Numerical Simulation of the Deflagration to Detonation Transition in a Tube with Repeated Obstacles: Experimental Scale Simulation Using the Artificial Thickened Flame Method

The Artificial Thickened Flame (ATF) method, which involves artificially increasing the flame thickness so as to simulate with a coarse grid resolution, is applied to reduce the computational cost of predicting the Deflagration to Detonation Transition (DDT) in a tube with repeated obstacles. While simulation results depended on the parameter N (the number of grid points in laminar flame thickness), it was found that N values of more than 10 may be excessive. The results show that the chosen simulation method predicts the flame speed as compared to a reference experiment and captures the detail of the strong ignitions near the corner between the obstacle and the sidewall. The present simulation also captures the wrinkle flame front structure during the acceleration of flame.

APPLICATION OF WC GRAINS BY DEPOSITION BRAZING

The article describes problems of hard depositional brazing of wolfram-carbide grains in various matrixes. Especially iron and nickel base matrix on base material from constructional carbon steel. The experimental part was brazed by oxyacetylene flame (method 912 according to EN ISO 4063). The major goals of the experiment were to describe the technological procedure of hard depositional brazing of this specific part. Consequently, were proved wolfram-carbide deposit on two test coupons. These test coupons were metallographically and qualitatively evaluated. The advantage of wolfram-carbide depositional brazing is a service life of deposit, that could be multiple higher, than standard weld deposit with carbon, chromium and vanadium filler material. The advantage is also costly because this kind of braze is cheaper than hard surfacing filler material. This specific application of the wolfram-carbide layer is one of the hardest coatings that could be by flame brazing technology performed. Usage of this application is for example in the mining, woodcutting industry, where it is necessary to improve abrasion and resistance, service life, and guaranteed durability or hardness for cutting tools.

Improvement of the Method for Restoring the Bearing Supports of Steel Crankshaft

In the science of car repair, the problem of restoring worn-out crankshafts is very relevant. The engineering solutions proposed in the article will provide an increase in the technical and economic indicators of repair: an increase in the quality of coating by a gas-flame method with a finishing non-abrasive antifriction treatment. At the same time, the engineering solution consisting in the formation of one groove on each journal of the crankshaft, brazing of a copper wire, followed by flame spraying of a coating, sealed by a disk, and grinding of the journals (the bearing supports), provides a non-wear effect. So, thanks to the coil of copper wire, the resource of the crankshaft increases and the cost of repaired crankshafts are reduced in comparison with new ones.

Pembuatan Teskit Boraks dalam Upaya Efisiensi Penggunaan Bahan dan Alat Laboratorium

Borax is a carcinogenic compound which is dangerous to the body. The flame method is one of the qualitative laboratory testing that usually used to determine the Borax compound in food. The method not only needs H2SO4, methanol, furnace equipment which is prices, but also needs long time because of the graying process. The research aims to make a simple borax test kit (simple method) by extracting anthocyanin substances on the skin of purple sweet potatoes and testing the borax compound in food samples. Materials and tools used are purple sweet potato skin, 96% ethanol, filter paper, knives, cutting boards, measuring cups, beaker glass, food scales and petri dishes. The results of the borax test kit that have been made are then tested using the borax standard as the gold standard and it showed that there was color changing of the test kit, i.e from pink to blue. The borax test kit was also tested on four food samples that possibly contained borax, i.e gendar crackers, white tofu, meatballs and noodles. Gendar crackers was the only food sample that contain borax. Therefore, it was concluded that the borax test kit made from filter paper containing anthocyanin can be used as an alternative tool in qualitatively testing of borax in food

Results of the experimental bits bench test, equipped with the compound built-up layers

The article shows the results of performance laboratory studies of compound built-up layers, as well as benches of the pilot tests of the drilling bit rolling cutters, equipped on the bit gage surface of the compound built-up layer; the hardening layers were located along the gage teeth contour. The cast tungsten carbide building-up welding on experimental bits was carried out using a gas-flame method. The induction method of building-up welding was implemented on the rolling cutters of the serial bits. The article shows the results of comparative indicators of serial and experimental bits when their processing on the bench. It was found that experimental bits were more efficient than the serial ones. The estimation of the performance laboratory tests results was confirmed by tests on the bench under pilot conditions of the rolling cutter bits drilling, equipped on the bit gage surface by the compound built-up layer.