Energy Audit Perspectives on Biodiesel-Fuelled Diesel Engines

Energy auditing provides a systematic framework for quantifying energy flows, identifying losses, and improving system efficiency. In diesel engines that increasingly use biodiesel blends as renewable fuels, energy audits serve as diagnostic tools to determine performance, emission behavior, and sustainability. This review synthesizes recent research about the use of energy audits to diesel engines using diesel with biodiesel. It examines performance metrics such as brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), and brake specific energy consumption (BSEC), as well as emission indices and heat-flow distribution. The analysis shows that biodiesel blends, especially up to B20, maintain comparable performance to diesel while reducing emissions of smoke, carbon monoxide, hydrocarbons, and particulates. Slight increases in NOx are observed, which can be mitigated by timing optimization and exhaust-gas recirculation. The paper proposes a standardized audit methodology that integrates thermodynamic, environmental, and economic indicators. This framework can harmonize biodiesel evaluation procedures, reduce duplication of experiments, and accelerate the adoption of sustainable fuels.