https://biblio.ugent.be/publication/8589931/file/8609217.pdf

Methanol as a fuel for internal combustion engines

Ethanol vehicles present a significant cold starting problem. Below 11/spl deg/C, ethanol will not form a rich enough fuel vapor-air mixture to support combustion. The addition of 15% gasoline helps to alleviate this problem, by allowing the vehicle to start primarily on the vaporized gasoline compounds. This approach does not completely eliminate the problem while substantially worsening cold start emissions. Supplementing E85 (85% ethanol, 15% gasoline) with hydrogen improves cold starting significantly. An effort was made to determine the minimum amount of hydrogen which could be used to supplement E85 and which would suffice in providing acceptable cold start performance. This was accomplished by experimental injection of pure hydrogen into the intake stream of a dedicated E85 fuelled vehicle. The minimum acceptable level of hydrogen was found to be 8% by volume at cold start conditions of -4/spl deg/C (25/spl deg/F). Initial work on an E85 hydrogen reformation technologies is also reported.

Ethanol vehicle cold start improvement when using a hydrogen supplemented E85 fuel

Flexible fuel vehicles (FFVs) can operate on a blend of ethanol and gasoline in any volumetric concentration of up to 85% ethanol (93% in Brazil). Existing FFVs rely on ethanol sensor installed in the vehicle fueling system, or on an ethanol estimation based on air-to-fuel ratio (AFR) regulation via an exhaust gas oxygen (EGO) or λ sensor. The EGO-based ethanol detection is desirable from cost and maintenance perspectives but it is known to be prone to large errors during mass air flow sensor drifts. Ethanol content estimation can be realized by a feedback-based fuel correction of the feedforward-based fuel calculation using an exhaust gas oxygen sensor. When the fuel correction is attributed to the difference in stoichiometric air-to-fuel ratio (SAFR) between ethanol and gasoline, it can be used for ethanol estimation. When the fuel correction is attributed to a mass air flow (MAF) sensor error, it can be used for sensor drift estimation and correction. Deciding under which condition to blame (and detect) ethanol and when to switch to sensor correction burdens the calibration of FFV engine controllers. Moreover, erroneous decisions can lead to biases in ethanol estimation and in MAF sensor correction. In this paper, we present AFR-based ethanol content estimation, associated sensitivity and dynamical analysis, and a cylinder air flow estimation scheme that accounts for MAF sensor drift or bias using an intake manifold absolute pressure (MAP) sensor. The proposed fusion of the MAF, MAP, and λ sensor measurements prevents severe misestimation of ethanol content in flex fuel vehicles.

AFR-Based Fuel Ethanol Content Estimation in Flex-Fuel Engines Tolerant to MAF Sensor Drifts

Designing production-optimal alternative fuels for conventional, flexible-fuel, and ultra-high efficiency engines

*† The emissions benefits and any negative long-term consequences encountered when using biomass-based fuels and lubricants are discussed. For example, snowmobiles using gasohol/E-10 (10% ethanol, 90% gasoline), have been shown to produce lower emissions. Existing snowmobiles can make use of this fuel without any noticeable degradation in performance or increase in maintenance costs, yet many snowmobilers try to avoid this fuel based upon incorrect hear-say. Further, soy-based oils are commercially available for use in existing engines. They are also biodegradable when incidentally released to the air, land, or water. These products conform to all current legislation regarding air, land, and water pollution. Again, most snowmobile enthusiasts either are unaware of these products, or refrain from their use due to superstition or rumor. This paper studies not only the reduction in emissions resulting from the use of these fuels, but also looks any negative consequences such as possible corrosion due to the use and storage of these fuels or lubricants.

Effect of Biomass-based Fuels and Lubricants on Snowmobiles

Neat alcohol fuels offer several benefits over conventional gasoline in automotive applications. However, their low vapor pressure and high heat of vaporization make it difficult to produce a flammable vapor composition from a neat alcohol fuel during a start under cold ambient conditions. Various methods have been introduced to compensate for this deficiency. In this study, the authors applied computer modeling and simulation to evaluate the potential of four cold-start technologies for engines fueled by near-neat alcohol. The four technologies were a rich combustor device, a partial oxidation reactor, a catalytic reformer, and an enhanced ignition system. The authors ranked the competing technologies by their ability to meet two primary criteria for cold starting an engine at {minus}25 deg C and also by several secondary parameters related to commercialization. Their analysis results suggest that of the four technologies evaluated, the enhanced ignition system is the best option for further development.

/pdf/modeling-and-cold-start-in-alcohol-fueled-engines-2hgf4aefmd.pdf

A.J. Markel

Papers

Modeling and Cold Start in Alcohol-Fueled Engines