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Jürg Alexander Schiffmann

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Publications associées (112)

Realistic Constrained Multi-Objective Optimization Benchmark Problems from Design

Jürg Alexander Schiffmann, Cyril Picard

Multi-objective optimization is increasingly used in engineering to design new systems and to identify design trade-offs. Yet, design problems often have objective functions and constraints that are expensive and highly non-linear. Combinations of these fe ...

2020

Theoretical and Experimental Investigation of a Small-scale, High-speed, and Oil-free Radial Anode Off-gas Recirculation Fan for Solid Oxide Fuel Cell Systems

Jürg Alexander Schiffmann, Jan Van Herle, Patrick Hubert Wagner

The Laboratory for Applied Mechanical Design (LAMD) designed, manufactured, and experimentally tested a novel recirculation fan for a 10 kWe solid oxide fuel cell (SOFC). The fan uses oil-free bearings, more specifically herringbone-grooved journal and spi ...

2020

An Instrumented High-Speed Rotor with Embedded Telemetry for The Continuous Spatial Pressure Profile Measurement in Gas Lubricated Bearings: A Proof of Concept

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Pressure is one of the constitutional quantities governing the flow field in gas lubricated bearings. Knowledge of the pressure is of principal importance in the fundamental understanding of such bearings and for the calibration of reduced order models. Th ...

2020

Sofc system with anode off-gas recirculation

Jürg Alexander Schiffmann, Daniel Favrat, Jan Van Herle, Zacharie Wuillemin, Patrick Hubert Wagner

The present invention concerns an SOFC system comprising an anode off-gas recirculation arrangement in which anode off-gas is pumped by a fan or pump of a coaxial turbine-fan assembly, the system comprising a condenser for condensing water contained in sai ...

2020

Two-phase and oil-free co-rotating scroll compressor/expander

Jürg Alexander Schiffmann

This paper discusses experimental and theoretical investigations about a re-designed co-rotation scroll machine, operating in compressor and expander mode. The machine has been tested under various operational conditions, with the aim to determine the infl ...

2019

Performance potential of gas foil thrust bearings enhanced with spiral grooves

Jürg Alexander Schiffmann, Eliott Philippe Guenat

The upscaling of turbomachinery using gas foil thrust bearings is limited because of their limited load capacity and the thermal issues linked with very thin film thickness. The improvement potential of spiral grooves manufactured on the top-foil of such b ...

2019

Thin Gas Film Isothermal Condensation in Aerodynamic Bearings

Jürg Alexander Schiffmann, Eliott Philippe Guenat

High-speed small-scale turbomachinery for waste heat recovery and vapor compression cycles is typically supported on gas-lubricated bearings operating close to the saturation conditions of the lubricant. Under particular conditions, the gas film might loca ...

2019

Impact of large tip clearance ratios on the performance of a centrifugal compressor

Jürg Alexander Schiffmann, Markus Diehl

Ultra-compact and fast spinning turbomachinery is a key technology to increase performance of domestic heating applications and to address decentralization of power and heat as a consequence of the rise of renewable energy sources. Recently, a heat pump us ...

2019

Pressure Profile Measurements Within The Gas Film Of Journal Foil Bearings Using An Instrumented Rotor With Telemetry

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Foil bearings are strong candidates to support oil -free turbomachinery. Although foil bearings are a widely used technology, models describing their behavior are not validated using the film pressure, which is the fundamental variable of any fluid film be ...

Amer Soc Mechanical Engineers2019

Multi-Objective Optimization of Grooved Gas Journal Bearings for Robustness in Manufacturing Tolerances

Jürg Alexander Schiffmann, Eliott Philippe Guenat

A tolerancing method highlighting trade-offs against key design variables of mechanical systems is proposed and applied to herringbone-grooved gas journal bearings. Gas bearings typically suffer from a subsynchronous instability, demanding a very tight tol ...

2019

An Instrumented High-Speed Rotor With Embedded Telemetry For The Continuous Spatial Pressure Profile Measurement In Gas Lubricated Bearings: A Proof Of Concept

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Gas lubricated bearings are capable of supporting high speed rotors with satisfactory load capacities. Pressure is one of the constitutional quantities governing the flow field in gas lubricated bearings. Knowledge of the pressure is of principal importanc ...

Amer Soc Mechanical Engineers2019

Data-Driven Model for the Dynamic Characteristics of O-Rings for Gas Bearing Supported Rotors

Jürg Alexander Schiffmann, Philipp Kaspar Bättig

The measurement results of various nitrile butadiene rubber (NBR) O-Ring sizes are pre-sented, and reduced-order models are developed in order to predict the stiffness and damping coefficient as a function of O-Ring geometry, Shore hardness, squeeze, and e ...

2019

Theoretical and Experimental Investigation of a Small-Scale, High-Speed, and Oil-Free Radial Anode Off-Gas Recirculation Fan for Solid Oxide Fuel Cell Systems

Jürg Alexander Schiffmann, Jan Van Herle, Patrick Hubert Wagner

2019

Multi-objective optimization of turbo-ORC systems for waste heat recovery on passenger car engines

Jürg Alexander Schiffmann, Kévin Rosset, Eliott Philippe Guenat, Violette Mounier

Waste heat recovery from passenger car internal combustion engines by means of an organic Rankine cycle (ORC) system is promising for reducing CO2 emissions. In this study, different cycle configurations capable of converting waste heat from both coolant a ...

2018

Dynamic pressure probe response tests for robust measurements in periodic flows close to probe resonating frequency

Jürg Alexander Schiffmann, Fatma Ceyhun Sahin

A single-hole probe was designed to measure steady and periodic flows with high fluctuation amplitudes and with minimal flow intrusion. Because of its high aspect ratio, estimations showed that the probe resonates at a frequency two orders of magnitude low ...

Institute of Physics2018

Non-linear transfer function identification of pressure probes using Siren Disks

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash, Fatma Ceyhun Sahin

This article presents a Siren Disk proof of concept for the dynamic excitation of pressure probes, and a method to reconstruct distorted signals due to pneumatic channels. Constraints in sensor installation require placing a pressure transducer distant fro ...

2018

Data-Driven Pre-Design Tool for Small Scale Centrifugal Compressors in Refrigeration

Jürg Alexander Schiffmann, Cyril Picard, Violette Mounier

Domestic scale heat pumps and air conditioners are mainly driven by volumetric compressors. Yet the use of reduced scale centrifugal compressors is reconsidered due to their high efficiency and power density. Recent work has demonstrated the technical feas ...

2018

Spatially Sampled Pressure Profile Measurements in Externally Pressurized Gas Journal Bearings

Jürg Alexander Schiffmann, Eliott Philippe Guenat, Karim Magdi Zakaria Abdelrahman Shalash

Externally pressurized gas journal bearings (EPGJB) are widely adopted to support high speed rotors. This paper presents novel experimental benchmark test data which enables EPGJB model validation. Axial and circumferential pressure profile measurements ar ...

2018

Impacts of Constraints and Constraint Handling Strategies for Multi-Objective Mechanical Design Problems

Jürg Alexander Schiffmann, Cyril Picard

Multi-objective optimization tools are becoming increasingly popu-lar in mechanical engineering and allow decision-makers to better understand the inevitable trade-offs. Mechanical design problems can however combine properties that make the use of optimiz ...

2018

Small scale radial inflow turbine performance and pre-design maps for Organic Rankine Cycles

Jürg Alexander Schiffmann, Luis Eric Olmedo Ocampo, Violette Mounier

While small scale ORCs are currently dominated by volumetric expanders, the use of turbomachines is reconsidered due to their high efficiency and power density. Yet, suitable performance maps, which ensure an accurate starting point for the turbine design, ...

Elsevier2018

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