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Jürg Alexander Schiffmann

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Related publications (111)

Page 3 of 6

Brine-to-water heat pump test system for small-scale oil-free turbo compressors

Jürg Alexander Schiffmann

Hermetic, small-scale turbo compressors supported on gas-lubricated bearings and driven by high-speed electric motors represent a promising technology to increase the efficiency of domestic heat pumps and air conditioners. Moreover, thanks to the oil-free ...

Int Inst Refrigeration2023

Experimental Investigation of a Small-Scale Organic Rankine Cycle Turbo-Generator Supported on Gas-Lubricated Bearings

Jürg Alexander Schiffmann, Kévin Rosset

Waste heat recovery (WHR) is expected to contribute to reducing CO2 emissions from trucks. Organic Rankine cycle (ORC) systems show the highest potential for this application, but still lack efficient small-scale expansion devices, in practice. A novel tur ...

2021

Parametric Reduced Order Model of a Gas Bearings Supported Rotor

Fabio Nobile, Jürg Alexander Schiffmann, Dimitri Maurice Goutaudier

Gas bearings use pressurized gas as a lubricant to support and guide rotating machinery. These bearings have a number of advantages over traditional lubricated bearings, including higher efficiency in a variety of applications and reduced maintenance requi ...

Amer Soc Mechanical Engineers2023

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

Theoretical Study of a Novel Oil-Free Co-Rotating Scroll Compressor Integrated into a Hybrid Absorption Heat Pumps

Jürg Alexander Schiffmann, Luis Carlos Mendoza Toledo

Hybrid absorption heat pumps (Osenbrück cycle and Hybrid wet compression cycle) are known for high temperature lifts, low-pressure ratios and wide capacity control. They are well suited for processes with the occurrence of significant heat sink and heat so ...

2016

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

A new method to interpolate POD reduced bases-Application to the parametric model order reduction of a gas bearings supported rotor

Fabio Nobile, Jürg Alexander Schiffmann, Dimitri Maurice Goutaudier

The proper orthogonal decomposition (POD) is successfully employed in a variety of projection-based methods for parametric model order reduction (pMOR) of large dynamical systems. It extracts the most energetic modes describing the dynamics of a system fro ...

Wiley2023

Adiabatic two-phase pressure drop of carbon dioxide in different channel orientations

Jürg Alexander Schiffmann, Rémi Revellin, David Schmid

Adiabatic pressure drop measurements of two-phase Carbon Dioxide (CO2) have been carried out in horizontal, vertical upward and downward direction with a dedicated test facility at the European Organization for Nuclear Research (CERN). A database of more t ...

2022

Theoretical and Experimental Investigation of a 34 Watt Radial-Inflow Steam Turbine with Partial-Admission

Jan Van Herle, Jürg Alexander Schiffmann, Patrick Hubert Wagner

A micro steam turbine with a tip diameter of 15mm was designed and experimentally characterized. At the nominal mass flow rate and total-to-total pressure ratio of 2.3 kgh-1 and 2, respectively, the turbine yields a power of 34W and a total-to-static isent ...

2021

Influence of Large Relative Tip Clearances for a Micro Radial Fan and Design Guidelines for Increased Efficiency

Jan Van Herle, Jürg Alexander Schiffmann, Patrick Hubert Wagner

The blade tip clearance loss was studied experimentally and numerically for a micro radial fan with a tip diameter of 19:2mm. Its relative blade tip clearance, i.e., the clearance dividedby the blade height of 1:82mm, was adjusted with different shims. The ...

2021

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 ...

2023

Design, experimental investigation and multi-objective optimization of a small-scale radial compressor for heat pump applications

Daniel Favrat, Jürg Alexander Schiffmann

The main driver for small scale turbomachinery in domestic heat pumps is the potential for reaching higher efﬁciencies than volumetric compressors currently used and the potential for making the compressor oil-free, bearing a considerable advantage in the ...

2010

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

Analysis and modeling of the tip leakage flow on the performance of small-scale turbopumps for ORC applications

Jürg Alexander Schiffmann, Sajjad Zakeralhoseini

In this paper, the influence of tip clearance on the performance of small-scale turbopumps is studied numerically on extensive parameter ranges suitable for organic Rankine cycle applications. A novel and fully parameterized design model is developed and u ...

2022

Flexible Support for Gas-Lubricated Bearing Bushings

Jürg Alexander Schiffmann

Herringbone-grooved journal bearings (HGJBs) for high-speed turbo-machinery are often supported on O-rings due to their favorable stiffness and damping characteristics for stability and alignment reasons. They yield limited lifetime at high temperatures, i ...

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

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

Robust design optimization of gas-lubricated herringbone grooved journal bearings: Surrogate modeling and experimental validation

Cameron John Bush, Jürg Alexander Schiffmann, Soheyl Massoudi

This study experimentally validates robust designs for herringbone grooved journal bearings (HGJBs) in micro-turbocompressors, addressing manufacturing deviations that lead to rotor instabilities. Experiments on a Pelton-driven rotor system focused on maxi ...

2025

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

Jürg Alexander Schiffmann, Violette Mounier, Luis Eric Olmedo Ocampo

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

Towards a real-time capable hybrid-twin for gas-bearing supported high-speed turbocompressors

Jürg Alexander Schiffmann, Luis Eric Olmedo Ocampo

A hybrid-twin for gas-bearing supported, high-speed turbocompressor is suggested to be an aide to increase the operational reliability and to provide valuable insights to improve its design. The bearing clearances of a few micrometers imply that excessive ...

2023