This type of hydraulics nevertheless presents some disadvantages<\/strong>. The principle of operation requires only very slightly curved impeller blades to reduce the transverse separation of the two phases with very different densities. Consequently, these blades are very long to achieve an acceptable pressure coefficient. By virtue of their constitution, these blades generate high viscous losses<\/strong>, greatly penalizing the efficiency<\/strong> (monophasic and consequently diphasic). The second disadvantage concerns the two-phase efficacy<\/strong> which, although it is higher than the one of a conventional single-phase machine, tends to decrease sharply when the difference in densities is pronounced<\/strong>. However, it should be noted that the hub of the impeller presents a concave curved shape (vertex directed towards the centre of the impeller). This configuration has the advantage of counteracting the residual centrifugal force and somewhat favouring the mixing of the phases up to a gas fraction of the order of 1 or 2. This gas fraction is expressed by the ratio of the volume flow rates of the gas and the liquid phases also designated by GLR for Gaz Liquid Ratio. Beyond this value, the phase separation increases, causing high energy losses. Below are some references:<\/p>\n\n\n\n S.Y. Li, X.P. Jiang, Jiambo Zhang – The two-phase flow analysis of helico-axial oil-gas multiphase pump for offshore oil fields <\/strong> _https:\/\/images.app.goo.gl\/ADzadNKgDQvMQLj87<\/a><\/p>\n\n\n\n This helico axial hydraulic cell can be designated by the \u201cFirst generation cell\u201d<\/strong>. It should be emphasized that this cell is strictly axial (cylindrical) on its external part.<\/p>\n\n\n\n This section will be completed during 2020 with a text describing the operation and the dimensioning method of a helico axial impeller (Poseidon or similar) for two-phase compression.<\/em><\/p>\n\n\n\n Attempts\nhave been made, in the past, to increase the compression ratio of a\ntwo-phase machine using semi-radial hydraulic cells while keeping the\nhelical principle for the impeller. This type of machine did not meet\nexpectations.<\/p>\n\n\n\n Why\ndo these two types of two-phase machines malfunction when the gas\nrate is intermediate (fully diphasic) ? The reasons are as follows:<\/p>\n\n\n\n –\nin a strictly helico axial impeller, the liquid phase lags behind the\ngas phase due to the a difference in wall friction between the two\nphases (phase velocity determined by viscosity and density). The same\nphenomenon is observed in an axial impeller or in a horizontal duct.<\/p>\n\n\n\n –\nIn a helico axial semi-radial impeller, the liquid phase is ahead of\nthe gas phase due to the application of a large force (of centrifugal\norigin) exerted from the inlet to the outlet of the impeller. This\nforce is all the more important as the external part of the impeller\n(the cover or the casing) is inclined (diameter at the outlet\nsignificantly greater than that of the inlet). The same phenomenon is\nobserved in a radial impeller or any centrifugal element.<\/p>\n\n\n\n It is based on these observations that a helico \u201cquasi-axial\u201d impeller was developed during the 2010s. The term \u201cquasi-axial\u201d is used to suggest a slight inclination of the external part of the impeller (cover or casing). This external profile is designed to control the liquid velocity so as to keep it as close as possible to that of the gas phase<\/strong>. The principle is as follows: the combination of centrifugal and centripetal forces (Coriolis) results in a force directed in the centrifugal direction (described in the attached document). A radial force is exerted on the two phases of the mixture with a tangential component (along the external profile) which depends on the densities of the two phases and on the angle of the external profile.<\/p>\n\n\n\n The\nexternal profile presents two curved shapes. In direction of the\nflow, a first concave section (apex directed towards the centre of\nthe impeller) aimed at accelerating the liquid phase and a second\nconvex one (apex directed towards the outside of the impeller) aimed\nat maintaining the velocity of the liquid phase as close as possible\nto the one of the gas phase. Without going into detail, this equality\nof velocities is obtained by balancing the friction forces and the\ncomponent of the residual centrifugal force applied along the\nexternal profile.<\/p>\n\n\n\n Defining the interfacial slip as the difference in velocities between the liquid and gas phases, one can designate this impeller by \u201cInterfacial Slip Control\u201d (ISC) or “Phase Velocity Control” (PVC). This helico \u201cquasi-axial\u201d hydraulic cell can also be designated by a \u201cSecond generation cell\u201d<\/strong>.<\/p>\n\n\n\n Summary for New Helico Radio Axial Impeller with “Phase Velocity Control” – <\/p>\n\n\n\n Patent for New Helico Radio Axial Impeller with “Phase Velocity Control” – <\/p>\n\n\n\n Patent figures for New Helico Radio Axial Impeller with “Phase Velocity Control” – <\/p>\n\n\n\n Comparison between HRA hydraulics – First and second generation, without and with “Phase Velocity Control”<\/p>\n\n\n\n
https:\/\/www.researchgate.net\/publication\/326699320_The_two-phase_flow_analysis_of_helico-axial_oil-gas_multiphase_pump_for_offshore_oil_fields<\/a> Falcimaigne, Brac, Charron, Pagnier, Vilagines – Multiphase Pumping: Achievements and perspectives <\/strong>
https:\/\/pdfs.semanticscholar.org\/7bc6\/84d33f0a8ce107a028cd7f6a1d91e87a8517.pdf<\/a>
J. Falcimaigne, S Decarre – <\/strong>Multiphase Production: Pipeline Transport, Pumping and Metering
https:\/\/books.google.fr\/books?<\/a> <\/p>\n\n\n\n![\"Poseidon](\"http:\/\/yvcharron.com\/wp-content\/uploads\/2020\/12\/Poseidon-pump-One-Petro.jpg\")
<\/figure><\/div>\n\n\n\nAttempts to use semi radial designs<\/h2>\n\n\n\n
Liquid phase velocity control – New design<\/h2>\n\n\n\n
![\"Longitudinal](\"http:\/\/yvcharron.com\/wp-content\/uploads\/2020\/03\/PVC-Impeller_2nd-generation.png\")
<\/figure><\/div>\n\n\n\n![\"Several](\"http:\/\/yvcharron.com\/wp-content\/uploads\/2020\/03\/pdf-4.png\")
<\/figure><\/div>\n\n\n\n