Hole-to-hole variations in coupled flow and spray simulation of a double-layer multi-holes diesel nozzle

Abstract

In diesel engines, double-layer multi-holes nozzles contribute significantly in making spray injection uniform in both the circumferential and axial directions; they further ensure that minimal or no interactions are encountered among the spray jets emerging from the nozzle holes and positively affect fuel atomisation and enhance mixing during engine operation. In this study, the variation in internal flow characteristics and spray patterns from the upper and the lower layer nozzle holes were investigated experimentally and computationally. A double-layer 8-hole heavy-duty diesel engine injector nozzle was utilised for the characterisation of hole-to-hole variation on spray formation. The actual nozzle geometry was derived from X-ray scans obtained at the third generation X-ray imaging and biomedical beamline station in SSRF, revealing all geometrical differences between the individual injection holes. The momentum fluxes from each holes were obtained together with spray tip penetration under non-evaporating conditions. These data were used to validate the computational fluid dynamics (CFD) model suitable to describe the relevant flow processes. Initially, an Eulerian-Eulerian two-phase flow model was utilised to predict the internal nozzle flow under cavitating conditions. This model was weakly coupled with a Lagrangian spray model predicted the subsequent atomisation and penetration of all individual spray plumes. The results show that cavitation development within the upper layer holes is more intense than those formed within the lower layer nozzle holes; this is leading to higher injection rates from the lower layer nozzle holes that they also exhibit less cycle-to-cycle variations in the observed spray patterns.

Numerical simulation and experimental validation of cavitating flow in a multi-hole diesel fuel injector

“…The comparison of prediction results showed good agreements with the experimental results for mean velocity but underpredicted the RMS velocity where cell size was not very fine. The variation in internal flow characteristics and spray patterns in diesel engine from the upper and the lower layer nozzle holes have been investigated recently by Wang et al 23 experimentally (using X-ray scans) and computationally (using Eulerian-Eulerian two-phase flow and Lagrangian spray models); the results showed that the cavitation development within the upper layer holes is more intense than those formed within the lower layer nozzle holes leading to higher injection rates from the lower layer nozzle holes and that they also exhibit less cycle-to-cycle variations in the observed spray patterns. Also, Mohan et al 24 simulated in-nozzle flow and spray (flashing and non-flashing) in IC engine using a coupled Eulerian-Lagrangian approach and Lagrangian spray models, and the results showed good quantitative agreements between the liquid and vapor penetration lengths with the published experimental data.…”

Численное Моделирование Образования Температурного Факела Неизотермических Жидких Впрысков

“…The temperature in the combustion chamber varied from 700 K to 1500 K. The pressure in the combustion chamber was 100 bar for octane and 80 bar for dodecane and the injection velocity was 350 m/s in both cases. These values were taken from previous works of the authors [19][20][21][22][23]. distribution of liquid fuel droplets (octane and dodecane), respectively.…”

Investigation of cavitation phenomenon with different fuel temperatures in diesel nozzles

“…Fuel economy and emission cleanliness have gradually become the primary factors to be considered in diesel engine with proposing the concept of “energy saving” and “environmental protection.” 1,2 The electronic high-pressure common rail fuel injection system is equivalent to the “heart” and “brain” of the internal combustion engine, and is regarded as a landmark technology to improve fuel economy and reduce pollutant emissions. 3,4 Injector nozzle is the most critical core component in high-pressure common-rail fuel injection system, 5–7 which is related to the accuracy and stability of fuel injection system. Cavitation phenomenon performs the most common two-phase flow in the nozzle with high turbulence and strong compression.…”