Injection characteristics of gaseous jet injected by a single-hole nozzle direct injector Iman Erfan a , Iman Chitsaz b , Masoud Ziabasharhagh a,⇑ , Alireza Hajialimohammadi c,d , Brian Fleck e a Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran b Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran c Young and Elite Researchers Club, Parand Branch, Islamic Azad University, Parand, Tehran, Iran d Fuel and Combustion Development Department, Irankhodro Powertrain Co., Tehran, Iran e Department of Mechanical Engineering, University of Alberta, Edmonton, Canada highlights  We provide experimental work on transient jet of natural gas.  All nondimensional data of tip penetration are located between lines.  The mass flow rate of injector is independent of chamber pressure.  A port fuel injector should be utilized in a partially stratified engine. article info Article history: Received 25 September 2014 Received in revised form 19 June 2015 Accepted 13 July 2015 Available online 21 July 2015 Keywords: Direct injection Natural gas Jet structure Single-hole injector Image processing Schlieren abstract Engine manufacturers have focused on natural gas spark ignition engines due to the strict regulations for the reduction of emission levels. However, the characteristics of injectors play an important role in mix- ture formation and combustion. Two methods to identify the injection characteristics of the gaseous fuel injector which is applied in Spark Ignition Direct Injection (SIDI) engine are described. The first method studies the structure of Compressed Natural Gas (CNG) jet which is directly injected into an optical constant volume chamber for different pressure ratios. Schlieren photography is used to visualize the jet development. The correlation of tip penetration for near and far field of the jet is presented. The second experiment investigates the variations of mass flow rate due to variation of injection pressure and pressure of chamber. The results of this method indicate that mass flow rate through the injector is affected by the injection pressure linearly while it is not influenced by the pressure of chamber. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Concerns regarding air quality caused by combustion engines burning conventional fossil fuels are important current issues. Engine designers and manufacturers are required to improve these emissions. Alternative fuels, especially natural gas, are considered to be an option since there are large proven reserves and relatively low emission levels during combustion [1]. High RON [2] and hydrogen to carbon ratio [3] of CNG makes it an appropriate fuel for vehicle applications. Lower brake power of CNG compared to gasoline can be compensated by direct injection of CNG [4,5]. For direct injection NG engines, the characteristics of the NG jet, such as tip penetration and jet angle, are important to the mixing pro- cess. Hence, it is necessary to investigate the jet characteristics and fuel metering for design and optimization of CNG Spark Ignition Direct Injection (CNG-SIDI) engines. The objective of this study is to help specify the optimal position of the injector in cylin- der head and the injection timing which ensures stable combustion and lower emissions. Most works on the gas injection are limited to Diesel engines fueled with natural gas. The numerical and experimental works on the jet structure [6–10], injection system [11–13], combustion development and engine emission levels [14,15] for natural gas fueling Diesel engines were investigated in the literature. Methane jet injection in a chamber using LIF technology was investigated in Chiodi et al. [16] and Mohamad et al. [17]. They http://dx.doi.org/10.1016/j.fuel.2015.07.037 0016-2361/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Mechanical Engineering, K. N. Toosi University of Technology, P.O. Box: 19395-1999, Tehran, Iran. Tel.: +98 21 8406 3242; fax: +98 21 8867 7274. E-mail addresses: ierfan@mail.kntu.ac.ir (I. Erfan), i_chitsaz@ip-co.com (I. Chitsaz), mzia@kntu.ac.ir (M. Ziabasharhagh), a_hajiali@ip-co.com (A. Hajialimohammadi), bfleck@ualberta.ca (B. Fleck). Fuel 160 (2015) 24–34 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel