Simulations of flow and heat conditions in a disc brake are presented in the article. Through simulations different parameters that influence the air flow field were analysed: the size of calculated domain, mesh, boundary conditions and turbulent model. In addition, different ways of applying time-dependent heat source were tested. Simulations with stationary flow field and transient temperature field were compared to a totally trasient simulation. Results show that flow (and consequently heat) conditions in air in case of stationary and transient flow field calculation match relatively well. However in stationary calculation the formation and separation of vortices, that is happening in reality and because of which the actual heat transfer is greater, cannot be seen.
COBISS.SI-ID: 16303894
This article is focused on the choice of a suitable turbulence model for simulations of an industrial pumpćs intake, from the perspective of accuracy and, partially, also the CPU time. Twelve steady-state and transient simulations were made on a fine computational mesh, using turbulence models such as: the shear stress transport (SST), the scale-adaptive simulation (SAS), the Reynolds stress model, the explicit algebraic Reynolds-stress model, the detached eddy simulation and the large eddy simulation (LES). The curvature-correction (CC) option was assessed for the SST and SAS turbulence models. The results were compared with the LES and with published experimental results. Although all the models could predict the main floor vortex, there were still some substantial differences. It can be able to conclude that it is better to use either the SST-CC turbulence model, due to its low-computational resources and far better results than the SST model, or the SAS-CC turbulence model, since its predictions are quite similar to the LES results. In the final step, good agreement with experimental results was shown for a longer simulation with the SAS-CC turbulence model.
COBISS.SI-ID: 15259158
This paper presents a problem-solving procedure regarding brake-drum noise issues performed by engineers within a short time period and additional measures to be taken for avoiding similar issues in the future. Cimos TAM Ai company is a member of Cimos Group, which is a component producer in the automotive industry. We have taken the production of the rear brake-drums during the phase of the car manufacturing (transfer of production). Soon afterthe instigation of this production, the customer reported squealing issues with the brake-drums. No detailed information was received about the issue except that it occurred on new cars during everyday operation. It was our goal to find the root cause, fix the issue and take some preventive actions. Research was based on comparing the Cimos brake-drum (B) with the brake-drum of previous supplier (A). The research was focused on resonant frequency of the brake-drum as the most likely parameter connected to the squealing. First the natural frequency of drums A and B was determined by impact-hammer test. Then a numerical simulation was carried out with the goal of detecting the most problematic surface of the drum for causing the squealing. A weakness was found in the brake-drum design where no thickness ortolerance was specified at the critical area, and large deviations existed between the finished brake-drums. The problem was solved by changing the machining parameters. Besides solving the noise problem, an in-depth investigation was conducted into the gray cast-iron modulus of elasticity, in order to find a representative value for those small deformations occurring incases dealing with noise-emission issues. This value proved to be higher than in the case of larger deformations as considered during mechanical and temperature behavior simulations.
COBISS.SI-ID: 17432086
This article represents the improved numerical model for steady-state simulation of heat transfer and fluid flow (CFD) at ventilated brake disc. The purpose of the model is to evaluate the convective heat flux and also the efficiency of the disc cooling. The model in upgraded with real air material properties, which shows to have a great impact on the result like heat flux etc. In this study we compare two different discs design and the results showed the realistic conditions, got from the experimental work made by the company Cimos d.d. This way the numerical model is suitable to evaluate different disc designs, which is very important for the industry in the early stage of the new disc design.
COBISS.SI-ID: 18125590
An experimental study of an axial fan in different operating regimes was performed. The experimental data were acquired using pressure sensors and PIV (Particle Image Velocimetry). The axial fan characteristic curve was divided into its stable and unstable part area. In the unstable area, the rotating stall regime was determined. The location of sudden and deep stall on the characteristic axial fan's curve and the hysteresis area was also determined. Flow fields upstream of the axial fan's rotor and blade passage on three different spans were measured using PIV system.
COBISS.SI-ID: 16304150