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In this work, the effects of engine operational parameters, λ, spark timing, and compression ratio, on knock tendency and intensity as well as H2 supplementation are studied. We postulated, verified and eventually used the duration from ignition to 70% mass fraction burnt (MFB0-70%) as an explanatory variable to describe the knock tendency and intensity. In this manner, the physical factors and fuel factors that are introduced by the differences in test conditions can be differentiated. Practically, in terms of percentage of knocking cycles or the spark timing at audible knock, knock tendency decreases as λ increases and increases with H2 supplementation. However, when MFB duration is taken into account, then for the same MFB duration, knock tendency increases as λ increases and decreases with H2 supplementation.

Global ethanol trade is forecast to increase 25-fold by 2020. Most of it will be blended with gasoline to make biofuel. However, blending ethanol with gasoline has a profound effect on the evaporation characteristics of the mixture. In particular, the thermodynamic properties of the blends can be significantly different than the constituents. A clear understanding of the blend's properties is essential for optimizing engine design, e.g. utilizing charge cooling effect. Data available in the literature is very limited, considering ethanol-gasoline blends will be used as a fuel in large scale worldwide. In this work, comprehensive measurements of vapor pressures were carried out. The enthalpies of vaporization were derived from vapor pressure data using the Clausius-Clapeyron equation. Maximum vapor pressure occurs with 20% ethanol-gasoline blend at which a positive azeotrope is formed. The trend is different in enthalpy of vaporization.

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.

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.

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.

Exhaust gas temperatures in a 1.4 L, sparked ignition engine have been measured using fine wire thermocouples at different loads and speeds. However the thermocouples are not fast enough to resolve the rapid change in exhaust temperature. This paper discusses a new thermocouple compensation technique to resolve the cycle-by-cycle variations in exhaust temperature by segmentation. Simulation results show that the technique can find the lower time constants during blowdown, reducing the bias from 28 to 4%. Several estimators and model structures have been compared. The best one is the difference equation-least squares technique, which has the combined error between -4.4 to 7.6% at 60 dB signal-to-noise ratio. The compensated temperatures have been compared against combustion parameters on a cycle-by-cycle basis. The results show that the cycle-by-cycle variations of the exhaust temperatures and combustion are correlated.