Cold Start Combustion Characteristics in Diesel Engines

Cold start combustion in diesel engines is characterised by low ambient temperatures that impair fuel atomisation, prolong ignition delay and increase unburned hydrocarbons, carbon monoxide and particulate emissions. The elevated viscosity and poor cold flow properties of diesel fuel at subzero temperatures delay spray breakup, leading to incomplete mixing and wall-film formation. Heat loss to cold combustion-chamber surfaces further retards flame development and prolongs cranking duration. Practical strategies to mitigate these effects include intake air preheating, optimised injection pressure and timing, fuel additives or alternative blends, and active thermal management of the combustion chamber. Robust control of these variables is essential to meet global emission regulations, improve fuel economy during the critical warm-up phase and extend component life in cold climates.

Research from Nature Portfolio

Experimental studies have quantified the transient heat transfer within a high-temperature wall encountering diesel spray impingement under engine-relevant conditions. Findings demonstrate that increasing injection pressure and lowering ambient temperature both elevate the instantaneous surface heat flux and heat transfer coefficient. However, as the initial wall temperature rises from 200 °C to around 520 °C, heat flux peaks before declining, reflecting a shift in the dominant heat-transfer regime. A dimensionless correlation based on Biot and Fourier numbers was developed to predict the evolving ratio of wall thermal resistance to convective resistance. These insights into spray–wall heat exchange offer guidance for optimising chamber surface coatings and injection parameters to reduce cold-start energy losses.

Cold Start Combustion Characteristics in Diesel Engines publication trend

The graph below shows the total number of articles in cold start combustion characteristics in diesel engines across all publications each year (not limited to Nature Index journals).

Technical terms

Ignition delay: Interval between start of fuel injection and the onset of combustion, influenced by mixture formation and temperature.

Spray-wall impingement: Interaction of fuel spray with chamber walls that affects heat transfer, film formation and local mixture stratification.

Intake air preheating: Process of raising the temperature of incoming air to improve fuel evaporation and reduce ignition delay under cold conditions.

Cold flow properties: Characteristics such as viscosity and pour point of fuel at low temperatures that govern pumpability and atomisation quality.

Particulate number: Count of soot and solid particles emitted per unit volume, serving as a metric for combustion cleanliness.

References

1. Reducing Cold Start Emissions from Automotive Diesel Engine at Cold Ambient Temperatures. Aerosol and Air Quality Research (2016).
2. Impact of Biodiesel Blends and Di-Ethyl-Ether on the Cold Starting Performance of a Compression Ignition Engine. Energies (2016).
3. The effect of nozzle diameter, injection pressure and ambient temperature on spray characteristics in diesel engine. Journal of Physics Conference Series (2017).
4. Effect of the Preheating Strategy on the Combustion Process of the Intake Manifold Burner. Applied Sciences (2022).