Wave disk engine
Pistonless internal-combustion engine
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A wave disk engine or wave disk generator is a type of pistonless rotary engine being developed at Michigan State University and Warsaw Institute of Technology. The engine has a spinning disk with curved blades. Once fuel and air enter the engine, the rotation of the disk creates shockwaves that compress the mixture. When ignited, the burning mixture expands, pushing against the blades, causing them to spin. The spinning of the disk itself opens and closes intake and exhaust ports.[1] The proposed concept was called a radial internal combustion wave rotor.
Background
Wave rotors utilize shock waves to transfer energy between a high-energy fluid to a low-energy fluid, thereby increasing both temperature and pressure of the low-energy fluid (also called pressure wave machines or pressure exchangers).
Operational principles
As with all heat engines, the efficiency of a wave disk engine is governed by the temperature difference between the hot and cold sides (see Carnot's theorem). Compared to a conventional piston engine (reciprocating engine), a wave disk engine works at higher peak temperature, which theoretically makes it more efficient. The design also works without a cooling system, saving weight. Compared to turbine based systems, the rotational speed and the rotor-blade temperature of the wave disk engine is lower, which creates lower stress on materials, and consequently less demanding requirements for materials, leading to cheaper manufacturing and maintenance costs.[2]
Earlier wave rotor implementations were mainly axial flow, where the scavenging process of returning hot compressed air back into the turbine is complex. The wave-disc engine uses a radial and circumferential flow, using centrifugal forces for scavenging. Curved channels provide greater length for the same disc diameter compared to straight channels, allowing the travel times of the waves to be tuned properly.
Current status
The wave-disk engine has the potential for better energy efficiency compared to conventional internal combustion engine designs and can potentially save weight. Possible applications include charging batteries in hybrid vehicles, which could reduce weight by about 1,000 pounds (450 kg).[3][1][citation needed] It promises to be up to 60% more efficient, 30% lighter, and 30% cheaper to manufacture than an equivalent conventional piston engine, and to reduce emissions by 90%.[4]
Researchers from Michigan State University and the Warsaw Institute of Technology developed a prototype wave-disk engine and electricity generator, proposed as a potential replacement for conventional backup generators in plug-in hybrid electric vehicles. The project, led by Associate Professor Norbert Müller, received $2.5 million in funding from the U.S. Department of Energy’s ARPA-E program and initially aimed to produce a 25 kW (33 hp) vehicle-scale system by 2011. By 2013, efforts had shifted toward commercialization, and subsequent research continued in academic settings through at least 2017.
Since then, development has progressed modestly, including patented designs granted in 2018, but as of 2025 the technology has not reached commercial deployment and remains largely in the experimental and research stage, with no confirmed large-scale applications.