Showing papers on "Overpressure published in 1986"

Simplified vent sizing equations for emergency relief requirements in reactors and storage vessels

Abstract: Simplified vent sizing equations for emergency relief requirements in reaction kettles and storage vessels are obtained from analytical consideration. Venting modes include homogeneous-vessel venting, all-vacor venting, and all-liquid venting; energy sources due to runaway chemical reactions and external heating are treated separately. The resulting equations have been shown via numerical examples to yield good agreement with detailed computer simulations, both in terms of temperature and pressure histories during venting and in vent size predictions. These equations are generally applicable over a wide range of overpressure situations and reduce to the correct limit at no overpressure. The relative merit of allowing for overpressure in various venting modes can be demonstrated using these equations. Because of their simple forms, requiring only pertinent physical property and thermal data, these equations readily lend themselves to quick but accurate vent sizing predictions.

Static overpressure protection system for differential pressure transducer

Abstract: An improved differential pressure transducer is provided having static overpressure protection means. The overpressure protection means includes spring-loaded element being shiftable in response to an overpressure condition.

Dependence of Free-Field Impulse on the Decay Time of Energy Efflux for a Jet Flow.

Abstract: : Until now, the peak energy efflux at the jet exit was considered the significant parameter in a scaling approach to estimate the peak overpressure, time of arrival, and positive phase duration from guns and shock tubes. The resulting predictions for the peak overpressure, time of arrival were satisfactory but the positive phase duration prediction was poor. This predicted value of the positive phase duration is used with the peak overpressue prediction to obtain an estimate of an important quantity: the impulse. Here we investigate the characteristic exhaust decay time for the energy efflux at the jet exit as a possible additional significant parameter that might be used to improve predictions for the impulse. Numerical simulation was used to establish that the impulse value depends upon this parameter. Comparison between simulation and experiment is satisfactory. This additional parameter wa sused to correlate the available impulse data. It was determined that the additional parameter significantly improves the prediction capability of the scaling method for predicting impulse. An idealized wave form together with the predicted peak overpressure can be used to obtain an estimate of the positive phase duration. This approach yields less satisfactory agreement with the duration data but this fact is relatively unimportant since the impulse is the quantity of importance. Keywords: Gun muzzle blast; Shock waves; Blast wave scaling; Dimensional analysis.

Process for cleaning the dust filter of a silo

Abstract: Filter hoses in a dust filter of a silo are cleaned by blowing air into the hoses in a shocklike manner when there is a predetermined overpressure in the silo. At least one additional cleaning cycle occurs after the overpressure drops.

Fracture Propagation in Underwater Gas Pipelines

Abstract: Two full-scale ductile fracture propagation experiments on segments of line pipe pressurized with nitrogen gas have been conducted underwater at a depth of 40 ft (12 m) to evaluate the ductile fracture phenomenon in underwater pipelines. The pipes were 22-in. (559-mm) diameter and 42-in. (1067-mm) diameter. Fracture velocities were measured and arrest conditions were observed. The overpressure in the water surrounding the pipe resulting from the release of the compressed nitrogen gas contained in the pipe was measured in both experiments. The overpressure in the water reduces the stress in the pipe wall and thus slows down the fracture. In addition, the water surrounding the pipe appears to be more effective than soil backfill in producing a slower fracture velocity. Both of these effects suggest a greater tendency toward arrest for a pipeline underwater than would be the case for the same pipeline buried in soil onshore. Further verification of this effect is planned and a modified version of the existing model for predicting ductile fracture in buried pipelines will be developed for underwater pipelines.

Shock and Vibration Analysis of a Communication System Subject to Nuclear Blast

Abstract: If a mobile, transportable, command, control, and communications system is expected to survive a near field nuclear explosion, the design must include protection of the equipment from the overpressure shock The response of the equipment in a shelter subjected to nuclear overpressure for nominal overpressures of 2 psi and 4 psi has been simulated and shown to be much greater than the response to the shock and vibration environment which is normally specified for electronics--even military equipment Including a shock isolation system in the simulation demonstrates that such an isolation system can attenuate the shock to more acceptable levels Methods and tools are discussed which allow the simulation of the response to overpressure and the design of the isolation system

Numerical simulation of an ICF target explosion in a stratified gas atmosphere

Abstract: Two-dimensional radiation hydrodynamic simulations of a light ion fusion target generated microfireball in a stratified gas atmosphere have been performed. The target location in a two region cavity was varied with the intent to reduce the overpressure on the diodes at the walls of a target chamber with a single cavity gas. Helium and nitrogen at 15 torr were used as the cavity gases; target explosions of 200 and 800 MJ were investigated. It was found that placing the target in a helium region surrounded by nitrogen could reduce the overpressure by a factor of 2 when compared with a single gas cavity of nitrogen. The surface heat flux was also reduced from a pure helium gas cavity.

Response of SDF Systems to Extreme Overpressure

Abstract: Charts are provided for the rapid estimation of the response of an elastoplastic single-degree-of-freedom system to a decaying exponential load. The integral of the load was equated to the overpressure impulse from either the HULL code or the Speicher-Brode representation of blast wave overpressures. Plots were thus derived of the scaled duration and of the exponential characteristic parameter as a function of overpressure. Variations in both positive overpressure impulse and positive phase duration are well within the overpressure uncertainty for the scaled heights-of-burst of interest over the pressure range considered. A parametric response chart of the system is provided, which covers a very wide range of displacements, fundamental periods, and loading pressures. The chart is a graph of the results of the solution of 750 individual cases using the Newmark beta method of numerical integration.

Blast wave propagation in air from a gaseous charge

Abstract: In the point explosion problem it is assumed that an instantaneous release of finite energy causing shock wave propagation in the ambient gas occurs at a space point. The results of the solution of the problem of such blasts are contained in [1–4]. This point model is applied for the determination of shock wave parameters when the initial pressure in a sphere of finite radius exceeds the ambient air pressure by 2–3 orders of magnitude. The possibility of such a flow simulation at a certain distance from the charge is shown in papers [4, 5] as applied to the blast of a charge of condensed explosive and in [6, 8] as applied to the expansion of a finite volume of strongly compressed hot gas. In certain practical problems the initial pressure in a volume of finite dimensions exceeds atmospheric pressure by a factor 10–15 only. Such cases arise, for example, in the detonation of gaseous fuel-air mixtures. The present paper considers the problem of shock wave propagation in air, caused by explosion of gaseous charge of spherical or cylindrical shape. A numerical solution is obtained in a range of values of the specific energy of the charge characteristic for fuel-air detonation mixtures by means of the method of characteristics without secondary shock wave separation. The influence of the initial conditions of the gas charge explosion (specific energy, nature of initiation, and others) is investigated and compared with the point case with respect to the pressure difference across the shock wave and the positive overpressure pulse.