![Fig. 5. Correlation between LHV and H/C ratio. Reproduced from Narayanaswamy et al. [54], with permission from Elsevier Publishing.](/figures/fig-5-correlation-between-lhv-and-h-c-ratio-reproduced-from-3j0t50lf.webp)
![Fig. 7. Flow chart for surrogate fuel formulation from Puduppakkam et al. [110]. Reproduced with permission from SAE International.](/figures/fig-7-flow-chart-for-surrogate-fuel-formulation-from-35s3oato.webp)
![Fig. 12. Temperature measurement in a rapid compression machine using chirpedlaser absorption spectroscopy. Simulated temperature is obtained by running a zerodimensional reactive simulation. Pc D 9.21 bar, Tc D 742 K, 2.56% n-pentane/20.46% O2/75.98% N2/1%CO. Figure adopted from Nasir and Farooq [134] with permission from Elsevier Publishing.](/figures/fig-12-temperature-measurement-in-a-rapid-compression-8ki5wuhc.webp)
Q2. What is the effect of higher octane fuels on combustion efficiency?
Higher octane fuels enable earlier spark timing, which can improve combustion efficiency and power output at higher compression ratios.
Q3. What is the role of ethanol in the formation of soot in gasoline engines?
Since the addition of oxygenated species (such as ethanol) to hydrocarbons is expected to reduce soot formation, a few studies have been dedicated to carry out diffusion flameTaggedP xperiments of gasoline and ethanol blends.
Q4. How much reduction in soot agglomerates was found in the E0 flame?
the E85 flame resulted in 4 7 times reduction in nuclei mode mass and a reduction factor of about two in the size of soot agglomerates compared to the E0 flame.
Q5. Why is it possible to differentiate different fuels in the NTC and low-temperature regions?
Due to the long test times accessible with RCMs, it is possible to differentiate various fuels in the NTC and low-temperature regions.
Q6. What is the importance of a good ignition quality in HCCI engines?
Most notably, to obtain the desired onset of heat release and combustion phasing, an appropriate ignition quality is required in HCCI engines.
Q7. What is the effect of ethanol blending on gasoline?
Ethanol blending is known to cause higher volatility in gasoline-ethanol mixtures, while also introducing discontinuities in the distillation profile.
Q8. What is the importance of measuring the flame temperature as a function of the burner?
For low-pressure flames, measurement of flame temperature as a function of height above the burner is critical for the usefulness of the data.
Q9. What is the ideal homogeneous batch reactor for measuring ignition delay times?
TaggedP he shock tube stands as the ideal homogeneous batch reactor for measuring ignition delay times as a function of temperature, pressure and mixture fraction.
Q10. What is the main reason why CO emissions were not being oxidized to CO2?
CO emissions were not found to be directly linked to fuel composition, rather, in-cylinder temperature inhomogeneity (leading to cold spots) was found to be the primary reason why CO was not being oxidized to CO2.
Q11. What is the importance of a robust core mechanism in gasoline surrogate fuels?
fuel mixtures behave notably different than pure components, but the cross effects are realized in species and reactions within the intermediate radical pool (and rarely with the parent fuel molecules), which highlights the importance of a robust core mechanism.
Q12. What should be the focus of research on gasoline fuels?
Research should be directed towards acquiring liquid spray and combustion data for various gasoline fuels, surrogate mixtures, and injector geometries.
Q13. What is the way to ensure vaporization of gasoline?
The liquid fuel should be injected into a heated chamber, such as a mixing vessel, where the temperature of the vessel is high enough to ensure vaporization of all gasoline components.
Q14. What is the effect of blending oxygenates on combustion performance?
Di Iorio et al. [75] showed that blending oxygenates, such as ethanol, MTBE, and ETBE, increase the octane number, thereby improving combustion performance.
Q15. What are the difficult properties to estimate?
Physical properties, such as volatility characteristics (i.e., distillation curve), are more difficult to estimate because they are not additive.
Q16. Why are surrogate mixtures formulated to emulate the properties of the real fuel?
For this reason, surrogate mixtures are formulated to emulate the thermophysical, thermochemical, and chemical kinetic properties of the real fuel, so that fundamental experiments and predictive simulations can be conducted.
Q17. What is the important factor in the kinetic modeling effort?
This greatly facilitates the kinetic modeling effort, as it permits complex gasoline mixtures with many isoalkanes variants to be modeled as simpler mixtures of an n-alkane and a highly branched alkane.
Q18. What are the main goals of fundamental combustion experiments?
Such fundamental experiments may be able to decouple the physical and chemical aspects of fuel behavior and are ideal for understanding the effects of the chemical structure on fuel autoignition and emissions, for example.
Q19. What is the simplest explanation for the lower reactivity of cyclopentane?
Al Rashidi et al. [271,272] provided a similar explanation for the lower reactivity of cylopentane compared to n-pentane; they attribute cyclopentane's lower reactivity to higher energy barriers in forming the strained bicyclic transition state, which increase the flux to concerted elimination reactions forming unreactive cyclopentene and HO2 radicals.
Q20. What is the difference between aromatics and isoparaffins?
isoParaffins are superior to aromatics due to their higher stoichiometric fuel/ air ratio and higher H/C ratios, which improves combustion efficiency and reduces particulate matter emissions.