Transient performance of the mixed flow and radial flow variable geometry turbines for an automotive turbocharger (original) (raw)
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Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2018
A new design of a mixed flow variable geometry turbine is developed for the turbocharger used in diesel engines having the cylinder capacity from 1.0 to 1.5 L. An equivalent size radial flow variable geometry turbine is considered as the reference for the purpose of bench-marking. For both the radial and mixed flow turbines, turbocharger components are manufactured and a test rig is developed with them to carry out performance analysis. Steady-state turbine experiments are conducted with various openings of the nozzle vanes, turbine speeds, and expansion ratios. Typical performance parameters like turbine mass flow parameter, combined turbine efficiency, velocity ratio, and specific speed are compared for both mixed flow variable geometry turbine and radial flow variable geometry turbine. The typical value of combined turbine efficiency (defined as the product of isentropic efficiency and the mechanical efficiency) of the mixed flow variable geometry turbine is found to be about 25%...
Variable Geometry Mixed Flow Turbine for Turbochargers: An Experimental Study
International Journal of Fluid Machinery and Systems, 2008
This paper investigates a variable geometry (VG) mixed flow turbine with a novel, purposely designed pivoting nozzle vane ring. The nozzle vane ring was matched to the 3-dimensional aspect of the mixed flow rotor leading edge with lean stacking. It was found that for a nozzle vane ring in a volute, the vane surface pressure is highly affected by the flow in the volute rather than the adjacent vane surface interactions, especially at closer nozzle positions. The performance of the VG mixed flow turbine has been evaluated experimentally in steady and unsteady flow conditions. The VG mixed flow turbine shows higher peak efficiency and swallowing capacity at various vane angle settings compared to an equivalent nozzleless turbine. Comparison with an equivalent straight vane arrangement shows a higher swallowing capacity but similar efficiencies. The VG turbine unsteady performance was found to deviate substantially from the quasi-steady assumption compared to a nozzleless turbine. This is more evident in the higher vane angle settings (smaller nozzle passage), where there are high possibility of choking during a pulse cycle. The presented steady and unsteady results are expected to be beneficial in the design of variable geometry turbochargers, especially the ones with a mixed flow turbine.
Mixed-flow turbines for automotive turbochargers: steady and unsteady performance
International Journal of Engine Research, 2002
Turbochargers are finding increasing appliincreasingly more stringent emission standards. This cation to automotive diesel engines as cost effective means paper is part of an extensive experimental profor improving their power output and efficiency, and gramme focused on turbine design technology for reducing exhaust emissions; these requirements have led vehicle applications aiming to (a) explore available to the need for highly loaded turbocharger turbines. A means to modify the turbine operating characteristics mixed-flow turbine is capable of achieving its peak isen-in order to improve the engine/turbocharger matchtropic efficiency at reduced velocity ratios compared to a ing and (b) improve the transfer of energy from the typical radial inflow turbine; it is therefore possible to pulsating exhaust gases to the turbine. In order to improve the turbocharger/engine matching. These turbines achieve these aims, the project is centred on mixeddiffer from the commonly used radial turbines in that the flow turbine rotors as opposed to radial rotors comflow approaches the rotor in the non-radial direction; in monly used in automotive turbochargers. This choice the extreme a mixed-flow turbine would become an axial overcomes one of the principal limitations of the machine. The steady and unsteady performances of a radial inflow turbine, where stress and material conmixed-flow turbocharger turbine with a constant blade siderations dictate that the blade angle must be zero inlet angle have been investigated. The steady flow results to maintain radial blade sections and to keep the indicated that the mixed-flow turbine obtains a peak centrifugal load in the blades purely tensile. A efficiency (total-to-static) of 75 per cent at a velocity ratio mixed-flow geometry permits the use of a non-zero of 0.61, compared with that of a typical radial-inflow turblade angle without departure from the above bine which peaks at a velocity ratio of 0.7. The performance requirement and introduces an extra degree of freeand flow characteristics were found to deviate significantly dom into the rotor design, which has particular from the equivalent steady state values commonly used in implications for the range of operation of the turbine, turbocharger turbine design.
Simulation of the Performance of a Variable Geometry Turbocharger for Diesel Engine Road Propulsion
Advanced research work has lead to the development of a new simulation program and the thermodynamic parameters at engine inlet and exhaust of an engine-mounted variable-geometry turbine can thus be evaluated. The machine is divided into characteristic sub-blocks and resolution of thermomechanical flow equations is carried out using the necessary geometrical parameters. A detailed study of losses is conducted experimentally and numerically into the scroll, the vaned nozzle and the rotor in relation to nozzle opening angles. Simulation results made on the variable geometry turbine are analyzed in relation to main flow entry parameters and are compared systematically with experimental data gathered on turbocharger test equipment, and on a Diesel engine used for industrial applications.
Performance of a Mixed Flow Turbocharger Turbine Under Pulsating Flow Conditions
Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery, 1995
The performance of a high pressure ratio (P.R.=2.9) mixed flow turbine for an automotive turbocharger has been investigated and the results revealed its better performance relative to a radial-inflow geometry under both steady and pulsating flow conditions. The advantages offered by the constant blade angle rotor allow better turbocharger-engine matching and maximization of the energy extracted from the pulsating engine exhaust gases. In particular, the mixed inlet blade geometry resulted in high efficiency at high expansion ratios where the engine-exhaust pulse energy is maximum. The efficiency characteristics of the mixed flow turbine under steady conditions were found to be fairly uniform when plotted against the velocity ratio, with a peak efficiency at the design speed of 0.75. The unsteady performance as indicated by the mass-averaged total-to-static efficiency and the swallowing capacity exhibited a departure from the quasi-steady assumption which is analysed and discussed.
Development of a Variable Area Radial Turbine for Small Turbochargers
Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery, 1988
This paper summarizes the development of variable area radial turbines for small turbochargers, intended for passenger car applications. Comparisons of aerodynamic performance of several different kinds of variable radial inflow turbines are discussed. The results of comparative performance evaluations indicate the scroll area control type (VI) is the most suitable design for small turbochargers, where performance, cost and durability are the major design considerations.
Conceptual Design of a Variable Geometry, Axial Flow Turbocharger Turbine
SAE Technical Paper Series
The modern automotive industry is under strict regulations to reduce emissions to comply with the Kyoto Protocol, a universally acknowledged treaty aiming at reducing exhaust gas emissions. In order to achieve the required future emission reduction targets, further developments on gasoline engines are required. One of the main methods to achieve this goal is the application of engine downsizing. Turbocharging is a cost-effective method of downsizing an engine whilst reducing exhaust gas emissions, reducing fuel consumption and maintaining prior performance outputs. For these reasons, the turbocharging is becoming the most widely adopted technology in the automotive markets. In 2012, 32% of passenger and commercial vehicles sold had a turbocharger installed, and is predicted to be 40% of 2017 [1]. Even if the engine turbocharging is a widespread technology, there are still drawbacks present in current turbocharging systems. The main problem is overcoming the issue of turbo-lag, which is the poor initial response of the turbocharger to the driver commands due to its inertia. Indeed, the system turbine plus compressor is characterized by an own rotational inertia, therefore, the turbocharger will take a certain time to accelerate and produce the desired boost when a higher amount of exhaust gas is sent to the system. In this work, an innovative solution to the turbo-lag phenomenon will be analyzed: a vaneless stator-axial flow turbine. The proposed turbine configuration would improve the transient response of the system since the axial turbine has intrinsically a lower inertia than the radial turbine as stated by the research works of Ford first [2] and Honeywell after [3]. The whole design process is presented in this paper and particular relevance has been given to the thermo-fluid-dynamic aspect of the machine. Several CFD investigations have been carried out in order to deeply understand the new turbine behavior and, thanks to a 1D model of the target engine, it has been possible to validate the new design simulating the performance of the system engine + turbocharger.
Energy, 2011
In the paper the results of an experimental investigation developed on a small turbocharger turbine for automotive application are presented, including the effect of the waste-gate valve opening. The study was focused on the evaluation of turbine efficiency, especially under unsteady flow conditions typically occurring in automotive turbocharged engines. Turbine efficiency values measured under steady and pulsating flow conditions are compared, also considering a quasi-steady flow approach.
Unsteady performance analysis of a twin-entry variable geometry turbocharger turbine
Energy, 2012
This paper discusses the details of unsteady experimentation and analysis of a twin-entry variable geometry turbine for an automotive turbocharger. The turbine in this study is the product of design progression from a commercial nozzleless unit to a single-entry variable geometry and consequently to a twin-entry unit. The main features of the turbine were kept similar across all configurations for equivalent comparison basis. The unsteady curves of the twin-entry turbine exhibited the conventional looping characteristics representing filling and emptying effects, which was also the case for the nozzleless and single-entry nozzled turbine. The swallowing capacity of the twin-entry turbine, during full admission testing, was recorded to be inconsistent between the two entries, in particular they were at different pressure ratio levels e the shroud end entry was in most cases more pressurized compared to the hub end entry, as much as 13%. Contrarily, during out-of-phase testing the swallowing capacity of both the turbine entries was found to be similar. The cycle-averaged efficiency of the nozzled turbine either twin or single-entry was found to depart significantly from the equivalent quasi-steady, in comparison to the nozzleless single-entry turbine, this was as much as 32%.