Essay Example on Sustainable Aviation: Moving Away from Gas-Fed Piston Engines

Introduction

While manned aircraft has limited command-and-control policy restrictions and require autonomy, the unmanned aircraft is not limited since it has no crew and hence has no risk of life loss. From the earliest stages, aviation has relied on gas-fed piston engines and turbines that have propelled military might, goods, and people around the globe. These gas-fed jet engines are unsustainable due to their substantial use of fossil fuel and claimed adverse effects upon the environment. Their reliability is questionable as they rely on non-renewable fossil fuel. Non-renewable resources are prone to becoming extinct, and this could create a crisis if new technologies are not developed. Fossil fuels also release carbon dioxide, which is a greenhouse gas that highly pollutes the environment and causes climatic change. Due to their overwhelming effects, the world is seeking to curb the use of fossil fuels and adopt sustainable greener methods of powering the engine. In this regard, the technology aims to replace the gas-fed engines in manned and uncrewed aircraft with more advanced techniques. Technology is rapidly changing, and so is the propulsions system of the plane. The need for more energy-efficient and environmentally friendly systems are warranted. There is a need for the development of faster, more reliable, lighter, and more efficient propulsion systems such as hybrid and fully electric propulsion systems for years for manned and uncrewed aircraft. Hence, in the future, the aircraft engines will depend on electric and hybrid types of engine systems. The conventional propulsion systems are obsolete, unsustainable, and environmentally unfriendly; the future targets their replacement with more efficient, environmentally friendly, faster, more reliable, and lighter propulsion systems.

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Traditional Propulsion systems

Gas Fed Engines Propulsion Systems

The aircraft propulsion system consists of a propeller engine, which converts action in an engine and generates driving force, and this is what keeps the aircraft in motion (Chen et al., 2019). Technology has, for many years, being perceived to be the best and is hence the dominant technological system. Much technological inventions and advancement have been achieved in the aviation industry. Massive innovations in the gas-fed engines propulsion systems and the battery-powered aircraft have been met. Aeronautical engineers have been working tirelessly to come up with such kind of inventions. All these innovations and creativity have been directed to making the aviation industry safe, effective, and convenient due to the current trends in the field of aviation. Such changes have played a significant role in maintaining some countries in the highly competitive market in the aviation industry. The aircraft propulsion system consists of a propeller engine, which converts action in an engine and generates driving force, and this is what keeps the aircraft in motion. The machine, which produces the driving force that pushes an object ahead.

The gas turbine is an internal incineration engine that uses air as the working fluid. The engine extracts chemical energy from fossil fuels. It converts it to mechanical energy using the gaseous exchange of air, which in turn moves the engine propeller and keeps the aircraft running or in thrust. A vast mass of air has to be supplied to the gas engine to generate the expected power. Additionally, the air has to be provided to the compressor, which pushes air into the engine and squeezes it offers high pressure to the turbine. The compressor lastly converts the mechanical energy from the turbine to gaseous energy in the form of pressure and temperature, which keeps the aircraft in motion and running. The gas-feed/aircraft engine is not environmentally friendly as compared to other renewable resources that are non-hazardous to the environment. Much of the gas fed aircraft engines can be managed as they are not as complicated as other the hybrid engines, which requires specialized and skilled training in the field of aviation. To support this, the gas-fed drivers were the pioneer engines in the field of aviation, and the aircraft industry and many inventions and innovations have incorporated to come up with the most effective, safe, and less costly aircraft engine.

Challenges of Gas Fed Engines Propulsion Systems

Gas-fed engines are not sustainable because the fossil gases are non-renewable. Besides, fossil fuels release greenhouse gases that cause pollution to the environment. There other challenge of the conventional gas fed- engine is low efficiency. The low efficiency could at times be attributed to low quality fuels that contain impurities such as vanadium, sulfur or sodium which lowers the efficiency. Such impurities can as well lead to corrosion of the aircraft components when they mix to form molten salts of V2O5 and Na2SO4 at high temperatures (Chen et al., 2019).

Clean Sky and Clean Air Act, Regulations and Legislations

The major challenge of the fossil-fuel-powered engines is the greenhouse gases that not only pollute the environment but also cause climate change. In the 21st century, climate change has become a hot debate on how to reduce the use of fossil fuels that release vast amounts of carbon dioxide to the environment. The need for greener technologies arose, and this led to the enactment t of legislation and regulation to curb the release. In addition to the rules, the Clean Sky Joint Undertaking set up two large scale research and innovation programmers under the Horizon 2020 and FP7 to develop more competitive technologies (Brouckaert et al., 2018). The joint undertaking has since then worked in phases where phase one runs from 2008 to 2017, and step 2 duped Clean Sky 2 runs from 2014 to 2024 to develop the next generation of propulsion technologies in aircraft. Clean Sky 1 came up with the Sustainable And Green Engines (SAGE) programme while Clean Sky 2 came up with the ENGINES programme (Brouckaert et al., 2018).

Clean Sky has made several developments and various engine architectures proposed and tested. For sustainable aviation, Clean Aky targets the creation of sustainable and Green Engines" (SAGE) under the "ENGINES" programme to produce engines such as turboshaft engines, geared turbofans, UHBR turbofans and Safran aircraft engines for the future (Brouckaert, 2018).

For instance, the ultra-high propulsive efficiency (UHPE) technology for the Safran Aircraft Engines has been designed for short/medium-range applications. Such open rotor architectures use the principle of High, Ultrahigh Bypass Ratio, or the Geared turbofans. These types of engine became the most advanced and the most fuel-efficient state of the art technologies for the future generation of aircraft engine propulsion systems. The architecture has high potential with the capacity to reduce fuel burn by 15% compared to the CFM56 (Brouckaert et al., 2018). To harness this potential, Clean Sky 2 is working to produce the Contra -Rotating Open Rotor (CROR) engine for the maximum capacity.

The UHBR engines aim to create technologies with advanced low-pressure-ratio fan/short inlet and with low weight. Other features include the structures with small noise ducts and low drag and improved technology capabilities like a low-pressure turbine, power gearbox, high-speed compressor booster, and innovative engine/airframe integration. The engine structure is expected to reduce carbon emissions by 23% compared to the 2000 aircraft (Brouckaert et al., 2018). Figure 1 shows the UHBR engine architecture for future propulsions:

The second engine structure is the large Very High Bypass Ratio (VHBR) turbofan engine architectures which possess Advanced Low-Pressure System, lightweight, and compressor structures technologies. The technology is being developed with the input of the Rolls-Royce, which seeks to develop technologies with higher efficiency and low-pressure turbines. The architecture was successfully tested in 2014 and demonstrated a composite fan blade in-flight operability and a reduction of carbon emissions by 3% to 5% (Brouckaert et al., 2018). Figure 2 below shows the engine architecture developed by Rolls-Royce.

Additional improvements in the engine structure are the introduction of the geared transmission between the LP turbine and the fan expected to attain a higher by pass-ratio. Noise is a significant factor in the development of engines, and the architecture is expected to cause a reduction of noise levels by a higher percentage. The geared turbofans have been developed and implemented successfully to power the Regional Jets such as the Bombardier C-Series and small engines such as the A320 Aircraft. Such engine systems have proved to possess superior low-noise characteristics and double efficiency in fuel consumption. Currently, Clean Sky 2 is keen to develop eco-engine designs for sustainable aviation that meets Europe's Flightpath 2050. Such engines are useful in fuel consumption economy and noise reduction.

The clean Air Act regulates the emission of greenhouse gases, and this covers the airline's emissions. Aircraft use kerosene, which is a petroleum product with several carbon atoms. The combustion of petroleum products releases carbon dioxide, which is an air pollutant and a greenhouse gas. According to Richardson (2012), aircraft emit about 2% to 3% annually of the total world greenhouse gases. Rather than decreasing, the percentage of continuously increasing, and it is projected that by 2050, it will range from 290% to 667%. Such emissions carefully compare to the vast amounts released in ground transportation and electric power. For a greener environment, and to avoid adverse effects of climate change caused by carbon dioxide and other greenhouse gases, regulation is highly required.

The provisions of the Clean Air Act are regulated by agencies such as the U.S. Environmental Protection Agency. Before CAA was enacted, problems on who should regulate aviation emissions were a significant problem. The agency regulates the emissions of the greenhouse gases from various sources, among them the aviation and industrial facilities. However, there has been a reluctance to control the emission of greenhouse gases from aircraft. The challenge is that the International Civil Aviation Organization (ICAO) has failed to issue regulations and guidelines on the emissions of greenhouse gases. In contrast, EPA has reluctantly was unable to overtake the authority of ICAO.

The enactment of the CAA necessitated proper regulation since the act gave EPA the mandate to regulate aviation emissions. EPA achieves its role through collaborations with Federal Aviation Administration (FAA). The call to regulate aviation emissions touches on the architecture of the aircraft engine. Hence, regulations require that the aviation industry develop new technologies that do not emit carbon. However, the change in engine architecture has to affect the design of the aircraft to some extent. But to be considered, the EPA regulations required the evolution of the engine alone unless there is a need to change the entire design of the aircraft. The law has, therefore, provoked the thoughts of designing better sustainable and environmentally friendly aircraft engines that can reduce greenhouse gas emissions. Future engine architectures are expected to produce low emissions or none for a greener world and economy.

Recent Developments For Future Propulsions

The need for the development of engines with greater efficiency has led to significant improvement of the gas...