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Homogeneous charge compression ignition (HCCI), a low temperature combustion (LTC) engine concepts, offers the potential to significantly reduce NOx and particulate, while also produce diesel-like efficiency. However, many technical challenges, including an established fuel performance metric, have hindered the advancement of this technology. In the present work, we used a design-of-experiments approach to address sensitivity of our previously-developed metric for LTC engine fuel performance: the LTC index. Using two different statistical strategies: one-at-a-time (OAT) analysis and 23 factorial design, we targeted driving cycle, weight, maximum power, as well as compression ratio as input parameters to determine their individual and interactive impacts to the LTC index for a wide range of fuels relevant to advanced internal combustion engines research.

SAE International has been requested by the author to retract the above referenced paper. The retracted paper has been withdrawn and will no longer be available online or in print.

Home refueling systems for natural gas vehicles are commercially available but suffer from long refilling times and high system costs. A novel concept of selectively repurposing one cylinder of a compressed natural gas (CNG) engine to be used as a compressor would allow a CNG vehicle to refuel itself quickly and with low capital cost. Using funding from the DOE through the ARPA-E program, such a vehicle is being designed and built by Oregon State University with the help of Czero, Inc. This paper outlines some of the early design, analysis and simulation work done to prove the concept and arrive at a first prototype design. Some of the unique challenges associated with the concept are discussed and the solutions to them are presented. An accompanying paper will present test results for the system.

In this paper we describe the experimental apparatus used to validate concepts associated with a bimodal internal combustion engine for use in natural gas vehicles (NGV's). In one mode, all engine cylinders fire normally providing locomotion for the NGV. In the other mode, one cylinder of the engine is used to compress residential natural gas, in multiple stages, to a standard US compressed natural gas (CNG) vehicle storage tank pressure of 250 bar. In the refueling mode, while the single cylinder is compressing natural gas it is powered by natural gas combustion in the remaining engine cylinders. Here we describe the engine dynamometer testing used to validate the bimodal engine design described in a companion paper. More specifically, a base compression ignition engine is powered by an AC motor while pumping air into storage tanks while all relevant thermodynamic parameters are recorded.

The effects of fuel composition on homogeneous charge compression ignition (HCCI) combustion were studied experimentally in an engine employing negative valve overlap (NVO). Three test fuels, varying in ignition quality and volatility, were investigated for their effect on engine performance and combustion phasing; comparisons were made to a full-run 87-octane base fuel. The three test fuels, which varied in research octane number from 69 to 98, were all found to advance the combustion timing slightly relative to the base fuel, suggesting some differences in the ignition chemistry. The combustion performance at a fixed combustion phasing, however, was found to be comparable, within the limits of the system, for all of the fuels. A major testing issue that limited the system repeatability was the formation of combustion chamber deposits under some operating conditions. A methodology to mitigate these effects was employed with some success.

A laser-based sensor has been developed which generates short multicolored pulses for use with absorption spectroscopy techniques for the collection of thermodynamic information in an HCCI engine. Our sensor is based on supercontinuum generation which is accomplished by coupling a short-duration, high energy laser pulse (the pump) into fiber optics where colors other than the pump are generated through various nonlinear phenomena. The resulting “white pulse” is then stretched out in time by dispersive media (e.g., another fiber) to a time scale which can be collected by a high speed detector and oscilloscope. Although other multicolored (wavelength agile) laser based techniques generated by scanning mirrors or gratings have been applied to HCCI combustion [1], our supercontinuum approach offers a broad range of wavelengths with both high spectral and high temporal resolution from a source with no moving parts.