Galin engine is an internal combustion engine converting the heat energy of combustion into mechanical shaft power and/or directly into electrical energy.

Galin engine is based on the rotary vane (scissor action, cat-and-mouse) operating principle. What is a rotary vane engine? For some historical examples of such engine designs see here. Figures 1 and 2 compare the combustion chambers of existing reciprocating piston engines with that of the rotary vane engines. Notable differences between the two are:

• no slider-crank mechanism,

• no valves,

• no camshaft,

• no reciprocating motion, rotational motion is produced directly

  at the output shaft,

• 4 combustion strokes per shaft revolution

Unlike in the reciprocating piston engine which has one combustion stroke per shaft revolution (for a single cylinder) the rotary vane engine has four strokes per shaft revolution. In the rotary vane engine all four strokes are simultaneously performed inside the combustion chamber. Figures 3 and 4 compare the combustion process of the reciprocating piston cylinder with the rotary vane cylinder. Figure 3 shows us that in the reciprocating piston we have one combustion stroke for every 2 revolutions of the crankshaft, whereas in the rotary vane engine, figure 4, we have two combustion strokes for every shaft revolution.

There is no strong reason to suppose that the combustion process itself will be particularly more efficient (although, we can lean on Le Chatelier-Braun principle to argue that the conditions for complete combustion of fuel are better observed inside the rotary vane chamber) however, one can definitely see that the power to weight ratio of the rotary vane engine is superior to the reciprocating piston type.

Additionally, torque output from the rotary vane design is significantly greater as there is no slider-crank lever mechanism to mediate the generated torque. The problem with the slider-crank mechanism is that at the moment of highest torque (moment of combustion) the lever arm is zero, consequently output power is zero. In contrast, the rotary vane engine has a constant lever arm that does not change as a function of shaft rotation. To emphasise the point further, let us look at how much the slider-crank mechanism affects the torque output of the piston engine versus the constant lever arm of the rotary vane engine. Our GitHub repo contains some MATLAB simulation code of just the combustion process of the piston and rotary vane engines. Figure 5 plots the pressure inside a cylinder volume after combustion as a function of cylinder volume, figure 6 plots the lever arm of the piston (red) and rotary vane (blue) as a function of cylinder volume.

Many attempts to make the rotary vane engine work have been made. In fact back in 2010 an attempt was made to restart the Russian automotive industry with the introduction of the “ё-мобиль“ (Yo-mobile) whose prime mover was going to be none other than a rotary vane engine. Unfortunately, nothing came of it: “On 7 April 2014 it was announced that the project was sold to the Russian government for €1.[5] As of 2017, no production vehicles were ever produced.” It was not due to engine problems.

To date, aside from Andrew Dec’s demonstration prototype of the rotary vane engine, no engines based on the rotary vane mechanism have been developed let alone made it to market. Why?

The main cause of failure in all known constructions of the rotary vane engine is the use of mechanical linkages to coordinate shaft rotation. The patent literature is replete with variations of these (e.g. here and here). The reason that we have seen historical practical failure of these engines to date is that components in these linkages experience alternating shock loadings, which quickly lead to their destruction.

Now, we are ready to explain what is Galin engine? What differentiates it from the standard rotary vane engine described above, and what makes it a viable rotary vane engine?

The key inventive step in Galin engine is replacing the mechanical linkages with electrical machines to regulate the motion of the shafts and make sure that the vanes are at the required place at the required time to go through the four stages of the combustion cycle. See figure 8 for the block diagram of Galin engine with the key components.

Equipping the engine with electrical machines opens up a world of possibilities. We have all the benefits already listed that are present in the rotary vane engine architecture, but on top of this, as there are no mechanical constraints - we have full control of the vane position, essentially a software crank, and hence achieve: variable compression, HCCI.

In the coming posts we’ll delve into how exactly we harvest the energy of combustion using the electrical machines, how we extract mechanical shaft power, and how we switch between these two modes. In the meantime, here’s a family tree of engines showing where Galin engine sits and a short video I gave at Hackaday in 2022.