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ABSTRACT
The combustion and emission characteristics of n-butanol/coal-derived naphtha blends in homogeneous charge compression ignition (HCCI) combustion mode were experimentally researched on a retrofitted diesel engine. The effects of intake temperature (Tin) and excess-air coefficient (λ) were mainly analyzed. The results show that the peak in-cylinder pressure (Pmax) and peak heat release rate (HRRmax) of all tested fuels show an overall increasing trend as Tin rises. The combustion gets faster and more stable, carbon monoxide (CO) and hydrocarbon (HC) emissions decrease, and the indicated thermal efficiency (ITE) first increases and then decreases. When Tin remains constant, the Pmax and HRRmax decrease and the combustion phase delays as the n-butanol volume fraction increases; CO and HC emissions gradually increase, except for that of lower Tin, which shows a trend of first reduction and then increase. ITE gradually decreases in general, but when Tin is higher than 100°C, coal-derived naphtha containing 24% of n-butanol in volume (B24N76) exhibits the highest ITE. In addition, for all tested fuels, both Pmax and HRRmax decrease as λ increases and the combustion gets slower and less stable; CO and HC emissions deteriorate, and ITE gradually decreases. It is worth noting that B24N76 shows the best combustion stability for all λs and exhibits the lowest CO and HC emissions when λ are 3.0 and 3.5.
Disclosure statement
No potential conflict of interest was reported by the authors.
Nomenclature
| Tin | = | Intake temperature (°C) |
| n | = | Engine speed (r/min) |
| λ | = | Excess-air coefficient |
| CD | = | Combustion duration (kJ/°CA) |
| HRRmax | = | Peak heat release rate (kJ/°CA) |
| Pmax | = | Peak in-cylinder pressure (MPa) |
| COVPmax | = | Coefficient of variation for Pmax (%) |
| ITE | = | Indicated thermal efficiency (%) |
Abbreviation
| CA | = | Crank angle |
| HC | = | Hydrocarbon |
| CO | = | Carbon monoxide |
| LTR | = | Low temperature reaction |
| LHOV | = | Latent heat of vaporization |
| HCCI | = | Homogeneous charge compression ignition |
Additional information
Funding
Notes on contributors
Ke Yang
Ke Yang is currently a PhD student majored in Vehicle New Energy and Energy Conservation Engineering, Chang’an University. Xi’an, China. His research interest includes new combustion modes and engine alternative fuels.
Chunhua Zhang
Chunhua Zhang is currently a Professor and Doctoral supervisor in the Mechanical and Electrical Engineering Department, Chang’an University. Xi’an, China. His research interest includes development and application of alternative fuels and emission control of vehicles.
An Lu
An Lu is currently a PhD student majored in Vehicle Engineering, Chang’an University. Xi’an, China. His research interest includes new combustion mode and reaction mechanism of emission generation.
Yujia Kang
Yujia Kang is currently a student majored in Vehicle Operation Engineering, Chang’an University. Xi’an, China. His research interest includes battery thermal management and simulation.
Xiaowen Yu
Xiaowen Yu is currently a student majored in Vehicle Operation Engineering, Chang’an University. Xi’an, China. Her research interest includes coal-derived lubricating oil for vehicles.
Hanwen Wang
Hanwen Wang is currently a student majored in Vehicle Engineering, Chang’an University. Xi’an, China. His research interest includes coal-derived lubricating oil for vehicles.