Evaluation of fuel additives and engine conditions on fuel deposit formation and prevention in gdi and pfi engines: an accelerated approach

Norman, Andrew James (2025). Evaluation of fuel additives and engine conditions on fuel deposit formation and prevention in gdi and pfi engines: an accelerated approach. University of Birmingham. Ph.D.

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Abstract

Modern engines require precise control of variables to optimise drivability, power, emissions and efficiency. Fuel deposits disrupt this balance by affecting components such as fuel injectors, Exhaust Gas Recirculation (EGR) coolers, and intake valves. To mitigate this, an understanding of conditions that promote deposits, their impact on performance and prevention methods are essential. This study uses accelerated deposit growth cycles to evaluate how fuel and additives as well as engine and fuel parameters influence deposit growth, prevention, and removal on Gasoline Direct Injection (GDI) injectors, GDI EGR coolers and Port Fuel Injection (PFI) intake valves. An iterative method was established to create an effective accelerated GDI injector deposit growth cycle, which alternated a sequence of high and low loads, with sequence timing critical to deposit growth and additive effectiveness. Additives reduced injection duration increase from 6.8 - 2.1 %, and to 1 % with a renewable fuel. Another method, with an EGR cooler, showed that additives maintained exhaust Total Hydrocarbon (THC) and soot levels, preventing EGR cooler deposits, decreasing pressure loss and intake manifold temperature, with a predicted 1.2 % reduction in Brake Specific Fuel Consumption (BSFC) compared to a base fuel. A deposit formation cycle on PFI intake valves used an experimental rig with a novel design which can control parameters such as valve and cylinder head temperature, air and fuel flow rates, and valve speed. 34.3 mg of deposits were generated in a 5 hr test whilst identifying a critical temperature of 210 ⁰C for deposit formation, replicating real engine trends. This study provides a detailed account of the rig’s design for future experimentation of a similar nature.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):