Fabrizio Ponti

Full Load Performance Optimization Based on Turbocharger Speed Evaluation via Acoustic Sensing

Turbocharger performance optimization on passenger car engines is particularly challenging, especially in case of severe engine downsizing and downspeeding.On high performance engines (e.g., heavy duty truck applications) turbocharger speed measurement is usually performed with the aim of maximizing engine power and torque, limiting turbocharger over-speed, which is harmful for its durability and reliability. This solution is too expensive for passenger cars, and the turbocharger speed sensor is typically not available.In this work, an innovative and low cost sensing chain for the rotational speed evaluation of the turbocharger is applied. With this information, obtained via an acoustic sensor, a new turbocharger control architecture has been developed to optimize turbocharger performance, in order to improve engine output torque under full load conditions.After a brief description of the new sensing chain and of the electronic components developed to manage this kind of information, the paper shows the new control architecture that takes advantage of the turbocharger speed information.Moreover, experimental results on a small turbocharged Diesel engine for passenger car applications are presented, demonstrating the achieved benefits.Copyright

Development of a Common Rail Diesel Engine Combustion Model for ROHR Real-Time Estimation

Combustion control is a crucial aspect in modern Diesel engines control strategies, mainly due to the requests to increase efficiency and maintain pollutant emissions within the values bounded by standard regulations. In order to perform an accurate combustion control, modern “closed loop” control algorithms require the evaluation of a large number of quantities that provide information about combustion process effectiveness. This work presents a methodology that allows real-time estimation of energy released, during the combustion process, in a Common Rail Multi-Jet Diesel engine. This procedure can be divided in two main steps. The first step consists in the development of a zero-dimensional combustion model based on the linear combination of a proper number of Wiebe functions. In this case, a zero-dimensional approach has been chosen, because it is accurate enough for this analysis and requires low computational efforts. Once the combustion model has been developed, it can be used to determine Rate of Heat Release (RoHR) and the angular position in which 50% of fuel burned within an engine cycle is reached (MFB50). The second section of this work describes the relationships existing between injection parameters (such as Start of Injection, injected fuel quantities, rail pressure...) and the Wiebe parameters identified in the first step of the procedure. The above mentioned relationships have been used to set up correlations that allow estimating Wiebe parameters, therefore ROHR and MFB50, starting from injection parameters. The results obtained in MFB50 estimation are particularly emphasized, because real-time knowledge of this quantity is necessary to feedback a control algorithm for optimal combustion positioning. This work is based on several experimental tests performed on a 2.2 liters Common Rail Multi-Jet Diesel engine. First, experimental tests have been carried out to identify the combustion model and the correlations existing between Wiebe parameters and injection parameters. Then, in order to determine the accuracy of the approach, the complete estimation methodology has been applied to the engine under study. This work describes a methodology for real-time estimation of several quantities that provide important information about combustion process effectiveness (useful, for example, in modern low temperature combustion control systems). No extra cost is needed, because the methodology requires no additional sensor.© 2011 ASME

Combustion Noise Real-Time Evaluation and Processing for Combustion Control

Newly developed Diesel engine control strategies are mainly aimed at pollutant emissions reduction, due to the increasing request for engine-out emissions and fuel consumption reduction. In order to reduce engine-out emissions, the development of closed-loop combustion control algorithms has become crucial. Modern closed-loop combustion control strategies are characterized by two main aspects: the use of high EGR rates (the goal being to obtain highly premixed combustions) and the control of the center of combustion. In order to achieve the target center of combustion, conventional combustion control algorithms correct the measured value by varying Main injection timing.It is possible to obtain a further reduction in pollutant emissions through a proper variation of the injection parameters. Modern Diesel engine injection systems allow designing injection patterns with many degrees of freedom, due to the large number of tuneable injection parameters (such as start and duration of each injection). Each injection parameter’s variation causes variations in the whole combustion process and, consequently, in pollutant emissions production. Injection parameters variations have a strong influence on other quantities that are related to combustion process effectiveness, such as noise radiated by the engine. This work presents a methodology that allows real-time evaluating combustion noise on-board a vehicle. The radiated noise can be evaluated through a proper in-cylinder pressure signal processing. Even though in-cylinder pressure sensor on-board installation is still uncommon, it is believed that in-cylinder pressure measurements will be regularly available on-board thanks to the newly developed piezo-resistive sensors.In order to set-up the methodology, several experimental tests have been performed on a 1.3 liter Diesel engine mounted in a test cell. The engine was run, in each operating condition, both activating and deactivating pre-injections, since pre-injections omission usually produces a decrease in pollutant emissions production (especially in particulate matter) and a simultaneous increase in engine noise. The investigation of the correlation between combustion process and engine noise can be used to set up a closed-loop algorithm for optimal combustion control based on engine noise prediction.Copyright

Estimation Methodology for Automotive Turbochargers Speed Fluctuations Due to Pulsating Flows

Turbocharging technique, together with engine downsizing, will play a fundamental role in the near future as a way to reach the required maximum performance while reducing engine displacement and, consequently, CO2 emissions.However, performing an optimal control of the turbocharging system is very difficult, especially for small engines fitted with a low number of cylinders. This is mainly due to the high turbocharger operating range and to the fact that the flow through compressor and turbine is highly unsteady, while only steady flow maps are usually provided by the manufacturer. In addition, in passenger cars applications, it is usually difficult to optimize turbocharger operating conditions because of the lack of information about pressure/temperature in turbine upstream/downstream circuits and turbocharger rotational speed.This work presents a methodology suitable for instantaneous turbocharger rotational speed determination through a proper processing of the signal coming from an accelerometer mounted on the compressor diffuser or a microphone faced to the compressor. The presented approach can be used to evaluate turbocharger speed mean value and turbocharger speed fluctuation (due to unsteady flow in turbine upstream and downstream circuits), that can be correlated to the power delivered by the turbine.The whole estimation algorithm has been developed and validated for a light duty turbocharged Common-Rail Diesel engine mounted in a test cell. Nevertheless, the developed methodology is general and can be applied to different turbochargers, both for Spark Ignited and Diesel applications.Copyright

Diesel Engine Combustion Sensing Methodology Based on Vibration Analysis

The increasing request for pollutant emissions reduction spawned a great deal of research in the field of combustion control and monitoring. As a matter of fact, newly developed low temperature combustion strategies for Diesel engines allow obtaining a significant reduction both in particulate matter and NOx emissions, combining the use of high EGR rates with a proper injection strategy. Unfortunately, due to their nature, these innovative combustion strategies are very sensitive to in-cylinder thermal conditions. Therefore, in order to obtain a stable combustion, a closed-loop combustion control methodology is needed.Many works demonstrate that a closed-loop combustion control strategy can be based on real-time analysis of in-cylinder pressure trace, that provides important information about the combustion process, such as start of combustion, center of combustion and torque delivered by each cylinder. Nevertheless, cylinder pressure sensors on-board installation is still uncommon, due to problems related to unsatisfactory measurement long term reliability and cost.This paper presents a newly developed approach that allows extracting information about combustion effectiveness through the analysis of engine vibrations. In particular, the developed methodology can be used to obtain an accurate estimation of the indicated quantities of interest combining the information provided by engine speed fluctuations measurement and by the signals coming from acceleration transducers mounted on the engine.This paper also reports the results obtained applying the whole methodology to a light-duty turbocharged Common Rail Diesel engine.Copyright

Remote Combustion Sensing Methodology for Non-Intrusive Cylinder Pressure Estimation in Diesel Engines

Abstract The pollutant emission reduction requested by future pollutant emission policies spawned a great deal of research in the field of combustion monitoring and closed-loop control. This is especially true for Diesel engine, since an important reduction in NOx and particular matter will be required. Many works demonstrate that a major engine-out emission reduction can be achieved through a closed-loop combustion control methodology based on cylinder pressure trace processing. However, the main obstacles to the use of cylinder pressure sensors for on-board application are measurement reliability over time and cost. Therefore, this paper describes the development of a methodology that allows estimating cylinder pressure through a proper combination of the information coming from low-cost sensors mounted on the engine.

Estimation Methodology for Automotive Turbochargers Speed Fluctuations due to Pulsating Flows

Turbocharging technique, together with engine downsizing, will play a fundamental role in the near future as a way to reach the required maximum performance while reducing engine displacement and, consequently, CO2 emissions.However, performing an optimal control of the turbocharging system is very difficult, especially for small engines fitted with a low number of cylinders. This is mainly due to the high turbocharger operating range and to the fact that the flow through compressor and turbine is highly unsteady, while only steady flow maps are usually provided by the manufacturer. In addition, in passenger cars applications, it is usually difficult to optimize turbocharger operating conditions because of the lack of information about pressure/temperature in turbine upstream/downstream circuits and turbocharger rotational speed.This work presents a methodology suitable for instantaneous turbocharger rotational speed determination through a proper processing of the signal coming from an accelerometer mounted on the compressor diffuser or a microphone faced to the compressor. The presented approach can be used to evaluate turbocharger speed mean value and turbocharger speed fluctuation (due to unsteady flow in turbine upstream and downstream circuits), that can be correlated to the power delivered by the turbine.The whole estimation algorithm has been developed and validated for a light duty turbocharged Common-Rail Diesel engine mounted in a test cell. Nevertheless, the developed methodology is general and can be applied to different turbochargers, both for Spark Ignited and Diesel applications.Copyright