Design and Integration of Dual-Fuel Conversion Kit for Thermodynamic Optimization of 2 Kilovolt-Ampere Petrol Generators Using Propane Fuel Blends

Abstract

This study presents a comprehensive design, modeling, and performance evaluation of a dual-fuel retrofit conversion kit tailored for a 2.0 kVA single-cylinder spark ignition (SI) petrol generator, enabling seamless operation on Liquefied Petroleum Gas (LPG), petrol, or LPG–petrol blends. The motivation for this research stems from the need to reduce carbon emissions, enhance fuel flexibility, and lower operational costs in small-scale domestic power systems, especially in developing regions. The conversion kit was developed through an integrated mechanical-electronic design approach involving the synthesis of a calibrated aluminum venturi-type mixer, a zero-governor regulator, and a delay-activated dual solenoid valve interfaced with the carburetion system.

Experimental validation was conducted on a retrofitted 2.0 kVA generator operated under four discrete load conditions (0.5, 1.0, 1.5, and 2.0 kW) in three different fuel modes: petrol-only, LPG-only, and dual-fuel (40% petrol and 60% LPG by mass). The brake power (BP), brake specific fuel consumption (BSFC), and brake thermal efficiency (BTE) were computed following first-law thermodynamic principles. LPG operation consistently outperforms petrol, with BTE increasing from 18.0% at 200 W to 24.5% at 1000 W. In contrast, petrol yields BTE values from 17.2% to 22.1% over the same load range. respectively. BSFC reduced significantly in dual-fuel operation to 0.32 kg/kWh compared to 0.41 kg/kWh in petrol-only mode, suggesting better combustion efficiency and lower fuel consumption per unit of output. Emission analysis revealed that CO and unburned hydrocarbon emissions declined by 44.1% and 35.2% respectively in dual-fuel mode compared to petrol combustion, attributable to the cleaner-burning properties of LPG and improved air-fuel mixing.

A full cost-model analysis based on materials sourcing and fabrication processes was also conducted. The complete unit production cost of the conversion kit was estimated at $22.75, with sensitivity analysis indicating that bulk production could reduce the cost to below $19.00 per unit. The economic advantage was further emphasized by a 28.4% reduction in operational fuel cost over 200 hours of usage. The retrofit was achieved without altering the generator’s existing engine block or ignition system, making it easily deployable for low-income and off-grid communities.

The findings suggest that the proposed conversion kit not only enhances the thermodynamic performance of small SI engines but also contributes meaningfully to environmental sustainability by curbing carbonaceous emissions. This work establishes a technical foundation for subsequent development of microprocessor-controlled LPG injection systems for variable-speed engines and opens a pathway for scalable dual-fuel generator retrofitting technologies in sub-Saharan Africa and similar contexts