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In this study, a single-cylinder HCCI engine was used to study the technical feasibility of HCCI engines for stationary power generation applications. The compression ratio (CR) of the engine was set at 13.8:1 considering a hybrid system with diesel micro-pilot injection. The engine was operated under various loads at a rated speed of 1800 rpm. Intake manifold temperature of the air/fuel mixture was used to control the start of combustion (SOC) of the HCCI engine. Oil and coolant temperatures were set at 100°C. Location of peak in-cylinder pressure (PPL) was maintained within 6∼9°ATDC in order to obtain maximum thermal efficiency by initiating the SOC between 2∼4°BTDC. Intake boost was increased up to 2.5 bar absolute to increase engine power output. Results of the HCCI combustion were also compared with those of diesel and diesel micro-pilot natural gas combustion. The results showed that the required intake temperature ranged from 149°C to 261°C depending on engine loads. The highest net mean effective pressure (NMEP) was about 10.6 bar. Higher intake boost pressure would increase NMEP even higher. Maximum indicated thermal efficiency (ITE) was about 49% at the excess air ratio (λ) of 3.2 and maximum combustion efficiency was about 94% at λ = 2.6. Oxides of nitrogen (NOx) emissions were below 10 ppm when λ was above 3. At these excess air ratios, in the good HCCI operating regimes, carbon monoxide (CO), total hydrocarbons (THC), and methane (CH4) were equivalent to those of conventional natural gas engines.

Engine manufacturers and researchers in the United States are finding growing interest among customers in the use of opportunity fuels such as syngas from the gasification and pyrolysis of biomass and biogas from anaerobic digestion of biomass. Once adequately cleaned, the most challenging issue in utilizing these opportunity fuels in engines is that their compositions can vary from site to site and with time depending on feedstock and process parameters. At present, there are no identified methods that can measure the composition and heating value in real-time. Key fuel properties of interest to the engine designer/researcher such as heating value, laminar flame speed, stoichiometric air to fuel ratio and Methane Number can then be determined. This paper reports on research aimed at developing a real-time method for determining the composition of a variety of opportunity fuels and blends with natural gas. Interfering signals from multiple measurement sources are processed collectively using multivariate regression methods, such as, the principal components regression and partial least squares regression to predict the composition and energy content of the fuel blends. The accuracy of the method is comparable to gas chromatography.

Today, renewable fuels such as biogas are being used to fuel combined heat and power (CHP) and distributed generation (DG) systems. The composition of biogas delivered to power generation equipment varies depending upon the origin of the anaerobic digestion process and site-specific factors. For improved process control and optimum utilization of CHP/DG systems, the biogas composition needs to be monitored. A new apparatus has been developed for characterization of hydrocarbon fuel mixtures. The method utilizes near infrared absorption spectroscopy to monitor composition and heating value of landfill gas, natural gas, and other hydrocarbon fuel gases. The measurement is virtually instantaneous. A commercialized version of this sensor is expected to cost less than half the price of gas chromatographs, which are widely used in the gas industry today.

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