Pressure cross-over

Another eommon eombustion problem eoneerns the erossover tubes. Cross-over tubes are used in ean-annular eombustors to assure eombustion in all ehambers and to equalize pressure. Many times the flow of hot gases through the erossover tubes is inereased due to bloeked fuel nozzles, whieh ean lead to tube failures as shown in Figure 21-17. 

Figure 12-103C. In a compound pump, the gas is compressed in two stages. First, the gas is compressed in the larger low pressure section and then transferred through the cross-over and internal passageways to be compressed in the smaller, high pressure stage. (Used by permission Form 4114. Kinney Vacuum Division, Tuthill Corporation.)...

Small capacity pumps commonly referred to as "jockey" pumps are provided on a firewater system to compensate for small leakages and incidental usage without the main pump(s) startup. They are set to start 0.70 to 1.05 kg/sq. cm. (10 to 15 psi) above the start up pressure of main firewater pumps. In some cases a cross-over from the utility water system can be used in place of a jockey pump, however a check valve is installed to prevent drain down of the firewater by the utility water system. Jockey pumps do not require the... 

Irradiation of the 1,2,3-benzotrithiole 2-oxide (41) with a high-pressure mercury lamp afforded the corresponding 1-oxide (111) <93TL673>. This rearrangement, which was also observed for a number of related benzotrithiole 2-oxides, was shown to be an intramolecular process by cross-over experiments using 0-labeled materials. 

The most suitable wires for this purpose are pure lead, indium and gold. The Pb and In wires should be between 0.1 and 0.4 mm thick, the Au ca. 0.05 to 0.1 mm. Under presure, these metals are deformed plastically and adapt themselves to the contour of the joint. There will momentarily be the greatest pressure at the point at which the ends cross over and thus the greatest deformation will occur there until a uniform thickness is attained. If such a joint resists dismantling, it can usually be freed by heating it gently with a brush flame or hot air gun. 

Isomerization yields increase with decrease in incident wavelength. Thus it is possible that isomerization yields may increase at low pressures where vibrational relaxation would be slow. Thus it is especially dangerous to assume that all 1B2u molecules which do not emit cross over to the triplet state. More information on this point is badly needed. 

At low relative pressures p/p0 or thin adsorbate films, adsorption is expected to be dominated by the van der Waals attraction of the adsorbed molecules by the solid that falls off with the third power of the distance to the surface (FHH-regime, Eq. 3a). At higher relative pressures p/p0 or thick adsorbate films, the adsorbed amount N is expected to be determined by the surface tension y of the adsorbate vapor interface (CC-regime, Eq. 3b), because the corresponding surface potential falls off less rapidly with the first power of the distance to the surface, only. The cross-over length zcrit. between both regimes depends on the number density np of probe molecules in the liquid, the surface tension y, the van der Waals interaction parameter a as well as on the surface fractal dimension ds [100, 101] ... 

Kistiakowsky and Parmeter studied the benzene-sensitized isomerization of CTS-butene-2 at one pressure, viz., 0.047 mm. They found isomerization even at this low pressure, thus indicating that triplet-state benzene molecules are present in CeHe irradiated at this low pressure. They did not study the effect of pressure by the Cundall technique. They did, however, study the relative emission from benzene as a function of pressure at low pressures. By making the assumption supported within experimental error by the data of Ishikawa and Noyes that all absorbing molecules either emit or cross over to the triplet state, Kistiakowsky and Parmeter conclude that the rate of crossover is independent of collisions even at these low pressures. 

This conversion procedure must be attempted for the longitudinal as well as for the transverse transport. The results for p (7) in (TMTSFljPF at ambient pressure is given in Fig. 14 where a cross-over from a superlinear to a linear (or sublinear) power law temperature dependence is observed in the vicinity of 80 K. A detailed analysis based on the Fermi liquid theory shows that a law is apparently well satisfied below 50 K down to the vicinity of the spin density-wave transition where the resistivity is dominated by critical scattering effects [75]. 

---