Exploring the Efficacy of Port Water Injection on Air–Fuel Ratios and NOx Emissions in Diesel Engines: An Experimental Study

Diesel engines are popular due to their efficiency, power, and fewer carbon emission features. But NOx emissions pose a significant challenge to diesel engines’ use. NOx emissions are the largest constituents of diesel engines’ exhaust pollutants, with proven adverse effects on environment and human health. Different emission control strategies have been in use to inhibit NOx emission in diesel engines and to satisfy the global environmental standards. Port water injection, a relatively new emission control technology offers a solution to effectively inhibit the NOx emissions without significantly changing the standard combustion mode of diesel engines. This study experimentally investigates the impact of port water addition on air–fuel ratios (lambda ratios) and NOx emissions in a high-speed diesel engine. This investigation is carried out through experimentation on the diesel engine connected on a test bench across four operating conditions representing one low, one medium, and two high loading conditions. The experimentation introduced multiple port water injection rates from 0 to 21 kg/h. Results showed a 3–8% reduction in the lambda ratio and a substantial 75–89% decrease in NOx emissions with water addition. Importantly, combustion remained in the standard lean mode, affirming the effectiveness of port water injection in curbing NOx emissions while maintaining the required air–fuel ratio (lambda ratio).