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Engine stability at idle is an important factor that influences the behaviour of an I.C., S.I. engine, in terms of fuel efficiency, exhaust gas emissions and customer comfort. In particular, the increasing daily use of vehicles in urban traffic bestows more and more importance on the engine idle quality. The engine idle quality is perceived by the user as the constancy of noise tone, low vibrations level and absence of sudden speed drop, noticeable on the steering wheel, gear shift lever, and seat [1]. Combustion characteristics play an essential role on the overall engine quality level at idle. It is important to have an estimation of the engine behaviour in this condition during the engine pre-development phase. While the fluid-dynamic calculation codes mean the engine performance at full load can be predicted, but the modelling of part load and idle behaviour is very difficult.

This paper is a description and analysis of the behaviour of a purely conceptual mechanism or system which is able to vary continuously both the opening and closing angle of internal combustion engine valves which are operated by a double overhead camshaft arrangement of substantially conventional type. The mechanism is interposed between the camshaft and the drive from the crankshaft and is able to vary the instantaneous phase of the camshaft so as to permit each cam to spend a longer or shorter time in contact with its tappet for a given engine speed. There is an implicit acceptance in the paper that published work on variable valve timing has demonstrated its desirability if the full potential of the normally aspirated internal combustion engine is to be realised. The difficulties of producing suitable mechanisms, as shown by the long history of (largely unsuccessful) interest in the subject, is acknowledged.

BorgWarner has developed a continuously variable vane style VCT camshaft phaser that, differing from the oil pressure actuated phasers in production, utilizes camshaft torque energy, not oil pump flow, to actuate. This VCT phaser has several distinct advantages, low oil flow requirements and fast response rates even at low RPM. The low oil flow requirement, allows this Cam Phaser to easily adapt to existing engine platforms without major engine modifications or increases in oil pump size. For new engine designs a smaller oil pump can be selected and thereby improve overall engine efficiency. Since the phaser responds to camshaft torque energy and actuates independent of oil pressure, fast response rates are available from idle on up through the engine operating range, allowing the engine calibrator to adopt a more aggressive approach to camshaft timing.

This paper describes the principle of operation of a novel capacitance based transducer which is employed in a bench mounted turbocharger to identify oil leakage from the “piston-ring” seal at the turbine end of the shaft. Some preliminary data relating to “vacuum-to-leak” conditions are presented along with graphs which illustrate the filling of the transducer. Finally, the design modifications which will be required if the transducer is to be used for leak detection in a turbocharger mounted on a firing engine, are briefly outlined.

Till recently supercharging was the most accepted technique for boost solution in gasoline engines. Recent advents in turbochargers introduced turbocharging technology into gasoline engines. Turbocharging of gasoline engines has helped in powertrains with higher power density and less overall weight. Along with the advantages in performance, new challenges arise, both in terms of thermal management as well as overall acoustic performance of powertrains. The study focuses mainly on NVH aspects of turbocharging of gasoline engines. Compressor surge is a most common phenomenon in turbochargers. As the operating point on the compressor map moves closer to the surge line, the compressor starts to generate noise. The amplitude and frequency of the noise depends on the proximity of the operating point to the surge line. The severity of noise can be reduced by selecting a turbocharger with enough compressor surge margin.

Results of a case study in which an unusual liner wear pattern is seen to form within the cylinders of a large marine diesel engine are presented. Analysis of the wear patterns and the wear surfaces are also presented which reveal that the maximum wear corresponds to regions on the liner where “varnish” or “lacquer” films appear to build up from decomposition products of the fuel and lubricants employed. Possible reasons for such wear and film formation are discussed, and compared with frictional and thermal analyses of the ring-liner contacts under operating conditions, with and without the presence of lacquer films. Preliminary results suggest that such films can act as insulation layers to frictionally generated heat between rings and liner, and if allowed to become thick enough can lead to scuffing.

A dimensionless relationship that estimates the maximum bearing load of a 4-cylinder 4-stroke in-line engine has been found. This relationship may assist the design engineer in choosing a desired counterweight mass. It has been demonstrated that: 1) the average bearing load increases with engine speed and 2) the maximum bearing load initially decreases with engine speed, reaches a minimum, then increases quickly with engine speed. This minimum refers to a transition speed at which the contribution of the inertia force overcomes the contribution of the maximum pressure force to the maximum bearing load. The transition speed increases with an increase of counterweight mass and is a function of maximum cylinder pressure and the operating parameters of the engine.

Growing awareness about CO2 emissions and their environmental implications are leading to an increase in the importance of thermal efficiency as criteria to design internal combustion engines (ICE). Heat transfer to the combustion chamber walls contributes to a decrease in the indicated efficiency. A strategy explored in this study to mitigate this efficiency loss is to promote low swirl conditions in the combustion chamber by using low swirl ratios. A decrease in swirl ratio leads to a reduction in heat transfer, but unfortunately, it can also lead to worsening of combustion development and a decrease in the gross indicated efficiency. Moreover, pumping work plays also an important role due to the effect of reduced intake restriction to generate the swirl motion. Current research evaluates the effect of a dedicated injection strategy to enhance combustion process when low swirl is used.

The crank noise of a motorcycle often spoils the product value because of its annoying sound. Many approaches have been tried to cope with this troublesome issue. In recent years, a CAE-based method has been adopted to evaluate new designs for engines and to propose design changes that determine any identified issue. But it was a challenge to make an accurate CAE model due to the relatively high frequency characteristics of the noise generated by ball bearing-supported crankshafts. This paper presents the virtual modeling of a single-cylinder engine of a motorcycle that succeeds in identifying the mechanism behind the generation of annoying noise. Furthermore, different possible design changes were evaluated in order to determine the issue. A combined experimental and numerical approach was adopted to obtain the necessary accuracy. Experimental data were used to identify important parameters that determine the engine behavior and thus are critical to the modeling of such an engine.

Experimental work has demonstrated that spark ignition engine exhaust emissions can be controlled through basic modification of the combustion process, and that such control can be achieved without serious compromise of the efficiency of fuel utilization. The combustion process investigated in this work is designed to exploit the finite time dependence of nitric oxide formation in high temperature combustion products. Through use of a divided combustion chamber it has been possible to quench nitric oxide formation reactions so that little nitric oxide formation occurs. Further it has been possible to simultaneously promote complete oxidation of hydrocarbons and carbon monoxide in combustion products. The combustion process, therefore, results in total control of exhaust emissions.

The use of cycle simulation computer programs has become an established part of turbocharged diesel engine research and development. However, the utility of these programs has in the past been limited by the need for combustion information at the operating point. This difficulty has been overcome by the development of an empirical correlation simulating the combustion process (heat release) via an analytical expression whose governing parameters are linked to in-cylinder conditions. A method of deriving the governing parameters from only a minimum of experimental test data is presented, but enabling performance to be predicted over a wide range of operating conditions. The use of the combustion correlation enables the effects of changing ambient conditions, turbocharger match, valve timing and other engine design parameters to be predicted automatically, and includes their influence on combustion as well as the turbocharging process.

A Spark-ignition combustion correlation is presented that links the fuel burning rate with in-cylinder vaules of temperature, pressure, fuel-air equivalance ratio, speed, ignition timing and residual gas-fraction. The correlation is designed to be used in a multi-cylinder engine simulation to study the influence of manifold, valve, supercharging and turbocharging systems design on performance. It is shown how the correlation permits transient performance predictions for a turbocharged engine.

In previous papers a complete simulation model of the combustion in a gasoline rotary engine has been described. This combustion model, developed at the University of Gent and UMIST (University of Manchester Institute of Science and Technology), is based on a turbulence enhancement factor for the flame in various zones of the combustion chamber. The purpose of this paper is to give a description of the modifications of the model for a homogeneous natural gas rotary engine. The real geometry of the combustion chamber is incorporated In the model. Calculations are executed for different geometries of rotary engines (especially different positions and shapes of the recess in the rotor). Different formulas of the laminar flame speed for natural gas are examined. The turbulent flame speed is calculated with a turbulence factor or with a turbulence intensity factor. A correlation between the engine conditions and the turbulence intensity is proposed.

Several models for the evaluation of Gross Heat Release are often used in literature. One of these is the First Law - Single Zone Model (FL-SZM), derived from the First Law of Thermodynamics. This model presents a twice advantage: first it describes with accuracy the physic of the phenomenon (charge heat release during the combustion stroke and heat exchange between gas and cylinder wall); second it has a great simplicity in the mathematical formulation. The current paper deals with the implementation of a mathematical model, based on FL-SZM, to study the heat release due to the combustion phenomena in Internal Combustion Engines (ICEs). For purposes of chemical kinetic calculations, many of the major species have been included into the combustion products. In particular, seven gases (i.e. H2O, CO2, H2, O2, N2, CO and Ar) may also be assumed in chemical equilibrium.

A new combustion pressure sensor capable of measuring the combustion pressure in an engine cylinder has been developed. This combustion pressure sensor has been used for control of the advanced lean combustion engine in TOYOTA 1992 model (Oct. 1992). The control system is useful for improvement of energy consumption efficiency and reduction of emissions from commercial cars. The successfully designed combustion pressure sensor has excellent features of low impedance and good linearity. It has been realized with the smallest number of components and reasonable cost. This paper describes the principle, structure and basic characteristics of the combustion pressure sensor.

Lucas Diesel Systems has designed a Common Rail fuel injection system for modern high speed direct injection diesel engines. The components of the system include a new high pressure pump, a rail, and injectors which accommodate a rapid control valve within the envelope of a 17 mm diameter. The injection pressure can be controlled at all engine operating conditions within the range of 150 to 1600 bar. This paper describes the major components of this system, which is designed to provide multiple injections into the combustion chamber during each engine cycle with a good control of small deliveries. In comparison with cam-driven diesel injection systems, the common rail approach needs some additional control and supervision strategies; for example, detection of small leakages due to high pressure at the needle seat throughout the engine cycle.

The paper discusses the concept, specification and overall performance of a 10 kW electric power range extender suitable for electric plug-in and series hybrid vehicles, based on a single cylinder, high speed, four stroke internal combustion engine, tested and developed at Istituto Motori CNR of Italy. This unit has been conceived from the beginning as a compact on board recharging system for the mentioned kind of means, and especially for city cars and small commercial vehicles. The paper starts by defining some characteristics, advantages and drawbacks of an electric city car, followed by the criteria adopted to characterize the nominal power of the range extender. Then, the ratio which leaded to the adoption of a single cylinder internal combustion engine is discussed, followed by an explanation of the main design characteristics of the whole unit.

Setting the correct valve timing and lift based on the operating speed will be the key to achieving good volumetric efficiency and torque. Continuously variable valve timing systems are the best choice but are too expensive. In this work a novel two stage variable valve actuation system was conceived and developed for a small single cylinder three wheeler spark ignition engine. The constraints were space, cost and complexity. The developed system uses one cam for low speeds and another cam that has a higher lift and duration for high speeds. The shift between the cams occurs through the mechanism even as the engine runs by the operation of a stepper motor which can be connected to the engine controller. A one dimensional simulation model validated with experimental data was used to predict the suitable valve timings and lifts in low and high speed ranges. Two profiles were then selected.

The high temperature fatigue behaviors of three cast aluminum alloys used for cylinder head fabrication - 319, A356 and AS7GU - are compared under isothermal fatigue at room temperature and elevated temperatures. The thermo-mechanical fatigue behavior for both out-of-phase and in-phase loading conditions (100-300°C) has also been investigated. It has been observed that all three of these alloys present a very similar behavior under both isothermal and thermo-mechanical low-cycle fatigue. Under high-cycle fatigue, however, the alloys A356 and AS7GU exhibit superior performance.

Low speed pre-ignition (LSPI) in downsized spark-ignition engines has been studied for more than a decade but no definitive explanation has been found regarding the exact sources of auto-ignition. No single mechanism can explain all the occurrences of LSPI and that each engine should be considered as a particular case supporting different conditions for auto-ignition. In a different context, dual fuel Diesel-Methane engines have been more recently studied in large to medium bore compression ignition engines. However, if Dual Fuel combustion is less knock sensitive, LSPI remains one of the main limitations of low-end torque also for dual fuel engines. Indeed, in some cases, premature ignition of CNG can be observed before the Diesel pilot injection as LSPI can classically be observed before the spark in gasoline engines. This article aims at highlighting the similarities and discrepancies between LSPI phenomena in SI gasoline and dual fuel engines.