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Purpose The aim of this study is to identify key factors limiting efficiency of pumped heat energy storage systems and determine some general features of transient behavior of solid state, sensible heat storages. Moreover, it aimed at establishing a feasible approach to transient conjugate heat transfer (CHT) analyses for such applications. Design/methodology/approach A zero-dimensional analytical model is used to determine the system efficiency sensitivity to efficiency of its components. Analysis of argon gas flow in an exemplary configuration of layered bed thermal energy storage is presented. The analysis incorporates a unsteady reynolds averaged navier stokes model with conjugate heat transfer between gas and solid storage core. Findings It is established that exergetic efficiency of the heat storage is one of the key factors for the system’s overall performance. Three full cycles of storage charging and discharging having 17 h physical time in total are simulated, with calculation of exergetic efficiency for each of the cycles. From standpoint of the system efficiency, it is concluded that the presented heat storage kind has limited exergetic efficiency because of severe temperature drop at the solid–fluid interface in comparison to granular kind of heat storage devices. From the methodological standpoint, it is concluded that calculating the exergetic efficiency of the heat storage by direct computational fluid dynamics (CFD) analysis requires significant amount of walltime and computational resources. Originality/value The paper presents unconventional approach to using standard CFD tools by exploiting numerical diffusion to numerically suppress high-frequency solution oscillations. This strategy grants that the analysis, otherwise requiring impractically long computation walltime, is completed within a practical time.

The study presents a computational study of a drag reduction device based on an active boundary layer control for a generic truck-trailer utility road vehicle. The conceptual device is in accordance with upcoming EU regulations regarding attachable aerodynamic devices for heavy utility vehicles. Design and principles of operation of the conceptual device are presented. The device is intended to increase decrease the trailer’s base drag coefficient by manipulation of the separated flow region behind the vehicle base. Results of a steady state Reynolds averaged analysis and Delayed Detached Eddy Simulation are presented to show the discrepancies of fluid flow patterns between baseline and augmented configuration as well as between mentioned CFD approaches. Results for drag reduction for baseline truck-trailer configuration and aerodynamically augmented configuration are presented.

The goal of this study is to present a comparison between different approaches to multiphase injection modeling of self-pressurized rocket engine propellant. Swirled, tangential orifice injector of nitrous oxide, for an “N” class hybrid rocket motor is the object of the study. A brief descriptionof the injector purpose and geometry is provided, followed by a description of different approaches for flow modeling. Examined techniques range from 0D, Homogeneous Equilibrium Model (HEM) to 3D multiphase with mass and heat exchange between phases. Results of analyses are provided and compared with experimental data. The discrepancies between results are of significant magnitude but expected nature. Co clusions about most feasible approaches for engineering calculations are drawn.

An Active Flow Control drag reduction device concept is presented and a numerical study of the proposed device is carried out. The operating principle of the device is based on the Coanda effect. The device is tested by means of the Reynolds Averaged Navier Stokes (RANS) analysis and the Delayed Detached Eddy Simulation (DDES) analysis. A hybrid multiblock hexagonal mesh with tetrahedral farfield is created. The resolution of the mesh is fitted so as to fulfill the DDES requirements of resolving 80% of the turbulent kinetic energy. The proposed device achieved 11% reduction of drag coefficient. An 8% discrepancy of results between the methods used is presented. Comparisons of flow-field for baseline and concept case is presented. Differences between RANS and DDES results are given. The presented concept is in line with requirements of the EU directive No. 2015/719 [1].

Article presents results of the numerical study concerning nature of blood flow in the post-surgical artery. The research focuses on the development of geometric variants of patches sewn into the common carotid artery during surgery of the atherosclerotic plaque removal. Based on analytical methods, the geometry of the patch described by the polynomial function has been developed. The simulations of blood flow in the arteries with the sewn patch were performed. The study includes the influence of the patient’s diameter, the width and length of the chosen patch on blood flow disorders. The study results comprise the development of software that with the use on input data related to arterial geometry, patch length and patient’s blood parameters (affecting the fluid density and viscosity), shall generate an accurate contour of the patch of width in the selected range.

An analysis of argon gas flow in exemplary configuration of layered bed thermal energy storage is presented. The analysis incorporates URANS model with conjugate heat transfer between gas and solid storage core. The aim of this analysis was to identify key factors limiting exergy efficiency of this storage type and determine some details about storage transient behaviour. Three full cycles of storage loading and unloading having 17 hours physical time in total are simulated, with calculation of exergetic efficiency for each of the cycles. Conclusions regarding this storage type feasibility for indirect power storage in pumped heat systems are made.

Article describes a meshing strategy for efficient computation of generic layered heat storage device for pumped heat energy storage (PHES). Mesh for structural solid body and fluid boundary layer is with unstructured flow field is presented. A rationale for geometry choice, mesh topology and different types of mesh topologies considered in this study. The effect of coarse and fine mesh on computational time and accuracy of results for transient analysis of coupled fluid and heat flow is described.

The article presents a concept of boundary layer control in transonic axial compressors. Two methods for obtaining boundary layer control are presented. It is proposed that by combining those two methods, an efficient way of preventing turbulent boundary layer separation in transonic compressor passages can be obtained without the loss of the compressor flux. The concept, is based on the idea of removing boundary layer flows at one stage, and using this removed flux as a blowing type boundary layer control, at previous stage where lower pressures occur. This creates a loop of secondary flow between those stages preventing the boundary layer separation (especially the shock induced separation) on both stages. Two dimensional numerical analyses are performed to assess the possible passage performance (especially the diffusion factor). On the basis of two dimensional analyses, the possible performance of such compressor stage is estimated. The aerodynamic possibility of greatly increasing the axial compressing stage loadings and pressure ratios without increasing blade velocities and passage flow Mach numbers is shown. This possibility has a growing importance as the overall pressure ratio of turbojet engines and tends to rise with every next engine generation. Main conclusions are drawn, showing the possibilities for further research in the scope of this concept.