Wojciech Bueschke

Analysis of a dual-fuel combustion engine fueled with diesel fuel and CNG in transient operating conditions

The paper presents the thermodynamic analysis of the engine supplied with small and large diesel fuel doses while increasing natural gas quantity. The paper presents changes in the combustion process thermodynamic indexes and changes in the exhaust gas emissions for dynamically increased share of the gaseous fuel. The cylinder pressure history was subject to thermodynamic analysis, . based on which the mean indicated pressure, the heat release rate, the quantity of heat released as well as the pressure rate increase after self-ignition were determined. These parameters were also referred to the subsequent engine operation cycles by specifying the scope of the change per cycle. The relationship between the engine load and the start, the center and the end of combustion while increasing the gas amount supplied to the cylinder was indicated. The presented analysis of the results indicates significant impact of the changes in the supplied gas amount on the engine operating indexes and exhaust emissions. The conducted tests made it possible to confirm that significant cooling of the cylinder (determined by the constant temperature of exhaust gas) does not allow combustion of a dual-fuel mixture during dynamic change of the engine fueling. It was shown that there is a relation between the thermal history of the cylinder (steady state conditions), the engine fueling rate and the possibility of combustion of a diesel-methane mixture.

Thermodynamic indexes of real driving conditions of gasoline and LPG fuelled engine

The aim of the conducted tests was to assess the method of delivering additional fuel dose in transient conditions and to determine the impact of this additional fuel dose on the engine operation conditions. The experimental tests were conducted in typical urban driving conditions. In the study was used system for indicating and acquisition of fast-varying data; the combustion pressure in the first cylinder of the 3-cylinder engine with spark ignition was measured, as well as the voltage on the petrol injectors and the liquefied petroleum gas injector. The post-processing analysis enabled defining engine operation indexes taking into account the aforementioned parameters. Also indicated mean effective pressure, the heat release rate and the amount of the heat released were analysed. In addition, the indexes of transient conditions of engine operation per one cycle were specified: change of the engine speed, of the maximum combustion pressure, of the indicated mean effective pressure and change of the heat release rate.