Octane Numbers of Ethanol-Gasoline Blends: Measurements and Novel Estimation Method from Molar Composition Ford Motor Company

Format:

Conference/Event

Author/Creator:

Anderson, Anderson, author.

Contributor:

Bizub, Jeffrey J.

Foster, Michael

Leone, Thomas G.

Lynskey, Michael G.

Polovina, Dusan

Shelby, Michael H.

Wallington, Timothy J.

Conference Name:

SAE 2012 World Congress & Exhibition (2012-04-24 : Detroit, Michigan, United States)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2012

Summary:

Ethanol has a high octane rating and can be added to gasoline toproduce high octane fuel blends. Understanding the octane increasewith ethanol blending is of great fundamental and practicalimportance. Potential issues with fuel flow rate and fuelvaporization have led to questions of the accuracy of octanemeasurements for ethanol-gasoline blends with moderate to highethanol content (e.g., E20-E85) using the Cooperative Fuel Research(CFR) engine. The nonlinearity of octane ratings with volumetricethanol content makes it difficult to assess the accuracy of suchmeasurements.In the present study, Research Octane Number (RON) and MotorOctane Number (MON) were measured for a matrix of ethanol-gasolineblends spanning a wide range of ethanol content (E0, E10, E20, E30,E50, E75) in a set of gasoline blendstocks spanning a range of RONvalues (82, 88, 92, and 95). Octane ratings for neat ethanol,denatured ethanol, and hydrous ethanol were also measured. One setof measurements was conducted using a CFR engine equipped withmanufacturer-supplied enhancements (GE Energy Waukesha XCP-OAdigital octane panel) for digital knock measurement and precisecontrol of temperatures and fuel flow. A second set of measurementswas conducted at a separate laboratory with a CFR engine equippedwith an adjustable-orifice fuel jet. Both approaches address fuelflow issues at high ethanol concentrations.A linear molar octane blending model was found to describe mostof the nonlinearity in the RON and MON data, but measured valueswere still somewhat greater than predicted. Deviations from thelinear model can be described by a term with 2nd-order dependenceon ethanol content with a single scaling parameter (Pg).The parameter Pg can be estimated from the measuredoctane number of a 50:50 molar alcohol-gasoline blend and theoctane numbers of the gasoline (ONg) and alcohol(ONa). The octane number of any ethanol-gasoline blend(ONb) with that blendstock can then be estimated (within1 ON) from the molar fraction of the alcohol (xa) usingthe following expression: ONb =(1-xa)ONg + xaONa +Pg xa (1-xa)(ONa -ONg).This study supports a companion paper (SAE 2012-01-1277) inwhich a state-of-the-art single-cylinder engine equipped withmultiple fuel injection systems was used to evaluate theknock-limited performance of the ethanol-gasoline blends describedherein and to evaluate the relevance of octane ratings and heat ofvaporization as predictors of this performance

Notes:

Vendor supplied data

Publisher Number:

2012-01-1274

Access Restriction:

Restricted for use by site license