Integrated Modeling and Validation of HHO-Based Nox Reduction in Spark-Ignition Engines

Toncho Ivanov Boyukov

doi:10.2478/ttj-2026-0003

Abstract

This study presents the design, testing and optimization of a solar-powered HHO generator integrated into a gasoline-powered car (1.6L, 105 hp). The generator (model B1) is powered entirely by a 180 W photovoltaic (PV) panel via an MPPT controller, avoiding additional load on the alternator and improving net electrical efficiency. Exhaust emissions were measured using a TEXA Gasbox2 analyzer, with additional monitoring of the HHO system pressure using a PDS500G sensor. Comparative road tests (100 km) were carried out with and without the HHO generator. The reported results show a 28.6% reduction in NOx emissions (from 0.042 g/km to 0.030 g/km), as well as improvements in CO and HC values. A parametric model for NOx reduction was developed and an optimization scenario with increased photovoltaic power (300 W) and higher cell current was simulated. Theoretical electrolysis efficiency, hydrogen mass production and predicted energy balance were calculated.

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Integrated Modeling and Validation of HHO-Based Nox Reduction in Spark-Ignition Engines

Abstract

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