59206 - Improved Cfd Predictions of Pyrolysis Oil Combustion Using Advanced Spray Measurements and Numerical Models 

In search of an economical and environmentally friendly manner of power generation the industry is forced to find fuels which can replace conventional fossil fuels. During the last years this has led to significant developments in the production of alternative fuels, whereby these fuels became a more reliable and more efficient source of energy. Fast pyrolysis oil (FPO) is considered as a promising example of one of the alternative fuels. It is produced by means of fast pyrolysis process of biomass, which is thought to be one of the most promising techniques to transfer biomass into liquid fuels. However, when compared to conventional fuels, the produced FPO may have some drawbacks which complicate its application for power and heat generation. 

This research focusses on the application of FPO in a gas turbine combustion chamber and how the numerical predictions can be improved. For the OPRA OP16 gas turbine both an experimental and a numerical approach has been applied to a real scale gas turbine combustor. This includes full-scale combustor tests with various fuels, atomizer spray experiments and advanced CFD simulations. 

The droplet Sauter Mean Diameter (SMD) has been investigated by means of a dedicated atmospheric spray experiment. Particle Droplet Image Analysis was used to visualize the sprays in the near field of the atomizer determining the size of the droplets and ligaments, as well as their velocity. The effects of the spray pattern are of key importance to the flame structure in the gas turbine combustion chamber therefore the results from this dedicated test experiment have been used as input for dedicated CFD simulations. 

CFD based studies have been performed with a model pyrolysis oil on several flow parameters of the combustion chamber. A dedicated combustion model of fast pyrolysis oil has been developed for the OpenFoam code, considering both the evaporation of the oil and the burnout of the char. In the simulations both the cone angle and the droplet SMD of the spray where varied. The effect of these variations on the char conversion, the temperature field and the fuel conversion are investigated for various conditions, SMD and cone angles. These simulations provide a detailed insight and description on the evaporation of the pyrolysis oil and the flame characteristics in the combustion chamber of OPRA’s OP16. The CFD results obtained with the new model have been validated using data from a full-scale OP16 gas turbine combustor. 

In addition to the numerical work an experimental study was carried out in OPRA’s atmospheric combustion test cell in order to investigate the combustion of pyrolysis oil in a full-scale gas turbine combustor. Stable operation was achieved in the 30-100% load range, while running on pyrolysis oil only.