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Technical Paper


A comprehensive cycle analysis has been developed for four-stroke spark-ignited engines from which the indicated performance of a single cylinder engine was computed with a reasonable degree of accuracy. The step-wise cycle calculations were made using a digital computer. This analysis took into account mixture composition, dissociation, combustion chamber shape (including spark plug location), flame propagation, heat transfer, piston motion, engine speed, spark advance, manifold pressure and temperature, and exhaust pressure. A correlation between the calculated and experimental performance is reported for one engine at a particular operating point. The calculated pressure-time diagram was in good agreement with the experimental one in many respects. The calculated peak pressure was 10 per cent lower and the thermal efficiency 0.8 per cent higher than the measured values. Thus this calculational procedure represents a significant improvement over constant volume cycle approximations.
Technical Paper

NVH Analysis of Balancer Chain Drives with the Compliant Sprocket of the Crankshaft with a Dual-Mass Flywheel for an Inline-4 Engine

The work presented in this paper outlines the design and development of a compliant sprocket for balancer drives in an effort to reduce the noise levels related to chain-sprocket meshing. An experimental observation of a severe chain noise around a resonant engine speed with the Dual-Mass Flywheel (DMF) and standard build solid (fixed) balancer drive sprocket. Torsional oscillation at the crankshaft nose at full load is induced by uneven running of crankshaft with a dual-mass flywheel system. This results in an increase of the undesirable impact noise caused by the meshing between the chain-links and the engagement/disengagement regions of sprockets, and the clatter noise from the interaction between the vibrating chain and the guides. This paper evaluates and discusses the benefits that the compliant sprocket design provided. A multi-body dynamics system (MBS) model of the balancer chain drive has been developed, validated, and used to investigate the chain noise.
Technical Paper

An Engineering Method for Part-load Engine Simulation

This work provides an effective engineering method of building a part-load engine simulation model from a wide-open throttle (WOT) engine model and available dynamometer data. It shows how to perform part-load engine simulation using optimizer for targeted manifold absolute air pressure (MAP) on a basic matrix of engine speed and MAP. Key combustion parameters were estimated to cover the entire part-load region based on affordable assumptions and limitations. Engine rubbing friction and pumping friction were combined to compare against the motoring torque. The emission data from GM dynamometer laboratory were used to compare against engine simulation results after attaching the RLT sensor to record emission data in the engine simulation model.
Technical Paper

Fatigue Strength Effect of Thread Forming Process in Cast Aluminum

Two thread forming processes, rolling and cutting, were studied for their effects on fatigue in cast aluminum 319-T7. Material was excised from cylinder blocks and tested in rotating-bending fatigue in the form of unnotched and notched specimens. The notched specimens were prepared by either rolling or cutting to replicate threads in production-intent parts. Cut threads exhibited conventional notch behavior for notch sensitive materials. In contrast, plastic deformation induced by rolling created residual compressive stresses in the notch root and significantly improved fatigue strength to the point that most of the rolled specimens broke outside the notch. Fractographic and metallographic investigation showed that cracks at the root of rolled notches were deflected upon initiation. This lengthened their incubation period, which effectively increased fatigue resistance.
Technical Paper

Cylinder Pressure Data Quality Checks and Procedures to Maximize Data Accuracy

Cylinder pressure data is so completely integral to the combustion system development process that ensuring measurements of the highest possible accuracy is of paramount importance. Three main areas of the pressure measurement and analysis process control the accuracy of measured cylinder pressure and its derived metrics: 1) Association of the pressure data to the engine's crankshaft position or cylinder volume 2) Pegging, or referencing, the pressure sensor output to a known, absolute pressure level 3) The raw, relative pressure output of the piezoelectric cylinder pressure sensor Certain cylinder pressure-based metrics, such as mean effective pressures (MEP) and heat release parameters, require knowledge of the cylinder volume associated with the sampled pressure data. Accurate determination of the cylinder volume is dependent on knowing the rotational position of the crankshaft.
Technical Paper

Design of a Rapid Prototyping Engine Management System for Development of Combustion Feedback Control Technology

Combustion feedback using cylinder pressure sensors, ion current sensors or alternative sensing techniques is actively under investigation by the automotive industry to meet future legislative emissions requirements. One of the drawbacks of many rapid prototyping engine management systems is their available analog interfaces, often limited to 10-12 bits with limited bandwidth, sampling rate and very simple anti-aliasing filters. Processing cylinder pressure or other combustion feedback sensors requires higher precision, wider bandwidths and more processing power than is typically available. For these reasons, Ricardo in collaboration with GM Research has developed a custom, high precision analog input subsystem for the rCube rapid prototyping control system that is specifically targeted at development of combustion feedback control systems.
Technical Paper

Critical Speed Vibrations Induced by Unstable Gyroscopic Moment

Critical speed induced by imbalance forces is a well-known dynamic behavior of rotating shafts. Such problems are typically found in flexible shafts or rigid shafts with flexible supports when the frequency of rotation reaches the natural frequencies of the shaft. This simple critical speed problem is well understood and formulated in many engineering texts. However, not all critical speed phenomena are induced by imbalance. A perfectly balanced shaft with certain inertial properties also reaches a critical speed condition at a rotational speed that is not equal to the natural frequency of the shaft. Several variables of the dynamic system play a role on the critical speed condition, which is mainly induced by the unstable gyroscopic moment acting on the shaft. The unstable gyroscopic moment forces the shaft bearings to deflect causing precession about the undeflected geometric centerline of the shaft, but the rotation and precession speeds remain synchronized at low speeds.
Technical Paper

Application of Hydraulic Body Mounts to Reduce the Freeway Hop Shake of Pickup Trucks

When pickup trucks are driven on concrete paved freeways, freeway hop shake is a major complaint. Freeway hop shake occurs when the vehicle passes over the concrete joints of the freeway which impose in-phase harmonic road inputs. These road inputs excite vehicle modes that degrade ride comfort. The worst shake level occurs when the vehicle speed is such that the road input excites the vehicle 1st bending mode and/or the rear wheel hop mode. The hop and bending mode are very close in frequency. This phenomenon is called freeway hop shake. Automotive manufacturers are searching for ways to mitigate freeway hop shake. There are several ways to reduce the shake amplitude. This paper documents a new approach using hydraulic body mounts to reduce the shake. A full vehicle analytical model was used to determine the root cause of the freeway hop shake.
Technical Paper

Bulkhead Loading Calculation of an Aluminum Engine Block Coupled with a Rotating Crankshaft through Elastohydrodynamic Bearings

During a new engine development program, or the adaptation of an existing engine to new platform architectures, testing is performed to determine the durability characteristics of the basic engine structure. Such testing helps to uncover High Cycle durability-related issues that can occur at the bulkhead walls as well as cap bolt thread areas in an aluminum cylinder block. When this class of issues occurs, an Elastohydrodynamic (EHD) bearing simulation capability is required. In this study, analytical methods and processes are established to calculate the localized distributed load on the bulkhead. The complexity in performing a system analysis is due to the nonlinear coupling between the bearing hydrodynamic pressure distribution and the crankshaft and block deformation. A system approach for studying the crankshaft-block interaction requires a crankshaft flexible body dynamics model, an engine block assembly flexible body dynamics model and a main bearing lubrication model.
Technical Paper

CFD-based Robust Optimization of Front-end Cooling Airflow

Development and integration of the cooling system for an automotive vehicle requires a balancing act between several performance and styling objectives. The cooling system needs to provide sufficient air for heat rejection with minimal impact on the aerodynamic drag, styling requirements and other criteria. An optimization of various design parameters is needed to develop a design to meet these objectives in a short amount of time. Increase in the accuracy of the numerical predictions and reduction in the turn-around time has made it possible for Computational Fluid Dynamics (CFD) to be used early in the design phase of the vehicle development. This study shows application of the CFD for robust design of the engine cooling system.
Technical Paper

Investigation of the Buoyancy Driven Flow in a Simplified Underhood - Part II, Numerical Study

This paper describes the numerical results for a simplified underhood buoyancy driven flow. The simplified underhood geometry consists of an enclosure, an engine block and two exhaust cylinders mounted along the sides of the engine block. The flow condition is set up in such a way that it mimics the buoyancy driven flow condition in the underhood environment when the vehicle is parked in a windbreak with the engine shut down. The experimental measurements for temperature and velocity of the same configuration were documented in the Part I of the same title. Present study focuses on the numerical issues of calculating temperature and flow field for the same flow configuration. The predicted temperature and velocity were compared with the available measured data. The mesh sizes, mesh type and the orders of spatial and temporal accuracy of the numerical setup are discussed.
Technical Paper

A Flexible Engine Control Architecture for Model-based Software Development

The fierce competition and shifting consumer demands require automotive companies to be more efficient in all aspects of vehicle development and specifically in the area of embedded engine control system development. In order to reduce development cost, shorten time-to-market, and meet more stringent emission regulations without sacrificing quality, the increasingly complex control algorithms must be transportable and reusable. Within an efficient development process it is necessary that the algorithms can be seamlessly moved throughout different development stages and that they can be easily reused for different applications. In this paper, we propose a flexible engine control architecture that greatly boosts development efficiency.
Technical Paper

A Three-Pillar Framework for Model-Based Engine Control System Development

This paper presents a comprehensive Matlab/Simulink-based framework that affords a rapid, systematic, and efficient engine control system development process including automated code generation. The proposed framework hinges on three essential pillars: 1 ) an accurate model for the target engine, 2) a toolset for systematic control design, and 3) a modular system architecture that enhances feature reusability and rapid algorithm deployment. The proposed framework promotes systematic model-based algorithm development and validation in virtual reality. Within this context, the framework affords integration and evaluation of the entire control system at an early development stage, seamless transitions across inherently incompatible product development stages, and rapid code generation for production target hardware.
Journal Article

Modeling and Simulation of Torsional Vibration of the Compliant Sprocket in Balance Chain Drive Systems

The work presented in this paper outlines the development of a simulation model to aid in the design and development of a compliant sprocket for balancer drives. A design with dual-mass flywheel and a crank-mounted compliant chain sprocket greatly reduces interior noise levels due to chain meshing. However, experimental observations showed the compliant sprocket can enter into resonance and generate excessive vibration energy during startup. Special features are incorporated into the compliant sprocket design to absorb and dissipate this energy. Additional damper spring rate, high hysteresis and large motion angle that overlap the driving range may solve the problem during engine start-up period. This work develops a simulation model to help interpret the measured data and rank the effectiveness of the design alternatives. A Multibody dynamics system (MBS) model of the balancer chain drive has been developed, validated, and used to investigate the chain noise.
Journal Article

Development of the Combustion System for General Motors' 3.6L DOHC 4V V6 Engine with Direct Injection

General Motors' 3.6L DOHC 4V V6 engine has been upgraded to provide substantial improvements in performance, fuel economy, and emissions for the 2008 model year Cadillac CTS and STS. The fundamental change was a switch from traditional manifold-port fuel injection (MPFI) to spark ignition direct injection (SIDI). Additional modifications include enhanced cylinder head and intake manifold air flow capacities, optimized camshaft profiles, and increased compression ratio. The SIDI fuel system presented the greatest opportunities for system development and optimization in order to maximize improvements in performance, fuel economy, and emissions. In particular, the injector flow rate, orifice geometry, and spray pattern were selected to provide the optimum balance of high power and torque, low fuel consumption, stable combustion, low smoke emissions, and robust tolerance to injector plugging.
Technical Paper

Application of Model-Based Design Techniques for the Control Development and Optimization of a Hybrid-Electric Vehicle

Model-based design is a collection of practices in which a system model is at the center of the development process, from requirements definition and system design to implementation and testing. This approach provides a number of benefits such as reducing development time and cost, improving product quality, and generating a more reliable final product through the use of computer models for system verification and testing. Model-based design is particularly useful in automotive control applications where ease of calibration and reliability are critical parameters. A novel application of the model-based design approach is demonstrated by The Ohio State University (OSU) student team as part of the Challenge X advanced vehicle development competition. In 2008, the team participated in the final year of the competition with a highly refined hybrid-electric vehicle (HEV) that uses a through-the-road parallel architecture.
Technical Paper

Observer Design for Fuel Reforming in HCCI Engines Using a UEGO Sensor

Homogeneous Charge Compression Ignition (HCCI) combustion shows a high potential of reducing both fuel consumption and exhaust gas emissions. Many works have been devoted to extend the HCCI operation range in order to maximize its fuel economy benefit. Among them, fuel injection strategies that use fuel reforming to increase the cylinder charge temperature to facilitate HCCI combustion at low engine loads have been proposed. However, to estimate and control an optimal amount of fuel reforming in the cylinder of an HCCI engine proves to be challenging because the fuel reforming process depends on many engine variables. It is conceivable that the amount of fuel reforming can be estimated since it correlates with the combustion phasing which in turn can be measured using a cylinder pressure sensor.
Technical Paper

Concept and Implementation of a Robust HCCI Engine Controller

General Motors recently demonstrated two driveable test vehicles powered by a Homogeneous Charge Compression Ignition (HCCI) engine. HCCI combustion has the potential of a significant fuel economy benefit with reduced after-treatment cost. However, the biggest challenge of realizing HCCI in vehicle applications is controlling the combustion process. Without a direct trigger mechanism for HCCI's flameless combustion, the in-cylinder mixture composition and temperature must be tightly controlled in order to achieve robust HCCI combustion. The control architecture and strategy that was implemented in the demo vehicles is presented in this paper. Both demo vehicles, one with automatic transmission and the other one with manual transmission, are powered by a 2.2-liter HCCI engine that features a central direct-injection system, variable valve lift on both intake and exhaust valves, dual electric camshaft phasers and individual cylinder pressure transducers.
Technical Paper

Progress Toward a Magnesium-Intensive Engine: The USAMP Magnesium Powertrain Cast Components Project

The US Automotive Materials Partnership (USAMP) and the US Department of Energy launched the Magnesium Powertrain Cast Components Project in 2001 to determine the feasibility and desirability of producing a magnesium-intensive engine; a V6 engine with a magnesium block, bedplate, oil pan, and front cover. In 2003 the Project reached mid-point and accomplished a successful Decision Gate Review for entry into the second half (Phase II) of the Project. Three tasks, comprising Phase I were completed: (1) evaluation of the most promising low-cost, creep-resistant magnesium alloys, (2) design of the engine components using the properties of the optimized alloys and creation of cost model to assess the cost/benefit of the magnesium-intensive engine, and (3) identification and prioritization of scientific research areas deemed by the project team to be critical for the use of magnesium in powertrain applications.
Technical Paper

CFRM Concept for Vehicle Thermal System

Condenser, fan, radiator power train cooling module (CFRM) proposed by Delphi Automobile Systems was evaluated in the context of vehicle thermal system analysis. The results from the CFRM configuration were compared with those from the conventional condenser, radiator, and fan power train cooling module (CRFM). The analysis shows that for a typical passenger vehicle, the underhood temperature for the CFRM configuration is more than 10°C lower than its CRFM counterpart when the fan is operating at the same speed of 2500 rpm. This is due mainly to the higher mass flow rate impelled by the fan in the CFRM configuration. At the equal mass flow condition, both the CFRM and the CRFM configurations give similar underhood temperatures; but the fan in the CFRM configuration uses 19% less power, due mainly to the reduction in the fan speed needed to impel the same amount of mass flow rate.