DIESEL PERFORMANCE
CRC Project No. DP
Leader: M. Nikanjam
Scope and Objective
The objectives of the Diesel Performance Group are to provide technical supporting data for diesel performance issues that are needed by the fuel, engine, equipment, and additive industry and that 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 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 have since been developed for the following areas:
- Lubricity
- Low Temperature Operability
- Cetane Number
- Fuel Cleanliness
- Density Range
- Biodiesel
It is recognized that not all of these tasks can be accomplished concurrently. Initially, the Lubricity Panel was selected to 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 was formed to 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 performed a study of the effects of Cetane Number on a small fleet of European model LDDs. This was published in September 2004 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 have been started in the biodiesel area, and others will follow as the variety of U.S. LDD models increases.
Fuel Cleanliness and Density Range topics are under review by the committee, but no new projects have been developed for funding consideration. A new project panel on Deposits has been organized to address injectors deposits and other deposition mechanisms in LDD systems.
Diesel Fuel Lubricity Program
The Diesel Fuel Lubricity Panel completed a program plan, selected a contracting laboratory, and the contractor installed injection systems for testing. 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 scope included 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) were to be characterized by HFRR and SBOCLE laboratory lubricity tests to determine the effect of lubricity on injection equipment wear for each injection system. Equipment and controller information were supplied by GM and Chrysler.
After a delay in locating appropriate test articles, SwRI assembled test injection units and initiated testing in February 2008. Initial test runs resulted in near immediate failures on both high and low lubricity test fuels. The test procedures were modified and new injection pumps tested with repeatable results as might be expected for high and low lubricity test fuels. The new procedures are being documented along with test results from the study. A final draft report is expected before the end of 2008 from the contractor at SwRI.
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 may 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 ideally be a practical laboratory test method that adequately predicts low temperature operability limits for LDD vehicles.
CFPP 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 Coordinating European Council (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.
Materials (vehicles, fuels, and additives) were assembled by Imperial Oil 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 Final Report was approved by the Performance Committee members in October 2006. The Low Temperature Operability Panel prepared a separate report analyzing the results of the test program and making final recommendations. The combined reports were bound as the final deliverable for Project DP-2-04 and released November 2007 as CRC Report No. 649.
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°C 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 colinear 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 testing in 2008 if funds can be identified. The study requires Tier 2 vehicles, S15 fuels, and several LDD vehicles to be available in the U.S.
Biodiesel Panel Program
The Biodiesel Panel was formed recently to address many issues that need to be investigated regarding this renewable fuel that is being used 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 project dealt with low temperature operability of biodiesel blends.
The proposed study evaluated the correlation between bench test results and actual vehicle performance. This included validation of the proposed ASTM test method for “Precipitates Above the Cloud Point.” The study followed 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 National Biodiesel Board (NBB), EMA, and NREL joined with CRC to evaluate several blends of petroleum diesel and biodiesel in a low temperature operability study conducted at the Imperial Oil test facility in Sarnia. This project started in December 2007, and the physical test program was concluded in early 2008 with a draft laboratory report supplied by Imperial Oil to the project panel. NREL led development of the final analysis report for the project which was approved by the committee in June and released for publication as CRC Report No. 650. A summary presentation of results was given at the June ASTM meeting in Vancouver. A follow-on study has been developed with sponsorship from NBB and NREL to collect additional data and is now underway at the AWCD facility at Imperial Oil.
