The optimal fuel injection strategy for rotary engines

Researchers from the Tomsk Scientific Center SB RAS and Beijing University of Technology conducted numerical and experimental investigation of mixture formation, ignition, and combustion processes to enhance performance characteristics of rotary engines for various purposes. The reported study funded by Russian Science Foundation No. 21-79-00170 were published in Fuel journal.

– One of the urgent tasks is to produce domestic (in Russia) rotary engines for various purposes. The advantages of these engines are simple design, small size, light weight, low noise and vibration levels. Using syngas in this project as a primary fuel which can be produced from various raw materials is a bridge technology for transitioning from carbon-based to hydrogen-based energy sources, – says Sergey Zambalov, researcher of the physical activation laboratory of the TSC SB RAS.

As the authors of the study explain, there are mainly two systems of fuel delivery that can be implemented in rotary engines: port injection (PI) and direct injection (DI). During PI, the fuel is injected into the intake manifolds and enters the combustion chamber with fresh air. PI is characterized by a fuel delivery delay .With DI system, the fuel is injected directly into the combustion chamber with a minimum delay.

Researchers studied a novel concept of syngas dual injection: part of the fuel is delivered by a port injector during the induction stroke, while another part is directly injected during the compression stroke. To use this technology in rotary engines we need to adjust it to the chosen fuel.

This study focuses on the dual injection of syngas with a 50 % H₂: 50 % CO model composition in the rotary engine. The effect of dual injection ratio on mixture formation, ignition, combustion, performance, and emissions was numerically investigated. According to the obtained results, the optimal dual fuel injection strategy under given conditions is to supply the bulk of the fuel to the intake manifold (75–90 %). This increases fuel conversion efficiency by 5–7 % and decreases fuel consumption by 4–6 % compared to PI or DI only.

– Experimental results were verified by our Chinese colleagues. A group of researchers led by Professor Changwei Ji from Beijing University of Technology is the leader in the field of technological aspects of perspective engines and the combustion of various fuels. Our collaboration began a year ago, when our publications attracted colleague’s attention. In addition to publications, in collaboration with our colleagues we are going to work on projects and take part in programs organized and granted by the Ministries of Science and Higher Education of Russia and China, – noted Sergey Zambalov.

The results of the research conducted at the TSC SB RAS will serve to produce domestic rotary compact engines with a power up to 20 horsepower, which is enough for small unmanned aerial vehicles, garden equipment, boat motors, and electricity generators. At the International military-engineering Forum “Army-2023” there are appeared industrial partners interested in our research.