High-Frequency Oscillatory Combustion in Tubular Flame Burners(Thermal Engineering)

High-frequency oscillatory combustion in tubular flame burners has been experimentally investigated using two prototype burners of 1MW and 2MW. Oscillatory combustion regions have been mapped in the plane of equivalence ratio and air flow rate, and pressures fluctuations also have been recorded. Results show that large-amplitude, high-frequency oscillatory combustion occurs for near stoichiometric mixtures and when the mean axial velocity exceeds about 5m/s. With increasing the air flow rate, the oscillatory combustion region gradually expands on both lean and rich sides. According to FFT analyses, the peak frequencies during the oscillatory combustion exceed 1000Hz. A simple analysis shows that these high frequencies cannot be explained on the basis of the Helmholtz resonator, or attributed to the axial mode of acoustic instability of the burner tube. These high frequencies can be explained on the basis of coupling of tangential and radial modes of acoustic instability of the burner tubes. Just before the onset of the intense oscillatory combustion, the fundamental tangential mode, which is of asymmetry, appears, and during the subsequent intense oscillatory combustion, higher radial modes appear coupled with the asymmetric and symmetric tangential modes. Since the first asymmetric tangential mode of acoustic instability seems to trigger the intense, high-frequency oscillatory combustion, it is suggested to design the burner as symmetric as possible, and in addition, to make the flame as round as possible

Clinicopathologic Characteristics of Epstein–Barr Virus-Associated Gastric Cancer Over the Past Decade in Japan

: Epstein–Barr virus (EBV) is a ubiquitous human herpes virus, but related with several types of malignancies. Among EBV-related malignancies, EBV-associated gastric carcinoma (EBVaGC) has the largest patient’s number. We screened for EBV infection in 1067 GC lesions of 1132 patients who underwent surgical resection from 2007 to 2017 in Japan and examined clinicopathological features of EBVaGC. EBV infection was detected by in situ hybridization with EBV-encoded small RNA 1(EBER-1 ISH). EBV was infected in 80 GC lesions (7.1%). Mean age was significantly lower in patients with EBVaGC than with EBV-negative GC. EBVaGC was more frequent in men than in women. EBVaGC was found twice as frequent in the upper or middle stomach as in the lower stomach. Early EBVaGC was more frequent, and submucosally invaded cases were dominant. The presence of lymphatic vessel invasion was less in EBVaGC, but frequency of lymph node metastasis was similar. Carcinoma with lymphoid stroma (CLS) was found in 3.8% (43/1132) of all lesions with 60.5% of EBV positivity. The synchronous or metachronous multiple GC was frequent in EBVaGC. We clarified clinicopathologic characteristics of EBVaGC over the past decade in Japan. EBV infection should be examined in gastric cancer cases showing these characteristics

PIV Measurement and Turbulence Scale in Turbulent Combustion

We have investigated a turbulent combustion by PIV (Particle Image Velocimetry) technique. Comparing with LDV data, the validity of PIV measurement has been confirmed. Especially, the conditions of sampling number and spatial resolution have been revealed to obtain reliable data by PIV. Based on the velocity fields in cold flow and combustion, the interaction between flame and flow has been discussed. It is observed that the flow field is changed by combustion and the turbulence is reduced. For determining statistic quantities such as mean velocity and rms of velocity fluctuation, the sampling number of 1000 is needed. Moreover, the velocity correlation coefficient is evaluated to obtain the integral length scale of the flow. For both cold flow and combustion, the estimated scale by PIV is very close to that by LDV based on the assumption of Taylor's hypothesis. Resultantly, the special resolution in this study is about 6 times smaller than the integral length scale