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A new fully mechanical valve timing mechanism for continuous control of valve lift, duration and phase angle has been developed. Any valve lift and duration between zero and the maximum value may be obtained by rotating an adjustable control shaft and ramp. Total valve deactivation is possible and intake valve throttling may be used. The operation principle and several applications of the mechanism are presented. The kinematics and dynamics of the mechanism have been studied and the critical forces and stresses have been calculated. Also the tribology of the mechanism is dealt with to check possible lubrication problems. Simulation has been used to find the dynamic properties and loads of the mechanism. The mechanism has been tested in two single cylinder intake valve prototypes using the two-lever rocker and drag lever principles.

In this paper various methods of studying in-cylinder heat transfer in small displacement two-stroke engines are presented and compared. First of all, the mistakes that can be caused by the application of steady heat transfer models to the study of such a complex phenomenon are considered. After the demonstration that an ordinary convective heat transfer model determines mistakes in the evaluation of the thermal load, three-dimensional analysis and improved heat transfer models are considered. The multidimensional code Fluent is used for the 3-D fluid mechanics simulation. Numerical analysis evidences the importance of the non-uniformity of the gas temperature inside the cylinder. The improved models considers the fact that heat transfer during compression and expansion is out of phase with bulk gas-wall temperature difference and that the great part of the heat transfer is linked to the combustion.

This paper focused experimental and theoretical studies on the effects of air-head stratified scavenging and leaner combustion on reducing hydrocarbon emission and improving thermal efficiency of two-stroke cycle spark-ignition engine. The result showed that the amount of short-circuiting mixture with a conventional Schnurle scavenging two-stroke cycle engine was reduced from 30% to 9% with the air-head stratified scavenging two-stroke cycle engine which was developed in this study. Thermal efficiency was improved from 13.6% to 20.6%. As the result, the engine with air-head stratified scavenging and leaner combustion in this study can conform to the California Air Resources Board (CARB) 1999 or tier 2 emission standards regarding THC, CO and NOx emission.

The Lysholm compressors is developed and is produced as a high-efficiency supercharger optimum for use in automotive engines. This paper describes a second-generation Lysholm compressor that has a self-contained lubrication system and a low inertia, and describes the systems connecting the engine and the Lysholm compressor.

Time-averaged temperatures at critical locations on the piston of a direct-fuel injected, two-stroke, 388 cm3, research engine were measured using an infrared telemetry device. The piston temperatures were compared to data [7] of a carbureted version of the two-stroke engine, that was operated at comparable conditions. All temperatures were obtained at wide open throttle, and varying engine speeds (2000-4500 rpm, at 500 rpm intervals). The temperatures were measured in a configuration that allowed for axial heat flux to be determined through the piston. The heat flux was compared to carbureted data [8] obtained using measured piston temperatures as boundary conditions for a computer model, and solving for the heat flux. The direct-fuel-injected piston temperatures and heat fluxes were significantly higher than the carbureted piston. On the exhaust side of the piston, the direct-fuel injected piston temperatures ranged from 33-73 °C higher than the conventional carbureted piston.

The performance of a turbocharger compressor with a range of low solidity vaned diffusers close coupled to the collecting volute is presented. The vaned diffusers were designed with a solidity of 0.5, an inlet radius ratio of approximately 1.4, and a discharge radius ratio of 1.65 so that the flow discharged directly into the collecting volute. The experimental investigation presents the basic performance of the turbocharger together with the specific pressure recovery developed in the vaneless space, the vaned diffuser, and the collecting volute. The effect of alternative vane designs on the matching and performance of the collecting volute is discussed.

VAST is a variable timing system developed for spark-ignition and compression-ignition engines. It makes variable control of the intake and exhaust valves possible for SC and OHC engines. The system is based on the principle of the purely mechanical effect of the cam's irregular angular speed. It makes it possible to vary the valve opening angle (up to approx. 50° crankshaft angle) and the spread (up to approx. 30° crankshaft angle) continuously for each valve lift movement. When the valve opening period is prescribed, longer time profiles can be realized with this system than with any mechanical VVT system known to the authors. The valve lift is influenced directly at the cam, which means this system can be used with all types of known valve gear- both for engines/cylinder heads with just one camshaft and for multi-valve cylinder heads with two camshafts. The system is being tested on functioning spark-ignition and compression-ignition engines.

The performance of a centrifugal compressor with a range of low solidity diffuser vanes is discussed. The effect of vane leading and trailing edge angle was investigated while maintaining a basic design with 10 vanes and a solidity of 0.69. The diffuser vanes were designed with a circular arc camberline and a specified leading edge angle. The trailing edge angle was varied by specifying a range of angles through which the vanes turned. Vanes with leading edge angles of 65°, 70°, 75°, and 80° were considered together with vane turning angles of 10°, 15° and 20°. All results are compared with those obtained with the standard vaneless diffuser configuration. Despite the low solidity configuration none of the vane designs provided a broad operating range and it would be necessary to deploy a variable geometry arrangement.

To improve the performance of the centrifugal compressor for automotive turbocharger, it is essential to understand the complicated flow phenomena caused by its complex blade geometry. Authors carried out the detailed flow measurement of the centrifugal compressor impeller uisng Laser Doppler Velocimeter (LDV). The test impeller is a 9.1 times enlarged model of real turbocharger. In result authors found out the low velocity region is grown up at the suction surface of the inducer according to the reduction of flow rate. The experimental data are compared with the three dimensional (3D) viscous flow analysis and acceptable agreement was observed.

A modelling study is presented in this paper, whose objective is to obtain design criteria for optimum layouts and dimensions of exhaust manifolds in automotive engines. The first step has been the characterisation of the pulsating flow phenomena in the exhaust manifold, focusing on the pressure wave propagation process and on the interaction between cylinders across the manifold. Two relevant phenomena have been studied: the reflection of under-pressure pulses at pipe junctions and open ends, and the interference between exhaust processes of different cylinders. These phenomena have been characterised respectively by non-dimensional parameters, related to the layout and dimensions of the manifold. A parametric modelling study has been performed in order to evaluate the effects of the manifold dimensions on the engine performance. The work has been focused on a four-cylinder engine with a four-branch manifold.

An important paradigm for the modelling of naturally aspirated (NA) spark ignition (SI) engines for control purposes is the Mean Value Engine Model (MVEM). Such models have a time resolution which is just sufficient to capture the main details of the dynamic performance of NA SI engines but not the cycle-by-cycle behavior. In principle such models are also physically based, are very compact in a mathematical sense but nevertheless can have reasonable prediction accuracy. Presently no MVEMs have been constructed for intercooled turbocharged SI engines because their complexity confounds the simple physical understanding and description of such engines. This paper presents a newly constructed MVEM for a turbocharged SI engine which contains the details of the compressor and turbine characteristics in a compact way. The model has been tested against the responses of an experimental engine and has reasonable accuracy for realistic operating scenarios.

Results of computations of flows, sprays and combustion performed in an optically- accessible Diesel engine are presented. These computed results are compared with measured values of chamber pressure, liquid penetration, and soot distribution, deduced from flame luminosity photographs obtained in the engine at Sandia National Laboratories and reported in the literature. The computations were performed for two operating conditions representing low load and high load conditions as reported in the experimental work. The computed and measured peak pressures agree within 5% for both the low load and the high load conditions. The heat release rates derived from the computations are consistent with expectations for Diesel combustion with a premixed phase of heat release and then a diffusion phase. The computed soot distribution shows noticeable differences from the measured one.

The Homogeneous Charge Compression Ignition (HCCI) is the third alternative for combustion in the reciprocating engine. Here, a homogeneous charge is used as in a spark ignited engine, but the charge is compressed to auto-ignition as in a diesel. The main difference compared with the Spark Ignition (SI) engine is the lack of flame propagation and hence the independence from turbulence. Compared with the diesel engine, HCCI has a homogeneous charge and hence no problems associated with soot and NOX formation. Earlier research on HCCI showed high efficiency and very low amounts of NOX, but HC and CO were higher than in SI mode. It was not possible to achieve high IMEP values with HCCI, the limit being 5 bar. Supercharging is one way to dramatically increase IMEP. The influence of supercharging on HCCI was therefore experimentally investigated. Three different fuels were used during the experiments: iso-octane, ethanol and natural gas.

A new reaction scheme for NOx production is incorporated into a steady state quasi-dimensional engine combustion simulation. The reaction kinetics includes 67 reactions and 13 chemical species, and assumes equilibrium concentration for all other chemical species. The General Engine SIMulation (GESIM) developed by Ford Motor Company is used to model the engine cycle. The new reaction scheme is a super-extended Zel'dovich mechanism (SEZM) which predicts NOx formation levels to within 10% of engine test data for several engines, whereas the 3 reaction, extended Zel'dovich mechanism (EZM) is shown to have errors of approximately 50% or more for similar conditions. Analytical engine mapping, under NOx constrained calibration, requires accurate modeling of NOx emissions over varying engine operating conditions.

The paper describes recent advances in the research work concerning the 1-d fluid dynamic modeling of unsteady flows in i.c. engine pipe systems. A comprehensive simulation model has been developed, which is based on different numerical techniques for the solution of the fundamental conservation equations. Classical (MacCormack method plus TVD algorithm) and innovative (the CE-SE method, the discontinuous Galerkin FEM) shock-capturing schemes have been compared, considering the shock-tube problem and the shock-turbulence interaction problem. Moreover, the tracking of the chemical species along the intake and exhaust duct systems has been investigated, introducing the species continuity equations in the numerical model. The engine test case reported in the paper points out the predicted transport of chemical species in the ducts.

Modern engine management systems increasingly rely on on-line identification schemes. These are used either for self-tuning regulators or the rapid parametrization of controllers. In this paper the on-line parameter identification of the wall-wetting dynamics is studied in detail. The identification is performed by exciting the fuel path dynamics of the engine at a constant operating point. The amount of fuel injected serves as input and the air-to-fuel ratio, which is measured with a linear oxygen sensor, as output. In order to gain precise information about the amount of fuel in the cylinder, a new measurement concept is used. For one, the placement of the lambda sensor close to the exhaust valve minimizes the effects of gas mixing on the measurements. Additionally, by an appropriate collection of the data, the sensor dynamics are bypassed. This is also illustrated by a measurement with a very fast NOx sensor.

Diesel engine control has already become complex, and in order to meet future emissions standards (such as Euro 4) it is likely to be the control system that will provide the needed performance increment. Common rail fuel injection offers yet more degrees of freedom which will need to be exploited as new emissions standards emerge. Whatever the emissions standards, there is a need to reduce risk at the earliest stages in the development of the powertrain. This will involve early and extensive simulation of the powertrain including its control system, sensors and actuators. What is the best way to achieve this using current tools? The result lies in a combination of a phenomenological model of the engine and a flexible controls environment. To illustrate the principles of developing prototype control systems, we will use the example of the CPower environment, which is a combination of a detailed engine simulation code (GT-Power) and the Simulink simulation environment.

Electronic throttle control is increasingly being considered as a viable alternative to conventional air management systems in modern spark-ignition engines. In such a scheme, driver throttle commands are interpreted by the powertrain control module together with many other inputs; rather than directly commanding throttle position, the driver is now simply requesting torque - a request that needs to be appropriately interpreted by the control module. Engine management under these conditions will require optimal control of the engine torque required by the various vehicle subsystems, ranging from HVAC, to electrical and hydraulic accessories, to the vehicle itself. In this context, the real-time estimation of engine and load torque can play a very important role, especially if this estimation can be performed using the same signals already available to the powertrain control module.

In this paper, the prototypes of electric cars done by the Engineering & Infrastructure Transportation Area in the Department of Mechanical Engineering of the University of Zaragoza is presented. The project started in 1993, the initial stage started doing calculation and construction of prototype I which was used as a technological demonstrator. The prototype I, was a very simplified electric vehicle with particular performance qualities. Prototype II has the features of an urban car comparable to the current combustion cars for urban purposes. A program of testing will be done in order to find problems that can be corrected for the prototype III, in which all the parameters analyzed will be corrected for a serial manufacture.

This paper describes SHEV, a computer program created to simulate hybrid electric vehicles. SHEV employs the time-stepping technique in order to evaluate energy flow in series hybrids, and makes use of a unique method in order to speed up the fuel economy estimation. This estimation method is a refinement of the “state of charge matching” method and is explained in detail. The graphic user interfaces employed in SHEV make it easy to use and give it a look similar to regular Windows‚ applications. This paper also gives some examples of the screens created by the program, depicts its main flowchart, and describes a battery model optimized for this application.