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We present a new method to predict the power losses in electric vehicle (EV) transmission systems using a thermally coupled gearbox efficiency model. Friction losses in gear teeth contacts are predicted using an iterative procedure to account for the thermal coupling between the tooth temperature, oil viscosity, film thickness, friction, and oil rheology during a gear mesh cycle. Crucially, the prediction of the evolution of the coefficient of friction (COF) along the path of contact incorporates measured lubricant rheological parameters as well as measured boundary friction. This allows the model to differentiate between nominally similar lubricants in terms of their impact on EV transmission efficiency. Bearing and gear churning losses are predicted using existing empirical relationships. The effects of EV motor cooling and heat transfers in the heat exchanger on oil temperature are considered.

In the present study, Large Eddy Simulations (LES) have been performed with a 3D model of a step nozzle injector, using n-pentane as the injected fluid, a representative of the high-volatility components in gasoline. The influence of fuel temperature and injection pressure were investigated in conditions that shed light on engine cold-start, a phenomenon prevalent in a number of combustion applications, albeit not extensively studied. The test cases provide an impression of the in-nozzle phase change and the near-nozzle spray structure across different cavitation regimes. Results for the 20oC fuel temperature case (supercavitating regime) depict the formation of a continuous cavitation region that extends to the nozzle outlet. Collapse-induced pressure wave dynamics near the outlet cause a transient entrainment of air from the discharge chamber towards the nozzle.

Following market demands for a niche balance between engine performance and legislation requirement, a new-concept compressor scroll has been designed for small to medium size passenger cars. The design adopts a slight deviation from the conventional method, thus resulting in broader surge margin and better efficiency at off-design region. This paper presents the performance evaluation of the new compressor scroll on the cold-flow gas-stand followed by the on-engine testing. The testing program focused on back-to-back comparison with the standard compressor scroll, as well as identifying on-engine operational regime with better brake specific fuel consumption (BSFC) and transient performance. A specially instrumented 1.6L gasoline engine was used for this study. The engine control unit configuration is kept constant in both the compressor testing.

Future CO2 emission legislation requires the internal combustion engine to become more efficient than ever. Of great importance is the boosting system enabling down-sizing and down-speeding. However, the thermodynamic coupling of a reciprocating internal combustion engine and a turbocharger poses a great challenge to the turbine as pulsating admission conditions are imposed onto the turbocharger turbine. This paper presents a novel approach to a turbocharger turbine development process and outlines this process using the example of an asymmetric twin scroll turbocharger applied to a heavy duty truck engine application. In a first step, relevant operating points are defined taking into account fuel consumption on reference routes for the target application. These operation points are transferred into transient boundary conditions imposed on the turbine.

The present work investigates the effect of fuel injection timing on combustion stratification and soot formation in an optically accessible, single cylinder light duty diesel engine. The engine operated under low load and low engine speed conditions, employing a single injection scheme. The conducted experiments considered three different injection timings, which promoted Partially Premixed Combustion (PPC) operation. The fuel quantity of the main injection was adjusted to maintain the same Indicated Mean Effective Pressure (IMEP) value among all cases considered. Findings were analysed via means of pressure trace and apparent heat transfer rate (AHTR) analyses, as well as a series of optical diagnostics techniques, namely flame natural luminosity, CH* and C2* chemiluminescence high-speed imaging, as well as planar Laser Induced Incandescence (pLII).

For the investigation of the tribological behavior of lubricated contacts, the choice and the calibration of the adopted asperity contact model is fundamental, in order to properly mimic the mixed lubrication conditions. The Greenwood/Tripp model is extensively adopted by the commercial software commonly employed to simulate lubricated contacts. This model, based on a statistic evaluation of the number of asperities in contact and on the Hertzian contact theory, has the advantage of introducing a simple relationship between oil film thickness and asperity contact pressure, considerably reducing the simulation time. However, in order to calibrate the model, some non-standard roughness parameters are required, that are not available from commercial roughness measuring equipment. Standard values, based on some limited experiences, are typically used, and a limited literature can be found focusing on how to evaluate them, thus reducing the predictivity of the model.

The use of twin-scroll turbocharger turbine in automotive powertrain has been known for providing better transient performance over conventional single-scroll turbine. This has been accredited to the preservation of exhaust flow energy in the twin-scroll volute. In the current study, the performance comparison between a single and twin-scroll turbine has been made experimentally on a 1.5L passenger car gasoline engine. The uniqueness of the current study is that nearly identical engine hardware has been used for both the single and twin-scroll turbine volutes. This includes the intake and exhaust manifold geometry, turbocharger compressor, turbine rotor and volute scroll A/R variation trend over circumferential location. On top of that, the steady-state engine performance with both the volutes, has also been tuned to have matching brake torque.

Bearings represent one of the main causes of friction losses in internal combustion engines, and their lubrication performance has a crucial influence on the operating condition of the engine. In particular, the conrod small-end bearing is one of the most critical engine parts from a tribological point of view since limited contact surfaces have to support high inertial and combustion forces. In this contribution an analysis is performed of the tribological behavior of the lubricated contact between the piston pin and the conrod small-end of a high performance motorbike engine. A mass-conserving algorithm is employed to solve the Reynolds equation based on a complementarity formulation of the cavitation problem. The analysis of the asperity contact problem is addressed in detail. A comparison between two different approaches is presented, the former based on the standard Greenwood/Tripp theory and the latter based on a complementarity formulation of the asperity contact problem.

The use of twin-scroll turbocharger turbines has gained popularity in recent years. The main reason is its capability of isolating and preserving pulsating exhaust flow from engine cylinders of adjacent firing order, hence enabling more efficient pulse turbocharging. Asymmetrical twin-scroll turbines have been used to realize high pressure exhaust gas recirculation (EGR) using only one scroll while designing the other scroll for optimal scavenging. This research is based on a production asymmetrical turbocharger turbine designed for a heavy duty truck engine of Daimler AG. Even though there are number of studies on symmetrical twin entry scroll performance, a comprehensive modeling tool for asymmetrical twin-scroll turbines is yet to be found. This is particularly true for a meanline model, which is often used during the turbine preliminary design stage.

Turbocharging has become the favored approach for downsizing internal combustion engines to reduce fuel consumption and CO2 emissions, without sacrificing performance. Matching a turbocharger to an engine requires a balance of various design variables in order to meet the desired performance. Once an initial selection of potential compressor and turbine options is made, corresponding performance maps are evaluated in 1D engine cycle simulations to down-select the best combination. This is the conventional matching procedure used in industry and is ‘passive’ since it relies on measured maps, thus only existing designs may be evaluated. In other words, turbine characteristics cannot be changed during matching so as to explore the effect of design adjustments. Instead, this paper presents an ‘adaptive’ matching methodology for the turbocharger turbine.

Reported in the current paper is a study into the cycle efficiency effects of utilising a complex valvetrain mechanism in order to generate variable in-cylinder charge motion and therefore alter the dilution tolerance of a Direct Injection Spark Ignition (DISI) engine. A Jaguar Land Rover Single Cylinder Research Engine (SCRE) was operated at a number of engine speeds and loads with the dilution fraction varied accordingly (excess air (lean), external Exhaust Gas Residuals (EGR) or some combination of both). For each engine speed, load and dilution fraction, the engine was operated with either both intake valves fully open - Dual Valve Actuation (DVA) - or one valve completely closed - Single Valve Actuation (SVA) mode. The engine was operated in DVA and SVA modes with EGR fractions up to 20% with the excess air dilution (Lambda) increased (to approximately 1.8) until combustion stability was duly compromised.

Internal combustion engines are routinely developed using 1D engine simulation tools. A well-known limitation is the accuracy of the turbocharger compressor and turbine sub-models, which rely on hot gas bench-measured maps to characterize performance. Such discrete map data is inherently too sparse to be used directly in simulation, and so a preprocessing algorithm interpolates and extrapolates the data to generate a wider, more densely populated map. Methods used for compressor map interpolation vary. They may be mathematical or physical in nature, but there is no unified approach, except that they typically operate on input map data in SAE format. For decades it has been common practice for turbocharger suppliers to share performance data with engine OEMs in this form. This paper describes a compressor map interpolation technique based on the nondimensional compressor flow and loading coefficients, instead of SAE-format data.

The purpose of this work was to gain a fundamental understanding of which fuel property parameters are responsible for particulate emission characteristics, associated with key intermediate behavior in the engine cylinder such as the fuel film and insufficient mixing. Accordingly, engine tests were carried out using various fuels having different volatility and chemical compositions under different coolant temperature conditions. In addition, a fundamental spray and film visualization analysis was also conducted using a constant volume vessel, assuming the engine test conditions. As for the physical effects, the test results showed that a low volatility fuel displayed high particulate number (PN) emissions when the injection timing was advanced. The fundamental test clearly showed that the amount of fuel film on the impingement plate increased under such operating conditions with a low volatility fuel.

Engine stop/start and cylinder deactivation are increasingly in use to improve fuel consumption of internal combustion engine in passenger cars. The stop/start technology switches off the engine to whenever the vehicle is at a stand-still, typically in a highly-congested area of an urban driving. The inherent issue with the implementation of stop/start technology in Southeast Asia, with tropical climate such as Malaysia, is the constant demand for the air-conditioning system. This inevitably reduces the duration of engine switch-off when the vehicle at stop and consequently nullifying the benefit of the stop/start system. On the other hand, cylinder deactivation technology improves the fuel consumption at certain conditions during low to medium vehicle speeds, when the engine is at part load operation only. This study evaluates the fuel economy benefit between the stop/start and cylinder deactivation technologies for the actual Kuala Lumpur urban driving conditions in Malaysia.

Throttling loss of downsized gasoline engines is significantly smaller than that of naturally aspirated counterparts. However, even the extremely downsized gasoline engine can still suffer a relatively large throttling loss when operating under part load conditions. Various de-throttling concepts have been proposed recently, such as using a FGT or VGT turbine on the intake as a de-throttling mechanism or applying valve throttling to control the charge airflow. Although they all can adjust the mass air flow without a throttle in regular use, an extra component or complicated control strategies have to be adopted. This paper will, for the first time, propose a de-throttling concept in a twin-charged gasoline engine with minimum modification of the existing system. The research engine model which this paper is based on is a 60% downsized 2.0L four cylinder gasoline demonstrator engine with both a supercharger and turbocharger on the intake.

In a turbocharged engine, preserving the maximum amount of exhaust pulse energy for turbine operation will result in improved low end torque and engine transient response. However, the exhaust flow entering the turbine is highly unsteady, and the presence of the turbine as a restriction in the exhaust flow results in a higher pressure at the cylinder exhaust ports and consequently poor scavenging. This leads to an increase in the amount of residual gas in the combustion chamber, compared to the naturally-aspirated equivalent, thereby increasing the tendency for engine knock. If the level of residual gas can be reduced and controlled, it should enable the engine to operate at a higher compression ratio, improving its thermal efficiency. This paper presents a method of turbocharger matching for reducing residual gas content in a turbocharged engine.

Cylinder deactivation has been utilized by vehicle manufacturers since the 80's to improve fuel consumption and exhaust emissions. Cylinder deactivation is achieved by cutting off fuel supply and ignition in some of the engine cylinders, while their inlet and outlet valves are fully closed. The vehicle demand during cylinder deactivation is sustained by only the firing cylinders, hence increasing their indicated power. Conventionally, half the number of cylinders are shut at certain driving conditions, which normally at the lower demand regime. An optimal strategy will ensure cylinder deactivation contributes to the fuel saving without compromising the vehicle drivability. Cylinder deactivation has been documented to generally improve fuel consumption between 6 to 25 %, depending on the type-approval test drive cycle. However, type-approval test has been reported to differ from the “real-world” fuel consumption values.

Engines equipped with pressure charging systems are more prone to knock partly due the increased intake temperature. Meanwhile, turbocharged engines when operating at high engine speeds and loads cannot fully utilize the exhaust energy as the wastegate is opened to prevent overboost. The turboexpansion concept thus is conceived to reduce the intake temperature by utilizing some otherwise unexploited exhaust energy. This concept can be applied to any turbocharged engines equipped with both a compressor and a turbine-like expander on the intake loop. The turbocharging system is designed to achieve maximum utilization of the exhaust energy, from which the intake charge is over-boosted. After the intercooler, the turbine-like expander expands the over-compressed intake charge to the required plenum pressure and reduces its temperature whilst recovering some energy through the connection to the crankshaft.

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 UK's 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.

Emissions from motor vehicles are known to be the major contributor of air pollution. Pollutants that are commonly concerned and regulated for petrol engines are Hydrocarbons, Carbon Monoxide, Nitrogen Oxides and Particulate Matter. One of the most important factor that vary these pollutants is the engine operating condition such as cold start, low engine loads and high engine loads which are found during actual driving. In actual driving conditions, particularly in urban areas, vehicles regularly travel at idle, low or medium speeds which signify the engine part load operations. Thus urban driving carries a crucial weight on the overall vehicle fuel economy. Understanding the implications of urban driving conditions on fuel economy will allow for strategic application of key technologies such as cylinder deactivation in the efforts towards better efficiency.