Varying Chamber Pressure Research Articles

On the formation of calderas during ignimbrite eruptions

Many large calderas result from the eruption of substantial volumes (tens or hundreds of km3) of silicic pyroclastics. Such events often begin with an airfall phase and progress to the generation of voluminous ignimbrites1–3. We propose here that many such eruptions involve two well-defined stages, based on a simple analysis of magma chamber pressure variations during an eruption. The first stage begins when an overpressured magma chamber fractures the country rock and forms a conduit to the surface. The chamber pressure decreases rapidly to values less than lithostatic pressure. We show that only small to moderate volumes of magma, representing a small fraction of the total chamber, can be erupted during this stage. In the second stage, caldera collapse results from a further decrease in magma pressure, which causes the chamber roof to fracture catastrophically and deform. Subsidence of the roof attempts to re-establish lithostatic pressures within the chamber and can drive substantial volumes of magma to the surface. Geological relationships in pyroclastic deposits associated with large caldera eruptions provide independent evidence for this model.

A comment upon the correlation of inductively coupled plasma emission signal variations with spray chamber pressure variations

A comment upon the correlation of inductively coupled plasma emission signal variations with spray chamber pressure variations

Generalized response of chemiluminescence analyzers

The mass flow and chemical kinetic equations for a gaseous chemiluminescence (CL) analyzer are formulated and solved. The resultant equation can be used to predict the absolute response of the analyzer as a function of the sample flow rate, the sample gas pressure, the chamber pressure, the chamber volume, the mass flow rate and mole fraction of the reagent gas, and the rate constants of the relevant chemical processes. Thus, the equation allows optimization of these parameters. It is shown that for varying sample pressure the analyzer can be used to measure either concentration or mole fraction and that interfering reactions can sometimes be discriminated against by chamber pressure variation. The equations apply equally well to a flowing-liquid-phase CL analyzer, if the chemical mechanism considered is appropriate.

Performance of Plug-Type Rocket Exhaust Nozzles

The physical characteristics of a plug nozzle are described and compared with a conventional converging-diverging nozzle. The mathematical analysis of the aerodynamic performance of a plug nozzle is outlined, including the Prandtl-Meyer corner expansion of the flowing gas. The advantages of the plug nozzle in terms of superior performance at lower than design pressure ratio, smaller physical size and aerodynamic thrust vector control are described. A brief description is given of how these advantages can be utilized in liquid propellant rocket engines. Application of plug nozzles for solid propellant rocket engines is discussed primarily from the viewpoint of using the plug's movement to adjust for chamber pressure variation, to control thrust magnitude and direction and to control total impulse.