Simon Blakey

Sustainability of supply or the planet: a review of potential drop-in alternative aviation fuels

The development of kerosene-like drop-in alternative aircraft fuels can be categorised into two groups, depending on whether the product increases supply security or provides a reduced environmental footprint. This paper uncovers this relationship through a review of commercially available process technologies (Fischer Tropsch and hydroprocessing) to produce alternative fuels, lifecycle results and recent flight test campaigns, before evaluating the prospects for future fuel development. Supply may be improved through the conversion of coal (with carbon sequestration) or natural gas using the Fischer Tropsch process. Refinement of these alternative fossil fuels, however, provides comparable total life cycle emissions to Jet A-1. The hydroprocessing of biomass feedstock provides for a reduced environmental footprint—approximately 30% reduction for sustainable cultivated feedstock, when blended 50/50 with conventional jet fuel. However, securing supply is a significant issue. Considering aviation is responsible for 2.6% of global CO2 emissions, converting 6% of arable land (representing 0.95% of the earth surface) to supply a 50/50 blend, thus offsetting 0.78% of global CO2 emissions, seems impractical based upon the current land use scenario. Furthermore, ground based sectors have significant environmental footprints compared to aviation, yet require little pre-processing of feedstock (i.e. power generation can burn raw feedstock), thus presenting a better biomass opportunity cost.

Impact of Alternative Fuels on Emissions Characteristics of a Gas Turbine Engine ? Part 1: Gaseous and Particulate Matter Emissions

Growing concern over emissions from increased airport operations has resulted in a need to assess the impact of aviation related activities on local air quality in and around airports, and to develop strategies to mitigate these effects. One such strategy being investigated is the use of alternative fuels in aircraft engines and auxiliary power units (APUs) as a means to diversify fuel supplies and reduce emissions. This paper summarizes the results of a study to characterize the emissions of an APU, a small gas turbine engine, burning conventional Jet A-1, a fully synthetic jet fuel, and other alternative fuels with varying compositions. Gas phase emissions were measured at the engine exit plane while PM emissions were recorded at the exit plane as well as 10 m downstream of the engine. Five percent reduction in NO(x) emissions and 5-10% reduction in CO emissions were observed for the alternative fuels. Significant reductions in PM emissions at the engine exit plane were achieved with the alternative fuels. However, as the exhaust plume expanded and cooled, organic species were found to condense on the PM. This increase in organic PM elevated the PM mass but had little impact on PM number.

Polycyclic Aromatic Hydrocarbon Emissions from the Combustion of Alternative Fuels in a Gas Turbine Engine

We report on the particulate-bound polycyclic aromatic hydrocarbons (PAH) in the exhaust of a test-bed gas turbine engine when powered by Jet A-1 aviation fuel and a number of alternative fuels: Sasol fully synthetic jet fuel (FSJF), Shell gas-to-liquid (GTL) kerosene, and Jet A-1/GTL 50:50 blended kerosene. The concentration of PAH compounds in the exhaust emissions vary greatly between fuels. Combustion of FSJF produces the greatest total concentration of PAH compounds while combustion of GTL produces the least. However, when PAHs in the exhaust sample are measured in terms of the regulatory marker compound benzo[a]pyrene, then all of the alternative fuels emit a lower concentration of PAH in comparison to Jet A-1. Emissions from the combustion of Jet A-1/GTL blended kerosene were found to have a disproportionately low concentration of PAHs and appear to inherit a greater proportion of the GTL emission characteristics than would be expected from volume fraction alone. The data imply the presence of a nonlinear relation between fuel blend composition and the emission of PAH compounds. For each of the fuels, the speciation of PAH compounds present in the exhaust emissions were found to be remarkably similar (R(2) = 0.94-0.62), and the results do provide evidence to support the premise that PAH speciation is to some extent indicative of the emission source. In contrast, no correlation was found between the PAH species present in the fuel with those subsequently emitted in the exhaust. The results strongly suggests that local air quality measured in terms of the particulate-bound PAH burden could be significantly improved by the use of GTL kerosene either blended with or in place of Jet A-1 kerosene.

The effect of wall emissivity on radiator heat output

The variation in the heat output of panel radiators obtained by altering the emissivity of the wall behind them has been examined. This work was conducted through experiments and Computational Fluid Dynamics (CFD). The results indicate that the presence of a high emissivity (black, such as the usual painted or wallpapered) surface to the wall increases the mass flow rate and air velocity behind the heat source compared to a reflective material. This is due to the radiation heat transfer to the wall creating an additional convecting surface behind the radiator. The results imply that the heat transfer rate can be increased by 20% through the use of a black instead of a reflective wall. The work concentrated on the air-gap behind the radiator, so these results will not be directly applicable to a normal radiator. An extrapolation indicates that the output of single bank (plate) radiator will be increased by 10% and a double radiator by 5%. Wall surface temperature results indicate that a reflective wall does indeed decrease the heat loss through the wall. The trend shown in the data obtained from the CFD analysis agreed well with the experimental results. The flow and temperature plots obtained from the CFD work help to explain the heat exchange and fluid flow processes that take place between the radiator and the wall. This understanding should lead the engineer to a better consideration of radiator placement and design.

Inadequacy of Optical Smoke Measurements for Characterization of Non–Light Absorbing Particulate Matter Emissions from Gas Turbine Engines

Analysis of particulate matter (PM) emissions from gas turbine engines, using the conventional smoke number (SN) technique, provides a measure of plume visibility. In this study, PM emissions were sampled from the exhaust of a small gas turbine engine, burning Jet A-1, and Biodiesel. SN results indicated that biodiesel significantly reduced visible emissions. Analysis of PM number and mass concentrations using a differential mobility spectrometer found that although nonvolatile PM was significantly reduced, biodiesel combustion produced a high fraction of volatile PM. Concurrent aerosol mass spectrometer measurements established that the condensable material was organic in composition. The condensation of volatile organics, not captured by the SN technique, significantly increased the total PM emissions. Application of the Society of Automotive Engineers Aerospace Recommended Practice 1179d for gas turbine engines is limited to visible plume characterization and thus is inadequate when combustion produces a large fraction of volatile or non–light absorbing PM emissions.

Energy consumption and capacity utilization of galvanizing furnaces

Abstract An explicit equation leading to a method for improving furnace efficiency is presented. This equation is dimensionless and can be applied to furnaces of any size and fuel type for the purposes of comparison. The implications for current furnace design are discussed. Currently the technique most commonly used to reduce energy consumption in galvanizing furnaces is to increase burner turndown. This is shown by the analysis presented here actually to worsen the thermal efficiency of the furnace, particularly at low levels of capacity utilization. Galvanizing furnaces are different to many furnaces used within industry, as a quantity of material (in this case zinc) is kept molten within the furnace at all times, even outside production periods. The dimensionless analysis can, however, be applied to furnaces with the same operational function as a galvanizing furnace, such as some furnaces utilized within the glass industry.

Genetic Algorithm optimised Chemical Reactors network: A novel technique for alternative fuels emission prediction

Abstract Sustainability of the conventional jet fuels and climate change has attracted the aviation sector to diversity to alternative fuels. However, fuel diversification requires an assessment of the long term impact to engine performance and engine emissions through the combustion process, as alternative fuels are not as well understood as conventional jet fuel. A detailed experimental study on alternative fuels emissions across the entire aircraft fleet is impractical. Therefore a plausible method of computer modelling combined Genetic Algorithm and Chemical Reactors network was developed to predict alternative fuels gaseous emissions, namely, Carbon Monoxide, Nitrogen Oxides and Unburned Hydrocarbons in aircraft engines. To evaluate the feasibility and accuracy of the technique, exhaust emission measurements were performed on a re-commissioned Artouste Mk113 Auxiliary Power Unit, located at the University of Sheffield׳s Low Carbon Combustion Centre. The simulation produced results with good agreements with the experimental data. The optimised model was used to extrapolate emissions data from different blends of alternative fuels that did not operate during the campaign. The proposed technique showed that it can develop a data base of alternative fuels emissions and also act as a guideline for alternative fuels development.

Preliminary Calculations on Post Combustion Carbon Capture From Gas Turbines With Flue Gas Recycle

Carbon capture is getting increased attention recently due to the fact that it seems to be the only answer to decrease emissions. Gas turbines exhaust have 3–5 % concentration of CO2 which is very low to be captured by an amine carbon capture plant effectively. The amine based plants are most effective at around 10 – 15% CO2 in the flue gas. In order to increase the concentration of CO2 in the exhaust of the gas turbine, part of the exhaust gas needs to be recycled back to the air inlet. On reaching the concentration of CO2 around 10% it can be fed to the amine capture plant for effective carbon capture.A 100 kWe (plus 150 kW hot water) CHP gas turbine Turbec T100 is installed at the Low Carbon Combustion Centre of the University of Sheffield. The turbine set up will be modified to make it CO2 capture ready. The exhaust gases obtained will be piped to amine capture plant for testing capture efficiency. Preliminary calculations have been done and presented in this paper. The thermodynamic properties of CO2 are different from nitrogen and will have an effect on compressor, combustor and turbine performance. Preliminary calculations of recycle ratios and other performance based parameters have been presented in this paper. This paper also covers the aspects of turbine set up machinery which needs to be modified and what kind of modifications may be needed.Copyright

Development of an Apparatus for the Degradation of Aviation Gas Turbine Lubricants

The capabilities of the Lubricant System Interaction Simulator (LSIS) are demonstrated by presenting the results from a 1,000-h thermal oxidative degradation test of an MIL-PRF-23699F lubricant. These results are compared with data from two in-service gas turbine engines using the same oil but under different conditions so that a range of operating regimes can be represented. The results showed that the viscosity changed, in accordance with the two engines, from 26.5 to 28.3 mm2/s. The change in total acid number was higher than expected, identifying areas for improvement. The antioxidant level reached 30%, which is between the 25 and 45% levels observed from the two engines. The antiwear and metal deactivator additives reached steady-state concentration levels of 95 and 20%, respectively. The results obtained from this test verified the significant potential of this facility as a reliable means of testing lubricants in an environment that is closely related to gas turbine lubrication system operating conditions.

Squeezability. Part 1: a pressing issue

Abstract Within the UK it is estimated that by 2020 over half the adult population will be over 50. A society in which the majority are aged poses some interesting questions, not least how that society will use and access goods and services, when the majority are likely to experience some loss of strength and dexterity. One such issue, the openability or accessibility of packaging, is becoming a major issue for brand owners, manufacturers, designers, and engineers due to the rapid ageing of much of the developed world. The authors have previously undertaken a significant amount of work on understanding the openability of vacuum lug closures (jam or sauce jars). This work looked at the forces to keep the system closed, the forces a human could apply and used experimental, numerical, and analytical analysis to understand these systems. Packaging, however, comes in many varied and differing forms and little or no previous work has been undertaken in this field on other forms of packaging such as thin film packets or bottles. The work in this article applies the principles used in the earlier studies to the squeezable bottle pack format. The article describes initial experimental and analytical work undertaken from first principals to establish the factors that contribute to the ease of use along with various laboratory tests carried out in order to determine the design rules for developing bottle styles and nozzle designs, for specific fluid contents. The work suggested several things that may be important for designers and manufacturers of squeezable bottles. Fundamental analysis shows that bottle material and shape generally dominate the squeezeability of and access to bottle contents. Bottle shape was seen to affect performance with the conditioner bottle having the best volume—deflection performance. Work also showed that hole size and Borda length can be calculated to determine specific flow characteristics with a relatively simple set of equations.