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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.

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.

The S40/V50 PZEV (partial zero emission vehicle) model year (MY) 2007 has an upgraded hardware configuration for improved PZEV capability balanced with the best possible customer attributes. The base engine is the Volvo naturally aspirated inline 5-cylinder that, together with new technology, achieves PZEV emission performance with maximum cost efficiency. The engine out emissions were reduced by a newly-developed injection synchronization strategy during engine crank. The reduced number of engine revolutions during crank result in less hydrocarbon (HC) emissions from the cylinder pumping effect prior to the first cylinder combustion. Thanks to the Volvo developed start strategy that during lean lambda operation generates an extreme temperature ramp in the front part of the catalyst in a very early phase after cold start, in combination with a new unique oxygen-sensor installation, catalyst control is started extremely early.

Ion current sensors have high potential utility for obtaining feedback signals directly from the combustion chamber in internal combustion engines. This paper describes experiments performed in a single-cylinder optical engine operated in HCCI mode with negative valve overlap to explore this potential. A high-speed CCD camera was used to visualize the combustion progress in the cylinder, and the photographs obtained were compared with the ion current signals. The optical data indicate that the ions responsible for the chemiluminescence from the HCCI combustion have to be in contact with the sensing electrode for an ion current to start flowing through the measurement circuit. This also means that there will be an offset between the time at which 50% of the fuel mass has burned and 50% of the ion current peak value is reached, which is readily explained by the results presented in the paper.

A naturally aspirated in-line six-cylinder 2.9-litre Volvo engine is operated in Homogeneous Charge Compression Ignition (HCCI) mode, using camshafts with low lift and short duration generating negative valve overlap. Standard port fuel injection is used and pistons and cylinder head are unchanged from the automotive application. HCCI through negative valve overlap is recognized as one of the possible implementation strategies of HCCI closest to production. It is important to gain knowledge of the constraints and limits on the possible operating region. In this work, the emphasis is on investigating how cycle-to-cycle and cylinder-to-cylinder deviations limit the operating region, how these effects change in different parts of the operating region and how they can be controlled. At low load the cycle-to-cycle phenomena cause periodic behavior in combustion timing; together with cylinder deviations this is found responsible for decreasing the operating regime.

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.

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.

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.

A single cylinder, naturally aspirated, four-stroke and camless gasoline engine was operated in gasoline compression ignition mode or otherwise known as homogeneous charge compression ignition (HCCI) mode. The valve timing could be adjusted during engine operation, which made it possible to operate the engine on HCCI combustion in the part-load regime of a 5-cylinder 2.4 liter engine. Cycle to cycle variation in cylinder pressure is caused by the shifts in the auto-ignition timing of the air-fuel mixture. These variations during HCCI combustion were found to, be predictable to some extent, in the sense that an early phased combustion follows a later phased one and vice versa. When the engine was operated in spark ignition mode, a late combustion was correlated with a high gas temperature. No such correlation was found when the engine was operated in HCCI mode.

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.

The new SULEV legislation for passenger cars with gasoline powered engines, which will be introduced with the California LEV II program in the year 2003, requires a further development of the exhaust aftertreatment system. Three fundamentally different system approaches, each with very high efficiency in reducing cold start hydrocarbons, will be discussed in this paper. Vehicle test results will be presented to illustrate the potential of the respective systems towards the SULEV requirements. Durability aspects are also considered since an increased durability of 120 000 and even 150 000 miles is imposed by the legislation.

Numerical simulations of the flow inside a passenger compartment are compared with experimental data obtained from velocity field measurements using Particle Image Velocimetry (PIV). Comparisons are made in the front part of the passenger compartment with the air-distribution system operated in a ventilation mode. The sensitivty of the CFD-model to the boundary conditions was investigated and two different turbulence models were tested. Computations and experiments resulted in similar results for the overall flow field, however, rather large differences were found in the vertical spreading of the jet from the dashboard nozzle. The width of the jet was lower in the measurements than in the simulations. This difference is believed to be caused by the high diffusivity obtained when using a k-epsilon model in combination with an unstructured grid.

A series of experimental studies of diesel spray and combustion characteristics was carried out using circular, elliptic and step orifices. The experiment was performed on a 3-litre single-cylinder engine with optical access. In the engine tests, an elliptic-orifice nozzle with an aspect ratio of approximately 2:1, and a step-orifice nozzle were compared with circular-orifice nozzles. All orifices had sharp-edged inlets. The nozzles were tested at injection pressures extending from 300 to 1300 bar. The nozzles were evaluated in respect of initial spray tip velocity, penetration, spray cone angle, spray width, intermittency and heat-release. Substantial differences were observed in the spray characteristics: At an injection pressure of 300 bar, the spray width increased twice as fast in the minor axis plane of the elliptic orifice and step orifice than the circular orifices.

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.

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.

The aim of this method is to measure emissions from components in the fuel system in a way that is comparable with regulated measurements by Sealed Housing for Evaporative Determination (SHED). In a circuit, constructed as a differential reactor, air is circulated between a test cell and a flame ionization detector (FID) for total hydrocarbon measurement. A test object, i.e. a fuel system component, is filled with fuel and placed in a sealed test cell. Due to the flow characteristic, equilibrium will occur between the air and the fuel evaporated from the surface of the test object. The amount of air consumed in the reactor is compensated by pure air being added to the system. The concentration of hydrocarbon in the circulated air is continuously measured by the FID.

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.