Determination of the isentropic turbine efficiency due to adiabatic measurements and the validation of the conditions via a new criterion

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The determination of the isentropic turbine efficiency under adiabatic and SAE boundary conditions is studied in this paper. The study is structured into two parts. The first part describes the possibility of measuring the isentropic turbine efficiency directly. Normally this is not possible in measurements conducted following the SAE J922 guidelines. Therefore, the experiments have been carried out under adiabatic conditions, and combined with improved measuring equipment. The results were compared with adiabatic computational fluid dynamics simulations of this turbocharger. In the second part, a new criterion is defined in order to evaluate the quality of the adiabatic measurements and compare them with standard measurements. The investigation has been carried out with multiple turbochargers ranging from very small to medium passenger car size turbochargers. In the end, a possible application for the criterion is given

Bidirectional flow measurement based on the differential pressure method for surge analysis on a small centrifugal compressor

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.To obtain a high temporal resolution of mass flow data, a flowmeter based on the differential pressure method has been developed. It is capable of detecting negative flow for investigations of dynamic effects in small centrifugal compressors used for turbocharging automotive internal combustion engines. Experiments were performed at a hot gas test bench focusing on the surge characteristics at different turbocharger speeds and the influence of volume modifications downstream of the compressor. Instantaneous operating points could be traced in the compressor map including the typical orbits at deep surge resulting from the cyclic character of the phenomenon

Geometric Optimization of Turbocharger Compressor and Its Influence on Engine Performance

This paper consists of two parts: aerodynamic and mechanical multi-objective optimization for centrifugal compressor impeller through combining the three dimensional fluid dynamic simulation module CFX 16.1, the static structure in the ANSYS Workbench and the optimization software optiSLang; and a comparison and analysis of the effects of the optimized compressor on the engine performance by the one dimensional simulation tool GT-Power. In the process of optimization, the compressor design point is regarded as the optimizing point, while impeller blades and hub line were parameterized through the Bezier curve. Pressure ratio, isentropic efficiency, quality and maximum deformation and maximum internal stress of the impeller were defined as the output conditions. MOP module was then adopted in optiSLang for the parameters sensitivity analysis and mapping relationship modeling between the impeller parameters and the objective functions. The genetic algorithm is applied to find out and validate the optimal design. Through 1D simulation tool GT-Power, the influence of the optimized compressor on rotational speed of the turbocharger, backpressure and pumping loss under different engine operating conditions is analyzed and compared

Activity Increase Despite Arthritis (AÏDA): design of a Phase II randomised controlled trial evaluating an active management booklet for hip and knee osteoarthritis [ISRCTN24554946]

<p>Abstract</p> <p>Background</p> <p>Hip and knee osteoarthritis is a common cause of pain and disability, which can be improved by exercise interventions. However, regular exercise is uncommon in this group because the low physical activity level in the general population is probably reduced even further by pain related fear of movement. The best method of encouraging increased activity in this patient group is not known. A booklet has been developed for patients with hip or knee osteoarthritis. It focuses on changing disadvantageous beliefs and encouraging increased physical activity.</p> <p>Methods/Design</p> <p>This paper describes the design of a Phase II randomised controlled trial (RCT) to test the effectiveness of this new booklet for patients with hip and knee osteoarthritis in influencing illness and treatment beliefs, and to assess the feasibility of conducting a larger definitive RCT in terms of health status and exercise behaviour. A computerised search of four general medical practice patients' record databases will identify patients older than 50 years of age who have consulted with hip or knee pain in the previous twelve months. A random sample of 120 will be invited to participate in the RCT comparing the new booklet with a control booklet, and we expect 100 to return final questionnaires. This trial will assess the feasibility of recruitment and randomisation, the suitability of the control intervention and outcome measurement tools, and will provide an estimate of effect size. Outcomes will include beliefs about hip and knee pain, beliefs about exercise, fear avoidance, level of physical activity, health status and health service costs. They will be measured at baseline, one month and three months.</p> <p>Discussion</p> <p>We discuss the merits of testing effectiveness in a phase II trial, in terms of intermediate outcome measures, whilst testing the processes for a larger definitive trial. We also discuss the advantages and disadvantages of testing the psychometric properties of the primary outcome measures concurrently with the trial.</p> <p>Trial registration</p> <p>Current Controlled Trials ISRCTN24554946</p

Geometric Optimization of Turbocharger Compressor and Its Influence on Engine Performance

This paper consists of two parts: aerodynamic and mechanical multi-objective optimization for centrifugal compressor impeller through combining the three dimensional fluid dynamic simulation module CFX 16.1, the static structure in the ANSYS Workbench and the optimization software optiSLang; and a comparison and analysis of the effects of the optimized compressor on the engine performance by the one dimensional simulation tool GT-Power. In the process of optimization, the compressor design point is regarded as the optimizing point, while impeller blades and hub line were parameterized through the Bezier curve. Pressure ratio, isentropic efficiency, quality and maximum deformation and maximum internal stress of the impeller were defined as the output conditions. MOP module was then adopted in optiSLang for the parameters sensitivity analysis and mapping relationship modeling between the impeller parameters and the objective functions. The genetic algorithm is applied to find out and validate the optimal design. Through 1D simulation tool GT-Power, the influence of the optimized compressor on rotational speed of the turbocharger, backpressure and pumping loss under different engine operating conditions is analyzed and compared

Geometric Optimization of Turbocharger Compressor and Its Influence on Engine Performance

This paper consists of two parts: aerodynamic and mechanical multi-objective optimization for centrifugal compressor impeller through combining the three dimensional fluid dynamic simulation module CFX 16.1, the static structure in the ANSYS Workbench and the optimization software optiSLang; and a comparison and analysis of the effects of the optimized compressor on the engine performance by the one dimensional simulation tool GT-Power. In the process of optimization, the compressor design point is regarded as the optimizing point, while impeller blades and hub line were parameterized through the Bezier curve. Pressure ratio, isentropic efficiency, quality and maximum deformation and maximum internal stress of the impeller were defined as the output conditions. MOP module was then adopted in optiSLang for the parameters sensitivity analysis and mapping relationship modeling between the impeller parameters and the objective functions. The genetic algorithm is applied to find out and validate the optimal design. Through 1D simulation tool GT-Power, the influence of the optimized compressor on rotational speed of the turbocharger, backpressure and pumping loss under different engine operating conditions is analyzed and compared

Turbocharger Heat Transfer Determination with a Power Based Phenomenological Approach and a CHT Validation

International audienceWe present from our work on models to determine heat flows on turbochargers. A Conjugate-Heat-Transfer simulation has been carried out on the turbine for validation of the approach. Results have shown that isentropic efficiencies fit well for values of turbine inlet temperatures of 600°C. For other temperatures the differences between the determined values and CHT are greater. e differences rise with higher temperatures. Hence, an additional dependency of turbine inlet temperatures has been implemented in the model. The modification has shown better results and smaller differences to CHT results. Especially at low speeds where the former approach has had big differences the modification improves the distribution. A wastegate turbocharger has been investigated from small gasoline engine applications. In future investigations the approach will be tested on the compressor with a modification, too, as well as on different turbochargers. The objective is to create a methodology for parameterization of a thermal network model based on the modified approach as a start point. Recently the experimental basis has been developed to determine heat flows on radial turbines and compressors. It has been validated for the compressor with experimental data under near adiabatic conditions. For the turbine a CFD simulation has been carried out. Both comparisons have shown good results for turbine inlet temperatures of 600°C

Challenges of turbocharging a two-cylinder engine : a computational analysis of a turbocharger turbine by transient CFD methods

Drive train development is facing demands for reduced emissions and growing expectations for driving dynamics coupled with declining fuel consumption. Downsizing in combination with turbocharging is a key technology to ensure increased power density and efficiency, at reduced emission levels. Up to now, quasi-steady behavior of the turbocharger has been assumed in the turbocharger design. However, the inflow conditions for radial turbines are actually quite different for real pulsating engine operations, compared to steady and quasi-steady conditions [1]. The aim of reducing the fuel consumption with fewer cylinders leads to a further change in the boundary conditions for the turbocharger [7]. As a result, the quasi-steady behavior, especially in two cylinder engines, does not seem to be valid and this has to be taken into account during the design process [2], [3]. This paper presents a numerical investigation of a pulse charged turbocharger turbine to gain an understanding of the aerodynamics at different pulse frequencies. A validated CFD-model is used to compute two and four-cylinder pulses. The time dependent boundary conditions for pressure and temperature are generated via 1D simulation. To make both pulse frequencies comparable, the turbine simulations were run with the same specific exhaust cycle enthalpy. The analyses of the results shows a significant deterioration of the turbine operating behavior at low end torque due to the pulsating inflow of a two cylinder pulse compared to a four cylinder pulse. Higher engine speeds reduce the disadvantages. Furthermore it can be shown that the storage effect of the volute and the phase shift in temperature and pressure influences the throughput behavior of the turbine. For that the specific pulsating flow conditions must be considered for an optimization of the turbocharger of a two-cylinder engine.Turboaufgeladene Vier-Zylinder-Motoren stellen weltweit den höchsten Anteil im Automobilbereich. Diese stehen auf Grund von Po-tentialen hinsichtlich Verbrauchsersparnis und Bauraum in Konkurrenz mit Drei-Zylinder-Motoren. Dem Trend folgend, wächst auch das Interesse an zweizylindrigen Motoren. Diese bringen neben mechanischen Eigenschaf-ten hinsichtlich Ungleichförmigkeiten bewegter Massen und Zündfolge auch deutlich geänderte Bedingungen am Abgasturbolader mit sich. Der pulsierende Einfluss bei Zwei-Zylindermotoren steigt und ändert damit vor allem die Randbedingungen der Turbine. In diesem Beitrag werden mit Hilfe numerischer Untersuchungen Verglei-che der Betriebsbedingungen einer Abgasturbolader-Turbine bei einem Zwei- und einem Vier-Zylinderbetrieb durchgeführt. Ziel der Studie ist es, die Unterschiede beider Motorarten auf das Betriebsverhalten der Turbine aufzuzeigen. Für die Randbedingungen des Modells werden die Ergebnisse eines, aus einer GT-Power-Simulation stammenden, Zwei-Zylinder-Modells verwendet. Als Ausgangsbedingung der CFD-Simulation (CFD= computati-onal fluid dynamics) wird die Turbine mit einem Zwei- bzw. Vier-Zylinderpuls beaufschlagt, wobei für beide Betriebszustände die gleiche spezifische Abgasenthalpie über einen Zyklus zur Verfügung gestellt wird. Auf diese Weise lassen sich die Pulsbedingungen eines kleinen Vier-Zylinder-Motors simulieren und mit denen eines Zwei-Zylinders verglei-chen. Die Ergebnisse zeigen, dass für eine Optimierung des Turboladers eines Zwei-Zylindermotors die Besonderheiten pulsierender Strömungsbe-dingungen berücksichtigt werden müssen