DIESEL PERFORMANCE

CRC Project No. DP

Leader:      M. Nikanjam

Scope and Objective

The objective of the Diesel Performance Group is to provide technical supporting data for diesel performance issues that are needed by the fuel, engine, equipment, and additive industry and can be used by technical groups such as ASTM and the International Organization for Standardization (ISO).

Current Status and Future Program

The Diesel Performance Group is addressing light-duty diesel (LDD) performance issues.  Several proposals for future work were evaluated by the group.  A LDD Fuel Forum was held at the SAE Powertrain & Fluid Systems Conference & Exhibition in October 2003.  CRC Performance Group panels were formed and program proposals were received in the following areas:

It was recognized that not all of these tasks could be accomplished concurrently.  Initially, the Lubricity Panel will determine the relationship between diesel fuel lubricity as measured by laboratory tests and injection equipment wear for the current and near future LDD engines in the U.S. 

A Low-Temperature Operability Panel will determine if current diesel cold-flow metrics [e.g., pour point, cloud point, cold filter plug point (CFPP), or low temperature flow test (LTFT)] are adequate predictors of actual cold-weather operability of current LDD in the U.S. market. 

For Cetane Number, the CRC AVFL Committee earlier performed a study of the effects of Cetane Number on a small fleet of European model LDDs.  This was published as Report AVFL-11, "The Effect of Fuel Cetane Quality on Light-Duty Diesel Performance."  Future work was recommended by AVFL to the Performance Committee to further investigate the observed unexpected behavior of cetane effects in LDD vehicles.  Other studies will follow when the variety of U.S. LDD models increases.

Diesel Fuel Lubricity Program

A Diesel Fuel Lubricity Panel has completed a program plan, selected a contracting laboratory, and has installed injection systems from two OEM's.  After some extended delay in locating appropriate test articles, SwRI has assembled the test injection units and will initiate testing in September 2007.

The objective of the program is to determine the relationship between diesel fuel lubricity as measured by laboratory tests and diesel engine injection equipment durability for the current and near future LDD injection equipment in the U.S.  The deliverable will be a High Frequency Reciprocating Rig (HFRR) Wear Scar Diameter (WSD), and a Scuffing-Load Ball-on-Cylinder Evaluator (SBOCLE) correlation with wear of typical injection equipment.

This program will perform injection equipment-rig tests using two types of commercial injection systems used in vehicles in the U.S.  Two fuels each with three levels of lubricity (base and additized fuels) will be characterized by HFRR and SBOCLE laboratory lubricity tests to determine the effect of lubricity on injection equipment wear for each injection system. The project testing phase awaits final installation of the two commercial injection systems and controllers at SwRI. Equipment and controller information has been supplied by GM and by Chrysler to start the project.   

Low Temperature Operability Program

The objectives of this program are to evaluate existing low temperature laboratory test methods, such as CFPP and LTFT, and determine their applicability to the operability of LDD engines using data developed from LDD vehicle tests.  The scope of the project will be extended in order to develop new test methods or modify existing test methods if currently employed methods fail to adequately correlate with the vehicle test data.  The deliverable will be a practical laboratory test method that adequately predicts low temperature operability limits for LDD vehicles.

FPP has been used for low temperature operability in Europe for many years.  The LTFT is the test method of choice in the U.S.  With the introduction of more European-like LDD vehicles in the U.S., it is timely to conduct a program to determine if the CFPP method can be used.  An existing CEC testing protocol, CEC M-11-T-91 was used as a guideline in developing a test protocol.  For the CRC low temperature program, BP and Chevron provided ultra low sulfur diesel test fuels.  A request for proposal was issued in November 2005 and the review committee selected Imperial Oil of Canada to conduct the test program. Testing materials (vehicles, fuels, and additives) were assembled and the testing program was completed in June 2006.  Imperial Oil provided concise weekly progress reports to the project panel and completed the testing program on schedule. The laboratory draft Final Report was approved by the Performance Committee members in October 2006. This report will not be released to the public until the data analyses are completed. A data CD is currently available. Yhe Low Temperature Operability Panel is in the process of writing a separate report analyzing the results of the test program and making final recommendations.

Cetane Number Program

The objective of this program is to determine the limit of acceptable operation of North American LDD vehicles as a function of temperature and fuel cetane number quality. It is intended as a follow-up to a program completed by AVFL, "The Effect of Fuel Cetane Quality (Number) Quality on Light-Duty Diesel Performance," in which a number of European LD vehicles were found to be insensitive to Cetane Number variation from 41 to 58, over a temperature range of +10 to -10°C.

The Cetane Number program would extend the investigations to test North American vehicle models at lower temperatures, at least down to -20 °C.  It would be expanded to develop statistical confidence in the results. Multiple repeats of performance runs would be considered, along with a more statistically-designed fuel set to better separate Cetane Number effects from other collinear fuel properties.

A panel was formed and assembled to outline a test plan and identify when appropriate vehicles will be available so that this project can be started as other ongoing activities of the Diesel Performance Group are completed.  The cetane number panel met during the December 2006 ASTM D2 meetings to develop the plan outline that will be circulated for further review and approval.  The Diesel Performance Group recommends waiting until Tier 2 vehicles are available, S15 fuels are in routine production, and several LDD vehicles are available in the U.S. before actually starting the project.

Biodiesel Panel Program

A biodiesel panel was formed recently to address many issues that need to be investigated regarding this renewable fuel that is being used in the diesel market at a growing rate.  Although it serves as a diesel fuel blending component in most cases, there are a number of performance categories that warrant investigation.

Unlike other panels in this group, the biodiesel panel addresses a product instead of a performance category.  Therefore, this panel works closely with other panels to conduct research projects.  The first proposed project deals with low temperature operability.

The proposed study will evaluate the correlation between bench test results and actual vehicle performance.  This will include validation of the propsed ASTM test method for "Precipitates Above the Cloud Point."  The study will follow protocols similar to those used in the recent CRC Diesel Performance Group cold temperature study, and also similar to those described in SAE 962197.

The biodiesel panel is in the process of defining program details and funding options.