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How Quasiturbine Engines Work

Quasiturbine Basics

The Saint-Hilaire family first patented the Quasiturbine combustion engine in 1996. The Quasiturbine concept resulted from research that began with an intense evaluation of all engine concepts to note advantages, disadvantages and opportunities for improvement. During this exploratory process, the Saint-Hilaire team came to realize that a unique engine solution would be one that made improvements to the standard Wankel, or rotary, engine.

Like rotary engines, the Quasiturbine engine is based on a rotor-and-housing design. But instead of three blades, the Quasiturbine rotor has four elements chained together, with combustion chambers located between each element and the walls of the housing.

simple quasiturbine design
Photo courtesy
Simple Quasiturbine design

The four-sided rotor is what sets the Quasiturbine apart from the Wankel. There are actually two different ways to configure this design -- one with carriages and one without carriages. As we'll see, a carriage, in this case, is just a simple machine piece.

First, let's look at the components of simpler Quasiturbine model -- the version without carriages.

The simpler Quasiturbine model looks very much like a traditional rotary engine: A rotor turns inside a nearly oval-shaped housing. Notice, however, that the Quasiturbine rotor has four elements instead of three. The sides of the rotor seal against the sides of the housing, and the corners of the rotor seal against the inner periphery, dividing it into four chambers.

basic housing of quasiturbine engine

In a piston engine, one complete four-stroke cycle produces two complete revolutions of the crankshaft (see How Car Engines Work: Internal Combustion). That means the power output of a piston engine is half a power stroke per one piston revolution.

A Quasiturbine engine, on the other hand, doesn't need pistons. Instead, the four strokes of a typical piston engine are arranged sequentially around the oval housing. There's no need for the crankshaft to perform the rotary conversion.

This animated graphic identifies each cycle. Notice that in this illustration the spark plug is located in one of the housing ports.

basic quasiturbine engine

In this basic model, it's very easy to see the four cycles of internal combustion:

  • Intake, which draws in a mixture of fuel and air
  • Compression, which squeezes the fuel-air mixture into a smaller volume
  • Combustion, which uses a spark from a spark plug to ignite the fuel
  • Exhaust, which expels waste gases (the byproducts of combustion) from the engine compartment

Quasiturbine engines with carriages work on the same basic idea as this simple design, with added design modifications that allow for photo-detonation. Photo-detonation is a superior combustion mode that requires more compression and greater sturdiness than piston or rotary engines can provide. Now, let's see what this combustion mode is all about.

Internal combustion engines fall into four categories based on how well air and fuel are mixed together in the combustion chamber and how the fuel is ignited. Type I includes engines in which the air and fuel mix thoroughly to form what is called a homogenous mixture. When a spark ignites the fuel, a hot flame sweeps through the mixture, burning the fuel as it goes. This, of course, is the gasoline engine.

Four Types of Internal Combustion Engines

Homogenous Fuel-air Mixture
Heterogeneous Fuel-air Mixture
Spark-ignition Type I
Gasoline Engine
Type II
Gasoline Direct-injection (GDI) Engine
Pressure-heated Self-ignition Type IV
Photo-detonation Engine
Type III
Diesel Engine

Type II -- a gasoline-direct injection engine -- uses partially mixed fuel and air (i.e., a heterogeneous mixture) that is injected directly into the cylinder rather than into an intake port. A spark plug then ignites the mixture, burning more of the fuel and creating less waste.

In Type III, air and fuel are only partially mixed in the combustion chamber. This heterogeneous mixture is then compressed, which causes the temperature to rise until self-ignition takes place. A diesel engine operates in this fashion.

Finally, in Type IV, the best attributes of gasoline and diesel engines are combined. A premixed fuel-air charge undergoes tremendous compression until the fuel self-ignites. This is what happens in a photo-detonation engine, and because it employs a homogenous charge and compression ignition, it is often described as an HCCI engine. HCCI (Homogeneous Charge Compression Ignition) combustion results in virtually no emissions and superior fuel efficiency. This is because photo-detonation engines completely combust the fuel, leaving behind no hydrocarbons to be treated by a catalytic converter or simply expelled into the air.

engine ignition comparison
Source: Green Car Congress

Of course, the high pressure required for photo-detonation puts a significant amount of stress on the engine itself. Piston engines can't withstand the violent force of the detonation. And traditional rotary engines such as the Wankel, which have longer combustion chambers that limit the amount of compression they can achieve, are incapable of producing the high-pressure environment necessary for photo-detonation to occur.

Enter the Quasiturbine with carriages. Only this design is strong enough and compact enough to withstand the force of photo-detonation and allow for the higher compression ratio necessary for pressure-heated self-ignition.

In the next section, we'll look at the major components of this design.