Effects of direct water injection and injector configurations on performance and emission characteristics of a gasoline direct injection engine: A computational fluid dynamics analysis

Abstract

In-cylinder water injection is a promising approach for reducing NOx and soot emissions from internal combustion engines. It allows one to use a higher compression ratio by reducing engine knock; hence, higher fuel economy and power output can be achieved. However, water injection can also affect engine combustion and emission characteristics if water injection and injector parameters are not properly set. Majority of the previous studies on the water injection are done through experiments. Therefore, subtle aspects of water injection such as in-cylinder interaction of water sprays, spatial distribution of water vapor, and effect on flame propagation are not clearly understood and rarely reported in literature due to experimental limitations. Thus, in the present article, a computational fluid dynamics investigation is carried out to analyze the effects of direct water injection under various injector configurations on water evaporation, combustion, performance, and emission characteristics of a gasoline direct injection engine. The emphasis is given to analyze in-cylinder water spray interactions, flame propagation, water spray droplet size distribution, and water vapor spatial distribution inside the engine cylinder. For the study, the water-to-fuel ratio is varied from 0 to 1. Various water injector configurations using nozzle hole diameters of 0.14, 0.179, and 0.205 mm, along with nozzle holes of 4, 5, 6, and 7, are considered for comparison in addition to the case of no_water. Computational fluid dynamics models used in this study are validated with the available data in literature. From the results, it is found that the emission and performance characteristics of the engine are highly dependent on water evaporation characteristics. Also, the water-to-fuel ratio of 0.6 with 6 number of nozzle holes and the nozzle diameter of 0.14 mm results in the highest indicated mean effective pressure and the lowest NOx, soot, and CO emissions compared to other cases considered.

Development of an experimental test bench and a psychrometric model for assessing condensation on a low-pressure exhaust gas recirculation cooler

“…Then, equation (5) provides the partial saturation pressure correlation (Antoine equation) of saturated water vapor, which only depends on the temperature of the gas. So, the relation of the relative humidity (RH; equation (6)) between both gases is connected through a proportional constant as can be seen in equation (12). The error of using this consideration has been assessed using the developed condensation model, resulting in a deviation between 1% and 4% in terms of accumulated water at the end of the warm-up tests for the selected test matrix, which is in the order of magnitude of the measurement uncertainties RH air = 0:9543 Á RH Exh ð12Þ…”

“…using exhaust gas recirculation (EGR) 11 or injecting water into the cylinders. 12,13 This work is focused on using EGR as an emission-reduction technique. 14 This technique consists of recirculating a portion of the exhaust gases back to the engine cylinders mixed with fresh air, which dilutes the concentration of O 2 and provides inert gases to the combustion process.…”

Spray development of iso-octane, ethanol, hydrous ethanol and water from a multi-hole injector under ultra cold fuel temperature conditions

“…Distilled water was also tested at ambient conditions for comparison. It is noted that apart from its relevance as a hydrous ethanol component, there has been great interest recently in the atomisation of water by direct injection for increasing the thermal efficiency of engines [47][48][49][50][51]. Some typical properties of the three fuels and water related to atomisation are summarised in Table 1 at atmospheric temperature and pressure for easy reference.…”

Analisis Sistem Injeksi Air/Metanol Dan Air/Etanol Terhadap Konsumsi Bahan Bakar dan Emisi Gas buang

“…Indicated Specific Fuel Consumption memiliki tren kebalikan dari Idicated Mean Fuel Consumption yaitu menurun, dan kemudian mencapai titik minimum pada rasio W/F 0,6 dan kemudian meningkat dengan peningkatan rasio W/F. ISFC pada rasio W/F 0,6 adalah sekitar 243 g/kW jam, yang sekitar 8,2% lebih rendah daripada tanpa injeksi air [7].…”

“…Karakteristik emisi dan performa mesin sangat tergantung pada karakteristik penguapan air dan rasio air terhadap bahan bakar yaitu 0,6 dengan jumlah lubang nosel 6 dan diameter nosel 0,14 mm menghasilkan tekanan efektif rata-rata tertinggi dan emisi NOx, jelaga, dan CO terendah dibandingkan dengan kasus tanpan injeksi air [7].…”