As engine manufacturers strive to achieve the seemingly incompatible aims of delivering increased power and torque, while using less fuel and creating fewer exhaust emissions, clean diesel has never been such a critical part of the equation. Ultra-high fuel injection pressures, with ever-tighter injector nozzle tolerances, must be supplied by high specification fuel supply systems.
With common rail engines, a high-pressure fuel pump provides a constant supply of pressurised fuel to all of the injectors continuously. Electronically-controlled injectors open at precise intervals, often multiple times per injection cycle, to allow the fuel into the cylinder. As these systems have developed, injection pressures have risen, with many now exceeding 2,500-3,000 bar in the latest Euro 6 Engine Technology.
As mentioned in a report by Cummins Engines, to the 11th International Conference on Stability, Handling and Use of Liquid Fuels, senior technical advisor Norman Blizard noted: “High-pressure common rail is a necessary building block in the total system for emissions solutions.
It offers improvements in NOx, fuel economy, smoke, noise, UHC, CO and particulate control, that would not be available through conventional mechanical or electronic unit fuel injection systems.” Modern injectors have 100-200 micron nozzles, to produce optimum fuel spray and mist. This means that injector contact surfaces can be as small as 1-5 microns, requiring ultra-clean fuels to prevent a reduction in performance.
At these pressures, even the smallest particles within the fuel can scar the surfaces of the fuel delivery system, resulting in increased wear, loss of performance and potential failure. When partial functional failures within the injector occur, it is perceived as best practice to use diesel fuel additives; whilst they can help, they do not rectify the true underlying issues that contribute to injector blockages.
Protection of the high-pressure common rail fuel system on modern diesel engines is one of the most demanding contamination control challenges that we face today. There are various filtration options. These include simple dirt microfilters, coalescing filters to remove free water and dirt, plus water absorbing filters to provide a higher level of removal.
Power generation specialist MTU Onsite Energy says that diesel engine manufacturers now supply filters as a standard accessory and these will have been upgraded to meet higher fuel filtration requirements. Many engines will also be equipped with water separators, with a visual bowl that can be regularly emptied. OEMs and distributors may add additional filtration devices if the application requires above standard levels of filtration.
Recently launched into the Road Transportation sector, the FuelActive pick-up system, will ensure that only the cleanest fuel is used, rather than picking up contaminated material from the bottom of the tank.
In a comprehensive pilot over 6 months with a Global OEM in the UK, FuelActive tractor units consistently delivered the best fuel consumption performance, delivering an aggregate 0.49 mpg / 4.8% improvement in fuel efficiency. FuelActive is “transition technology” for the transport sector on the road to Net Zero emissions.