Research

Pulsating turbine impact

The phenomena of pulsating turbine impact in exhaust gas turbochargers leads to uncertainties when designing these important components. Owing to their efficiency increasing effect, these can be found in many combustion engines, e.g. in the diesel and gasoline engines of cars. The project goal was to examine the relationship between stationary engine characteristics and the turbocharger turbine's real flow in engine operation. Both the results of the measurements as well as the CFD (Computational Fluid Dynamics) simulation show that the impeller from an internal engine viewpoint behaves in an almost steady fashion and only the volute – the area of the flow – is responsible for the pulsation effects. It could be inferred from the 1-D-engine process calculation that pulsation effects could be considered with sufficient preciseness by depicting volute as a pressure volume without loss and by using stationary engine characteristics.

» We've made an important contribution to understanding the pulsation effects in turbocharger turbines. With our recommended calculations we can realistically forecast the behaviour of turbochargers and thus design them more efficiently. «
Dr. Panagiotis Grigoriadis (IAV GmbH)

Motivation

Exhaust turbocharging has established itself as a key technology with diesel engines and has also become standard meanwhile in gasoline engines as well. The charging process involves pulsating inflow of turbines – which together with the compressor is a main turbocharger component. Until now the phenomena of pulsating turbine inflow has not been clear. The goal of the project was to analyse the variation between the characteristics determined at the turbocharger test rig at stationary conditions and the operating values determined in the pulsating engine test.

Methodology

The basis for the tests was the test bench trials. In order to collect the pulsation effects, extensive measurement technology was necessary, e.g. to determine the torque. Through almost adiabatic conditions it was possible to determine the isentropic turbine efficiency. In this way it was possible during measurements to concentrate fully on the turbine aerodynamics and to isolate the pulsating effects. Using 1-D simulation, an approach for depicting the pulsating flow was developed. As part of the CFD examination an analysis of the turbine's aerodynamic occurred.

Result

The measurements and CFD simulation show that the impeller behaved almost completely in a steady fashion and pulsating effects mainly take place in the volute in the form of reverberation and energy storage. The pulsation amplitude decreases with increasing frequency, whereas the gradient increases. The 1-D simulation indicates that the pulsating flow could be depicted with sufficient precision by using volute as pressure loss-free volume. By integrating the volute volume in the engine process simulation along with the stationary engine characteristics, turbine efficiency could be reproduced realistically. In the project it was also possible to prove that pulsation has a significant impact on the course of the axial force and thus probably on frictional power.

Documentation

Pulsating turbine flow | Efficiency of turbocharger turbine at admission with pulsating exhaust gas flow | Project No. 1103

Themis

Status
Finalised

Programme
Public Funding

Budget
300.000,00 EUR

Time Period
2012-03-01 to 2014-12-31

German Federation of Industrial Research Associations (AiF) e. V.

Bayenthalgürtel 23
50968 Cologne
Germany

Federal Ministry for Economic Affairs and Energy (BMWi)

Scharnhorststrasse 34-37
10115 Berlin
Germany

Industrie

Dr. Panagiotis Grigoriadis
IAV GmbH

Forschungsstellen

1 | Division of Automotive Engineering and Internal Combustion Engines (FZA), Institute of Land and Sea Transport Systems (ILS), Department of Mechanical Engineering and Transport Systems (VM) - Technische Universität Berlin

Head of Research:
Prof. Dr.-Ing. Roland Baar

2 | Institute of Fluid Dynamics and Technical Acoustics (ISTA), Technische Universität Berlin

Head of Research:
Prof. Dr. Lars Enghardt

3 | Engine Acoustics (TRA), Institute of Propulsion Technology (AT), German Aerospace Center (DLR) eV

Head of Research:
Prof. Dr. Lars Enghardt

Technische Universitaet Berlin

Institute of Fluid Dynamics and Technical Acoustics (ISTA) Propulsion Technology, Engine Acoustic

Müller-Breslau-Str. 8
10623 Berlin
Germany

Aeronautics and space research centre of Germany

Institute of Propulsion Technology

Linder Höhe
51147 Cologne
Germany

Project Management

Ralf Thee

FVV
+49 (0) 69 6603 1349
+49 (0) 69 6603 2349

Research Association for Combustion Engines eV

Lyoner Strasse 18
60528 Frankfurt am Main
Germany
T +49 69 6603 1345