*Article* **Optimization of a Multiple Injection System in a Marine Diesel Engine through a Multiple-Criteria Decision-Making Approach**

### **Maria Isabel Lamas 1,\*, Laura Castro-Santos 1 and Carlos G. Rodriguez 2**


Received: 25 October 2020; Accepted: 18 November 2020; Published: 20 November 2020

**Abstract:** In this work, a numerical model was developed to analyze the performance and emissions of a marine diesel engine, theWärtsilä 6L 46. This model was validated using experimental measurements and was employed to analyze several pre-injection parameters such as pre-injection rate, duration, and starting instant. The modification of these parameters may lead to opposite e ffects on consumption and/or emissions of nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC). According to this, the main goal of the present work is to employ a multiple-criteria decision-making (MCDM) approach to characterize the most appropriate injection pattern. Since determining the criteria weights significantly influences the overall result of a MCDM problem, a subjective weighting method was compared with four objective weighting methods: entropy, CRITIC (CRiteria Importance Through Intercriteria Correlation), variance, and standard deviation. The results showed the importance of subjectivism over objectivism in MCDM analyses. The CRITIC, variance, and standard deviation methods assigned more importance to NOx emissions and provided similar results. Nevertheless, the entropy method assigned more importance to consumption and provided a di fferent injection pattern.

**Keywords:** MCDM; marine engine; injection; emissions; consumption
