Automotive Spark Ignition Engine Research Articles

STATISTICAL ENGINE KNOCK DETECTION

A knock detection circuit which is based on the signal of the accelerometer installed on the engine block of spark ignition automotive engine has a band-pass filter with a certain frequency as a parameter to be calibrated. New statistical method for determination of the frequency which is the most suitable for the knock detection in real-time applications is proposed. The knock detectability is associated with a statistical hypothesis for testing the equality of two mean values, i.e., mean values of the amplitudes for knocking and non-knocking cycles, and signal-to-noise ratio is associated with the value of the statistic. The frequency with the largest signal-to-noise ratio is chosen for implementation in the engine knock detection circuit.

SIMPLIFIED MODELS OF ENGINE HC EMISSIONS, EXHAUST TEMPERATURE AND CATALYST TEMPERATURE FOR AUTOMOTIVE COLDSTART

The initial 1-2 minutes of operation of an automotive spark-ignition engine, commonly called as the “coldstart” period, produces more than 75-80 % of the hydrocarbon (HC) emissions in a typical drive cycle. Model-based controller development requires accurate, yet simple, models that can run in realtime. Simple, intuitive models are developed to predict both tailpipe hydrocarbon (HC) emissions and exhaust temperature during coldstart. Each of the models is chosen to be sum of first order linear systems based on the observation of experimental data and on the notion that such structure is suitable for controller synthesis. Inputs to these models are AFR, spark timing and engine crankshaft speed. A reduced order thermodynamic model for the catalyst temperature is also developed. The parameters are identified using least squares technique. The model estimates for the coldstart are compared with the experimental results with good agreement. Submitted to Fifth IFAC Symposium on Advances in Automotive Control

Some aspects concerning the geometry of a hinged engine with a variable compression ratio

An improvement in automotive fuel consumption has been for many years the most important challenge in engine development. In a century of automotive spark ignition engine development, only two parameters were subject to automatic control: the air-fuel ratio and spark advance. Ever since, a wide range of technologies has been developed in order to improve fuel economy further. The following strategy was used: the identification of the sources of losses in the conventional spark ignition engine and then the attempt to reduce them one by one. The potential of these technologies needs to be evaluated by a cost and consumption benefit trade-off and all these, of course, without affecting the power level. In this context, the authors are about to develop a variable geometrical compression ratio engine, in order to overcome the main drawback of the spark ignition engine: the continuous variation of the real rate of compression, caused by the load control. The concept of the variable geometrical compression ratio (VCR) engine is the subject of a patent and consists of a hinged mechanism. It is an intrinsic, automatic self-regulation system with a fast response time and at the same time is a natural development of the classic engine. So far, two prototypes have been designed and tested. The paper presents some specific features regarding hinge position choice. The following are taken into consideration: the upper block rotational angle, added angle of the piston, tipping torque, and relative motion of the camshaft with respect to the crankshaft.

The cam profile switching state detection method

A new method for the detection of the CPS (cam profile switching) state of spark ignition automotive engines is proposed and implemented. The method is based on the evaluation of the amplitude and the phase of the component of the intake manifold pressure signal with the period of 720 CA (crank angle) degrees. The method permits the detection of the CPS bank failure even at high rotational speeds.

Methods for Specific Emission Evaluation in Spark Ignition Engines Based on Calculation Procedures of Air-Fuel Ratio: Development, Assessment, and Critical Comparison

New computational procedures are proposed for evaluating the exhaust brake specific mass emissions of each pollutant species in internal combustion (IC) engines. The procedures start from the chemical reaction of fuel with combustion air and, based on the measured exhaust raw emissions THC, CH4,NOx, CO, O2,CO2, calculate the volume fractions of the compounds in the exhaust gases, including those that are not usually measured, such as water, nitrogen and hydrogen. The molecular mass of the exhaust gases is then evaluated and the brake specific emissions can be obtained if the exhaust flow rate and the engine power output are measured. The algorithm can also be applied to the evaluation of air-fuel ratio from measured raw volume emissions of IC engines. The new procedures take the effects of various fuel and combustion air compositions into account, with particular reference to different natural gas blends as well as to the presence of water vapor, CO2, Ar and He in the combustion air. In the paper, the algorithms are applied to the evaluation of air-fuel ratio and brake specific mass emissions in an automotive bi-fuel Spark Ignition (SI) engine with multipoint sequential port-fuel injection. The experimental tests were carried out in a wide range of steady-state operating conditions under both gasoline and compressed natural gas operations. The specific emissions calculated from the new procedures are compared to those evaluated by applying Society of Automotive Engineers (SAE) and International Standards Organization (ISO) recommended practices and the air-fuel ratio results are compared to those obtained either from directly measured air and fuel mass flow rates or from Universal Exhaust Gas Oxygen (UEGO) sensor data. The sensitivity of the procedure results to the main engine working parameters, the influence of environmental conditions (in particular the effect of air humidity on NOx formation) and the experimental uncertainties are also determined.

Composite adaptive and input observer‐based approaches to the cylinder flow estimation in spark ignition automotive engines

AbstractThe performance of air charge estimation algorithms in spark ignition automotive engines can be enhanced using advanced estimation techniques available in the controls literature. This paper illustrates two approaches of this kind that can improve the cylinder flow estimation for gasoline engines without external exhaust gas recirculation (EGR). The first approach is based on an input observer, while the second approach relies on an adaptive estimator. Assuming that the cylinder flow is nominally estimated via a speed‐density calculation, and that the uncertainty is additive to the volumetric efficiency, the straightforward application of an input observer provides an easy to implement algorithm that corrects the nominal air flow estimate. The experimental results that we report in the paper point to a sufficiently good transient behaviour of the estimator. The signal quality may deteriorate, however, for extremely fast transients. This motivates the development of an adaptive estimator that relies mostly on the feedforward speed‐density calculation during transients, while during engine operation close to steady‐state conditions, it relies mostly on the adaptation. In our derivation of the adaptive estimator, the uncertainty is modelled as an unknown parameter multiplying the intake manifold temperature. We use the tracking error between the measured and modelled intake manifold pressure together with an appropriately defined prediction error estimate to develop an adaptation algorithm with improved identifiability and convergence rate. A robustness enhancement, via a σ‐modification with the σ‐factor depending on the prediction error estimate, ensures that in transients the parameter estimate converges to a pre‐determined a priori value. In close to steady‐state conditions, the σ‐modification is rendered inactive and the evolution of the parameter estimate is determined by both tracking error and prediction error estimate. Further enhancements are made by incorporating a functional dependence of the a priori value on the engine operating conditions such as the intake manifold pressure. The coefficients of this function can be learned during engine operation from the values to which the parameter estimate converges in close to steady‐state conditions. This feedforward learning functionality improves transient estimation accuracy and reduces the convergence time of the parameter estimate. Copyright © 2004 John Wiley & Sons, Ltd.

Illustration of the Use of an Instructional Version of a Thermodynamic Cycle Simulation for a Commercial Automotive Spark-Ignition Engine

The development and use of an instructional version of a thermodynamic engine cycle simulation for classroom use is described. This simulation is based on well-established features, but which are not necessarily the most advanced. The major simplification of this instructional simulation is the use of constant specific heat capacities as opposed to the use of variable composition and properties. The cycle simulation was developed with an elementary set of conventional sub-model components. To account for the unsteady flow dynamics, an empirical adjustment factor was used. With the exception of this empirical adjustment factor, all of the constants associated with the sub-models are used as suggested by the original publications. Students, therefore, are readily able to develop and use this simulation. This paper then demonstrates the usefulness of such a basic simulation in describing the overall performance of a commercial automotive spark-ignition engine for a range of engine speeds and operating conditions. A modern, four-valve per cylinder, two-camshaft engine was selected for this study. Although the cycle simulation was based on elementary conventional features, a number of important engine characteristics were correctly obtained. These included the overall performance for engine speeds up to 7000 rpm, and details such as the time (crank angle) of peak pressure for optimum performance.

Linear Robust Control of Identified State-Space Non-Linear Inverse Compensated SI Engine

This paper presents a non-linear inverse compensation methodology based on a technique similar to Horowitz's non-linear quantitative feedback theory. A causal inverse is found based on an identified non-linear plant model. Linear identification of the non-linear identified inverse compensated system is carried out in order to achieve a reduction in the unstructured uncertainty representation. Subsequent robust control design results in an improvement in robust stability and robust performance over the uncompensated system. Using a parameter space linear robust control design technique, the method is applied to the automotive Spark ignition (SI) engine idle speed control problem and is experimentally validated using an electric dynamometer.

A Hierarchical System of Models for the Optimal Design of Control Strategies in Spark Ignition Automotive Engines

The structure of a hierarchical system of models for model based optimization and rapid prototyping of control strategies in automotive spark ignition engines is presented. A distributed and hybrid modeling approach has been considered in order to reach an acceptable level of precision with conventional computational resources and limited experimental effort. Different class of models have been used, ranging from black-box (regression and/or neural networks) to physical ones (thermo-chemical); mean value dynamical model are also considered for the simulation of transient engine-vehicle manoeuvres. The advantages of the mixed approach are reviewed and the critical role played by the identification phase is discussed through a comparative analysis of the estimation procedures adopted during model development and validation process.

Parameter Identification, Estimation, and Dynamometer Valida tion of the Nonlinear Dynamics of an Automotive Spark-Ignition Engine

The identification is described of a nonlinear mathematical model of a modem four-cylinder four- stroke spark-ignition automotive engine for idle-speed control applications. The primary outputs are engine speed and inlet-manifold pressure, and the primary inputs are mass air/fuel ratio, spark timing, air bleed valve duty cycle, and disturbance torque. The model can be used for simulating and predicting the dynamic response of the engine system for control algorithm development as a tool to evaluate various engine control concepts. The nonlinear mathematical engine model is obtained using an assumed nonlinear model structure, and a sequential least squares identification algorithm is used to estimate the model parameters. The model formulation, which is based on nonlinear continuous differential equations, consists of four state variables with 15 parameters to represent the engine dynamics. The model contains representations of the idle air bypass valve, manifold plenum, engine-pumping phenomena, brake output torque, and rotational dynamics. The model structure and identified parameter set are validated using experimental data from an engine in an electric dynamometer. The results indicate the suitability of the model structure and nonlinear identification technique for general engine idle-speed control model applications in both off-line and on-line implementations.

Development and Validation of Hierarchical Models for the Design of Engine Control Strategies

The development of mathematical models for the design of controlstrategies for spark ignition automotive engines is described. The objectiveof the models, used for both simulation and optimization analysis, is theprediction of the effects of control strategies on fuel consumption andemissions of a vehicle over arbitrary driving cycles. In order to achievethe best compromise between precision, experimental costs, computationaltime and flexibility, a mixed modelling approach is used, withphenomenological and input-output models integrated within a hierarchicalsystem.

Modeling and Validation of Automotive Engines for Control Algorithm Development

There is considerable interest in coordinated automotive engine/transmission control to smooth shifts, and for traction control of front wheel vehicles. This paper outlines a nonlinear dynamic engine model of a port fuel-injected engine, which can be used for control algorithm development. This engine model predicts the mean engine brake torque as a function of the engine controls (i.e., throttle angle, spark advance, fuel flow rate, and exhaust gas recirculation (E. G. R.) flow rate). The model has been experimentally validated for a specific engine, and includes: • intake manifold dynamics, • fuel delivery dynamics, and • process delays inherent in the four-stroke engine. This model is used in real time within a control algorithm, and for system simulation. Also, it is flexible enough to represent a family of spark ignition automotive engines, given some test and/or simulation data for setting parameters.

Mixture Strength Measurements in the Combustion Chamber of SI Engine via Rayleigh Scattering : 3rd Report, Results in the Motored Engine

An experimental study was conducted to determine the time history of fuel vapor concentration in the combustion chamber of an automotive spark ignition engine. Laser Rayleigh scattering was applied for the remote, nonintrusive, point probing of the concentration of fuel vapor in the combustion chamber, which was caused by the timed injection of liquid fuel into an intake port. In order to make the optical diagnostics accessible, the original engine was modified to permit installation of an extended combustion cylinder with three sets of glass windows and an extended piston

Mixture Strength Measurements in the Combustion Chamber of SI Engine via Rayleigh Scattering : 2nd Report, Results for Liquid Fuel Injection

An experimental study was made of the fundamental aspect of the mixture formation in the combustion chamber of an automotive spark ignition engine with multipoint fuel injection. The mixture formation process during the intake stroke of an engine was simulated by the intermittent injection of gasoline or Freon-113 into the steady flow of dust-free dry air through an intake port. The time histories of the vapor concentration at several locations in the transparent combustion cylinder were determined with the application of the laser Rayleigh scattering. The measured results were expressed in terms of the peak vapor concentration at the location of interest, the period of time between the initiation of the liquid fuel injection and vapor arrival, and the duration for the vapor to be observed over a wide range of injection pressures, injection durations, intake valve temperatures, intake valve lifts and intake air flow rates

Self-tuning optimization of spark ignition automotive engines

The use of self-tuning control concepts applied to the adaptive optimization of spark ignition angles of an automotive engine is described. In particular, it is shown how the concepts of self-adaptive control theory can be modified to allow their use in a continuous updating of the spark-angle map as a function of load and speed. Used in this manner, the self-tuner can account for in-service changes in engine characteristics, changes due to variations of ambient and operational conditions. In addition, self-adaptation allows the spark-controller algorithm to tune itself, so that the factory-generated spark map is precisely matched to the exact nature of each individual engine. The basic theory of self-tuning optimizers (also known as extremum controllers) is outlined, and their performance features are discussed with particular reference to their implementation in adaptive spark-timing systems. It is shown that the self-tuning extremum controller can be made robust even when the signal-to-noise ratio is less than one.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Mixture strength measurements in the combustion chamber of SI engine via Rayleigh scattering. 3rd Report. Results in the motored engine.

An experimental study was made to determine the time history of fuel vapor concentration in the combustion chamber of an automotive spark ignition engine. The laser Rayleigh scattering was applied for the remote, nonintrusive, point-probing of the concentration of fuel vapor in the combustion chamber, which was caused by the timed injection of liquid fuel into an intake port. In order to make the optical diagnostics accessible, the original engine was modified to permit installation of an extended combustion cylinder with three sets of glass windows and an extended piston. The results showed that the vapor concentration increased and reached a peak after which it decreased during the intake stroke, and was almost constant during the compression stroke. It was also found that the vapor concentration increased with a reduced air fuel ratio supplied, and with increased engine speed and fuel injection pressure. A maximum occurred as a function of fuel injection timing.

The behavior of liquid fuel droplets in the combustion chamber of a spark ignition engine. (2nd Report, Droplet size measurements during motoring).

An experimental study was made of droplet behavior in the combustion chamber of an automotive spark ignition engine with multipoint fuel injection. The laser Mie scattering technique was applied for time-resolved measurements of the size of the liquid droplets in the combustion chamber which were caused by the intermittent injection of unleaded regular gasoline into an intake port during the intake stroke of the motored engine. In order to make the optical diagnostics accessible, the original engine was modified to permit installation of an extended transparent combustion cylinder and a piston. The results showed that the temporal variation of the droplet size during intake and compression strokes was slight. It was also found that the droplet size decreased with an increase in the intake valve temperature. Both engine speed and fuel injection timing did not have an appreciable effect on the drolet size within the range of experimental conditions.

The behavior of liquid fuel droplets in the combustion chamber of a spark ignition engine. Droplet size measurements under stationary flow test conditions.

An experimental study was made of the fuel droplet behavior in the combustion chamber of an automotive spark ignition engine. The mixture formation during the intake stroke was simulated by the intermittent injection of gasoline into a steady flow of air through an intake port. The spatial distribution of the size and number of droplets was measured by applying the laser Mie scattering technique. The results showed that both the intake air flow rate and the intake valve lift did not give and appreciable influence of the Sauter mean diameter of the fuel droplets. The fuel supply from two different types of injectors almost caused the same size of droplets. It was also found that the location for fuel injection was one of the important factors affecting the droplet size. The total quantity of fuel droplets increased with and increased with an increase of the intake valve lift.

Behavior of droplets in pulsating air flow through an intake manifold.

A numerical calculation supplemented by experimental work was conducted of the behavior of fuel droplets subjected to pulsating air flow in the T-branched duct of a square cross section for a better understanding of fuel supply characteristics in an intake manifold of an automotive spark ignition engine. The Lagrangian approach was adopted to derive simultaneous equations of momentum, heat and mass transfer for computing the locations, temperatures and diameters of moving droplets as a function of spatial coordinates The results were expressed primarily in terms of the location at the impact deposition of droplets relevant to the formation of liquid film on the bottom wall of the duct. It was revealed that the calculated results agreed well with the empirical data. It was also suggested that the undesirable aspects of liquid film might possibly by relieved if small droplets with high volatility and low density are infused at optimum timing into a warm air flow with a short period of pulsation.

An Automotive Piston Lubrication Model

An analytical study of the dynamics of a piston in a reciprocating engine was conducted. The analysis, which incorporates a hydrodynamic lubrication model, was applied to a V-8 automotive spark ignition engine. The variation of piston transverse position and rotation with crank angle, and the piston-skirt frictional power loss were calculated for different wrist pin locations, piston-to-cylinder clearances, and lubricant viscosities. The results obtained indicate that piston motion is strongly affected by the location of the wrist pin and that piston-skirt friction is increased significantly if the wrist pin is at an unfavorable position. In addition, piston dynamics were found to be sensitive to piston-cylinder bore clearance and lubricant viscosity, underscoring their importance in engine design. Presented at the 37th Annual Meeting in Cincinnati, Ohio, May 10–13, 1982