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Current trends for IC-engines are driving the development of more efficient engines with higher specific power. This is true for both light and heavy duty vehicles and has led to an increased use of super-charging. The super-charging can be both in the form of a single or multi-stage turbo-charger driven by exhaust gases, or via a directly driven compressor. In both cases a possible noise problem can be a strong Blade Passing Frequency (BPF) typically in the kHz range and above the plane wave range. In this paper a novel type of compact dissipative silencer developed especially to handle this type of problem is described and optimized. The silencer is based on a combination of a micro-perforated (MPP) tube backed by a locally reacting cavity. The combined impedance of micro-perforate and cavity is chosen to match the theoretical optimum known as the Cremer impedance at the mid-frequency in the frequency range of interest.

Fuel consumption of vehicles has received increased attention in recent years; however one neglected area that can have a large effect on this is the energy usage for the interior climate. This study aims to investigate the energy usage for the interior climate for different conditions by measurements on a complete vehicle. Twelve different NEDC tests in different temperatures and thermal states of the vehicle were completed in a climatic wind tunnel. Furthermore one temperature sweep from 43° to −18°C was also performed. The measurements focused on the heat flow of the air, from its sources, to its sink, i.e. compartment. In addition the electrical and mechanical loads of the climate system were included. The different sources of heating and cooling were, for the tested powertrain, waste heat from the engine, a fuel operated heater, heat pickup of the air, evaporator cooling and cooling from recirculation.

In recent years fuel consumption of passenger vehicles has received increasing attention by customers, the automotive industry, regulatory agencies and academia. However, some areas which affect the fuel consumption have received relatively small interest. One of these areas is the total energy used for vehicle interior climate which can have a large effect on real-world fuel consumption. Although there are several methods described in the literature for analyzing fuel consumption for parts of the climate control system, especially the Air-Condition (AC) system, the total fuel consumption including the vehicle interior climate has often been ignored, both in complete vehicle testing and simulation. The purpose of this research was to develop a model that predicts the total energy use for the vehicle interior climate. To predict the total energy use the model included sub models of the passenger compartment, the air-handling unit, the AC, the engine cooling system and the engine.

This paper describes the experimental study of a tumble-flap mounted in the intake port of a single-cylinder spark-ignited gasoline engine. The research question addressed was whether an optimal tumble level could be found for the combustion system under investigation. Indicated fuel consumption was measured for a number of part-load operating points with the tumble-flap either open or closed. The experimental results were subjected to an energy balance analysis to understand which portion of the fuel energy was converted to work and how much was lost by incomplete combustion, heat losses to walls and to the exhaust gases, as well as to pumping losses. Closing the tumble-flap resulted in reduced fuel consumption only in a small area of the operating map: only at low-speed, low-load operation, a benefit could be obtained.

To improve fuel efficiency and facilitate handling of the vehicle in a dense city environment, it should be as small as possible given its intended application. This downsizing trend impacts the size of the engine bay, where the air filter box has to be packed in a reduced space, still without increased pressure drop, reduced load capacity nor lower filtering efficiency. Due to its flexibility and reduced cost, CFD simulations play an important role in the optimization process of the filter design. Even though the air-flow through the filter box changes as the dust load increases, the current modeling framework seldom account for such time dependence. Volvo Car Corporation presents an industrial affordable model to solve the time-dependent dust load on filter elements and calculate the corresponding flow behavior over the life time of the air filter box.

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.

Direct gasoline injection combined with turbo charging and down sizing is a cost effective concept to meet future requirements for emission reduction as well as increased efficiency for passenger cars. It is well known that turbulence induced by in-cylinder air motion can influence efficiency. In this study, the intake-generated flow field was varied for a direct injected turbo charged concept, with the intent to evaluate if further increase in tumble potentially could lead to higher efficiency compared to the baseline. A single cylinder head with flow separating walls in the intake ports and different restriction plates was used to allow different levels of tumble to be experimentally evaluated in a single cylinder engine. The different levels of tumble were quantified by flow rig experiments.

Passenger car fuel consumption is a constant concern for automotive companies and the contribution to fuel consumption from aerodynamics is well known. Several studies have been published on the aerodynamics of wheels. One area of wheel aerodynamics discussed in some of these earlier works is the so-called ventilation resistance. This study investigates ventilation resistance on a number of 17 inch rims, in the Volvo Cars Aerodynamic Wind Tunnel. The ventilation resistance was measured using a custom-built suspension with a tractive force measurement system installed in the Wheel Drive Units (WDUs). The study aims at identifying wheel design factors that have significant effect on the ventilation resistance for the investigated wheel size. The results show that it was possible to measure similar power requirements to rotate the wheels as was found in previous works.

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.

Targets for reducing emissions and improving energy efficiency present the automotive industry with many challenges. Passenger cars are by far the most common means of personal transport in the developed part of the world, and energy consumption related to personal transportation is predicted to increase significantly in the coming decades. Improved aerodynamic performance of passenger cars will be one of many important areas which will occupy engineers and researchers for the foreseeable future. The significance of wheels and wheel housings is well known today, but the relative importance of the different components has still not been fully investigated. A number of investigations highlighting the importance of proper ground simulation have been published, and recently a number of studies on improved aerodynamic design of the wheel have been presented as well. This study is an investigation of aerodynamic influences of different tires.

The principles of an electronic nose are described briefly. It is shown how a sensor array in combination with pattern recognition software can be used for quality control and classification of car interior trim materials. Anomalies such as bad smelling leather and carpet are shown as outliers. The results are consistent with GC-MS TVOC measurements as well as with data from a human sensory panel. More needs to be done, however, regarding the sensor stability in particular before the sensor array can be used for routine classification of the trim materials.

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.

Traditional approaches to pollution control have been to develop benign non-polluting processes or to abate emissions at the tailpipe or stack before emitting to the atmosphere. A new technology called PremAir®* Catalyst Systems takes a different approach and directly reduces ambient ground level ozone. This technology can be applied to both mobile and stationary applications. For automotive applications, the new system involves placing a catalytic coating on the car's radiator or air conditioner condenser. As air passes over the radiator or condenser, the catalyst converts the ozone into oxygen. Three Volvo vehicles with a catalyst coating on the radiator were tested on the road during the 1997 summer ozone season in southern California to assess performance. Studies were also conducted in Volvo's laboratory to determine the effect of the catalyst coating on the radiator's performance with regard to corrosion, heat transfer and pressure drop.

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 describes the development of a robust and accurate method to model one-phase heat exchangers in complete vehicle air flow simulations along with a comprehensive comparison of EFD and CFD results. The comparison shows that the inlet radiator coolant temperatures obtained with CFD were within ±4°C of the experimental data with a trend in the differences being dependent on the car speed. The relative differences in cooling air mass flow rates increase with increasing car speed, with CFD values generally higher than EFD. From the investigation, the conclusion is that the methodology and modeling technique presented offer an accurate tool for concept and system solutions on the front end design, cooling package and fan. Care must be taken in order to provide the best possible boundary conditions paying particular attention to the heat losses in the engine, performance data for the radiator and fan characteristics.

When developing gas exchange and combustion systems at Volvo Car Corporation, CFD (Computational Fluid Dynamics) is today a key tool. Three dimensional CFD is by tradition used to study one single component (e.g. manifolds and ports) at a time. Our experience is that this approach suffers from two main limitations; first that the boundary conditions (both upstream and downstream) are uncertain; and secondly that validation against experimental data is extremely difficult since any measured parameter will depend on the complete engine. Distribution of secondary gases and AFR (Air to Fuel ratio) are typical examples where traditional CFD methods fail. One proposed way to overcome these problems is to use 1D gas exchange models coupled with 3D CFD. The main problem with this approach is however the positioning and treatment of the boundaries between the models. Furthermore, the boundaries themselves will unconditionally cause disturbances in the pressure fields.

To elucidate the processes controlling the auto-ignition timing and overall combustion duration in homogeneous charge compression ignition (HCCI) engines, the distribution of the auto-ignition sites, in both space and time, was studied. The auto-ignition locations were investigated using optical diagnosis of HCCI combustion, based on laser induced fluorescence (LIF) measurements of formaldehyde in an optical engine with fully variable valve actuation. This engine was operated in two different modes of HCCI. In the first, auto-ignition temperatures were reached by heating the inlet air, while in the second, residual mass from the previous combustion cycle was trapped using a negative valve overlap. The fuel was introduced directly into the combustion chamber in both approaches. To complement these experiments, 3-D numerical modeling of the gas exchange and compression stroke events was done for both HCCI-generating approaches.