The Effects of Exhaust Gas Recirculation on the Performance and Combustion Characteristics of Methanol-Fueled Spark Ignition Engines

To examine the effects of exhaust gas recirculation (EGR) on the exhaust emissions and on the cycle-by-cycle variation of combustion process in a methanol engine, the authors have tried to measure the emissions of total hydrocarbon, carbon monoxides, nitric oxides and formaldehyde and to record the cylinder pressure development histories of 1000 cycles duration. Moreover, the standard deviation of peak pressure Pmax, the heat release rate and the averaged pressure history are analyzed.

The results are compared with those of gasoline fueled operation.

The results are summarized as follows:

1. (1)
   In the case of a methanol-fueled engine operated under exhaust gas recirculation (EGR), similar to that already carried out in a gasoline-fueled engine, the concentration of NOx, in the exhaust gas can be decreased but those of formaldehyde (HCHO) and unburned methanol are increased.
2. (2)
   The effect of EGR, such as 20% of it, on Nox reduction is the same as those of hydrous methanol of 50% water content.
3. (3)
   In the case of EGR applied to an EFI engine, its output and thermal efficiency are decreased within the lean mixture region (λ>1.0) but these recover and the concentration of hydrocarbon is decreased by raising the fuel temperature.
4. (4)
   When the optimum conditions of the EGR and fuel temperature are selected, it is possible to improve the exhaust gas characteristics concerning NOx, THC, etc., while the decreased in engine output and thermal efficiency is reduced to the minimum.