| Abstract: | In this paper, a multi-zone model is developed to predict the operating range of homogeneous charge compression ignition (HCCI)
engines. The boundaries of the operating range were determined by knock (presented by ringing intensity), partial burn (presented
by combustion efficiency), and cycle-to-cycle variations (presented by the sensitivity of indicated mean effective pressure
to initial temperature). By simulating an HCCI engine fueled with iso-octane, the knock and cycle-to-cycle variations predicted
by the model showed satisfactory agreement with measurements made under different initial temperatures and equivalence ratios;
the operating range was also well reproduced by the model. Furthermore, the model was applied to predict the operating range
of the HCCI engine under different engine speeds by varying the intake temperatures and equivalence ratios. The potential
to extend the operating range of the HCCI engine through two strategies, i.e., variable compression ratio and intake pressure
boosting, was then investigated. Results indicate that the ignition point can be efficiently controlled by varying the compression
ratio. A low load range can be extended by increasing the intake temperature while reducing the compression ratio. Higher
intake temperatures and lower compression ratios can also extend the high load range. Boosting intake pressure is helpful
in controlling the combustion of the HCCI engine, resulting in an extended high load range. |
