José Manuel Luján

Modelling of turbocharged diesel engines in transient operation. Part 1: Insight into the relevant physical phenomena

Abstract A new calculation model, able to predict the engine performance during an engine transient, has been developed, based on an existing wave action code. Previously to the model development, the turbocharged diesel engines transient phenomena (turbocharger lag, thermal transient and energy transport delay) were deeply analysed on the basis of experimental information. The study has been focused on the load transient, i.e. torque increase from idle, at constant engine speed of a high speed direct injection (DI) turbocharged engine. Experimental load transient tests have been performed, with the aim of obtaining a combustion database during engine transient operation, to input into a combustion simulation submodel. The applied methodology allows the characterization of the transient combustion process in any DI turbocharged engine.

An approach to model-based fault detection in industrial measurement systems with application to engine test benches

An approach to fault detection (FD) in industrial measurement systems is proposed in this paper which includes an identification strategy for early detection of the appearance of a fault. This approach is model based, i.e. nominal models are used which represent the fault-free state of the on-line measured process. This approach is also suitable for off-line FD. The framework that combines FD with isolation and correction (FDIC) is outlined in this paper. The proposed approach is characterized by automatic threshold determination, ability to analyse local properties of the models, and aggregation of different fault detection statements. The nominal models are built using data-driven and hybrid approaches, combining first principle models with on-line data-driven techniques. At the same time the models are transparent and interpretable. This novel approach is then verified on a number of real and simulated data sets of car engine test benches (both gasoline—Alfa Romeo JTS, and diesel—Caterpillar). It is demonstrated that the approach can work effectively in real industrial measurement systems with data of large dimensions in both on-line and off-line modes.

A methodology to identify the intake charge cylinder-to-cylinder distribution in turbocharged direct injection Diesel engines

Exhaust gas recirculation (EGR) is currently the most important NOx emission control system. During the last few years the EGR rate has increased progressively as pollutant emission regulations have become more restrictive. High EGR rate levels have given the effect of the unsuitable EGR and air distribution between cylinders away, which causes undesirable engine behavior. In this sense, the study of the EGR distribution between cylinders achieves high importance. However, despite the fact that the EGR is continuously under study, not many studies have been undertaken to approach its distribution between cylinders. In concordance with the aspects outlined before, the aim of this paper is to propose a methodology that permits us to identify the EGR cylinder-to-cylinder dispersion in a commercial engine. In order to achieve this objective, experimental tests have been combined with both one-dimensional and three-dimensional fluid dynamic models.

Modelling Study of the Scavenging Process in a Turbocharged Diesel Engine with Modified Valve Operation

The instantaneous gas exchange process in a turbocharged direct injection diesel engine with an intake valve pre-lift and an exhaust valve post-lift has been studied in detail by means of a wave action model. Such a modified valve timing operation allows the internal exhaust gas recirculation and the residual burnt gas ratio in the combustion chamber to be increased and modulated. A simple scavenging model has been included in the global calculation code, in order to obtain information on the instantaneous composition of the gas flow across valves. The analysis sheds light on the intricate flow phenomena produced by the additional valve lift periods, and evaluates the potential of this technique in the control of the residual burnt gas in the cylinder.

Exhaust pressure pulsation observation from turbocharger instantaneous speed measurement

In internal combustion engines, instantaneous exhaust pressure measurements are difficult to perform in a production environment. The high temperature of the exhaust manifold and its pulsating character make its application to exhaust gas recirculation control algorithms impossible. In this paper an alternative method for estimating the exhaust pressure pulsation is presented. A numerical model is built which enables the exhaust pressure pulses to be predicted from instantaneous turbocharger speed measurements. Although the model is data based, a theoretical description of the process is also provided. This combined approach makes it possible to export the model for different engine operating points. Also, compressor contribution in the turbocharger speed pulsation is discussed extensively. The compressor contribution is initially neglected, and effects of this simplified approach are analysed.

DFT-based controller for fuel injection unevenness correction in turbocharged diesel engines

Although combustion failure diagnosis techniques have been widely developed over the last few years, real-time correction of fuel injection failures, such as drift, are still deficient. In this paper, a controller for the correction of fuel injection failures is presented; the aim of the algorithm is to ensure that the same quantity of fuel is injected in each one of the cylinders. The controller is based on a linear model that relates the low-frequency region of the Fourier transform of a dynamic engine signal and fuel injection unevenness. Model inversion is used as an injection failure observer, and discrepancies in the injected fuel mass in each cylinder can be estimated, even in the case of multiple and simultaneous failures. This observer is used for closing the loop and performing the control action via an integral controller. Theoretical bases are given for the controller, and the stability and settling error are related to the error of the linear engine model assumed. This technique can be used for different engine signals, like crankshaft speed, exhaust manifold pulsation, and turbocharger instantaneous speed. Experimental results obtained on a diesel turbocharged engine, where the turbocharger instantaneous speed was used as input information of the controller, are presented proving the performance of the fuel quantity control algorithm

On the combination of high-pressure and low-pressure exhaust gas recirculation loops for improved fuel economy and reduced emissions in high-speed direct-injection engines

In this paper, an experimental study of the combination of low-pressure and high-pressure exhaust gas recirculation architectures has been carried out. In the first part of the paper, the effects of both high-pressure and low-pressure exhaust gas recirculation architectures on engine behaviour and performance are analysed by means of a series of steady tests. In the second part, the effects of the combination of both architectures are addressed. The results show that the low-pressure configuration improves high-pressure exhaust gas recirculation results in brake-specific fuel consumption, nitrogen oxides and exhaust gas opacity; nevertheless, hydrocarbon emissions are increased, especially during the engine warm up. In addition, the exhaust gas recirculation rate achieved with low-pressure systems is limited by the pressure difference between diesel particulate matter outlet and compressor inlet; therefore, the high-pressure system can be used to achieve the required exhaust gas recirculation levels without increasing pumping losses. In this sense, the combination of both exhaust gas recirculation layouts offers significant advantages to reduce emissions and fuel consumption to meet future emission requirements.

Transient particle emission measurement with optical techniques

Particulate matter is responsible for some respiratory and cardiovascular diseases. In addition, it is one of the most important pollutants of high-speed direct injection (HSDI) passenger car engines. Current legislation requires particulate dilution tunnels for particulate matter measuring. However for development work, dilution tunnels are expensive and sometimes not useful since they are not able to quantify real-time particulate emissions during transient operation. In this study, the use of a continuous measurement opacimeter and a fast response HFID is proven to be a good alternative to obtain instantaneous particle mass emissions during transient operation (due to particulate matter consisting mainly of soot and SOF). Some methods and correlations available from literature, but developed for steady conditions, are evaluated during transient operation by comparing with mini-tunnel measurements during the entire MVEG-A transient cycle. A new correlation was also derived from this evaluation. Results for soot and SOF (obtained from the new correlation proposed) are compared with soot and SOF captured with particulate filters, which have been separated by means of an SOF extraction method. Finally, as an example of ECU design strategies using these sort of correlations, the EGR valve opening is optimized during transient operation. The optimization is performed while simultaneously taking into account instantaneous fuel consumption, particulate emissions (calculated with the proposed correlation) and other regulated engine pollutants.

Cost of ownership-efficient hybrid electric vehicle powertrain sizing for multi-scenario driving cycles

During the last decade, hybrid electric vehicles have gained a presence in the automotive market. On the streets, in motorsports and in society, hybrid electric vehicles are increasingly common. Many manufacturers have become involved in hybrid electric vehicles, while others have hybrid electric vehicle projects in development. Thus, there is already a great variety of hybrid electric vehicles in production, from small microhybrid vehicles to range extenders. Although there are some hybrid electric vehicles designed for urban driving or luxury segments of the market, most of the market share is aimed to the same kind of use and driving, resulting in potentially subsized or oversized hybrid systems that could lead to inefficient use of the vehicle’s fuel-saving capabilities in many situations. The present work studies the influence of the sizes of the powertrain components (i.e. the engine, the motor and the battery) on the fuel economy under different assumptions: city driving, highway driving and mixed driving. The utilized framework permits the calculation of the theoretically optimum powertrain sizes assuming a particular target. Different drivers and different traffic conditions are also evaluated. Finally, a long-term cost evaluation is carried out to estimate the optimal sizes of the hybrid electric vehicle powertrain as functions of the type of use of the vehicle throughout its life cycle.

Potential of Using a Nozzle at the Compressor Inlet of a High-Speed Direct-Injection Diesel Engine

The present work reports the effect of a nozzle placed upstream of the compressor of a high-speed direct-injection diesel engine. It has been observed that mounting a nozzle at the compressor inlet can lead to a shift in the compressor surge line to lower mass flowrates. In order to study the effect of the nozzle on the engine performance a set of experimental investigations has been conducted including characterization of the nozzle alone using a flow test rig up to sonic conditions and characterization of the nozzle—compressor unit by determining its operation map in a turbocharger test bench. The distortions in the compressor inlet are usually considered as a disadvantage, as they affect the efficiency and the behaviour of the turbocharger. However, the comparison between the original compressor map (provided by the manufacturer) and the nozzle—compressor map given in the present paper shows that the change in the flow pattern caused by the nozzle improves the engine—turbocharger coupling and thus reduces the air mass flowrate, leading to a surge by 30 per cent, for a given pressure ratio. The improvement in turbocharging does not necessarily increase the performance of the engine. Nevertheless, the possibility of increasing the boost pressure allows elevated fuel flowrates to be applied while still maintaining the combustion efficiency, thus increasing the power of the engine