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Technical Paper

Predicted Paths of Soot Particles in the Cylinders of a Direct Injection Diesel Engine

2012-04-16
2012-01-0148
Soot formation and distribution inside the cylinder of a light-duty direct injection diesel engine, have been predicted using Kiva-3v CFD software. Pathlines of soot particles traced from specific in-cylinder locations and crank angle instants have been explored using the results for cylinder charge motion predicted by the Kiva-3v code. Pathlines are determined assuming soot particles are massless and follow charge motion. Coagulation and agglomeration have not been taken into account. High rates of soot formation dominate during and just after the injection. Oxidation becomes dominant after the injection has terminated and throughout the power stroke. Computed soot pathlines show that soot particles formed just below the fuel spray axis during the early injection period are more likely to travel to the cylinder wall boundary layer. Soot particles above the fuel spray have lesser tendency to be conveyed to the cylinder wall.
Technical Paper

Review of Reconfigurable Assembly Systems Technologies for Cost Effective Wing Structure Assembly

2013-09-17
2013-01-2336
Airbus commercial wings are assembled manually in dedicated steel structures. The lead time to design, manufacture and commission these fixtures is often in excess of 24 months. Due to the nature of these fixtures, manufacturing is slow in responding to changes in demand. There is underused capacity in some areas and insufficient ramp-up speed where increased production rate is needed. Reconfigurable Manufacturing Systems and Reconfigurable Assembly Systems (RAS) provide an approach to system design that provides appropriate capacity when needed. The aim of the paper is to review RAS technologies that are suitable for cost-effective wing structure assembly and what knowledge gaps exist for a RAS to be achieved. The paper examines successful cases of RAS and reviews relevant system design approaches. Cost savings are acknowledged and tabularised where demonstrated in research. The research gaps to realising a RAS for wing assembly are identified and different approaches are considered.
Technical Paper

Low Cost Reconfigurable Jig Tooling and In-Process Metrology for High Accuracy Prototype Rotorcraft Wing Assembly

2019-09-16
2019-01-1877
Reconfigurable tooling frames consisting of steel box sections and bolted friction clamps offer an opportunity to replace traditional expensive welded steel tooling. This well publicized reconfigurable reusable jig tooling has been investigated for use in the assembly of a prototype compound helicopter wing. Due to the aircraft configuration, the wing design is pinned at both ends and therefore requires a higher degree of end to end accuracy, over the 4m length, than conventional wings. During the investigation some fundamental issues are approached, including: Potential cost savings and variables which effect the business case. Achievable Jig accuracy. Potential sources of instability that may affect accuracy over time. Repeatability of measurements with various features and methods. Typical jig stability over 24hrs including effects of small temperature fluctuations. Deflections that occur due to loading.
Technical Paper

Advanced Assembly Solutions for the Airbus RACER Joined-Wing Configuration

2019-09-16
2019-01-1884
The Rapid And Cost Effective Rotorcraft (RACER) is being developed by Airbus Helicopters (AH) to demonstrate a new Vertical Take-Off and Landing configuration to fill the mobility gap between conventional helicopters and aeroplanes. RACER is a compound rotorcraft featuring wings and multiple rotors. The wing arrangement suggested by AH is defined as a staggered bi-plane joined configuration with an upper and a lower straight wing, either side of the fuselage, connected at their outboard extent to form a triangular structure. The ASTRAL consortium, consisting of the University of Nottingham and GE Aviation Systems, are responsible for the design, manufacture, assembly and testing of the wings. Producing an optimised strategy to assemble a joined-wing configuration for a passenger carrying rotorcraft is challenging and novel. The objective of this work concerns all aspects of assembling the joined-wing structure.
Technical Paper

Morphological Characterisation of Diesel Soot in Oil and the Associated Extraction Dependence

2018-04-03
2018-01-0935
The size and morphology of soot particles and agglomerates extracted from lubricating oil drawn from the sump of a diesel engine have been investigated and compared using Transmission Electron Microscopy (TEM) and Nanoparticle Tracking Analysis (NTA). Samples were prepared for electron microscopy imaging by both centrifugation and solvent extraction to investigate the impact of these procedures on the morphological characteristics, such as skeleton length and width and circularity, of the obtained soot. It was shown that centrifugation increases the extent of agglomeration within the sample, with 15% of the agglomerates above 200 nm compared to only 11% in the solvent extracted soot. It was also observed that the width of centrifugation extracted soot was typically 10 nm to 20 nm larger than that of solvent extracted soot, suggesting that centrifugation forces the individual agglomerate chains together.
Technical Paper

Soot in the Lubricating Oil: An Overlooked Concern for the Gasoline Direct Injection Engine?

2019-04-02
2019-01-0301
Formation of soot is a known phenomenon for diesel engines, however, only recently emerged for gasoline engines with the introduction of direct injection systems. Soot-in-oil samples from a three-cylinder turbocharged gasoline direct injection (GDI) engine have been analysed. The samples were collected from the oil sump after periods of use in predominantly urban driving conditions with start-stop mode activated. Thermogravimetric analysis (TGA) was performed to measure the soot content in the drained oils. Soot deposition rates were similar to previously reported rates for diesel engines, i.e. 1 wt% per 15,000 km, thus indicating a similar importance. Morphology was assessed by transmission electron microscopy (TEM). Images showed fractal agglomerates comprising multiple primary particles with characteristic core-shell nanostructure. Furthermore, large amorphous structures were observed. Primary particle sizes ranged from 12 to 55 nm, with a mean diameter of 30 nm and mode at 31 nm.
Technical Paper

Demonstration of Transformable Manufacturing Systems through the Evolvable Assembly Systems Project

2019-03-19
2019-01-1363
Evolvable Assembly Systems is a five year UK research council funded project into flexible and reconfigurable manufacturing systems. The principal goal of the research programme has been to define and validate the vision and support architecture, theoretical models, methods and algorithms for Evolvable Assembly Systems as a new platform for open, adaptable, context-aware and cost effective production. The project is now coming to a close; the concepts developed during the project have been implemented on a variety of demonstrators across a number of manufacturing domains including automotive and aerospace assembly. This paper will show the progression of demonstrators and applications as they increase in complexity, specifically focussing on the Future Automated Aerospace Assembly Phase 1 technology demonstrator (FA3D).
Technical Paper

Investigating the Effect of Carbon Nanoparticles on the Viscosity of Lubricant Oil from Light Duty Automotive Diesel Engines

2014-04-01
2014-01-1481
The influence of size and concentration of carbon nanoparticle on the viscosity of an SAE 5W-30 lubricant oil has been investigated experimentally. Data were collected for oil samples drawn from sump of light duty automotive diesel engines. The average size of soot particles in the used oil samples was in the range of 180-320nm with concentrations ranging from 0 to 2 percentage by weight (wt. %.). A Brookfield DV-II Pro rotary viscometer was used to measure dynamic viscosity at low shear rates and temperatures of 40°C and 90°C. Nanoparticle concentration and particle size distribution were evaluated using Thermo-Gravimetric Analysis (TGA) and Dynamic Light Scattering (DLS) respectively. The viscosity of suspensions of graphite powder in lubricant oil was also investigated for concentrations ranging from 0 to 2 wt. %. The results show that dynamic viscosity increases with increasing soot content and decreasing temperature.
Journal Article

The Effect of Reducing Compression Ratio on the Work Output and Heat Release Characteristics of a DI Diesel under Cold Start Conditions

2008-04-14
2008-01-1306
An experimental investigation has been carried out to compare the indicated performance and heat release characteristics of a DI diesel engine at compression ratios of 18.4:1 and 15.4:1. The compression ratio was changed by modifying the piston bowl volume; the bore and stroke were unchanged, and the swept volume was nominally 500cc. The engine is a single cylinder variant of modern design which meets Euro 4 emissions requirements. Work output and heat release characteristics for the two compression ratios have been compared at an engine speed of 300 rev/min and test temperatures of 10, -10 and -20°C. A more limited comparison has also been made for higher speeds representative of cold idle at one test temperature (-20°C). The reduction in compression ratio generally produces an increase in peak specific indicated work output at low speeds; this is attributable to a reduction in blowby and heat transfer losses and lower peak rates of heat release increasing cumulative burn.
Journal Article

Flexible Tooling for Wing Box Rib Clamping and Drilling

2011-10-18
2011-01-2639
Currently the wing box rib assembly process requires the manual location and temporary fixing of components within product specific jig or fixtures for drilling. After drilling and reaming, parts are separated, cleaned, deburred prior to adding sealant, reclaiming and final bolting, but this may significantly increase cost, manufacturing lead-time, reduces flexibility and cannot usually be economically modified for use on other aircraft types. Due to potential increase in demand for the next generation single isle aircraft, existing tooling solutions have to be improved and new technologies have to be developed. This paper describes the development and testing of flexible tooling to provide clamping and support for drilling wing box ribs to mating rib posts within a restricted environment. Results are presented along with a discussion of the problems that may be encountered during clamping trials.
Technical Paper

CFD Investigation on the Influence of In-Cylinder Mixture Distribution from Multiple Pilot Injections on Cold Idle Behaviour of a Light Duty Diesel Engine

2014-10-13
2014-01-2708
Cold idle operation of a modern design light duty diesel engine and the effect of multiple pilot injections on stability were investigated. The investigation was initially carried out experimentally at 1000rpm and at −20°C. Benefits of mixture preparation were initially explored by a heat release analysis. Kiva 3v was then used to model the effect of multiple pilots on in-cylinder mixture distribution. A 60° sector of mesh was used taking advantage of rotational symmetry. The combustion system and injector arrangements mimic the HPCR diesel engine used in the experimental investigation. The CFD analysis covers evolutions from intake valve closing to start of combustion. The number of injections was varied from 1 to 4, but the total fuel injected was kept constant at 17mm3/stroke. Start of main injection timing was fixed at 7.5°BTDC.
Technical Paper

A Modified Oil Lubrication System with Flow Control to Reduce Crankshaft Bearing Friction in a Litre 4 Cylinder Diesel Engine

2016-04-05
2016-01-1045
The oil distribution system of an automotive light duty engine typically has an oil pump mechanically driven through the front-endancillaries-drive or directly off the crankshaft. Delivery pressure is regulated by a relief valve to provide an oil gallery pressure of typically 3 to 4 bar absolute at fully-warm engine running conditions. Electrification of the oil pump drive is one way to decouple pump delivery from engine speed, but this does not alter the flow distribution between parts of the engine requiring lubrication. Here, the behaviour and benefits of a system with an electrically driven, fixed displacement pump and a distributor providing control over flow to crankshaft main bearings and big end bearings is examined. The aim has been to demonstrate that by controlling flow to these bearings, without changing flow to other parts of the engine, significant reductions in engine friction can be achieved.
Technical Paper

Design of a Reconfigurable Assembly Cell for Multiple Aerostructures

2016-09-27
2016-01-2105
This paper presents novel development of a reconfigurable assembly cell which assembles multiple aerostructure products. Most aerostructure assembly systems are designed to produce one variant only. For multiple variants, each assembly typically has a dedicated assembly cell, despite most assemblies requiring a process of drilling and fastening to similar tolerances. Assembly systems that produce more than one variant do exist but have long changeover or involve extensive retrofitting. Quick assembly of multiple products using one assembly system offers significant cost savings from reductions in capital expenditure and lead time. Recent trends advocate Reconfigurable Assembly Systems (RAS) as a solution; designed to have exactly the functionality necessary to produce a group of similar components. A state-of-the-art review finds significant benefits in deploying RAS for a group of aerostructures variants.
Technical Paper

Variation Aware Assembly Systems for Aircraft Wings

2016-09-27
2016-01-2106
Aircraft manufacturers desire to increase production to keep up with anticipated demand. To achieve this, the aerospace industry requires a significant increase in the manufacturing and assembly performance to reach required output levels. This work therefore introduces the Variation Aware Assembly (VAA) concept and identifies its suitability for implementation into aircraft wing assembly processes. The VAA system concept focuses on achieving assemblies towards the nominal dimensions, as opposed to traditional tooling methods that aim to achieve assemblies anywhere within the tolerance band. It enables control of the variation found in Key Characteristics (KC) that will allow for an increase in the assembly quality and product performance. The concept consists of utilizing metrology data from sources both before and during the assembly process, to precisely position parts using motion controllers.
Technical Paper

Light Weight Aerospace Assembly Fixture

2015-09-15
2015-01-2496
There is the need to strive towards more advanced aircraft with the use of materials such as composites, and a desire to improve efficiency by achieving and maintaining laminar flow over a large proportion of the aircraft wing. Due to the high tolerances required to achieve laminar flow, the manufacturing processes and tooling will have to be revaluated to enable successful manufacture in a production environment. A major influence in achieving the key characteristics and tolerances is the assembly fixture. This paper details the design and manufacture of a carbon fibre based assembly fixture, required for a one-off build of an innovative leading edge wing concept. The fixture has been designed and optimised in order to make it adaptable, reconfigurable, and suitable for lifting as well as being thermally stable whilst maintaining laminar flow tolerances.
Technical Paper

Towards Self-Adaptive Fixturing Systems for Aircraft Wing Assembly

2015-09-15
2015-01-2493
The aim of this work was to develop a new assembly process in conjunction with an adaptive fixturing system to improve the assembly process capability of specific aircraft wing assembly processes. The inherently complex aerospace industry requires a step change in its capability to achieve the production ramp up required to meet the global demand. This paper evaluates the capability of adaptive fixtures to identify their suitability for implementation into aircraft wing manufacturing and assembly. To understand the potential benefits of these fixtures, an examination of the current academic practices and an evaluation of the existing industrial solutions is highlighted. The proposed adaptive assembly process was developed to account for the manufacturing induced dimensional variation that causes significant issues in aircraft wing assembly. To test the effectiveness of the adaptive assembly process, an aircraft wing assembly operation was replicated on a demonstrator test rig.
Journal Article

A Novel Diagnostics Tool for Measuring Soot Agglomerates Size Distribution in Used Automotive Lubricant Oils

2014-04-01
2014-01-1479
The determination of size distribution of soot particles and agglomerates in oil samples using a Nanosight LM14 to perform Nanoparticle Tracking Analysis (NTA) is described. This is the first application of the technique to sizing soot-in-oil agglomerates and offers the advantages of relatively high rates of sample analysis and low cost compared to Transmission Electron Microscopy (TEM). Lubricating oil samples were drawn from the sump of automotive diesel engines run under a mix of light duty operating conditions. The oil samples were diluted with heptane before analysing. Results from NTA analysis were compared with the outputs of a more conventional analysis based on Dynamic Light Scattering (DLS). This work shows that soot-in-oil exists as agglomerates with average size of 115 nm. This is also in good agreement with TEM analysis carried out in a previous work. NTA can measure soot particles in polydisperse oil solutions and report the size distribution of soot-in-oil aggregates.
Journal Article

Emerging Technologies for Use in Aerospace Bonded Assemblies

2013-09-17
2013-01-2134
Several new technologies are now emerging to improve adhesive supply and formulation along with surface treatments that have the potential to offer significant improvements to both surface energy and cleanliness [3]. Additionally, the miniaturisation of laboratory techniques into portable equipment offers potential for online surface energy and chemical analysis measurement for use as quality control measures in a production environment. An overview of newly available technology is given here with several devices studied in further detail. Technologies assessed further in this paper are; portable surface contact angle measurement, ambient pressure plasma cleaning, portable FTIR measurement and adhesive mixing equipment. A number of potential applications are outlined for each device based on the operational technique. The practical aspects of implementation and the perceived technology readiness levels for operation, implementation and results are also given.
Journal Article

The Effect of Piston Cooling Jets on Diesel Engine Piston Temperatures, Emissions and Fuel Consumption

2012-04-16
2012-01-1212
A Ford 2.4-liter 115PS light-duty diesel engine was modified to allow solenoid control of the oil feed to the piston cooling jets, enabling these to be switched on or off on demand. The influence of the jets on piston temperatures, engine thermal state, gaseous emissions and fuel economy has been investigated. With the jets switched off, piston temperatures were measured to be between 23 and 88°C higher. Across a range of speed-load points, switching off the jets increased engine-out emissions of NOx typically by 3%, and reduced emissions of CO by 5-10%. Changes in HC were of the same order and were reductions at most conditions. Fuel consumption increased at low-speed, high-load conditions and decreased at high-speed, low-load conditions. Applying the results to the NEDC drive cycle suggests active on/off control of the jets could reduce engine-out emissions of CO by 6%, at the expense of a 1% increase in NOx, compared to the case when the jets are on continuously.
Journal Article

Investigating the Potential to Reduce Crankshaft Main Bearing Friction During Engine Warm-up by Raising Oil Feed Temperature

2012-04-16
2012-01-1216
Reducing friction in crankshaft bearings during cold engine operation by heating the oil supply to the main gallery has been investigated through experimental investigations and computational modelling. The experimental work was undertaken on a 2.4l DI diesel engine set up with an external heat source to supply hot oil to the gallery. The aim was to raise the film temperature in the main bearings early in the warm up, producing a reduction in oil viscosity and through this, a reduction in friction losses. The effectiveness of this approach depends on the management of heat losses from the oil. Heat transfer along the oil pathway to the bearings, and within the bearings to the journals and shells, reduces the benefit of the upstream heating.
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