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A detailed description of a numerical method for computing unsteady flows in engine intake and exhaust systems is given. The calculations include the effects of heat transfer and friction. The inclusion of such calculations in a mathematically simulated engine cycle is discussed and results shown for several systems. In particular, the effects of bell-mouth versus plain pipe terminations and the effects of a finite surge tank are calculated. Experimental data on the effect of heat transfer from the back of the intake valve on wave damping are given and show the effect to be negligible. Experimental data on wave damping during the valve closed period and on the temperature rise of the air near the valve are also given.

This paper describes a method for studying reactions of hydrocarbons in S.I. engine exhaust gases. The reaction of ethane is described using an Arrhenius model (experimentally E = 86,500 cal/mole) for the rate of ethane diappearance and empirical correlations for distributions of the products carbon monoxide, ethylene, formaldehyde, methane, acetylene, and propane as a function of the fraction of ethane reacted. The results show that the nature of partial oxidation products from a nonreactive hydrocarbon may be less desirable from an air pollution viewpoint than the initial hydrocarbon.

The ratio of two temperature gradients across the combustion-chamber wall in a diesel engine is used to provide a heat flow ratio showing the radiant heat transfer as a per cent of local total heat transfer. The temperature gradients were obtained with a thermocouple junction on each side of the combustion-chamber wall. The first temperature gradient was obtained by covering the thermocouple at the cylinder gas-wall interface with a thin sapphire window, while the second was obtained without the window. Results show that the time-average radiant heat transfer is of significant magnitude in a diesel engine, and is probably even more significant in heat transfer during combustion and expansion.

The objective of this research was to investigate the effect of injection pressure on air entrainment into transient diesel sprays. The main application of interest was the direct injection diesel engine. Particle Image Velocimetry was used to make measurements of the air entrainment velocities into a spray plume as a function of time and space. A hydraulically actuated, electronically controlled unit injector (HEUI) system was used to supply the fuel into a pressurized spray chamber. The gas chamber density was maintained at 27 kg/m3. The injection pressures that were studied in this current research project were 117.6 MPa and 132.3 MPa. For different injection pressures, during the initial two-thirds of the spray plume there was little difference in the velocities normal to the spray surface. For the last third of the spray plume, the normal velocities were 125% higher for the high injection pressure case.

The objective of this paper is to present the results of the GT Power calibration with engine test results of the air loop system technology down selection described in the SAE Paper No. 2012-01-0831. Two specific boosting systems were identified as the preferred path forward: (1) Super-turbo with two speed Roots type supercharger, (2) Super-turbo with centrifugal mechanical compressor and CVT transmission both downstream a Fixed Geometry Turbine. The initial performance validation of the boosting hardware in the gas stand and the calibration of the GT Power model developed is described. The calibration leverages data coming from the tests on a 2 cylinder 2-stroke 0.73L diesel engine. The initial flow bench results suggested the need for a revision of the turbo matching due to the big gap in performance between predicted maps and real data. This activity was performed using Honeywell turbocharger solutions spacing from fixed geometry waste gate to variable nozzle turbo (VNT).

The purpose of the tests conducted on a single-cylinder laboratory engine was to determine the mechanism of combustion that affect exhaust emissions and the relationship of those mechanisms to engine design and operating variables. For the engine used in this study, the exhaust emissions were found to have the following dependence on various engine variables. Hydrocarbon emission was reduced by lean operation, increased manifold pressure, retarded spark, increased exhaust temperature, increased coolant temperature, increased exhaust back pressure, and decreased compression ratio. Carbon monoxide emission was affected by air-fuel ratio and premixing the charge. Oxides of nitrogen (NO + NO2 is called NOx) emission is primarily a function of the O2 available and the peak temperature attained during the cycle. Decreased manifold pressure and retarded spark decrease NOx emission. Hydrocarbons were found to react to some extent in the exhaust port and exhaust system.

A detailed mathematical model of the thermodynamic events of a crankcase scavenged, two-stroke, SI engine is described. The engine is divided into three thermodynamic systems: the cylinder gases, the crankcase gases, and the inlet system gases. Energy balances, mass continuity equations, the ideal gas law, and thermodynamic property relationships are combined to give a set of coupled ordinary differential equations which describe the thermodynamic states encountered by the systems of the engine during one cycle of operation. A computer program is used to integrate the equations, starting with estimated initial thermodynamic conditions and estimated metal surface temperatures. The program iterates the cycle, adjusting the initial estimates, until the final conditions agree with the beginning conditions, that is, until a cycle results.

Highly time resolved measurements of cylinder pressure acquired simultaneously from three transducers were used to investigate the nature of knocking combustion and to identify biases that the pressure measurements induce. It was shown by investigating the magnitude squared coherence (MSC) between the transducer signals that frequency content above approximately 40 kHz does not originate from a common source, i.e., it originates from noise sources. The major source of noise at higher frequency is the natural frequency of the transducer that is excited by the impulsive knock event; even if the natural frequency is above the sampling frequency it can affect the measurements by aliasing. The MSC analysis suggests that 40 kHz is the appropriate cutoff frequency for low-pass filtering the pressure signal. Knowing this, one can isolate the knock event from noise more accurately.

The paper describes a way to a 1-D central streamline model of a radial turbine flow, suitable for twin-scroll description and based on approximation of real physics of flow mixing and energy transformation. The original 1-D model of a single scroll turbine, described earlier in numerous SAE papers, has been amended by twin-scroll nozzles (both vaneless or with blade cascades) and mixing of individual partitions of flows upstream of additional vaneless nozzle and an impeller. This model is transferable to 1-D unsteady simulations as it is (i.e., using quasi-steady approach) or using 1-D unsteady solvers. It has suitable features even for more detailed description of turbine flows and energy transformation. The first results of pulse influence on turbine maps delivered expected results consisting of complicated interaction between individual losses.

A computational, three-dimensional approach to investigate the behavior of diesel soot particles in the micro-channels of wall-flow Diesel Particulate Filters is presented. The KIVA3V CFD code, already extended to solve the 2D conservation equations for porous media materials [1], has been enhanced to solve in 2-D and 3-D the governing equations for reacting and compressible flows through porous media in non axes-symmetric geometries. With respect to previous work [1], a different mathematical approach has been followed in the implementation of the numerical solver for porous media, in order to achieve a faster convergency as source terms were added to the governing equations. The Darcy pressure drop has been included in the Navier-Stokes equations and the energy equation has been extended to account for the thermal exchange between the gas flow and the porous wall.

This paper deals with the influence of CO, CO₂, N₂, H₂, C₂H₆, C₃H₈ and C₄H₁₀ content in fuel on basic engine integral parameters. The focus is on the influence of biogas fuel composition on engine thermodynamic features. The paper describes the iterative regression method evaluating the influence of individual gas mass fraction and engine operation parameters on cumulative heat release curve of SI engines. The parameters for recalculation of heat release patterns depending on individual gas mass fraction in fuel and operation parameters are derived. The modeled cumulative heat release patterns are converted into burned fuel fraction pattern. The particular outputs are generalized using GT-POWER-based model results.

3-D Computational Fluid Dynamics (CFD) simulations have been performed to study particulate formation in a Spark-Ignition (SI) engine under premixed conditions. A semi-detailed soot model and a chemical kinetic model, including poly-aromatic hydrocarbon (PAH) formation, were coupled with a spark ignition model and the G equation flame propagation model for SI engine simulations and for predictions of soot mass and particulate number density. The simulation results for in-cylinder pressure and particle size distribution (PSDs) are compared to available experimental studies of equivalence ratio effects during premixed operation. Good predictions are observed with regard to cylinder pressure, combustion phasing and engine load. Qualitative agreements of in-cylinder particle distributions were also obtained and the results are helpful to understand particulate formation processes.

Knock in a Rotax-914 engine was modeled and investigated using an improved version of the KIVA-3V code with a G-equation combustion model, together with a reduced chemical kinetics model. The ERC-PRF mechanism with 47 species and 132 reactions [1] was adopted to model the end gas auto-ignition in front of the flame front. The model was validated by a Caterpillar SI engine and a Rotax-914 engine in different operating conditions. The simulation results agree well with available experimental results. A new engineering quantified knock criterion based on chemical mechanism was then proposed. Hydroperoxyl radical (HO2) shows obvious accumulation before auto-ignition and a sudden decrease after auto-ignition. These properties are considered to be a good capability for HO2 to investigate engine knock problems.

The paper focuses on portable “on-board” instrumentation and methods for evaluation of exhaust emissions from scooters and various small machinery under real-world driving conditions. Two approaches are investigated here. In one, a miniature on-board system mounted on the equipment itself performs online measurements of the concentrations of the pollutants of interest (HC, CO, CO2, NOx, some property of particulate matter), and measurement or computation of the intake air flow. This approach has been used on a 50 cm3 scooter fitted with a 14-kg on-board system and driven on local routes. Measured concentrations of gaseous compounds, particle mass and total particle length were multiplied with the corresponding intake air flow computed from measured engine rpm, intake air manifold pressure and temperature. In the second approach, a full-flow dilution tunnel, gas analyzers and particle measurement or sampling devices are mounted on an accompanying hand cart or vehicle.

The performance of a structural design significantly depends upon the assumptions made on input load. In order to estimate the input load, during the design and development stage of the suspension assembly of a BAJA car, designers and analysts invest immense amount of time and effort to formulate the mathematical model of the design. These theoretical formulations may include idealization errors which can affect the performance of the car as a final product. Due to the errors associated with the assumption of design load, several components might have more weight or may have less strength than needed. This discrepancy between the assumed input load (lab or theoretical studies) and the actual load from the environment can be eliminated by performing a real life testing process using load recovery methodology. Commercial load cells exist in industry to give engineers insight to understanding the complex real world loading of their structures.

Sector mesh modeling is the dominant computational approach for combustion system design optimization. The aim of this work is to quantify the errors descending from the sector mesh approach through three geometric modeling approaches to an optical diesel engine. A full engine geometry mesh is created, including valves and intake and exhaust ports and runners, and a full-cycle flow simulation is performed until fired TDC. Next, an axisymmetric sector cylinder mesh is initialized with homogeneous bulk in-cylinder initial conditions initialized from the full-cycle simulation. Finally, a 360-degree azimuthal mesh of the cylinder is initialized with flow and thermodynamics fields at IVC mapped from the full engine geometry using a conservative interpolation approach. A study of the in-cylinder flow features until TDC showed that the geometric features on the cylinder head (valve tilt and protrusion into the combustion chamber, valve recesses) have a large impact on flow complexity.

Computer simulation technology coupled with indoor laboratory facilities is being used in the automotive industry to provide up-front assessment of vehicle performance. This paper presents a technique to evaluate passenger vehicle tire wear performance as related to suspension and tire design early in the design process. Motivation for developing this tool is to optimize suspension and tire design to tire wear early in the design process. This approach has resulted in reductions in vehicle development time, dependency on outdoor testing and the need for expensive prototype vehicles. A full vehicle ADAMS model of a production vehicle is used to animate vehicle suspension kinematic motions, and dynamic tire forces of vehicle maneuvers for a preselected outdoor tire wear route. Time histories of five vehicle parameters are generated: radial force, slip angle or lateral force, camber, velocity and driving and braking torques.

The present paper deals with the application of the LES approach to in-cylinder flow modeling. The main target is to study cycle-to-cycle variability (CCV) using 3D-CFD simulation. The engine model is based on a spark-ignited single-cylinder research engine. The results presented in this paper cover the motored regime aiming at analysis of the cycle-resolved local flow properties at the spark plug close to firing top dead center. The results presented in this paper suggest that the LES approach adopted in the present study is working well and that it predicts CCV and that the qualitative trends are in-line with established knowledge of internal combustion engine (ICE) in-cylinder flow. The results are evaluated from a statistical point of view based on calculations of many consecutive cycles (at least 10).

The combustion propagation mechanism of homogeneous charge compression ignition combustion was investigated using planar laser Rayleigh scattering thermometry, and was compared to that of spark-ignition combustion. Ethylene and dimethyl ether were chosen as the fuels for SI and HCCI experiments and have nearly constant Rayleigh scattering cross-sections through the combustion process. Beam steering at the entrance window limited the load range for HCCI conditions and confined the quantitative interpretation of the results to local regions over which an effective beam steering correction could be applied. The SI conditions showed a clear bimodal temperature behavior with a well-defined interface between reactants and products. The HCCI results showed large regions that were partially combusted, i.e., at a temperature above the reactants but below the adiabatic flame temperature. Dual-imaging experiments confirm that the burned region was progressing towards the fully burned state.

The higher cylinder peak pressure and pressure rise rate of modern diesel and gasoline fueled engines tend to increase combustion noise while customers demand lower noise. The multiple degrees of freedom in engine control and calibration mean there is more scope to influence combustion noise but this must first be measured before it can be balanced with other attributes. An efficient means to realize this is to calculate combustion noise from the in-cylinder pressure measurements that are routinely acquired as part of the engine development process. This publication reviews the techniques required to ensure accurate and precise combustion noise measurements. First, the dynamic range must be maximized by using an analogue to digital converter with sufficient number of bits and selecting an appropriate range in the test equipment.