Computation of unsteady turbomachinery flows: Part 1—Progress and challenges

Tucker, Paul G.

doi:10.1016/j.paerosci.2011.06.004

Cited by 110 publications

(55 citation statements)

References 144 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, high pressure turbines operate at both transonic Mach numbers and high Reynolds numbers, which impose great challenges to modern CFD. Conventional RANS and URANS methods have many difficulties in treating unsteady vortical flows in turbines [17][18][19][20] while DNS and LES are too costly [21] especially for high pressure turbines. High pressure turbine cascades had previously not been studied with high-fidelity numerical simulations until the works by Rathakrishnan Bhaskaran [22] with the help of LES.…”

Section: Introductionmentioning

confidence: 99%

Local Entropy Generation in Compressible Flow through a High Pressure Turbine with Delayed Detached Eddy Simulation

Lin

Yuan

Chen

2017

Entropy

View full text Add to dashboard Cite

Gas turbines are important energy-converting equipment in many industries. The flow inside gas turbines is very complicated and the knowledge about the flow loss mechanism is critical to the advanced design. The current design system heavily relies on empirical formulas or Reynolds Averaged Navier-Stokes (RANS), which faces big challenges in dealing with highly unsteady complex flow and accurately predicting flow losses. Further improving the efficiency needs more insights into the loss generation in gas turbines. Conventional Unsteady Reynolds Averaged Simulation (URANS) methods have defects in modeling multi-frequency, multi-length, highly unsteady flow, especially when mixing or separation occurs, while Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) are too costly for the high-Reynolds number flow. In this work, the Delayed Detached Eddy Simulation (DDES) method is used with a low-dissipation numerical scheme to capture the detailed flow structures of the complicated flow in a high pressure turbine guide vane. DDES accurately predicts the wake vortex behavior and produces much more details than RANS and URANS. The experimental findings of the wake vortex length characteristics, which RANS and URANS fail to predict, are successfully captured by DDES. Accurate flow simulation builds up a solid foundation for accurate losses prediction. Based on the detailed DDES results, loss analysis in terms of entropy generation rate is conducted from two aspects. The first aspect is to apportion losses by its physical resources: viscous irreversibility and heat transfer irreversibility. The viscous irreversibility is found to be much stronger than the heat transfer irreversibility in the flow. The second aspect is weighing the contributions of steady effects and unsteady effects. Losses due to unsteady effects account for a large part of total losses. Effects of unsteadiness should not be neglected in the flow physics study and design process.

show abstract

Section: Introductionmentioning

confidence: 99%

Local Entropy Generation in Compressible Flow through a High Pressure Turbine with Delayed Detached Eddy Simulation

Lin

Yuan

Chen

2017

Entropy

View full text Add to dashboard Cite

show abstract

“…The losses of exergy due to irreversibility are more accurately assessed by Equation (16) than by Equation (15). However, the contribution of the cascade to the output work is not taken into account by Equation (16). According to Equation (16), the optimized blade cascades should have low loading and work at a small incidence angle, thus the entropy generation can be minimized.…”

Section: Dimensionless Coefficients For Assessing Irreversible Processesmentioning

confidence: 99%

“…However, Kopriva et al [14,15] found that RANSs have much lower accuracy than large eddy simulations (LESs). Tucker [16,17] indicated that it is particularly difficult to predict unsteady separations in turbines with RANSs. As a compromise between the computational cost and the accuracy, Lin et al [18] studied the local entropy generation in a turbine cascade passage with a delayed detached eddy simulation (DDES) method.…”

Section: Introductionmentioning

confidence: 99%

Second-Law Analysis of Irreversible Losses in Gas Turbines

Jin

et al. 2017

Entropy

View full text Add to dashboard Cite

Several fundamental concepts with respect to the second-law analysis (SLA) of the turbulent flows in gas turbines are discussed in this study. Entropy and exergy equations for compressible/incompressible flows in a rotating/non-rotating frame have been derived. The exergy transformation efficiency of a gas turbine as well as the exergy transformation number for a single process step have been proposed. The exergy transformation number will indicate the overall performance of a single process in a gas turbine, including the local irreversible losses in it and its contribution to the exergy obtained the combustion chamber. A more general formula for calculating local entropy generation rate densities is suggested. A test case of a compressor cascade has been employed to demonstrate the application of the developed concepts.

show abstract

“…Understanding, designing and optimizing flows is crucial, e.g., for improving fuel injections [1], combustions [2,3], fuel cells [4], wind turbines [5], turbomachines [6], human air and blood flows in medicine [7,8], as well as for the fundamental task of modeling flow turbulence [9]. For this purpose, optical measurement methods are essential tools that promise fast and precise field measurements of complex flows.…”

Section: Introductionmentioning

confidence: 99%

Imaging Flow Velocimetry with Laser Mie Scattering

Fischer

2017

Applied Sciences

View full text Add to dashboard Cite

Abstract:Imaging flow velocity measurements are essential for the investigation of unsteady complex flow phenomena, e.g., in turbomachines, injectors and combustors. The direct optical measurement on fluid molecules is possible with laser Rayleigh scattering and the Doppler effect. However, the small scattering cross-section results in a low signal to noise ratio, which hinders time-resolved measurements of the flow field. For this reason, the signal to noise ratio is increased by using laser Mie scattering on micrometer-sized particles that follow the flow with negligible slip. Finally, the ongoing development of powerful lasers and fast, sensitive cameras has boosted the performance of several imaging methods for flow velocimetry. The article describes the different flow measurement principles, as well as the fundamental physical measurement limits. Furthermore, the evolution to an imaging technique is outlined for each measurement principle by reviewing recent advances and applications. As a result, the progress, the challenges and the perspectives for high-speed imaging flow velocimetry are considered.

show abstract

Computation of unsteady turbomachinery flows: Part 1—Progress and challenges

Cited by 110 publications

References 144 publications

Local Entropy Generation in Compressible Flow through a High Pressure Turbine with Delayed Detached Eddy Simulation

Local Entropy Generation in Compressible Flow through a High Pressure Turbine with Delayed Detached Eddy Simulation

Second-Law Analysis of Irreversible Losses in Gas Turbines

Imaging Flow Velocimetry with Laser Mie Scattering

Contact Info

Product

Resources

About