HUBICH, I. Analýza tlakových ztrát v mazací soustavě turbodmychadla [online]. Brno: Vysoké učení technické v Brně. Fakulta strojního inženýrství. 2025.

Posudek vedoucího

Novotný, Pavel

The 43-page thesis (33 pages excluding the introduction and reference list) analyses the oil flow in a turbocharger lubrication system for various operating conditions. The student worked actively during the last phase of development of the thesis and continuously searched for solutions in the available literature and also using AI tools in solving the given problem. The review of the state of the art basically includes historically proven analytical relations for the calculation of flow in 1D domains. These analytical methods are applied appropriately to the problem at hand. The originality and the student's own contribution is questionable, as there is a vast amount of literature for solving the problem and a considerable complement of AI tools. The realism of the results cannot be accurately assessed, probably at least the tendencies and overall values of the turbocharger flow rates are essentially correct. The work shows a certain number of formal shortcomings, but this fact does not affect the quality of the work. After the overall evaluation, it can be concluded that the student has clearly fulfilled the requirements set for the bachelor thesis.

Posudek oponenta

Vacula, Jiří

Mr. Hubich's bachelor's thesis spans 33 pages, excluding the formal introductory sections and the list of references. The thesis focuses on analyzing the pressure drop in a turbocharger lubrication system that includes both axial and radial hydrodynamic bearings. The first part of the work presents a literature review covering turbocharger components, lubrication principles, and basic concepts of hydraulic losses. The latter part is devoted to the calculation of pressure losses in a specific turbocharger configuration. One can certainly appreciate the work the author has put into tracking down the loss coefficients in the extensive work Idelchik. However, the issue lies in the overall physical approach to the problem. The system in question features branching flow paths, a combination of series and parallel resistances, where the power equation instead of Bernoulli equation should be applied. Although the Bernoulli equation is correctly written between points on a streamline (i.e., where the flow does not branch), this raises concerns about the validity of the overall analysis. Furthermore, the thesis defines pressure drop as the difference between inlet and outlet static pressures (see p. 27: "The pressure drop can be expressed as a difference between the inlet p1 and outlet p2"), which is not physically true. Pressure drop is defined as the difference in total pressures. Both the graphs and equations (18) and (19) reflect static pressure differences. Physically speaking, this does not represent a true pressure drop. However, since static pressure is often the only quantity measured in practice, the results presented may still align with measurement conditions, despite not fully capturing the physical reality. It is also unfortunate that the author did not utilize a graphical method for combining the resistance characteristics of the hydraulic network, which would have more clearly illustrated the behaviour of individual branches of the system as a whole. Several graphical and content-related issues are also present in the thesis. Examples include inconsistent text alignment (e.g., Table 1 on p. 15; paragraphs in sections 4.2 and 4.3.2; section 6.8 containing only a single sentence; a blank page on p. 44), vague presentation of results (e.g., Chapter 1 mentions “results for different input parameters” without specifying what those parameters are), and unsupported claims (e.g., Chapter 8.2 states that pressure drop can be reduced by lowering surface roughness, yet provides no calculation or reference to the equations used). In summary, although the thesis could have been executed in a more physically rigorous and illustrative way, it still presents practical results and fulfills the goals.

eVSKP id 165882