Exhaust Mass Flow Rate 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.

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.

Power prediction and packed bed heat storage control for marine diesel engine waste heat recovery

The generation capability of the waste heat recovery system cannot be fully utilized by relying solely on the exhaust gas, as the mass flow rate and temperature of exhaust fluctuate in real time. The volatility of ship engine conditions and the instability of power demand can pose a challenge to real-time power allocation. Developing integrated prediction and control methods for power allocation becomes necessary. An integrated system is devised to fully utilize waste energy from marine diesel engines by combining a regenerative organic Rankine cycle with a controllable packed bed. The trends of thermodynamic properties and dynamic charging and discharging processes of the system are analyzed. To provide a plausible management strategy for allocating power in real time, a bidirectional long-short-term memory network power prediction method based on improved complete ensemble empirical mode decomposition with adaptive noise and improved marine predator algorithm is proposed. It is found that 315.6 kW of power can be obtained from the system, and its payback period is 6.84 years. In addition, by using the proposed model, the system can reduce diesel engine power generation. The findings suggest the proposed solution is a viable and meaningful strategy.

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.

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.

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.

Development of two transient models for predicting dynamic response characteristics of an automobile thermoelectric generator system

In this work, two transient models, including a transient fluid-thermal-electric multiphysics numerical model and a hybrid transient CFD-analytical model, are proposed to predict the dynamic performance of the automobile thermoelectric generator system in practical applications. The transient models consider the heat source fluctuation, temperature dependence of thermoelectric materials, and the coupling of different physical fields, which can simulate the actual working conditions. According to the model results, the dynamic output power varies smoothly and is mainly related to the exhaust temperature due to thermal inertia, whereas the dynamic conversion efficiency fluctuates sharply and is mainly related to the exhaust mass flow rate. Compared with the transient fluid-thermal-electric multiphysics numerical model, the output performance obtained by the hybrid transient CFD-analytical model is overestimated, especially for conversion efficiency, and the average errors of output power and conversion efficiency between the two models are 2.90% and 13.58% respectively. Besides, the output performance predicted by transient models is lower than that expected in a steady-state analysis, and the transient models are experimentally verified. This work fills the gap of theoretical models for predicting the dynamic response characteristics, and the findings are helpful to understand the transient performance of automobile thermoelectric generator systems.

Waste Heat Recovery in a Compression Ignition Engine for Marine Application Using a Rankine Cycle Operating with an Innovative Organic Working Fluid

The exhaust heat of energy conversion systems can be usefully recovered by Organic Rankine Cycles (ORC) instead of wasting it into the environment, with benefits in terms of system efficiency and environmental impact. Rankine cycle technology, consolidated in stationary power plants, has not yet spread out into transport applications due to the layout limitations and to the necessity of containing the size and weight of the ORC system. The authors investigated an ORC system bottoming a compression ignition engine for marine application. The exhaust mass flow rate and temperature, measured at different engine loads, have been used as inputs for modeling the ORC plant in a Simulink environment. An energy and exergy analysis of the ORC was performed, as well as the evaluation of the ORC power at different engine loads. Two different working fluids were considered: R1233zd(e), an innovative fluid belonging to the class of hydrofluoroolefin, still in development but interesting due to its low flammability, health hazard, and environmental impact, and R601, a hydrocarbon showing a benchmark thermodynamic performance but highly flammable, considered as a reference for comparison. Three plant configurations were investigated: single-pressure, dual-pressure, and reheating. The results demonstrated that the dual-pressure configuration achieves the highest exploitation of exhaust heat. R1233zd(e) produced an additional mechanical power of 8.0% with respect to the engine power output, while, for R601, the relative contribution of the ORC power was 8.7%.

Soot Distribution Characteristics and Its Influence Factors in Burner-Type Regeneration Diesel Particulate Filter

The burner-type regeneration diesel particulate filter is one of the most widely used diesel particulate filters. Using AVL FIRE, a 3D model of a burner-type regeneration diesel particulate filter (DPF) was established, and simulation analyses were carried out. The effects of the exhaust parameters (temperature, exhaust mass flow rate, and soot load) and the structural parameters (channel density, inlet/outlet channel ratio, and the length–diameter ratio) on soot distribution (soot mass concentration and soot thickness) were analyzed. The results show that the soot distribution characteristics of regenerative DPF with a burner are as follows: the soot mass concentration first rapidly rises to the maximum value and then rapidly decreases to a low value, and the dust thickness gradually increases with the increase in location. With the increase in exhaust mass flow rate and soot load, soot mass concentration and soot thickness increase. With the increase in temperature, the mass concentration and thickness of the ash decreased. When the temperature exceeds 750 K, soot begins to regenerate. Among the exhaust parameters, the mass flow rate of the exhaust has the greatest influence on the soot distribution. The length–diameter ratio, the ratio of the inlet and the outlet channel, and channel density have little effect on the mass concentration of soot, and the soot mass concentration increases with the increase in channel density. In addition to the length–diameter ratio of 2.1, the soot thickness increases with the increase in the length–diameter ratio, and the rising rate is also accelerated. The thickness of soot decreased with the increase in channel density and the ratio of the inlet and the outlet channels. When the channel density is more than 250, the change in soot thickness is basically the same. When the ratio of the inlet and the outlet channels exceeds 1.3, the change in the soot thickness is basically the same. Among the structural parameters, channel density has the greatest influence on the soot distribution.

Fast Diesel Aftertreatment Heat-Up Using CDA and an Electrical Heater Between 1.2 and 5.0 kW

Commercial vehicles require fast aftertreatment heat-up in order to move the selective catalytic reduction catalyst into the most efficient temperature range to meet upcoming NOX regulations while minimizing CO2. This study is a follow-up study using an electric heater upstream of a LO-SCR followed by a primary aftertreatment system having an engine equipped with cylinder deactivation. The focus of this study is to minimize the maximum power input to the e-heater without compromising tailpipe NOX and CO2. A system solution is demonstrated using a heavy-duty diesel engine with an end-of-life aged aftertreatment system targeted for 2027 emission levels using various levels of controls. The baseline layer of controls includes cylinder deactivation to raise the exhaust temperature more than 100°C in combination with elevated idle speed to increase the exhaust mass flow rate through the aftertreatment system. The engine load is adjusted to compensate for generating electrical power on the engine. The combination of electrical heat, added load, cylinder deactivation, and elevated idle speed allows the aftertreatment system to heat up in a small fraction of the time required by today’s systems. This work was quantified over the cold federal test procedure, hot FTP, low load cycle (LLC), and the U.S. beverage cycle showing improved NOX and CO2 emissions. The improvement in NOX reduction and the CO2 savings over these cycles are highlighted.

Assessment of an Exhaust Thermoelectric Generator Incorporating Thermal Control Applied to a Heavy Duty Vehicle

The road transport industry faces the need to develop its fleet for lower energy consumption, pollutants and CO2 emissions. Waste heat recovery systems with Thermoelectric Generators (TEGs) can directly convert the exhaust heat into electric energy, aiding the electrical needs of the vehicle, thus reducing its dependency on fuel energy. The present work assesses the optimisation and evaluation of a temperature-controlled thermoelectric generator (TCTG) concept to be used in a commercial heavy-duty vehicle (HDV). The system consists of a heat exchanger with wavy fins (WFs) embedded in an aluminium matrix along with vapour chambers (VCs), machined directly into the matrix, that grant the thermal control based on the spreading of local excess heat by phase change, as proposed by the authors in previous publications and patents. The TCTG concept behaviour was analysed under realistic driving conditions. An HDV with a 16 L Diesel engine was simulated in AVL Cruise to obtain the exhaust gas temperature and mass flow rate for each point of two cycle runs. A model proposed in previous publications was adapted to the new fin geometry and vapour chamber configuration and used the AVL Cruise data as input. It was possible to predict the thermal and thermoelectric performance of the TCTG along the corresponding driving cycles. The developed system proved to have a good capacity for applications with highly variable thermal loads since it was able to uncouple the maximisation of heat absorption from the regulation of the thermal level at the hot face of the TEG modules, avoiding both thermal dilution and overheating. This was achieved by the controlled phase change temperature of the heat spreader, that would ensure the spreading of the excess heat from overheated to underheated areas of the generator instead of wasting excess heat. A maximum average electrical production of 2.4 kW was predicted, which resulted in fuel savings of about 2% and CO2 emissions reduction of around 37 g/km.

Multilayer Conductive Metallization With Offset Vias Using Aerosol Jet Technology

Abstract The transition of additive printed electronics into high-volume production requires process consistency to allow quality control of the manufactured product. Process recipes are needed for multilayer substrates with z-axis interconnects in order to enable complex systems. In this paper, process recipes have been developed through fundamental studies of the interactions between the process parameters and the mechanical–electrical performance achieved for multilayer substrates. The study reported in this paper focuses on printed vias also known as donut vias. Aerosol jet process parameters studied include carrier mass flow rate, sheath mass flow rate, exhaust mass flow rate, print speed, number of passes, sintering time and temperature, UV-intensity for UV-cure, and standoff height. The electrical performance has been quantified through the measurements of resistance. The mechanical performance has been quantified through measurement of shear load-to-failure. The effect of sequential build-up on the mechanical–electrical properties vs process parameters has been quantified for up to eight-layers designs. The performance of five-layer and eight-layer additively printed substrate designs and effect of multiple vias has been compared to assess process consistency.

Weighted analysis and simplified calculation method of automotive exhaust thermoelectric generator performance

This paper focuses on evaluating the performance of automotive exhaust thermoelectric generators (AETEGs) under actual vehicle driving conditions. The exhaust gas temperature and mass flow rate under driving conditions are in a transient state, which directly affects the performance of the AETEG and therefore cannot be ignored. To reflect this, we built a numerical model of the AETEG and developed a weighted analysis method based on the exhaust conditions in standard test cycles to obtain the output performance and optimal thermoelectric module area of the AETEG. The results show that, compared with the results without using the weighted analysis, the maximum power output and the optimal module area increased by 5.2 % and 56.4 %, respectively, after using this method. In addition, for engineering applications, this paper presents a simplified calculation method for the performance parameters of an AETEG. Compared with the numerical calculation method, the simplified calculation method, whose calculation accuracy meets the requirements of general engineering applications, is more convenient and efficient, and has certain guiding significance for the practical application of AETEGs.