Detailed chemical kinetic simulations of homogeneous charge compression ignition engine transients

Abstract

A fast, full-cycle homogeneous charge compression ignition (HCCI) simulator that uses detailed fuel chemistry for the primary reference fuel PRF90 (1036 species and 4238 reactions) is presented and used to study transient engine performance. The numerical predictions are compared with measured data from a single-cylinder HCCI engine that uses residual gas trapping. In particular, the response of the engine to changes in fuelling rate, speed, and phasing of the exhaust valve event is studied. The experimental results are obtained using a Mazda port fuel injected 2.3 l four-cylinder engine that is modified to run in a single-cylinder mode and to allow HCCI operation. The simulator combines a standard cycle simulation software package for the gas exchange processes with a two-zone model of the trapped charge; the combustion in the cylinder is modelled using a detailed chemical kinetics mechanism. To minimize the demand for computational resources, a specialized numerical solver is used that exploits sparsity of the system and allows the simulator to run in 7–8 min per cycle on a desktop computer. The numerical and experimental results are compared. The model predictions for the transient time constants and the changes in gross indicated mean effective pressure (GIMEP) during/after a step change in equivalence ratio, φ, and speed are consistent with experimental data and are accurate enough to be useful for HCCI engine design. The model predictions for the changes in CA50 (the crank angle at which 50 per cent of the cumulative heat release occurs) during transients are less reliable. Ways by which the fidelity of the HCCI transient model predictions could be improved are outlined.

Các khó khăn của công nghệ HCCI trên động cơ đốt trong

“…Quá trình này xảy ra đồng thời và tự phát tại một số điểm. Kiểm soát chính xác thời điểm cháy là một thách thức lớn và liên quan đến một loạt các điều kiện vận hành của động cơ [5]. Động cơ HCCI không thể kiểm soát trực tiếp quá trình cháy, vì vậy điều khiển quá trình cháy trong động cơ HCCI là khó khăn đầu tiên khi nghiên cứu về công nghệ này.…”

Simplifying ignition delay prediction for homogeneous charge compression ignition engine design and control

“…However, fundamental combustion research studies explore this method in order to better understand the various interactions involved. 1,16 With regard to simplifying the prediction of ignition delay times using ignition correlation, some work based on chemical kinetic models has been presented in the literature. 17,18 For correlations based on experimental ignition data, most focus on empirical Arrhenius-type expressions There has also been sustained effort by some researchers to develop highly reduced chemical kinetic models based on the analysis of detailed and skeletal chemical kinetic models.…”

“…However, fundamental combustion research studies explore this method in order to better understand the various interactions involved. 1,16…”

Transient flow characteristics of a high speed rotary valve

“…In an effort to better understand the HCCI process, the specifics of fuel heat release under varying conditions of engine operation must be quantified. Highly detailed numerical analysis can be performed using chemical kinetics modeling such as CHEMKIN [15,13,20] (sometimes coupled with KIVA [17]), direct numeric simulation (DNS) [13], and the hydrodynamics, chemistry, and transport (HCT) model [18].…”

“…Heat transfer models within the cylinder are critical to numerically estimating conditions pertinent to autoignition. Several correlations exist, such as the many variations of Woschni's equation [2,20,13], for example,…”