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Numerical Investigation of Diesel-Spray-Orientated Piston Bowls on Natural Gas and Diesel Dual Fuel Combustion Engine

Zhaojie Shen
Brunel University-Xinyan Wang, Hua Zhao
  • Technical Paper
  • 2020-01-0311
To be published on 2020-04-14 by SAE International in United States
Low combustion efficiency and high hydrocarbon emissions at low loads are key issues of natural gas and diesel (NG-diesel) dual fuel engines. For better engine performance, two diesel-spray-orientated (DSO) bowls were developed based on the existing diesel injector of a heavy-duty diesel engine with the purpose of placing more combustible natural gas/air mixture around the diesel spray jets. A protrusion-ring was designed at the rim of the piston bowl to enhance the in-cylinder flame propagation. Numerical simulations were conducted for a whole engine cycle at engine speed of 1200 r/min and indicated mean effective pressure (IMEP) of 0.6 MPa. Extended coherent flame model 3 zones (ECFM-3Z) combustion model with built-in soot emissions model was employed. Simulation results of the original piston bowl agreed well with the experimental data, including in-cylinder pressure and heat released rate (HRR), as well as soot and methane emissions. Turbulence kinetic energy, IMEP and methane emissions of the DSO piston geometries were compared with that of the original piston geometry. The results showed that both in-cylinder pressure and heat release rate…
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Effect of a Split-Injection Strategy on the Atomisation Rate Using a High Pressure Gasoline DI Injector

Brunel University-Meghnaa Paresh Dhanji, Hua Zhao
  • Technical Paper
  • 2020-01-0322
To be published on 2020-04-14 by SAE International in United States
The Gasoline direct-injection (GDI) engine can emit high levels of particulate matter and unburned Hydrocarbons when operating under stratified charge combustion mode. Injecting late in the compression stroke means the fuel has insufficient time to atomise and evaporate. This could cause fuel film accumulation on the piston surface and combustion liner. Locally fuel rich diffusion combustion could also result in the formation of soot particles. Employing a split-injection strategy can help tackle these issues. The first injection is initiated early in the intake stroke and could ensure a global homogeneous charge. The second injection during the compression stroke could help form a fuel-rich charge in the vicinity of the spark plug. Many studies have established the crucial role that a split-injection strategy plays in the stratified charge operation of GDI engines. The current study examines how a split-injection strategy affects the flow field and spray characteristics at high injection pressure. This is done by analysing the global spray structures and the atomisation rates. In particular, the effects of changing dwell times between injections on the…
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Axial Flow Turbine Concept for Conventional and e-Turbocharging

Brunel University-Apostolos Pesyridis
Universita di Napoli Federico II-Alessandro Cappiello, Raffaele Tuccillo, Maria Cristina Cameretti
Published 2019-09-09 by SAE International in United States
Engine downsizing has established itself as one of the most successful strategies to reduce fuel consumption and pollutant emissions in the automotive field. To this regard, a major role is played by turbocharging, which allows an increase in engine power density, so reducing engine size and weight. However, the need for turbocharging imposes some issues to be solved. In the attempt of mitigating turbo lag and poor low-end torque, many solutions have been presented in the open literature so far, such as: low inertia turbine wheels and variable geometry turbines; or even more complex concepts such as twin turbo and electrically assisted turbochargers. None of them appears as definitive, though.As a possible way of reducing turbine rotor inertia, and so the turbo lag, also the change of turbine layout has been investigated, and it revealed itself to be a viable option, leading to the use of mixed-flow turbines. Only recently, the use of axial-flow turbines, with the aim of reducing rotor inertia, has been proposed as well.The current paper documents a case study involving the…
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Experimental Studies of Gasoline Auxiliary Fueled Turbulent Jet Igniter at Different Speeds in Single Cylinder Engine

Brunel University-Khalifa Isa Bureshaid, Hua Zhao
Mahle Powertrain Ltd-Michael Bunce
Published 2019-09-09 by SAE International in United States
Turbulent Jet Ignition (TJI) is a pre-chamber ignition system for an otherwise standard gasoline spark ignition engine. TJI works by injecting chemically active turbulent jets to initiate combustion in a premixed fuel/air mixture. The main advantage of TJI is its ability to ignite and burn, completely, very lean fuel/air mixtures in the main chamber charge. This occurs with a very fast burn rate due to the widely distributed ignition sites that consume the main charge rapidly. Rapid combustion of lean mixtures leads to lower exhaust emissions due to more complete combustion at a lower temperature.For this research, the effectiveness of the Mahle TJI system on combustion stability, lean limit and emissions in a single cylinder spark engine fueled with gasoline at different speeds was investigated. The combustion and heat release process was analyzed and the exhaust emissions were measured. The results show that the effect of the Mahle TJI system on the lean-burn limit and exhaust emissions varied with engine speeds. The lean limit was extended by increasing the engine speed, to λ = 1.71…
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Dilution Boundary Expansion Mechanism of SI-CAI Hybrid Combustion Based on Micro Flame Ignition Strategy

Brunel University-Hua Zhao
Tianjin University-Yifang Feng, Tao Chen, Hui Xie, Longlong Zhang
Published 2019-04-02 by SAE International in United States
In decade years, Spark Ignition-Controlled Auto Ignition (SI-CAI) hybrid combustion, also called Spark Assisted Compression Ignition (SACI) has shown its high-efficiency and low emissions advantages. However, high dilution causes the problem of unstable initial ignition and flame propagation, which leads to high cyclic variation of heat release and IMEP. The instability of SI-CAI hybrid combustion limits its dilution degree and its ability to improve the thermal efficiency. In order to solve instability problems and expand the dilution boundary of hybrid combustion, micro flame ignition (MFI) strategy is applied in gasoline hybrid combustion engines. Small amount of Dimethyl Ether (DME) chosen as the ignition fuel is injected into cylinder to form micro flame kernel, which can stabilize the ignition combustion process. Experimental results of the single cylinder engine showed that MFI strategy raises the dilution boundary from lambda 1.2 to 2.0 and thermal efficiency from 33.65% to 42.87% at 2000 rpm and IMEP 4 bar. Computational Fluid Dynamics (CFD) numerical simulation analysis indicate that the early injection case showed a 2-stage heat release process with one…
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Experimental Investigation of Combustion and Emission Characteristics of Stoichiometric Stratified Flame Ignited (SFI) Hybrid Combustion in a 4-Stroke PFI/DI Gasoline Engine

Brunel University-Hua Zhao
China North Engine Research Institute-Yan Zhang, Yufeng Li, Honglin Bai
Published 2019-04-02 by SAE International in United States
Controlled Auto-Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), can improve the fuel economy of gasoline engines and simultaneously achieve ultra-low NOx emissions. However, the difficulty in combustion phasing control and violent combustion at high loads limit the commercial application of CAI combustion. To overcome these problems, stratified mixture, which is rich around the central spark plug and lean around the cylinder wall, is formed through port fuel injection and direct injection of gasoline. In this condition, rich mixture is consumed by flame propagation after spark ignition, while the unburned lean mixture auto-ignites due to the increased in-cylinder temperature during flame propagation, i.e., stratified flame ignited (SFI) hybrid combustion. The combustion and emissions characteristics in the SFI combustion were experimentally investigated in a naturally aspirated single-cylinder 4-stroke gasoline engine at medium-high loads when direct injection timing was kept at -60 °CA after top dead center and direct injection ratio was less than or equal to 0.4 at stoichiometry. The results show that advanced spark timing or decreased direct injection ratio alters the SFI…
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Analyzing the Limitations of the Rider and Electric Motorcycle at the Pikes Peak International Hill Climb Race

Brunel University-Koen Matthys
Eric Wu Engineering-Eric Wu
Published 2019-04-02 by SAE International in United States
This paper describes a post-race analysis of team KOMMIT EVT’s electric motorcycle data collected during the 2016 Pikes Peak International Hill Climb (PPIHC). The motorcycle consumed approximately 4 kWh of battery energy with an average and maximum speed of 107 km/h and 149 km/h, respectively. It was the second fastest electric motorcycle with a finishing time of 11:10.480. Data was logged of the motorcycle’s speed, acceleration, motor speed, power, currents, voltages, temperatures, throttle position, GPS position, rider’s heart rate and the ambient environment (air temperature, pressure and humidity). The data was used to understand the following factors that may have prevented a faster time: physical fitness of the rider, thermal limits of the motor and controller, available battery energy and the sprocket ratio between the motor and rear wheel. Even though the rider’s heart rate implied a vigorous exercise intensity level, throttle values indicated that the rider wanted to go faster ~33% of the time. The motor reached a steady-state temperature that was approximately 30°C below the maximum allowable temperature and thus could have handled…
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The Application of Controlled Auto-Ignition Gasoline Engines -The Challenges and Solutions

Brunel University-Hua Zhao
China North Engine Research Institute-Yan Zhang, Yufeng Li, Honglin Bai
Published 2019-04-02 by SAE International in United States
Controlled Auto-Ignition (CAI) combustion, also known as Homogeneous Charge Compression Ignition (HCCI), has the potential to simultaneously reduce the fuel consumption and nitrogen oxides emissions of gasoline engines. However, narrow operating region in loads and speeds is one of the challenges for the commercial application of CAI combustion to gasoline engines. Therefore, the extension of loads and speeds is an important prerequisite for the commercial application of CAI combustion. The effect of intake charge boosting, charge stratification and spark-assisted ignition on the operating range in CAI mode was reviewed. Stratified flame ignited (SFI) hybrid combustion is one form to achieve CAI combustion under the conditions of highly diluted mixture caused by the flame in the stratified mixture with the help of spark plug. CAI combustion in two-stroke gasoline engine can be used to enhance the torque of a four-stroke gasoline engine with the same displacement at the same indicated mean effective pressure. Poppet-valved two-stroke gasoline engines with normal valve lift and variable valve timing device, and uniflow two-stroke engine with gas exchange process completed by…
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Simulation of the Effect of Intake Pressure and Split Injection on Lean Combustion Characteristics of a Poppet-Valve Two-Stroke Direct Injection Gasoline Engine at High Loads

Brunel University-Hua Zhao
China North Engine Research Institute-Yan Zhang, Yufeng Li, Honglin Bai
Published 2018-09-10 by SAE International in United States
Poppet-valve two-stroke gasoline engines can increase the specific power of their four-stroke counterparts with the same displacement and hence decrease fuel consumption. However, knock may occur at high loads. Therefore, the combustion with stratified lean mixture was proposed to decrease knock tendency and improve combustion stability in a poppet-valve two-stroke direct injection gasoline engine. The effect of intake pressure and split injection on fuel distribution, combustion and knock intensity in lean mixture conditions at high loads was simulated with a three-dimensional computational fluid dynamic software. Simulation results show that with the increase of intake pressure, the average fuel-air equivalent ratio in the cylinder decreases when the second injection ratio was fixed at 70% at a given amount of fuel in a cycle. With the increase of intake pressure, ignition timing advances, combustion duration slightly decreases first and then increases while the maximum pressure rise rate first increases and then drops. High intake pressure can prevent the occurrence of knock through decreased fuel-air equivalent ratio around the cylinder. The second injection timing can also influence combustion…
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Potentials of External Exhaust Gas Recirculation and Water Injection for the Improvement in Fuel Economy of a Poppet Valve 2-Stroke Gasoline Engine Equipped with a Two-Stage Serial Charging System

Brunel University-Hua Zhao
Tianjin University-Xue-Qing Fu, Bang-Quan He, Sipeng Xu
Published 2018-04-03 by SAE International in United States
Engine downsizing is one of the most effective means to improve the fuel economy of spark ignition (SI) gasoline engines because of lower pumping and friction losses. However, the occurrence of knocking combustion or even low-speed pre-ignition at high loads is a severe problem. One solution to significantly increase the upper load range of a 4-stroke gasoline engine is to use 2-stroke cycle due to the double firing frequency at the same engine speed. It was found that a 0.7 L two-cylinder 2-stroke poppet valve gasoline engine equipped with a two-stage serial boosting system, comprising a supercharger and a downstream turbocharger, could replace a 1.6 L naturally aspirated 4-stroke gasoline engine in our previous research, but its fuel economy was close to that of the 4-stroke engine at upper loads due to knocking combustion. Two promising approaches, including external exhaust gas recirculation (eEGR) and water injection (WI), were investigated to improve the fuel economy of the 2-stroke engine by means of a 1-D simulation. Knocking combustion is limited by elongated combustion process and suppressed decomposition of hydrogen…
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