An Investigation of Applicability of Transporting Water Mist for Cooling Turbine Vanes
This paper presents a numerical study to investigate the feasibility of transporting mist through the internal cooling channel in high-pressure turbine vanes for film cooling over the vane’s surface. The idea of using mist film cooling to enhance conventional air cooling has been proven to be a feasible technique in the laboratory conditions and by computational simulations. However, there is a challenge to this technique to prove that the water mist can survive in the very hot environment inside the gas turbine casings and internal air passages and be delivered to the film injection holes. Both a zero-dimensional mist evaporation analytical model and 3-D computational fluid dynamic (CFD) scheme are employed for analysis. In the CFD simulation, the Lagrangian /Eulerian method is used along with the discrete phase model (DPM) to track the evaporation process of water droplets. The high-pressure water mist is injected into the stream of cooling air extracted from the compressor through the outer gas turbine casing near the vane before it reaches the vane internal cooling cavity. Using the mist equivalent of 10% of the cooling air mass flow rate, the results show that, when the liquid droplets are atomized to 30 μm in diameter initially, the droplets can survive inside the internal cooling passages and be delivered to the film cooling injection hole location with droplets of 20 μm in diameter; and alternatively, an initially 20 μm droplet can be delivered at 12μm in diameter, which is sufficiently large for completing the required external film cooling task.Copyright © 2012 by ASME
Mist/Air Cooling in a Two-Pass Rectangular Rotating Channel With 45-deg Angled Rib Turbulators
Increasing the turbine inlet temperature can increase the gas turbine cycle efficiency. In order to increase the turbine inlet temperature significantly, an advanced cooling system has to be essentially developed. Injection of mist to the coolant fluid is considered a promising technique to protect the hot components such as combustor liners, combustor transition pieces, and turbine vanes and blades. A series of experiments conducted in the past proved the success of mist cooling technology in the laboratory environment. Favorable results from the numerical simulation further encourage continuous exploration of employing mist-cooling technology in the actual gas turbine working environment in various applications. The present study focuses on applying mist cooling to the rotating mist/air internal cooling passage with rib turbulators using numerical simulation. In the first part, the computational fluid dynamics (CFD) models of smooth and ribbed channels without mist and rotation are validated with the experimental results available in literature. The agreement between the predicted and experimental values in the lower Reynolds number (Re) range is within 3% deviation, and, at higher Re range, the deviation is about 10%. For the smooth channel, the agreement with experimental result is good for the entire range of Re values. In the second part, the rotational effect on the smooth and ribbed channels is predicted and analyzed. In the last part, the mist cooling enhancement on the ribbed channel with rotation is simulated. The secondary flows created due to channel bend and rotation are specifically analyzed. The results show that the mist cooling enhancement is about 30% at the trailing surface and about 20% at the leading surface of the first passage with 2% mist injection. In the second passage, 20% enhancement is predicted for both the surfaces.Copyright © 2011 by ASME
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.