Classical Nozzle Research Articles

Numerical Investigation of Jet-Wake Interaction for a Dual-Bell Nozzle

The turbulent wake of a planar generic space launcher equipped with a dual-bell nozzle is numerically investigated to examine the interaction of the dual-bell nozzle jet and the wake flow. The simulation is performed at transonic freestream condition, i.e., freestream Mach number $Ma_{\infty }= 0.8$ and freestream Reynolds number based on the launcher thickness ReD = 4.3 ⋅ 105, with the dual-bell nozzle operating at sea-level mode. A zonal RANS/LES approach is used and the time-resolved flow field data is analyzed by classical spectral analysis and modal decomposition techniques, i.e., proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). The overall flow topology of the recirculation region downstream of the base and the pressure loads on the outer nozzle fairing are only slightly affected by the modified nozzle shape. However, the changed nozzle flow topology characterized by the flow separation at the nozzle contour inflection leads to a backflow region and an entrainment of the outer flow into the nozzle extension which results in increased pressure loads on the inner nozzle wall. Using spectral, POD, and DMD analyses, the outer wake flow is investigated, revealing a growing and contracting of the separation bubble and an undulating motion of the shear layer similar to the “cross-pumping” and “cross-flapping” motion detected in previous investigations of a configuration with a classical nozzle and a jetless backward facing step setup. The spectral and modal analysis of the nozzle flow shows that the increased pressure loads detected at the inner wall of the nozzle extension are caused by an interaction of the separated shear layer inside the nozzle extension with the shock pattern that leads to a streamwise oscillation of the shock and a pumping or wave-like motion of the shear layer.

Accurate stage-by-stage modelling of axial turbines using an appropriate nozzle analogy with minimal geometric data

This paper presents a methodology to model a turbine on a stage-by-stage basis using nozzle flow analogy, requiring minimal detail information of the geometry of the individual blade passages. The classical nozzle theory is slightly expanded such that a turbine stage can be represented as a series of two nozzles with appropriate inlet conditions and loss factors. Conservation equations and component characteristics are presented which can be programmed into a simultaneous solver.The thermo-hydraulic network solver Flownex was used to model the nozzles in such a manner. This enabled the definition of a custom turbine stage component, which was then used to model a 4-stage air turbine, as well as two steam turbines of an arbitrary power plant. The model predicted the turbines’ off-design (low load) conditions very well, considering the limited information used to set up the models.The approach can be used for accurate prediction of a turbine’s off-design and abnormal operation, provided the physical geometry of the turbine remains unchanged. Plant operators can use this method to obtain better information regarding the inter-stage process conditions of a turbine, without requiring detail design information or complex CFD software.

Microstructural properties of ZnO:Sn thin films deposited by intermittent spray pyrolysis process

Zinc oxide films have been prepared via spray pyrolysis using a perfume atomizer. ZnCl2 has been used as precursor. The influence of the precursor solution and dopant concentration has been investigated. Homogeneous films are obtained with a precursor concentration ranging between 0.3 and 0.4 M and a SnCl2 dopant concentration of 1–2%. The films exhibit broad band gaps and small conductivity. The microstructural properties of these films have been compared with that of films deposited using a classical nozzle. Films deposited by perfume atomizer are rougher, with smaller grain size, compared to films deposited with a classical nozzle.

Optical homogeneity of the active media of cw chemical HF(DF) lasers

The optical homogeneity of the active media of cw chemical lasers was investigated by interferometry. A study was made of how the optical quality of the active media was influenced by the characteristics of various configurations of nozzle arrays (classical nozzle—nozzle configuration, configurations with discrete supply of the secondary fuel to the supersonic channel, and those with radial expansion or with a honeycomb structure). The dependences of the integral optical homogeneity criterion, the Strehl number, on the main operational parameters of a laser were determined. The optical homogeneity of the active medium was reduced by intensification of the processes which improved the operational parameters.

Nozzle dynamics

Motion equations of one-dimensional nozzle flows have a hamiltonian structure identical to that of a very different sytem: adiabatic fluid dynamics dimensionally reduced with respect to a direct sum of orthogonal groups. This correspondence allows one to generalize classical nozzle dynamics to the case of higher-dimensional magnetohydrodynamical flows.