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Orbital Engine Company
Report to Environment Australia, December 2002
This report represents part of the work commissioned by Environment Australia (EA) under tender 34/2002 'Environment Australia Project: 'Market Barriers to the Uptake of Biofuels Testing Petrol Containing 20% Ethanol (E20)''. Specifically, this report satisfies the section of work Section 188.8.131.52 titled 'Analysis of Impacts'.
A study has been conducted on the suitability of ethanol/gasoline blend fuels containing 10% and 20% (by volume) ethanol for non-automotive engines. The study has focussed on researching areas of engine operability, engine durability and fuel system durability when the engines were operated on ethanol gasoline blend fuels. The study must be considered in the context of the current non-automotive engine population, which must operate safely, effectively and efficiently on the ethanol blends without retuning/recalibration or other modification. During the execution of the literature search it became apparent that only limited information relating to non-automotive engines and ethanol blend fuels was available, with respect to higher ethanol blends up to 20% no literature was uncovered. Generally manufacturers recommendations allow the use of up to 10% ethanol. The majority of information available was often not specific to a particular engine group (aircraft, vehicle, marine or utility), forcing rather general conclusions.
The addition of ethanol to gasoline increases the available oxygen for the combustion process. The study shows that there will be enleanment of the combusted mixture. The severity of the impact of enleanment depends on the relative richness the engines gasoline calibration. If the original gasoline calibration is lean, then the impact of enleanment has the potential to be significant. Enleanment has the potential to have a detrimental effect on: cold starting; hot operation; cold operation and wide open throttle performance. Depending on the type of engine and its calibration, there is potential for engine damage to occur through enleanment. The propensity for this to occur will increase as the proportion of ethanol blend is increased.
Ethanol gasoline blend fuels volatility characteristics may impact on an engines operational characteristic under hot conditions. The increased volatility of ethanol gasoline blend fuels may result in vapour lock when operating the engine in hot conditions, the impact being difficulty restarting, hesitation and stumbling during acceleration, in certain cases it can be severe enough to cause the engine to cut out completely.
Fuel consumption theoretically increases when oxygenates are blended with gasoline due to the lower energy content of the oxygenated fuel. The theoretical increase in fuel consumption for a 10% and 20% ethanol gasoline blend is approximately 3% and 6% respectively. This increase in fuel consumption, due primarily to the reduction in energy content of the fuel, may be offset somewhat in by the enleanment of the fuel/air mixture.
No specific literature was found on the effect of ethanol blends on the wide open throttle (WOT) performance of non-automotive engines. There is however no reason to believe that the potential impacts on non-automotive engines will be significantly different to those described for automotive engines. From the automotive literature review of WOT performance the level of potential deterioration is likely to be dependent on the gasoline calibration of the engine, with the 20% ethanol gasoline blend fuel giving the worst performance.
The impact of the 10% ethanol gasoline blends (E10) on the wear of engines is quite clear. In general it should be negligible compared to straight gasoline as many of the non-automotive engine manufacturers permit the use of up to E10 in their products. There are some exceptions with those manufacturers outlining steps the user should take to ensure satisfactory performance with an E10 blend. For blends greater than E10 the impact is not clear though manufacturers specifically do not warrant their products should they be operated on ethanol gasoline blends beyond 10%. No literature was uncovered that detailed specific testing of non-automotive engine testing with ethanol gasoline blends of approximately 20% by volume ethanol.
Corrosion of non-automotive engines metallic fuel system components through the use of E10 will in general not be an issue. Many manufacturers permit the use of up to E10 in their engines, however some manufacturers report corrosion of fuel system components in older engines, prior to the mid 1980s. Beyond the E10 ethanol blend fuel it is unclear as to the impact as no literature was uncovered that detailed specific testing with 20% ethanol gasoline blend fuels.
Fuel systems elastomeric and plastic components in modern non-automotive engines are in general compatible with E10 ethanol fuel blends. This is based on the fact that most manufacturers permit the use of ethanol gasoline blend fuels up to 10%. With older engines, manufacturers recommend that the plastic and rubber fuel system components be inspected regularly for leaks and/or deterioration. Beyond the 10% level there was no available literature uncovered by the search that provided clear and detailed scientific experimental data indicating that there would not be a detrimental impact.
The potential for fuel systems deposits to be dissolved by ethanol gasoline blend fuels has been identified by the study. The introduction of ethanol gasoline blend fuels into fuel systems may dissolve some of the fuel system deposits which in turn will clog filters and fuel metering devices. This impact is most likely on older used engines which have seen previous use on straight gasoline.
It is expected that the issues and shortcomings in information for E20 blends identified in this report will be appropriately addressed and reported in due coarse by the execution of the scope of work provided within the Orbital Engine Company tender 34/2002.
One area that will not be covered by the above scope of work but deserves special attention is the area of aircraft and aircraft engines. There are aircraft and aircraft engines in Australia that are approved to use automotive unleaded gasoline. Approval does not include gasoline blended with ethanol. It does appear that there are guidelines specifying the outlets that should be used for the supply of automotive gasoline for those approved aircraft or aircraft engines. However the potential does exist for inconsistency in fuel quality, to this end aircraft engine suppliers and safety authorities recommend operators scrutinize each fuel batch to determine the fuels overall quality as well as maintaining a heightened awareness for potential fuel leaks throughout the aircraft fuel system. There is also a recommendation to buy fuel from a large supplier while making all efforts to confirm the fuel being bought is as advertised. A further recommendation by an aircraft engine supplier is that operators of such engines and aircraft obtain a simple alcohol test kit allowing the determination for alcohol to be made as this is the only safe way to be sure the fuel is alcohol free.