miR-425-5p. Moreover, overexpression of miR-425-5p could partly abrogate the expression of TGF-βRII and SMAD2 induced by LncRNA-ATB. Hence, we conclude that LncRNA-ATB promotes HCV-induced liver fibrogenesis by activating HSCs and increasing collagen I production through competitively binding to miR-425-5p. LncRNA-ATB may be a novel diagnostic biomarker and a potential therapeutic target for HCV-related hepatic fibrosis.

Interleukin-23 (IL-23) and its downstream factor IL-17 are the key cytokines involved in immune and inflammatory response in chronic liver diseases. This study aimed to investigate the role and molecular mechanisms of the IL-23/Th17 axis in chronic hepatitis C virus (HCV) infection, and the efficacy of IL-23/Th17 modulation in response to anti-HCV therapy. Sixty-six HCV-infected patients and 20 healthy controls were enrolled. The patients received PegIFNa-2a and ribavirin therapy for at least 48 weeks. The plasma level of IL-23 and the number of IL-17A-, IFN-γ-, and IL-21-producing peripheral blood mononuclear cells (PBMCs) at baseline and 12, 24, and 48 weeks following treatment were determined. The mRNA level of Th17 immune-associated molecules in PBMCs was evaluated by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) following treatment with IL-23 agonist or antagonist. Our data showed that, compared to healthy controls, HCV-infected patients had an increased plasma level of IL-23 and increased frequencies of IL-17A- and IFN-γ-producing PBMCs, whereas the HCV patients exhibited a reduced number of IL-21-producing PBMCs. However, the baseline frequencies of IL-21-producing PBMCs were markedly higher in HCV patients who achieved rapid virological response (RVR) than those without RVR. Additionally, the mRNA expressions of IL-21, IFN-γ, myxovirus resistance protein A (MxA), and suppressor of cytokine signaling 3 (SOCS3) were significantly upregulated in PBMCs, while FoxP3 expression was suppressed by IL-23 agonist. Thus, the IL-23/Th17 axis plays an important role in development of chronic HCV infection and antiviral response. IL-23 may enhance the antiviral activity of interferon-based therapy by modulating the expression of Th17 cells-associated molecules in HCV-infected patients.

Nonalcoholic fibrosing steatohepatitis is a uniform process throughout nonalcoholic fatty liver disease (NAFLD). MicroRNAs (miRNAs) have been suggested to modulate cellular processes in liver diseases. However, the functional role of miRNAs in nonalcoholic fibrosing steatohepatitis is largely unclear. In this study, we systematically analyzed the hepatic miRNAs by microarray analysis in nonalcoholic fibrosing steatohepatitis in C57BL/6J mice induced by methionine-choline deficient (MCD) diet. We identified 19 up-regulated and 18 down-regulated miRNAs in liver with fibrosis. Among these dysregulated miRNAs, miR-146a-5p was the most significant down-regulated miRNA. Luciferase activity assay confirmed that Wnt1 and Wnt5a were both the target genes of miR-146a-5p. Hepatic miR-146a-5p was down-regulated in fibrosing steatohepatitis, but its target genes Wnt1 and Wnt5a and their consequent effectors α-SMA and Col-1 were significantly up-regulated. In addition, miR-146a-5p was downregulated, whilst Wnt1 and Wnt5a were up-regulated in the activated primary hepatic stellate cells (HSCs) compared to the quiescent primary HSCs. Overexpression of miR-146a-5p in HSCs inhibited HSC activation and proliferation, which concomitant with the decreased expressions of Wnt1, Wnt5a, α-SMA and Col-1. In conclusion, miR-146a-5p suppresses activation and proliferation of HSCs in the progress of nonalcoholic fibrosing steatohepatitis through targeting Wnt1 and Wnt5a and consequent effectors α-SMA and Col-1.

To explore the clinical application and related factors of FibroTouch in the diagnosis of liver fibrosis in patients with chronic liver disease through comparison of the specificity and sensitivity of FibroTouch and multi-parameter models, and to identify whether FibroTouch is a more accurate and safe method in diagnosis of liver fibrosis and evaluation of the therapeutic effect.A total of 190 patients with chronic liver disease were performed liver biopsy and underwent liver stiffness measurement (LSM) using FibroTouch in department of Traditional and Western Medical Hepatology, Third Hospital of Hebei Medical University from January 2014 to February 2015. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin (TBIL) were tested by enzymic method with automatic biochemistry analyzer. Blood platelet counts were detected by automatic blood cell analyzer. AST-to-PLT ratio index (APRI) and fibrosis index based on the 4 factor (FIB-4) were calculated. The diagnostic values of FibroTouch, APRI and FIB-4 for liver fibrosis degree were calculated and compared by receiver operating characteristic (ROC) curves. The related factors of LSM were analyzed by Spearman analysis.There was significant correlation between LSM and histological fibrosis (r=0.804, P=0.000). The area under ROC curve of LSM for S(≥2, S≥3 and S=4 was 0.894, 0.938 and 0.961, respectively, which was significantly higher than APRI (0.678, 0.698 and 0.658) and FIB-4 (0.765, 0.785 and 0.775). On Spearman analysis, LSM was positively correlated with age, ALT, AST, TBIL ((≥2×ULN) and the grade of liver inflammation (r=0.309, 0.558, 0.504, 0.492 and 0.532, respectively) but negatively with PLT (r=-0.444), (all P0.05).LSM is a convenient and reliable approach for diagnosis of liver fibrosis in patients with chronic liver disease. The sensitivity and specificity of Fibrotouch in diagnosis of hepatic fibrosis is superior to APRI and FIB-4, and age, high level ofALT, AST and TBIL (≥2×ULN) were independent predictors of LSM inaccuracy.

Nonalcoholic fibrosing steatohepatitis is a uniform process that occurs throughout nonalcoholic fatty liver disease (NAFLD). MicroRNAs (miRNAs) have been shown to be involved in the biological processes, but the role and molecular mechanism of miRNAs in NAFLD are not entirely clear. In this study, we observed a significant reduction in the expression of miR-130a-3p in livers of a mouse model with fibrosis induced by a methionine–choline-deficient diet, of NAFLD patients, and in activated hepatic stellate cells (HSCs). A dual-luciferase activity assay confirmed that transforming growth factor-beta receptors (TGFBRs) 1 and 2 were both the target genes of miR-130a-3p. The hepatic expression of TGFBR1 and TGFBR2 was significantly increased. Moreover, the overexpression of miR-130a-3p in HSCs inhibited HSC activation and proliferation, concomitant with the decreased expression of TGFBR1, TGFBR2, Smad2, Smad3, matrix metalloproteinase-2 (MMP-2), MMP-9, type I collagen (Col-1), and Col-4. In addition, the overexpression of miR-130a-3p promoted HSC apoptosis by inducing the expression of caspase-dependent apoptosis genes. Transfection with si-TGFBR1 and si-TGFBR2 revealed effects on HSC function that were consistent with those of miR-130a-3p. TGFBR1 and TGFBR2 rescued the miR-130a-3p-mediated reductions in the mRNA and protein expression levels of Smad2, Smad3, Col-1, and Col-4. In conclusion, our findings suggest that miR-130a-3p might play a critical role in negatively regulating HSC activation and proliferation in the progression of nonalcoholic fibrosing steatohepatitis by directly targeting TGFBR1 and TGFBR2 via the TGF-β/SMAD signaling pathway.

Good altitude performance of lubrication system ensures flying performance of the helicopter. Both engine and reducer need lubricating oil to cool themselves, to keep stable and decrease malfunction in flying tasks. In this article, a multi-factor coupling calculation method is put forward for altitude performance analysis of lubrication system in “Zhi X” main reducer system, taking into consideration of heat transfer and flow resistance characteristics of every component, off-design performance of the fan and dynamic characteristic of heat exchanger. Performance parameters of each component are calculated, such as temperature, pressure and flux. The results are in good agreement with numerical results of FM2. Then an analysis software for altitude performance of lubrication system is developed for “Zhi X” based on the multi-factor coupling calculation method, which is regarded as a scientific and practical tool for altitude performance prediction and integrated design of lubrication system in helicopter.Copyright © 2010 by ASME

Nacelle fire is seen as one of the most difficult to put out. To clarify the characteristics of fire spread in nacelle and determine the minimum usage of fire extinguishing agent, a numerical study is conducted to investigate fire activity in helicopter nacelle by analyzing the distribution of heat release rate, velocity vector field, temperature field and the distribution of fire extinguishing agent concentration with FDS (Fire Dynamics Simulator). Full scale experiment is implemented and three fire sources are set in the nacelle away from front fire wall of 1/4 position, 1/2 position and 3/4 position, respectively. Fire extinguishing system is designed by the results of fire spread. The distribution of fire extinguishing agent concentration is investigated from 6 s to 10 s. Ten scenarios are studied, which are established by changing mass flow rate or injection time. The results indicate that the fire spread in nacelle is affected by the position of inlet and fire source significantly under no ventilation condition. More attention should be paid on 1/4 position which locates at the opposite face of inlet. In order to improve the dependability of helicopter and reduce the waste of fire extinguishing agent, minimum usage of agent is obtained. Decreasing agent mass flow rate is propitious to improve reliability of fire extinguishing system when meets fire suppression requirement.