Investigation into Various Strategies to Achieve Stable Ammonia Combustion in a Spark-Ignition Engine

<div class="section abstract"><div class="htmlview paragraph">Engine knock is a major challenge that limits the achievement of higher engine efficiency by increasing the compression ratio of the engine. To address this issue, using a higher octane number fuel can be a potential solution to reduce or eliminate the propensity for knock and so obtain better engine performance. Methanol, a promising alternative fuel, can be produced from conventional and non-conventional energy resources, which can help reduce pollutant emissions. Methanol has a higher octane number than typically gasolines, which makes it a viable option for reducing knock intensity. This study compared the combustion characteristics of gasoline and methanol fuels in an optical spark-ignition engine using multiple spark plugs. The experiment was carried out on a single-cylinder four-stroke optical engine. The researchers used a customized metal liner with four circumferential spark plugs to generate multiple flame kernels inside the combustion chamber. The results indicated that generating multiple flames inside the cylinder caused higher pressures and temperatures, which led to the production of more knocking cycles with higher knock intensities. Additionally, the study showed that methanol combustion produced significantly lower knock intensity with better engine power output compared to gasoline combustion due to its higher octane rating enabling more advanced ignition and its faster flame propagation. The researchers characterized various knock intensities obtained by multiple ignition sites and exhibited a transition from normal combustion to slight knock, medium knock, and high knock cases. Furthermore, the researchers performed high-speed natural-flame-luminosity (NFL) imaging to capture the multiple flame development and autoignition kernels inside the cylinder for various combustion cases. This study provides a detailed understanding of the combustion characteristics of gasoline and methanol fuels in a spark-ignition engine and can be used to further optimize engine performance by reducing knock intensity and increasing engine efficiency.</div></div>

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Development of an Ultra-Low Carbon Flex Dual-Fuel Ammonia Engine for Heavy-Duty Applications

Hegab,

Bowling,

Cairns

et al. 2024

SAE Technical Paper Series

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<div class="section abstract"><div class="htmlview paragraph">The work examined the practicality of converting a modern production 6 cylinder 7.7 litre heavy-duty diesel engine for flex dual-fuel operation with ammonia as the main fuel. A small amount of diesel fuel (pilot) was used as an ignition source. Ammonia was injected into the intake ports during the intake stroke, while the original direct fuel injection equipment was retained and used for pilot diesel injection. A bespoke engine control unit was used to control the injection of both fuels and all other engine parameters. The aim was to provide a cost-effective retrofitting technology for existing heavy-duty engines, to enable eco-friendly operation with minimal carbon emissions. The tests were carried out at a baseline speed of 600 rpm for the load range of the engine (10-90%), with minimum pilot diesel quantity and as high as 90% substitution ratio of ammonia for diesel fuel. Results demonstrated that at high load conditions, ammonia dual-fuel operation could achieve diesel-like efficiency, while reducing engine carbon emissions by 90% and almost eliminating soot. Engine stability was maintained at acceptable levels, while the peak in-cylinder pressure and the maximum rate of pressure rise were reduced by more than 7% and 34%, respectively. Despite slightly lower combustion and exhaust gas temperatures, ammonia dual-fuel operation resulted in higher NOx emissions compared with conventional diesel operation, potentially owing to the nitrogen-rich fuel. The case was reversed at low load conditions, where ammonia dual-fuel operation produced lower NOx emissions but suffered poor combustion and inferior engine performance, relative to conventional diesel operation. Ammonia slip into the exhaust was excessive (exceeding 10,000 ppm) throughout dual-fuel testing.</div></div>

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Investigation into Various Strategies to Achieve Stable Ammonia Combustion in a Spark-Ignition Engine

Cited by 3 publications

References 33 publications

Performance and emission analysis of ammonia-ethanol and ammonia-methane dual-fuel combustion in a spark-ignition engine: An optical study

Performance and emission analysis of ammonia-ethanol and ammonia-methane dual-fuel combustion in a spark-ignition engine: An optical study

A Comparative Study of Knock Formation in Gasoline and Methanol Combustion Using a Multiple Spark Ignition Approach: An Optical Investigation

Development of an Ultra-Low Carbon Flex Dual-Fuel Ammonia Engine for Heavy-Duty Applications

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