Optical Techniques in Gasoline Engine Performance and Emissions Development Injector Spray Visualisation

Transcription

1 Injector Spray Visualisation Denis Gill, Wolfgang Krankenedl, DEC Ernst Winklhofer

2 Emissions Development Injector Spray Visualisation Contents Introduction Spray Box Direct Injection (GDI) Spray Visualization Penetration, Spray Angle, Bend Angle Patternator (Spray Distribution) Drop Sizing (Malvern) Injector Dribble

3 Emissions Development Injector Spray Visualisation Introduction Direct gasoline injection engines rely on their spray direction and formation for good mixing. Using video techniques into spray boxes, the spray form and movement can be assessed, allowing injectors to be compared and their properties analysed.

4 Spray Chamber - Description Results: Overall Structure Spray Quality Spray Develoment After injections Boundary Conditions Rail pressure: Variable - up to 500bar Chamber pressure: Variable - from 0.3 to 11bar abs. Test fuel: n - Heptan Test fuel temperature: 20 C Temperature in chamber: Ambient (approx. 20 C) not variable Injection duration: Variable Size of observation window : 180*180*180 mm. View: Set-Up Front and side Compressed Air / Nitrogen Cross Sectional View Fuel Supply Scavenging Air Inlet Injector Flow Straightener Fuel Supply Injector Mounting Quartz Windows Air Carbon Filter Observation Chamber Vacuum Pump Bypass Valve Throttle Valve Observation Area Fuel Water Water

5 Digital Video System Experimental Setup for GDI Spray Analysis Injector Spray Observation Chamber Stroboscope Stroboscope Light Unit Digital CCD- Camera VisioScope Digital Engine Video System

6 Emissions Development Injector Spray Visualisation Spray Observation Chamber

7 Emissions Development Injector Spray Visualisation Spray Observation Chamber

8 Emissions Development Injector Spray Visualisation Contents Introduction Spray Box Direct Injection (GDI) Spray Visualization Penetration, Spray Angle, Bend Angle Patternator (Spray Distribution) Drop Sizing (Malvern) Injector Dribble

9 Optical Techniques in Gasoline Engine Performance and GDI Injectors Connector below

10 Spray Visualisation Fuel Pressure: 200bar; Pulse Duration: 1.5ms Connector - rear Connector - left

11 Injector Spray Visualisation 0.2ms 100bar; 1.5ms 0.2ms 0.5ms 0.5ms connector behind connector right

12 Optical Techniques in Gasoline Engine Performance and Injector Spray Visualisation 1.0ms 1.5ms connector behind 100bar; 1.5ms 1.0ms 1.5ms connector right

13 Injector Spray Visualisation 2.0ms 100bar; 1.5ms 2.0ms

14 Optical Techniques in Gasoline Engine Performance and Injector Spray Visualisation AVL Visioscope Software Software allowing to visualize, post-process and export recorded data. 100% In-House development. Extended library of image post-processing functions (see below) Automatic assessment of penetration, spray angle, bend angle Results: Spray Penetration Spray Stability/Repeatability Example of results obtained thanks to AVL visioscope software Colour invert Trace iso-line Overlay Image Probablity Distribution

15 Injector Spray Visualisation Averaged Pictures

16 Injector Spray Visualisation Statistical Distribution of Fuel Concentration in %

17 Injector Spray Visualisation Definition of Spray Geometry Characteristic Numbers Spray Angle Bend Angle Axial Penetration Lateral extension

18 Injector Spray Visualisation View 1 View 2 Penetration Penetration [mm] CA [deg]

19 Injector Spray Visualisation Spray Angle View 1 View Spray Angle [deg] CA [deg]

20 Injector Spray Visualisation Bend Angle View 1 View Bend Angle [deg] CA [deg]

21 Emissions Development Injector Spray Visualisation Contents Introduction Spray Box Direct Injection (GDI) Spray Visualization Penetration, Spray Angle, Bend Angle Patternator (Spray Distribution) Drop Sizing (Malvern) Injector Dribble

22 Optical Techniques in Gasoline Engine Performance and Patternator Low resolution mechanical patternator Results: Spray Pattern Spray Angles SAE2715 does not recommend the use of a mechanical patternator for DI injector. 61 pipes 4 mm y [mm] x [mm] y [mm] x [mm] Relativ Mass [%] y [mm] x [mm]

23 Patternator Testing Conditions and Mass capture efficiency 20 mm distance between injector tip and patternator (Open pipes ends). 500 injections (100 bar fuel pressure into ambient at 1.5 ms PW) were performed corresponding to 60s measuring time and 120 ms injection period. At PW = 1.5ms and 100 bar fuel pressure, the dynamic flow is 9.24 mg/inj (see slide 16). This leads to a total injected mass of 4.62g. The sum of the masses found in the pipes of the patternator equal 2.33g. The mass capture efficiency is therefore approx. equal to 50%.

24 Patternator The table below shows the settings investigated : Measurement Program Absolute Back-Pressure [bar] Pulse widths Absolute Fuel Pressure [bar] ms Work Scope : Installation of injector in spray chamber with high resolution mechanical mass patternator and verification of alignment. For the settings mentioned in the table below performance of a number of injection allowing the collection of a significant amount of fuel in each of the 61 tubes of the AVL high resolution mechanical mass patternator Weighing the amount of fuel in each tube. Post-processing. Deliverables : Fuel mass distribution and mass capture efficiency

25 Optical Techniques in Gasoline Engine Performance and Patternator Relativ Mass [%] y [mm] x [mm]

26 Patternator Views definition y [mm] View x [mm] View 1

27 Optical Techniques in Gasoline Engine Performance and Patternator

28 Emissions Development Injector Spray Visualisation Contents Introduction Spray Box Direct Injection (GDI) Spray Visualization Penetration, Spray Angle, Bend Angle Patternator (Spray Distribution) Drop Sizing (Malvern) Injector Dribble

29 Measurement Equipment - Malvern Spraytec STP2000 Results Drop size distribution Characteristic diameters Time history of characteristic diameters Example of results Laser Beam expansion Receiver Detection System Size range Measurement triggering Acquisition Rate Main characteristics 2 mw Helium-Neon laser (wave length 633 nm) 10 mm Fourier transformer lens f = 300 mm 36 element log-spaced silicon diode detector array µm for 300 mm lens External Based on TTL input 10kHz Experimental set-up Fuel Injector Π Title Average Min Max Trans (%) Dv(10) (µm) Dv(50) (µm) Dv(90) (µm) Variation of the Injector Position He-Ne Laser Laser Beam ø 10 mm Measuring volume Receiver Lens Detector Array Meas. Electr. Computer Monitor Air Carbon Filter Device Vacuum Pump Bypass Valve Throttle Valve Fuel Water Water

30 Measurement Equipment - Malvern Spraytec STP

31 Measurement Equipment - Malvern Spraytec STP2000 Measuring Principle (Source SAEJ2715)

32 Injector Variant Investigations Physical and Chemical Characteristics of n-heptane Value / Region Unit Method Density (15 C) g/cm³ DIN Viscosity, kinematic (20 C) mm²/s ISO 3104 Surface tension (25 C) 19.7 mn/m Wilhelmy Plate Vapour Pressure (25 C) 6.1 kpa Calculated (CONCAWE 2010a) Boiling Point C ASTM D1078 Ignition Temperature 204 C According to Lide (2005) Melting Point < -20 C Flame Point - 4 C According to Lide (2005) Solubilty in Water (25 C) 2.5 mg/l According to Lide (2005) Distribution Coefficient in n-octanol / Wasser 4.5 log pow According to Lide (2005) Droplet size measurements, based in the principle of light scattering in the forward direction contain the risk of adulteration caused by fuel vapourisation. Therefore, n- Heptan, which does not vapourise significantly, is used as test fluid.

33 Measurement Programme The box below shows an abstract of the binding commercial offer. The table below shows the different settings investigated :

34 Drop Size Distribution - Time History - 1 Results Description and Correlation to Spray Chamber Imaging Pfuel = 100 bar, PW = 1.5 ms, Z = 30 and 50 mm SOL SOF (~ 1.6 CA / 0.25 ms) EOF Fuel covers LD beam (Z = CA / 0.8 ms) Fuel covers LD beam (Z = CA / 1.2 ms) Transmission [%] Time [ms] CA [deg] Transmission Z = 30 mm Transmission Z = 50 mm N = 1000rpm Min Trans at Z = 30 mm (Z = 30 ~ 12 CA / 2 ms) Min Trans at Z = 50 mm (Z = 50 ~ 14.4 CA / 2.4 ms)

35 Result Values Generated: D (0,1) ; Dv(10) 10% of the measured droplet volume has a diameter below this value D (0,5) ; Dv(50) This is the average diameter of the droplets measured. i.e. 50% of the total volume is made up of droplets smaller than this value and 50% are larger. D (0,9) ; Dv (90) 90% of the measured droplet volume has a diameter less than this value. D (3,2); SMD This is a means of expressing the spray in terms of surface area produced by the spray. It is the size of a drop having the same surface area to volume ratio as all the total volume of all the drops to the total surface area of all the drops

36 Drop Size Distribution cycle by cycle

37 Drop Size Distribution average

38 Drop Size Distribution average

39 Emissions Development Injector Spray Visualisation Contents Introduction Spray Box Direct Injection (GDI) Spray Visualization Penetration, Spray Angle, Bend Angle Patternator (Spray Distribution) Drop Sizing (Malvern) Injector Dribble

40 Injector Spray Visualisation Split Injection - Close Up

41 Spray Chamber Visualizations Injector Tip

42 Overview Spray Characterization and Flow Characteristics Summary For Gasoline direct injection, the quality and form of the spray is important for the mixture formation. By means of optical techniques such as spray visualisation and laser diffraction, we can assess the quality of an injector before engine test, and ensure that the injector is suitable for its intended purpose. The results of these tests can be used to support both CFD modelling and the glass engine development work.

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