In general, we know of two types of internal combustion engines used in vehicles – Gasoline and Diesel. The gasoline engine relies on electric sparks for igniting its air-fuel mixture, while the diesel engine relies on heat and compression to do the same. Introduction of new types of renewable fuels such as biodiesel, bioethanol and Hydrogen are leading to newer types of internal combustion engines such as those utilizing HCCI or Homogeneous Charge Compression Ignition.
HCCI uses a type of internal combustion mechanism where fuel is mixed with an oxidizer such as air and the mixture is compressed until it ignites on its own. The exothermic reaction thus created by the combustion of the air-fuel mixture releases its chemical energy and transforms it into a sensible form that the engine can use for generating work and heat.
Extreme machines use HCCI as this method combines the characteristics of conventional diesel and gasoline engines. Diesel engines use CI or compression ignition with SC or stratified charge – abbreviated as SCCI. Gasoline engines use SI or spark ignition with HC or homogeneous charge – abbreviated as HCSI.
An HCCI engine injects fuel during its intake stroke. This is similar to what happens in an HCSI engine. However, unlike the HCSI engine using an electric discharge to ignite the mixture, the HCCI engine compresses the mixture to raise its temperature and density, until the entire mixture reacts completely. This is different from the functioning of the SCCI engine.
An SCCI engine also increases the density and temperature during compression. However, the difference is that it injects fuel only after the compression stroke is completed. This leads to combustion occurring at the boundary of the air-fuel mixture, resulting in higher emissions. Since the method allows a leaner and higher compression burn, SCCI engines are more efficient.
Controlling extreme machines such as HCCI requires precision and a physical understanding of the ignition process. With proper control, such as with a microprocessor, HCCI engines can achieve efficiencies typical of diesel engines and emissions such as gasoline engines do.
Adam Vaughan has developed an adaptive algorithm for controlling extreme machines such as those using the homogeneous charge compression ignition His algorithm runs on the tiny, credit card sized single board computer, the Raspberry Pi or RBPi. The algorithm learns and adapts to the HCCI mechanism in real time.
The near-chaotic combustion process in an HCCI engine is hard to predict. Adam’s algorithm requires roughly 240,000 samples per second of data to predict how the engine is likely to behave. This is very close to real-time monitoring – the latency or lag approaches a mere 300µS.
Data sent to the RBPi includes pressure from each cylinder of the engine, the angle of the crank rod and the heat released. RBPi records this data and uses it to control the engine in real time over a CAN or Controller Area Network. With the real-time control provided by his algorithm on the RBPi, Adam is able to improve the efficiency of the engine and reduce its carbon dioxide emissions drastically. Watch RBPi controlling the extreme engine here and you can read about Adam’s algorithm here.