The Interaction Between Fuel Chemicals and HCCI Combustion Characteristics Under Heated Intake Air Conditions 2006-01-0207
To evaluate the relation between the intake air temperature (Tair-in), low temperature heat release (LTHR) and high temperature heat release (HTHR), a supercharged 4-cylinder engine with intake air heating, high compression pistons and a pressure transducer in each cylinder was introduced Eleven pure hydrocarbon components were blended into 23 different model fuels, labeled BASE MC01-MC11, and K01-K11. BASE is a mixture of equal proportion of each of the 11 pure hydrocarbons. The difference between MC series and K series fuels is in the amount of pure hydrocarbon added to the BASE: 6.5vol% for MC series fuels and 17.5vol% for K series fuels.
Engine tests were performed with BASE and MC01-MC11 fuels at Tair-in=50°C (IMEP 530kPa), 80°C (IMEP 420kPa), and 100°C (IMEP 380kPa). Because the sensitivity of heat release to fuel composition decreases at high inlet air temperature, BASE and K01-K11, that were the fuels with larger compositional difference, were tested at Tair-in=150°C (IMEP 270kPa) and 180°C (IMEP 240kPa) to further confirm the relationship. All engine tests were performed at a manifold absolute pressure of 1.55bar and engine speed of 1000rpm.
At the high Tair-in conditions only the LTHR of paraffin rich blended fuels, such as K01, K05 and K07, have distinguishable LTHR and consequent early initiation of HTHR. This means that engine performance was most influenced by the paraffin content at high Tair-in conditions. The temperature (THTHR) and pressure (PHTHR) at start of HTHR were investigated. At low Tair-in conditions, HTHR starts at a low temperature and high pressure, while at high Tair-in conditions, the HTHR starts at high temperature and low pressure. A linear relation between the THTHR and PHTHR (SU Model) was found and related to the H2O2 decomposition condition. Furthermore, as a follow-up to our previous research , the inhibitor effect of naphthenes was investigated with 6 additional model fuels.