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  1. Abstract This is a study of the suitability of preheat flame electrical resistance as a potential method for measuring the standoff distance an oxyfuel cutting torch and a work piece. Careful scrutiny of forty-seven individual experiments demonstrate that when cut quality is good, there is a linear repeatable relationship between the two with uncertainty about ±0.3 mm (0.015 in.). As the cut quality degrades, the formation of top-edge dross reduces the electrical path length in the flame, and momentary reduction in the reaction rate in the kerf reduces the free electrons in the flame, causing increases in flame resistance. In these conditions, measurement uncertainty reduces to ±1 mm (0.040 in.) or worse.
    Free, publicly-accessible full text available July 1, 2023
  2. Abstract Fuel efficiency becomes very important for new vehicles. Therefore, improving the aerodynamics of tires has started to receive increasing interest. While the experimental approaches are time-consuming and costly, numerical methods have been employed to investigate the air flow around tires. Rotating boundary and contact patch are important challenges in the modeling of tire aerodynamics. Therefore, majority of the current modeling approaches are simplified by neglecting the tire deformation and contact patch. In this study, a baseline computational fluid dynamics (CFD) model is created for a tire with contact patch. To generate mesh efficiently, a hybrid mesh, which combines hex elements and polyhedral elements, is used. Then, three modeling approaches (rotating wall, multiple reference frame, and sliding mesh) are compared for the modeling of tire rotation. Additionally, three different tire designs are investigated, including smooth tire, grooved tire, and grooved tire with open rim. The predicted results of the baseline model agree well with the measured data. Additionally, the hybrid mesh shows to be efficient and to generate accurate results. The CFD model tends to overpredict the drag of a rotating tire with contact patch. Sliding mesh approach generated more accurate predictions than the rotating wall and multiple reference framemore »approaches. For different tire designs, tire with open rim has the highest drag. It is believed that the methodology presented in this study will help in designing new tires with high aerodynamic performance.« less
  3. This is a study of the suitability of preheat flame electrical resistance as a potential method for measuring the standoff distance an oxyfuel cutting torch and a work piece. Careful scrutiny of forty seven (47) individual experiments demonstrate that when cut quality is good, there is a linear repeatable relationship between the two with uncertainty about ± .3mm (.015in). As the cut quality degrades, the formation of top-edge dross reduces the electrical path length in the flame, and momentary reduction in the reaction rate in the kerf reduces the free electrons in the flame, causing rises in flame resistance. In these conditions, measurement uncertainty reduces to ± 1mm (.040in) or worse.
  4. Abstract

    This paper presents a computational model to study ion and electron transportation and current-voltage characteristics inside a methane-oxygen flame. A commercial software is used to develop the model by splitting the simulation into the combustion and electrochemical transportation parts. A laboratory experiment is used to compare the results from the model. The initial and boundary conditions represented in the model are similar to the experimental conditions in the laboratory experiment.

    In the combustion part, the general GRI3.0 mechanism plus three additional ionization reactions are applied and results are then used as input into the electrochemical transportation part. A particular inspection line is created to analyze the results of the electrochemical transportation part. Ion, electron number density, and current density are studied along the interval from −40V to 40V electric potential. The ions are heavier and more difficult to move than electrons. The results show that at both torch and work surfaces charged sheaths are formed and cause three different regions of current-voltage relations.