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The Dada engine is a dual-mode operation heat engine which moves a working gas in a closed circuit between two cylinders of different volumes, via two heat exchangers selected by passive valves, so as to approach a Brayton/Joule cycle. It can function either as an external heat engine or as a heat pump, refrigerator. The working gas may be inert: helium, nitrogen or air.

On a similar principle, the Stirling engine, which has been in existence for two centuries, carries out heat transfer within the cylinders; the idea here is to transfer heat as the gas passes from one cylinder to another. During its cycle, the engine undergoes a compression and an expansion, interspersed with phases of heat exchange that are ideally isobaric. The valves determine the direction of flow through the heat exchangers. Between the end of compression and the start of expansion, all of the gas passes through the hot heat exchanger. During expansion and until the start of compression, all of the gas passes through the cold heat exchanger.

Heat exchangers are a key component of this machine, they must provide maximum heat transfer surface area relative to internal volume, while minimising pressure drops. So far, only microtube heat exchangers have been considered. The cylinders and pistons are made from a material with low thermal conductivity. The piston kinematics can be achieved using various methods, achieving maximum efficiency requires a complex motion which can be accurately approximated using a 6-bar linkage, while a simple crank-connecting rod system will allow operation at reduced efficiency. For refrigeration applications, numerous mechanisms are possible, such as cams, actuators, solenoids, etc.

There still exist no prototype of the Dada engine. A comprehensive thermodynamic and mechanical study has been carried out, which served as the basis for the design of a 0D simulator. This is an open-source project, any help is welcome.

Motor cycle

Phase I — low-pressure heat exchange, ideally isobaric

Almost all of the gas is transferred from the large cylinder to the small cylinder via the cold heat exchanger, heat is extracted from gas, causing its volume and temperature to decrease.

Phase II — Compression, ideally adiabatic

The large cylinder closes completely, the small cylinder compresses the gas, causing its volume to decrease while its pressure and temperature increase.

Phase III — High-pressure heat exchange, ideally isobaric

All of the gas is transferred from the small cylinder to the large cylinder via the hot heat exchanger, it absorbs heat, causing its volume and temperature to increase.

Phase IV — Expansion, ideally adiabatic

The large cylinder opens fully, the small cylinder participates in the expansion and opens slightly, the volume of the gas increases, while the pressure and temperature decrease.

Receiver cycle (heat pump, refrigerator)

Phase I — Compression, ideally adiabatic

The small cylinder closes completely, the large cylinder closes partially, the volume decreases, while the pressure and temperature increase.

Phase II — High-pressure heat exchange, ideally isobaric

All the gas is transferred from the large cylinder to the small cylinder via the hot heat exchanger, the gas releases heat there, its volume and temperature decrease.

Phase III — Expansion, ideally adiabatic

The small cylinder opens fully, the large cylinder participates in the expansion and opens slightly, the volume of the gas increases, while pressure and temperature decrease.

Phase IV — low-pressure heat exchange, ideally isobaric

Almost all of the gas is transferred from the small cylinder to the large cylinder via the cold heat exchanger, the gas absorbs heat there, and its volume and temperature increase.

Way to a real machine

In Dada engine, the heat exchangers remain active throughout the cycle, compression and expansion cannot be perfectly adiabatic. In order to minimise irreversibilities, these phases must be brief in relation to the thermal time constants, dead volumes and internal volumes of the heat exchangers will be kept to a minimum.

Heat transfer through the heat exchangers results in pressure drops, a perfect isobaric process is unachievable. To minimise these losses, the duration of the heat transfer is extended to limit the flow rate, and the heat exchangers must offer as little resistance as possible to the passage of the gas.

A comprehensive thermodynamic analysis of the cycle was carried out using extensive AI. I learnt a great deal while writing this, and although I believe this work to be rigorous, it requires an expert review: Thermodynamic_and_Mechanical_Study.

Based on the equations established in this study, a 0D simulator was developed in Python (entirely by AI, including documentation) in order to determine the optimal dimensions and parameters of this machine in various configurations: Dada_Engine_Solver. I used it to size a cooling cell using air as working gas, powered by a pedal mechanism. I hope to size an air small demonstrator engine in the coming weeks, followed by a heat pump and a motor using helium as working gas.

Is it free?

Totally! The description of this invention is published here under Creative Commons Zero license, however I cannot guarantee that all or part of this machine is not currently protected by a patent.

I sincerely hope that this idea will help reduce greenhouse gases emissions, and I'm convinced that making it free is the best thing I can do to facilitate its development and rapid spread.

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