In-cylinder studies of hybrid combustion in a direct injection single-cylinder optical engine

Abstract

Over the last decade, controlled autoignition (CAI) combustion, or homogeneous charge compression ignition (HCCI), has been the subject of numerous studies and has shown its potential to reduce fuel consumption and NO x emissions simultaneously from gasoline engines. However, there are still some fundamental questions that are yet to be addressed, such as combustion control and underlying physical and chemical processes. In the present study, a single-cylinder optical gasoline engine was operated with negative valve overlap to investigate CAI and hybrid spark ignition (SI)–CAI combustion. The effects of direct fuel injection and spark timings were studied by means of a simultaneous in-cylinder heat release study and high-speed visualization of total chemiluminescence, OH and CHO radicals.

Control and optimization of spark ignition–controlled auto-ignition hybrid combustion based on stratified flame ignition

“…Chang et al 15 proved that the fuel injection during negative valve overlap (NVO) was an effective way to extend the dilution limit of gasoline hybrid combustion. The work carried out by Polovina et al 16 and Yang and Zhao 17 also showed the effectiveness of NVO injection strategy.…”

Spectroscopic analysis of the phases of premixed combustion in a compression ignition engine fuelled with diesel and ethanol

“…Moreover, the same spectra show also well resolvable peaks at 431 nm due to CH radical and a broadband emission from 250 to 440 nm due to both HCO and HCHO [18,21,30]. CH is indicating the rich combustion of the mixture [21,26]. On the other hand, in the center under the nozzle tip, the spectra intensity continue to grow.…”

“…In particular, a filter at 310 nm was used; it had a bandwidth of 10+/À2 nm and a peak transmission of 15% of the incident light. Its intensity along the combustion process was related to the rate of heat release curve [24,26].…”

Assessment of elliptic flame front propagation characteristics of iso-octane, gasoline, M85 and E85 in an optical engine

“…Therefore, optical investigation of combustion is preferred to pressure tracing at the early combustion stages. The practical realisation of visual access to a combustion chamber of a working piston engine is not easy, with any of the visible, ultra violet spectra or laser radiation approaches [43][44][45][46]. The fluctuating pressure at high temperature, the limited strength of transparent materials and the geometrical constrains kept investigators from studying optical engines at real working conditions.…”