Total pressure

About: Total pressure is a research topic. Over the lifetime, 5199 publications have been published within this topic receiving 66658 citations.

Infrared Transmission of Synthetic Atmospheres.* II. Absorption by Carbon Dioxide

Abstract: The total absorption ∫Aνdν has been determined for the CO2 bands at 15, 5.2, 4.8, 4.3, 2.7, 2.0, 1.6, and 1.4μ under stimulated atmospheric conditions. The absorber concentrations w ranged from 1 to 1000 atmos cm of CO2 for the strong bands and from 100 to 8600 atmos cm for the weak bands. Nitrogen was added to give total pressures ranging up to atmospheric; the pressure effects of oxygen were found to be similar to those of nitrogen. The observed data can be satisfactorily represented by two types of empirical relations.(1)For small values of total absorption,∫Aνdν=cw12(P+p)k;(2)For large values of total absorption,∫Aνdν=C+D Logw+K Log(P+p),where w is the CO2 absorber concentration, p is the CO2 partial pressure, and P is the total pressure. Values of the constants c, k, C, D, and K are given for each region of characteristic absorption. The present results are compared with those obtained in earlier studies. The use of the empirical relations in calculating atmospheric absorption is discussed.

On the role of pressure and flow perturbations around dipolarizing flux bundles

Abstract: [1] As a dipolarizing flux bundle (DFB) moves earthward, it creates pressure and flow perturbations. These perturbations may play a significant role in controlling DFB motion and generating field-aligned currents (FACs) which render the DFB a “wedgelet”, a traveling building block of the substorm current wedge. To investigate this hypothesis, we use DFB observations from the Time History of Events and Macroscale Interactions during Substorms mission to reconstruct the spatial profiles of the thermal and total (thermal plus magnetic) pressures and of the plasma flow near the DFB. The total pressure reaches maximum inside the dipolarization front (DF, the leading edge of the DFB). The resultant pressure gradient force pushes ambient plasma in the direction normal to the front and exerts a gradient force density of ~0.15 nPa/RE against the DFB motion. The thermal pressure in the equatorial plane is strongest immediately ahead of the DFB's leading point; it decreases with distance from that peak: toward the ambient plasma, toward the DFB interior, and toward the DFB flanks. Combining our estimate of the flux tube volume distortion with the measured equatorial thermal pressure distribution, we obtain a region-1-sense FAC inside the DF layer and region-2-sense FAC in the ~1 RE thick region immediately ahead of it. This system of FACs is indeed consistent with a wedgelet.

Variable gas volume flow measuring and control methods and apparatus

Abstract: A method and apparatus for measuring gas flow volume in a system (of the kind in which the amount of gas flowing in a duct can vary in response to the variation of area of a variable area orifice in a duct and/or in response to changes in the total pressure of the gas upstream of the orifice) references the total pressure upstream of the orifice to the static pressure downstream of the orifice to produce a first signal representative of the differential pressure between the total pressure upstream of the orifice and the static pressure downstream of the orifice. The method and apparatus produce a second signal corresponding to the area of the opening in the orifice. The first and second signals are supplied to a gas flow volume database which is correlated to the sensors and to the orifice in the duct. The gas flow volume occurring in the duct at the first and second signals is read out from the database.

Experiments and Simulations of n-Heptane Spray Auto-Ignition in a Closed Combustion Chamber at Diesel Engine Conditions

Abstract: Auto-igniting n-heptane sprays have been studied experimentally in a high pressure, high temperature constant volume combustion chamber with optical access. Ignition delay and the total pressure increase due to combustion are highly repeatable whereas the ignition location shows substantial fluctuations. Simulations have subsequently been performed by means of a first-order fully elliptic Conditional Moment Closure (CMC) code. Overall, the simulations are in good agreement with the experiment in terms of spray evolution, ignition delay and the pressure development. The sensitivity of the predictions with respect to the measured initial conditions, the spray modelling options as well as the chemical mechanism employed have been analysed. Strong sensitivity on the chemical mechanism and to the initial temperature on the predicted ignition delay is reported. The primary atomisation model did not affect strongly the predicted auto-ignition time, but a strong influence was found on the ignition location prediction.