Sam Akehurst

Ultra Boost for Economy: Extending the Limits of Extreme Engine Downsizing

The paper discusses the concept, design and final results from the ‘Ultra Boost for Economy’ collaborative project, which was part-funded by the Technology Strategy Board, the UKs innovation agency. The project comprised industry- and academia-wide expertise to demonstrate that it is possible to reduce engine capacity by 60% and still achieve the torque curve of a modern, large-capacity naturally-aspirated engine, while encompassing the attributes necessary to employ such a concept in premium vehicles. In addition to achieving the torque curve of the Jaguar Land Rover naturally-aspirated 5.0 litre V8 engine (which included generating 25 bar BMEP at 1000 rpm), the main project target was to show that such a downsized engine could, in itself, provide a major proportion of a route towards a 35% reduction in vehicle tailpipe CO2 on the New European Drive Cycle, together with some vehicle-based modifications and the assumption of stop-start technology being used instead of hybridization. In order to do this vehicle modelling was employed to set part-load operating points representative of a target vehicle and to provide weighting factors for those points. The engine was sized by using the fuel consumption improvement targets and a series of specification steps designed to ensure that the required full-load performance and driveability could be achieved. The engine was designed in parallel with 1-D modelling which helped to combine the various technology packages of the project, including the specification of an advanced charging system and the provision of the necessary variability in the valvetrain system. An advanced intake port was designed in order to ensure the necessary flow rate and the charge motion to provide fuel mixing and help suppress knock, and was subjected to a full transient CFD analysis. A new engine management system was provided which necessarily had to be capable of controlling many functions, including a supercharger engagement clutch and full bypass system, direct injection system, port-fuel injection system, separately-switchable cam profiles for the intake and exhaust valves and wide-range fast-acting camshaft phasing devices. Testing of the engine was split into two phases. The first usied a test bed Combustion Air Handling Unit to enable development of the combustion system without the complication of a new charging system being fitted to the engine. To set boundary conditions during this part of the programme, heavy reliance was placed on the 1-D simulation. The second phase tested the full engine. The ramifications of realizing the engine design from a V8 basis in terms of residual friction versus the fuel consumption results achieved are also discussed. The final improvement in vehicle fuel economy is demonstrated using a proprietary fuel consumption code, and is presented for the New European Drive Cycle, the FTP-75 cycle and a 120 km/h (75 mph) cruise condition.

Development and Field Trial of a Driver Assistance System to Encourage Eco-Driving in Light Commercial Vehicle Fleets

Driver training schemes and eco-driving techniques can reduce fuel consumption by 10%, but their effectiveness depends on the willingness of drivers to change their behavior, and changes may be short lived. Onboard driver assistance systems have been proposed, which encourage driving style improvement. Such systems, when fitted in commercial vehicles, can assume some authority since uneconomical driving styles can be reported to a fleet manager. A driver assistance system has been developed and tried in the field with commercial vehicle drivers. The system aims to reduce fuel consumption by encouraging two behaviors: reduced rates of acceleration, and early upshifting through the gears. Visual feedback is reinforced with audible warnings when the driver makes uneconomical power demands of the engine. Field trials of the system were undertaken in the U.K. using 15 light commercial vehicles, driven by their professional drivers from a range of commercial applications. The trials consisted of two-week baseline data collection, which drivers were not aware of, followed by two weeks of data collection with the system being active. During the trials a total of 39 300 km of trip data were collected, which demonstrated fuel savings of up to 12% and average fuel savings of 7.6%.

Modelling of loss mechanisms in a pushing metal V-belt continuously variable transmission. Part 1: Torque losses due to band friction

Abstract The power transmission efficiency of continuously variable transmissions (CVTs) based on the pushing metal belt is acknowledged to be lower than that of discrete ratio alternatives. This tends to negate the potential fuel economy benefits that are obtained by improved engine/load matching with a CVT. This series of three papers details an investigation into the loss mechanisms that occur within the belt drive as a first step to obtaining improvements in efficiency. Experimental work has been undertaken to investigate the no-load and low-load torque losses associated with a pushing metal V-belt CVT. This first paper describes a new analysis of the principal torque losses occurring in the metal belt CVT due to relative motion occurring between the belt segments and bands. The work takes into account new findings in other research and changes in the design of the metal V-belt. The torque loss model proposed in this paper is supported by experimental data from several different test procedures. A number of additional torque loss mechanisms, due to pulley deflections, are described in Part 2 of the series. The findings from this current paper support an analysis of belt-slip losses, which is described in detail in Part 3.

Cooling system improvements — assessing the effects on emissions and fuel economy

Abstract The work reported in this paper details an experimental study of the effects of cooling system hardware changes on diesel engine emissions and fuel economy. Experiments were performed under both steady state and transient conditions and complemented by statistical assessments. Techniques for assessing the thermal integrity of the engine as a consequence of such changes are also presented. An experimental design was constructed to investigate the effect of water pump throttling, coolant flow control through the oil cooler, and the adoption of a pressure resistive thermostat (PRT). Use of these thermal controls offers a useful trade-off between NO x and fuel economy, with a saving of around 3 per cent in b.s.f.c. for a 10 per cent NO x penalty at low load, where NO x output is less of a concern. However, these benefits were not observed during drive cycle testing.

Octane appetite: The Relevance of a Lower Limit to the MON Specification in a Downsized, Highly Boosted DISI Engine

Market demand for high performance gasoline vehicles and increasingly strict government emissions regulations are driving the development of highly downsized, boosted direct injection engines. The in-cylinder temperatures and pressures of these emerging technologies tend to no longer adhere to the test conditions defining the RON and MON octane rating scales. This divergence between fuel knock rating methods and fuel performance in modern engines has previously led to the development of an engine and operating condition dependent scaling factor, K, which allows for extrapolation of RON and MON values. Downsized, boosted DISI engines have been generally shown to have negative K-values when knock limited, indicating a preference for fuels of higher sensitivity and challenging the relevance of a lower limit to the MON specification. The Ultraboost engine is an inline-4 downsized, highly boosted prototype DISI engine designed to achieve a 35% reduction in CO2 emissions whilst maintaining performance of a production V8. A series of 14 fuel formulations were tested to probe engine response to various fuel properties. This paper presents results from a 7 fuel RON and MON decorrelated matrix at four high-load engine conditions. The K-value was found to be negative at all engine conditions; fuels of higher sensitivity were found to yield improved engine performance. Furthermore, in-cylinder experimental data from high load knocking conditions with a single standard octane fuel were used to simulate the K-value; a similar trend between theory and experiment was observed.

Modelling of loss mechanisms in a pushing metal V-belt continuously variable transmission: Part 2: Pulley deflection losses and total torque loss validation:

Abstract The power transmission efficiency of continuously variable transmissions (CVTs) based on the pushing metal belt is acknowledged to be lower than that of discrete ratio alternatives. This tends to negate the potential fuel economy benefits that are obtained by improved engine/load matching with a CVT. This series of three papers details an investigation into the loss mechanisms that occur within the belt drive as a first step to obtaining improvements in efficiency. This second part follows on from an initial paper in which an analysis was performed of the losses that occur due to relative motion between the bands and segments of the belt. Additional experimental work has been performed indicating that a significant deflection occurs in the pulleys of the variator. Further torque-loss models are proposed in addition to that discussed in Part 1, representing a smaller but still significant torque loss associated with the belt. The work takes into account new findings in other research and changes in the design of the metal V-belt. The third paper in this series develops a number of models to predict belt-slip losses in the variator system, based on force distribution models developed in Part 1.

CVT Rolling Traction Drives—A Review of Research Into Their Design, Functionality, and Modeling

In this paper we detail a review of the current state of published work regarding the modeling of rolling traction drive Continuously Variable Transmissions (CVTs). An overview of CVTs operating by traction through small contact areas is performed, the layouts and kinematics of leading examples are reviewed, including the factors affecting design optimization. Properties of the traction contacts are considered in detail, with particular attention to elastohydrodynamic lubrication and asperity contact. Factors affecting the traction coefficient are reviewed and fundamental empirical predictions are contrasted with modern modeling computations. Finally measurements of the rheology of traction fluids are considered, leading to a definition of ideal properties and the development of proprietary fluids.

Modelling of loss mechanisms in a pushing metal V-belt continuously variable transmission. Part 3: belt slip losses

Abstract The power transmission efficiency of continuously variable transmissions (CVTs) based on the pushing metal belt is acknowledged to be lower than that of discrete ratio alternatives. This tends to negate the potential fuel economy benefits that are obtained by improved engine/load matching with a CVT. This series of three papers details an investigation into the loss mechanisms that occur within the belt drive as a first step to obtaining improvements in efficiency. This third paper follows on from two previous papers in which an analysis was performed modelling the torque losses that occur due to relative motion between the bands and segments of the belt, and between the pulleys and the belt due to pulley deflection effects. It describes additional experimental work, measuring the belt-slip speed tangentially about both of the pulleys in the variator. Additional loss models are proposed beyond those discussed in Parts 1 and 2 to describe the belt-slip phenomena, based on existing theory proposed by others. The analysis produced in this paper is validated against a range of experimental data and additionally through its close interaction with the torque-loss and torque-force distribution models proposed in Parts 1 and 2. The work takes into account new findings in other research and changes in the design of the current metal V-belt.

Octane Response in a Downsized, Highly Boosted Direct Injection Spark Ignition Engine

Increasingly strict government emissions regulations in combination with consumer demand for high performance vehicles is driving gasoline engine development towards highly downsized, boosted direct injection technologies. In these engines, fuel consumption is improved by reducing pumping, friction and heat losses, yet performance is maintained by operating at higher brake mean effective pressure. However, the in-cylinder conditions of these engines continue to diverge from traditional naturally aspirated technologies, and especially from the Cooperative Fuels Research engine used to define the octane rating scales. Engine concepts are thus key platforms with which to screen the influence of fundamental fuel properties on future engine performance. ‘ULTRABOOST’, a collaborative research project which is co-funded by the Technology Strategy Board (TSB), the UKs innovation agency, is a downsized, highly boosted, 2.0L in-line 4 cylinder prototype engine, designed to achieve 35% CO2 emissions reduction without compromising the performance of a 5.0L V8 naturally aspirated production engine. To probe engine response to fuel, a matrix of 14 formulations was tested at several engine conditions. This is the first in a series of fuel related papers and focuses on the engines response to the research octane number (RON). The knock limited spark advance was determined for a series of fuels with RON varying from 95 to 112; octane was shown to provide 5 or 10° crank angle advance in knock limited spark advance at 2000 and 3000 rpm, respectively. This study demonstrates that fuel octane quality continues to be important for the performance of emerging downsized engine technologies. Furthermore, the trend for continued engine downsizing will increase the potential performance benefit associated with knock resistant fuels.

Stochastic Dynamic Programming in the Real-World Control of Hybrid Electric Vehicles

Stochastic dynamic programming (SDP) is applied to the optimal control of a hybrid electric vehicle in a concerted attempt to deploy and evaluate such a controller in the real world. Practical considerations for robust implementation of the SDP algorithm are addressed, such as the choice of discount factor used and how charge sustaining characteristics of the SDP controller can be examined and adjusted. A novel cost function is used incorporating the square of battery charge (C-rate) as an indicator of electrical powertrain stress, with the aim of lessening the affliction of real-world concerns such as battery health and motor temperature, while allowing short spells of operation toward the system peak power limits where advantageous. This paper presents the simulation and chassis dynamometer results over the LA92 drive cycle, as well as the results of testing on open roads. The hybrid system is operated at several levels of aggressivity, allowing the tradeoff between fuel savings and electrical powertrain stress to be evaluated. In dynamometer testing, this approach yielded a 13% reduction in electrical powertrain stress without sacrificing any fuel savings, compared with a controller that does not consider aggressivity in its optimization.