Investigation of Deposit Formation in the Ignition Quality Tester, 03-9334Printer Friendly Version
Inclusive Dates: 07/03/02 - Current
Background - SwRI developed a constant volume combustion apparatus for rating the ignition and combustion characteristics of diesel engine fuels. This technology, which has been applied in several funded projects with great success in identifying the important aspects of fuel ignition and combustion, was licensed to another company. The licensing company is currently marketing the concept, known as the Ignition Quality Tester (IQTTM), as a replacement for the current diesel fuel cetane number rating apparatus and technique.
This quick-look study is aimed at identifying the fundamental cause of a problem that is currently limiting further development of the IQT. The problem is a systematic drift in the apparatus that appears to be related to the formation of deposits on the inside of the combustion chamber of the IQT. The research element of the proposed study is to identify the fundamental cause of the deposits and the interaction of the deposits on the fuel injection and ignition processes in the IQT. The program was performed as a quick look because of two factors. The investigators are promoting the IQT, combined with a single-cylinder engine, as a study to the Clean Diesel III (CD III) Consortium to start this project year. The consortium has raised an issue relative to the effects of fuel injection and surface interactions. The second factor is the need to solve the deposit problem so that SwRI can participate in a current round-robin test of the IQT for cetane number rating.
Approach - The approach is driven by several deadlines. Initially, the unit will be cleaned and calibrated to support the American Society for Testing and Materials (ASTM) round-robin testing. The failure mode of deposit accumulation will be duplicated to identify which fuels have the propensity to form deposits. Alternative methods of cleaning will be examined. Alternative calibration fuels will be considered. These approaches will also answer questions posed by the Clean Diesel III members and promote work in the IQT for the fourth year. Modifications to the combustion apparatus will also be examined to prevent deposit formation.
Accomplishments - The program is still active. Deposit formation has been observed on the pressure transducer end of the combustion chamber. The pressure transducer is water-cooled, causing this end of the combustion bomb to run cooler than the wall surfaces. Thermally baking the chamber with the transducer removed removes the deposits, but the IQT must then be aged for two days before the results stabilize. Other cleaning methods are being considered. The ASTM round-robin testing was supported, and the results were promising for acceptance as a certified ASTM procedure. The SwRI IQT provided results that were very near the average of nine other units. An official ASTM number is expected to be assigned by February of 2003. One anomaly that contributes to instability has been identified. The electric heaters can malfunction when they reach the operating temperature. Current measurements of all nine heaters have shown two heaters do not provide the full capacity at operating temperatures. The heaters have been replaced.
Ignition Quality Tester