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Tsinghua, BYD team explores combustion and emissions of gasoline/ammonia engine

A team from Tsinghua University, with colleagues from BYD research, investigated the impact of NH3 blending on combustion and emission characteristics of a stoichiometric spark-ignition gasoline engine, with a particular emphasis on nitrogen-based emissions.

The experimental investigation was complemented by chemical kinetic calculations. A paper on their work is published in the journal Fuel.

The experimental investigation was complemented by chemical kinetic calculations. The results showed that NH3 blending could effectively suppress engine knock, optimize combustion phase and improve thermal efficiency. For pure gasoline, advancing the spark timing resulted in increased NOx emissions. However, when NH3 was blended, NOx emissions decreased with advancing spark timing, indicating a negative correlation with pressure.

The NH3 emission was attributed to the ‘crevice mechanism’ as well as the absorption/desorption in the lubricant oil film on the cylinder wall.

Chemical kinetic analysis revealed that the NOx emission from NH3 blended combustion is closely related to reactive radicals such as OH, H and O. The reduction in NOx emissions under high-pressure conditions was primarily attributed to the consumption of these reactive radicals via three-body reactions. Interestingly, NOx emissions initially increased with increasing nh3 blending ratio but eventually followed a decreasing trend. This can be attributed to the lower combustion temperature, lower concentration of reactive radicals, and enhanced de-NOx reactions.

—Liu et al.


  • Shang Liu, Zhelong Lin, Yunliang Qi, Guoxiang Lu, Bo Wang, Li Li, Zhi Wang (0024) “Combustion and emission characteristics of a gasoline/ammonia fueled SI engine and chemical kinetic analysis of NOx emissions,” Fuel, Volume 367, doi: 10.1016/j.fuel.2024.131516.


Roger Pham

If you already have NH3 on board, then you can use that for the Selective Catalytic Reduction unit to enable stratified-charge lean-burning gasoline engine to boost efficiency while bringing NOx to near zero. A small quantity of NH3 on board for the SCR unit is Ok, but if NH3 used in fuel quantity would be too dangerous in case of fuel tank rupture due to the high toxicity of NH3.

High-compression stratified-charge direct-injection lean-burning turbocharged gasoline engine can attain diesel level of fuel efficiency, while consuming far less NH3 in the SCR than diesel engine in normal cruise mode.


Hi Roger:

Not to do with ammonia in engines, but I tried several times to reply to you here but there was a software gliche:

It was to the effect that it is not just in the US that light aviation fuel remains leaded, that is also the case in the UK.

And that another presumably substantial source of particulate emissions is from braking aircraft.

An Airbus A380 has 22 tires, each of which loses around 1.5 lbs of rubber on landing, much of which is burnt onto the runway, which needs regular scraping, but presumably there are also very substantial particulate emissions, or at least that would be my speculation as I can't track down figures.

Not great for those who live anywhere near an airport.

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