Exhaust Mass Research Articles

Investigation of diesel particulate filter performance under typical failure conditions

Diesel particulate filter (DPF) is one of the most effective particulate reduction components in diesel engine aftertreatment systems. However, prolonged utilization of a DPF might result in a deterioration in performance or even failure, such as ash-clogging, melting, breakage, and catalyst deactivation. It is crucial to conduct research on DPF performance degradation across a series of partially failed conditions. In this study, the morphology and chemical composition of the ash in the DPF samples were characterized. The effects of degree-varying clogging and unplugged-breakage failure on exhaust characteristics as well as DPF temperature, filtration and pressure drop characteristics were investigated. Finally, the sensitivity differences between DPF performance parameters and failure index parameters were examined using a canonical correlation analysis (CCA). When four factors were considered, the ash loading index and breakage index had the greatest impact on DPF temperature difference and filtration efficiency, while the exhaust mass flow rate had the greatest impact on pressure drop. Besides, the influence of the DPF inlet temperature on the pressure drop, filtration efficiency, and temperature difference was not significant. These findings contribute to the prediction of DPF performance in partially failed conditions and the development of DPF failure diagnosis methods.

Dynamic characteristics and prediction and control models of subsonic exhaust from a container

This study combines experimental measurements, numerical simulations, and theoretical analysis to investigate the subsonic discharge process in a container under normal temperature and pressure conditions. Experimental data captured the internal pressure dynamics during exhaust at the atmospheric environmental pressure. Numerical simulations using OpenFOAM validated the isothermal exhaust model against the experimental results. Under the assumption of ideal gas and isothermal processes, a nonlinear differential equation was derived to describe the evolution of the container's internal pressure. This equation was simplified for a specific range of pressure ratios, yielding analytical solutions for the internal pressure of the container under both constant and variable external pressures. The effectiveness of the expressions of pressure inside the container was verified by comparing them with experimental and numerical simulation data. We further developed a formula for predicting exhaust mass flow rate, with a prediction error within 9%. An improved formula was subsequently proposed to reduce the error to below 0.4%, enhancing prediction accuracy. For containers with variable external pressure, a method for controlling the exhaust mass flow rate by predicting external pressure changes was proposed, demonstrating its effectiveness in achieving precise control.

A novel thermoelectric generator equipped with magnetized Ferro-Fluid coolant for automobile exhaust heat Recovery: A numerical study

Thermoelectric generator (TEG) is a promising energy-converting device that produces electricity from the temperature difference between a heat source and a heat sink. Enhancing the heat transfer between the TEG and the heat source or heat sink can improve the TEG performance. This study proposes a novel automobile exhaust TEG. The novelty originates from the fact that the proposed TEG uses magnetized Ferro-fluid flow as coolant to enhance cooling rate. Computational fluid dynamics (CFD) approach, through C++ coding in the OpenFOAM open-source software package, is used to assess the system’s performance. The results indicate that employing the magnetized Ferro-fluid flow can favorably reduce the cold side temperature of the TEG module, leading to a 5.5 % voltage rise. It is also shown that to achieve the same voltage enhancement without the use of the proposed magnetized Ferro-fluid flow, a tough task of a 470 % rise in the cold side mass flow rate is required. A parametric study reveals that the effectiveness of using the magnetized Ferro-fluid flow decreases with the exhaust temperature but is almost independent of the exhaust mass flow rate. This study also introduces the best location for the magnetic sources.

Applicability of Variable-Geometry Turbocharger for Diesel Generators under High Exhaust Back Pressure

The exhaust back pressure of diesel engines is becoming increasingly higher nowadays. In order to keep discharging exhaust unhindered and operating smoothly under high exhaust back pressure, a large reduction in engine maximum brake output is often observed, as well as increased fuel consumption and lower combustion efficiency with heavy exhaust smokes. In our previous study, “Applicability of Reducing Valve Timing Overlap for Diesel Engines under High Exhaust Back Pressure”, a reduced valve timing overlap of 12 °CA partially improves the brake output and BSFC for a fixed-geometry turbocharged diesel engine under high exhaust back pressures. A potential solution for restoring the brake output under high exhaust back pressures could be the use of variable-geometry turbochargers. In this study, a variable-geometry turbocharger is applied to a diesel engine to study the engine performance characteristics and applicability, especially the further improvement of brake output and the brake-specific fuel consumption of the engine. Continuing with the results of our previous research, a basic setting of 12 °CA for the valve timing overlap is set up for the subsequent engine performance simulations in this study (using GT-Power SW). Via simulation, exhaust back pressures of 25 kPa, 45 kPa, and 65 kPa gauge are studied for a turbocharged diesel engine. The results for the engine parameters, including brake output, brake-specific fuel consumption, compressor outlet temperature, turbine inlet temperature, intake air mass flow rate, and exhaust mass flow rate are analyzed. The results of the variable-geometry turbocharger, including turbocharger speed, pressure ratios and efficiencies of compressor and turbine are also analyzed. The results indicate that the brake output and brake-specific fuel consumption are effectively improved under full-load operation with an adequate variable-geometry turbocharger rack position. Operable ranges of rack position are also set up for different back pressures.

Aerodynamic noise and its reduction of the marine gas turbine air exhaust system.

The aerodynamic noise of pipelines is an important part of the noise of a ship's system. This paper conducted numerical investigations on the flow and acoustic characteristics of the marine gas turbine exhaust system. The near-field and far-field acoustic characteristics of the internal flow noise of the exhaust system are calculated by employing the Möhring's sound analogy method. In addition, the far-field acoustic characteristics of the external jet flow noise of the exhaust system are calculated by employing the stochastic noise generation and radiation (SNGR) method. Two kinds of protrusions are added to the main nozzle outlet to achieve noise reduction. The internal sound field of the marine exhaust system is dominated by low frequency sound sources, which are more obvious as the exhaust mass flow rate decreases. As for the external sound field of the marine exhaust system, the peak frequency of the far-field noise spectrum decreases with the decrease in the exhaust mass flow rate. The eight periodic protrusions perform better in reducing the internal aerodynamic noise of the exhaust system, while the five aperiodic protrusions perform better in reducing the external jet noise of the exhaust system.

Lumped model for evaluating dynamic filtration and pressure drop behaviour in diesel particulate filters

Particulate matter (PM) emitted from diesel vehicles poses significant risks to the global climate, environment, and human health. Diesel particulate filters (DPF) are currently the only effective aftertreatment device for PM emissions reduction, and it is important to reflect the DPF filtration and pressure drop performance by numerical method. This study established and validated a lumped model based on the spherical packed bed theory and Darcy’s law. The model described the dynamic PM filtration process in DPF, predicting real-time characteristics such as wall porosity, soot load, and pressure drop with improved accuracy. The effects of channel characteristics, monolithic size, and exhaust conditions on filtration and pressure drop performance were also investigated. The results showed that an increase in cell density, wall thickness, DPF length, and diameter is beneficial for increasing filtration efficiency, while DPF inlet temperature and exhaust mass flow rate have adverse effects. Besides, wall thickness, DPF diameter and exhaust flow rate have a more significant impact on total pressure drop. The results improve the dynamic performance prediction in the PM filtration process and provide a theoretical basis for DPF structural optimization.

Research on the method of diesel particulate filters carbon load recognition based on deep learning

Because the carbon load inside a diesel particulate filters (DPF) affects the DPF regeneration, and the carbon load recognition is significant for the particulate matter (PM) emission control. It is necessary to investigate an on-board DPF carbon load recognition method because the carbon load cannot be directly measured by sensors. Aiming to build a DPF carbon load prediction model adopting the deep learning method, this paper proposes a DPF carbon load identification model based on different experimental parameters using a layered one dimension convolutional neural network (1D-CNN) method. To improve data validity, this paper adopts two data-processing methods. The data pre-processing adopts data splicing method to complete the construction of the original sample set, and the data after-processing uses wavelet packet transform method to establish the feature sample sets. The model adopts the optimal feature dataset constructed by three input parameters, i.e., temperature difference, pressure difference, and exhaust mass flow, and has both high training accuracy and test accuracy above 90 %. The pressure difference is the most important influencing input parameter, and the three-parameter sample set (ΔT + ΔP + Q) has great recognition accuracy and good model stability with the high training accuracy and test accuracy as well as less iteration.

Experimental investigation for the operational performance improvement of cryogenic piston-type pump using subcooling effect for liquid hydrogen stations

This paper investigates the impact of subcooling degree and exhaust pressure on the performance of a high-pressure piston pump for pressurizing cryogenic liquid. We fabricate a lab-scale cryogenic liquid pump, conduct experiments with liquid nitrogen, and observe the significant effect of subcooling changes on the pump performance. The lab-scale pump achieves up to 30 bar of exhaust pressure and up to 45.4 g exhaust mass per cycle. This paper introduces the concept of duty cycle for the exhaust mass as a measure of pump performance. The results show that as the subcooling degree and the exhaust pressure increase, the duty cycle and the exhaust mass also increase, improving the pump performance. However, the increase in performance does not happen proportionally, and an optimal subcooling degree must be selected. This paper establishes a generalized computational model to predict the pump performance, achieving the mean absolute errors of 1.8 bar and 0.3 g/s in pressure and mass flow rate, respectively. The model can predict the exhaust mass during one stroke cycle of the pump with an approximation error of 10 %. In addition, the model predicts that pressurizing liquid hydrogen to 900 bar requires subcooling degree and its duty cycle cannot reach 100 % by reduction of specific volume. The findings suggest that subcooling can be used to enhance cryogenic liquid pump performance, and the optimal subcooling degree can be determined during the design of piston pumps to achieve high pressure.

Exploring the dynamic characteristics of thermoelectric generator under fluctuations of exhaust heat

The thermoelectric generator is a potential candidate to recover waste heat from exhaust gas. Regarding the fluctuations of exhaust heat in practical situations, this paper adopts a transient fluid-thermal-electric multiphysics model to investigate the dynamic performance of the thermoelectric generator. Results show that the fluctuation of exhaust temperature has a greater influence on the dynamic characteristics than the fluctuation of exhaust mass flow rate. The dynamic performance of the thermoelectric generator benefits from a decrease in exhaust heat, but suffers when the exhaust heat is in an upward trend. Compared with the constant power and efficiency values of 4.96 W and 2.49 %, the average power and efficiency of the thermoelectric generator show a notable increase of 5.50 % and 70.61 % respectively during a step decrease in exhaust mass flow rate. Similarly, under a linear decrease, the mean power and efficiency experience a rise of 6.04 % and 45.05 % respectively. Besides, periodic exhaust heat can effectively amplify the dynamic output performance, especially for conversion efficiency. When subjected to a sin wave of exhaust mass flow rate, the efficiency experiences a 15.58 % improvement. This work offers a comprehensive understanding of the dynamic characteristics exhibited by the thermoelectric generator employed for waste heat recovery.

Generation of Current in Thermoelectric Generator by Absorption of Heat Using ANSYS Thermal

Thermoelectric power generation is a renewable energy conversion process that directly converts heat to electricity. This research proposes a novel fluid-thermal-electric multi-physics numerical model for predicting the performance of a thermoelectric-producing system. On the ANSYS platform, numerical simulations are done along with the exhaust temperature and mass flow rate. The range of hot end temperatures is from 100 to 450 degrees Celsius. Similarly, the cold end temperature can reach a maximum of 25 degrees Celsius and a minimum of 10 degrees Celsius. When the temperature at the generator's hot end rises, it means the temperature at the generator's cold end must fall. It means both have an inverse relation to each other. The maximum heat absorbed at the hot junction is 32.762 W and the minimum heat absorbed at the hot junction is 4.6305 W. Hence the maximum and minimum current values produced in this paper by the thermoelectric generator are 72.156 A & 10.816 A respectively. The hot side heat exchanger's position of the thermoelectric modules has a significant impact on output. Combining the benefits of many models are advised to construct an inclusive thermoelectric generator system for use in real-world applications.

Taguchi optimization and thermoelectrical analysis of a pin fin annular thermoelectric generator for automotive waste heat recovery

Enhancing thermoelectric performance while minimizing exhaust back pressure is a crucial step in advancing the commercial viability of automotive thermoelectric generators. To achieve high overall performance in a thermoelectric generator, an annular thermoelectric generator equipped with circular pin fins is proposed. A comprehensive three-dimensional numerical model is established to accurately predict thermoelectric performance and thermomechanical behavior. Detailed multi-physics field distribution characteristics are analyzed. Using an L25 orthogonal array, we examine five influencing factors and their five levels: exhaust temperature, exhaust mass flow rate, fin height, fin diameter, and the number of fins. The Taguchi analysis suggests that exhaust temperature is the most influential factor in determining thermoelectric performance, followed by mass flow rate, fin height, fin diameter, and fin number. The optimal values for these parameters are 673 K, 30 g/s, 20 mm, 3 mm, and 420, respectively. Under the optimal design parameters, the net power reaches 34.11 W, representing an 18.7% increase compared to the original design. Moreover, a comparative study is conducted between plate fins and pin fins, showing that the pin fin-based thermoelectric generator exhibits a 5.83% increase in output power and a 4.82% increase in maximum thermal stress compared to the plate fin-based thermoelectric generator.

Potential of Variable Geometry Radial Inflow Turbines as Expansion Machines in Organic Rankine Cycles Integrated with Heavy-Duty Diesel Engines

This work evaluates the feasibility of utilizing an organic Rankine cycle (ORC) for waste heat recovery in internal combustion engines to meet the stringent regulations for reducing emissions resulting from the combustion of fossil fuels. The turbine is the most crucial component of the ORC cycle since it is responsible for power production. In this study, a variable geometry radial inflow turbine is designed to cope with variable exhaust conditions. A variable geometry turbine is simply a radial turbine with different throat openings: 30, 60, and 100%. The exhaust gases of a heavy-duty diesel engine are utilized as a heat source for the ORC system. Different engine operating points are explored, in which each point has a different exhaust temperature and mass flow rate. The results showed that the maximum improvements in engine power and brake specific fuel consumption (BSFC) were 5.5% and 5.3% when coupled to the ORC system with a variable geometry turbine. Moreover, the variable geometry turbine increased the thermal efficiency of the cycle by at least 20% compared to the system with a fixed geometry turbine. Therefore, variable geometry turbines are considered a promising technology in the field and should be further investigated by scholars.

Crank angle-resolved mass flow characterization of engine exhaust pulsations using a Pitot tube and thin-wire thermocouples

Characterizing pulsating flow in high-temperature, high-pressure engine exhaust gas is crucial for the development and optimization of exhaust energy recovery systems. However, the experimental investigation of engine exhaust pulses is challenging due to the difficulties in conducting crank angle-resolved measurements under these unsteady flow conditions. This study contributes to characterizing mass flow pulses from an isolated cylinder exhaust of a heavy-duty diesel engine using a single-pipe measurement system, developed for pulsating flow measurement. A Pitot tube-based approach is adopted to measure exhaust mass flow pulsations, complemented by fast temperature measurements obtained using customized unsheathed thin-wire thermocouples. The on-engine experiment is performed by isolating the in-cylinder trapped mass and the valve opening speed to produce different exhaust pulse waveforms. The adopted approach’s sensitivity in resolving instantaneous mass flows is evaluated analytically and experimentally, considering attenuated temperature measurement effects. Based on exhaust flow measurements, mass flow pulses are analyzed with regard to blow-down and scavenge phases. Under the load sweep, the main waveform change occurs during the blow-down phase, with pulse magnitude increasing with the load. In contrast, as the engine speeds up with a comparable trapped mass, the exhaust mass distribution in the blow-down phase decreases from 75.5% at 700 rpm to 41.9% at 1900 rpm. Additionally, it is observed that cycle-to-cycle variations in mass flow pulses align with combustion stability during the blow-down phase and are predominantly influenced by gas-exchange processes during the scavenge phase.

Numerical investigation of a Coandă-based fluidic thrust vectoring system for subsonic nozzles

The numerical investigation of a novel subsonic thrust concept for fluidic thrust vectoring (FTV) of jet engines is the subject of this publication. FTV possibly offers advantages over conventional mechanical thrust vector control such as decreased complexity, mass and maintenance costs. The operating principle of the FTV nozzles under investigation at the Institute of Jet Propulsion is based on the Coandă effect. The applied concept of thrust vectoring uses dedicated secondary flow channels which are mounted in parallel around the nozzle inner cone or the nozzle wall. If required, bleed air, provided by extraction from the engine compressor or from an external source, is injected at a specific nozzle pressure ratio at the nozzle throat A_8 through these secondary ducts, resulting in the redirection of the secondary jet towards the convex Coandă surface. The interaction between the primary mass flow and the secondary jet leads to a redirection of the primary exhaust mass flow of the engine and thus to a vectoring of the exhaust flow. In this paper, the influence of different nozzle geometric parameters and different operating points are investigated within an extensive parametric study applied to a convergent two-dimensional thrust vectoring nozzle using computational fluid dynamics tools. Thrust vector deflection of up to {20}^{circ } at a maximum secondary to primary mass flow ratio of 10 % is achieved. Reducing this mass flow rate to 5 % still yields vectoring angles of up to {15}^{circ } whereby similar deflection angles compared to conventional mechanical thrust vectoring systems are achievable.

Investigation of the Proton Exchange Membrane Fuel Cell System Cathode Exhaust Gas Composition Based on Test Bed Measurements

Proton exchange membrane fuel cells are gaining increasing importance in vehicle applications. The exhaust gas composition regarding the water and oxygen content and the mass flow are important parameters in fuel cell research (e.g., for designing the test bed, quantifying the hydrogen loss in the exhaust, performing experiments with air pollutants, and monitoring degradation). The exhaust gas composition is also important for vehicle applications (e.g., ensuring safe hydrogen levels in the exhaust). Performing direct measurements of the exhaust mass flow and the relative humidity is challenging due to the high-humidity environment. This article presents a mathematical thermodynamic model used to calculate the exhaust gas mass flow and relative humidity, validated by balancing the gas species composition between cathode inlet and exhaust and by using data measured at the fuel cell system test bed. Four calculation model variations and their analyses are discussed. Furthermore, the exhaust gas composition throughout the fuel cell system operating range is presented. The results of air pollutant experiments provide comprehensive examples for the application of the calculation model. These results demonstrate the suitability of the model for its application in fuel cell system research.

Investigation on the pressure fluctuation of hydrogen Roots pump with a novel reflow structure for fuel cell vehicles

The hydrogen pump is an important component in the hydrogen circulation system of fuel cells. Excessive pulsation at the outlet of the pump is challenging when the Roots hydrogen pump is used, which has a negative impact on the operation performance. To reduce the impact of excessive fluctuations in the hydrogen circulation system, a new structure of reflow grooves is proposed in this paper, which connects the different chambers and adjusts the pressure using a diversion method. The internal flow of the two pumps was studied for comparison, using a three-dimensional simulation model established by Computational Fluid Dynamics (CFD) method. Results showed that the reflow grooves reduce the exhaust pressure and mass flow pulsations, which has a positive effect on the pressure stabilization of the hydrogen circulation system and the anode inlet pressure of the fuel cell stack, contributing to the long durability and stability of the fuel cell stack.

Method to identify fuel sulphur content (FSC) violations of ongoing vessels using CFD modelling

This work presents a methodology to identify the fuel sulphur content (FSC) violations of ongoing vessels, using CFD RANS modelling by implementing the SST k-omega turbulence parameterization to predict the CO2 and SO2 concentrations of plume dispersion. Gaseous pollutants measurements and meteorological data from a ship emission monitoring station in the approach to the port of Hamburg, Germany, have been used for the evaluation of the methodology. Gaseous pollutants concentration, meteorology, identity, and position of passing ships (AIS signal) are the main parameters of the modelling approach. Five ships have been selected to demonstrate and evaluate the method developed. The vessels had different installed power, geometry, and fuel sulphur content. A virtual monitoring station is created for collecting concentration data from the simulated plume and producing concentration time-series. The comparison between modelling and measurements is being performed with integrated numerical values that were produced from the concentration time-series. Modelling, in comparison to measurements for all case studies, provides results for CO2 and SO2 that are in the same order of magnitude, which constitutes the main criterion of validity. In the methodology, the uncertainties are separated into three categories. The first one is related to ambient conditions such as turbulence and temperature profiles. The second concerns ships’ funnel exit characteristics considering the estimation of funnel exit concentration and exhaust mass flow. The third considers the uncertainties that are related to measurements. All details above were used to produce expressions considering the relationship between the FSC and SO2 measuring instruments. The outcome of this work can contribute in finding optimum monitoring location and in estimating plume dispersion close to the water level, e.g. for studying pollutants exchange in the air-water interface.

Determination of hydrogen production performance with waste exhaust gas in marine diesel engines

Steam-methane reformers are one of the most effective environmental systems used to obtain hydrogen with the effect of temperature. This study investigated hydrogen production efficiency numerically with exhaust waste heat. Two different scenarios were studied parametrically at five various engine loads. In this study, steam methane reactor temperature change, hydrogen, CO and CO2 formation amounts were determined according to each exhaust temperature and mass flow rate. As a result of the study, the temperature changes for the scenario 1 and scenario 2 conditions of the steam methane reformer were examined and it was found that the maximum temperature change was 26.7% at the 25% engine load condition. The maximum hydrogen production mass flow rate in proportion to the temperature was approximately 7020 g/h in scenario 2 at 25% engine load condition. Radical CO formation showed that system performance is not realized efficiently enough. The study's significant finding is that increasing the temperature and using catalysts throughout the system increases hydrogen production.

Influence of engine heat source conditions on a small-scale CO2 power generation system

Employing a CO2 power generation system to recover waste heat from engines can reduce fuel consumption and CO2 emissions by producing additional electric power. Nevertheless, the fluctuation in engine operating conditions would cause variations in waste heat sources and affect system performances largely. Hence, an experimental performance test at various engine conditions was implemented by the construction of a small-scale (10 kW) CO2 power generation system. Key components, including the turbine expander and printed circuit heat exchanger, were specifically designed and constructed. The steady-state and transient performances of critical components and the integrated system were carried out. Experimental results of the turbine expander at varying engine conditions revealed the potential for long-term and stable operation under dynamic mass flow rate, inlet temperature, and pressure ratio. The maximum total generation power and efficiency reached 11.55 kW and 58.92%. The printed circuit heat exchanger used to exploit engine exhaust gas showed satisfactory performances in balancing the trade-off between heat transfer and pressure drop. The total pressure drop of engine exhaust gas was lower than 4 kPa determined by both exhaust mass flow and temperature, considering all the variable engine conditions. Despite that a performance penalty was observed at the off-design operation of the integrated system because of the decrease in the waste heat input, the maximum net power and thermal efficiency reached 10.57 kW and 6.59%, respectively, at the engine condition of 1100 rpm, 1200 N m, with a relative improvement of 6.3% in engine brake thermal efficiency.

Study on Diesel Engine Selective Catalytic Reduction Performance at Different Atmospheric Pressures Using the Response Surface Method.

Nitrogen oxides (NO x ) are the main emissions of diesel engines. Selective catalytic reduction (SCR) is the main technology used to reduce NO x emissions from diesel engines. NO x conversion efficiency and ammonia (NH3) escape are the main indicators to evaluate SCR performance. In this work, the effects of diesel engine exhaust temperature and exhaust mass flow rate on the SCR performance under different atmospheric pressures were studied by the combination method of experiment and one-dimensional numerical simulation. At the same time, the response surface method (RSM) was used to analyze the interaction of atmospheric pressure, exhaust temperature, and exhaust mass flow rate on the SCR performance. The results show that the lower the atmospheric pressure, the lower the NO x conversion efficiency and ammonia escape. Under the same exhaust temperature, the lower the atmospheric pressure, the smaller the impact of exhaust mass flow rate on NO x conversion efficiency. According to the RSM results, the optimal NO x conversion efficiency is 78.6% under the combination working conditions of an atmospheric pressure of 100 kPa, exhaust temperature of 395 °C, and exhaust mass flow rate of 250 kg/h, and the NH3 escape is also at a low level of 1.7 g/cycle.