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Jürg Alexander Schiffmann

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Related publications (111)

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Thermal management for gas lubricated, high-speed turbomachinery

Jürg Alexander Schiffmann, Wei Liu, Luis Eric Olmedo Ocampo, Wanhui Liu

High-speed turbomachinery is commonly designed to achieve high power densities. Limited space for active cooling results in a challenging thermal management. A thermal modeling approach leveraging modern declarative programming capabilities is presented, y ...

2023

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

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

On the Application of Small-Scale Turbines in Industrial Steam Networks

François Maréchal, Jürg Alexander Schiffmann, Ivan Daniel Kantor, Ansgar Weickgenannt

This study investigates the technical and economic feasibility of replacing throttling valves with smale-scale, oil-free turbomachinery in industrial steam networks. This is done from the perspective of the turbomachine, which has to be integrated into a n ...

2021

Automated Design Tool for Automotive Control Actuators

Jürg Alexander Schiffmann, Cyril Picard

Automated design tools are seldom used in industry. Their potential, however, is high, especially in companies mostly active in variant design, where custom tools could help cut down development time in the early stages. The design of geared electro-mechan ...

2020

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

Readiness evaluation of SOFC-MGT hybrid systems with carbon capture for distributed combined heat and power

Jan Van Herle, Jürg Alexander Schiffmann, Michele Gaffuri, Victoria Xu Hong He

The aggravation of climate change calls for the timely development and implementation of highly efficient, renewable, zero- or negative-emission energy solutions with high technological readiness and feasibility levels. Solid oxide fuel cells (SOFC) consti ...

Elsevier2023

Prediction of the reaction forces of spiral-groove gas journal bearings by artificial neural network regression models

Jürg Alexander Schiffmann, Elia Iseli

This paper presents neural network regression models for predicting the nonlinear static and linearized dynamic reaction forces of spiral grooved gas journal bearings. The partial differential equations (PDEs) are sampled, based on a full factorial and ran ...

2021

Testing and modelling of a novel oil-free co-rotating scroll machine with water injection

Jürg Alexander Schiffmann, Luis Carlos Mendoza Toledo

Efficient compressed air energy storage requires reversible isothermal compression and expansion devices. The isothermal compression and expansion processes can either be approached by several stages with intercooling or by the more convenient injection of ...

Elsevier2017

Experimental investigation of a two-stage oil-free domestic Air/Water heat pump prototype powered by an oil-free high-speed twin-stage radial compressor rotating on gas bearings

Daniel Favrat, Jürg Alexander Schiffmann, Jean-Baptiste Carré

Domestic heat pumps have been identified as a key-technology to decrease the energy consumption of the domestic sector, which represents 29% of the world final energy consumption. Space & water heating represent more than two third of the domestic sector e ...

2016

Robust Design of Herringbone Grooved Journal Bearings using Multi-Objective Optimization with Artificial Neural Networks

Jürg Alexander Schiffmann, Soheyl Massoudi

Herringbone grooved journal bearings (HGJBs) are widely used in micro-turbocompressor applications due to their high load-carrying capacity, low friction, and oil-free solution. However, the performance of these bearings is sensitive to manufacturing devia ...

Amer Soc Mechanical Engineers2023

Theoretical analysis of steam generation methods - Energy, CO 2 emission, and cost analysis

Jürg Alexander Schiffmann

A theoretical case study on steam generation has been performed. Different methods of producing steam by vapour compression, direct electrical heating, gas heating, heat pumping, use of waste heat, and a mixture thereof, were theoretically analysed. The fi ...

Elsevier2017

Techno-Economic Optimization of an Integrated Biomass Waste Gasifier–Solid Oxide Fuel Cell Plant

François Maréchal, Jan Van Herle, Jürg Alexander Schiffmann, Arata Nakajo, Maria del Mar Perez Fortes, Victoria Xu Hong He

With a growing energy demand in a carbon-constrained society, fuels cells powered by renewable fuels, and specifically solid waste, are seen as interesting contributors to the energy portfolio. The alternative energy industry needs to reduce costs, enhance ...

2021

Multi-temperature heat pumps: A literature review

Jürg Alexander Schiffmann

This review highlights the major advantages and challenges of mechanically driven heat pumps and refrigeration systems with focus on multi-temperature applications. Different design strategies are presented, including cycles with multi-stage compressors, e ...

Elsevier2016

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

Heat transfer of flow boiling carbon dioxide in vertical upward direction

Jürg Alexander Schiffmann, Rémi Revellin, David Schmid

Heat transfer measurements of flow boiling Carbon Dioxide (CO2) in vertical upward direction have been carried out with a dedicated test facility at the European Organization for Nuclear Research (CERN). The experiments have been conducted in a vertical up ...

2022

Small, High-Speed, Oil-Free Radial Turbo-compressors for Cooling Applications: Refrigerant Selection

Jürg Alexander Schiffmann

Emerging energy-efficient, oil-free radial centrifugal compressors seem promising for small to mid-capacity air conditioning and refrigeration applications. Compressor design must balance trade-offs among impeller diameter, bearing type, and refrigerant se ...

2018

Real-gas effects on aerodynamic bearings

Jürg Alexander Schiffmann, Eliott Philippe Guenat

Motivated by the use of aerodynamic bearings lubricated with high-pressure gases in energy conversion cycles, the Reynolds equation is adapted in order to include effects of real-gas and turbulence. Three geometries (Rayleigh-step slider, plain and herring ...

2018

Modeling and Designing of a Radial Anode Off-Gas Recirculation Fan for Solid Oxide Fuel Cell Systems

Jan Van Herle, Jürg Alexander Schiffmann, Stefan Diethelm, Zacharie Wuillemin, Patrick Hubert Wagner

To improve the industry benchmark of solid oxide fuel cell (SOFC) systems, we consider anode off-gas recirculation (AOR) using a small-scale fan. Evolutionary algorithms compare different system design alternatives with hot or cold recirculation. The syste ...

2017

Flow pattern observations and flow pattern map for adiabatic two-phase flow of carbon dioxide in vertical upward and downward direction

Jürg Alexander Schiffmann, Rémi Revellin, David Schmid

A test facility to investigate flow pattern transitions of vertical two-phase flow of CO2 has been built within the scope of the high-luminosity detector upgrades at the European Organization for Nuclear Research (CERN). Adiabatic flow pattern observations ...

2022