• Comparative study on the macroscopic characteristics of gasoline and ethanol spray from a GDI injector under injection pressures of 10 and 60 MPa

      Li, Xiang; Li, Dayou; Liu, Jingyin; Ajmal, Tahmina; Aitouche, Abdel; Mobasheri, Raouf; Rybdylova, Oyuna; Pei, Yiqiang; Peng, Zhijun (ACS, 2022-03-04)
      To reduce particulate matter (PM) emissions from vehicles powered by gasoline direct injection (GDI) engines, increasing the fuel injection pressure has been one promising approach. However, a comparison of macroscopic characteristics between gasoline and ethanol from a GDI injector under an ultrahigh injection pressure of more than 50 MPa has not been reported. The experimental study presented in this paper can provide some new and valuable information about comparing and analyzing the macroscopic characteristics of gasoline and ethanol spray from a GDI injector in both front and side views under injection pressures of 10 and 60 MPa. The experimental results show that compared to ethanol, gasoline spray has a slight advantage in LS (penetration of whole spray), LC (penetration of core region of spray), θS (spray cone angle), and RI (irregularity of spray boundary) under both PI (injection pressure) = 10 MPa and PI = 60 MPa, which would promote a more homogeneous mixture of air and fuel. Furthermore, the advantage of gasoline in θS is more pronounced under PI = 60 MPa. At the end of injection, SS (area of whole spray) of gasoline is around 2% larger than ethanol, while its advantage in SC (area of core region of spray) can be around 5%. With the increase of PI from 10 to 60 MPa, a marked increase of RS (the ratio of SC to SS) and RI indicates that atomization and air–fuel mixture homogeneity can be significantly improved for both gasoline and ethanol spray. Besides, a minor revision to the Dent model helps achieve a significant improvement in the prediction accuracy of LS for both gasoline and ethanol spray under injection pressures of 10 and 60 MPa.
    • Effects of water injection strategies on oxy-fuel combustion characteristics of a dual-injection spark ignition engine

      Li, Xiang; Pei, Yiqiang; Li, Dayou; Ajmal, Tahmina; Rana, Khaqan-Jim; Aitouche, Abdel; Mobasheri, Raouf; Peng, Zhijun; University of Bedfordshire; Tianjin University; et al. (MDPI, 2021-08-26)
      Currently, global warming has been a serious issue, which is closely related to anthropogenic emission of Greenhouse Gas (GHG) in the atmosphere, particularly Carbon Dioxide (CO2). To help achieve carbon neutrality by decreasing CO2 emissions, Oxy-Fuel Combustion (OFC) technology is becoming a hot topic in recent years. However, few findings have been reported about the implementation of OFC in dual-injection Spark Ignition (SI) engines. This work numerically explores the effects of Water Injection (WI) strategies on OFC characteristics in a practical dual-injection engine, including GDI (only using GDI), P50-G50 (50% PFI and 50% GDI) and PFI (only using PFI). The findings will help build a conceptual and theoretical foundation for the implementation of OFC technology in dual-injection SI engines, as well as exploring a solution to increase engine efficiency. The results show that compared to Conventional Air Combustion (CAC), there is a significant increase in BSFC under OFC. Ignition delay (θF) is significantly prolonged, and the spark timing is obviously advanced. Combustion duration (θC) of PFI is a bit shorter than that of GDI and P50-G50. There is a small benefit to BSFC under a low water-fuel mass ratio (Rwf). However, with the further increase of Rwf from 0.2 to 0.9, there is an increment of 4.29%, 3.6% and 3.77% in BSFC for GDI, P50-G50 and PFI, respectively. As WI timing (tWI) postpones to around −30 °CA under the conditions of Rwf ≥ 0.8, BSFC has a sharp decrease of more than 6 g/kWh, and this decline is more evident under GDI injection strategy. The variation of maximum cylinder pressure (Pmax) and combustion phasing is less affected by WI temperature (TWI) compared to the effects of Rwf or tWI. BSFC just has a small decline with the increase of TWI from 298 K to 368 K regardless of the injection strategy. Consequently, appropriate WI strategies are beneficial to OFC combustion in a dual-injection SI engine, but the benefit in fuel economy is limited.
    • Exploring the potential benefits of Ethanol Direct Injection (EDI) timing and pressure on particulate emission characteristics in a Dual-Fuel Spark Ignition (DFSI) engine

      Li, Xiang; Li, Dayou; Liu, Jingyin; Ajmal, Tahmina; Aitouche, Abdel; Mobasheri, Raouf; Rybdylova, Oyuna; Pei, Yiqiang; Peng, Zhijun; ; et al. (Elsevier, 2022-04-26)
      Nowadays, particulate matter emitted by vehicles severely impacts environmental quality and human health. In this paper, the potential benefits of Ethanol Direct Injection (EDI) timing and pressure on particulate emission characteristics in a Dual-Fuel Spark Ignition (DFSI) engine were initially and systematically explored. The experimental results illustrate that by delaying EDI timing from -340 ºCA to -300 ºCA, there is a significant benefit in both particulate number and mass concentration. Furthermore, the size distribution curve of particulate number changes from bimodal to unimodal, meantime size distribution curves of particulate mass consistently concentrate on the accumulation mode. By increasing EDI pressure from 5.5 MPa to 18 MPa, the droplet size of ethanol spray can be effectively reduced. The benefit of increasing EDI pressure is more apparent in reducing particulate number is than particulate mass. The concentration of number and mass for total particulates have a reduction of 51.15% and 22.64%, respectively. In summary, it was demonstrated that an appropriate EDI timing or high EDI pressure could be a practical and efficient way to reduce particulate emissions in a DFSI engine.
    • A feasibility study of implementation of oxy-fuel combustion on a practical diesel engine at the economical oxygen-fuel ratios by computer simulation

      Li, Xiang; Peng, Zhijun; Ajmal, Tahmina; Aitouche, Abdel; Mobasheri, Raouf; Pei, Yiqiang; Gao, Bo; Wellers, Matthias; University of Bedfordshire; Centre de Recherche en Informatique Signal et Automatique de Lille; et al. (SAGE Publications, 2020-12-09)
      To help achieve zero carbon emissions from inland waterway vessels, this implementation of oxy-fuel combustion on a practical diesel engine at the economical oxygen-fuel ratios were systematically studied and analysed in this paper. A 1-D simulation was used to explore the effect of various operating parameters for recovering the engine power when the engine is modified to the oxy-fuel combustion from conventional air combustion. The brake power of oxy-fuel combustion is only 26.7kW that has a noticeable decline compared with 40 kWof conventional air combustion with fixed consumption of fuel and oxygen. By optimising some valuable parameters, like fuel injection timing, intake charge temperature, intake components, engine compression ratio and water injection strategy, a benefit of 6.8kW has been acquired in the engine power. Afterwards, a remarkable benefit was obtained with the increase of lambdaO2 from 1.0 to 1.5, finally obtaining the same engine power with the conventional air combustion. Above all, taking advantage of various operating parameters, it is expected to further improve the value of the implement of oxy-fuel combustion on diesel engines at the economical oxygen-fuel ratios.
    • Implementation of oxy-fuel combustion (OFC) technology in a gasoline direct injection (GDI) engine fueled with gasoline–ethanol blends

      Li, Xiang; Pei, Yiqiang; Li, Dayou; Ajmal, Tahmina; Aitouche, Abdel; Mobasheri, Raouf; Peng, Zhijun (American Chemical Society, 2021-10-27)
      Nowadays, to mitigate the global warming problem, the requirement of carbon neutrality has become more urgent. Oxy-fuel combustion (OFC) has been proposed as a promising way of carbon capture and storage (CCS) to eliminate carbon dioxide (CO2) emissions. This article explores the implementation of OFC technology in a practical gasoline direct injection (GDI) engine fueled with gasoline–ethanol blends, including E0 (gasoline), E25 (25% ethanol, 75% is gasoline in mass fraction), and E50 (50% ethanol, 50% is gasoline in mass fraction). The results show that with a fixed spark timing, φCA50 (where 50% fuel is burned), of E50 and E25 is about 4.5 and 1.9° later than that of E0, respectively. Ignition delay (θF) and combustion duration (θC) can be extended with the increase of the ethanol fraction in the blended fuel. With the increase of the oxygen mass fraction (OMF) from 23.3 to 29%, equivalent brake-specific fuel consumption (BSFCE) has a benefit of 2.12, 1.65, and 1.51% for E0, E25, and E50, respectively. The corresponding increase in brake-specific oxygen consumption (BSOC) is 21.83, 22.42, and 22.58%, respectively. Meanwhile, θF, θC, and the heat release rate (HRR) are not strongly affected by the OMF. With the increase of the OMF, the increment of θF is 0.7, 1.8, and 2.2° for E0, E25, and E50, respectively. θC is only extended by 1, 1.1, and 1.4°, respectively. Besides, by increasing the intake temperature (TI) from 298 to 358 K under all of the fuel conditions, BSFCE and BSOC present slight growth trends; θF and θC are slightly reduced; in the meantime, φCA50, φPmax (crank angle of peak cylinder pressure), and the position of the HRR peak are advanced by nearly 1°.
    • Investigation of oxyfuel combustion on engine performance and emissions in a DI diesel HCCI engine

      Mobasheri, Raouf; Izza, Nadia; Aitouche, Abdel; Peng, Jun; Bakir, Boualem (IEEE, 2020-01-09)
      Due to stronger environmental standard aims, the European Union (EU) has recently adopted more stringent limits for emissions from inland waterway vessels. The objective of “RIVER” project is to apply an oxyfuel combustion technology for diesel engines that eliminates NOx emissions, and captures and stores all carbon dioxide emissions in order to achieve zero-carbon and zero other pollutant emissions. As part of this project, a 3-D computational fluid dynamics model coupled with detailed chemical kinetics has been used to evaluate the influence of oxyfuel combustion on engine operating conditions and combustion characteristic in a high speed direct injection (HSDI) diesel engine under homogenous charge compression ignition (HCCI) mode. In this work, a reduced chemical n-heptane-n-butanol-PAH mechanism which consists 76 species and 349 reactions has been applied to simulate the combustion process. The mechanism has been initially validated by experiments under HCCI combustion mode and then, it has been used to examine the oxyfuel combustion using different diluent strategies over a range of air-fuel equivalence ratio (lambda). The simulation results indicate that increasing the inlet carbon dioxide concentration, as a diluent gas, under constant fueling rate does not bring any serious change to the amount of brake mean effective pressure (BMEP) in the relatively rich mixtures regions. However, by decreasing the fuel rate (higher lambda) the difference between different diluent strategies become more obvious as the minimum amount of BMEP is achieved when 83% of carbon dioxide is used. In addition, the results show a considerable reduction of PM emissions while the NOx emission have been completely eliminated using oxyfuel combustion.
    • Numerical investigation on implementing Oxy-Fuel Combustion (OFC) in an ethanol-gasoline Dual-Fuel Spark Ignition (DFSI) engine

      Li, Xiang; Pei, Yiqiang; Ajmal, Tahmina; Rana, Khaqan-Jim; Aitouche, Abdel; Mobasheri, Raouf; Peng, Zhijun; University of Bedfordshire; Tianjin University; CRIStAL - Centre de Recherche en Informatique Signal et Automatique de Lille; et al. (Elsevier, 2021-06-08)
      To decrease even eliminate Carbon Dioxide (CO2) emissions for mitigating global warming, various technologies are being developed on combustion engines. In the research presented in this paper, a numerical investigation of Oxy-Fuel Combustion (OFC) technology on an ethanol-gasoline Dual-Fuel Spark Ignition (DFSI) engine under economical oxygen consumption at low and mid-high loads was performed by one-dimensional computer simulation. It is demonstrated that under OFC mode without other optimisation, Brake Mean Effective Pressure (BMEP) can meet the requirement at mid-high load, but it has a considerable decline at low load compared to Conventional Air Combustion (CAC) mode. Moreover, there is a considerable deterioration in Brake Specific Fuel Consumption (BSFC) compared to that of CAC mode. A practical method is proposed to optimise the DFSI engine performance under OFC mode by changing intake charge components and utilising appropriate Water Injection (WI) strategies. BMEP increases approximately 0.05 bar at low load. BSFC has a reduction of 3.35% and 1.82% at low load and mid-high load, respectively.
    • Numerical study on the effects of intake charge on oxy-fuel combustion in a dual-injection spark ignition engine at economical oxygen-fuel ratios

      Li, Xiang; Pei, Yiqiang; Peng, Zhijun; Ajmal, Tahmina; Rana, Khaqan-Jim; Aitouche, Abdel; Mobasheri, Raouf (SAGE, 2021-05-28)
      In order to decrease Carbon Dioxide (CO2) emissions, Oxy-Fuel Combustion (OFC) technology with Carbon Capture and Storage (CCS) is being developed in Internal Combustion Engine (ICE). In this article, a numerical study about the effects of intake charge on OFC was conducted in a dual-injection. Spark Ignition (SI) engine, with Gasoline Direct Injection (GDI), Port Fuel Injection (PFI) and P-G (50% PFI and 50% GDI) three injection strategies. The results show that under OFC with fixed Oxygen Mass Fraction (OMF) and intake temperature, the maximum Brake Mean Effective Pressure (BMEP) is each 5.671, 5.649 and 5.646 bar for GDI, P-G and PFI strategy, which leads to a considerable decrease compared to Conventional Air Combustion (CAC).
    • Oxy-fuel combustion for carbon capture and storage in internal combustion engines - a review

      Li, Xiang; Peng, Zhijun; Pei, Yiqiang; Ajmal, Tahmina; Rana, Khaqan-Jim; Aitouche, Abdel; Mobasheri, Raouf; ; University of Bedfordshire; Tianjin University; et al. (2021-08-18)
      As the impacts of global warming have become increasingly severe, oxy-fuel combustion has been widely considered a promising solution for carbon capture and storage (CCS) to reduce carbon dioxide (CO2) to achieve net-zero emissions. In the past few decades, researchers around the world have demonstrated improvements by the application of oxy-fuel combustion to internal combustion (IC) engines. This article presents a comprehensive review of the experimental and simulation studies about oxy-combustion for CCS in IC engines. To give a more comprehensive understanding, it has included a detailed explanation of the essential components contained in an oxy-fuel IC engine and its typical operating parameters. The oxy-fuel IC engine components include the system of oxygen supply, exhaust gas recirculation (EGR), water injection, fuel injection, and CCS. In order to optimise the combustion process, it is required to adopt the appropriate values for the oxygen concentration, EGR rate, ignition timing, compression ratio, fuel injection, and water injection in oxy-fuel engines. The detailed literature review and analysis presented provide a basis for the selection of oxy-fuel combustion for CCS as a prospective solution to reduce carbon emissions in IC engines.
    • Simulation study on implementation of oxy-fuel combustion for a practical GDI engine

      Li, Xiang; Peng, Zhijun; Ajmal, Tahmina; Rana, Khaqan-Jim; Aitouche, Abdel; Mobasheri, Raouf; Pei, Yiqiang; University of Bedfordshire; University of Lille; Tianjin University (SAE, 2021-04-06)
      As the impacts of global warming have become increasingly severe, Oxy-Fuel Combustion (OFC) has been widely considered as a promising solution to reduce Carbon Dioxide (CO2) for achieving net-zero emissions. In this study, a one-dimensional simulation was carried out to study the implementation of OFC technology on a practical turbocharged 4-cylinder Gasoline Direct Injection (GDI) engine with economical oxygen-fuel ratios and commercial gasoline. When the engine is converted from Conventional Air-fuel Combustion (CAC) mode to OFC mode, and the throttle opening, oxygen mass fraction, stoichiometric air-fuel ratio (lambda = 1) are kept constant, it was demonstrated that compared to CAC mode, θF gets a remarkable extension whereas θC is hardly affected. θF and θC are very sensitive to the ignition timing, and Brake Specific Fuel Consumption (BSFC) would benefit significantly from applying Maximum Brake Torque (MBT) ignition timing. However, the power still does not reach the target at low load. With oxygen fraction increasing from 23.3% to 32%, it was found that θF and θC remain largely steady at low load and would extend a few degrees at m-h load. BSFC respectively gets a reduction of 33 g/kWh and 8.9 g/kWh. Meanwhile, Brake Specific Oxygen Consumption (BSOC) increases 677.9 g/kWh and 363.9 g/kWh, leading to a considerable cost that should be weighed under OFC mode of practical applications.