Effects of Multiple Injection Strategies on Heavy-Duty Diesel Energy Distributions and Emissions Under High Peak Combustion Pressures

Abstract

Peak combustion pressures (PCP) are increased in heavy-duty diesel engines to obtain higher thermal efficiency. Fuel injection strategy has been a major measure to improve the combustion and emissions of diesel engines. But most existing work of multi-injection strategies was not limited by PCP or was conducted under lower PCP (∼15 MPa). In this study, an experimental study is conducted to further improve the understanding of injection strategies on engine performance under a relative higher peak combustion pressure at 20 MPa. The four tested injection strategies are single main injection, pilot-main injection, main-post injection, and pilot-main-post injection. The effects of PCP on brake thermal efficiency (BTE) and other engine performances are also investigated under the same NOx emissions conditions. Results indicate that more advanced injection timing can obtain higher BTE, while the injection pressure has less effects on BTE as it is higher than 120 MPa. For double-injection, the smaller interval on pilot-main or main-post and the less pilot or post mass improves BTE and emissions. The PCPs are linearly correlated to the BTE, peak average temperature, and peak pressure rise rate (PRR), and the increment of BTE, peak average temperature, and peak PRR are about 0.3%, 30 K, and 0.1 MPa/CA for every 1 MPa increase in PCP, respectively. This also means that the improvement on BTE by the increase of PCP imparts greater thermal and mechanical loads on engine materials and components. At 20 MPa PCP, based on the optimized injection strategies, the BTE of all four strategies is about 42.8%, and the peak PRR of all four strategies is about 0.8 MPa/CA. At a given NOx emission of 17.4 g/kWh and approximate 20 MPa PCP, all four injection strategies have minor effects on distribution of fuel energy and emissions. Therefore, it can be concluded that the injection strategies have fewer effects on BTE and emissions at the higher peak combustion pressure of 20 MPa; the main purpose of injection strategies is to reduce the peak PRR or reach the potentially required temperature for aftertreatment devices.

Particulate Matter Emission and Air Pollution Reduction by Applying Variable Systems in Tribologically Optimized Diesel Engines for Vehicles in Road Traffic

“…From the aspect of PM and soot emission reduction, a significant contribution was made by the application of modern technologies for diesel fuel injection systems [15,16].…”

“…Pilot fuel injection enables the pre-mixing of fuel and air, while subsequent injection contributes to the combustion of unburned combustion products, which reduces emissions and fuel consumption. A split diesel injection strategy with pilot fuel injection enables the pre-mixing of fuel and air, while subsequent injection contributes to the combustion of unburned combustion products, which reduces emissions and fuel consumption [16,17].…”

The Effect of Internal Combustion Engine Nozzle Needle Profile on Fuel Atomization Quality

“…This possibly applies to the homogeneous atomization of the fuel in the entire volume of the combustion chamber, proper fragmentation of the fuel dose fed into the cylinder, and even mixing of fuel and air in the entire combustible mixture. The listed characteristics of the combustible mixture are usually obtained by appropriately shaping the air intake duct (the spiral-shaped inlet and swirling blades) [1,2], the combustion chamber [3] (the shape of the piston crown and the shape of the surface of the cylinder head closing the combustion chamber) [4,5], the proper atomization of the fuel by the injector [6,7], additional devices and ignition delay [8], and fuel injection strategy [9].…”

A Study on the Injection Rate Characteristics of the Solenoid Common-Rail Injector Under Using a High-Pressure Fuel System

“…According to a study by A. L. Niculae et al [10], the optimal rate of injection shape (triangular, trapezoidal, and boot) can simultaneously reduce NOx and soot by 11%, respectively 4% for maximum brake torque and by 22%, respectively 7% for maximum brake power using biodiesel B20, injection rate shape type Boot 2. Research by Z. Zhang et al [11], V. Macian et al [12], the shape of the injection rate profile (square, boot, ramp) as well as multiple injection strategies significantly induced the engine combustion and emission processes. D. A. Nehmer and R. D. Reitz [13], P. Karra, and S.C. Kong [14], who researched injection strategies, determined that onetime fuel injection with a high injection pressure of 200MPa produced the lowest soot emission.…”