Overpressure

About: Overpressure is a research topic. Over the lifetime, 3236 publications have been published within this topic receiving 34648 citations.

A Loudness Calculation Procedure Applied to Shaped Sonic Booms

Abstract: The economic viability of a supersonic commercial transport airplane would be much enhanced if it could fly supersonically over land Efforts to design an airplane to produce a minimized sonic boom at the ground require knowledge of the impact of sonic booms on people Loudness, being a fundamental and well-understood characteristic of human hearing, was chosen as a means of quantifying the magnitude of sonic boom impact on people This paper describes in detail a procedure that can be used to calculate the loudness of sonic booms The procedure is applied to a wide range of sonic booms, both classical N-waves and a variety of other shapes of booms The loudness of N-waves is controlled by overpressure and the associated rise time The loudness of shaped booms is highly dependent on the characteristics of the initial shock A comparison of the calculated loudness values indicates that shaped booms may have significantly reduced loudness relative to N-waves having the same peak overpressure This result implies that a supersonic transport designed to yield minimized sonic booms may be substantially more acceptable than an unconstrained design

Hierarchies of overpressure retardation of organic matter maturation: Case studies from petroleum basins in China

Abstract: The effects of overpressure on different aspects of organic matter maturation have been examined in three basins using multiple parameters. Overpressure in the Yinggehai Basin has retarded kerogen maturation, hydrocarbon generation, and thermal cracking of long-chain normal hydrocarbons, as well as evolution of isoprenoid hydrocarbons. Overpressure in the Dongpu depression, Bohai Bay Basin, seems to have retarded the maturation of bulk kerogens reflected by Rock-Eval Tmax, the thermal cracking of long-chain normal hydrocarbons, and the evolution of isoprenoid hydrocarbons, but seems to have had no detectable effects on vitrinite reflectance. Overpressure in the Qiongdongnan Basin has had no detectable retardation effects on all aspects of organic matter maturation. The observed phenomena suggest differential retardation of organic matter maturation (that is, different organic matter maturation reactions and different maturity parameters have been retarded by overpressure to different degrees in the same overpressured system) and four hierarchies of overpressure retardation. Hierarchy I retardation is defined as the state where the overpressure has retarded all aspects of organic matter maturation and is proposed to have been caused by the combination of high formation pressure and excess pressure, a high-water/organic matter ratio, and strong retention of reaction products in an early-developed, strong, persistent overpressured system. Hierarchy II retardation refers to the case in which all aspects of organic matter maturation except the maturation of hydrogen-poor kerogens, especially vitrinite, have been retarded and seem to have been caused by early-developed, moderate to strong, persistent overpressure. Hierarchy III retardation refers to the situation where overpressure has retarded only the thermal cracking of liquid hydrocarbons, but has had no detectable effect on the maturation of both hydrogen-rich and hydrogen-poor kerogens, and is proposed to have been caused by moderate to strong, persistent overpressures that began to develop around peak oil generation. Hierarchy IV retardation is defined as the situation where overpressure has had no detectable retardation on all aspects of organic matter maturation and may have been caused by cases wherein the overpressure developed too late, the intensity of the overpressure was too low, the duration of the overpressure was too short, or overpressured fluids had been expelled frequently. Resulting from both the diversities of organic matter maturation reactions and the complexities of overpressure generation and development, the hierarchies of overpressure retardation in different basins may be quite different, and it is necessary to use multiple parameters to understand the evolution of the petroleum systems in overpressured basins.

Blast overpressures from medium scale BLEVE tests

Abstract: The measured blast overpressures from recent tests involving boiling liquid expanding vapour explosions (BLEVE) has been studied The blast data came from tests where 04 and 2 m 3 ASME code propane tanks were exposed to torch and pool fires In total almost 60 tanks were tested, and of these nearly 20 resulted in catastrophic failures and BLEVEs Both single and two-step BLEVEs were observed in these tests This paper presents an analysis of the blast overpressures created by these BLEVEs In addition, the blast overpressures from a recent full scale fire test of a rail tank car is included in the analysis The results suggest that the liquid energy content did not contribute to the shock overpressures in the near or far field The liquid flashing and expansion does produce a local overpressure by dynamic pressure effects but it does not appear to produce a shock wave The shock overpressures could be estimated from the vapour energy alone for all the tests considered This was true for liquid temperatures at failure that were below, at and above the atmospheric superheat limit for propane Data suggests that the two step type BLEVE produces the strongest overpressure The authors give their ideas for this observation The results shown here add some limited evidence to support previous researchers claims that the liquid flashing process is too slow to generate a shock It suggests that liquid temperatures at or above the Tsl do not change this The expansion of the flashing liquid contributes to other hazards such as projectiles, and close in dynamic pressure effects Of course BLEVE releases in enclosed spaces such as tunnels or buildings have different hazards