Hybrid engine for unmanned aerial vehicles
Lowenthal Hybrid executives Doron Friedman (left) and Itai Lowenthal (right) demonstrate the LH-01 propulsion-powered UAV prototype.
Israeli companies Elbit Systems Ltd. and Lowental Hybrid Ltd. have signed a long-term cooperation agreement. Under this agreement, they will jointly develop unmanned aerial vehicles (UAVs) over the coming years. aviationThis collaboration is aimed at improving propulsion systems and enhancing the key flight characteristics of unmanned aircraft. This primarily involves the implementation of hybrid systems from the Native Parallel Hybrid family.
Long-term cooperation
Elbit Systems is a key player in Israel's defense industry. It develops and manufactures a wide range of products across various classes and applications, including a number of UAVs. Lowenthal Hybrid, meanwhile, was founded in 2018 and focuses exclusively on the development of propulsion systems for small aircraft. It offers customers several hybrid systems under the umbrella name Native Parallel Hybrid (NPH).
Overall, the two companies were interested in collaborating. Lowental Hybrid could gain a major customer willing to purchase significant quantities of its products. For Elbit Systems, such a partnership meant access to advanced technologies and propulsion systems.
Recently, the companies held the necessary negotiations and defined the terms of cooperation. This resulted in the agreement signed a few days ago.
Product LH-01 with propeller
According to this document, the two companies will collaborate over the next 10 years on the development of unmanned aircraft. Elbit intends to leverage its existing experience and develop new aerial platforms. Lowenthal will manufacture and supply engines for these platforms.
It is noted that NPH hybrid engines will significantly improve the fuel efficiency of UAVs. This will dramatically enhance their key performance characteristics, namely, range and flight endurance. Such engines can be used to upgrade existing ones. drones, as well as in the development of completely new ones.
For obvious reasons, the two companies are not yet disclosing all the details of their future collaboration. They haven't specified which engines Lowenthal Hybrid will supply, which UAVs Elbit Systems plans to equip with them, and so on. It's also unclear whether the companies will limit themselves to existing NPH products or develop new ones to suit future UAVs.
However, the lack of public information doesn't mean there are no real plans. The two companies are likely already prepared to implement them. Consequently, the first UAVs with hybrid engines could begin testing in the very near future. Given the specific nature of such projects and the expected benefits, it's expected that Elbit and Lowental will not delay the launch of their advertising campaign.
Installation of LH-02
Parallel hybrids
Lowental Hybrid currently offers four systems in its Native Parallel Hybrid product catalog. They are built on the same design and operate on similar principles, but differ in size, power, and other parameters. Furthermore, the systems are designed for aircraft of varying weight categories, each with their own power requirements.
All NPH units are built on a spatial frame made of metal sections. This unit is attached to the airframe of the carrier drone. The smaller LH-01 and LH-02 units have rectangular frames with some of the units housed internally. Units numbered "03" and "04" feature an L-shaped frame with a slightly different layout.
The internal combustion engine is housed within the frame. The NPH family uses two-stroke, single- and twin-cylinder engines of varying power outputs. The muffler, located outside the frame, is mounted directly to the cylinder. The engine shaft extends beyond the front of the frame, and a belt drive pulley is mounted on it.
Above the engine shaft on the frame (outside) is the driven transmission pulley, a uniquely designed gearbox, and a coaxial electric motor, which also functions as a generator. As with gasoline engines, different engine configurations use different motors with the required performance levels. The gearbox/electric motor shaft is used to mount the propeller.
Product LH-03
The hybrid system includes batteries of the required capacity. They are optimally positioned inside the aircraft. It also includes converters and control systems.
The most compact and low-power unit in the family, the LH-01, weighs just 2,5 kg (excluding tanks and batteries). It has a 1,9 hp internal combustion engine and a 3,69 hp electric motor. The larger LH-02 system weighs 3,3 kg and uses a 3,2 hp gasoline engine and a 4,82 hp electric motor.
The LH-03 has a different layout and weighs 4,65 kg. It uses a 4,55 hp internal combustion engine and a 9,86 hp electric motor. The most powerful unit in the family is the LH-04. Its gasoline engine produces 8 hp, and its electric motor produces 12,25 hp. The weight, however, is 6,1 kg.
Work principles
The operating principle of the Native Parallel Hybrid system is quite simple. Depending on the flight mode and current requirements, the internal combustion engine and electric motor operate either together or alternately. Each mode has its own characteristics, but together they improve the UAV's key performance characteristics.
Thus, the gasoline engine generates thrust during operation and, together with the electric motor, charges the battery in generator mode. If increased power is needed, the two engines operate together, and their power is transmitted to the propeller through a gearbox. The electric motor receives power from the battery. It is also possible to switch off the internal combustion engine and switch completely to electric propulsion using the battery's charge.
LH-04 is the most powerful member of the family
It is assumed that such a propulsion system will alternate between different modes during flight. The transition between them depends on the flight plan, energy consumption, and other factors. Optimal use of these modes reduces fuel consumption and improves energy efficiency.
With advantages and disadvantages
Lowenthal Hybrid claims that the NPH system provides the carrier drone with unique capabilities. Compared to a fully electric system, it increases flight endurance by five times. Unlike an internal combustion engine, the hybrid system can operate virtually silently. It also combines other advantages of gasoline and electric engines.
At the same time, NPH products are not without their drawbacks. First and foremost, like any other hybrid system, they are more complex than a simple internal combustion engine or electric system. Furthermore, the presence of two engines and auxiliary equipment increases the size and weight. This places additional demands on compatible aerial platforms.
Lowenthal Hybrid offers several NPH engine options, but all of them have a power output of no more than 10-12 hp. This significantly limits the range of UAVs that can be equipped with such systems. Engines of this family are only suitable for use on drones weighing tens of kilograms.
The Elbit Hermes 900 heavy reconnaissance UAV. This class of equipment would benefit from NPH installations.
The developer may be planning to scale up existing technologies and create new propulsion systems in the future. Whether it will be able to reach a power level of tens of horsepower remains unclear. Further power increases are also uncertain.
Clearly, Lowenthal's hybrid systems aren't a universal solution for all UAVs. They should only be installed on those UAVs that can utilize all the inherent advantages of NPH and mitigate their shortcomings. These should be medium-sized UAVs for reconnaissance or reconnaissance-and-strike missions, designed for long-range flights. The use of NPH systems in other categories of UAVs is impractical, although the possibility of their adaptation cannot be ruled out.
In the early stages
Apparently, Elbit Systems and Lowental Hybrid are currently working together to find suitable aerial platforms or formulate requirements for new types of such equipment. New projects will then emerge, and in the foreseeable future, promising UAVs will begin testing.
Two Israeli companies plan to leverage new technologies and developments to secure lucrative contracts. This means they won't delay the development of promising projects and will begin a promotional campaign as soon as possible. The first results of their collaboration may be presented at an upcoming international exhibition.
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