Multi-objective optimization of water injection in spark-ignition engines using the stochastic reactor model with tabulated chemistry

Abstract

Water injection is investigated for turbocharged spark-ignition engines to reduce knock probability and enable higher engine efficiency. The novel approach of this work is the development of a simulation-based optimization process combining the advantages of detailed chemistry, the stochastic reactor model and genetic optimization to assess water injection. The fast running quasi-dimensional stochastic reactor model with tabulated chemistry accounts for water effects on laminar flame speed and combustion chemistry. The stochastic reactor model is coupled with the Non-dominated Sorting Genetic Algorithm to find an optimum set of operating conditions for high engine efficiency. Subsequently, the feasibility of the simulation-based optimization process is tested for a three-dimensional computational fluid dynamic numerical test case. The newly proposed optimization method predicts a trade-off between fuel efficiency and low knock probability, which highlights the present target conflict for spark-ignition engine development. Overall, the optimization shows that water injection is beneficial to decrease fuel consumption and knock probability at the same time. The application of the fast running quasi-dimensional stochastic reactor model allows to run large optimization problems with low computational costs. The incorporation with the Non-dominated Sorting Genetic Algorithm shows a well-performing multi-objective optimization and an optimized set of engine operating parameters with water injection and high compression ratio is found.

Effects of direct water injection and injector configurations on performance and emission characteristics of a gasoline direct injection engine: A computational fluid dynamics analysis

“…They demonstrated a reduction of more than 80% in NO x emissions at the expense of 20% torque reduction using the water-to-fuel (W/F) ratio of 1 at the engine speed of 4000 rev/min. Franken et al 30 used a generic algorithm to perform simulation-based multi-objective optimization of water injection in a turbocharged spark ignition (SI) engine. They achieved about 12% decrease in fuel consumption compared to that of without water due to increased compression ratio at the W/F ratio of 0.4.…”

Special issue: Symposium for combustion control 2019

“…The two previous special issues illustrated the spectrum of the conference, which ranged from advanced control concepts 1–4 to application-oriented contributions with on-road vehicle validation, 5 detailed control of the combustion process on a laboratory scale 6–9 to combustion process simulation. 10…”

Symposium for combustion control 2017 and 2018 special issue

“…The paper selection covers the main topics of the SCC, from advanced control concepts 2-4 to application-oriented papers with on-road vehicle validation 5,6 or detailed engine process control. [7][8][9][10] Innovative sensor and actuator technologies do not only enable greater flexibility in process control but also lead to greater complexity in future drive trains. For better knowledge of the system states, the concept of a ''soft-sensor'' gets a lot of attention, due to the possibility to reduce the hardware complexity and cost.…”

“…10,13 This extended the in-cycle control approach presented in the contribution of Liu et al 14 Another very important aspect of control development always lies on the process simulation. The contribution of Franken et al 9 presented a stochastic reactor model with tabulated chemistry. It was shown that it can be used for a simulative analysis of innovative combustion principles such as water injection and that it can be executed with low computational costs.…”

“…The paper selection covers the main topics of the SCC, from advanced control concepts 2–4 to application-oriented papers with on-road vehicle validation 5,6 or detailed engine process control. 7–10…”