## 1 Introduction  
As a consequence of the continuous growth of the automotive industry, exhaust gas emissions have increased, significantly affecting air quality [1]. On a global scale, the transport sector accounts for 26% of greenhouse gas emissions, and this shows a growing trend year by year [2]. In the cities of developing countries, poor air quality causes the death of approximately 800,000 people every year [3]. European legislators have pointed out that laboratory emission tests do not reflect real-world conditions, particularly in the case of NOx. The New European Driving Cycle (NEDC), which has been in use since 1970, did not reflect real driving conditions, a fact that was highlighted by the 2015 diesel scandal [4]. Driving Emissions (RDE) tests were introduced to overcome this, where emissions are measured under real conditions using Portable Emission Measurement Systems (PEMS). However, since these measurements are influenced by several factors such as traffic, weather, and air quality, they were supplemented by the Worldwide Harmonized Light Duty Vehicle Test Cycle (WLTC), a laboratory test that can be carried out under controlled conditions [5; 6]. Another consequence of the growing demand for vehicles is the accelerated depletion of fossil fuel reserves [7]. Despite this, according to the World Energy Outlook (WEO), 84% of the global energy demand will still be met by fossil fuels [8]. These two main reasons have motivated researchers to explore various renewable energy sources to meet the world's continuously increasing energy needs in the interest of sustainability [9]. Several gasoline extenders are under investigation as at least partial substitutes for gasoline. Hydrogen-gasoline solutions [10] combined with engine exhaust gas optimization [11] seem promising, but here the barrier is the hydrogen's production and logistics. Liquid alternatives are also being researched in depth [12]. For renewable components, aging degradation handling is crucial [13]. Ethanol is an excellent alternative to replace fossil fuels, as it can be produced from renewable sources and is suitable for internal combustion engines. Its oxygen content reduces exhaust gas emissions, while its higher laminar flame speed improves combustion efficiency [14]. The use of alcohol in engines is not a new idea; experiments were already being conducted in the early 1900s, but it has only received significant attention in recent years [15; 16]. Globally, the United States and Brazil are the largest ethanol producers, but in many other countries ethanol has been integrated into commercial gasoline with the help of legislation [7; 17]. In the last 20 years, many researchers have studied the effects of various ethanol-blended fuels on engine performance and exhaust emissions under different conditions. Most of these studies were experimental, while numerical methods have only begun to spread in the past few years. In terms of results, the research consistently shows that increasing the ethanol content in gasoline slightly increases engine performance [18]. Regarding exhaust emissions, results vary. According to some researchers, NOx emissions increase at higher engine speeds due to increased fuel burned. Other researchers have reported opposite results, which they explained by the shorter time available for combustion [19]. As for HC and CO emissions, different research results consistently show that increasing ethanol content reduces these values due to its oxygen content and higher burning speed [20; 21; 22]. Regarding CO2 emissions, the results are also mixed: [PERSON] et al. [23] investigated the effect of ethanol produced from pomegranate blended with pure gasoline on SI engine performance and emission characteristics. According to the results, CO2 emissions increased due to the decrease in CO emissions. In contrast, [PERSON] et al. [24] investigated the effects of anhydrous and hydrous ethanol-gasoline blends on the combustion characteristics and emissions of a port fuel injection (PFI) spark-ignition (SI) engine.