Multirotor Whirl Flutter: A semi-analytical approach

In the last few years, a new aircraft configuration has been developed: the electric Vertical Take-off/Landing aircraft (eVTOL). To improve aircraft efficiency, structures are lighter and more flexible. Due to the structure's flexible nature and the use of propellers for propulsion, eVTOL are prone to whirl flutter, which consists of a dynamic...

Preliminary aeroelastic design of composite wings with distributed electric propulsion

In the development of electric aircraft, the use of distributed electric propulsion introduces a potential occurrence of propeller whirl flutter, which needs to be taken into account for wing structural design. To this end, this work extends an in-house aeroelastic optimization tool by means of including a post-processing procedure on whirl...

Propeller-wing whirl flutter: an analytical approach

Electrification of aviation is driving new aircraft configurations consisting in slender, lighter wings with several propellers spread across the wing span, including the wing tips. Thinner wings with high aspect ratios tend to be more flexible, and thus, more susceptible to wing flutter, a dynamic aeroelastic instability characterised by...

Towards robust design optimization of automotive turbocharger rotor-bearing systems

In the competitive automotive market, the performance of turbochargers is constantly being pushed towards their theoretical optimum. One of the key components of the turbocharger is the rotor-bearing system, which determines the friction losses and noise output and furthermore affects the overall turbocharger efficiency, reliability and cost. In...

Rotordynamic and friction loss measurements on a high speed Laval rotor supported by floating ring bearings

Floating ring bearings are the commonly used type of bearing for automotive turbochargers. The automotive industry continuously investigates how to reduce the bearing friction losses and how to create silent turbochargers. Many of these studies involve creating a numerical model of the rotor-bearing system and performing validation on a test...

Global Robust Optimization of Computationally Expensive Systems: A Lavel Rotor Suspended by Fluid Film Bearings

Kriging based methods enable the deterministic and robust optimization of computationally expensive systems. With a limited amount of function evaluations the optima are found in an iterative process with expected improvement as infill sampling criteria. Outputs of computer models can be stochastic and/or the models do not always succeed to...

Stability Analysis of a Laval Rotor on Hydrodynamic Bearings by Numerical Continuation: Investigating the influence of rotor flexibility, rotor damping and external oil pressure on the rotordynamic behaviour

Self-excited vibrations in Laval rotors supported by hydrodynamic bearings, know as oil whirl, induce friction losses and noise, or may even damage the system. This transient dynamic behaviour is caused by the stable and unstable equilibria in the system. To study this phenomenon, this research uses numerical continuation. This method determines...

Modeling and Experimental Validation of a Laval Rotor on Plain Journal- and Turbocharger Floating Ring Bearings - The Behavior of High Speed Rotors on Fluid Film Bearings

The first part of this thesis elaborates on two numerical models of different levels of comprehensiveness of a Laval rotor on plain journal bearings. These models are compared to an experiment, capable of rotating at 60 krpm, also devised in this research. Reasonable correlation in terms of whirl and whip behavior has been found. In the second...

Towards accurate prediction of unbalance response, oil whirl and oil whip of flexible rotors supported by hydrodynamic bearings

Journal bearings are used to support rotors in a wide range of applications. In order to ensure reliable operation, accurate analyses of these rotor-bearing systems are crucial. Coupled analysis of the rotor and the journal bearing is essential in the case that the rotor is flexible. The accuracy of prediction of the model at hand depends on its...

Casing Design Methodology For Casing While Drilling

In the current plans of Delft Aardwarmte Project (DAP), it is considered to perform the drilling operation by using pipes which remain in the well after drilling thus acting as a casing, the so-called “Casing While Drilling” (CwD) technique. Due to the absence of drill pipe tripping prior to casing the well, this technique results in reduced...