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It is established that spark ignition (SI) engines are a contributor to polycyclic aromatic hydrocarbons (PAH) in the atmosphere. Studies have shown that the PAH emissions from SI engines are dependent on fuel chemistry. In addition, a few previous studies have shown that the PAH emissions are also dependent on operating conditions. Those studies however, did not involve a wide range of operating conditions such as spark timing, engine speed and compression ratio. This paper presents experimental results of PAH emissions from a single cylinder SI engine (Ricardo E6 engine) at various operating conditions employing contemporary PAH sampling and analysis techniques. Results show that PAH emissions increase with increasing equivalence ratio, spark advance, increase in engine load and with increase in compression ratio. With the engine speed, however, the PAH emissions show a sharp decrease and then a slight increase in the emissions as the speed is increased.

Fuel adulteration is becoming a widespread problem in South Asian countries, some forms of which are responsible for deterioration in performance and increase in emissions of spark ignition (SI) engines. A common form of adulteration is to blend gasoline with kerosene which is prevalent because of financial benefit resulting from the price difference between the two fuels. In addition to rendering the fuel more knock prone, based on previous studies it can be surmised that gasoline adulteration with kerosene would increase hydrocarbon (HC), particulate matter (PM) and polycyclic aromatic hydrocarbon (PAH) emissions from SI engines. However, detailed information about the emission effects with the extent of adulterant in the fuel is lacking. This paper elaborates on the effects of kerosene adulteration starting from change in the properties of the gasoline, including volatility and enthalpy of vaporization, to combustion characteristics of gasoline-kerosene blends in an SI engine.

Gasoline blended with kerosene, which is considered to be ‘adulterated’ fuel in South Asian countries, has been shown to increase knocking tendency in spark-ignition engines. The current study involves the use of known gasoline-kerosene blends to fuel a single cylinder Ricardo E6 engine and characterize the knocking of such blends. This paper presents results and discusses the variation of knock limited spark timing with change in kerosene proportion in the blend and with air-fuel ratio. Knock characterization is quantitatively evaluated by applying Fast Fourier Transform (FFT) and bandpass filtering techniques to the cylinder pressure data. Knock intensity of the gasoline-kerosene blends with varying proportion of kerosene is compared. An increasing amount of kerosene in the blends has been shown to increase both the knocking tendency as well as the intensity of knock.