Installed performance assessment of a boundary layer ingesting distributed propulsion system at design point

Boundary layer ingesting systems have been proposed as a concept with great potential for reducing the fuel consumption of conventional propulsion systems and the overall drag of an aircraft. These studies have indicated that if the aerodynamic and efficiency losses were minimised, the propulsion system demonstrated substantial power consumption benefits in comparison to equivalent propulsion systems operating in free stream flow. Previously assessed analytical methods for BLI simulation have been from an uninstalled perspective. This research will present the formulation of an rapid analytical method for preliminary design studies which evaluates the installed performance of a boundary layer ingesting system. The method uses boundary layer theory and one dimensional gas dynamics to assess the performance of an integrated system. The method was applied to a case study of the distributed propulsor array of a blended wing body aircraft. There was particular focus on assessment how local flow characteristics influence the performance of individual propulsors and the propulsion system as a whole. The application of the model show that the spanwise flow variation has a significant impact on the performance of the array as a whole. A clear optimum design point is identified which minimises the power consumption for an array with a fixed configuration and net propulsive force requirement. In addition, the sensitivity of the system to distortion related losses is determined and a point is identi ed where a conventional free-stream propulsor is the lower power option. Power saving coefficient for the configurations considered is estimated to lie in the region of 15%

Impact of environmental taxation policies on civil aviation - a techno-economic environmental risk assessment

Sustainability of the aviation industry, as any other industry, depends on the elasticity of demand for the product and profitability through minimising operating costs and hence assessing and understanding the interdependency and effects of environmentally optimised solutions and emission mitigation policies, is paramount. The contribution to knowledge, from this research, is the development and application of assessment methodologies to better understand the effects that future potential environmental taxation may have on the adaptation of optimised “greener” operations and novel technologies. These studies are undertaken using a Techno-economic Environmental Risk Assessment approach (TERA). The first methodology introduced to assess optimised operation methods (based on operating cost analysis), demonstrated that carbon taxation has limited effect if applied in isolation. Increasing it to extreme levels, apart from resulting in an increase in operational costs and raising governmental revenues, may not necessarily result in influencing an airline operator’s operational strategy to move to greener solutions. Instead, an application of a taxation level, commensurate to global standards, coupled with an improved air traffic management system, would allow aircraft to fly closer to their design efficiency and hence aid in reducing the environmental impact. The second methodology introduced (based on an operating and investment cost analysis) allows the assessment of the economic viability of a new technology in comparison to a conventional technology, when considered in terms of relative increase in acquisition price and maintenance costs, for various emission taxation and fuel price scenarios. A study undertaken as a ‘proof of concept’, comparing a Counter Rotating Open Rotor (CROR) aircraft with a conventional aircraft, indicates that at a current fuel price and no carbon taxation, despite being demonstrated as a highly fuel efficient technology, a relative increase in acquisition price and maintenance costs in comparison to the conventional aircraft, could render the CROR technology, economically unviable. The work further demonstrates that for the CROR technology to be economically beneficial, a simultaneous introduction of emission taxes may be required. The study shows that in order to achieve lower environmental impact, the implementation of taxation with the introduction of greener technologies will evidently increase the cost of civil aviation operation. This research subsequently identifies the following questions, more of a ‘political and socio-economic nature’, to consider as part of further work. If taxes above the global industry standards are introduced for the aviation industry, and they are higher in comparison to those applied on some other carbon intensive sectors, will it raise questions on equity of treatment? If taxation is introduced, airline operators and the ticket price paying passengers being amongst the key stakeholders in the aviation industry, will such high pricing as demonstrated be practical for long term sustenance? Will policies be driven by the fact that they will be aimed as a trade-off between achieving global sustenance of the industry and achieving environmental gain? Will high taxation as demonstrated, have global acceptance or will it have to be compromised, based on the growth potential or GDP of a country/ region