Serpentine ducts used by both military and commercial aircraft can generate significant flow angularity (inlet swirl) and total pressure distortion at the engine face. The impact of inlet swirl on the engine performance and operability must be quantified to ensure safe operation of the aircraft and propulsion system and to define installed deficiencies. Testing is performed over a wide range of flight conditions in the propulsion system flight envelope in order to quantify these effects. Turbine engine compressor models are based on experimental data which can be collected at a limited number of discrete operating points. These models can be used as an analysis tool to optimize the engine test plan and help during validation of the design. The Dynamic Turbine Engine Compressor Code (DYNTECC) utilizes parallel compressor theory and quasi-one-dimensional Euler equations to determine compressor performance. In its standard form, DYNTECC uses user-supplied characteristic stage maps in order to calculate stage forces and shaft work for use in the momentum and energy equations. These maps are typically developed using experimental data. These maps can also be created using characteristic codes such as the 1-D Mean Line Code or the 2-D Streamline Curvature Code. The 1-D Mean Line Code was originally created to predict the performance of individual compressor stages and requires greatly reduced computational time when compared to 2-D and 3-D models. This thesis documents work done to incorporate the 1-D Mean Line code into DYNTECC as a subroutine. The combine DYNTECC/1-D Mean Line Code was then used to analyze the effects of inlet swirl on the fan performance and operability of the Honeywell F109 turbofan engine. The code was calibrated and validated using the F109 cycle deck. Additional code validation was performed using experimental data gathered at the United States Air Force Academy. F109 fan maps were developed for various cases of inlet swirl and results were presented showing shifts in corrected mass flow, fan pressure ratio and fan stability limit.

The Internal Combustion Engines (ICEs) have played a significant role in transportation system to date and are expected to retain a significant market share through to 2050, according to the U.S. Energy Information Administration. Improving the efficiency of the ICEs is one of the most promising and cost-effective approaches to increasing highways vehicle’s fuel economy. The tools to address critical barriers to commercializing higher efficiency, lower emissions, advanced ICEs for passenger and commercial vehicles are increasingly important in the rapidly evolving automotive sector. In this research, a model based optimization strategy is developed for trade-off analysis of parts in Spark Ignition Internal Combustion Engines (SI-ICE). The trade-off analysis tool has been used as a complement to engine mapping to determine the operating region of an engine where a new part could lead to improvements in fuel efficiency, performance, and emissions. To build the engine models, a Design of Experiment (DoE) was developed for performing the engine tests. For each spark plug set, the engine tests were conducted twice with an acceptable control of the parameters that affect engine outputs. The engine torque, Break Specific Fuel Consumption (BSFC) and break specific NOx emission were considered as the engine responses. Engine models were built according to the two-stage modeling strategy by means of black box modeling techniques. The accuracies of the models were 96%, 95% and 92% for the engine torque, BSFC and NOx outputs respectively. For the optimization part, determination of the optimal spark timing for each spark plug was formulated as a multi-objective optimization problem searching for compromises among opposing objectives, i.e. engine torque, emission and fuel consumption. The optimization outputs were in form of Pareto fronts, enabling the selection of the best solutions in terms of different objectives by considering the higher level information. The resulted Pareto fronts of the two spark plugs were compared at different operating points of the Ford Coyote engine and results showed that the two plugs are comparable. The marginal difference was at low load and low speed condition, where the newly designed spark plug was better than the conventional design. / Thesis / Master of Applied Science (MASc)

This thesis presents optimal cooled turbine tip designs that demonstrate a superior performance during an entire engine transient. The improvement of efficiency is obtained by optimizing the shape of the cooled turbine tip, considering all the phenomena associated with clearance variations. Optimal turbine blade tip designs not only enhance the aerodynamic performance, but they also reduce the thermal loads on one of the most vulnerable parts of the gas turbine. A multi-objective optimization was performed using a differential evolution strategy and Computational Fluid Dynamics software to solve Reynolds-Averaged Navier-Stokes equations. The results showed the strong impact of the over-tip coolant flows on the over-tip flow field. A detailed model for the scaling of tip convective heat flux based on Green’s functions was developed to predict the overtip heat flux at various gaps and engine conditions. The turbine aerothermal models integrated with the mathematical model of the entire engine were used to assess the effect of an improved turbine design on the overall gas turbine performance. Finally, this thesis proposes an experimental approach to validate the numerical models of the turbine aerothermal performance. This experimental procedure relies on an extensive computational analysis which resulted in the development of an unprecedented facility. This new facility, built at Purdue University, will be extensively used to evaluate transients with ad-hoc instrumentation designed using CFD. This work proposes a methodology to extrapolate the experimental results to engine conditions, in terms of aerothermal performance focusing on tip flow.

<p>Since measurements in engine test cells are closely coupled with high costs it is of interest to use physically interpretable engine models instead of engine maps. Such engine models can also be used to do off-line tests of how new or altered components affects engine performance.</p><p>In the thesis an existing mean value engine model will be extended with a model of a compressor bypass valve. A controller for that valve will also be developed. The purpose with that controller is to save torque and boost pressure but at the same time avoid having the compressor entering surge during fast closing transients in the throttle position.</p><p>Both the extension and controller is successfully developed and implemented. The extension lowers the pressure after the compressor and increases the pressure before the compressor when the bypass valve is being opened and the controller shows better results in simulations than the controller used in the research lab. By using the proposed controller, as much as 5 percent higher torque can be achieved in simulations.</p><p>Finally there is a discussion on wastegate control alternatives and the use of TOMOC for optimization of wastegate control.</p>

<p>Mean Value Engine Modeling (MVEM) is used to make engine control development less expensive. With more and more cars equipped with turbocharged engines good turbo MVEM models are needed. A turbocharger consists of two major parts: turbine and compressor. Whereas the turbine is relatively durable, there exist phenomenons on the compressor that can destroy the turbocharger. One of these is surge.</p><p>Several compressor models are developed in this thesis. Methods to determine the compressor model parameters are proposed and discussed both for the stable operating range as well as for the surge region of a compressor map. For the stationary region methods to automatically parameterize the compressor model are developed. For the unstable surge region methods to get good agreement for desired surge properties are discussed. The parameter sensitivity of the different surge properties is also discussed. A validation of the compressor model shows that it gives good agreement to data, both for the stationary region as well as the surge region.</p><p>Different open loop and closed loop controllers as well as different performance variables are developed and discussed. A benchmark is developed, based on a measured vehicle acceleration, and the control approaches are compared using this benchmark. The best controller is found to be a open loop controller based on throttle and surge valve mass flow.</p>

Since measurements in engine test cells are closely coupled with high costs it is of interest to use physically interpretable engine models instead of engine maps. Such engine models can also be used to do off-line tests of how new or altered components affects engine performance. In the thesis an existing mean value engine model will be extended with a model of a compressor bypass valve. A controller for that valve will also be developed. The purpose with that controller is to save torque and boost pressure but at the same time avoid having the compressor entering surge during fast closing transients in the throttle position. Both the extension and controller is successfully developed and implemented. The extension lowers the pressure after the compressor and increases the pressure before the compressor when the bypass valve is being opened and the controller shows better results in simulations than the controller used in the research lab. By using the proposed controller, as much as 5 percent higher torque can be achieved in simulations. Finally there is a discussion on wastegate control alternatives and the use of TOMOC for optimization of wastegate control.

Modern engines are faced with increasingly stringent requirements for reduced fuel consumptionand lower emissions. A technique which can partly be used to reduce emissionsof nitrogen oxides is recirculation of combusted gases (Exhaust Gas Recirculation, EGR). Ingasoline engines, it also has the advantage that it can save fuel by reducing pumping losses.To large mixture of EGR in the air to the cylinders will however affect the combustion stabilitynegatively. To investigate EGR rate and dynamics with respect to different actuatorinputs, the thesis develops an engine model that includes EGR. The model focus on the airflow in the engine and extends an existing mean value engine model. Two types of EGRsystemare investigated. They are short-route EGR which is implemented between intakemanifold and exhaust manifold and long-route EGR which is implemented between compressorand turbine. The work provides a simulation study that compares both stationaryand transient properties of the two EGR-systems, such as fuel consumption, maximum EGR,and rise time with respect to different actuators.

Mean Value Engine Modeling (MVEM) is used to make engine control development less expensive. With more and more cars equipped with turbocharged engines good turbo MVEM models are needed. A turbocharger consists of two major parts: turbine and compressor. Whereas the turbine is relatively durable, there exist phenomenons on the compressor that can destroy the turbocharger. One of these is surge. Several compressor models are developed in this thesis. Methods to determine the compressor model parameters are proposed and discussed both for the stable operating range as well as for the surge region of a compressor map. For the stationary region methods to automatically parameterize the compressor model are developed. For the unstable surge region methods to get good agreement for desired surge properties are discussed. The parameter sensitivity of the different surge properties is also discussed. A validation of the compressor model shows that it gives good agreement to data, both for the stationary region as well as the surge region. Different open loop and closed loop controllers as well as different performance variables are developed and discussed. A benchmark is developed, based on a measured vehicle acceleration, and the control approaches are compared using this benchmark. The best controller is found to be a open loop controller based on throttle and surge valve mass flow.

Indiana University-Purdue University Indianapolis (IUPUI) / Stringent regulatory requirements and modern diesel engine technologies have engaged automotive manufacturers and researchers in accurately predicting and controlling diesel engine-out emissions. As a result, engine control systems have become more complex and opaquer, increasing the development time and costs. To address this challenge, Model-based control methods are an effective way to deal with the criticality of the system study and controls. And physics-based combustion engine modeling is a key to achieve it. This thesis focuses on development and validation of a physics-based model for both engine and emissions using model-based design tools from MATLAB & Simulink. Engine model equipped with exhaust gas circulation and variable geometry turbine is adopted from the previously done work which was then integrated with the combustion and emission model that predicts the heat release rates and NOx emission from engine. Combustion model is designed based on the mass fraction burnt from CA10 to CA90 and then NOx predicted using the extended Zeldovich mechanism. The engine models are tuned for both steady state and dynamics test points to account for engine operating range from the performance data. Various engine and combustion parameters are estimated using parameter estimation toolbox from MATLAB and Simulink by applying the least squared solver to minimize the error between measured and estimated variables. This model is validated against the virtual engine model developed in GT-power for Cummins 6.7L turbo diesel engine. To account for the harmonization of the testing cycles to save engine development time globally, a world harmonized stationary cycle (WHSC) is used for the validation. Sub-systems are validated individually as well as in a loop with a complete model for WHSC. Engine model validation showed promising accuracy of more than 88.4 percent on average for the desired parameters required for the NOx prediction. NOx estimation is accurate for the cycle except the warm-up and cool-down phase. However, NOx prediction during these phases is limited due to actual NOx measured data for tuning the model for real-time NOx estimation. Results are summarized at the end to compare the trend of NOx estimation from the developed combustion and emission model to show the accuracy of in-cylinder parameters and required for the NOx estimation.

Engine control becomes increasingly important in newer cars. It is therefore interesting to investigate if a relatively new control method as Model Predictive Control (MPC) can be useful in engine control in the future. One of the advantages of MPC is that it can handle contraints explicitly. In this thesis basics on turbocharged engines and the underlying theory of MPC is presented. Based on a nonlinear mean value engine model, linearized at multiple operating points, we then implement both a linear and a nonlinearMPC strategy and highlight implementation issues. The implemented MPC controllers calculate optimal wastegate position in order to track a requested torque curve and still make sure that the constraints on turbocharger speed and minimum and maximum opening of the wastegate are fulfilled.