8 research outputs found

    Large Eddy Simulation of the Pulsating, Non-Reacting Flow in Combustion Chambers

    Get PDF
    In the present work a numerical investigation of the pulsating, non-reacting flow in a combustion chamber, and a coupled system of burner plenum and combustion chamber is presented. The results are compared with an analytical model and experimental data. The numerical simulations provide the damping ratio, an important input, for the analytical model, which was developed to predict the stability limits of technical combustion systems

    A Centrifugal Fan Test Bench for Validation Data at Off-Design Conditions

    Get PDF
    Nowadays with eco directives becoming more strictly the efficiency improvement of turbomachinery is getting more important than ever. Relieving experimental investigations computational fluid dynamics (CFD) could be the major tool to optimize the geometry of a turbomachinery, as it can provide a detailed insight into the flow within the impeller. In order to have reliable results from CFD simulations a validation of the acquired simulation tool and the composed numerical model is crucial. Especially in off-design conditions it is very challenging for CFD to predict strongly whirling, highly unsteady flow fields correctly. In the present paper the construction of a test bench for a centrifugal fan with spiral casing is described and the first results are presented. The main goal in constructing the test case is to provide extensive validation data not only in the design operation point but for off-design conditions also. The geometry was designed based on classical design guidelines. It is close to industrial centrifugal fans however an additional aim was, to provide a geometry which allows an acceptable mesh generation effort and high mesh quality. Due to the rotational periodicity of axial and radial fans without casing, those types can be calculated by regarding only a single blade passage, which decreases the number of required cells and hence the necessary computational power. For centrifugal fans with spiral casing this simplification is not suitable and this construct induces additional issues as pressure pulsation, acoustics, pulsating radial force, periodic load of vanes etc. The present test case should provide availability to investigate such phenomena also. The characteristic and the efficiency curve of the fan are measured with standardized methods. Beyond this “Particle Image Velocimetry” (PIV) is chosen to measure the flow field within the blade channels and the spiral casing, as well, in several different positions relative to the corner (“tongue”). For the optical accessibility the hub of the impeller and the main parts of the casing are made out of acrylic glass. In order to keep the seeding particles within the system a closed loop test rig is constructed. The inlet section of the fan was designed to get well defined inlet conditions for the numerical simulation. The first investigations were carried out at a rotational speed of 600 rpm, and compared with results from CFD. These results are presented and discussed in the present paper. Further investigations will be performed at higher rotational speed

    Towards a Fair Centrifugal Fan Database for Off-Design Validation of CFD Simulations

    Get PDF
    Turbomachineries such as fans are energy conversion machines which can be found in many daily technical devices. The bandwidth of power consumption ranges from a few watts to megawatts and energy-saving requirements are getting increasingly strict with every year. Therefore, a continuous study of the flow phenomena inside such machines is necessary to identify and to understand the sources of energy losses. To analyze the flow phenomena beyond empirical findings, Computational Fluid Dynamic (CFD) simulations are nowadays being used to unlock further potentials for design optimizations and energy savings without the need for expensive experiments. While the optimal operation point typically can be described well by such simulations, the off-design conditions of turbomachineries are very challenging to predict due to unsteady effects for instance. A validation test bench for a low-pressure centrifugal fan with a spiral casing has been built and Particle Image Velocimetry (PIV) is used to measure the flow field in several different positions and various operation points. The acquired data together with the geometry and a structured CFD mesh is provided through an open-source database and is intended to be used by researchers to validate their CFD codes and methods. On the pathway towards the centrifugal fan database, research and meta data management along with an uncomplicated data access organization are two key building blocks. This paper highlights the concept and implementation of the data management using HDF5 as the underlying data file format. Furthermore, the workflow and tools provided for other scientists, that aim to validate their fan CFD simulations, is presented

    Assessment of condensation models for moist air transonic flow prediction

    No full text
    The aim of this article is to thoroughly analyse the influence of condensation models on the modelling of condensation phenomena in transonic flow of moist air. The reason for the study was the fact that different condensation models are used by researchers to obtain satisfactory results of numerical modelling. The condensation models tested herein differ in the nucleation rate formula and the droplets growth equation. Four most often used condensation models were selected for detailed investigations. The results obtained from each model were compared with experiments for the nozzle flow. The main focus was on the location of the onset of the nucleation process. Moreover, the droplets growth intensity was compared and discussed. The nozzle flow CFD calculations were performed using the ANSYS Fluent commercial tool. Finally, the condensation model which is the most suitable for the moist air transonic flow was recommended

    Identification of unsteady effects in the flow through a centrifugal fan using CFD/CAA methods

    No full text
    Besides centrifugal pumps, centrifugal fans are the most common turbomachines used in technical applications. They are commonly used in power engineering systems, such as heat engines and chillers, heating, ventilation, and air conditioning systems, supply and exhaust air systems. They are also used as machines consuming final energy (electricity). Therefore, any improvement in their efficiency affects the efficiency of energy generation and the level of electricity consumption. Many efforts have been made so far to find the most efficient numerical method of modelling flows in fans. However, only a few publications focus on the unsteadiness that may have an impact on device efficiency and noise generation. This paper presents an attempt to identify unsteadiness in the flow through a centrifugal fan by means of computational fluid dynamics and computational aeroacoustics methods. The works were performed using the Ansys CFX commercial software and the results of numerical studies are compared with experimental data
    corecore