Journal Articles

Effects of fuel injection pressure and quantity on low octane gasoline sprays in a simulated high-pressure ambient environment of a gasoline compression ignition engine

Authors: Sam Joe Chintagunti, Avinash Kumar Agarwal*

Reference: Joe Chintagunti, S., & Kumar Agarwal, A. (2024). Effects of fuel injection pressure and quantity on low octane gasoline sprays in a simulated high-pressure ambient environment of a gasoline compression ignition engine. Fuel, 363, 130793. https://doi.org/10.1016/j.fuel.2023.130793

Link to Download: https://drive.google.com/file/d/1niatIkFlPSFb0K1lOPfwwk7z_qhNI4Fp/view?usp=sharing

Abstract: Gasoline Compression Ignition technology using low-octane gasoline-like fuel can lead to very low NOx and Soot emissions and enhanced thermal efficiency than conventional diesel engines. The difference in test fuel properties is a significant reason for the difference in the fuel-air mixture formation in Gasoline Compression Ignition engines offering these advantages. In this study, microscopic and macroscopic spray characterization of baseline diesel, 50% v/v diesel blended with 50% v/v gasoline (G50), and 20% v/v diesel blended with 80% v/v gasoline (G80) are conducted in a high-pressure ambient environment relevant to Gasoline Compression Ignition engines. The study was performed in a Constant Volume Spray Chamber in non-reacting conditions using Phase Doppler Interferometry and Diffused Backlit Illumination techniques. The test fuels were injected into a 30-bar ambient pressure environment at 400, 500, and 700-bar fuel injection pressures. The liquid spray penetration length of gasoline-diesel blends was slightly shorter than baseline diesel, but their spray cone angles and entrained air mass were significantly higher. The average axial droplet velocity was higher, and the Sauter Mean Diameter was lower for gasoline-diesel blends than baseline diesel 40 mm away from the injector nozzle exit, indicating superior mixture formation for the gasoline-diesel blends. The effect of droplet collision and injected fuel quantity on droplet size distribution was assessed in all test fuels. Droplet collisions increased the Sauter Mean Diameter of the spray at farther distances. Smaller fuel injection quantities decreased the Sauter Mean Diameter of the spray, increasing the probability of unburnt hydrocarbon emission-producing ultra-lean regions in the engine combustion chamber.

Book Chapters

Spray Chamber Designs and Optical Techniques for Fundamental Spray Investigations

Authors: Sam Joe Chintagunti, Ankur Kalwar, Dhananjay Kumar, and Avinash Kumar Agarwal 

Reference: Chintagunti, S. J., Kalwar, A., Kumar, D., & Agarwal, A. K. (2021). Spray Chamber Designs and Optical Techniques for Fundamental Spray Investigations. In Novel Internal Combustion Engine Technologies for Performance Improvement and Emission Reduction (pp. 105-144). Springer, Singapore. 

Link to download: https://drive.google.com/file/d/15_S_JpBYW4P9Eiio1czj2uFFj0TufQog/view?usp=sharing

Abstract: In the present scenario, research in the area of Internal Combustion (IC) engines is mainly driven to address the alarming depletion of conventional fossil fuels and to control the tail-pipe emissions in order to comply with stringent emission norms. Combustion is one of the primary reasons for global warming; however, ~80% of total global energy production is based on combustion of conventional fuels. Hence, researchers have been trying to understand the in-cylinder combustion phenomenon to improve efficiency of energy conversion devices and new ways to utilize alternate fuels. Spray studies in engine-like environment play vital role in combustion and consequent heat loss to the cylinder walls. Fuel spray affects the air–fuel mixture formation, which is responsible for combustion and emission formation in the engine combustion chamber. To study mixing processes and spray distribution, in-cylinder conditions need to be simulated in constant volume combustion chamber (CVCC). Development of high-pressure high-temperature chambers and optical diagnostics involves lasers and high-speed cameras. These investigations enable us to understanding the insights into combustion that takes place in few milliseconds. This chapter starts with design of combustion chambers, followed by explanation of prominent optical techniques. This is followed by detailed discussions with the help of recent studies involving these chambers and techniques to understand spray atomization and combustion in different operating conditions. This chapter aims to give an understanding of different aspects of experimental spray studies and their impact in the field of IC engines. 

-----------------------------------------------------------------------------

Combustion in Diesel Fuelled Partially Premixed Compression Ignition Engines

Authors: Sam Joe Chintagunti, Avinash Kumar Agarwal*

Reference: Chintagunti, S.J., Agarwal, A.K. (2022). Combustion in Diesel Fuelled Partially Premixed Compression Ignition Engines. In: Agarwal, A.K., Martínez, A.G., Kalwar, A., Valera, H. (eds) Advanced Combustion for Sustainable Transport. Energy, Environment, and Sustainability. Springer, Singapore. https://doi.org/10.1007/978-981-16-8418-0_5

Link to download: https://drive.google.com/file/d/1SLRFSiJUCEPo7BRIu6YLx8wlG6VPnipI/view?usp=sharing

Abstract: Global concerns about depleting fuel reserves, environment degradation, and sustainability have motivated researchers to explore advanced combustion strategies. In this regard, low-temperature combustion (LTC) has emerged as a promising combustion strategy that can simultaneously reduce soot and NOx emissions with the additional benefit of superior fuel economy. However, researchers must address its primary challenges, w.r.t. controlling ignition timing, combustion phasing, and high heat release rate (HRR), to practically implement it on a large scale. Partially premixed compression ignition (PPCI) is a type of LTC that can address these drawbacks. In PPCI, the injection is closer to ignition when compared with homogeneous charge compression ignition (HCCI), which provides superior control over the ignition. It achieves better mixing and low in-cylinder temperatures using medium to high exhaust gas recirculation (EGR) levels. Optical diagnostics are powerful tools used by researchers to understand the physical behaviour of these complex processes in engines or engine-like conditions. The main attempt of this chapter is to summarize the understandings obtained by researchers about the two-stage combustion occurring in PPCI conditions using optical diagnostics. In the build-up, a brief introduction is given to the conventional diesel combustion (CDC) model and the chemical kinetics involved in the LTC to provide an overall understanding.

Conference Papers

Gasohol Sprays Simulations of a Multi-Hole GDI Injector in Engine-Like Conditions

Authors: Ankur Kalwar, Sam Joe Chintagunti and Avinash Kumar Agarwal 

Reference: Kalwar, A., Chintagunti, S., & Agarwal, A. K. (2021). Gasohol Sprays Simulations of a Multi-Hole GDI Injector in Engine-Like Conditions (No. 2021-01-0549). SAE Technical Paper. 

Link to download: 

Abstract: Mixture formation in GDI engine is considered crucial in determining combustion and emissions characteristics, which mainly depend on fuel spray quality. However, spray characteristics change with variations in control parameters such as fuel injection parameters, fuel injection strategy, engine operating conditions, and fuel properties. Growing research interest in the use of methanol as an additive with gasoline has motivated the need for deeper investigations of spray characteristics of these fuels. Although, it can be noted that sufficient literature is available in the area of spray characterization under several independent influencing factors, however, comparative analysis of gasohol spray behavior under different ambient conditions is hardly studied. This study is aimed at investigating the spray morphology, and evaporation and mixing characteristics of M15 (15% v/v methanol in iso-octane) and M85 (85% v/v methanol in iso-octane) in comparison to iso-octane at early injection and late injection conditions. CFD simulation studies were performed using multi-hole GDI injector in a constant volume spray chamber (CVSC) using Converge software. Numerical model used for the analysis was validated using experimental spray penetration measurements, available at the ECN. The results highlighted that effect of methanol properties on spray penetration and SMD of fuel droplets diminished under high temperature-high pressure conditions. Although, substantial difference in droplets evaporation was found among the test fuels due to inferior volatility of methanol, which definitely demands optimization of fuel injection parameters for adapting methanol blends in the engine. However, despite lower droplet evaporation, equivalence ratio distribution for methanol blends was more shifted towards stoichiometric conditions due to inherent fuel oxygen content.