Combustion in Gas Fueled Compression: Ignition Engines of the Dual Fuel Type

Abstract

In the dual fuel engine much of the energy release comes from the combustion of the gaseous fuel while only a small amount of diesel liquid fuel provides ignition through timed cylinder injection. Such operation with optimum conversion methods has the potential to provide operational characteristics that are comparable or superior to those of the corresponding diesel or spark ignition engines. These characteristics may be realized only if sufficiently effective measures can be ensured both for the avoidance of knock, usually at high loads, and incomplete gaseous fuel utilization at relatively light loads. An objective of this contribution is to demonstrate that the main effort needed to overcome the problems associated with the operation of gas fueled dual fuel engines is via a better control of the relatively complex processes of combustion. Both experimental and analytical modeling procedures for effecting optimum improvement to the combustion process are described.

Combustion and emissions characteristics of a dual fuel engine operated on alternative gaseous fuels

“…A similar observation was reported by Karim in [13]. This was due to the increase in the concentration of gaseous fuel in air and the corresponding overall equivalence ratio which modifies and extends significantly the flammability zone around the pilot fuel [32].…”

“…This can be attributed to several interacting effects including: reduced oxygen partial pressure due to air displacement by gaseous fuel; reduced temperature and pressure during the initiation of the ignition as methane has a higher heat capacity than air; pre-ignition reaction activities between methane and air may affect those between diesel and air; increased residuals concentration at higher loads [36]. Longer ignition delay periods for dual fueling with NG or methane are also reported by several authors including [13,17,31,37]. The ignition delay was affected further due to the presence of CO 2 in gas as CO 2 has a high specific heat capacity.…”

“…Numerous research works on experimental and theoretical investigations concerning the dual fuel diesel-natural gas operating mode have been reported over the last decades in the literature [12][13][14][15][16][17][18].…”

Fumigation of a heavy duty common rail marine diesel engine with ethanol–water mixtures

“…In diesel engines, NOx emissions primarily form in the region surrounding the combustion zone. Karim [11] notes that the production of NOx depends on the peak value of the combustion temperature, the effective volume of the combustion zone, the availability of oxygen and the time available for the rate limited NOx reactions. It is possible that the presence of combustible gas in the air leads to the combustion occurring at a slightly more fuel rich mixture strength which would make less oxygen available for thermal NOx formation.…”

“…Karim [11] postulated that there are three distinct stages in dual fuel combustion, where the primary fuel is gaseous and ignition is by pilot injection of standard diesel fuel. The first stage involves combustion of some of the pilot fuel and some gaseous fuel entrained into the fuel spray.…”