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Improvements in dual-fuel biodiesel-producer gas combustion at low loads through pilot injection splitting

Journal of Energy Engineering, ISSN: 0733-9402, Vol: 141, Issue: 2
2015
  • 23
    Citations
  • 0
    Usage
  • 15
    Captures
  • 0
    Mentions
  • 0
    Social Media
Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    23
    • Citation Indexes
      23
  • Captures
    15

Article Description

In dual-fuel engines, a combustible mixture of air and generally a gaseous fuel is ignited, thanks to the injection and autoignition of a small amount of liquid fuel. It is well-known that dual-fuel engines suffer from poor combustion when operated at low loads. This behavior, due mainly to the presence of an overlean mixture into the combustion chamber, leads to unacceptably high levels of carbon monoxide and unburned hydrocarbons emitted at the exhaust. In order to solve this problem a possible solution could be to split the pilot injection of liquid fuel into two split injections, the second having the function of boosting the combustion of gaseous fuel also during the late combustion phase. In this paper this solution has been implemented on a diesel common rail single cylinder research engine converted to operate in dual-fuel mode. The composition of the gaseous fuel, indirectly injected, simulated a typical producer gas. The liquid fuel used during the experiments was biodiesel, injected by means of a common rail injection system. The first section of results describes the tests run for comparison purposes, performing only one pilot biodiesel injection and varying its timing on a wide range. The second section of results then presents the tests run for different timings, varied on a wide range, of the first split injection, and different dwells between the first and the second injections. The engine behavior has been discussed in terms of heat release rate, fuel conversion efficiency, and nitric oxides, total hydrocarbons, and carbon monoxide emission levels at the exhaust. The results demonstrate that splitting the pilot injection leads to an increase of fuel conversion efficiency and a reduction of both total hydrocarbons and carbon monoxide. This final result allows to state that splitting the pilot injection is an effective way for sustaining the gaseous fuel combustion in dual-fuel engine late during the combustion phase.

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