Optimum Design of the Continuously Variable Transmission for a Motorcycle

Many design parameters affect the performance of continuous variable transmissions. This paper presents the optimization of a continuous variable transmission by using the simulated annealing algorithm. The Bessel method of curve fitting and the tensor product method of surface fitting were used to facilitate the discrete fuel consumption, emissions of carbon monoxide (CO) and HC compound of experimental engine data. A compromise method was used to analyze the multi-objective functions. The values for design variables are recommended for further development.

Supercharging of SI Engines Using a New Kind of Screw-Type Supercharger

In result of the permanent endeavor to reduce fuel consumption of vehicle engines, nowadays the implementation of downsizing concepts is being enforced. Thereby the desired nominal engine power can be produced by an engine with lower displacement operating with correspondingly higher charging pressure. Mechanical supercharging as well as turbocharging can be considered as a suitable supercharging method. This paper reports on experimental and simulation results regarding the stationary and transient operation of a four-stroke cycle SI passenger car engine supercharged by a new type of screw-type supercharger. In this manner the load control of the SI engine is performed by a supercharger internal slide valve system. Thus not only the throttling losses will be reduced noticeably, but also expansion work can be regained by this supercharger under certain operating conditions. The results obtained will be compared with those of the turbocharged reference engine.

Engine Torque Non-Uniformity Evaluation Using Instantaneous Crankshaft Speed Signal

The paper presents the development of a methodology for evaluating the torque non-uniformity between the various cylinders of an Internal Combustion Engine (ICE). This non-uniformity can be due, for example, to pathological operating conditions such as misfires or misfuels, as well as to other abnormal operating conditions. Between the nominal torque production and the one corresponding to the absence of combustion there exist, in fact, a series of possible intermediate conditions. Each of them corresponds to a value of produced torque that lies between the nominal value and the one corresponding to the lack of combustion (due for example to statistical dispersion in manufacturing or aging in the injection system). The diagnosis of this type of non-uniformity is a very important issue in today’s engine control strategies design. The use of the developed methodology should in fact allow the control strategy to adopt the appropriate interventions if the diagnosed non-uniformity is related to different behavior of the injectors. In order to evaluate this torque production variability between the various cylinders, information hidden in the instantaneous crankshaft speed fluctuations has been processed using a suitable methodology. The procedure has been validated running a supercharged 2.0 liters V6 engine, and a 1.2 liters L4 engine, in a test cell. During the tests, the in-cylinder pressure signal has been acquired together with the instantaneous engine speed, in order to determine a correlation between speed fluctuations and the indicated torque produced by each cylinder. The actual cylinder by cylinder torque non-uniformity can then be evaluated on-board by processing engine speed. The procedure is able to diagnose the absence of combustion (due for example to a misfire or a misfuel) as well as abnormal combustions that do not necessarily involve lack of combustion, with the accuracy needed for on-board use. Control interventions to injection and ignition time commands of one or more cylinders should in most cases be able to re-establish torque production uniformity.

Engine Friction Characteristics Under Cold Start Conditions

Most studies of engine friction have been carried out at fully-warm operating conditions. Relatively little attention has been given to frictional losses when the engine is running cold, although these can be considerably higher and have a strong influence both on cold-start characteristics and fuel consumption during warm-up. The losses which effect the indicated load on the engine are rubbing losses and loads associated with driving auxiliaries. The equivalent frictional mean effective pressures (fmep) are generally highest during the first seconds of engine operation. These decay rapidly onto a characteristic variation which depends upon oil viscosity, and which fmep follows throughout the warm-up period. The oil viscosity can be evaluated at the bulk temperature of oil in the sump or main gallery. Breakdown motoring tests have been carried out on a series of diesel engines to examine how the friction contribution of various sub-assemblies in the engine contribute to the total and how this varies with temperature and speed. Tests were carried out using a compact cold cell and engine motoring facility. The engine was cold soaked to a target test temperature and then motored to a target speed and the variation of motoring torque recorded. Sets of tests were carried out at several stages of breaking the engine down. This enables the contributions due to the valve train, piston and big end assembly, crankshaft, fuel injection pump, and auxiliary load to be determined.

Simulation of Cylinder Bore Surface Finish Parameters to Improve Laboratory-Scale Friction Tests in New and Used Diesel Oil

The development of alloys, coatings, surface treatments, and lubricants for improved cylinder liners and rings has historically included friction and wear testing. The correlation of results from motored engines or laboratory-scale tribotests with those from full-scale, fired engines remains a subject of contention. Attempts to develop valid engine wear simulators have met with varying degrees of success. Complexities in understanding and duplicating the relevant contact conditions in fired engines have challenged the designers of sub-scale, simulative laboratory tests. The current paper describes one aspect of this problem; namely, simulating the cylinder bore surface finish for use in bench tests. A rapid method to prepare cast iron test specimens that have similar surface roughness parameters to a production cast iron cylinder liner has been developed. To compare the sliding response of simulated liners with actual liners, cast iron specimens were friction-tested in both new and used 15W40 commercial diesel engine oil, in mineral oil, and without liquid lubrication. A reciprocating, ball-on-flat testing machine was used with test lengths that ranged from 100 to 20,000 cycles. Kinetic friction coefficient data compared favorably between the simulated cylinder liner specimens and actual cylinder liner segments. The friction coefficients obtained in tests with different lubricants on the simulated surfaces were related through a second-degree polynomial to the change in arithmetic average roughness that occurred during running-in. Additional elements of the fired engine environment will be added in the next stages of this research to determine the degree of complexity that is needed to obtain increasingly better simulations.

Improvement of the Dynamic Characteristic of an Automotive Engine by a Turbocharger Assisted by an Electric Motor

Increase of the mean effective pressure in an automotive Diesel engine is generally the consequence of the turbocharging and subsequent charge cooling of the working medium. A problem of poor performance during the engine speed and load change is attributed to the nature of energy exchange between the engine and the turbocharger. Filling of the intake and exhaust manifolds, consequent increase of the pressure and acceleration of the rotating components of the turbocharger require a certain period of time. Dynamic performance of the turbocharger can be substantially improved by the assistance of an electric motor attached directly to the turbo shaft. A new concept of asynchronous electric motor with a very thin rotor was applied to support the turbocharger during the transient regimes of the engine. Experimental work for matching an electrically assisted turbocharger to an engine is rather expensive; it was therefore decided to determine general characteristic of the electric motor separately by experiments, whereas transient response of the turbocharged and intercooled Diesel engine was simulated by a zero-dimensional filling and emptying computer simulation method. A lot of experimentally obtained data and empirical formulae for the compressor, gas turbine, flow coefficients of the engine valves, intercooler, high pressure fuel pump with the pneumatic control device (LDA), combustion parameters etc. were applied to overcome deficiency introduced by the zero-dimensional simulation model. As the result a reliable and accurate program compatible with the experimental results in steady and transient engine operation was developed and is presented in the work. Faster transient response of the engine was obtained by applying an electric motor to assist the turbocharger; a few versions were introduced in the simulation program and were also analysed in the work.

Preliminary Investigation of Dilution Strategies to Control Engine Torque During Transient Events

A continuously variable transmission (CVT) allows a powertrain controller the freedom to develop a required output power at a range of engine torque and speed conditions. This flexibility can be used to maximise fuel efficiency. Due to low frictional and pumping losses a gasoline engine’s fuel efficiency is maximised at low speed, high torque conditions. However due to the reduced torque margin available, controlling a gasoline engine in this region compromises transient vehicle response. Dilution torque control, using EGR or lean burn, has the potential to maintain the economy gains available using a CVT powertrain whilst improving a vehicle’s driveability. This paper introduces preliminary work that has been undertaken to investigate the potential of charge dilution to control steady state engine torque. A test rig has been developed based around an engine fitted with variable cam phasing and an external EGR system. The paper contains a discussion of initial results of a lean dilution test program used to demonstrate the principle.

Swirl Turbocharging Exhaust System and its Application Study

A novel modular single exhaust manifold called swirl turbocharging exhaust system is described. The flow field was modeled and compared with the flow behavior in MPC system. Numerical calculation results of the manifold flow show that its flow field characteristics were different from that of the MPC’s. To investigate the efficient two swirl turbocharging exhaust systems were designed and applied to two turbocharged diesel engines respectively. The test results reveal that both engines with the new type turbocharging system have promising performance.

Dynamic Response of Automotive Catalytic Converters to Variations in Air-Fuel Ratio

The automotive catalytic converters, which are employed to reduce engine exhaust emissions, operate in transient conditions under all modes of operation. The fluctuation in air-fuel ratio is a major contributor to these transients. The consideration of these transients is essential in accurate modeling of catalyst operation during actual driving conditions. In this work, a numerical investigation is carried out to comprehend the dynamic response of three-way catalytic converters subjected to changes in air-fuel ratio. The mathematical model considers the coupling effect of heat and mass transfer with the catalyst reactions as exhaust gases flow through the catalyst. The converter dynamic response is studied by considering a converter operating under steady conditions, which is suddenly subjected to air-fuel ratio variations. Two types of imposed fluctuations (sinusoidal and step changes) are considered. The catalyst response is predicted by using a detailed chemical mechanism. The paper elucidates the effect of air-fuel modulations on the catalyst HC, CO, and NO conversion efficiencies.

Analytical Modeling of Cylinder Head Distortion to Eliminate Intake Valve Burning

Intake valve seat recession and subsequent valve leakage were experienced during the late development phase of a new DOHC aluminum engine. This type of failure was not observed in the earlier development phase during engine break-in. To resolve this valve burning issue, a three-dimensional finite element model was used to study the thermal/mechanical behavior of this engine. A parallel experimental program was conducted to evaluate the effect of the hardware changes between the early and late engine development phases on engine performance. The experimental effort also provided engine temperature and measured distortion data for validating the analytical model. The finite element analysis was able to identify the root cause of this condition and to propose structural modifications to remedy this problem rapidly by predicting the distortion and stress distribution within the cylinder head.