Computational Fluid Dynamics Modelling And Validation Of In-Cylinder Processes In Internal Combustion Engines Patrick Chakanyuka The Sir Harry Ricardo Laboratories - Centre for Automotive Engineering Faculty of Science and Engineering, University of Brighton, Brighton, BN2 4GJ CONCLUSIONS : • An oscillatory character of air filling process is observed for all 3D cases with constant inlet pressure boundary conditions. It is observed that higher inlet pressure fills up the engine cylinder faster as shown in Table 1 for time = 0.5ms Table 1 In-cylinder mass and pressure show damping oscillations with period of 1.6ms. Maximum in-cylinder pressure is achieved at 1ms in all five cases whilst inlet mass flowrate has phase shift and it is zero at 1 ms. Five 3D CFD cases were ran, with inlet pressures in the range 7 – 15bar. Each run lasted 5ms to explore long-term character of the oscillatory process. Amplification effects: For 3D case, in-cylinder pressure can exceed the inlet pressure at certain time (in our case, at 1ms). Advantages: Higher in-cylinder pressure (ICP) allows to burn more fuel. Possible problem: Knock might occur for pressures exceeding 10 bar. • 3D CFD simulations with massflowrate boundary conditions give monotonic in-cylinder pressure rise. A steep rise in cylinder pressure starts at about 0.15ms for all three values of massflowrate. This is associated with the traveling time along the inlet duct : inlet duct length is 64mm and velocity of sound is about 400 m/s; this gives 0.16 ms for high pressure front to reach the engine cylinder • Choked flow is observed in both 3D and 2D simulations. Flow at the inlet is initially subsonic and its velocity increases to high Mach numbers as it flows through the smaller cross-sectional area of the restriction. Flow velocities are high in the areas of low pressure due to Bernoulli’s principle. • Toroidal vortex rings are formed in 2D case and they are evolving with time. Recommendations for further work: • Investigation of frequency of the oscillations for different piston positions. • Investigation of vortex ring formation, evolution and comparison with theory. Vortex rings can serve as a vehicle for capturing fuel spray and directing it to spark plug. RESULTS:3D CFD Simulation for Inlet Pressure Boundary Conditions: amplification effects 3D CFD Simulation for Inlet Massflowrate Boundary Conditions 7 g/s AIMS: Analysis of rapid air filling process in a split-cycle internal combustion engine by CFD simulations. OBJECTIVES: • Review of recent trends in automotive industry research • Analysis of split-cycle engine concept and advantages of rapid air filling process • Review and setup of relevant 2D and 3D CFD cases for parametric studies of in-cylinder filling process • CFD simulation of air flow through the inlet duct for a realistic 3D geometry of cylinder head with a) inlet pressure boundary conditions, b) massflowrate boundary conditions • Feasibility studies for the design of a validation experiment: CFD simulation of air filling of cylinder with inlet pressure boundary conditions via narrow duct • Conclusions and recommendations for further validation research and the engine design METHODOLOGY FOR CFD SETUP: Air is injected from compressor through intake duct. The intake valve is fully open. Exhaust duct is closed. Initial in-cylinder conditions are: pressure is 1 bar and 350K. The calculation is run with a time step of 1e-05s until 5ms to study dynamics of reflected pressure waves. Compressible gas law. ACKNOWLEDGEMENTS: I thank Dr E. SAZHINA my supervisor for her guidance and support; Dr O Rybdylova for her consultations and expertise on compressible flows and vortex formation. I also thank Dr D Coren for his constructive comments. This project has greatly benefitted from close collaboration with the CEREEV team. My special thanks are to Dr S Begg and Dr D Mason. Last but not least I am deeply grateful to my entire family for their support. CEREEV(Combustion Engine for Range-Extended Electric Vehicle) INTERREG Project: Task under investigation of current project under CEREEV: Rapid air Filling of engine Cylinder. The project aims to explore rapid air filling process of split-cycle engine using Computational Fluid Dynamics (CFD). This new engine type performs combustion and compression in separate cylinders. • The thermodynamics of the proposed engine requires rapid filling in the power cylinder where combustion will take place. Fuel spray is injected simultaneously but at different in-cylinder location. This shall help to overcome problems of volumetric efficiency and combustion phasing. • The realistic time for rapid air filling is less than 1.7ms for 1000rpm (D Mason,private communication) METHODOLOGY SUMMARY: CFD study for a new SHRL test: Setup of 2D Air-Spray Cases. A cylinder 400 mm long and 80 mm diameter is proposed as a design facility set in SHRL to allow visualisation of the flow pattern by laser diagnostics methods. Air is injected through a nozzle 200μ radius. A 2D axisymmetric geometry has been set up in ANSYS FLUENT. Boundary conditions: for inlet, fixed pressure of (a) 1MPa and (b) 1.8MPa. The rest of the boundaries are set to wall type. Initial conditions: In-cylinder pressure is 0.1MPa and temperature 350K. Initial pressure in the nozzle is lower than inlet pressure by 0.01MPa to facilitate convergence at first time steps. CFD study for a 3D realistic engine mesh. The engine geometry and mesh were inherited after 2-ACE project for a gasoline engine but the setup has been adapted for split-cycle engine. Air comes from compressor cylinder via inlet duct with inlet valve being fully open. Air flow is modelled using ideal gas law, energy and turbulence model with compressibility effects. The simulations ran with a time step of 1microsecond until 5ms. Two types of boundary conditions are explored in realistic ranges: • Fixed inlet pressure and T: Inlet pressures were set at 0.7 MPa, 0.9MPa, 1.0MPa, 1.2MPa, and 1.5MPa at 350K. • Fixed mass flowrate and T: Inlet massflowrate was set at 0.007 kg/s , 0.07 kg/s and 0.7 kg/s at 350K Inlet Initial in-cylinder pressure: 1 bar Exhaust valve is closed Exploring rapid filling process of cylinder by air 3D CFD analysis of filling the cylinder process 1. Inlet pressures: 0.7 MPa, 0.9, 1.2MPa, 1.5MPa at 350K 2. Mass flowrate: 0.007 kg/s , 0.07 kg/s and 0.7 kg/s high mass flowrate at 350K CEREEV TEAM Air Spray: Rapid Filling of Cylinder of 80mm diameter the nozzle has the diameter of 200 microns CFD Simulation of Transonic Flow Inlet Pressure Boundary Conditions 2D Axisymmetric mesh Vortex ring formation for air injection via nozzle of 200μ diameter at 18 bar fixed inlet pressure 0.1ms 0.05ms 0.2ms 0.05ms 0.2ms Pressure distribution (Pa) Velocity magnitude (m·s-1) Pressure distribution (Pa) Pressure distribution (Pa) Velocity magnitude (m/s) 1 1.1 1.2 1.3 1.4 0 0.05 0.1 0.15 0.2 0.25 0.3 Pressure (bar) In-cylinder pressure rate increases at 0.15 Fixed inlet P = 15bar In-Cylinder P = 20bar at 1ms Choked flow (Ma > 1) for 18 bar fixed inlet pressure Comparison in-cylinder gauge pressures vs time: red 1.8MPa and blue1MPa 0 0.5 1 1.5 2 0 0.5 1 1.5 2 Pressure (Pa) Time (ms) At 1ms 1.8MPa and 1MPa have 0.9Pa and 0.5Pa in- cylinder gauge pressures respectively Inlet duct travel time = 65mm /390m/s = 0.16ms 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 1 2 3 4 5 Pressure (MPa) Time(ms) Inlet pressure (bar) ICP (bar) 7 5.5 9 7 10 8 12 9 15 11 RESULTS 2D:
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Computational Fluid Dynamics Modelling And Validation Of In-Cylinder Processes In Internal Combustion Engines
Patrick Chakanyuka The Sir Harry Ricardo Laboratories - Centre for Automotive Engineering
Faculty of Science and Engineering, University of Brighton, Brighton, BN2 4GJ
CONCLUSIONS :
• An oscillatory character of air filling process is observed for all
3D cases with constant inlet pressure boundary conditions.
It is observed that higher inlet pressure fills up the engine
cylinder faster as shown in Table 1 for time = 0.5ms Table 1
In-cylinder mass and pressure show damping oscillations with period of 1.6ms.
Maximum in-cylinder pressure is achieved at 1ms in all five cases whilst inlet mass flowrate has phase
shift and it is zero at 1 ms. Five 3D CFD cases were ran, with inlet pressures in the range 7 – 15bar.
Each run lasted 5ms to explore long-term character of the oscillatory process.
Amplification effects:
For 3D case, in-cylinder pressure can exceed the inlet pressure at certain time (in our case, at 1ms).
Advantages: Higher in-cylinder pressure (ICP) allows to burn more fuel.
Possible problem: Knock might occur for pressures exceeding 10 bar.
• 3D CFD simulations with massflowrate boundary conditions give monotonic in-cylinder pressure rise.
A steep rise in cylinder pressure starts at about 0.15ms for all three values of massflowrate. This is
associated with the traveling time along the inlet duct : inlet duct length is 64mm and velocity of sound is
about 400 m/s; this gives 0.16 ms for high pressure front to reach the engine cylinder
• Choked flow is observed in both 3D and 2D simulations. Flow at the inlet is initially subsonic and its
velocity increases to high Mach numbers as it flows through the smaller cross-sectional area of the
restriction. Flow velocities are high in the areas of low pressure due to Bernoulli’s principle.
• Toroidal vortex rings are formed in 2D case and they are evolving with time.
Recommendations for further work:
• Investigation of frequency of the oscillations for different piston positions.
• Investigation of vortex ring formation, evolution and comparison with theory.
Vortex rings can serve as a vehicle for capturing fuel spray and directing it to spark plug.
RESULTS:3D CFD Simulation for Inlet Pressure Boundary Conditions: amplification effects
3D CFD Simulation for Inlet Massflowrate Boundary Conditions 7 g/s
AIMS: Analysis of rapid air filling process in a split-cycle internal combustion engine by CFD simulations.
OBJECTIVES:
• Review of recent trends in automotive industry research
• Analysis of split-cycle engine concept and advantages of rapid air filling process
• Review and setup of relevant 2D and 3D CFD cases for parametric studies of in-cylinder filling process
• CFD simulation of air flow through the inlet duct for a realistic 3D geometry of cylinder head with a) inlet
pressure boundary conditions, b) massflowrate boundary conditions
• Feasibility studies for the design of a validation experiment: CFD simulation of air filling of cylinder with
inlet pressure boundary conditions via narrow duct
• Conclusions and recommendations for further validation research and the engine design
METHODOLOGY FOR CFD SETUP:
Air is injected from compressor through intake duct. The intake valve is fully open. Exhaust duct is closed.
Initial in-cylinder conditions are: pressure is 1 bar and 350K. The calculation is run with a time step of 1e-05s
until 5ms to study dynamics of reflected pressure waves. Compressible gas law.
ACKNOWLEDGEMENTS:
I thank Dr E. SAZHINA my supervisor for her guidance and support; Dr O Rybdylova for her
consultations and expertise on compressible flows and vortex formation.
I also thank Dr D Coren for his constructive comments. This project has greatly benefitted from close
collaboration with the CEREEV team. My special thanks are to Dr S Begg and Dr D Mason.
Last but not least I am deeply grateful to my entire family for their support.
CEREEV(Combustion Engine for Range-Extended Electric Vehicle) INTERREG Project:
Task under investigation of current project under CEREEV: Rapid air Filling of engine Cylinder.
The project aims to explore rapid air filling process of split-cycle engine using Computational Fluid
Dynamics (CFD). This new engine type performs combustion and compression in separate cylinders.
• The thermodynamics of the proposed engine requires rapid filling in the power cylinder where
combustion will take place. Fuel spray is injected simultaneously but at different in-cylinder location.
This shall help to overcome problems of volumetric efficiency and combustion phasing.
• The realistic time for rapid air filling is less than 1.7ms for 1000rpm (D Mason,private communication)
METHODOLOGY SUMMARY:
CFD study for a new SHRL test: Setup of 2D Air-Spray Cases.
A cylinder 400 mm long and 80 mm diameter is proposed as a design facility set in SHRL to allow
visualisation of the flow pattern by laser diagnostics methods. Air is injected through a nozzle 200µ
radius. A 2D axisymmetric geometry has been set up in ANSYS FLUENT.
Boundary conditions: for inlet, fixed pressure of (a) 1MPa and (b) 1.8MPa. The rest of the boundaries are
set to wall type.
Initial conditions: In-cylinder pressure is 0.1MPa and temperature 350K. Initial pressure in the nozzle is
lower than inlet pressure by 0.01MPa to facilitate convergence at first time steps.
CFD study for a 3D realistic engine mesh.
The engine geometry and mesh were inherited after 2-ACE project for a gasoline engine but the setup
has been adapted for split-cycle engine. Air comes from compressor cylinder via inlet duct with inlet
valve being fully open. Air flow is modelled using ideal gas law, energy and turbulence model with
compressibility effects. The simulations ran with a time step of 1microsecond until 5ms.
Two types of boundary conditions are explored in realistic ranges:
• Fixed inlet pressure and T: Inlet pressures were set at 0.7 MPa, 0.9MPa, 1.0MPa, 1.2MPa, and
1.5MPa at 350K.
• Fixed mass flowrate and T: Inlet massflowrate was set at 0.007 kg/s , 0.07 kg/s and 0.7 kg/s at 350K
Inlet
Initial in-cylinder pressure: 1 bar
Exhaust valve is
closed
Exploring rapid filling process of cylinder by air
3D CFD analysis of filling the cylinder process
1. Inlet pressures: 0.7 MPa, 0.9, 1.2MPa, 1.5MPa at 350K
2. Mass flowrate: 0.007 kg/s , 0.07 kg/s and 0.7 kg/s high mass flowrate at 350K
CEREEV TEAM
Air Spray: Rapid Filling of Cylinder of 80mm diameter
the nozzle has the diameter of 200 microns
CFD Simulation of Transonic Flow
Inlet Pressure Boundary Conditions
2D Axisymmetric mesh
Vortex ring formation for air injection via
nozzle of 200µ diameter at 18 bar fixed
inlet pressure
0.1ms 0.05ms 0.2ms
0.05ms 0.2ms
Pressure distribution (Pa)
Velocity magnitude (m·s-1)
Pressure distribution (Pa) Pressure distribution (Pa)
Velocity magnitude (m/s)
1
1.1
1.2
1.3
1.4
0 0.05 0.1 0.15 0.2 0.25 0.3Pre
ssu
re (
bar)
Time (ms)
In-cylinder pressure rate increases at 0.15 ms
Fixed inlet P = 15bar
In-Cylinder P = 20bar at 1ms
Choked flow (Ma > 1) for 18 bar fixed inlet pressure
Comparison in-cylinder gauge pressures vs time: red 1.8MPa and blue1MPa
0
0.5
1
1.5
2
0 0.5 1 1.5 2
Pre
ssu
re (
Pa)
Time (ms)
At 1ms 1.8MPa and 1MPa
have 0.9Pa and 0.5Pa in-
cylinder gauge pressures
respectively
Inlet duct travel time = 65mm /390m/s =
0.16ms
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 1 2 3 4 5
Pre
ss
ure
(M
Pa
)
Time(ms)
Inlet pressure (bar) ICP (bar)
7 5.5
9 7
10 8
12 9
15 11
RESULTS
2D:
Related Documents
