Effect of the HPDI and PPCI Combustion Modes of Direct-Injection Natural Gas Engine on Combustion and Emissions

Abstract

Natural gas (NG) engines have very broad application prospects. The pilot-ignited NG diesel engine can be organized into two combustion modes according to the sequence of oil and gas injection: (1) High-pressure direct injection, where NG is mainly diffused combustion; and (2) partially premixed compression ignition, where NG is mainly premixed combustion. In this study, we used CONVERGE to explore the influence of the NG injection timing on the distribution of the mixture equivalence ratio, ignition characteristics, thermal efficiency, emission, and combustion reaction rate under the two combustion modes. We also used a multi-step soot model to analyze the particle mass and quantity. We showed herein that the NG injection timing significantly affects the mixture distribution in the cylinder, thereby consequently affecting the combustion process. Both very early and very late injection times were not conducive to NG combustion. In addition, the mass, quantity, and diameter of the soot produced by diffusion combustion were larger than those produced with premixed combustion.

Investigations into the Combined Effect of Mahua Biodiesel Blends and Biogas in a Dual Fuel Engine

“…Biogas, CNG and hydrogen can be used as primary fuels in dual fuel engine [26]. Partially premixed combustion is used to improve the combustion by varying the injection timing [27]. RCCI mode is used to utilize both high octane number and high cetane number fuel in CI engine.…”

Retrofit of Diesel Engines with H2 for Potential Decarbonization of Non-Electrified Railways: Assessment with Lifecycle Analysis and Advanced Numerical Modeling

“…According to the literature, the cost of the conversion of a diesel engine to become compatible with natural gas is in the range of EUR 8000 to EUR 12,000 for each engine [40]. The estimated cost includes the following stages:  Engine disassembly;  Revision and eventual replacement of some components;  Replacement of pistons to reduce the compression ratio;  Modification of the cylinder head to place the spark plugs; A more sophisticated and expensive upgrade, like the use of a direct high-pressure injection fuel system, is needed to achieve the previous level of power, leading to a rise in the total transformation costs [38,39]. Figure 5 shows the comparison between the fuel consumption of hydrogen and diesel engines as a function of engine rotational speed at full-load operating points.…”

“…A more sophisticated and expensive upgrade, like the use of a direct high-pressure injection fuel system, is needed to achieve the previous level of power, leading to a rise in the total transformation costs [38,39]. Figure 5 shows the comparison between the fuel consumption of hydrogen and diesel engines as a function of engine rotational speed at full-load operating points.…”