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Bushing elasticity is one of the most important compliance factors that significantly influence driving behavior. The deformations of the bushings change the wheel orientations under external forces. Another important factor of bushing compliance is to provide a comfortable driving experience by isolating the vibrations from road irregularities. However, the driving comfort and driving dynamics are often in conflict and need to be balanced in terms of bushing compliance design. Specifically, lateral force steer and brake force steer are closely related to safety and stability and comprises must be minimized. The sensitivity analysis helps engineers to understand the critical bushing for certain compliance attributes, but optimal balancing is complicated to understand. The combination of individual bushing stiffness must be carefully set to achieve an acceptable level of all the attributes.

Squeak and rattle (S&R) are nonstationary annoying and unwanted noises in the car cabin that result in considerable warranty costs for car manufacturers. Introduction of cars with remarkably lower background noises and the recent emphasis on electrification and autonomous driving further stress the need for producing squeak- and rattle-free cars. Automotive manufacturers use several road disturbances for physical evaluation and verification of S&R. The excitation signals collected from these road profiles are also employed in subsystem shaker rigs and virtual simulations that are gradually replacing physical complete vehicle test and verification. Considering the need for a shorter lead time and the introduction of optimisation loops, it is necessary to have efficient and inclusive excitation load cases for robust S&R evaluation.

While striving for more fuel-efficient vehicles, all possible measures are considered to increase the efficiency of the combustion engine powertrain. 48V mild hybrid technology is one such measure, SIDI (Spark Ignited Direct Injection) engines with Miller technology are another, while recovering energy from the engine’s waste heat (WHR) is yet another option. In this paper, results will be published from an advanced engineering project at Volvo Cars including all of these components. An ethanol based Organic Rankine Cycle (ORC) WHR-system was successfully built around a 4-cylinder, 2.0 litre SIDI-engine, including 48V mild hybrid technology, with vehicle packaging considered. A dedicated control system was also developed for the ORC system including communication between it and the engine. The ORC system uses the engine exhaust as the heat source, for which a purpose-built evaporator was designed and built to fit in the vehicle tunnel.

Since several decades, passenger cars and light duty vehicles (LDV) with spark-ignited engines reach full pollutant conversion during warm up conditions; the major challenge has been represented by the cold start and warming up strategies. The focus on technology developments of exhaust after treatment systems have been done in the thermal management in order to reach the warm up conditions as soon as possible. A new challenge is now represented by the Real Driving Emission (RDE) Regulation as this bring more various, and not any longer cycle defined, cold start conditions. On the other hand, once the full conversion has been reached, it would be beneficial for many Exhaust After Treatment System (EATS) components, e.g. for overall durability if the exhaust gas temperature could be lowered. To take significant further emission steps, approaching e.g. zero emission concepts, we investigate the use of Electrical Heating Catalyst (EHC) also including pre-heating.

A two-state forward dynamic programming algorithm is evaluated in a series hybrid drive-train application with the objective to minimize fuel consumption when look-ahead information is available. The states in the new method are battery state-of-charge and engine speed. The new method is compared to one-state dynamic programming optimization methods where the requested generator power is found such that the fuel consumption is minimized and engine speed is given by the optimum power-speed efficiency line. The other method compared is to run the engine at a given operating point where the system efficiency is highest, finding the combination of engine run requests over the drive-cycle that minimizes the fuel consumption. The work has included the engine torque and generator power as control signals and is evaluated in a full vehicle-simulation model based on the Volvo Car Corporation VSIM tool.

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.

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.

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.

The aerodynamic drag, fuel consumption and hence CO2 emissions, of a road vehicle depend strongly on its flow structures and the pressure drag generated. The rear end flow which is an area of complex three-dimensional flow structures, contributes to the wake development and the overall aerodynamic performance of the vehicle. This paper seeks to provide improved insight into this flow region to better inform future drag reduction strategies. Using experimental and numerical techniques, two vehicle shapes have been studied; a 30% scale model of a Volvo S60 representing a 2003MY vehicle and a full scale 2010MY S60. First the surface topology of the rear end (rear window and trunk deck) of both configurations is analysed, using paint to visualise the skin friction pattern. By means of critical points, the pattern is characterized and changes are identified studying the location and type of the occurring singularities.

Vehicle dynamics development relies on subjective assessments (SA), which is a resource-intensive procedure requiring both expert drivers and vehicles. Furthermore, development projects becoming shorter and more complex, and increasing demands on quality require higher efficiency. Most research in this area has focused on moving from physical to virtual testing. However, SA remains the central method. Less attention has been given to provide better tools for the SA process itself. One promising approach is to introduce computer-tablets to aid data collection, which has proven to be useful in medical studies. Simple software solutions can eliminate the need to transcribe data and generate more flexible and better maintainable questionnaires. Tablets’ technical features envision promising enhancements of SA, which also enable better correlations to objective metrics, a requirement to improve CAE evaluations.

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. Realistic combinations of energy saving measures were evaluated regarding the total energy use for vehicle interior climate using a one dimensional (1D) simulation model. The 1D simulation model included sub models of the passenger compartment, the air-handling unit, the Air Conditioning (AC) system, engine and engine cooling system. A test cycle representative for real-world conditions was developed. The test cycle included tests in cold, intermediate and warm conditions and the results were weighted with the estimated use in each condition.

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.

The focus on engine thermal management is rapidly increasing due to the significant effect of heat losses on fuel consumption, engine performance and emissions. This work presents a time resolved, high resolution 3D engine heat balance model, including all relevant components. Notably, the model calculates the conjugated heat transfer between the solid engine components, the coolant and the oil. Both coolant and oil circuits are simultaneously resolved with a CFD solver in the same finite volume model as the entire engine solid parts. The model includes external convection and radiation. The necessary boundary conditions of the thermodynamic cycle (gas side) are mapped from a calibrated 1D gas exchange model of the same engine. The boundary conditions for the coolant and at the oil circuits are estimated with 1D models of the systems. The model is calibrated and verified with measurement data from the same engine as modeled.

Previous research on both small-scale and full-scale vehicles shows that base extensions are an effective method to increase the base pressure, enhancing pressure recovery and reducing the wake size. These extensions decrease drag at zero yaw, but show an even larger improvement at small yaw angles. In this paper, rear extensions are investigated on an SUV in the Volvo Cars Aerodynamic Wind Tunnel with focus on the wake flow and on the unsteady behavior of the surface pressures near the base perimeter. To increase the effect of the extensions on the wake flow, the investigated configurations have a closed upper- and lower grille (closed-cooling) and the underbody has been smoothed with additional panels. This paper aims to analyze differences in flow characteristics on the wake of an SUV at 0° and 2.5° yaw, caused by different sets of extensions attached to the base perimeter. Extensions with several lengths are investigated with and without a kick.

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.

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.

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.

In modern vehicles, each system must meet tough demands to fulfill the many different attribute requirements, design constraints and manufacturing limitations. It becomes difficult and time-consuming to find an optimal and robust design using a traditional engineering process. Volvo Cars has for several years been using Multi-Disciplinary Optimization, MDO, that basically shows the customer attributes levels, such as NVH, ride comfort, and driveability as a function of different parameter configurations. This greatly facilitates project team understanding of the limitations and possibilities of the different systems, and has become a key enabler to achieving a good balance between different attributes. Traditionally, this type of comprehensive Design of Experiments (DOE) optimization demands huge time and computer resources. Frequently, experimental designs will not fulfill manufacturing limitations or attribute targets, making this decision process slow, tedious, and fruitless.

The durability peak load events Driving over a curb and Skid against a curb have been simulated in Adams for a Volvo S80. Simulated responses in the front wheel suspension have been validated by comparison with measurements. Due to the extreme nature of the peak load events, the component modeling is absolutely critical for the accuracy of the simulations. All components have to be described within their full range of excitation. Key components and behaviors to model have been identified as tire with wheel strike-through, contacts between curb and tire and between curb and rim, flexibility of structural components, bump stops, bushings, shock absorbers, and camber stiffness of the suspension. Highly non-linear component responses are captured in Adams. However, since Adams only allows linear material response for flexible bodies, the proposed methods to simulate impact loads are only valid up to small, plastic strains.