Homogeneous Charge Compression Ignition, or HCCI, is a relatively new combustion technology. It is a hybrid of the traditional spark ignition (SI) and the compression ignition process (such as a Diesel engine). Our project here at the UC Berkeley Combustion Analysis Laboratory (CAL) is to focus on the experimental side of HCCI. Data collected here is being used to validate the computational models generated by engineers at LLNL. We are an integral part of the continuing effort to assess the possibility of an HCCI engine to provide low emission, high efficiency power generation for the ever growing energy demands of this planet.
*Animation edited by G. Leung, Original from Mitsubushi Corp
Unlike a traditional S.I. or Diesel engine, HCCI combustion takes place spontaneously and homogeneously without flame propagation. This eliminates heterogeneous air/fuel mixture regions. See Figure below from New Scientist magazine (January 2006).
In addition, HCCI is a lean combustion process. These conditions translate to a lower local flame temperature which lower the amount of Nitric Oxide (NOx) produced in the process. NOx is a gas that is believed to be responsible for the creation of ozone (O3).
Our project is based on a 1995, 1.9-litre, 4-cyl, SOHC, Volkswagen Turbo Direct Injection Diesel engine with a fixed compression ratio of 18.8:1 (shown below). It has been converted to run in the HCCI mode. The intake air can be preheated with a 18 kW air heater. As of today, various fuels such as propane, butane and methane have been tested on this engine with some positive results. Exhaust gas recirculation was also used to control and improve the performance of this engine.
VW Engine Cylinder Head
VW HCCI Experimental Setup
In addition to the VW engine, our project is also equipped with a Corporate Fuel Research (CFR) single cylinder engine running in HCCI mode (shown below). The compression ratio of this engine can be adjusted during the experiment runs if necessary. It is equipped with a 6 kW intake heater. Many different fuels have been tested on this engine. Currently, variable valve timing control is being developed on this engine to better control HCCI combustion.
CFR Single-Cylinder Engine
Caterpillar 3401 Engine
Recently, our project has added a 2-liter single cylinder Catepillar 3401 diesel engine (see above) and we have converted it to run successfully in HCCI mode. Laser diagnostics will be performed on this engine to measure the "mixed-ness" of the intake charge vs. engine performance.
Recently Published Articles:
Au M., Girard J., Dibble R., Flowers D., Aceves S., Martinez-Frias J., Smith R., Seibel C., Maas U., "1.9-Liter Four-Cylinder HCCI Engine Operation with Exhaust Gas Recirculation," SAE Paper 2001-01-1894
Flowers D., Aceves S., Martinez-Frias J., Smith R., Au M., Girard J., Dibble R.,"Operation of a Four-Cylinder 1.9 L Propane Fueled Homogeneous Charge Compression Ignition Engine", SAE Paper 2001-01-1895
Salvador M. Aceves, Daniel L. Flowers, Charles K. Westbrook, J. Ray Smith, Robert W. Dibble, Magnus Christensen,William J. Pitz, Bengt Johansson,"A Multi-Zone Model for Prediction of HCCI Combustion and Emissions", SAE Paper 2000-01-0327
Daniel L. Flowers, Salvador M. Aceves, J. Ray Smith, John Torres, James Girard, Robert W. Dibble, "HCCI in a CFR Engine: Experiments and Detailed Kinetic Modeling", SAE Paper 2000-01-0328
Robert W. Dibble, Michael Au, James W. Girard, Salvador M. Aceves, Daniel L. Flowers, Joel Martinez-Frias,"A Review of HCCI Engine Research: Analysis and Experiments", SAE Paper 2001-01-2511
(To Order SAE Papers go to www.sae.org)