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Increasing fuel and electricity prices create high pressure to develop efficient external aerodynamics of road cars. At the same time, development cycles are getting shorter to meet changing customer preferences while physical testing capacities remain limited, creating a pressing need for fast and accurate turbulence models to predict aerodynamic performance. This paper introduces and discusses different turbulence modelling approaches beyond the well-known and established models used today in the industry. The RANS Lag Elliptic Blending (Lag EB) k − ϵ model, which enables highly accurate steady-state RANS, was chosen as the baseline approach. As a medium fidelity approach Scale-Resolving Hybrid (SRH) model was utilized, which modifies a RANS base model to produce a smooth transition between URANS and LES behavior. The Wall-Modelled LES (WMLES) method was chosen for high fidelity simulations.

The implementation of Synthetic Jet Actuators (SJAs) on Unmanned Aerial Vehicles (UAVs) provides a safe test-bed for analysis of improved performance, in the hope of certification of this technology on commercial aircraft in the future. The use of high resolution numerical methods (i.e. CFD) to capture the details of the effects of SJAs on flows and on the hosting lifting surface are computationally expensive and time-consuming, which renders them ineffective for use in real-time flow control implementations. Suitable alternatives include the use of Reduced Order Models (ROMs) to capture the lower resolution overall effects of the jets on the flow and the hosting structure. This research paper analyses the effects of SJAs on aircraft wings using a ROM for the purpose of determining the unsteady aerodynamic forces modified by the presence of the SJAs. The model developed is a 3D unsteady panel code where the jets are represented by source panels.

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.

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.

Mandated pollutant emission levels are shifting light-duty vehicles towards hybrid and electric powertrains. Heavy-duty applications, on the other hand, will continue to rely on internal combustion engines for the foreseeable future. Hence there remain clear environmental and economic reasons to further decrease IC engine emissions. Turbocharged diesels are the mainstay prime mover for heavy-duty vehicles and industrial machines, and transient performance is integral to maximizing productivity, while minimizing work cycle fuel consumption and CO2 emissions. 1D engine simulation tools are commonplace for “virtual” performance development, saving time and cost, and enabling product and emissions legislation cycles to be met. A known limitation however, is the predictive capability of the turbocharger turbine sub-model in these tools.

The aim of this paper is to extend the evaluation of the accuracy of published 1-D pressure loss coefficients which are used in 1-D gas dynamics models, in unsteady compressible flows propagating in the exhaust pulses in manifolds. These pressure loss coefficients were derived from the conservation of linear momentum over finite control volumes based on assumptions including steady flow. The objectives of this work were to evaluate the accuracy of the pressure loss coefficients over the type of flows generated by engine-like pressure pulses propagating in a range of three-pipe junctions. The evaluation was performed by reference to results from unsteady, compressible, 3-D Reynolds-averaged computational fluid dynamic (CFD - open source software OpenFOAM) simulations. Two of the junction branches represented the exhaust pipes from two cylinders and the remaining was the outlet pipe. All pipes had a diameter of 25mm with length ratio 1:2 between inlet and outlet.

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.

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.

The Ahmed Body is one of the most widely studied bluff bodies used for automotive conceptual studies and Computational Fluid Dynamics - CFD software validation. With the advances of the computational processing capacity and improvement in cluster costs, high-fidelity turbulence models, such as Detached Eddies Simulation – DES and Large Eddies Simulation – LES, are becoming a reality for industrial cases, as studied by BUSCARIOLO et al. (2016) [4], evaluating DES models to automotive applications. This work presents a correlation study between a computational and physical model of an Ahmed Body with slant angle of 0 degree, also known as a squared back. Physical results are from a wind tunnel test, performed by STRACHAN et al. (2007) [11] considering moving ground and Reynolds number of 1.7M, based on the length of the body.

Turbocharger hot gas stand testing is routinely carried out in the industry both to provide an experimental assessment of different designs, and to confirm to automotive OEM customers that the product meets the afore-promised levels of performance and durability. The resulting characteristics, or maps, have a hugely significant role in the correct matching of turbocharger options for engine applications. However, since these are generated from experimentally-determined values of pressure, temperature and mass flow, with each sensed variable having an inherent finite error, the uncertainty in these measured components is variously propagated through to the flow and efficiency characteristics - and the significance of this is not well recognized.

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).

Turbocharged diesel engines are widely used in off-road applications including construction and mining machinery, electric power generation systems, locomotives, marine, petroleum, industrial and agricultural equipment. Such applications contribute significantly to both local air pollution and CO₂ emissions and are subject to increasingly stringent legislation. To improve fuel economy while meeting emissions limits, manufacturers are exploring engine downsizing by increasing engine boost levels. This allows an increase in IMEP without significantly increasing mechanical losses, which results in a higher overall efficiency. However, this can lead to poorer transient engine response primarily due to turbo-lag, which is a major penalty for engines subjected to fast varying loads. To recover transient response, the turbocharger can be electrically assisted by means of a high speed motor/generator.

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.

The measurement of the rate of fuel injection using a constant volume, fluid filled chamber and measuring the pressure change as a function of time due to the injected fluid (the so called “Zeuch” method) is an industry standard due to its simple theoretical underpinnings. Such a measurement device is useful to determine key timing and quantity parameters for injection system improvements to meet the evolving requirements of emissions, power and economy. This study aims to further the understanding of the nature of cavitation which could occur in the near nozzle region under these specific conditions of liquid into liquid injection using high pressure diesel injectors for heavy duty engines. The motivation for this work is to better understand the temporal signature of the pressure signals that arise in a typical injection cycle.

This paper describes the development of a thin film rheometer able to measure the viscosity of lubricant films of the order of 200 μm thickness on flat, solid surfaces. The rheometer consists of a small cylinder mounted on a piezo bimorph which is divided electrically into two halves. When an AC voltage is applied to the one half of the piezo it causes the flat surface of the cylinder to oscillate in its own plane with an amplitude of a few microns. This motion produces an AC output from the other half of the piezo. The flat face of the cylinder is held parallel to an oily test surface and the latter is supported on a micrometer stage so that the gap between the two surfaces can be adjusted. As the gap is narrowed the oil film dampens the sinusoidal motion of the cylinder and the extent of this damping can be used to determine the viscosity of the oil film between the surfaces.

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.

In Gasoline Direct Injection engines, direct exposure of the injector to the flame can cause combustion products to accumulate on the nozzle, which can result in increased particulate emissions. This research observes the impact of injector fouling on particulate emissions and the associated injector spray pattern and shows how both can be reversed by utilising fuel detergency. For this purpose multi-hole injectors were deliberately fouled in a four-cylinder test engine with two different base fuels. During a four hour injector fouling cycle particulate numbers (PN) increased by up to two orders of magnitude. The drift could be reversed by switching to a fuel blend that contained a detergent additive. In addition, it was possible to completely avoid any PN increase, when the detergent containing fuel was used from the beginning of the test. Microscopy showed that increased injector fouling coincided with increased particulate emissions.

The present investigation is centered around two motored research gasoline direct-injection engines, equipped with a pressure-swirl atomizer closely spaced with the centrally located spark plug. At first a Laser Doppler Velocimetry system was employed to characterize the in-cylinder airflow in one of the engines. A comparison was made to velocity profiles in a port-fuel injected engine of similar design characteristics, which revealed a different decay mechanism of the large-scale flow structure and associated higher turbulence levels in the pentroof of the cylinder. Second, images of the hollow cone fuel spray generated by the direct injector were recorded for three different injection timings in order to discuss the temporal and spatial development of the liquid phase in the engine cylinder in terms of its interaction with the gas motion.

A mixed flow turbine with pivoting nozzle vanes was designed and tested to actively adapt to the pulsating exhaust flow. The turbine was tested at equivalent speed of 48000 rpm with inlet flow pulsation of 40Hz and 60Hz, which corresponds to a 4-stroke diesel engine speed of 1600 rpm and 2400 rpm respectively. The nozzle vane operating schedules for each pulse period are evaluated experimentally in two general modes; natural opening and closing of the vanes due to the pulsating flow and the forced sinusoidal oscillation of the vanes to match the incoming pulsating flow. The turbine energy extraction as well as efficiency is compared for the two modes to formulate its effectiveness.