Development of an automated non-axisymmetric endwall contour design system for the rotor of a 1-stage research turbine – part 1: System design

2019 ◽  
Vol 234 (5) ◽  
pp. 565-581
Author(s):  
Jonathan Bergh ◽  
Glen Snedden ◽  
Daya Reddy
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Global Optimization ◽  
Secondary Flow ◽  
Optimization Procedure ◽  
Secondary Flows ◽  
Design System ◽  
Efficient Global Optimization ◽  
Optimization Approach ◽  
Blade Row

Secondary flows are a well-known source of loss in turbomachinery flows, contributing up to 30% of the total aerodynamic blade row loss. With the increase in pressure on aero-engine manufacturers to produce lighter, more powerful and increasingly more efficient engines, the mitigation of the losses associated with secondary flow has become significantly more important than in the past. This is because the production of secondary flow is closely related to the amount of loading and hence the work output of a blade row, which then allows part counts and overall engine weight to be reduced. Similarly, higher efficiency engines demand larger engine pressure ratios which in turn lead to reduced blade passage heights in which secondary flows then dominate. This article discusses the design and application of an automated turbine non-axisymmetric endwall contour optimization procedure for the rotor of a low speed, 1-stage research turbine, which was used as part of a research program to determine the most effective objective functions for reducing turbine secondary flows. In order to produce as effective as possible designs, the optimization procedure was coupled to a computational fluid dynamics routine with as high a degree of fidelity as possible and an efficient global optimization scheme based on the so-called efficient global optimization algorithm. In order to compliment the requirements of the efficient global optimization approach, as well as offset some of the computational requirements of the computational fluid dynamics, the DACE metamodel was used as an underlying surrogate model.

scholarly journals On- and off-design performance of a model rotating turbine with non-axisymmetric endwall contouring and a comparison to cascade data

2018 ◽  
Vol 122 (1250) ◽  
pp. 646-665 ◽  
Author(s):  
G. Snedden ◽  
D. Dunn ◽  
G. Ingram
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Secondary Flows ◽  
Objective Functions ◽  
Design Studies ◽  
Cascade Testing ◽  
Numerical Predictions ◽  
Blade Row ◽  
Hot Film ◽  
Isentropic Efficiency

ABSTRACTNon-axisymmetric endwalls in turbine stages have shown to be a robust method to improve the performance of turbines in both power generation and aero-derivative applications. Non-axisymmetric endwalls target the control of secondary flows and are designed using detailed computational fluid dynamics coupled with a variety of optimisation algorithms and utilising a number of objective functions according to the engine company or researcher's preference. These numerical predictions are often backed up by detailed measurements in linear and annular cascades and later proven in full-scale engine tests. Relatively little literature is available describing their performance in rotating test rigs or at conditions other than design, apart from that of the authors. This study comprehensively revisits the low-speed, model turbines used in the earlier study, replacing all of the 5-hole probe data with more accurate results and additional hot-film measurements. These results together with computational fluid dynamics solutions are used to show the success of the method across a large incidence range and to compare to earlier cascade results for a similar endwall and blade profile to establish the usefulness of cascade testing in this application. In addition, a comparison to two other off-design studies is made. Results indicate that the endwalls successfully improve the rotor total isentropic efficiency at all test conditions and that the improvement increases with increased turning in the blade row, from 0.5% to 1.8% across the incidence range. The results also compare well to the estimation of isentropic efficiency improvement that can be drawn from the cascade testing which stands at 1.55%.

scholarly journals Secondary Flow Control in Low Aspect Ratio Vanes Using Splitters

2016 ◽  
Author(s):  
Christopher Clark ◽  
Graham Pullan ◽  
Eric Curtis ◽  
Frederic Goenaga
Keyword(s):  
Kinetic Energy ◽  
Aspect Ratio ◽  
Secondary Flow ◽  
Current Practice ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Optimization Approach ◽  
Flow Strength ◽  
Low Aspect Ratio

Low aspect ratio vanes, often the result of overall engine architecture constraints, create strong secondary flows and high endwall loss. In this paper, a splitter concept is demonstrated that reduces secondary flow strength and improves stage performance. An analytic conceptual study, corroborated by inviscid computations, shows that the total secondary kinetic energy of the secondary flow vortices is reduced when the number of passages is increased and, for a given number of vanes, when the inlet endwall boundary layer is evenly distributed between the passages. Viscous computations show that, for this to be achieved in a splitter configuration, the pressure-side leg of the low aspect ratio vane horseshoe vortex, must enter the adjacent passage (and not “jump” in front of the splitter leading edge). For a target turbine application, four vane designs were produced using a multi-objective optimization approach. These designs represent: current practice for a low aspect ratio vane; a design exempt from thickness constraints; and two designs incorporating splitter vanes. Each geometry is tested experimentally, as a sector, within a low-speed turbine stage. The vane designs with splitters geometries were found to reduce the measured secondary kinetic energy, by up to 85%, to a value similar to the design exempt from thickness constraints. The resulting flowfield was also more uniform in both the circumferential and radial directions. One splitter design was selected for a full annulus test where a mixed-out loss reduction, compared to the current practice design, of 15.3% was measured and the stage efficiency increased by 0.88%.

The Application of Non-Axisymmetric Endwall Contouring in a Single Stage, Rotating Turbine

2009 ◽  
Author(s):  
Glen Snedden ◽  
Dwain Dunn ◽  
Grant Ingram ◽  
David Gregory-Smith
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Gradient ◽  
Full Scale ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Detailed Understanding ◽  
Low Speed ◽  
Endwall Contouring ◽  
Probe Measurements

As turbine manufacturers strive to develop machines that are more efficient, one area of focus has been the control of secondary flows. To a large extent these methods have been developed through the use of computational fluid dynamics and detailed measurements in linear and annular cascades and proven in full scale engine tests. This study utilises 5-hole probe measurements in a low speed, model turbine in conjunction with computational fluid dynamics to gain a more detailed understanding of the influence of a generic endwall design on the structure of secondary flows within the rotor. This work is aimed at understanding the influence of such endwalls on the structure of secondary flows in the presence of inlet skew, unsteadiness and rotational forces. Results indicate a 0.4% improvement in rotor efficiency as a result of the application of the generic non-axisymmetric endwall contouring. CFD results indicate a clear weakening of the cross passage pressure gradient, but there are also indications that custom endwalls could further improve the gains. Evidence of the influence of endwall contouring on tip clearance flows is also presented.

scholarly journals Using Splitters to Control Secondary Flow

2017 ◽  
Vol 139 (09) ◽  
pp. 58-59
Author(s):  
C. Clark ◽  
G. Pullan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Secondary Flow ◽  
Boundary Layers ◽  
Experimental Tests ◽  
Optimization Techniques ◽  
Automated Optimization

This article elaborates the concept of splitter vanes in controlling secondary flow. Secondary flow vortices are formed by the rotation of vorticity filaments, located in the endwall boundary layers, as the filaments move through the passage. The connection between the number of stators and the secondary kinetic energy suggests that the only way to significantly reduce the mixing loss is to increase the number of blades in the row. The designs evaluated were produced with fast turn-around computational fluid dynamics (10 minutes per solution) and automated optimization techniques. Experimental tests showed that the theory was correct, and that by increasing vane count, the secondary kinetic energy was reduced by up to 80%.

Design Optimization of Profiled Endwall With Consideration of Cooling and Rim Seal Flow Effects

2016 ◽  
Author(s):  
Huimin Tang ◽  
Shuaiqiang Liu ◽  
Hualing Luo
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Great Influence ◽  
Optimization Procedure ◽  
Secondary Flows ◽  
High Pressure Turbine ◽  
Operation Condition ◽  
Turbine Performance

Profiled endwall is an effective method to improve aerodynamic performance of turbine. This approach has been widely studied in the past decade on many engines. When automatic design optimisation is considered, most of the researches are usually based on the assumption of a simplified simulation model without considering cooling and rim seal flows. However, many researchers find out that some of the benefits achieved by optimization procedure are lost when applying the high-fidelity geometry configuration. Previously, an optimization procedure has been implemented by integrating the in-house geometry manipulator, a commercial three-dimensional CFD flow solver and the optimization driver, IsightTM. This optimization procedure has been executed [12] to design profiled endwalls for a turbine cascade and a one-and-half stage axial turbine. Improvements of the turbine performance have been achieved. As the profiled endwall is applied to a high pressure turbine, the problems of cooling and rim seal flows should be addressed. In this work, the effects of rim seal flow and cooling on the flow field of two-stage high pressure turbine have been presented. Three optimization runs are performed to design the profiled endwall of Rotor-One with different optimization model to consider the effects of rim flow and cooling separately. It is found that the rim seal flow has a significant impact on the flow field. The cooling is able to change the operation condition greatly, but barely affects the secondary flow in the turbine. The influences of the profiled endwalls on the flow field in turbine and cavities have been analyzed in detail. A significant reduction of secondary flows and corresponding increase of performance are achieved when taking account of the rim flows into the optimization. The traditional optimization mechanism of profiled endwall is to reduce the cross passage gradient, which has great influence on the strength of the secondary flow. However, with considering the rim seal flows, the profiled endwall improves the turbine performance mainly by controlling the path of rim seal flow. Then the optimization procedure with consideration of rim seal flow has also been applied to the design of the profiled endwall for Stator Two.

Identification of the Optimal Product Configuration and Parameters for Improving Manufacturability

1996 ◽  
Author(s):  
Deyi Xue
Keyword(s):  
Global Optimization ◽  
Optimization Methods ◽  
Product Configuration ◽  
Design System ◽  
Optimization Approach ◽  
Continuous Variables ◽  
Integer Variables ◽  
System A ◽  
Global Optimization Methods

Abstract A global optimization approach for identifying the optimal product configuration and parameters is proposed to improve manufacturability measures including feasibility, cost, and time of production. Different product configurations, including alternative design candidates and production processes, are represented by an AND/OR graph. Product parameters are described by variables including continuous variables, integer variables, Boolean variables, and discrete variables. Two global optimization methods, genetic algorithm and simulated annealing, are employed for identifying the optimal product configuration and parameters. The introduced approach serves as a key component in an integrated concurrent design system. A case study example is given to show how the proposed method is used for solving the engineering problems.

scholarly journals Effect of geometrical factors interactions on design optimization process of a natural gas ejector

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401988036
Author(s):  
Amin Hassan Amin ◽  
Ibrahim Elbadawy ◽  
E Elgendy ◽  
M Fatouh
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Natural Gas ◽  
Optimum Design ◽  
Average Error ◽  
Minor Effect ◽  
Optimization Approach ◽  
Entrainment Ratio ◽  
Geometrical Factors ◽  
Discharge Pressure

Enhancing the ejector entrainment ratio plays an important role in the ejector performance. In this article, a surrogate-based optimization approach along with computational fluid dynamics technique has been employed to optimize the entrainment ratio of a single-phase ejector working with natural gas. Nine ejector geometrical factors have been varied to maximize the ejector entrainment ratio. Validation results of the presented computational fluid dynamics model were in a good agreement with the experimental data from the literature with an average error of 0.6% in the critical mode. Reported results showed that the optimum design achieves entrainment ratio of 19.45% at 12, 2, and 5.2 MPa motive pressure, induced pressure, and discharge pressure, respectively. Moreover, the primary nozzle convergent angle and throat length are insignificant factors. Furthermore, secondary nozzle inclination angle has a minor effect on the entrainment ratio of the optimum design.

Optimal Arrangement Design of a Tube Bundle in Cross-Flow Using Computational Fluid Dynamics and Multi-Objective Genetic Algorithm

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Ya Ge ◽  
Feng Xin ◽  
Yao Pan ◽  
Zhichun Liu ◽  
Wei Liu
Keyword(s):  
Fluid Dynamics ◽  
Genetic Algorithm ◽  
Computational Fluid Dynamics ◽  
Pressure Drop ◽  
Tube Bundle ◽  
Optimal Solution ◽  
Optimization Procedure ◽  
Optimal Arrangement ◽  
Multi Objective ◽  
Multi Objective Genetic Algorithm

Recently, energy saving problem attracts increasing attention from researchers. This study aims to determine the optimal arrangement of a tube bundle to achieve the best overall performance. The multi-objective genetic algorithm (MOGA) is employed to determine the best configuration, where two objective functions, the average heat flux q and the pressure drop Δp, are selected to evaluate the performance and the consumption, respectively. Subsequently, a decision maker method, technique for order preference by similarity to an ideal solution (TOPSIS), is applied to determine the best compromise solution from noninferior solutions (Pareto solutions). In the optimization procedure, all the two-dimensional (2D) symmetric models are solved by the computational fluid dynamics (CFD) method. Results show that performances alter significantly as geometries of the tube bundle changes along the Pareto front. For the case 1 (using staggered arrangement as initial), the optimal q varies from 2708.27 W/m2 to 3641.25 W/m2 and the optimal Δp varies from 380.32 Pa to 1117.74 Pa, respectively. For the case 2 (using in-line arrangement as initial), the optimal q varies from 2047.56 W/m2 to 3217.22 W/m2 and the optimal Δp varies from 181.13 Pa to 674.21 Pa, respectively. Meanwhile, the comparison between the optimal solution with maximum q and the one selected by TOPSIS indicates that TOPSIS could reduce the pressure drop of the tube bundle without sacrificing too much heat transfer performance.

Effects of Inlet Temperature Gradients on Turbomachinery Performance

1975 ◽  
Vol 97 (1) ◽  
pp. 64-71 ◽  
Author(s):  
B. Lakshminarayana
Keyword(s):  
Combustion Chamber ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Secondary Flows ◽  
Temperature Gradients ◽  
Large Temperature ◽  
Inlet Temperature ◽  
Temperature Profiles ◽  
Blade Row

An analysis is carried out to predict the nature and magnitude of secondary flows induced by temperature gradients in turbomachinery stator and rotor. The effect of this thermal driven secondary flow is severe in gas turbines, due to large temperature gradients that exist at the outlet of the combustion chamber. Secondary flows change the temperature profiles at the exit of the blade row and generate thermal wakes. A method of incorporating these effects into the calculation of gas, blade and casing temperatures in a turbine is demonstrated through an example.

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