Jürg Alexander Schiffmann

After obtaining his diploma in mechanical engineering from EPFL in 1999 he co-founded a start-up company dedicated to the design of gas bearing supported rotors. In 2005 he joined Fischer Engineering Solutions where he led the development of small-scale, gas bearing supported high-speed turbomachinery for fuel cell air supplies and for domestic scale heat pumps. In parallel he worked on his PhD, which he obtained from EPFL in 2008 and for which he was awarded the SwissElectric Research Award. He then joined the Gas Turbine Lab at MIT as a postdoctoral associate where he worked on foil bearings and on the experimental investigation of radial diffusers. In 2013 he was nominated assistant professor at the Ecole Polytechnique Fédérale de Lausanne where he founds the Laboratory for Applied Mechanical Design. His current research interest are in gas lubricated bearings, in aerodynamics of small-scale compressors and turbines and in automated design and optimization methodologies.

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Pompe à chaleur

Une pompe à chaleur (PAC), aussi appelée thermopompe en français canadien, est un dispositif permettant de transférer de l'énergie thermique (anciennement « calories ») d'un milieu à basse températu

Design

vignette|Chaise de Charles Rennie Mackintosh, 1897. Le design, le stylisme ou la stylique est une activité de création souvent à vocation industrielle ou commerciale, pouvant s’orient

Fluid bearing

Fluid bearings are bearings in which the load is supported by a thin layer of rapidly moving pressurized liquid or gas between the bearing surfaces. Since there is no contact betwe

ME-311: Dynamical effects in mechanical design

Ce cours poursuit la compréhension des effets cinématiques et dynamiques de systèmes mécaniques complexes et introduit les bases pour les comprendre et les modéliser. L'étudiant saura expliquer et modéliser la dynamique et choisir des modèles adéquats.

ME-403: Applied mechanical design

Students will be exposed to hands-on design problems throughout the term. They will acquire methodologies to (1) address open ended engineering problems, (2) cultivate creativity, (3) support decision making and (4) develop problem solving abilities.

ME-459: Thermal power cycles and heat pump systems

This course aims at studying thermal power cycles, heat pumping technologies, and equipment.

Design and experimental investigation of a herringbone grooved gas bearing supported turbocharger

Wanhui Liu, Jürg Alexander Schiffmann

The design of an oil free turbocharger supported on herringbone grooved gas bearing was formulated as a multi-objective problem, which was solved by coupling a reduced order parametric model for gas bearing supported rotors with an evolutionary algorithm. The resulting Pareto curve offers the best possible tradeoff between the two competing objectives of maximizing the rotordynamic stability and minimizing the power losses. After manufacturing, the turbocharger was successfully operated up to 170 krpm, beyond a hybrid mode composed of a rigid body cylindrical and a flexural mode. Supercritical operation above a flexural bending mode on rigid gas lubricated bearings was possible due to the smart selection of the location of two balancing planes, to avoid the excitation of the flexural mode. A coast down test suggests minimum friction torque and therefore lift-off at 3 krpm. Bearing power loss tests performed at 40 ℃ and 100 ℃ showed that the herringbone grooved gas bearing supported oil-free turbocharger yields only 50% to 70% of the traditional semi-floating oil bearing supported turbochargers, which is a distinct advantage in terms of efficiency and cut in emissions. The theoretical and experimental results presented in this paper clearly demonstrate the rotordynamic feasibility of oil-free turbochargers supported on herringbone grooved gas bearings.

2023

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Design, computational and experimental investigation of a small-scale turbopump for organic Rankine cycle systems

Jürg Alexander Schiffmann, Sajjad Zakeralhoseini

The hydraulic design, computational analysis, and experimental investigations of a high-speed small-scale turbopump for mobile waste heat recovery applications based on organic Rankine cycle systems are presented in this paper. Such applications demand high-pressure rise, lightweight, and compact pumping systems with simple construction. The investigated turbopump features an unshrouded 37.75 mm tip diameter single-stage centrifugal pump equipped with eight radial blades, eight splitters blades, and a rectangular axisymmetric volute. The pump should deliver 0.28 kg/s of mass flow rate with a pressure rise of 20 bar at a designed rotational speed of 25,000 rpm. Due to uncertainties observed in employing state-of-the-art 1-d methods that are valid for much larger machines, computational fluid dynamics is utilized to obtain a design meeting the specifications. The pump’s performance is evaluated experimentally at different rotational speeds, mass flow rates, and impeller tip clearances. The excellent agreement between experimental data and predictions from computational fluid dynamics validates the design methodology and computational results. The turbopump’s characteristics are then utilized to estimate the possible performance improvement of a target organic Rankine cycle using the novel turbopump instead of a commercial multi-stage centrifugal pump. The comparison suggests that the novel turbopump increases the efficiency of the target organic Rankine cycle by 0.3 % points and decreases its back-work ratio by nearly 50 %. The novel turbopump is approximately ten times more compact compared to commercial systems.

2023

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Haptics based multi-level collaborative steering control for automated driving

Hannes Bleuler, Robert Fuchs, Tomohiro Nakade, Jürg Alexander Schiffmann

Increasing the capability of automated driving vehicles is motivated by environmental, productivity, and traffic safety benefits. But over-reliance on the automation system is known to cause accidents. The role of the driver cannot be underestimated as it will ultimately be the most relevant aspect for trust building and social acceptance of this technology. Here we introduce a driver-oriented automation strategy to achieve collaborative steering. Our approach relies on three major functionalities: interaction, arbitration, and inclusion. The proposed control strategy is grounded in the concept of shared control enabling driver intervention over the automation without deactivation. Well-defined physical human-robot interaction types are made available with the arbitration strategy. The automated driving trajectory is adapted to include the driver intent into the tactical level of trajectory planning. This enables driver initiated rerouting and consistent coordination of all vehicle actuators. In this way, automated vehicles, which rely on sight only, are augmented with the incorporation of the driver intent. The driver is neither replaced by nor excluded from the automation, rather their role remains active to the benefit of trust building and driving safety.

2023

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