A Guide for Drone Manufactures: Selecting the Ideal Engine for UAV Propulsion

17 Nov 2023

Drones or unmanned aerial vehicles (UAVs) have revolutionized the way we see the world, from capturing aerial footage to delivering packages to our doorsteps. Behind the seamless flight of these unmanned aerial vehicles (UAVs) is a complex system of components, with the engine being one of the most critical as it provides the necessary power and propulsion to keep it in the air. 

As the demand for drones continues to rise, drone manufacturers are constantly searching for ways to enhance the performance and efficiency of their UAVs. 

With a plethora of engine options available in the market, selecting the ideal engine for UAV propulsion can be a daunting task for manufacturers. This article acts as a guide to help drone manufacturers to choose the most suitable engine for their specific drone applications. 

1. Piston Engines 

Piston-driven internal combustion engines, also known as reciprocating engines, are typically powered by fossil fuels such as gasoline or diesel. The engine’s mechanical components include a crankshaft, connecting rods, pistons, and cylinders. When fuel is burned within the cylinders, it causes the pistons to move, which in turn rotates the crankshaft and produces the engine’s power output. 

The size and weight of piston-driven engines make them well-suited for use in small to medium-sized drones. These engines are available in a variety of sizes, ranging from a few cubic centimeters to several hundred cubic centimeters, depending on the desired power output. 

Piston-driven internal combustion engines can generate substantial amounts of power, making them ideal for applications that require high speed and agility, such as racing drones. Moreover, the energy density of fossil fuels allows piston-driven engines to achieve longer flight times than batteries, making them a popular choice for commercial applications such as aerial photography and surveillance. 

However, piston engines also come with the following limitations: 

  • They require constant maintenance, as the internal components are subject to wear and tear over time. 
  • The combustion of fossil fuels also produces harmful emissions, such as carbon dioxide and nitrogen oxide, which can negatively impact the environment. 
  • These engines can be quite noisy, which can create problems in noise-sensitive environments. 

Some of the piston engine manufacturers include HFE international, Sky power International, RCV engines, and Danielson aircraft systems. 

2. Turbine Engines 

Turbine engines consist of three main types, turbojet engines, turboprop engines, and turboshaft engines. The mechanical components of a typical turbine engine include a compressor, a combustion chamber, a turbine, and an exhaust system. The turbine engines operate by compressing air and mixing it with fuel, which is then ignited to create a high-velocity gas stream that propels the aircraft forward.

A high power-to-weight ratio of the turbine engines can generate substantial amounts of power while remaining relatively lightweight, allowing UAVs to achieve high speeds, carry heavier payloads, and simultaneously eradicate vibration and noise.  

Turbine engines are fuel efficient and can run on a wider range of fuels, including kerosene, diesel, and even biofuels, which allows UAVs to operate in versatile environments. On the other hand, maintaining turbine engines can be expensive as their mechanical components occasionally wear out and need to be changed to maintain drone efficiency. 

Turbine engines are extensively utilized in both commercial and military sectors and can be effectively employed in medium-to-high altitude long endurance (MALE) and high-altitude long endurance (HALE) unmanned aerial vehicles (UAVs) due to their advanced digital designs, competitive operating costs, and maintenance expenses.  

Some of the key players in the market include PBS India, Rolls Royce, Pratt & Whitney, and UAV Turbines Inc. 

3. Electric Engines

Electric engines have emerged as a promising alternative to traditional combustion engines for unmanned aerial vehicles (UAVs). The mechanical components of electric engines include an electric motor, electronic speed controller, power sources, and an energy management system for efficient operation. 

Due to advancements in battery technology, such as efficient battery thermal management systems, electric engines are now able to power drones of various sizes and perform a range of tasks, such as surveillance, inspection, aerial photography, mapping, and delivery of small packages. 

Electric engines operate by converting electrical energy into mechanical energy through the use of electric motors that are powered by batteries. When these batteries discharge, they provide electrical energy to the motor, which drives the propellers to generate thrust and lift the aircraft off the ground. 

Electric engines produce less noise and vibration than traditional combustion engines, making them ideal for applications such as surveillance and inspection drones. Furthermore, electric engines are sustainable alternatives to traditional combustion engines as they do emit harmful pollutants, which helps in complying with zero emission policies. 

Traditional combustion engines waste a lot of energy through heat emission, while electric engines convert almost all of the electrical energy into mechanical energy, resulting in a much higher efficiency rate, which allows UAVs to fly for longer periods of time and to carry heavier payloads. 

Although electric engines are efficient in many ways, they do face some limitations owing to the energy storage capacity of the batteries because the energy provided by the batteries is still lower than that of fossil fuels. 

The development of UAV propulsion engines can be facilitated by technological advancements, such as the integration of hybrid propulsion, an effective combination of electric and internal combustion (IC) engines that can help to improve fuel economy and reduce reliance on non-renewable fuels. 

According to BIS Research, the global UAV propulsion system market is estimated to reach $10.76 billion in 2033 from $8.36 billion in 2022, at a CAGR of 2.33% during the forecast period 2023–2033. 

4. Wankel Engines 

 Wankel engines, also known as rotary engines, are a type of internal combustion engine that uses a rotary design to convert fuel into mechanical energy. The Wankel engine has a rotor with three sides that rotates inside a housing. Each side of the rotor acts as a piston and goes through a four-stroke cycle (intake, compression, ignition, and exhaust) as it rotates around the housing. 

 Wankel engines have a high power-to-weight ratio than piston engines of equivalent power output due to their compact size and rotary design. Moreover, Wankel engines are cost-effective as they have fewer moving parts, resulting in lower maintenance requirements and higher reliability, and are best suited for fixed-wing UAVs with high electrical loads and VTOLs. 

Wankel engines are limited by the following factors: 

  • Wankel engines have relatively low thermal efficiency. 
  • The higher surface area-to-volume ratio due to the design of Wankel engines causes higher heat losses and lower thermal efficiency compared to piston engines. 
  • Wankel engines can have higher fuel consumption compared to piston engines. 
  • Wankel engines can have higher emissions due to their unique combustion process. 

There are several manufacturers of Wankel engines, such as BRP-Rotax Gmbh, UAV Engines Ltd., Advanced Innovative Engineering (UK) Ltd, as well as HFE International. 

5. Solar-Powered Engines

Solar-powered engines, or solar engines, use solar panels to convert solar energy into electrical energy, which is then used to power the motor that drives the propeller, which lifts the UAV forward. Solar-powered engines are environment-friendly and have no fuel costs, which makes them an economical choice for UAV operators that want to reduce their operating costs. 

Solar-powered engines can increase the UAV’s flight time, allowing for more extended data collection, surveillance, and monitoring missions as they do not require refueling and can remain airborne for a more extended period. 

There are two main types of solar-powered engines used in UAVs: 

  • Solar-electric engines, which use photovoltaic cells to convert the energy from the sun into electrical energy, are highly efficient, produce minimal noise, and are suitable for stealth applications such as military operations and surveillance missions. 
  • Solar-thermal engines generate thermal energy using concentrated solar power to power the engine and are highly efficient, capable of generating high levels of thrust, and suitable for high-power output applications such as cargo transport and delivery. 

With the advancements in solar technology, these engines are becoming more efficient and cost-effective, which makes them an attractive option for UAV operators. 

For instance, the U.S. Army is currently testing Zephyr, a solar-powered drone built by Airbus that delivers the benefits of Intelligence, surveillance and reconnaissance (ISR) satellites and traditional drones without many of their limitations. 

The Bottom Line

Selecting the ideal engine for UAV propulsion is a critical decision for drone manufacturers, as it directly impacts the performance, reliability, and sustainability of their products. A manufacturer must carefully evaluate the pros and cons of each engine available in the market in order to determine which engine best suits their drone’s specific needs. 

With advancements in propulsion technology, such as solar-powered engines and hybrid propulsion systems, drone manufacturers must continue to innovate and invest in cleaner solutions that meet the growing demands of the market and contribute to a more sustainable future. 

Interested to know more about the advancing technologies in your industry vertical? Get the latest market studies and insights from BIS Research. Connect with us at [email protected] to learn and understand more.