Steady-state and transient diesel engine test cycles: Issues associated with the introduction of bio-fuels

The adoption of bio-fuels in the automotive and transport sector has begun to introduce challenges to existing steady-state and transient test cycles, which were designed with petroleum fuels in mind. Bio-fuels have significantly different fuel properties, combustion chemistry and emissions to that of petroleum fuels. Therefore it is necessary to evaluate existing steady-state and transient test cycles with current and future bio-fuels in order to determine their suitability and to consider if any changes to the cycles should be implemented. The European Union issued a directive to use biofuels up to a level of 5.75% of the sold fossil fuels in the transport section by the end of 2010, increasing to 10% by the year 2020. Similarly, the US government has shown a strong preference to increase the share of biofuels in the market. In addition to this concern, there has recently been significant effort to ensure that engine test cycles more accurately reflect the actual conditions experienced by engines in fleets of vehicles. Field data is being compared to steady-state and transient test cycles in order to make this assessment. In this poster we evaluate three test cycles for their suitability for use with bio-fuels, and their relationship to actual fleet engine conditions: the European Stationary Cycle (ESC), Non-Road Transient Cycle (NRTC) and a custom transient cycle. However, the study of the operation of internal combustion engines has mostly been in steady-state conditions, whereas day-to-day fleet vehicles are inherently transient. In fact, only a very small portion of engines operate in steady-state or quasi-steady state conditions. During transient operation, variation in fuel injection, engine speed and load are frequently changing. Testing of new fuels should be done under steady-state operating condition as well as transient operating conditions. The ability of steady-state or transient engine test cycles to represent engine field operation will be evaluated using laboratory tests from the QUT Biofuel Engine Research Facility (BERF) and compared to key published works on exhaust emissions. The BERF has a full suite of gaseous and particulate emission measuring instruments, and has been working to explore new sources of biofuels, along with investigating their influence on engine performance and exhaust emissions. Comparison to field data collected from heavy diesel vehicles used in the mining industry will be made.