Investigation and demonstration of a rich combustor cold-start device for alcohol-fueled engines

Abstract

Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accurc.cy, completeness, or l1Sefulness of any Information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise doe� not necessarily constttute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. Preface BackgroundThe use of alcohols (methanol or ethanol) as transportation fuels has been identified as one strategy that has the potential to ameliorate some problems associated with the use of petroleum-based fuels. These problems include a growing dependence on imported oil and the persistent contributions that mobile sources make to urban air pollution.Both ethanol and methanol can be produced from renewable resources, and their combustion characteristics result in a different mix of organic emissions compared to petroleum fuels. The propensity of the exhaust to form ozone is generally less than the exhaust from gasoline-fueled vehicles.Unfortunately, the low vapor pressures of the alcohols at low temperatures present problems for starting engines under these conditions. The current solution to this problem is to mix primers with the alcohol fuel that provide sufficient volatility that starting is enabled generally to temperatures around 0°C.Because the primers detract from the favorable emissions characteristics of the alcohols, it would be desirable to have a way to cold start engines operating on "neat" or "near-neat" alcohol fuels. The Present StudyThe present study was undertaken to investigate an approach to cold starting spark-ignition engines. In this approach a portion of the fuel is burned outside the engine under fuel-rich conditions. This rich combustion creates a product stream that contains significant amounts of hydrogen and carbon monoxide (along with other gases such as carbon dioxide, nitrogen, water vapor, and organics). The hydrogen and carbon monoxide are combustible and noncondensable and provide the fuel for starting the engine. Once the engine starts the engine transitions to the normal fuel system. AcknowledgmentsSeveral people contributed to the success of this study. We would like to express our appreciation to the National Renewable Energy Laboratory for supporting the study and to our subcontract technical monitors, Chris Colucci and Peg Whalen, who provided encouragement and advice during the study.ii SummaryWe have completed a study in which we investigated the use of a rich combustor to aid in cold starting spark-ignition engines fueled with either neat ethanol or neat methanol. The rich combustor burns the alcohol fuel outside the engine under fuel-rich conditions to produce a combustible product stream that is fed to the engine for cold starting. The rich c...

Modeling and cold start in alcohol-fueled engines

“…A secondary throttle plate controls the combustor equivalence ratio by dividing the intake air between the bypass section and the combustor section. The bypass air is recombined with the combustor products prior to induction into the cylinder [5].…”