Direct Fuel Injection Research Articles

Computational Prediction of NOx Reduction Characteristics of Premixed Lean Diesel Engine.

Three-dimensional computations were carried out to study the effects of engine operating conditions on NOx emissions from premixed lean diesel combustion in a DI (Direct fuel Injection) engine. A modified version of the KIVA II computer code was used for numerical simulations. Qualitatively good agreement between computational and experimental results of the spatial distribution of impinging fuel sprays, the heat release rate, and the relative NOx mass have been achieved. The computational results demonstrate that NOx emissions are significantly influenced by intake air temperature, fuel injection timing, and fuel ignitability. It was also shown that fuel droplets which enter the squish region can later contribute to unburned fuel emissions.

Mixture Formation and Ignition in a Direct Injection Natural Gas Engine.

A natural gas fueled direct injection test engine, equipped with a newly developed natural gas injector, was designed and the influences of injection timing and spark timing on indicated mean effective pressure and exhaust emissions were investigated. The following results were obtained:(1)The location of the spark plug relative to the injection nozzle location and the piston cavity wall needs to be optimized to achieve a wide range of stable ignition and engine operating conditions;(2)Impingement of the gas jet against the cavity wall and high injection pressure are two key factors required to control ignition and combustion of the gas jet;(3)In terms of mixture preparation around the spark plug, early injection is preferable at low load conditions, and late injection at high load conditions;(4)When excess air ratio λ is 1.06 and 1.4, THC concentration was about 1 000 ppm and NOx concentration exceeds 1 000 ppm. When λ values are 2 and 2.3, THC concentration was high but NOx concentration was below 100 ppm.

A Study of Direct Fuel-Injection Two-Stroke Cycle Methanol Engine.

A direct fuel-injection two-stroke cycle engine operated with neat methanol was investigated. The engine performances, combustion and exhaust gas characteristics were analyzed experimentally and were also compared with the results of operations with a carburetor, EFI injection at the intake manifold, and EFI injection at the scavenging port. As a result, the power and the brake thermal efficiency of the direct fuel-injection engine were higher than those of engines operated with a carburetor and the above two EFI methods. The exhausted unburned fuel of the direct fuel-injection engine was lower than that with operation with a carburetor, and holmaldehyde and CO concentration were of the same level as the operations with the carburetor and EFI methods. The NOx concentration of the direct fuel-injection was half the level of the result of carburetor operation. Because a stratified charge using direct fuel-injection activated the combustion of the lean mixture which increases working gas temperature, therefore, the vaporization of injected fuel was promoted by the elevated temperature of the residual gas.

Modeling of the Combustion Process in a Dual Fuel Direct Injection Engine

Analytical methods to provide a guideline for predicting the limit for acceptable power output of dual fuel engines due to the onset of autoignition and knock are described. This is achieved primarily through improved modeling of the chemical reaction rates of the charge during compression and subsequently following pilot ignition. Some performance results with methane as a fuel are presented.