In this paper the Homogeneous Charge Compression Ignition (HCCI) combustion process is discussed.The objective of this paper is to provide a high efficiency means of fuel utilization.The development of a high efficiency,low emissions combustion process leads to the saving of petroleum based fuels for some more time. The main principle behind this combustion process is the fuel and air are mixed before combustion starts and that the mixture is auto ignited due to the increase in temperature from the compression stroke.Homogeneous Charge Compression Ignition engines combine the very best gasoline and diesel engine properties. This alternative combustion process, which uses lean mixtures is ignited without a spark or flame front. HCCI engines have the potential to provide high,diesel-like efficiencies and very low emissions. In an HCCI engine, a dilute, premixed fuel/air charge auto ignites and burns volumetrically as a result of being compressed by the piston. The charge is made dilute either by being very lean, or by mixing with recycled exhaust gases.
With high octane number fuel the engine operates with high compression ratio and lean mixtures giving CI engine equivalent fuel consumption or better. Due to premixed charge without rich or stoichiometric zones, the production of soot and NOx can be avoided. This paper presents some results from advanced laser diagnostics showing the fundamental behaviour of the process. It was observed that an improvement of fuel efficiency from 15% to 30% at 1.5 bar BMEP. The NOx is normally less than 1/500 of the CI level and no PM is generated by combustion.Homogeneous charge compression ignition (HCCI) combustion could be used to solve the problems of burn duration and flame propagation.
In general ,HCCI combustion has been shown to be faster than spark ignition or compression ignition combustion processes. The main challenge is to control the accurate combustion timing.But this problem can be solved by using some control systems like In-cylinder pressure,Ion trap method etc. There won’t be Detonation(“Knocking” or “Pinging”). Very lean mixtures (low equivalence ratios (f ~ 0.3) )can be used since no flame propagation is required. HCCI engines can operate using a variety of fuels. In the near term, the application of HCCI to automotive engines will likely involve mixed-mode combustion in which HCCI is used at low-to-moderate loads and standard spark-ignition (SI) combustion is used at higher loads.It can be used in variety of applications such as heavy duty vehicles,marine engines, automobiles and internal combustion electric generators etc.
The internal combustion engine is the key to the modern society. Without the transportation performed by the millions of vehicles on road and at sea we would not have reached the living standard of today. We have two types of internal combustion engines the spark ignition, SI, and the compression ignition, CI engines. Both have their merits. The SI engine is a rather simple product and hence has a lower first cost. Though the combustion is clean the problem with the SI engine is the poor part load efficiency due to large losses during gas exchange and low combustion and thermodynamical efficiency. This is mainly due to the throttling. The CI engine is much more fuel efficient and hence the natural choice in applications where fuel cost is more important than first cost. The problem with the CI engine is the emissions of nitrogen oxides, NOx, and particulates, PM. After treatment to reduce NOx and particulates is expensive and still not generally available on the market.