In order to develop, for air fraetionation plantg (AFP), reliable expansion-compression machines (expanderscompressors) on supports lubricated by process gas, which do not require precise equipment for their construction, it is necessary to exclude not only oil lubrication units, but also the presence of oil in the plant to avoid fouling of the heat-and mass-transfer units with oil. When this is done, the mechanical efficiency of the unit increases significantly, which is especially important for expansion-compression machines where the retarding compressor stage is used for final compression of the expanded gas slre, am; the algorithm of plant control is simplified; a poss~ility appears for higher working rotor speed, which becomes necessary when plant efficiency dimini.e, hes and pressure and temperature rise before the expansion stage.In developing turboexpansion mac, hines (turboexpanders) on gas-lubricated supports for belimn liquefiers, virtually the

Channel diffusers (CD) were experimentally obtained for the first time in the investigation of multiple bladeless diffusers (BD). It is known that an indispensable element of the design of BD is a sudden narrowing of the steam at the outer formed by the so-called ledge [1]. The angle of the stream at the outlet from the BD is increased to values that are usually found in vaned diffusers (VD). An experimental investigation of the influence of the width of the ledge on the losses in the BD showed that the minimum of losses corresponds to the alternative of the diffuser without a ledge [2]. Such BD became later known as channel BD.It follows from Fig. 1 that the through-flow part of the CD is formed by three geometric elements: the nozzle (O-Or), of which there may be four to ten in dependence on the scale of the stage; the oblique section of the nozzle by the curved wall (Or-ed( which may also be regarded as volute; the radial gap between the CD and the rotor (ed-1).The total opening cross-sectional area of the orifice of the CD determining (together with the regime parameters) the flow rate of the working gas is calculated by the formula For: Znaorb a,where z n is the number of nozzles; aor is the height of the nozzle orifice; b a is the width of the diffuser.The mean geometric angle at the outlet from the volute, viz., at the inlet to the gap, i.e., on the circumference of the trailing edges of the vanes, can be found from the expression sin ~ed = (zn/2n) (aor/Rea) :where Red is the radius of the circle formed by the edges.The presented geometric relations of CD make it possible to evaluate the characteristic traits of the geometry of CD compared with VD that have the same total opening cross-sectional area of the orifice. The substantially smaller number of nozzles and the geometric angle %d = 5-9* in CD compared with VD (z n = 19-27; sea = 12-16") increase the width of the diffuser and the height of the nozzle orifice. The last is due to the fact that the number of nozzles was reduced more than the angle. It should also be noted that technologically the CD is considerably simpler than the VD.We investigated experimentally CD of different scale: small nonregulated diffusers with rotor diameter D 1 = 30-60 ram; medium nouregulated and regulated diffusers with D 1 = 30-60 ram; medium nonregulated and regulated diffusers with D l = 100-150 mm; large regulated diffusers with D t = 250 rnm. The investigations were carried out on test stands with static scavenging as part of the experimental ("hot") stages and as part of industrial ("cold") stages. The angular momentum of the stream behind the diffuser was measured with a trap wheel. Figure 2 presents the loss factors ~1, the angles of th~ stream ct t depending on the reduced speed his = Cls/Cerit of the channel and vaned diffusers of different scale (here Cerit is the critical speed, cls is the absolute speed of the isentropic stream at the entry to the rotor). Small CD with D 94 = 50 mm and For = For/Rot 2 have the number of nozzles z n = 6 which is optimal for the ...

A topical problem is the elaboration and testing of a method of calculating losses in elements of the through-flow part and stage of turbo-expansion engines as a whole, necessary for the prediction of the efficiency of the planned stage and for the optimization of its geometric and regime relations. This problem in engineering statement was solved by analytical and experimental methods at the AO Kriogenmash. The newly devised method of calculating losses was first: tested, element by element on stands, and was then integrated into the system of automated designing of turbo-expansion engines, and finally the calculated and experimental efficiencies were compared on the investigated industrial stages. The experiments were carried out with stages differing from each other in scale, level of initial pressure, the kind of gas, etc. The results lead to the conclusion that the method is objective and is of scientific and applied interest.Let us consider the main postulates of the method.Components of the Losses. By calculation, almost all the components of the hydraulic losses of the stage are checked: losses in friction and secondary losses in the channel of the diffuser (DF) consisting of a nozzle, the oblique edge, and a radial gap; losses in friction and secondary losses in the channel of the rotor (R) consisting of the channel itself and the oblique edge; losses of partialness in the R on account of detachment of the flow from the wall of the oblique edge of the DF; edge losses in the DF and R; impact losses at the inlet to the R if in the theoretical regime the angle of attack is nonzero; losses at outlet velocity in view of the useful effect of the end diffuser. The losses of power of the stage through disk friction and flow-off are also checked by calculation. The friction losses and the secondary losses in the channel of the nozzle, in the cbannel and the oblique edge of the R are examined by the unidimensional scheme of calculation, in the oblique edge of the DF and in the gap by the plane scheme (jet by je0. Besides that, the type of stage is specified: DF channel type; R radial-axial. According to the experimental data the hydraulic losses and the losses through control in the channel DF are smaller than in the vane DF; the efficiency of the stage with radial-axial R is higher than of the stage with radial R [3].Friction Losses. The calculation of friction losses in the through-flow part is based on Karman's integral equation for the boundary layer; the simplest nongradient alternative of the equation is used, which applies to flows with small pressure gradient, and the expression for calculating the local coefficient of friction losses [4] is known. Such a calculation scheme corresponds fully to flows with small pressure gradient in the oblique edge of the channel of the R. In the channel of the nozzle of the DF and in the channel of the R of the reactive stage, considerable negative pressure gradients act, and it is assumed that their influence on the flow and on the losses are taken into account discretel...