Hydrocarbon adsorption mechanism of modern automobile engines and methods of reducing hydrocarbon emissions during cold start process: A review.

With the global emphasis on environmental protection and increasingly stringent emission regulations for internal combustion engines, there is an urgent need to overcome the problem of large hydrocarbon (HC) emissions caused by unstable engine cold starts. Synergistic engine pre-treatment (reducing hydrocarbon production) as well as after-treatment devices (adsorbing and oxidizing hydrocarbons) is the fundamental solution to emissions. In this paper, the improvement of hydrocarbon emissions is summarized from two aspects: pre-treatment and after-treatment. The pre-treatment for engine cold start mainly focuses on summarizing the intake control, fuel, and engine timing parameters. The after-treatment mainly focuses on summarizing different types of adsorbents and modifications (mainly including different molecular sieve structures and sizes, preparation conditions, silicon aluminum ratio, ion exchange modification, and heterogeneity, etc.), adsorptive catalysts (mainly including optimization of catalytic performance and structure), and catalytic devices (mainly including coupling with thermal management equipment and HC trap devices). In this paper, a SWOT (strength, weakness, opportunity, and threat) analysis of pre-treatment and after-treatment measures is conducted. Researchers can obtain relevant research results and seek new research directions and approaches for controlling cold start HC emissions.

Utilization of renewable biodiesel blends with different proportions for the improvements of performance and emission characteristics of a diesel engine.

This work investigated and compared the impact on performance and emission characteristics of diesel engine fueled with five different proportions of biodiesel blends. Firstly, the three-dimensional simulation software CONVERGE was used to create a 3D simulation model of in-cylinder combustion for a diesel engine. Secondly, the experimental data of cylinder pressure and NOx emissions at 50% and 100% loads were employed to verify the simulation model. Finally, the combustion processes of blends with proportions of 0%, 5%, 10%, 15%, and 20% biodiesel were simulated and compared by using the model. The study showed that the brake thermal efficiencies (BTEs) of biodiesel blends with 5%, 10%, 15%, and 20% of biodiesel were increased by 1.24%, 1.89%, 3.13%, and 3.82% at 50% load, respectively, compared with pure diesel. In addition, the soot emissions were decreased by 1.20%, 2.64%, 3.88%, and 4.65%, respectively. However, as the proportion of biodiesel in the biodiesel blends increased, the brake specific fuel consumption (BSFC) and NOx emissions increased. At 50% load, the BSFCs of biodiesel blends with 5%, 10%, 15%, and 20% of biodiesel increased by 0.61%, 1.34%, 1.42%, and 2.17%, respectively, compared with pure diesel. Additionally, the brake powers (BPs) were decreased by 0.64%, 1.31%, 1.88%, and 2.62% at 100% load, respectively.

Effect of Different Ratios of Gasoline-Ethanol Blend Fuels on Combustion Enhancement and Emission Reduction in Electronic Fuel Injection Engine.

The severity of engine emissions for the environment and human health cannot be ignored. This article optimizes the combustion and emission of gasoline-cassava bioethanol fuel blends in electronic fuel injection engines using response surface methodology to achieve the goal of reducing carbon and pollutant emissions. The experiment investigated the effects of different gasoline-cassava bioethanol mixing ratios (G100, G90E10, G80E20, and G70E30) on engine performance, including torque, brake specific fuel consumption, power, total hydrocarbons, nitrogen oxides, and carbon monoxide emissions. The results show that the gasoline-cassava bioethanol fuel blend is not as good as G100 in terms of braking power, torque, and brake specific fuel consumption, but better than G100 in terms of carbon monoxide emissions and total hydrocarbon emissions. Then, the optimization objective function was determined, and the combustion and emission characteristics were optimized using the response surface methodology method. The optimization results indicate that the response surface methodology method can determine the interaction between design variables such as brake specific fuel consumption, nitrogen oxides, and total hydrocarbon emissions and find the best solution. In this experiment, the independent variables of the best solution were 72.9 N·m torque, 30% G70E30 mixing rate, and 2000 rpm speed, corresponding to brake specific fuel consumption at 313 g/(kW·h), nitrogen oxide emissions at 2.85 × 103 ppm, and total hydrocarbon emissions at 166 ppm. The findings of this study indicate that by optimizing the gasoline-cassava bioethanol mixture ratio, lower emission levels can be achieved in electronic fuel injection engines, thereby promoting the sustainable development of renewable energy and reducing pollutant emissions.