The effect of nozzle geometry over internal flow and spray formation for three different fuels

Abstract

h i g h l i g h t sTwo single hole nozzle (cylindrical and convergent) are used. A complete hydraulic characterization is done along with spray visualization. A fast pulsed light source is synchronized to a fast camera working at 160 kHz. The effect of nozzle geometry is analyzed for three different fuels. A large set of experimental data was obtained, which could be used for model validation. a b s t r a c tThe influence of internal nozzle flow characteristics over macroscopic spray development is studied experimentally for two different nozzle geometries and three fuels. The measurements include a complete hydraulic characterization consisting of instantaneous injection rate and spray momentum flux measurements, followed by a high-speed visualization of isothermal liquid spray in combination with cylindrical and conical nozzle configurations. Two of the fuels are pure components-n-heptane and ndodecane-while the third fuel consists of a three-component surrogate to better represent the physical and chemical properties of diesel fuel. The cylindrical nozzle with 8.6% larger diameter, in spite of higher mass flow rate and momentum flux, shows slower spray tip penetration when compared to the conical nozzle. The spreading angle is found to be inversely proportional to the spray tip penetration. The spreading angle is largely influenced by the nozzle geometry and the ambient density. Rail pressure was found to have weak influence on the near-field spreading angle and no influence on the standard deviation of the spreading angle. n-Heptane spray shows slowest penetration rates while n-dodecane and the surrogate fuel mixture show very similar spray behavior for variations in injection pressure and back pressure. However, the surrogate fuel mixture shows higher penetration than n-dodecane when using the conical nozzle and lower penetration than n-dodecane when using cylindrical nozzle.

A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles.

“…Research has also focused on elucidating the relationship between nozzle shape and cavitation, whose presence can significantly perturb fuel spray characteristics such as the discharge coefficient, outlet velocity, spray angle, and atomization behavior [3]. A converging diameter profile and a sufficiently rounded hole inlet corner were found to decrease or eliminate geometric cavitation in comparison to a sharp-cornered, cylindrical geometry [4,5]. In addition, local asymmetries at the hole inlet have been shown to generate correspondingly asymmetric cavitation, forming at the location where the fuel flow experiences the largest change in direction [5].…”

Dispersion of spray droplets near diesel fuel injector nozzle

“…ディーゼル機関において熱効率の向上や排気物質の低減のため，燃料噴霧特性の詳細な理解に基づく燃焼の適 切な制御が求められている．燃料噴霧の基礎的な情報として，噴霧先端到達距離や噴霧角等の噴霧形状について は多くの研究成果が報告されている．燃料噴霧は時間的な非定常性が強く，空間的にも不均一であることから， 噴霧内部における噴霧液滴を評価する必要がある．噴霧下流の燃料噴霧については，噴霧液滴が十分に拡散し， 比較的計測が容易であることから，PDPA (Wang et al, 2016a)や PIV (Zama et al, 2012)により計測された液滴の速度 分布や粒径分布が報告されている．噴孔近傍の噴霧については液滴が非常に密集しているため比較的計測が容易 ではないものの，Crua らは長距離顕微鏡を用いて噴孔近傍の噴霧外縁部の噴霧液滴の速度および粒径分布を計測 している (Crua et al, 2015)．また Moon らは X 線位相コントラスト法 (XPCI: X-ray Phase Contrast Imaging) を用い *1 正員，長崎大学 工学研究科（〒852-8521 長崎県長崎市文教町 1-14） *2 いすゞ自動車（株） （〒252-0881 神奈川県藤沢市土棚 8） *3 （株）いすゞ中央研究所 E-mail of corresponding author: komada@nagasaki-u.ac.jp ることで，噴孔近傍噴霧のラインオブサイト特性に基づく画像を取得しており，その画像を解析することで噴霧 の速度分布や粒径分布を計測している (Moon et al, 2014)．燃料噴霧は下流に向かって広がり拡散することから噴 霧の分散過程が重要であり，噴霧角から分散を評価した結果が報告されている (Payri et al, 2016) (Naber and Siebers, 1996)．また，Wang らは微小な時間に噴射された燃料の質量と噴霧画像における噴霧断面積の増加量の間のつり あいから噴霧質量の分散を評価している (Wang et al, 2016b Fig. 1 Fuel spray measurement system.…”

The effect of nozzle geometry over ignition delay and flame lift-off of reacting direct-injection sprays for three different fuels

“…Therefore, richer surrogates containing aromatics and other species that are important components in diesel fuels must also be represented in the surrogate selected for this study. In the present paper, three surrogate fuels are employed, n-heptane as the classical diesel substitute, ndodecane that has been widely accepted as a diesel substitute in recent years and it was decided as reference fuel for the ECN [20,29] and finally a multi-component diesel surrogate consisting of n-tetradecane (0.5), n-decane (0.25) and a-methylnaphthalene (0.25) is utilized [30,31]. Numbers in parentheses represent mass fractions.…”

“…The study follows up on three previous works which analyze the effect of nozzle geometry over the liquid iso-thermal non-evaporative spray formation [32], the effect of nozzle geometry combined with different fuels on the hydraulic performance and liquid isothermal non-evaporative spray formation [30], and the same nozzles and fuels on evaporative conditions [31]. In this work, all experiments were also performed for the same nozzle geometries (cylindrical and conical convergent) and fuel types.…”