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Even though substantial improvements have been made for the lean NOx trap (LNT) catalyst in recent years, the durability still remains problematic because of the sulfur poisoning and sintering of the precious metals at high operating temperatures. Hence, commercial LNT catalysts were aged and tested in order to investigate their performance and activity degradation compared to the fresh catalyst, and establish a proper correlation between the aging methods used. The target of this study is to provide useful information for regeneration strategies and optimize the catalyst management for better performance and durability. With this goal in mind, two different aging procedures were implemented in this investigation. A catalyst was vehicle-aged in the vehicle chassis dynamometer for 100000 km, thus exposed to real conditions. Whereas, an accelerated aging method was used by subjecting a fresh LNT catalyst at 800 °C for 24 hours in an oven under controlled conditions.

Future pressures to reduce the fuel consumption of passenger cars may require the exploitation of alternative combustion strategies for gasoline engines to replace, or use in combination with the conventional stoichiometric spark ignition (SSI) strategy. Possible options include homogeneous lean charge spark ignition (HLCSI), stratified charge spark ignition (SCSI) and homogeneous charge compression ignition (HCCI), all of which are intended to reduce pumping and thermal losses. In the work presented here four different combustion strategies were evaluated using the same engine: SSI, HLCSI, SCSI and HCCI. HLCSI was achieved by early injection and operating the engine lean, close to its stability limits. SCSI was achieved using the spray-guided technique with a centrally placed multi-hole injector and spark-plug. HCCI was achieved using a negative valve overlap to trap hot residuals and thus generate auto-ignition temperatures at the end of the compression stroke.

Analysis of pressure pulsations in ducts is an active research field within the automotive industry. The fluid dynamics and the wave transmission properties of internal combustion (IC) engine intake and exhaust systems contribute to the energy efficiency of the engines and are hence important for the final amount of CO₂ that is emitted from the vehicles. Sound waves, originating from the pressure pulses caused by the in- and outflow at the engine valves, are transmitted through the intake and exhaust system and are an important cause of noise pollution from road traffic at low speeds. Reliable prediction methods are of major importance to enable effective optimization of gas exchange systems. The use of nonlinear one-dimensional (1D) gas dynamics simulation software packages is widespread within the automotive industry. These time-domain codes are mainly used to predict engine performance parameters such as output torque and power but can also give estimates of radiated orifice noise.

During 1991 Volvo Car Corporation has introduced the new Volvo 850 GLT model featuring front wheel drive with transverse installation of the engine and gearbox. The powertrain; consists of a new in-line five-cylinder engine in combination with a four speed electronically controlled automatic gearbox or a five speed manual gearbox. The engine features DOHC 20 valves, V-VIS (Volvo Variable Induction System), well tuned exhaust system and microprocessor controlled engine management systems. The engine was designed and developed as a new member of Volvo's modular engine family. The first member was the in-line six-cylinder engine B6304F [1] introduced in 1990. The modular engines have a large number of identical components and the major components are machined in common transfer lines which makes the manufacturing process highly rational and cost-effective.

Experiments on a modern DI Diesel engine were carried out: The engine was fuelled with standard Diesel fuel, RME and a mixture of 85% standard Diesel fuel, 5% RME and 10% higher alcohols under low load conditions (4 bar IMEP). During these experiments, different external EGR levels were applied while the injection timing was chosen in a way to keep the location of 50% heat release constant. Emission analysis results were in accordance with widely known correlations: Increasing EGR rates lowered NOx emissions. This is explained by a decrease of global air-fuel ratio entailing longer ignition delay. Local gas-fuel ratio increases during ignition delay and local combustion temperature is lowered. Exhaust gas analysis indicated further a strong increase of CO, PM and unburned HC emissions at high EGR levels. This resulted in lower combustion efficiency. PM emissions however, decreased above 50% EGR which was also in accordance with previously reported results.

Car accident investigations have shown that the head, the chest and the abdomen are the three most vulnerable body regions in side impacts, when serious-to-fatal (MAIS 3-6) injuries are considered. Injuries are much more common to occupants seated on the struck side than to those on the non-struck side. The development of new side impact protection systems has therefore been focused on struck side occupants. The first airbag system for side impact protection, jointly developed by Volvo and Autoliv, was introduced on the market in 1994. The SIPS bag is seat-mounted and protects mainly the chest and the abdomen, and also to some extent the head, since the head's lateral relative displacement is reduced by the side airbag, thereby keeping the head inside the car's outer profile. However, if an external object is exposed in the head area, for example in a truck-to-car side impact or in a single car collision into a pole or a tree, there is a need for an additional head protection device.

This paper presents how hardware in the loop (HIL) simulations have been used for testing during the development of the adaptive cruise control (ACC) and collision warning with brake support (CWBS) functions implemented in the Volvo S80. Both the brake system controller and the controller where the ACC and CWBS functions were implemented were tested. The HIL simulator was used for automated batch simulations in which different controller software releases were analyzed from both system, fail-safe and functional performance perspectives. This paper presents the challenges and the benefits of using HIL simulations when developing distributed active safety functions. Some specific simulation results are analyzed and discussed. The conclusion shows that although it is difficult and time-consuming to develop a complete HIL simulation environment for active safety functions such as ACC and CWBS, the benefits justify the investment.

Future demands for improvements in the fuel economy of gasoline passenger car engines will require the development and implementation of advanced combustion strategies, to replace, or combine with the conventional spark ignition strategy. One possible strategy is homogeneous charge compression ignition (HCCI) achieved using negative valve overlap (NVO). However, several issues need to be addressed before this combustion strategy can be fully implemented in a production vehicle, one being to increase the upper load limit. One constraint at high loads is the combustion becoming too rapid, leading to excessive pressure-rise rates and large pressure fluctuations (ringing), causing noise. In this work, efforts were made to reduce these pressure fluctuations by using a late injection during the later part of the compression. A more appropriate acronym than HCCI for such combustion is SCCI (Stratified Charge Compression Ignition).

The development of a new combustion system for a light-duty diesel engine is presented. The soot-NOx trade-off is significantly improved with maintained or improved efficiency. This is accomplished only by altering the combustion chamber geometry, and thereby the in-cylinder flow. The bowl geometry is developed in CFD and validated in single cylinder tests. Tests and simulations align remarkably well. Under identical conditions in the engine the new combustion chamber decreases smoke by 11-27%, NOx by 2-11%, and maintains efficiency as compared to the baseline geometry. The injector nozzle is matched to the new bowl using design of experiments (DoE). By this method transfer functions are obtained that can be used to optimize the system using analytical tools. The emissions show a complex dependence on the nozzle geometry. The emission dependence on nozzle geometry varies greatly over the engine operating range.

This paper compares and discusses the impact of conventional and improved start strategies on the design of the exhaust aftertreatment system. It is recognised that hardware measures on the exhaust side will not be sufficient if Volvo's 5 and 6 cylinder engines are to fulfil SULEV emission levels, assuming passive three way systems only. A new start strategy, providing an excessive heat profile combined with low engine out hydrocarbon emissions, was therefore developed. Temperature profiles, raw emissions and mass flow obtained with the Lean Start Calibration will be shown for the 5 and 6 cylinder engines, both naturally aspirated as turbo. The remaining part of the paper presents a brief history of the exhaust aftertreatment design modifications for Volvo's 5 cylinder N/A engine fulfilling LEV, ULEV I, ULEV II and PZEV emission levels respectively. The impact of the new start strategy on the cold start performance will be shown.

A single-cylinder engine was operated in HCCI combustion mode with different kinds of commercial fuels. The HCCI combustion was generated by creating a negative valve overlap (early exhaust valve closing combined with late intake valve opening) thus trapping a large amount of residuals (∼ 55%). Fifteen different fuels with high octane numbers were tested six of which were primary reference fuels (PRF's) and nine were commercial fuels or reference fuels. The engine was operated at constant operational parameters (speed/load, valve timing and equivalence ratio, intake air temperature, compression ratio, etc.) changing only the fuel type while the engine was running. Changing the fuel affected the auto-ignition timing, represented by the 50% mass fraction burned location (CA50). However these changes were not consistent with the classical RON and MON numbers, which are measures of the knock resistance of the fuel. Indeed, no correlation was found between CA50 and the RON or MON numbers.

Driver errors cause a majority of all car accidents. Forward collision avoidance systems aim at avoiding, or at least mitigating, host vehicle frontal collisions, of which rear-end collisions are one of the most common. This is done by either warning the driver or braking or steering away, respectively, where each action requires its own considerations and design. We here focus on forward collision by braking, and present a general method for calculating the risk for collision. A brake maneuver is activated to mitigate the accident when the probability of collision is one, taking all driver actions into considerations. We describe results from a simulation study using a large number of scenarios, created from extensive accident statistics. We also show some results from an implementation of a forward collision avoidance system in a Volvo V70. The system has been tested in real traffic, and in collision scenarios (with an inflatable car) showing promising results.

Operating an engine in homogeneous charge compression ignition (HCCI) mode requires the air fuel mixture to be very lean or highly diluted with residuals. This is in order to slow the kinetics down and to avoid too rapid heat release. Consequently, the operational window for the engine in HCCI mode is not the same as for the engine operating in spark ignited (SI) mode. Homogeneous charge compression ignition engine mode, in this study, is accomplished by trapping residual mass using variable valve timing. With the residual trapping method, the engine cannot be started in HCCI mode and due to the dilution, the engine in HCCI mode can only be operated in the part - load regime. Hence, a mode change between spark ignited and HCCI modes, and vice versa is required. This study reports the development of a mode change strategy for a single cylinder camless engine, and its successful implementation in a camless multi cylinder engine.

With alternative fuels having moved more into market in light of their reduction of emissions of CO2 and other air pollutants, the spark ignited internal combustion engine design has only been affected to small extent. The development of combustion engines running on natural gas or Biogas have been focused to maintain driveability on gasoline, creating a multi fuel platform which does not fully utilise the alternative fuels’ potential. However, optimising these concepts on a fundamental level for gas operation shows a great potential to increase the level of utilisation and effectiveness of the engine and thereby meeting the emissions legislation. The project described in this paper has focused on optimising a combustion concept for CNG combustion on a single cylinder research engine. The ICE’s efficiency at full load and the fuels characteristics, including its knock resistance, is of primary interest - together with part load performance and overall fuel consumption.

Highly refined NVH (Noise, Vibration and Harshness) is a key attribute for premium segment passenger cars. All noise sources such as powertrain, tires, wind, climate unit and etc. must be well balanced and at such a low level that the customer expectations are met or exceeded. However, not only are the NVH levels of importance but the character of the noise must also meet the high demands from premium car customers. This is especially true for diesel engines which historically have been more prone to have a less refined engine noise character than petrol engines. This paper will describe an investigation of what is defined as “engine presence” in four-cylinder diesel engine cars. The scope is to define a method for consistent subjective assessment of engine presence and to find the relationship and investigate the correlation between the “perceived loudness”, “perceived harshness” and the overall engine presence interior of the car.

An experimental study of EGR and turbocharging concepts has been performed on an experimental 2.0-litre 4-cylinder turbocharged Euro6 light-duty diesel engine. The purpose of the study was to investigate the emissions and fuel consumption trade-off for different concept combinations. The impact of low-pressure and high-pressure EGR was studied in terms of engine-out emissions and fuel consumption. Moreover, the influence of single-stage and two-stage turbocharging was investigated in combination with the EGR systems, and how the engine efficiency could be further improved after engine calibration optimization. During low load engine operation where throttling may be required to achieve the desired low-pressure EGR rate, the difference in fuel consumption impact was studied for exhaust throttling and intake throttling, respectively. The cooling impact on high-pressure EGR was compared in terms of emissions and fuel consumption.

Passenger cars equipped with diesel engines will meet challenging emission legislation for the coming decade, with introduction of Euro6 and Euro7, which comprises reduced NOX emissions and possibly new driving cycles including off-cycle limits. The technology measures to meet these legislative limits comprise a broad spectrum of engine and aftertreatment, i.e., engine measures such as improved fuel injection with respect to mass and timing, improved exhaust gas recirculation, improved warm-up and reduced friction, as well as aftertreatment measures such as selective catalytic reduction and lean NOX trap in combination with diesel particulate filter, and the thereby associated engine control. The resulting technology matrix is therefore large, and calls for a multidisciplinary simulation approach for appropriate selection and optimization of technology and control with the objectives and constraints of emissions, fuel consumption, performance and cost.

Maintaining the current ratio between certified and the customer-observed fuel consumption even with future required levels poses a considerable challenge. Increasing the efficiency of the driveline enables certified fuel consumption down to a feasible level in the order of 80 g CO₂/km using fossil fuels. Mainly affecting off-cycle fuel consumption, energy amounts used to create good interior climate as well as energy-consuming options and features threaten to further increase. Progressing urbanization will lead to decreasing average vehicle speeds and driving distances. Highly efficient powertrains come with decreased amounts of waste energy traditionally used for interior climate conditioning, thus making necessary a change of auxiliary systems.

The demands for a future diesel engine in terms of emission compliance, CO2 emissions, performance and cost effectiveness set new requirements for the development process of the combustion system. This paper focuses on the development of the next generation Volvo Cars diesel combustion system, which should comply with Euro 6d including Real Driving Emissions (RDE), with emphasis on the novel methods applied throughout the process. The foundation of a high performing combustion system is formed by first determining the requirements for the system, after which the key factors that affect system performance are selected, such as the charge motion, combustion chamber geometry and injector nozzle geometry. Based on the requirements, a robust charge motion with desired flow characteristics is defined. A new automated CFD optimization process for combustion chamber geometry and spray target is developed.

In a previous study, a passive sensor (HVAC) manikin coupled with a human thermal model was used to predict the thermal comfort of human test participants. The manikin was positioned among the test participants while they were collectively exposed to a mild transient heat up within a thermally asymmetric chamber. Ambient conditions were measured using the HVAC manikin’s distributed sensor system, which measures air velocity, air temperature, radiant heat flux, and relative humidity. These measurements were supplied as input to a human thermal model to predict thermophysiological response and subsequently thermal sensation and comfort. The model predictions were shown to accurately reproduce the group trends and the “time to comfort” at which a transition occurred from a state of thermal discomfort to comfort. In the current study, the effectiveness of using a coupled HVAC manikin-model system to evaluate a vehicle climate control system was investigated.