Experimental Comparison of Axial Turbine Performance Under Steady and Pulsating Flows

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
A. St. George ◽  
R. Driscoll ◽  
E. Gutmark ◽  
D. Munday
Keyword(s):  
Incidence Angle ◽  
Experimental Comparison ◽  
Strong Function ◽  
Axial Turbine ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Pulsed Detonation ◽  
Pulsed Flow ◽  
Partial Admission ◽  
Corrected Flow

The performance of an axial turbine is studied under close-coupled, out-of-phase, multiple-admission pulsed air flow to approximate turbine behavior under pulsed detonation inflow. The operating range has been mapped for four frequencies and compared using multiple averaging approaches and five formulations of efficiency. Steady performance data for full and partial admission are presented as a basis for comparison to the pulsed flow cases. While time-averaged methods are found to be unsuitable, mass-averaged, work-averaged, and integrated instantaneous methods yield physically meaningful values and comparable trends for all frequencies. Peak work-averaged efficiency for pulsed flow cases is within 5% of the peak steady, full admission values for all frequencies, in contrast to the roughly 15–20% performance deficit experienced under steady, 50% partial admission conditions. Turbine efficiency is found to be a strong function of corrected flow rate and mass-averaged rotor incidence angle, but only weakly dependent on frequency.

Experimental Comparison of Axial Turbine Performance Under Steady and Pulsating Flows

2014 ◽  
Author(s):  
A. St. George ◽  
R. Driscoll ◽  
E. Gutmark ◽  
D. Munday
Keyword(s):  
Incidence Angle ◽  
Experimental Comparison ◽  
Strong Function ◽  
Axial Turbine ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Pulsed Detonation ◽  
Pulsed Flow ◽  
Partial Admission ◽  
Corrected Flow

The performance of an axial turbine is studied under close-coupled, out-of-phase, multiple-admission pulsed air flow to approximate turbine behavior under pulsed detonation inflow. The operating range has been mapped for four frequencies and compared using multiple averaging approaches and five formulations of efficiency. Steady performance data for full and partial admission are presented as a basis for comparison to the pulsed flow cases. While time-averaged methods are found to be unsuitable, mass-averaged, work-averaged, and integrated instantaneous methods yield physically meaningful values and comparable trends for all frequencies. Peak work-averaged efficiency for pulsed flow cases is within 5% of the peak steady, full admission values for all frequencies, in contrast to the roughly 15–20% performance deficit experienced under steady, 50% partial admission conditions. Turbine efficiency is found to be a strong function of corrected flow rate and mass-averaged rotor incidence angle, but only weakly dependent on frequency.

Axial Turbine Performance Evaluation. Part B—Optimization With and Without Constraints

1968 ◽  
Vol 90 (4) ◽  
pp. 349-359 ◽  
Author(s):  
O. E. Balje´ ◽  
R. L. Binsley
Keyword(s):  
Reynolds Number ◽  
Performance Evaluation ◽  
Reference Value ◽  
Tip Clearance ◽  
Strong Function ◽  
Turbine Performance ◽  
Wide Range ◽  
Leakage Area ◽  
Partial Admission ◽  
Specific Speed

The maximum obtainable efficiency and associated geometry have been calculated based on the use of generalized loss correlations from Part A and are presented for full and partial admission turbines over a wide range of specific speeds. The calculated effects of varying values of Reynolds number, tip clearance, and trailing edge thickness on turbine performance are presented. Because of the anticipated difficulty in fabricating some of the optimum geometries calculated, the effects of using nonoptimum values of geometric parameters on attainable efficiency have also been investigated. The derating factor for machine Reynolds number is shown to be a strong function of specific speed, varying from 0.96 at a specific speed of 100, to 0.6 at a specific speed of 3, when Reynolds number is 105 compared to a reference value of 106. The derating factor for tip clearance is shown to be similar to what would be expected if the clearance area were considered as a leakage area. The use of blade heights, blade numbers, rotor exit angles, and degrees of reaction varying from the optimum by 25 percent produce maximum derating factors of 0.99, 0.98, 0.985, and 0.97, respectively, when compared to full optimum values.

Axial-Radial Diffuser With Integrated Exhaust Hood for An Automotive Turbocharger With Axial Turbine

2021 ◽  
Author(s):  
Christoph Kuestner ◽  
Joerg R. Seume
Keyword(s):  
Preliminary Design ◽  
Steam Turbines ◽  
Exhaust Hood ◽  
Design Guideline ◽  
Axial Turbine ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Turbine Design ◽  
Inflow Conditions ◽  
Turbine Exhaust

Abstract Exhaust hoods with an integrated axial-radial diffuser use the kinetic energy downstream of a turbine for static pressure recovery. This is especially useful in applications with limited axial space behind the turbine. So far, such exhaust hoods have been used almost exclusively in larger turbomachinery such as maritime turbochargers and steam turbines, where an axial turbine is typically installed. In combination with an axial turbine, an exhaust hood can result in a very powerful and space-efficient turbine design, especially under highly pulsating inflow conditions. Both are important requirements for automotive turbochargers. Therefore, the application of such an exhaust hood in a small automotive turbocharger is investigated in this paper; this turbocharger also uses an axial turbine. In the first step, a preliminary design is developed, based on a design approach for steam turbine exhaust hoods. The resulting design is examined with a 3D CFD model to determine efficiency and turbine performance. Subsequently, the design is improved by modifying the exhaust hood geometry such as to further improve the overall efficiency of the turbine. Finally, the CFD evaluation for the operating point investigated reveals an increased power output and a higher overall turbine efficiency compared to the initial design. A resulting design guideline for exhaust hoods with an integrated axial-radial diffuser is included.

The Effect of Stator-Rotor Hub Sealing Flow on the Mainstream Aerodynamics of a Turbine

2006 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Steady State ◽  
Entropy Generation ◽  
Flow Rate ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Flow Conditions ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Mainstream Flow ◽  
Flow Interactions

An investigation into the effect of stator-rotor hub gap sealing flow on turbine performance is presented. Efficiency measurements and rotor exit area traverse data from a low speed research turbine are reported. Tests carried out over a range of sealing flow conditions show that the turbine efficiency decreases with increasing sealant flow rate but that this penalty is reduced by swirling the sealant flow. Results from time-accurate and steady-state simulations using a three-dimensional multi-block RANS solver are presented with particular emphasis paid to the mechanisms of loss production. The contributions toward entropy generation of the mixing of the sealant fluid with the mainstream flow and of the perturbed rotor secondary flows are assessed. The importance of unsteady stator wake/sealant flow interactions is also highlighted.

The Effect of Clearance Flow of Variable Area Nozzles on Radial Turbine Performance

2008 ◽  
Author(s):  
Hideaki Tamaki ◽  
Shinya Goto ◽  
Masaru Unno ◽  
Akira Iwakami
Keyword(s):  
Flow Field ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Specific Work ◽  
Nozzle Vane ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Setting Angle ◽  
Clearance Flow ◽  
1D Model

The flow behind the variable area nozzle for radial turbines was measured with a 3-hole yaw probe and calculated with CFD. Two nozzle throat-areas were investigated: the smallest and the largest opening for the variable nozzle. Test results agreed with the calculated results qualitatively. The leakage flow through the tip clearance of the nozzle vane significantly affected the flow field downstream of the nozzle vane with the smallest opening. However, the effect on leakage flow on the flow field downstream of the nozzle vane with the largest opening was very weak. In the flow field of the largest opening nozzle, the effect of wake s dominant. The effect of the clearance of the nozzle vane on the turbine performance was estimated by a 1D-model and the strong influence on the turbine efficiency was confirmed at smallest opening. The flow fields in the impeller downstream of the nozzle vane at the smallest opening with and without the nozzle clearance were investigated with CFD. The setting angle of the nozzle vane without clearance was adjusted to match the operating point of the turbine with the nozzle clearance. In order to extract the specific work from the impeller, the nozzle vane with the vane clearance requires the larger vane setting angle than that without clearance. The increase of the vane setting angle increases the incidence loss and deteriorates turbine efficiency.

Pulse Converters—A Method of Improving the Performance of the Turbocharged Diesel Engine

1973 ◽  
Vol 187 (1) ◽  
pp. 635-647 ◽  
Author(s):  
M. S. Janota ◽  
N. Watson
Keyword(s):  
Pulse Generator ◽  
Test Results ◽  
Turbocharged Diesel Engine ◽  
Turbine Efficiency ◽  
Different Types ◽  
Partial Admission ◽  
Characteristics Analysis ◽  
Pulse Converter ◽  
Flow Loss ◽  
Loss Coefficients

Today, most turbocharged diesel engines operate on the pulse system. This is most effective on those engines whose exhaust manifolds can connect groups of three cylinders to a turbine entry without scavenging interference, e.g. three-, six-, nine- and twelve-cylinder engines. However, when only two cylinders can be connected to each turbine entry, e.g. four-, eight- and sixteen-cylinder engines, without interference, the system is usually less efficient. This is because the widely fluctuating, partial admission turbine conditions lower the average turbine efficiency. Recently, the pulse converter has been developed to improve the performance of such engines. A detailed investigation into the operation and application of the pulse converter has been conducted. Test results from three completely different types of engines showed substantial improvements in performance. The dependence of the pulse converter on engine speed and load, the effect of area variations in the pulse converter and the timing of the interfering exhaust pressure waves have been studied. A comparison of theoretically predicted and measured transient pressures (from a model pulse converter fitted to a pulse generator) was made. The theoretical analysis is based on empirical steady-flow loss coefficients and forms a boundary condition for a method of characteristics analysis. Results are compared with those predicted by the simple constant-pressure theory.

Unsteady Performance of a Double Entry Turbocharger Turbine With a Comparison to Steady Flow Conditions

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Colin D. Copeland ◽  
Ricardo Martinez-Botas ◽  
Martin Seiler
Keyword(s):  
Steady Flow ◽  
Flow Behavior ◽  
Turbine Rotor ◽  
Flow Conditions ◽  
Turbine Performance ◽  
Pulsed Flow ◽  
Performance Map ◽  
Engine Operating Condition ◽  
Double Entry ◽  
The Impact

Circumferentially divided, double entry turbocharger turbines are designed with a dividing wall parallel to the machine axis such that each entry feeds a separate 180 deg section of the nozzle circumference prior to entry into the rotor. This allows the exhaust pulses originating from the internal combustion exhaust to be preserved. Since the turbine is fed by two separate unsteady flows, the phase difference between the exhaust pulses entering the turbine rotor will produce a momentary imbalance in the flow conditions around the periphery of the turbine rotor. This research seeks to provide new insight into the impact of unsteadiness on turbine performance. The discrepancy between the pulsed flow behavior and that predicted by a typical steady flow performance map is a central issue considered in this work. In order to assess the performance deficit attributable to unequal admission, the steady flow conditions introduced in one inlet were varied with respect to the other. The results from these tests were then compared with unsteady, in-phase and out-of-phase pulsed flows most representative of the actual engine operating condition.

Unsteady Performance of a Double Entry Turbocharger Turbine With a Comparison to Steady Flow Conditions

2008 ◽  
Author(s):  
Colin D. Copeland ◽  
Ricardo Martinez-Botas ◽  
Martin Seiler
Keyword(s):  
Steady Flow ◽  
Turbine Rotor ◽  
Flow Conditions ◽  
Turbine Performance ◽  
Pulsed Flow ◽  
Performance Map ◽  
Unsteady Performance ◽  
Engine Operating Condition ◽  
Double Entry ◽  
The Impact

Circumferentially divided, double-entry turbocharger turbines are designed with a dividing wall parallel to the machine axis such that each entry feeds a separate 180° section of the nozzle circumference prior to entry into the rotor. This allows the exhaust pulses originating from the internal combustion exhaust to be preserved. Since the turbine is fed by two separate unsteady flows, the phase difference between the exhaust pulses entering the turbine rotor will produce a momentary imbalance in the flow conditions around the periphery of the turbine rotor. This research seeks to provide new insight into the impact of unsteadiness on turbine performance. The discrepancy between the pulsed flow behaviour and that predicted by a typical steady flow performance map is a central issue considered in this work. In order to assess the performance deficit attributable to unequal admission, the steady flow conditions introduced in one inlet were varied with respect to the other. The results from these tests were then compared to unsteady, in-phase and out-of-phase pulsed flow most representative of the actual engine operating condition.

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