eSTOL aircraft and eVTOL aircraft are being developed for taking off and landing on limited runways. eSTOL aircraft utilize the slipstream generated by distributed propellers to significantly increase the effective lift coefficient and reduce the takeoff and landing distances. The wings of eSTOL aircraft can generate lift at all stages of flight. eSTOL aircraft can achieve smaller thrust requirements and lighter propulsion system weights compared to eVTOL aircraft. It can increase the payload and range or reduce the aircraft weight of a given task [ 1 ]. Christopher Courtin compares the performance differences between eSTOL and eVTOL aircraft. For aircraft with an equivalent takeoff weight and wingspan to proposed eVTOL aircraft, eSTOL aircraft are able to carry 1.8&#;2.6 times the payload at the same speed and range [ 1 ]. A series of flight tests demonstrated the enhancement of aircraft performance through DEP technology. The flight testing of a 30% subscale demonstrator of a blown-wing Super-STOL aircraft [ 2 ] has shown that blown lift vehicles can generate lift coefficients greater than 10, which may enable GA-sized aircraft to have takeoff and landing ground rolls under 100 ft [ 3 ]. Yiyuan Ma [ 4 6 ] and Xingyu Zhang [ 7 8 ] conducted studies on the overall design and aerodynamic characteristics of DEP UAVs. A 21% subscale model of a Cirrus SR22T is developed for testing a dynamically-scaled, distributed electric ducted fan [ 9 ]. The Electra [ 10 ] eSTOL aircraft uses the interaction between distributed propellers and wing/flaps to generate blown lift. Its first short takeoff experiment took off at 8 s, with a takeoff distance of 30 m. A Distributed Electric Propulsion version of the D03 Scaled Flight Demonstrator has been designed, manufactured, and ground tested from to [ 11 ].
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Specially designed eSTOL UAV with a DEP system can achieve takeoff and landing distances comparable with the ground footprint proposed for eVTOL UAV facilities. TUDelft Micro Air Vehicle Lab has developed the NederDrone [ 12 ], a tandem-wing layout, hybrid energy hydrogen-powered UAV with 12 propellers. It has vertical takeoff and landing capability and can efficiently fly forward in cruise. C. De Wagter analyzed the selection of the UAV concept, the electronics, and the flight control system and showed a 3 h 38 min flight data at sea while taking off and landing from a moving ship [ 13 ].
In the study of propulsion systems for DEP aircraft, Guillem Moreno Bravo [ 14 ] conducted relevant research on generators, batteries, wires, motors, and other components, and concluded that a purely electric concept was not feasible for an airplane such as DA42. Majid T. Fard [ 15 ] presents a comprehensive review of the emerging DEP technologies for three various propulsion architectures: turboelectric, hybrid electric, and all-electric propulsion systems, summarizes the performance advantages of the DEP systems, and compares examples of existing DEP designs.
In the study of propulsion systems for lightweight UAVs, Dongjie Shi [ 16 ] and Hang Zhang [ 17 ] carried out a modeling study of the electric propulsion system, constructed models of propellers, motors, ESCs, and batteries, and constructed a simulation flow of the propulsion system with propeller speed and torque as inputs. Aiming at the power requirements of distributed propulsion tilt-wing UAVs, Cheng He [ 18 ] presented an optimization design method for series hybrid electric propulsion systems suitable for this type of aircraft. The current studies do not consider the motor temperature factor, and the model prediction error increases when the motor is in a high-power and high-temperature state.
eSTOL UAVs use the maximum power during the takeoff phase. The takeoff time of eSTOL UAVs is generally less than 5 s. The primary challenge of the propulsion system is how to increase the peak power without adding propulsion system weight. Based on the characteristics of short time and high-peak-power during the eSTOL UAV takeoff phase, designing a high-peak-power DEP system can effectively improve power density or reduce the weight of the propulsion system. There is a lack of research on the design of high-peak-power propulsion system for eSTOL UAVs. The main limiting factor for the peak power of the propulsion system is the temperature limit of the motor. Existing models have not considered the effect of motor temperature. Finally, the design of the DEP system faces the problem that after multiple propulsion units are installed, the power and thrust decrease due to wire losses.
This research is based on the requirement of a DEP Super-STOL UAV propulsion system and establishes a propulsion system model considering motor temperature and throttle input. By using overload design strategy, the peak power of the propulsion system is increased, enabling the UAV to achieve takeoff in a short distance. The second part specifies the propulsion system requirements and preliminary selection of the propulsion unit. The third part constructs a DEP system model considering temperature with throttle input. The fourth part includes the design of high-peak-power propulsion unit, ground bench experiments, and Super-STOL UAV flight experiments.
Internal plastic mechanical parts can be defined as any component that is incorporated into a mechanical mechanism within a product in order for it to operate or function as outlined in the product specification. This can include gears, bearings, shafts, structural elements, and hinges.
Each mechanical part will require specific properties in order to meet its design criteria, which could be high wear resistance, high sliding characteristics, flexibility with repeatable bending over its lifespan or other very specific attributes.
In general, internal plastic mechanical parts will be produced from one of the engineering plastics. Engineering plastics can be classified as plastics that have better mechanical and/or thermal properties than the more commonly used plastics. These engineering plastics each offer a unique property that will be best suited for specific applications.
In this series of articles, we will examine some popular internal plastic mechanical parts and some appropriate engineering plastics that would be suitable for each component type to help you get started with sourcing them.
With the engineering plastics available today, plastic gears are becoming ever more popular and the advantages of replacing metal gears with them are increasing.
Some industries are now able to use plastic gears and benefit from maintenance-free operations even in corrosive environments and harsh conditions that would simply not have been possible with metal gears.
Some of the obvious advantages of using plastic gears are weight savings, reduced cost, and better performance.
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In this article, we look at which plastic is ideal for machined gears and which is best for injection molded gears.
Plastic bearings are being used in more applications as the number of specific engineering polymers increases.
Plastic bearings have many advantages over conventional metal bearings such as their resistance to corrosive environments where metal bearings cannot be used. The fact that most of these plastics are self-lubricating eliminates the need for oils and other lubricants. There are even more benefits to be enjoyed over metal bearings, too, which we&#;ll get into.
Multiple plastics have the characteristics that make them candidates for use in bearings, however, in reality, only a few types are predominantly used, and we&#;ll take a look at them in this guide to plastic bearings.
There are multiple reasons why you would look for an alternative shaft material over steel or any other metal for that fact, cost reduction, weight reduction, corrosive environment, and in some cases the design of integrated features that could be achieved with a metal shaft design.
Because of the torsional and flexural requirements a shaft has to withstand, the plastics generally used are reinforced and what is classed as composites. So let&#;s examine plastic composites as suitable plastics for shaft production in this guide.
Hinges that are made from plastic are also known as living hinges and differ from the conventional three-part metal hinge in that the hinge is created within the plastic component as a single part.
You will see these types of hinges in everyday items such as shampoo lids, squeezy sauce bottles, pill boxes, or the lids of toothpaste tubes, for example.
There is one predominant plastic used for living hinges and we discuss its properties in this article.
You can learn more about plastics by reading and watching this content:
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