Progress and recent trends in homogeneous charge compression ignition (HCCI) engines

Advanced compression-ignition (CI) engines can deliver both high efficiencies and very low NOX and particulate (PM) emissions. Efficiencies are comparable to conventional diesel engines, but unlike conventional diesel engines, the charge is highly dilute and premixed (or partially premixed) to achieve low emissions. Dilution is accomplished by operating either lean or with large amounts of EGR. The development of these advanced CI engines has evolved mainly along two lines. First, for fuels other than diesel, a combustion process commonly known as homogeneous charge compression-ignition (HCCI) is generally used, in which the charge is premixed before being compression ignited. Although termed “homogeneous,” there are always some thermal or mixture inhomogeneities in real HCCI engines, and it is sometimes desirable to introduce additional stratification. Second, for diesel fuel (which autoignites easily but has low volatility) an alternative low-temperature combustion (LTC) approach is used, in which the autoignition is closely coupled to the fuel-injection event to provide control over ignition timing. To obtain dilute LTC, this approach relies on high levels of EGR, and injection timing is typically shifted 10–15° CA earlier or later than for conventional diesel combustion so temperatures are lower, which delays ignition and provides more time for premixing. Although these advanced CI combustion modes have important advantages, there are difficulties to implementing them in practical engines. In this article, the principles of HCCI and diesel LTC engines are reviewed along with the results of research on the in-cylinder processes. This research has resulted in substantial progress toward overcoming the main challenges facing these engines, including: improving low-load combustion efficiency, increasing the high-load limit, understanding fuel effects, and maintaining low NOX and PM emissions over the operating range.

https://www.engr.colostate.edu/~marchese/combustion10/1.pdf

Advanced compression-ignition engines—understanding the in-cylinder processes

A fuel reactivity controlled compression ignition (RCCI) concept is demonstrated as a promising method to achieve high efficiency – clean combustion. Engine experiments were performed in a heavy-duty test engine over a range of loads. Additionally, RCCI engine experiments were compared to conventional diesel engine experiments. Detailed computational fluid dynamics modelling was then used to explain the experimentally observed trends. Specifically, it was found that RCCI combustion is capable of operating over a wide range of engine loads with near zero levels of NOx and soot, acceptable pressure rise rate and ringing intensity, and very high indicated efficiency. For example, a peak gross indicated efficiency of 56 per cent was observed at 9.3 bar indicated mean effective pressure and 1300 rev/min. The comparison between RCCI and conventional diesel showed a reduction in NOx by three orders of magnitude, a reduction in soot by a factor of six, and an increase in gross indicated efficiency of 16.4 per cen...

https://journals.sagepub.com/doi/pdf/10.1177/1468087411401548

Fuel reactivity controlled compression ignition (RCCI): a pathway to controlled high-efficiency clean combustion

Experiments and Modeling of Dual-Fuel HCCI and PCCI Combustion Using In-Cylinder Fuel Blending

Fuel design and management for the control of advanced compression-ignition combustion modes

Study on the controlling strategies of homogeneous charge compression ignition combustion with fuel of dimethyl ether and methanol

The influence of inlet pressure ( P in) and octane numbers on combustion and emissions of a homogeneous charge compression ignition (HCCI) engine was experimentally investigated. The tests were carried out in a modified four-cylinder direct injection diesel engine. Four fuels with different research octane number (RON) were used during the experiments: 90-RON, 93-RON, and 97-RON primary reference fuel (PRF) blend and a commercial gasoline, 94.1-RON(G). The inlet pressure conditions were set to give 0.1, 0.15, and 0.2 MPa of absolute pressure. The results indicate that, with the increase of inlet pressure, the start of combustion (SOC) advances and the cylinder pressure increases. The effects of the PRF octane number on SOC are weakened as the inlet pressure increased. However, the difference of SOC between gasoline and PRF is enlarged with the increase of the inlet pressure. The successful HCCI operating range is extended to the upper and lower load as the inlet pressure increased. The maximum achievable ...

Effects of Inlet Pressure and Octane Numbers on Combustion and Emissions of a Homogeneous Charge Compression Ignition (HCCI) Engine

The effect of fuel and operating conditions on the combustion process, load range, and exhaust emissions of a homogeneous charge compression ignition (HCCI) engine was investigated in a modified fo...

Bo Zhang

Papers

Study on the controlling strategies of homogeneous charge compression ignition combustion with fuel of dimethyl ether and methanol

Effects of Inlet Pressure and Octane Numbers on Combustion and Emissions of a Homogeneous Charge Compression Ignition (HCCI) Engine

Influence of Fuel and Operating Conditions on Combustion Characteristics of a Homogeneous Charge Compression Ignition Engine

The Effect of PRF Fuel Octane Number on HCCI Operation

Experimental Study on HCCI Combustion of Dimethyl Ether(DME)/Methanol Dual Fuel