Erasmo Recco - Academia.edu (original) (raw)

Papers by Erasmo Recco

Research paper thumbnail of Remote Combustion Sensing in Diesel Engine via Vibration Measurements

Improvement Trends for Internal Combustion Engines, 2018

An efficient control of the combustion process is required in order to comply with regulations on... more An efficient control of the combustion process is required in order to comply with regulations on pollutant emissions from internal combustion engines. Literature presents investigations devoted to explore the potentiality of externally mounted sensor (speed sensor, microphone, and accelerometer) for combustion diagnosis. A relationship exists between the combustion event measured via an in-cylinder pressure transducer and engine block vibration measured via an accelerometer. Time and frequency domain processing of acquired signals highlighted the correlation between parameters able to characterize the combustion development and features derived from the engine block vibration data. A methodology was developed by the authors that demonstrated to be suitable for real-time estimation of combustion progress based on engine vibration. A two-cylinder common rail diesel engine of small displacement was tested; two configurations were investigated, naturally aspirated, and turbocharged. The in-cylinder pressure and block vibration signals were acquired and processed in time and frequency domains. The vibrational components mainly related to the combustion process were extracted, and indicators of the combustion positioning were computed. The angular positions of start of combustion (SOC) and MFB50 computed via the heat release curve by means of the in-cylinder pressure measurements were compared to those obtained by means of the accelerometer signal. High correlation coefficients were obtained for the data acquired during the testing of both naturally aspirated and turbocharged configurations in the complete engine operative field.

Research paper thumbnail of Le attività della Meccanica a Roma Tre

Research paper thumbnail of Turbocharging a small displacement diesel engine for urban vehicles

Turbochargers are widely used in automotive industry to enhance the engine power output without t... more Turbochargers are widely used in automotive industry to enhance the engine power output without the need to increase the engine displacement, thus allowing the adoption of smaller powerful engines. This paper presents a development of a naturally aspirated small displacement diesel engine, a light and compact engine that has a leading role in micro-cars in urban areas. The engine was equipped with a small turbocharger in order to improve its power output with the objective of letting this engine equip not only microcars but also urban vehicles. The engine operative range was extended aimed at including engine speed values where the turbocharger has the positive effect of increasing the engine volumetric efficiency. An experimentation was performed in the complete engine operative field of both naturally and turbocharged configurations. The engine performance and emissions were analyzed. The impact of engine configuration on the total number and size distribution of particle emission...

Research paper thumbnail of Automotive turbocharger speed estimation via vibration analysis for combustion optimization

The need of complying with the more stringent limits posed by legislation on exhaust emissions of... more The need of complying with the more stringent limits posed by legislation on exhaust emissions of internal combustion engines and of reducing fuel consumption makes monitoring of engine operating condition an essential feature. Several strategies have been proposed to this purpose, using different types of sensors for the direct/indirect combustion sensing and for providing a feedback signal with the final aim of process optimization. It has been demonstrated that in a turbocharged engine a relationship exists between the rotational speed of the turbocharger and the thermo-fluid dynamic condition of the gases at the exhaust valve opening. Such a relation allows establishing a link between the engine operating conditions in terms of speed, load and injection settings and the turbocharger speed. This work presents a methodology devoted to extract from an accelerometer signal, the mean turbocharger rotational speed with the final aim of realizing a non-intrusive control of combustion process, in which the variation of combustion development as regards nominal condition is detected via the estimation of the turbocharger speed.

Research paper thumbnail of Caratterizzazione Del Processo DI Combustione in Motori Diesel Mediante Misure DI Vibrazione

Research paper thumbnail of Combustion monitoring through vibrational data in a turbocharged city car engine

Research paper thumbnail of Effect of Waste Cooking Oil Biodiesel Blends on Performance and Emissions from a CRDI Diesel Engine

Improvement Trends for Internal Combustion Engines, 2018

The employment of biofuels in blends with diesel oil proved to attain a reduced environmental imp... more The employment of biofuels in blends with diesel oil proved to attain a reduced environmental impact without compromising the engine performance. Among biofuels, waste cooking oil offers the advantages of its reduced raw material cost in comparison with fresh vegetable oil cost; it also eliminates the environmental impacts caused by its disposal. Although a great number of researches has been devoted to biodiesel combustion in engines and pollutant emissions, few studies can be found on light duty diesel engine equipped with up-to-date technologies. This work aims at investigating the impact of waste cooking oil percentage in blends with diesel oil on the performance and emission characteristics of an up-to-date light and compact common rail diesel engine whose main application is in microcars and in urban vehicles. A comprehensive experimental activity was performed in the engine complete operative field. The comparison of the results with those obtained with standard ultralow-sulfur diesel highlighted that the engine performance was quite similar for B20 and diesel oil. B40 suffered for the lower caloric value in regard to diesel. A reduction in CO and HC was obtained with biodiesel blends, along with an increase in NO x. Particulate emissions were also reduced for biodiesel blends; the mean size of particles was smaller as regards diesel oil.

Research paper thumbnail of Emission Performance of a Diesel Engine Fuelled with Petrol Diesel, Green Diesel, and Waste Cooking Oil Blends

Journal of Combustion, 2018

The purpose of this paper is to conduct an experimental research on the impact of mixing ratio of... more The purpose of this paper is to conduct an experimental research on the impact of mixing ratio of biodiesel from waste cooking oil and an innovative diesel fuel (in which a renewable component is contained) on the emissions of an up-to-date light and compact small engine that has a leading role in city cars and urban vehicles. Two blends’ mixing ratios (20% and 40% by volume) were tested and the results were compared to those obtained when the engine was operated with low sulfur diesel (ULSD) and ULSD blended with 15% by volume of renewable diesel. The results indicate that diesel+ enhances CO and HC emissions in the exhaust as regards ULSD. Blending diesel+ with WCO causes a further reduction for most of the engine operative field. Concerning particulate emission, accumulation mode dominates for all fuels. Diesel+ is always characterized by lower mean diameters as regards ULSD. The addition of WCO further reduces the court mean diameter. Particle number concentration obtained by fu...

Research paper thumbnail of Vibration analysis to estimate turbocharger speed fluctuation in diesel engines

Energy Procedia, 2018

District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

Research paper thumbnail of Turbocharger speed estimation via vibration measurements for combustion sensing

Energy Procedia, 2017

District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

Research paper thumbnail of Accelerometer measurement for MFB evaluation in multi-cylinder diesel engine

Energy, 2017

Indirect methods have great potential for engine diagnosis. Several methodologies have been propo... more Indirect methods have great potential for engine diagnosis. Several methodologies have been proposed in the past in which indirect measurements are used for combustion sensing. This paper presents the results of the application of a methodology developed by the authors in which an accelerometer mounted on the engine block is used to characterize the combustion development in a multi-cylinder common rail diesel engine. The high correlation between accelerometer and in-cylinder pressure data allowed to use the vibration signals to evaluate the angular positions where: the combustion starts, 50% of fuel is burned over an engine cycle (MFB50) and the combustion process ends (MFB95) in two of the engine cylinders. The great accuracy of the predictions (the square value of the correlation coefficient was always higher than 0,97) demonstrated that a single accelerometer can be used in control algorithms for the optimal positioning of the combustion process in more than one cylinder.

Research paper thumbnail of Soot Particles Experimental Characterization During Cold Start of a Micro Car Engine

Energy Procedia, 2016

Substantial amount of pollutants is emitted during the vehicle start-up, since the engine has not... more Substantial amount of pollutants is emitted during the vehicle start-up, since the engine has not reached its optimal operating temperature. In urban traffic environment, the engine emissions during its warming up until it reaches a hot stabilized mode are an important source of major air pollutants. Existing literature indicates that:-in recent years the vehicle emissions have been reduced significantly, while those related to engine cold starts still remain high;-emission levels during engine start-up are deeply influenced by the vehicle characteristics. Most of studies are related to diesel engines equipped with high efficiency DPFs, gasoline port fuel injected and gasoline direct injected engines equipped with three-way-catalysts. This paper aims at characterizing pollutants and solid particles emissions from a low displacement two cylinder diesel engine, whose main application is in city cars and urban vehicles. During tests, measurements started at the time of the engine cold startup; transient conditions of load and speed were imposed to the engine. A characterization of solid particle was performed, in terms of particle number and size distribution for three engine thermal conditions: cold, warm and hot starts.

Research paper thumbnail of Analysis of the Relationship between Noise Emission and In-Cylinder Pressure in a Small Displacement Diesel Engine

SAE Technical Paper Series, 2014

Research paper thumbnail of Combustion and Vibration Characteristics in a Small Displacement Diesel Engine Fueled with Biodiesel Blends

SAE Technical Paper Series, 2013

Research paper thumbnail of Diesel Engine Combustion Monitoring through Block Vibration Signal Analysis

SAE Technical Paper Series, 2009

Research paper thumbnail of Diesel Combustion Analysis via Block Vibration during Engine Transient Operation

SAE Technical Paper Series, 2013

Research paper thumbnail of Acoustic Assessment in a Small Displacement Diesel Engine

SAE Technical Paper Series, 2014

Research paper thumbnail of Vibration Processing to Optimize Pressure Development in CR Diesel Engine

SAE Technical Paper Series, 2011

Research paper thumbnail of Accelerometer Measurements to Optimize the Injection Strategy

SAE Technical Paper Series, 2012

Research paper thumbnail of Combustion diagnosis via block vibration signal in common rail diesel engine

International Journal of Engine Research, 2014

This article presents a diagnostic technique in which nonintrusive measurements are used with the... more This article presents a diagnostic technique in which nonintrusive measurements are used with the aim of indirect characterization of the combustion process of an internal combustion diesel engine. The developed technique is based on the vibration signal coming from a mono-axial accelerometer placed in a selected location of the engine block. Such a location is able to guarantee high sensitivity to vibration caused by forces directly linked to the combustion process and low sensitivity to all the other excitation sources. The technique is applied to the signals acquired during two series of experimental tests, carried out on the same kind of engine (multi-cylinder diesel engine, equipped with common rail injection system), in two separate engine test facilities in order to test the engine stand-alone and the engine dressed up with the integrated automatic transmission, aimed at reproducing its real operation condition (it is mainly employed in mini-car sector application). The obtai...

Research paper thumbnail of Remote Combustion Sensing in Diesel Engine via Vibration Measurements

Improvement Trends for Internal Combustion Engines, 2018

An efficient control of the combustion process is required in order to comply with regulations on... more An efficient control of the combustion process is required in order to comply with regulations on pollutant emissions from internal combustion engines. Literature presents investigations devoted to explore the potentiality of externally mounted sensor (speed sensor, microphone, and accelerometer) for combustion diagnosis. A relationship exists between the combustion event measured via an in-cylinder pressure transducer and engine block vibration measured via an accelerometer. Time and frequency domain processing of acquired signals highlighted the correlation between parameters able to characterize the combustion development and features derived from the engine block vibration data. A methodology was developed by the authors that demonstrated to be suitable for real-time estimation of combustion progress based on engine vibration. A two-cylinder common rail diesel engine of small displacement was tested; two configurations were investigated, naturally aspirated, and turbocharged. The in-cylinder pressure and block vibration signals were acquired and processed in time and frequency domains. The vibrational components mainly related to the combustion process were extracted, and indicators of the combustion positioning were computed. The angular positions of start of combustion (SOC) and MFB50 computed via the heat release curve by means of the in-cylinder pressure measurements were compared to those obtained by means of the accelerometer signal. High correlation coefficients were obtained for the data acquired during the testing of both naturally aspirated and turbocharged configurations in the complete engine operative field.

Research paper thumbnail of Le attività della Meccanica a Roma Tre

Research paper thumbnail of Turbocharging a small displacement diesel engine for urban vehicles

Turbochargers are widely used in automotive industry to enhance the engine power output without t... more Turbochargers are widely used in automotive industry to enhance the engine power output without the need to increase the engine displacement, thus allowing the adoption of smaller powerful engines. This paper presents a development of a naturally aspirated small displacement diesel engine, a light and compact engine that has a leading role in micro-cars in urban areas. The engine was equipped with a small turbocharger in order to improve its power output with the objective of letting this engine equip not only microcars but also urban vehicles. The engine operative range was extended aimed at including engine speed values where the turbocharger has the positive effect of increasing the engine volumetric efficiency. An experimentation was performed in the complete engine operative field of both naturally and turbocharged configurations. The engine performance and emissions were analyzed. The impact of engine configuration on the total number and size distribution of particle emission...

Research paper thumbnail of Automotive turbocharger speed estimation via vibration analysis for combustion optimization

The need of complying with the more stringent limits posed by legislation on exhaust emissions of... more The need of complying with the more stringent limits posed by legislation on exhaust emissions of internal combustion engines and of reducing fuel consumption makes monitoring of engine operating condition an essential feature. Several strategies have been proposed to this purpose, using different types of sensors for the direct/indirect combustion sensing and for providing a feedback signal with the final aim of process optimization. It has been demonstrated that in a turbocharged engine a relationship exists between the rotational speed of the turbocharger and the thermo-fluid dynamic condition of the gases at the exhaust valve opening. Such a relation allows establishing a link between the engine operating conditions in terms of speed, load and injection settings and the turbocharger speed. This work presents a methodology devoted to extract from an accelerometer signal, the mean turbocharger rotational speed with the final aim of realizing a non-intrusive control of combustion process, in which the variation of combustion development as regards nominal condition is detected via the estimation of the turbocharger speed.

Research paper thumbnail of Caratterizzazione Del Processo DI Combustione in Motori Diesel Mediante Misure DI Vibrazione

Research paper thumbnail of Combustion monitoring through vibrational data in a turbocharged city car engine

Research paper thumbnail of Effect of Waste Cooking Oil Biodiesel Blends on Performance and Emissions from a CRDI Diesel Engine

Improvement Trends for Internal Combustion Engines, 2018

The employment of biofuels in blends with diesel oil proved to attain a reduced environmental imp... more The employment of biofuels in blends with diesel oil proved to attain a reduced environmental impact without compromising the engine performance. Among biofuels, waste cooking oil offers the advantages of its reduced raw material cost in comparison with fresh vegetable oil cost; it also eliminates the environmental impacts caused by its disposal. Although a great number of researches has been devoted to biodiesel combustion in engines and pollutant emissions, few studies can be found on light duty diesel engine equipped with up-to-date technologies. This work aims at investigating the impact of waste cooking oil percentage in blends with diesel oil on the performance and emission characteristics of an up-to-date light and compact common rail diesel engine whose main application is in microcars and in urban vehicles. A comprehensive experimental activity was performed in the engine complete operative field. The comparison of the results with those obtained with standard ultralow-sulfur diesel highlighted that the engine performance was quite similar for B20 and diesel oil. B40 suffered for the lower caloric value in regard to diesel. A reduction in CO and HC was obtained with biodiesel blends, along with an increase in NO x. Particulate emissions were also reduced for biodiesel blends; the mean size of particles was smaller as regards diesel oil.

Research paper thumbnail of Emission Performance of a Diesel Engine Fuelled with Petrol Diesel, Green Diesel, and Waste Cooking Oil Blends

Journal of Combustion, 2018

The purpose of this paper is to conduct an experimental research on the impact of mixing ratio of... more The purpose of this paper is to conduct an experimental research on the impact of mixing ratio of biodiesel from waste cooking oil and an innovative diesel fuel (in which a renewable component is contained) on the emissions of an up-to-date light and compact small engine that has a leading role in city cars and urban vehicles. Two blends’ mixing ratios (20% and 40% by volume) were tested and the results were compared to those obtained when the engine was operated with low sulfur diesel (ULSD) and ULSD blended with 15% by volume of renewable diesel. The results indicate that diesel+ enhances CO and HC emissions in the exhaust as regards ULSD. Blending diesel+ with WCO causes a further reduction for most of the engine operative field. Concerning particulate emission, accumulation mode dominates for all fuels. Diesel+ is always characterized by lower mean diameters as regards ULSD. The addition of WCO further reduces the court mean diameter. Particle number concentration obtained by fu...

Research paper thumbnail of Vibration analysis to estimate turbocharger speed fluctuation in diesel engines

Energy Procedia, 2018

District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

Research paper thumbnail of Turbocharger speed estimation via vibration measurements for combustion sensing

Energy Procedia, 2017

District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

Research paper thumbnail of Accelerometer measurement for MFB evaluation in multi-cylinder diesel engine

Energy, 2017

Indirect methods have great potential for engine diagnosis. Several methodologies have been propo... more Indirect methods have great potential for engine diagnosis. Several methodologies have been proposed in the past in which indirect measurements are used for combustion sensing. This paper presents the results of the application of a methodology developed by the authors in which an accelerometer mounted on the engine block is used to characterize the combustion development in a multi-cylinder common rail diesel engine. The high correlation between accelerometer and in-cylinder pressure data allowed to use the vibration signals to evaluate the angular positions where: the combustion starts, 50% of fuel is burned over an engine cycle (MFB50) and the combustion process ends (MFB95) in two of the engine cylinders. The great accuracy of the predictions (the square value of the correlation coefficient was always higher than 0,97) demonstrated that a single accelerometer can be used in control algorithms for the optimal positioning of the combustion process in more than one cylinder.

Research paper thumbnail of Soot Particles Experimental Characterization During Cold Start of a Micro Car Engine

Energy Procedia, 2016

Substantial amount of pollutants is emitted during the vehicle start-up, since the engine has not... more Substantial amount of pollutants is emitted during the vehicle start-up, since the engine has not reached its optimal operating temperature. In urban traffic environment, the engine emissions during its warming up until it reaches a hot stabilized mode are an important source of major air pollutants. Existing literature indicates that:-in recent years the vehicle emissions have been reduced significantly, while those related to engine cold starts still remain high;-emission levels during engine start-up are deeply influenced by the vehicle characteristics. Most of studies are related to diesel engines equipped with high efficiency DPFs, gasoline port fuel injected and gasoline direct injected engines equipped with three-way-catalysts. This paper aims at characterizing pollutants and solid particles emissions from a low displacement two cylinder diesel engine, whose main application is in city cars and urban vehicles. During tests, measurements started at the time of the engine cold startup; transient conditions of load and speed were imposed to the engine. A characterization of solid particle was performed, in terms of particle number and size distribution for three engine thermal conditions: cold, warm and hot starts.

Research paper thumbnail of Analysis of the Relationship between Noise Emission and In-Cylinder Pressure in a Small Displacement Diesel Engine

SAE Technical Paper Series, 2014

Research paper thumbnail of Combustion and Vibration Characteristics in a Small Displacement Diesel Engine Fueled with Biodiesel Blends

SAE Technical Paper Series, 2013

Research paper thumbnail of Diesel Engine Combustion Monitoring through Block Vibration Signal Analysis

SAE Technical Paper Series, 2009

Research paper thumbnail of Diesel Combustion Analysis via Block Vibration during Engine Transient Operation

SAE Technical Paper Series, 2013

Research paper thumbnail of Acoustic Assessment in a Small Displacement Diesel Engine

SAE Technical Paper Series, 2014

Research paper thumbnail of Vibration Processing to Optimize Pressure Development in CR Diesel Engine

SAE Technical Paper Series, 2011

Research paper thumbnail of Accelerometer Measurements to Optimize the Injection Strategy

SAE Technical Paper Series, 2012

Research paper thumbnail of Combustion diagnosis via block vibration signal in common rail diesel engine

International Journal of Engine Research, 2014

This article presents a diagnostic technique in which nonintrusive measurements are used with the... more This article presents a diagnostic technique in which nonintrusive measurements are used with the aim of indirect characterization of the combustion process of an internal combustion diesel engine. The developed technique is based on the vibration signal coming from a mono-axial accelerometer placed in a selected location of the engine block. Such a location is able to guarantee high sensitivity to vibration caused by forces directly linked to the combustion process and low sensitivity to all the other excitation sources. The technique is applied to the signals acquired during two series of experimental tests, carried out on the same kind of engine (multi-cylinder diesel engine, equipped with common rail injection system), in two separate engine test facilities in order to test the engine stand-alone and the engine dressed up with the integrated automatic transmission, aimed at reproducing its real operation condition (it is mainly employed in mini-car sector application). The obtai...