Optical Diagnostics of Mixture Preparation in GDI Engines

Lead Research Organisation: University of Oxford
Department Name: Engineering Science

Abstract

The aim of this project is to better understand the complex processes of mixture preparation in gasoline direct injection (GDI) engines. In recent decades, there has been a drive to combine the advantages of gasoline and diesel engines due to the introduction of increasingly stringent emissions legislation and the threat of climate change. GDI engines have the potential to achieve this goal by delivering the high specific output of a gasoline engine with the fuel economy of a diesel engine. However, as fuel is injected directly into the cylinder at high pressure (>150 bar), there is an increased likelihood of impingement of fuel on the piston and cylinder walls, which leads to increased emissions. Further investigation into the preparation of the fuel-air mixture is necessary in order to maximise the potential benefits of GDI engines.

A new optical engine, provided by Jaguar Land Rover, is based on the new JLR AJ200 combustion system. The new engine provides many features that greatly increase the flexibility of experiments when compared to previous designs of optical engine. A new support structure allows greater access to the combustion chamber and a new design of cylinder liner provides uninterrupted views of the spark plug and fuel injector. The engine also offers variable valve timing and continuous control of valve lift is planned.

A combination of laser techniques will be used to measure calibrated 2D in-cylinder temperature maps with high precision. Laser Induced Thermal Grating Spectroscopy (LITGS) is a point-wise temperature measurement technique developed for use in optical engines by members of the Oxford Physics Departments. This technique can achieve greater accuracy than similar laser-based techniques and will be used to calibrate 2D in-cylinder temperature maps captured with Two-Colour Planar Laser Induced Fluorescence (TC-PLIF). Data from these experiments will be valuable for modelling in terms of validation. The precision of the LITGS technique allows quantification of the charge cooling effect due to direct injection. It will be used to investigate the effect of various fuel components, including alcohols, on the reduction of charge temperature due to direct injection.

In the near future, a high-speed Particle Image Velocimetry (PIV) system will be installed and commissioned on the engine. This will allow the measurement of in-cylinder flowfields resolved on a crank-angle basis. This technique will be used in combination with spray and flame imaging to investigate fuel-air mixture preparation for various fuels and the consequent effect on emissions.

This project falls within the EPSRC Energy Efficiency Research Area.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509310/1 01/10/2015 30/09/2020
1658694 Studentship EP/N509310/1 01/10/2015 31/03/2019 Michael Blane Scott
 
Description This research has focused on producing high-quality experimental data that can be used to validate CFD models used by commercial partners, Jaguar Land Rover. Specifically, this research has focussed on investigating mixture preparation in a firing optical GDI engine. Planar, temperature fields measured using Two-Colour Planar Laser Induced Fluorescence (TC-PLIF) were calibrated in-situ using Laser Induced Thermal Grating Spectroscopy (LITGS). The results from this work have been published in the SAE International Journal of Engines in 2017 (Scott, B., Willman, C., Williams, B., Ewart, P. et al., "In-Cylinder Temperature Measurements Using Laser Induced Grating Spectroscopy and Two-Colour PLIF," SAE Int. J. Engines 10(4):2191-2201, 2017, https://doi.org/10.4271/2017-24-0045.)
More recently, a high-speed PIV system has been installed to investigate in-cylinder fluid flow and its subsequent effect on mixture formation and combustion. Novel techniques have been developed to quantify the differences between in-cylinder velocity fields, which have been used to quantify the differences between engine simulations and experimental results to aid the validation of numerical models. Flow field measurements have also been made under fired operation in an optical GDI engine. The objective is to use the newly developed methods to identify flow features that influence combustion to aid the development of future combustion systems.
Exploitation Route The code required to compare flow fields will be made available to Jaguar Land Rover, who can use it to analyse simulated flow fields produced by numerical simulations. These tools are not specific to internal combustion engines, but any vector fields that are to be compared and may be of use in industries other than automotive, particularly aerospace.
Sectors Energy,Transport

URL https://doi.org/10.4271/2017-24-0045
 
Description The optical engine design is based on Jaguar Land Rover's new production combustion system, the Ingenium. Therefore, all the results produced by the optical engine are used to aid the design of the new generation of Jaguar Land Rover engines. It has a fully variable valve train on the inlet to match the production engines, which will allow the flow motion induced by advanced valve strategies to be investigated. The data produced by the engine will be used to validate simulations produced by Jaguar Land Rover's Computational Fluid Dynamics (CFD) team.
First Year Of Impact 2017
Sector Energy,Transport
Impact Types Economic