Combustion features under different center of heat release of a diesel engine using dimethyl carbonate/diesel blend

ABSTRACT

Experiments were performed in a single cylinder common-rail diesel engine that adopts a low temperature premixed charge compression ignition (PCCI) mode. Combustion features of dimethyl carbonate (DMC)-diesel blends under various centers of heat release (COHRs) were revealed in details. With retarding of COHR, all the peaks of pressure and pressure rise rate and bulk gas temperature are postponed and declined in sequence. Normally, the crank angle of peak pressure is quite close to the COHR, while the peak of bulk gas temperature appears about 7°CA after COHR as a rule. The prolongation can be demonstrated at every stage of combustion such as q₁₀ and q₉₀ with the COHR being put backward. In addition, the heat release of diesel is completely slower than that of D10 fuel at various stages. Unfortunately, retarding of COHR implies a declining thermal efficiency of engines as well as a higher cyclic variation in general. Nevertheless, D10 blend has higher thermal efficiency than diesel thanks to high oxygen content of DMC and low boiling point that prompts better fuel atomization and complete combustion. Meanwhile, the cyclical variation of D10 is greater than diesel fuel owing to the low heat value, high latent heat of vaporization, and poor flammability of DMC. As a total, a comprehensive understanding of PCCI combustion features under different COHRs can be conducive to conducting effective management of combustion process and manipulating the subsequent emission performance to a favorable level.

KEYWORDS:

• Center of heat release (COHR)
• combustion process
• diesel engine
• dimethyl carbonate
• multiple injection
• premixed charge compression ignition (PCCI)

Funding

The authors wish to express their appreciation for the funds from the National Natural Science Foundation of China (No. 51376095 and No. 51506101) and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), which supported this study.

Nomenclature

CA	=	crank angle
COHR	=	center of heat release
COV	=	coefficient of variation
DMC	=	dimethyl carbonate
DME	=	dimethyl ether
D10	=	a fuel blend of 10% DMC in diesel
EGR	=	exhaust gas recirculation
HCCI	=	homogenous charge compression ignition
HRR	=	heat release rate
ηi	=	indicated thermal efficiency
PCCI	=	premixed charge compression ignition
pmax	=	peak pressure (MPa)
pmi	=	indicated mean effective pressure (MPa)
q10	=	10% of total heat release
q90	=	90% of total heat release
TDC	=	top dead center

Additional information

Funding

The authors wish to express their appreciation for the funds from the National Natural Science Foundation of China (No. 51376095 and No. 51506101) and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), which supported this study.