Recherche

Afficher tous les résultats pour

Accueil

Personne

Jürg Alexander Schiffmann

À propos
Confidentialité
Mentions légales

Graph Chatbot

Publications associées (112)

The effects of the tip clearance on the performance of small-scale turbopumps for ORC applications; analysis and modeling

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 ...

Technical University of Munich2021

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

Jürg Alexander Schiffmann, Jan Van Herle, 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

Nonlinear study on a rigid rotor supported by herringbone grooved gas bearings: Theory and validation

Jürg Alexander Schiffmann, Patrick Hubert Wagner, Philipp Kaspar Bättig, Wanhui Liu

The nonlinear behavior of a rigid rotor supported by herringbone grooved journal gas bearings (HGJBs) was investigated in this study. The two-dimensional narrow groove theory (2D-NGT) was adopted to model the HGJBs. A set of integrated rotor-bearing state ...

2021

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

Jürg Alexander Schiffmann, Jan Van Herle, 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

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

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

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

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

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

Jürg Alexander Schiffmann, Jan Van Herle, Arata Nakajo, François Maréchal, 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

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

Jürg Alexander Schiffmann, Jan Van Herle, Patrick Hubert Wagner

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

2021

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

Scale limitations of gas bearing supported turbocompressors for vapor compression cycles

Jürg Alexander Schiffmann

An analysis of single-stage centrifugal compressors supported on dynamic, gas lubricated bearings for driving vapor compression cycles suggests that the maximum feasible compressor power is limited, primarily by the bearing load capacity, in the range from ...

2020

Experimental characterization of a solid oxide fuel cell coupled to a steam-driven micro anode off-gas recirculation fan

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

While the global fuel utilization of solid oxide fuel cells (SOFCs) is limited by the stack aging rate, the fuel excess is typically used in a burner, and thus limiting the system electrical efficiency. Further, natural-gas-fueled SOFCs require treated wat ...

2020

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 bea ...

2020

Analysis of Spiral-Grooved Gas Journal Bearings by the Narrow-Groove Theory and the Finite Element Method At Large Eccentricities

Jürg Alexander Schiffmann, Eliott Philippe Guenat, Elia Iseli

A finite groove approach (FGA), based on the finite element method (FEM), is used for analyzing the static and dynamic behavior of spiral-grooved aerodynamic journal bearings at different eccentricities, number of grooves, and compressibility numbers. The ...

2020

The Role of Reynolds Number Effect and Tip Leakage in Compressor Geometry Scaling at Low Turbulent Reynolds Numbers

Jürg Alexander Schiffmann, Markus Diehl, Christoph Schreiber

In compressor design, a convenient way to save time is to scale an existing geometry to required specifications, rather than developing a new design. The approach works well when scaling compressors of similar size at high Reynolds numbers but becomes more ...

2020

Extended Windage Loss Models for Gas Bearing Supported Spindles Operated in Dense Gases

Jürg Alexander Schiffmann, Kévin Rosset

Generic models are proposed to evaluate the skin friction coefficient acting on enclosed rotating disks and cylinders under various flow regimes. In particular, a model taking into account the inner radius of the disk is developed. The models are compared ...

2020

Dynamic force coefficients identification on air-lubricated herringbone grooved journal bearing

Jürg Alexander Schiffmann, Eliott Philippe Guenat

The Narrow Groove Theory (NGT) is commonly used to simulate and design grooved gas bearing. However, measurements of dynamic force coefficients of Herringbone Grooved Journal Bearings (HGJBs) is missing, hence the validation historic NGT has never been per ...

2020

A Review of Grooved Dynamic Gas Bearings

Jürg Alexander Schiffmann, Eliott Philippe Guenat, Lili Gu

This paper offers an extensive review of publications dealing with the modeling, the design and the experimental investigation of grooved dynamic gas lubricated bearings. Recent years have witnessed a rise in small-scale and high-speed turbomachinery appli ...

2020

Experimental Assessment of a 3D-Printed Stainless Steel Gas Foil Bearing

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Gas foil bearings (GFBs) are a key enabling technology for high-speed turbomachinery. The manufacturing of GFBs relies mainly on sheet metal forming techniques in order to conceive the compliant structure (e.g., bump foil) and the top foil. Such techniques ...

2020

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

Page 3 sur 6