Browse Topic: Exhaust emissions
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Time-resolved background-oriented schlieren (BOS) data are used to calculate the two-dimensional velocity field in the wake of free-flying full-scale helicopters in ground effect. The calculation is performed based on the density gradient pattern of the helicopter engine exhaust gas passing the BOS field of view. A classical BOS evaluation allows the visualization of density gradients such as vortices and the exhaust plume. The result is the BOS displacement field. Applying the two-dimensional divergence to this data results in a pattern that is constant in shape across multiple BOS images, but convects downstream with the outwash velocity of the helicopter. Using this data as input to a second, timeresolved evaluation, quantitative two-dimensional velocity fields are calculated. Choosing an appropriate strategy for preparing and evaluating the data is critical to reliable velocity estimation. Another important aspect is to distinguish between reliable velocity data and erroneous results in areas of reduced signal intensity due to a lack of thermal structures. The velocity data obtained are compared with an analytical outwash model and constant temperature anemometry data acquired simultaneously with the BOS images. The data show good quantitative agreement in areas of sufficient thermal structures within the field of view.
In the emerging market of Advanced Air Mobility (AAM), aerospace companies have been designing and prototyping electric and hybrid vehicles to revolutionize travel. These vehicles must have low noise and particulate emissions while also having enough propulsive efficiency to complete the mission. This paper presents the relationship between noise and propulsive efficiency as related to any aircraft equipped with an electric motor and a variable pitch rotor/propeller. The combination of the electric motor with the variable pitch propeller/rotor allows for a decoupled rotational speed and torque generation, meaning that the electric motor can generate the same amount of torque while operating at different rotational speeds. This feature allows the rotor/propeller to hold constant thrust at different combinations of rotational speeds and torque, by adjusting the collective pitch of the blades. Therefore, for a rotor at constant thrust, the minimum noise (from loading and thickness contributions) and minimum power operating points in terms of rotor RPM and collective blade pitch, are not the same thus leading to the fact that it takes increased energy to decrease noise. A MATLAB code is developed to investigate the power and noise relationship by employing several functions to integrate XFOIL and Blade Element Momentum Theory for the rotor performance calculations and WOPWOP for thickness and loading noise analysis.
This slash document collects general reference material related to gaseous oxygen system flow requirements and sizing calculations. This document will assist oxygen system equipment designers and operators to establish systems and equipment requirements. The document consists of charts, tables, system schematics, system requirements, and sample calculations for system sizing.
A novel aviation infrastructure system by a multilayer ecological & energized module (EEM) system is aiming to create a high safety & security, graceful and comfortable air travel environment, high-quality air, zero energy, zero-water-consumption, and zero-carbon with a 100% greening rate, etc. It contains a modular EEM optical runway, totally-enclosed EEM ecological modules, and EEM ecological modules with thin-film or silicon solar cells on the top layer, etc. With the light processed and enhancing and optimizing crushed shadows & blown highlights and high contrast color layout, the EEM optical runway has a powerful visual flight, runway visual range (RVR), and significant blown highlights in 3D position and posture in various complex weather and occasions for the instrument landing, manually land and taxiing, etc. It’s always clean and bright without lampblack and exhaust traces since it is easy to rinse and replace. The totally-enclosed EEM system is laid flat on the entire airfield, including the ceiling and flooring of aircraft as well. It will generate enough clean energy, provide enough high-quality air with plentiful oxygen, plant anions, floral, phytoncide, active constituents, and fragrant scents with low-concentration CO2 for passengers and staff, and completely isolate birds’ food chains and habitat, etc. With controllable photosynthetic acceleration, the EEM system is a powerful carbon capture system with significant positive spillover. With antiskid and rainwater steerable structures in the EEM, the planes have calculable security assurances in severe weather and catastrophic events. Hot, cold water and steam system without electromagnetic interference in EEM are used for hot waves and snow and ice.
A hydrogen economy is an increasingly popular solution to lower global carbon dioxide emissions. Previous research has been focused on the economic conditions necessary for hydrogen to be cost competitive, which tends to neglect the effectiveness of greenhouse gas mitigation for the very solutions proposed. The holistic carbon footprint assessment of hydrogen production, distribution, and utilization methods, otherwise known as “well-to-wheels” carbon intensity, is critical to ensure the new hydrogen strategies proposed are effective in reducing global carbon emissions. When looking at these total carbon intensities, however, there is no single clear consensus regarding the pathway forward. When comparing the two fundamental technologies of steam methane reforming and electrolysis, there are different scenarios where either technology has a “greener” outcome. Despite misconceptions, steam methane reforming produces fewer total carbon emissions than current on-grid electrolysis due to the carbon emissions released by power plants. Similarly, for storing and deploying hydrogen, the optimal solution set will depend upon use case and geographic location. For example, truck transportation of gaseous hydrogen becomes less carbon efficient than liquification for distances greater than 614 miles. This paper explores the nuances of the factors of production that affect the total carbon footprint of a given technology, and how other emerging complimentary technologies, such as carbon capture storage and utilization, may change this carbon footprint calculation. As new technologies are evaluated, there are technological, political, and economic factors that will shape the landscape of how and where, hydrogen is produced, and the global infrastructure by which it is distributed.
The global aviation industry adopted a set of targets to mitigate CO2 emissions resulting from air transportation in 2009. The engine fuel burn is the main driver of CO2 emission; hence it will be the focus of this study. Rotorcraft are designed for supporting different types of missions or operations that are different from fixed wing aircraft. For this reason, the rotorcraft strategy for addressing the carbon impact should mainly target the new emerging technologies that will assist in reducing the fuel consumption and the deployment of Sustainable Aviation Fuels (SAF). This paper presents a forecast of the contribution level that could be achieved by rotorcraft industry in CO2 emission reduction in the period up to 2050. A projection of growth in civil rotorcraft fleet worldwide is provided as the starting point. Several new emerging technologies for both rotorcraft and engine together with the implementation scheme and their projected positive net impact on CO2 emission level are considered. Further, the contribution from SAF deployment in rotorcraft operation is analyzed. It is generally recognized that as much as 80% reduction in overall CO2 life cycle emission can be achieved from SAF relative to the fossil-based fuels or Conventional Aviation Fuels (CAF). However, some critical parameters used in predicting the SAF benefits remain uncertain. These pertain to fuel resources, economy, investment and policies. Therefore, consistent with previous studies, several fuel substitution scenarios are considered ranging from the most conservative to an optimistic projection.
ABSTRACT Rotorcraft operations in arid environments can result in the ingestion of large quantities of dust particles into turboshaft engines, where they can melt and deposit on high pressure turbine nozzle guide vanes. This can result in reduced engine life-span and in worst case scenarios, in-flight engine failure. Predicting the extent and rate at which this damage occurs has proven difficult owing to the wide range of variables relating to the dust cloud, engine and most importantly, the properties of the particulate encountered. Whilst significant work has been carried out to model the particle deposition process for both volcanic ash and coal fly-ash, there is scarce similar work for the different types of mineral dusts rotorcraft encounter. In this contribution, we assess the suitability of two opposing numerical approaches for use in a generalised, reduced-order deposition model of individual mineral particles depositing on a vane. Both models are seen to be heavily reliant upon empirical inputs, be this the thermo-mechanical properties of the particles such as their yield strength, or currently unknown experimentally determined constants. An alternative approach is therefore proposed whereby the particle yield strength is correlated using existing relationships to the Vickers hardness of the grain, a property more amenable to empirical determination. The results obtained represent the current applicability limits of the two models based upon existing empirical data and thus highlight the need for further experimentation relating to both the thermo-mechanical properties and probabilities of adhesion for both individual mineral grains and mineral dust blends.
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