Dohoy Jung

Multi-Zone DI Diesel Spray Combustion Model for Cycle Simulation Studies of Engine Performance and Emissions

A quasi -dimensional, multi-zone, direct injection (DI) diesel combustion model has been developed and implemented in a full cycle simulation of a turbocharged engine. The combustion model accounts for transient fuel spray evolution, fuel-air mixing, ignition, combustion and NO and soot pollutant formation. In the model, the fuel spray is divided into a number of zones, which are treated as open systems. While mass and energy equations are solved for each zone, a simplified momentum conservation equation is used to ca lculate the amount of air entrained into each zone. Details of the DI spray, combustion model and its implementation into the cycle simulation of Assanis and Heywood [1] are described in this paper. The model is validated with experimental data obtained in a constant volume chamber and engines. First, predictions of spray penetration and spray angle are validated against measurements in a pressurized constant volume chamber. Subsequently, predictions of heat release rate, as well as NO and soot emissions are compared with experimental data obtained from representative heavy-duty, turbocharged diesel engines. It is demonstrated that the model can predict the rate of heat release and engine performance with high fidelity. However, additional effort is require d to enhance the fidelity of NO and soot predictions across a wide range of operating conditions.

Engine-in-the-Loop Testing for Evaluating Hybrid Propulsion Concepts and Transient Emissions - HMMWV Case Study

This paper describes a test cell setup for concurrent running of a real engine and a vehicle system simulation, and its use for evaluating engine performance when integrated with a conventional and a hybrid electric driveline/vehicle. This engine-in-the-loop (EIL) system uses fast instruments and emission analyzers to investigate how critical in-vehicle transients affect engine system response and transient emissions. Main enablers of the work include the highly dynamic AC electric dynamometer with the accompanying computerized control system and the computationally efficient simulation of the driveline/vehicle system. The latter is developed through systematic energy-based proper modeling that tailors the virtual model to capture critical powertrain transients while running in real time. Coupling the real engine with the virtual driveline/vehicle offers a chance to easily modify vehicle parameters, and even study two different powertrain configurations. In particular, the paper describes the engine-in-the-loop study of a V8, 6L engine coupled to a virtual 4x4 HighMobility Multipurpose Wheeled Vehicle (HMMWV). The results shed light on critical transients in a conventional powertrain and their effect on NOx and soot emissions. Next, the conventional HMMWV powertrain is replaced with a parallel hybrid electric configuration and two power management strategies are examined. Comparison of the conventional and hybrid propulsion options provides detailed insight into fuel economy – emissions tradeoffs at the vehicle level.

Design of an Advanced Heavy Tactical Truck: A Target Cascading Case Study

The target cascading methodology is applied to the conceptual design of an advanced heavy tactical truck. Two levels are defined: an integrated truck model is represented at the top (vehicle) level and four independent suspension arms are represented at the lower (system) level. Necessary analysis models are developed, and design problems are formulated and solved iteratively at both levels. Hence, vehicle design variables and system specifications are determined in a consistent manner. Two different target sets and two different propulsion systems are considered. Trade-offs between conflicting targets are identified. It is demonstrated that target cascading can be useful in avoiding costly design iterations late in the product development process.

Modelling and simulation of a dual-clutch transmission vehicle to analyse the effect of pump selection on fuel economy

Positive displacement pumps are used in automotive transmissions to provide pressurised fluid to various hydraulic components in the transmission and also lubricate the mechanical components. The output flow of these pumps increases with pump/transmission speed, almost linearly, but the transmission flow requirements often saturate at higher speeds, resulting in excess flow capacity that must be wasted by allowing it to drain back to the sump. This represents a parasitic loss in the transmission leading to a loss in fuel economy. To overcome this issue, variable displacement pumps have been used in the transmission, where the output flow can be reduced by controlling the displacement of the pump. The use of these pumps in automatic transmissions has resulted in better fuel economy as compared with some types of fixed displacement pumps. However, the literature does not fully explore the benefits of variable displacement pumps to a specific type of transmission namely, dual-clutch transmission (DCT), which has different pressure and flow requirements from an epicyclic gear train. This paper presents an analysis of the effect of pump selection on fuel economy in a five-speed DCT of a commercial vehicle. Models of the engine, transmission, and vehicle are developed along with the models of two different types of pumps: a fixed displacement gerotor pump and a variable displacement vane pump. The models are then parameterised using experimental data, and the fuel economy of the vehicle is simulated on a standard driving cycle. The results suggest that the fuel economy benefit obtained by the use of the variable displacement pump in DCTs is comparable to the benefit previously shown for these pumps in automatic transmissions.

Modeling and Simulation of an M1 Abrams Tank with Advanced Track Dynamics and Integrated Virtual Diesel Engine

Abstract New capabilities for simulating a tracked vehicle are presented, including an advanced dynamic track model, a high-fidelity diesel engine system model, and an integration scheme to perform a coupled simulation of vehicle/powertrain dynamics. These capabilities are essential for understanding the interplay of vehicle dynamics and powertrain dynamics, including track vibration (and durability). Suspension response and engine performance. The dynamic track model considers the track as an equivalent continuum and captures longitudinal and transverse track vibrations, static sag, and superposed translation. A low-order discrete model is developed by employing modal track coordinates. The continuum approximation for the track is validated through experiments on a representative track span. This track model is extended and implemented into a commercial multibody dynamics code—DADS—through development of a new user-support-force element that integrates the track element with the vehicle hull and suspensi...

Quasidimensional Modeling of Direct Injection Diesel Engine Nitric Oxide, Soot, and Unburned Hydrocarbon Emissions

In this study we report the development and validation of phenomenological models for predicting direct injection (DI) diesel engine emissions, including nitric oxide (NO), soot, and unburned hydrocarbons (HC), using a full engine cycle simulation. The cycle simulation developed earlier by the authors (D. Jung and D. N. Assanis, 2001, SAE Transactions: Journal of Engines, 2001-01-1246) features a quasidimensional, multizone, spray combustion model to account for transient spray evolution, fuel–air mixing, ignition and combustion. The Zeldovich mechanism is used for predicting NO emissions. Soot formation and oxidation is calculated with a semiempirical, two-rate equation model. Unburned HC emissions models account for three major HC sources in DI diesel engines: (1) leaned-out fuel during the ignition delay, (2) fuel yielded by the sac volume and nozzle hole, and (3) overpenetrated fuel. The emissions models have been validated against experimental data obtained from representative heavy-duty DI diesel engines. It is shown that the models can predict the emissions with reasonable accuracy. Following validation, the usefulness of the cycle simulation as a practical design tool is demonstrated with a case study of the effect of the discharge coefficient of the injector nozzle on pollutant emissions.

An optimization study of manufacturing variation effects on diesel injector design with emphasis on emissions

This paper investigates the effects of manufacturing variations in fuel injectors on the engine performance with emphasis on emissions. The variations are taken into consideration within a Reliability-Based Design Optimization (RBDO) framework. A reduced version of Multi-Zone Diesel engine Simulation (MZDS), MZDS-lite, is used to enable the optimization study. The numerical noise of MZDS-lite prohibits the use of gradient-based optimization methods. Therefore, surrogate models are developed to filter out the noise and to reduce computational cost. Three multi-objective optimization problems are formulated, solved and compared: deterministic optimization using MZDS-lite, deterministic optimization using surrogate models and RBDO using surrogate models. The obtained results confirm that manufacturing variation effects must be taken into account in the early product development stages.

Application of Controllable Electric Coolant Pump for Fuel Economy and Cooling Performance Improvement

The engine cooling system for a typical class 3 pickup truck with a medium duty diesel engine was modeled with a commercial code, GT-Cool in order to explore the benefit of controllable electric pump on the cooling performance and the fuel economy. As the first step, the cooling system model with a conventional mechanical coolant pump was validated with experimental data. After the model validation, the mechanical pump sub-model was replaced with the electric pump submodel and then the potential benefit of the electric pump on fuel economy was investigated with the simulation. Based on coolant flow analysis the modified thermostat hysteresis was proposed to reduce the recirculating flow and electric pump effort, thus enabling assessment of the full power saving potential. It was also demonstrated that the radiator size could be reduced without any cooling performance penalty by replacing mechanical pump with the electric pump and decoupling of the pump speed from engine speed. The predicted results indicate that the cooling system with the electric pump can dramatically reduce the pump power consumption during the FTP 74 driving schedule and that radiator can be down-sized by more than 27% of the original size under grade load condition.Copyright

Design of vehicle cooling system architecture for a heavy duty series-hybrid electric vehicle using numerical system simulations

In this study, numerical simulations of the vehicle cooling system and the vehicle powertrain system of a virtual heavy duty tracked series hybrid electric vehicle (SHEV) is developed to investigate the thermal responses and power consumptions of the cooling system. The output data from the powertrain system simulation are fed into the cooling system simulation to provide the operating conditions of powertrain components. Three different cooling system architectures constructed with different concepts are modeled and the factors that affect the performance and power consumption of each cooling system are identified and compared with each other. The results show that the cooling system architecture of the SHEV should be developed considering various cooling requirements of powertrain components, power management strategy, performance, parasitic power consumption, and the effect of driving conditions. It is also demonstrated that a numerical model of the SHEV cooling system is an efficient tool to assess design concepts and architectures of the system during the early stage of system development.

A Systematic Approach for Dynamic Analysis of Vehicles With Eight or More Speed Automatic Transmission

In this study, a dynamic model of a vehicle with eight or more speed automatic transmission (A/T) has been developed for the analysis of shift quality and dynamic behavior of the vehicle during shift events. Subsystem models for engine, torque converter, automatic transmission, drivetrain, transmission control unit (TCU), and vehicle are developed and integrated with signal information interface. The subsystems included in the model were carefully selected to improve the accuracy of the model by comparing the simulation results with the test data. The systematic modeling approach based on matrix operation proposed in the study enables calibrating and fine-tuning the transmission control unit for shift quality in a virtual vehicle environment. The model presented in the study is validated with the vehicle test data and the comparison shows very good agreement. This paper presents a generalized modeling methodology for multiratio automatic transmissions that require both direct and indirect shifts. The model developed in the study provides a valuable analytical tool for the calibration and tuning of the transmission control unit by allowing quantitative analysis on the dynamic behavior and the performance metrics of an automatic transmission.