The article considers the calculation of the flow of a viscous incompressible fluid in piston seals of piston hybrid power machines. The most widely used and effective seals are considered: a smooth gap seal and a step-type gap seal, and—based on the references analyses—the initial boundary conditions for their calculation are determined. The laminar and turbulent flows in gap seals are calculated based on the well-known analytical relationships, experimental studies and flow models, including the k-ε, Menter’s Shear StressTransport (SST) and Reynolds Stress (RSM) turbulence models. The effectiveness of using each model to determine average velocities, flow rates, and velocity plots in the cross section of a gap seal, as well as the adequacy of the description of known physical laws, is estimated. The results proved that the RSM turbulence model is better for the gap seals of different types under different modes of motion.
The thermodynamic and dynamic analysis of working processes and acting forces in single-stage reciprocating compressors and pumps has been performed. It has been established that, despite the general tendency to increase the crankshaft velocity and the discharge pressure of the compressible gas and dropping liquid in reciprocating single-stage compressors and pumps, there are their optimal values, which are determined on the basis of the maximum values of the supply coefficient, indicator, volumetric and total efficiency. It is shown that these values also have limits, bounded by the oil flash point (for reciprocating compressors) and permissible stresses in the parts and assemblies of the drive mechanism (for reciprocating compressors and pumps). It was found out that for a reciprocating hybrid power machine with regenerative heat exchange, the crankshaft velocity could be taken equal to 300...700 rounds per min-1, and the discharge pressure of the compressible gas and dropping liquid is 0.2...1.5 MPa.
The article discusses the existing methods of cooling reciprocating compressors, where special attention is paid to liquid systems in which the motion of the coolant is carried out not from an external pump, but due to fluctuations in gas pressure or rarefaction. An analysis of the designs of pumpless cooling systems is carried out, advantages and disadvantages are identified, directions for their further improvement are identified.
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