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A new dynamometer system has been developed to improve the accuracy of tests that are run with a single cylinder version of a multi-cylinder engine. The dynamometer control system calculates the inertial torque and combustion torque that would normally be generated in a multi-cylinder engine. The system then applies the torque from the missing cylinders of the engine with the dynamometer. A unique high bandwidth hydraulic system is utilized to accurately apply these torque pulses. This allows the single-cylinder engine to have the identical instantaneous speed trajectory as the multi-cylinder engine, to test the single-cylinder engine at all engine speeds including very low speed operation, and to now do transient speed and load testing. Not only will this dramatically extend the capabilities of current single-cylinder engine test systems, but may open up new areas of research due to its transient testing capabilities.

A multidimensional simulation of Auxiliary Gas Injection (AGI) for late cycle oxygen enrichment was exercised to assess the merits of AGI for reducing the emissions of soot from heavy duty diesel engines while not adversely affecting the NOx emissions of the engine. Here, AGI is the controlled enhancement of mixing within the diesel engine combustion chamber by high speed jets of air or another gas. The engine simulated was a Caterpillar 3401 engine. For a particular operating condition of this engine, the simulated soot emissions of the engine were reduced by 80% while not significantly affecting the engine-out NOx emissions compared to the engine operating without AGI. The effects of AGI duration, timing, and orientation are studied to confirm the window of opportunity for realizing lower engine-out soot while not increasing engine out NOx through controlled enhancement of in-cylinder mixing.

In this paper, effect of intake air temperature, coolant temperature, and compression ratio on start of heat release (SOHR) in HCCI engines is investigated. The operational range with HCCI operation was determined experimentally using a CFR (Cooperative Fuels Research) engine with n-butane as the fuel. In-cylinder pressure was processed to evaluate SOHR. The effect of intake air and coolant temperature on SOHR increases as engine speed increases. In order to gain more insight into the combustion phenomena, SOHR was calculated using the theory of Livengood-Wu and compared with the experimental data. Dependence of SOHR on the equivalence ratio shows good correspondence between experiment and calculation. On the contrary, dependence on the intake air temperature and compression ratio shows poorer correspondence with predictions, especially under low engine speed. We interpret this as an indication of the importance of the active intermediate species that remain in the combustion chamber.

Simulations of DI Diesel engine combustion have been performed using a modified KIVA-II package with a recently developed phenomenological soot model. The phenomenological soot model includes generic description of fuel pyrolysis, soot particle inception, coagulation, and surface growth and oxidation. The computational results are compared with experimental data from a Cummins N14 single cylinder test engine. Results of the simulations show acceptable agreement with experimental data in terms of cylinder pressure, rate of heat release, and engine-out NOx and soot emissions for a range of fuel injection timings considered. The numerical results are also post-processed to obtain time-resolved soot radiation intensity and compared with the experimental data analyzed using two-color optical pyrometry. The temperature magnitude and KL trends show favorable agreement.

Multi-Dimensional modeling was carried out for a Mercury Marine two-stroke DISI engine. Recently developed spray, ignition, and combustion models were applied to medium load cases with an air-fuel ratio of 30:1. Three injection timings, 271, 291 and 306 ATDC were selected to investigate the effects of the injection timing on mixture formation, ignition and combustion. The results indicate that at this particular load condition, earlier injection timing allows more fuel to evaporate. However, because the fuel penetrates further toward the piston, a leaner mixture is created near the spark plug; thus, a slower ignition process with a weaker ignition kernel was found for the SOI 271 ATDC case. The measured and computed combustion results such as average in-cylinder pressure and NOx are in good agreements. The later injection case produces lower NOx emission and higher CO emission; this is due to poor mixing and is in agreement with experimental measurements.

The introduction of high-pressure injection systems in D.I. diesel engines has highlighted already known drawbacks of in-cylinder turbulence modeling. In particular, the well known equilibrium hypothesis is far from being valid even during the compression stroke and moreover during the spray injection and combustion processes when turbulence energy transfer between scales occurs under non-equilibrium conditions. The present paper focuses on modeling in-cylinder engine turbulent flows. Turbulence is accounted for by using the RNG k-ε model which is based on equilibrium turbulence assumptions. By using a modified version of the Kiva-3 code, different mathematically based corrections to the computed macro length scale are proposed in order to account for non-equilibrium effects. These new approaches are applied to a simulation of a recent generation HSDI Diesel engine at both full load and partial load conditions representative of the emission EUDC cycle.

A new ignition and combustion model has been developed and tested for use in premixed spark-ignition engines. The ignition model is referred to as the Discrete Particle Ignition Kernel (DPIK) model, and it uses Lagrangian markers to track the flame-front growth. The model includes the effects of electrode heat transfer on the early flame kernel growth process, and it is used in conjunction with a characteristic-time-scale combustion model once the ignition kernel has grown to a size where the effects of turbulence on the flame must be considered. A new term which accounts for the effect of air-fuel ratio, was added to the combustion model for modeling combustion in very lean and very rich mixtures. The flame kernel size predicted by the DPIK model was compared with measurements of Maly and Vogel. Furthermore, predictions of the electrode heat transfer were compared with data of Kravchik and Heywood. In both comparisons the model predictions were in good agreement with the experiments.

Fuel preparation and stratified combustion were studied for a conceptual gasoline Direct-Injection Spark-Ignition (GDI or DISI) engine by computer simulations. The primary interest was on the effects of different injector orientations and the effects of tumble ratio for late injection cases at a partial load operating condition. A modified KIVA-3V code that includes improved spray breakup and wall impingement and combustion models was used. A new ignition kernel model, called DPIK, was developed to describe the early flame growth process. The model uses Lagrangian marker particles to describe the flame positions. The computational results reveal that spray wall impingement is important and the fuel distribution is controlled by the spray momentum and the combustion chamber shape. The injector orientation significantly influences the fuel stratification pattern, which results in different combustion characteristics.

To help account for fuel distribution during combustion in diesel engines, a fuel film model has been developed and implemented into the KIVA-II code [1]. Spray-wall interaction and spray-film interaction are also incorporated into the model. Modified wall functions for evaporating, wavy films are developed and tested. The model simulates thin fuel film flow on solid surfaces of arbitrary configuration. This is achieved by solving the continuity, momentum and energy equations for the two dimensional film that flows over a three dimensional surface. The major physical effects considered in the model include mass and momentum contributions to the film due to spray drop impingement, splashing effects, various shear forces, piston acceleration, dynamic pressure effects, and convective heat and mass transfer.

Three different carburetor types have been tested to observe differences in the characteristics of the fuel/air mixtures produced. To characterize the fuel/air mixtures, two diagnostics have been applied: 1) High speed movies and subsequent analysis of the exit flow, and 2) measurement of the A/F ratio found in different positions within the intake manifold. The three different carburetor types that have been studied include a fixed-venturi, fixed-jet butterfly carburetor, a slide-valve carburetor, and a constant-velocity carburetor. Each carburetor type produced a unique set of exit flow characteristics, with differences in the optical density of fuel exiting the carburetor, and differences in the apparent amount of fuel on the intake manifold wall, entrained in the air flow, and in vapor phase.

An emissions and performance study was conducted to explore the effects of exhaust gas recirculation (EGR) and multiple injections on the emission of oxides of nitrogen (NOx), particulate emissions, and brake specific fuel consumption (BSFC) over a wide range of engine operating conditions. The tests were conducted on an instrumented single cylinder version of the Caterpillar 3400 series heavy duty Diesel engine. Data was taken at 1600 rev/min, and 75% load, and also at operating conditions taken from a 6-mode simulation of the federal transient test procedure (FTP). The fuel system used was an electronically controlled, common rail injector and supporting hardware. The fuel system was capable of as many as four independent injections per combustion event at pressures from 20 to 120MPa.

An endoscope-based image acquisition-and-processing camera system was used for diagnostics of pilot injection combustion in a single-cylinder heavy duty diesel engine. A study of the pilot injection or light load is of interest because the spray breakup, mixing and vaporization processes are less influenced by heat feedback from the flame than in full injection cases. This allows the spray process to be decoupled from the combustion process. The experimental cases were modeled using a version of the KIVA-II code that includes improvements in the turbulence, wall heat transfer, spray, ignition and combustion models. Pilot injections of three different amounts (10, 15 and 20% of the fuel injected at 75% load and 1600 RPM) at different start-of-injection timings were studied. The imaging system included an endoscope, an intensified CID camera, a frame grabber and the control circuitry.

Positive displacement flowmeters can be used to simply and accurately calibrate common flow transducers such as axial turbine and target flowmeters. Two means of utilizing positive displacement devices were studied for use as a laboratory flowmeter calibration. The first method employed a fixed displacement axial piston motor. This proved unsatisfactory due to the difficulty in quantifying flow losses. The second method used a large hydraulic cylinder. An optical encoder measured the position of the cylinder rod, permitting a direct calculation of the flow through the in-line flowmeter being calibrated. Because cylinder leakage is virtually zero at low pressure, flow can be readily calculated knowing the effective cylinder diameter and piston velocity. The method described in this paper permits flow rates to be measured with an accuracy of ±0.1% of the volumetric flow rate. This paper discusses details of the design of the flowmeter and calibration method.

Particle Image Velocimetry (PIV) was used to make gas velocity and turbulence measurements in a motored diesel engine. The experiments were conducted using a single-cylinder version of the Caterpillar 3406 production engine. One of the exhaust valves and the fuel injector port were used to provide optical access to the combustion chamber so that modifications to the engine geometry were minimal, and the results are representative of the actual engine. Measurements of gas velocity were made in a plane in the piston bowl using TiO2 seed particles. The light sheet necessary for PIV was formed by passing the beam from a Nd:YAG laser through the injector port and reflecting the beam off a conical mirror at the center of the piston. PIV data was difficult to obtain due to significant out-of-plane velocities. However, data was acquired at 25° and 15° before top dead center of compression at 750 rev/min.