Several factors affect engine performance, including fuel injection pressure, injection angle, and injector orifice diameter. Any deviation from normal conditions in any of these aspects can disrupt optimal engine performance, resulting in inefficient combustion and increased exhaust emissions. To investigate the effect of injector hole number, injection hole angle, and injection pressure on the performance and emissions of a diesel engine operating on a diesel/hydrogen blend (10 % hydrogen and 90 % diesel), a single-cylinder direct injection diesel engine was used. Three injector nozzle configurations just for diesel injector with different hole diameters (0.6, 0.3, and 0.2 mm) were used at injection angles of 0, 15, and 30 degrees, respectively. Three injection pressures (200, 400, and 600 bar) were tested, with results monitored for brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), smoke, and NOx emissions. Optimal results were achieved with a maximum injection pressure of 400 bar and a nozzle angle of 15 degrees, resulting in improved engine performance and BTE, along with a 6.5 % reduction in BSFC. Increasing the number of injector holes, injection pressure, and injection angle resulted in reduced BSFC and smoke emissions, but with a significant increase in NOx emissions. Notably, this study deviates from traditional combustion methods by introducing air from a 1.1-atmosphere tank instead of relying solely on natural intake. In addition, hydrogen fuel is introduced into the air manifold via a separate injector with an injection pressure of 20 bar, while diesel fuel is injected directly into the combustion chamber.

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