Development of fuel flexible gas engine system

In this study, the authors aim to develop a small gas engine system for biomass gas by modifying the control system of a conventional spark ignition engine. Before developing a control algorithm, combustion experiments with various components fuels assuming component of real biomass gases like as fermentation gas and pyrolysis gas were carried out. It was clarified that the relationship between dimensionless combustion duration and equivalence ratio is expressed in first order liner function regardless of fuel components. Indicated thermal efficiency can be also expressed by combustion duration and volumetric efficiency under the condition that COV of IMEP was lower than 5% and pumping loss decreased against volumetric efficiency linearly, and the relationship between . combustion duration and MBT can also be expressed in first order function. By using these relationships, a gas engine control algorithm, which can define target values of equivalence ratio of premixture and ignition timing realizing high thermal efficiency for fuel compositions automatically analyzing in-cylinder gas pressure data in real time, is developed in order to use gaseous fuels produced from biomass resources effectively. Thus, biomass fueled gas engine system is developed by applying the algorithm to the automobile gasoline engine, hardware modification of which were only fuel supply system and flywheel. The engine system was connected to a gasification plant using wood chip and operation test was carried out. As a result, the engine system could set optimum premixture condition and ignition timing, which realized stable and high thermal efficiency operation automatically.