Smart Combustion Technology


Reactivity Controlled Compression Ignition (RCCI) is a combustion concept that can be considered as a hybrid between Spark Ignition (SI) and Conventional Diesel Combustion (CDC). This combustion concept is the technical viable relative to Homogeneous Charge Compression Ignition (HCCI), which has the same advantages of a very high efficiency combined with very clean emissions, without exhaust gas aftertreatment. The DOCAT 3500AR engine runs RCCI to provide the best possible performance with Stage V emission standard in an retrofitted diesel engine.

Reactivity Controlled

RCCI is always operated with at least 2 different fuels with different reactivity, one high octane fuel and one low octane fuel. The low octane fuel is typically direct injected while the high octane is port injected. The direct injection is timed in the compression stroke to gain enough time to mix to a certain degree with the high octane fuel and air. This mixing happens in a rather homogeneous manner, the injection timing determines the amount of fuel stratification in the cylinder.

Compression ignition

This combustion process uses auto-ignition just like Conventional Diesel Combustion (CDC) engines, however at the moment of ignition the charge is rather homogeneous like in Spark Ignition (SI) engines. The moment of ignition is determined by the stratification of the fuel and the ratio between the high and the low octane fuel, that is why it is called Reactivity Controlled Compression Ignition.

High efficiency

The main reason why RCCI is exceptional efficient is that the heat release of the combustion has a high degree of controllability, which means that the thermodynamic efficiency can be fully optimized. To damp the chemical reactions we operate the engine in lean burn which also reduces the heat losses. When running CDC a lot of the heat is transferred to the walls because of the high peak temperatures of burning diesel sprays. Because RCCI is operated rather homogeneous the temperatures in the cylinder is also rather homogeneous, which leads to less heat loss. We achieved an efficiency of 51.5% for our DOCAT 3500AR engine. According to many researchers, an engine optimized for RCCI achieve an efficiency of 58%.

Low emissions

The lean and homogeneous burn is the main reason the peak temperatures can be kept low, which explains the very low NOx emissions of RCCI. The premixed lean combustion of RCCI results in an exceptionally low soot emission. The high controllability gives us the ability to control the peak cycle temperature which determines the Carbon Monoxide (CO) and Methane (CH4) emissions. We achieved a Stage V emission standard for our DOCAT 3500AR engine without exhaust gas aftertreatment. According to many researchers, an engine optimized for RCCI can achieve EURO6 emission standards without exhaust gas after treatment

Single Fuel RCCI

RCCI has to be operated with 2 different fuels, one high octane fuel and one low octane fuel. In automobile applications this can be seen as cumbersome and can discourage people to choose for RCCI. An solution is that for the high octane fuel a particular fuel is used and for the low octane fuel that same particular fuel but with added cetane-booster. The added cetane-booster requires a refill of 5 liters every oil change, which could be done by the car mechanic. In this way the car owner has all the benefits of owning a RCCI car without having to worry about fueling two different fuels.  

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