There are two basic types of coal mine gases: gas from demethanation of coal deposits, and ventilation gas; containing combustible ingredients (mainly methane, CH4). Effective use of these gases is an important technical and ecological issue (greenhouse gas emissions), mainly due to the presence of methane in these gases. Serious difficulties in this area (e.g. using them as the fuel for internal combustion (IC) engine) occur mainly in relation to the ventilation gas, whereas the gas from demethanation of coal deposits can be used directly as the fuel for internal combustion engines. The proposed solution of this problem shows that the simple mixing of these two gases (without supplying of oxygen from ambient air) is the effective way to producing the gaseous combustible mixture, which can be used for the fueling of internal combustion gas engines. To evaluate the energy usefulness of this way produced combustible mixture the process indicator has been proposed, which expresses the share of the chemical energy supplied with the ventilation gas, in the whole chemical energy of the produced fuel combustible mixture. It was also established how (e.g., by appropriate choice of the mixed gas streams) can be achieved significantly higher values of the characteristic process indicator, while retaining full energy usefulness of the gained gaseous mixture to power combustion engines.
The theoretical analysis of the charge exchange process in a spark ignition engine has been presented. This process has significant impact on the effectiveness of engine operation because it is related to the necessity of overcoming the flow resistance, followed by the necessity of doing a work, so-called the charge exchange work. The flow resistance caused by the throttling valve is especially high during the part load operation. The open Atkinson-Miller cycle has been assumed as a model of processes taking place in the engine. Using fully variable inlet valve timing the A-M cycle can be realized according to two systems: system with late inlet valve closing and system with early inlet valve closing. The systems have been analysed individually and comparatively with the open Seiliger-Sabathe cycle which is a theoretical cycle for the classical throttle governing of the engine load. Benefits resulting from application of the systems with independent inlet valve control have been assessed on the basis of the selected parameters: fuel dose, cycle work, charge exchange work and a cycle efficiency. The use of the analysed systems to governing of the SI engine load will enable to eliminate a throttling valve from the system inlet and reduce the charge exchange work, especially within the range of part load operation.