Browse Topic: Waste heat recovery

Items (303)

A Calculation Methodology for Predicting Exhaust Mass Flows and Exhaust Temperature Profiles for Heavy-Duty Vehicles

7/20/2020

The predictive control of commercial vehicle energy management systems, such as vehicle thermal management or waste heat recovery (WHR) systems, are discussed on the basis of information sources from the field of environment recognition and in combination with the determination of the vehicle system condition. In this article, a mathematical method for predicting the exhaust gas mass flow and the exhaust gas temperature is presented based on driving data of a heavy-duty vehicle. The prediction refers to the conditions of the exhaust gas at the inlet of the exhaust gas recirculation (EGR) cooler and at the outlet of the exhaust gas aftertreatment system (EAT). The heavy-duty vehicle was operated on the motorway to investigate the characteristic operational profile. In addition to the use of road gradient profile data, an evaluation of the continuously recorded distance signal, which represents the distance between the test vehicle and the road user ahead, is included in the prediction model. Using a Fourier analysis, the trajectory of the vehicle speed is determined for a defined prediction horizon. To verify the method, a holistic simulation model consisting of several hierarchically structured submodels has been developed. A map-based submodel of a combustion engine is used to determine the EGR and EAT exhaust gas mass flows and exhaust gas temperature profiles. All simulation results are validated on the basis of the recorded vehicle and environmental data. Deviations from the predicted values are analyzed and discussed.

Kreyer, Jörg, Müller, Marvin, Esch, Thomas

An Analytical Approach for Calculating Instantaneous Multilayer-Coated Wall Surface Temperature in an Engine

2020-01-01604/14/2020

Thermal swing coatings that have low volumetric heat capacity and low thermal conductivity are attractive because they have the potential to significantly reduce heat transfer to the combustion chamber walls. This paper presents an analytical method for determining the exact solution of the time-resolved wall temperature during the engine cycle for any number of coating layers and properties using the Laplace transformed heat diffusion equation. The method relies only on material properties and the past heat flux history, and represents the exact solution of the heat diffusion equation. The analytical nature of the solution enables fast computation and, therefore, application to system-level optimization calculations. The model relies on an assumption of one-dimensional heat flow, and constant material properties. The major advantage of this approach compared to the standard finite difference approach, wherein the wall is finely discretized, is that there is no approximation and the accuracy is guaranteed, i.e., it does not depend on nodal density. Results are presented for both a quasi-steady operating condition and for an engine transient event. In the latter case a 200-fold reduction in computation time relative to a finite difference code was realized.

Koutsakis, G., Ghandhi, J.B.

Optical Diagnostics of Isooctane and n-Heptane Isobaric Combustion

2020-01-11264/14/2020

Isobaric combustion has demonstrated a great potential to reach high thermodynamic efficiency in the advanced Double Compression Expansion Engine (DCEE) concept. It appears as one of few viable choices for applications with high-pressure combustion. At these conditions, releasing heat at a constant pressure minimizes the peak in-cylinder pressure and, hence, mitigates excessive mechanical stress on the engine. This study focuses on the effect of fuels on the multiple-injection isobaric combustion. A single-cylinder heavy-duty engine was utilized to test and compare the isobaric combustion with pure isooctane and n-heptane fuels. The engine was equipped with an optical piston to allow a bottom-view of the combustion chamber. The interactions of multiple injections and the combustion behavior were studied using high-speed acquisition of chemiluminescence. The examined isobaric cases have a peak pressure of 70 bar. For cases with high soot luminosity, a short band-pass filter was used to avoid image saturation. Fuels with short ignition delay time such as n-heptane are usually used for isobaric applications as they offer good controllability of injections. However, the study herein demonstrates that isobaric combustion can be achieved even with high octane number fuels such as isooctane. The dwell time between injections is much larger for isooctane, which allows enhanced mixing of the fuel jets with air and thus a partially premixed combustion behavior. The high-speed imaging demonstrated evidence of flame extinguishing during the sequential injection of n-heptane. This contributes to the staging of the heat release rate.

Al Ramadan, Abdullah S., Nyrenstedt, Gustav, Ben Houidi, Moez, Johansson, Bengt

Performance Evaluation of a Heavy-Duty Diesel Truck Retrofitted with Waste Heat Recovery and Hybrid Electric Systems

08-09-01-00043/11/2020

The interest of long-hauling companies about the conversion of their fleets into low-emission and fuel-efficient vehicles is growing, and retrofitting options may represent a suitable solution. Powertrain hybridization and waste heat recovery are considered among the most promising methods to further improve the fuel economy of road vehicles powered by internal combustion engines. In this article, not only the effect of retrofitting a heavy-duty truck with an electrification-oriented ORC unit or with a series hybrid system is investigated, but also the possibility of implementing both at the same time. The conventional vehicle is powered by a heavy-duty 12.6 liters diesel engine. It is shown that, despite such a large engine has high potential for waste heat recovery, on the other hand it represents a very challenging constraint when designing a hybrid retrofitting. Four powertrain options are considered: conventional vehicle (engine-only powered), waste heat recovery retrofit, hybrid retrofit, waste heat recovery+hybrid retrofit. For the hybrid powertrains, the optimal control strategy is analyzed and used as a starting point to develop an online implementable rule-based control strategy. The performance of the different powertrains have been numerically simulated over a set of driving cycles. The results show that, compared to the conventional powertrain, the hybrid retrofit allows the greatest reduction in fuel consumption (up to 17%), and the best employment of the waste heat recovery system.

Villani, Manfredi, Lombardi, Simone, Tribioli, Laura

Waste Heat Recovery System Thermal Management

J3173_202002 (Current)2/24/2020

Waste heat recovery (WHR) systems are used in vehicles and machines powered by internal combustion (IC) engines to capture unused/waste heat and utilize it thereby reducing fuel consumption and emissions by improving efficiency. This information report is a survey of the waste heat recovery methods that include the use of heat exchangers.

Cooling Systems Standards Committee

Enhancing Peak Firing Pressure Limit for Achieving Better Brake Thermal Efficiency of a Diesel Engine

2019-01-218012/19/2019

An increased cycle expansion ratio is beneficial from a thermodynamic viewpoint to increase the engine efficiency. In this study, the target compression ratio and corresponding thermodynamic cycle layout were investigated by means of a new ideal combustion cycle. To model the experimental pressure traces, the combustion was divided into three parts; constant volume combustion, early expansion combustion and late combustion. This study discussed optimal parameter values for compression ignition combustion under PFP constraints. These parameters included compression ratio, pressure ratios as well as cut-off ratios. Furthermore, this study experimentally investigated the limitation of thermal efficiency and the variation of energy losses under different geometric compression ratios, boosting pressure and degree of constant volume combustion. These experiments utilized a supercharged single-cylinder heavy duty diesel engine with PFP-capability of up to 30 MPa. In conclusion, it is confirmed that improvement in the indicated thermal efficiency and BTE was achieved by increasing the compression ratio. The trade-off between increased compression ratio and higher losses was also established and an optimum compression ratio found.

Enya, Kenji, Uchida, Noboru

Performance Analysis of Volumetric Expanders in Heavy-Duty Truck Waste Heat Recovery

2019-01-226612/19/2019

With increasing demands to reduce fuel consumption and CO2 emissions, it is necessary to recover waste heat from modern Heavy Duty (HD) truck engines. Organic Rankine Cycle (ORC) has been acknowledged as one of the most effective systems for Waste Heat Recovery (WHR) due to its simplicity, reliability and improved overall efficiency. The expander and working fluid used in ORC WHR greatly impact the overall performance of an integrated engine and WHR system. This paper presents the effects of volumetric expanders on the ORC WHR system of a long haulage HD truck engine at a steady-state engine operating point chosen from a real-time road data. Performance of a long haulage HD truck engine is analyzed, based on the choice of three volumetric expanders for its WHR system, using their actual performance values. The expanders are: an oil-free open-drive scroll, a hermetic scroll and an axial piston expander with working fluids R123, R245fa and ethanol, respectively. Performance of the engine that accommodates the WHR system, with each expander and working fluid combination, is assessed based on the overall system efficiency that can be achieved through heat recovery from the engine exhaust. This simulation study is carried out using validated 0D models of the scroll expanders and performance data of the piston expander, adopted from literature, and a 1D system model of a long haulage HD truck engine encompassing a WHR system. Under the given conditions, the open-drive scroll expander (R123) leads to a higher system efficiency of 6.3% at an optimum expander speed of 3400 rpm with an estimated fuel saving of 3.6% in the vehicle under study. The hermetic scroll expander (R245fa) exhibits potential performance at higher rotational speeds; it leads to 5.4% system efficiency at 5000 rpm and 3% fuel-saving. The axial piston expander (ethanol) results in a consistent performance over a wide range of expander speeds. The effect of sizing a volumetric expander in improving the overall system efficiency is also investigated. This study provides insights on the suitability of volumetric expanders in HD truck WHR.

Thantla, Sandhya, Fridh, Jens, Erlandsson, Anders Christiansen, Aspfors, Jonas

Simulation Study on Driving Range at High and Low Temperature

2019-01-507111/4/2019

Yu, Jiang, Nie, YanXin, MingJun, Dong, Xie, Ning, Ma, BaoTong, Xu, Zhe

A Study and Mathematical Analysis of Thermionic Energy Conversion Materials Based on Their Solid State Emission Properties

2019-28-008410/11/2019

The physical mechanism of direct energy conversion technology for space applications is well known for over a century. Whereas thermionic energy conversion is now being explored for automotive regeneration applications considering its high conversion efficiency. The thermionic emission used in space applications has operating temperatures >20000C which is much higher than available temperature at terrestrial automotive applications. Hence the key research interests are focused towards effective utilization of thermionic energy conversion for automotive waste heat recovery at considerably lower temperatures i.e. <10000C. This strongly needs a selection of suitable materials in thermionic convertor. This work shows a comprehensive study on materials and their work function for thermionic emission at relatively lower temperature. The selection of different emitter materials is based on simulation applying Richardson Dushman equation and child’s law at operating temperature ranges. The paper concludes with a comparative analysis of high and low work function materials showing their behavior of thermionic emission at specified temperature.

Kodihal, Kantaprasad, Sagar, Ankur

How to Improve SI Engine Performances by Means of Supercritical Water Injection

2019-24-023510/7/2019

The efficiency of ICEs is strongly affected by exhaust gases and engine cooling system heat losses, which account for about 50% of the heat released by combustion. A promising approach is to transfer this exhaust heat to a fluid, like water, and inject it into the combustion chamber under supercritical conditions. In such a way, the recovered energy is partially converted into mechanical work, improving both engine efficiency and performance. A quasi-dimensional model has been implemented to simulate an SI engine with supercritical water injection. Specifically, a spark ignition ICE, four-stroke with Port Fuel Injection (PFI) has been considered. The model accounts for gas species properties, includes valves opening/closing, wall heat transfer, a water injection model and a combustion model. The influence of some injection parameters, i.e. Water/Fuel ratio (W/F), Start Of water Injection (SOI) and Water Injection Duration (WID), on engine performances and efficiency is discussed in details. The results show that an increase of W/F ratio has the strongest impact on the performances with respect to SOI and WID, i.e. higher W/F ratio, SOI closer to TDC and shorter WID provide a higher engine performance. For instance, with W/F ratio equal to 7 and water injected at 230 bar and 700 K, an increase of engine efficiency up to 11.5% is obtained. The parametric analysis is performed by injecting water when the chemical heat release is complete, in order to avoid the interaction between injected water and combustion. Finally, the effects of spark advance on water injection efficiency gain have been investigated. By advancing the spark timing the combustion heat release is advanced, hence the supercritical water can be injected earlier. This leads to an increase of efficiency gain with earlier SOI.

Cantiani, Antonio, Viggiano, Annarita, Magi, Vinicio

A Mild Hybrid SIDI Turbo Passenger Car Engine with Organic Rankine Cycle Waste Heat Recovery

2019-24-01949/9/2019

While striving for more fuel-efficient vehicles, all possible measures are considered to increase the efficiency of the combustion engine powertrain. 48V mild hybrid technology is one such measure, SIDI (Spark Ignited Direct Injection) engines with Miller technology are another, while recovering energy from the engine’s waste heat (WHR) is yet another option. In this paper, results will be published from an advanced engineering project at Volvo Cars including all of these components. An ethanol based Organic Rankine Cycle (ORC) WHR-system was successfully built around a 4-cylinder, 2.0 litre SIDI-engine, including 48V mild hybrid technology, with vehicle packaging considered. A dedicated control system was also developed for the ORC system including communication between it and the engine. The ORC system uses the engine exhaust as the heat source, for which a purpose-built evaporator was designed and built to fit in the vehicle tunnel. The expansion of the ethanol vapour occurs in an axial piston expander coupled both electrically to the hybrid system and mechanically to the engine crankshaft via a belt-drive. This dual power output from the expander was found to be of particular importance for a passenger car with a transient driving style, giving the opportunity to recover more waste heat energy by overcoming the slow response from the steam system with the fast response of the electrical hybrid system. Initial results on the engine bench indicate, at high engine loads, a decrease in brake specific fuel consumption of 5-7% with stoichiometric engine operation. These results are in-line with our simulations also show that the combined powertrain system gives advantages in both city (mild hybrid), rural (optimized engine, WHR) and highway conditions (WHR).

Ekström, Fredrik B., Rolandson, Ola, Eriksson, Soren, Odenmarck, Christer, Svensson, Mattias, Eriksson, Andreas, Olsen, Hans

Surface Treatment Could Improve Refrigeration Efficiency

TBMG-351319/1/2019

Unlike water, liquid refrigerants and other fluids that have a low surface tension spread quickly into a sheet when they come into contact with a surface. For many industrial processes, it would be better if the fluids formed droplets that could roll or fall off the surface and carry heat away with them.

Generating Electrical Power from Waste Heat

TBMG-346116/1/2019

Directly converting electrical power to heat is easy; however, converting heat into electrical power is not as easy. To address this issue, a tiny silicon-based device was developed that can harness what was previously called waste heat and turn it into DC power. The device could be used as a compact infrared power supply that could replace radioisotope thermoelectric generators (RTGs) that are used for such tasks as powering sensors for space missions that don’t get enough direct sunlight to power solar panels. The device is made of common and abundant materials such as aluminum, silicon, and silicon dioxide — or glass — combined in uncommon ways.

Experimental Study of a Heat-Pipe Exchanger for an Exhaust Heat Recovery System

2019-01-01514/2/2019

Currently, the heat recovery systems based on thermoelectrics are an important part of the technologies under study to improve the efficiency of vehicles with internal combustion engines. Different types of heat exchangers are used as part of the components for the operation of the heat recovery technologies. Among the heat exchangers, the heat pipes are studied due to their promising results. This work presents the experimental analysis of a heat exchanger prototype based in heat pipes. The prototype was custom designed for a given thermoelectric module. The design was performed seeking to maximize its efficiency while protecting the module by avoiding possible excesses of temperature during the operation. The requirements for the heat pipe design were defined from the experimental characterization of the thermoelectric module. The prototype was manufactured through a sintering process. The system was tested in the laboratory first by components, and then as a system. The results allow observing the potential of the use of heat pipes as part of heat recovery technologies. The design tested allowed guaranteeing an operating temperature range with an upper limit that protects the thermoelectric module to increase its durability under variable operating conditions.

Rincon, Ernesto, Munoz, Luis

Analysis of the Effect of Vehicle Platooning on the Optimal Control of a Heavy Duty Engine Thermal System

2019-01-12594/2/2019

One promising method for reducing fuel consumption and emissions, particularly in heavy duty trucks, is platooning. As the distance between vehicles decreases, the following vehicles will experience less aerodynamic drag on the front of the vehicle. However, reducing the velocity of the air contacting the front of the vehicle could have adverse effects on the temperature of the engine. To compensate for this effect, the energy consumption of the engine cooling system might increase, ultimately limiting the overall improvements obtained with platooning. Understanding the coupling between drag reduction and engine cooling load requirement is key for successfully implementing platooning strategies. Additionally, in a Connected and Automated Vehicle (CAV) environment, where information of the future engine load becomes available, the operation of the cooling system can be optimized in order to achieve the maximum fuel consumption reduction. In this paper, a control-oriented physics-based model for the engine cooling loop of a Volvo engine is developed and validated against road data. Starting from the validated model, an optimal control problem for the coolant system is formulated considering the tradeoff between the tracking of the engine temperature setpoint and the corresponding fuel consumption under different trailing distances. To compare the coolant system performance, Dynamic Programming (DP) is used to determine the global optimal solution for the coolant system actuator. The coupling between optimal cooling system operation and reduction in ram air are evaluated by comparing the results obtained from the DP under different platooning conditions against the unrestricted scenario. In addition, the paper analyzes the changes in the tradeoff between fuel consumption and setpoint tracking for different vehicle distances. This analysis will provide useful insight on the sensitivity of the coolant system controller calibration to the platoon distance.

Block, Brian, Huynh, Brian, Boyle, Stephen, Stockar, Stephanie, Geyer, Stephen, Li, Jian, Huber, Jeffrey

Automotive Waste Heat Recovery after Engine Shutoff in Parking Lots

2019-01-01574/2/2019

1 The efficiency of internal combustion engines remains a research challenge given the mechanical friction and thermodynamic losses. Although incremental engine design changes continue to emerge, the harvesting of waste heat represents an immediate opportunity to address improved energy utilization. An external mobile thermal recovery system for gasoline and diesel engines is proposed for use in parking lots based on phase change material cartridges. Heat is extracted via a retrofitted conduction plate beneath the engine block after engine shutoff. An autonomous robot attaches the cartridge to the plate and transfers the heat from the block to the Phase Change Material (PCM) and returns later to retrieve the packet. These reusable cartridges are then driven to a Heat Extraction and Recycling Tower (HEART) facility where a heat exchanger harvests the thermal energy stored in the cartridges. A series of mathematical models are created to estimate the recoverable heat from a standard parking lot configuration. A representative case study that considered 500 cars with periodic traffic flow over a period of 16 hours can heat approximately 25 kiloliters of potable water from 15°C to 50°C. Future development will involve the creation of strategies to extract heat during engine idling at traffic stops and drive through lanes.

Syed, Zaker, Wagner, John R.

Review of Vehicle Engine Efficiency and Emissions

2019-01-03144/2/2019

This review paper covers major regulatory and technology developments in 2018 pertinent to tailpipe emissions of greenhouse gases and criteria pollutants. Europe has proposed ambitious reductions in CO2 limits for both light- and heavy-duty sectors. The challenge is compounded with changing measurement norms and a significant shift away from fuel efficient diesels in the light-duty (LD) space. Both incremental and step changes are being made to advance internal combustion. New studies show that in-use NOx emissions from diesels can be much lower than required by the Euro 6 regulation. Discussions have already started on Euro 7 regulations, and the leading regulatory concepts and proposed technical solutions are provided. In the heavy-duty (HD) sector, the progress is outlined in improving engine and vehicle fuel efficiency through the US Department of Energy’s (DOE’s) SuperTruck II program and other representative studies. Common approaches among the participants include hybridization, waste heat recovery, and both open- and closed cycle incremental improvements. Emissions control focus is on evaluating pathways to achieve California’s contemplated low-NOx standards, recently also supported by the US EPA through the Cleaner Trucks Initiative. The challenge is to reduce cold start and low load emissions, requiring innovative engine and after-treatment system solutions. Leading concepts include close-coupled SCR (selective catalytic reduction), use of passive NOx adsorbers, integration of SCR (selective catalytic reduction) on DPFs (diesel particulate filters), low temperature urea or ammonia injection, dual SCR, and active and passive thermal management to raise exhaust temperatures. Work is also underway on a new low load certification cycle. Continued advancement is made on after-treatment components. Aged three-way catalysts (TWCs) and diesel oxidation catalysts (DOCs) are nearing 90% conversion at 150 °C. SCR catalysts continue to improve both their low temperature conversion as well as high temperature durability. Particulate regulations in Europe, China and India are leading to widespread adoption of gasoline particulate filters (GPFs). Lean burn gasoline engines can offer significant fuel economy benefits. NOx control is a challenge, and passive SCR systems and new catalysts are proposed.

Joshi, Ameya

Study of Thermoacoustic Engine for Automotive Exhaust Waste Heat Recovery

2019-01-12574/2/2019

In this paper, the travelling-wave thermoacoustic engine (TAE) and its application for recovery of waste heat from automotive exhaust systems is investigated. The aim is to give some insight into the potential, but also limitations of the technique for practical applications. This includes packaging, physical boundary conditions as heating and cooling available, but also system perspectives as influence of legislative drive cycles and degree of hybridization. First, the travelling-wave TAE is described as a low-order acoustic network in the frequency domain. Models, including non-linear effects, are set up for every component in the network to describe the propagation and dissipation of acoustic waves. For a TAE with looped structure, the continuity of pressure and volumetric velocity is employed to determine the saturation pressure, as well as the stable operating point. These models are validated against experimental data available in the literature [1]. This is an engine designed for high-temperature application, but is well documented and yields a good reference for the models and to further the understanding of the TAE. Next, an optimized design for a system to be adapted to the operating conditions typical for heavy-duty systems is studied and proposed. No actual physical prototype has been built and verified, but the design is based on, and is of the same efficiency, as machines that have been reported in the literature. The proposed design and the original TAE are then used to discuss the practical implementation for heavy- and light-duty vehicles on a system level. To improve the utilization of the available exhaust waste heat, a configuration of system heat exchangers combining a self-circulating loop with multiple TAE modules is preliminarily studied. Further research for this configuration is needed for practical implementation although current simulation results are encouraging.

Zhou, Jianhua, Karlsson, Mikael, Abom, Mats

A Test Rig for Evaluating Thermal Cyclic Life and Effectiveness of Thermal Barrier Coatings inside Exhaust Manifolds

2019-01-09294/2/2019

Thermal Barrier Coatings (TBCs) may be used on the inner surfaces of exhaust manifolds in heavy-duty diesel engines to improve the fuel efficiency and prolong the life of the component. The coatings need to have a long thermal cyclic life and also be able to reduce the temperature in the substrate material. A lower temperature of the substrate material reduces the oxidation rate and has a positive influence on the thermo-mechanical fatigue life. A test rig for evaluating these properties for several different coatings simultaneously in the correct environment was developed and tested for two different TBCs and one oxidation-resistant coating. Exhausts were redirected from a diesel engine and led through a series of coated pipes. These pipes were thermally cycled by alternating the temperature of the exhausts. Initial damage in the form of cracks within the top coats of the TBCs was found after cycling 150 times between 50°C and 530°C. Temperature calculations showed that, besides evaluating the thermal cyclic life, the test method has the potential to provide a quick ranking of coating materials with respect to thermal insulation by measuring the temperature on the outer surface of the coated pipes. One of the major advantages of the presented test method compared to other methods described in the literature is that it ranks the thermal cyclic life and thermal properties of different coatings under realistic conditions in the correct environment. More cycles and higher temperatures are recommended for future tests, to accelerate the test, as well as evaluate whether the initial cracks in the TBCs will lead to spallation.

Thibblin, Anders, Olofsson, Ulf

Fuel and Engine Effects on Rich-Combustion Products as an Enabler of In-Cylinder Reforming

2019-01-11444/2/2019

Onboard reforming has been proposed as a strategy for improving spark-ignited (SI) engine efficiency through knock reduction, dilution limit extension, improved thermodynamic gas properties, and thermochemical exhaust enthalpy recuperation. One approach to onboard fuel reforming is to combust fuel in the engine cylinder under rich conditions, producing a hydrogen-rich reformate gas--which can subsequently be recirculated into the engine. Hydrogen is the preferred product in this process due to its high flame speed and knock resistance, compared with other reformate constituents. In this work, the effects of engine operation, fuel composition and water injection were evaluated for their effect on reformate gas composition produced under rich combustion conditions. Engine parameters, including intake pressure, intake temperature, combustion phasing, and valve timing all had no significant impact on hydrogen yield at a given equivalence ratio. Fuel effects on hydrogen yield were more significant--with methanol producing 75% more hydrogen than toluene at the same equivalence ratio. The greater hydrogen yield was due to greater hydrogen content of the fuel, although the benefit was shown to be partially offset by lower hydrogen selectivity and conversion. Production of smoke limited the minimum relative air-fuel ratio of some fuels contributing to reduced hydrogen yields. Upstream water injection was shown to boost hydrogen production by 10-60% (rel.) at the expense of carbon monoxide due to steam reforming reactions and Le Chatlier’s principle in the water gas shift reaction. Toluene exhibited the greatest relative improvement in hydrogen yield due to the lower exhaust water concentrations in the absence of water injection. In the presence of water injection, hydrogen production in some cases exceeded fuel hydrogen content indicating the presence of water gas shift and steam reforming chemistry occurring. Using the speciated exhaust data, a correlation was developed using measured exhaust hydrogen content to predict hydrogen concentration from carbon monoxide and relative air-fuel ratio. The correlation developed improves upon previous correlations by explicitly including the hydrogen content of the fuel, and thus allowing more accurate prediction. Lastly, the energy balance was calculated under rich combustion conditions from the indicated power and chemical potential energy of the reformate. The energy balance analysis suggests that in-cylinder reforming is a net endothermic process, with some exhaust heat being converted into chemical potential energy. Overall, it was concluded that in-cylinder reforming can be used to produce practical quantities of reformate to improve SI engine performance. This work showed the potential for optimized fuels to improve in-cylinder reforming processes, in conjunction with water injection, to produce a hydrogen-rich reformate gas without parasitic losses.

Voice, Alexander K., Costanzo, Vincent

Automated 6DOF Model Generation and Actuator Sizing within AFSIM

2019-01-13363/19/2019

The Air Force Research Laboratory has interest in automatically generating the extensive aerodynamic databases essential for six degree of freedom (6DOF) models and the use of 6DOF models for design. To be most useful, automation must include all aspects of producing the database including meshing, control surface deflections, running the CFD solution, and storage of the results. This effort applies newly-developed software to produce the desired results. Firstly, AFRL software called Computational Aircraft Prototype Syntheses (CAPS) allows automated meshing using the Advancing Front Local Reconnection (AFLR) software from Mississippi State University1 and automated control surface deflection using Engineering Sketch Pad (ESP) software from MIT/Syracuse. CAPS includes the ability to run the NASA CFD code FUN3D and interpret the FUN3D results via an Application Interface Module (AIM). This may sound like a complicated process. However, it is quite simple using a python interface to CAPS called pyCAPS. The automated generation of the aerodynamic database for the 6DOF model is handled by use of a short python script that includes nested loops that handle the numerous CFD runs to capture the combinations of angle-of-attack, sideslip angle, and control surface deflections needed for the database. This database is then paired with an appropriate controller and other information, like propulsion data and mass property data, to form the complete 6DOF model. Of interest is the design of actuators that are attached to the aircraft control surfaces. The 6DOF model is then used to fly the aircraft through an Operational Analysis (OA) scenario in AFSIM (Advanced Framework for Simulation, Integration and Modeling) where maneuvers and environmental conditions like gusts or turbulence are simulated. The entire process is shown to be tractable and accessible.

Allison, Darcy, Shimmin, Kyle, Schley, William, Bryson, Dean

Fuel Cell/Fuel Cell Hybrid System

TBMG-339333/1/2019

Fuel cells can deliver clean, reliable, and uninterrupted power nearly 100 percent of the time. Fuel cells offer the advantage of efficiency by converting chemical energy directly to electricity. They have no moving parts, thereby eliminating failures associated with pumps, blowers, heat exchangers, and other systems. All fuel cells, particularly high-temperature fuel cells, require spent fuel/waste heat recovery subsystems, and low-temperature fuel cells require fuel reforming subsystems that lower the efficiency of the entire system.

Q&A

19TOFHP02_132/1/2019

In October 2018, Tenneco Inc. completed its “transformational” acquisition of Federal-Mogul LLC, and now is working to realign the businesses and establish two independent companies by late 2019: an Aftermarket and Ride Performance company, and a Powertrain Technology company that will continue to address fuel economy, power output, and criteria pollution requirements for gasoline, diesel and hybrid-electric powertrains across the various regions of the world. The Tenneco name will remain with the Powertrain, or Clean Air, side of the business, according to John Wehrenberg, the leader of the Commercial Truck Off-Highway (CTOH) business for Clean Air. “The most exciting space in truck and off-highway, at the moment, is in the Asian markets, driven by the regulatory changes that are coming less than 18 months from now” with Bharat VI in India and China VI, he said during an interview with Truck & Off-Highway Engineering this past fall. Wehrenberg and Bernd Scherer, Tenneco's Executive Director of Engineering, offered their viewpoints on these markets and other topics. What approach is Tenneco taking to upcoming emissions standards in India and China?

Gehm, Ryan

A Heuristic Supervisory Controller for a 48V Hybrid Electric Vehicle Considering Fuel Economy and Battery Aging

2019-01-00791/15/2019

Most studies on supervisory controllers of hybrid electric vehicles consider only fuel economy in the objective function. Taking into consideration the importance of the energy storage system health and its impact on the vehicle’s functionality, cost, and warranty, recent studies have included battery degradation as the second objective function by proposing different energy management strategies and battery life estimation methods. In this paper, a rule-based supervisory controller is proposed that splits the torque demand based not only on fuel consumption, but also on the battery capacity fade using the concept of severity factor. For this aim, the severity factor is calculated at each time step of a driving cycle using a look-up table with three different inputs including c-rate, working temperature, and state of charge of the battery. The capacity loss of the battery is then calculated using a semi-empirical capacity fade model. Eventually, the fuel economy, and capacity loss as two of the most important objectives are compared with and without implementing the proposed controller. In the comparative study, four customized driving cycles are considered, including calm/aggressive drivers and low/high vehicle speeds. The results suggest improvement in the objectives and trade-off between fuel economy and battery aging. The proposed heuristic controller can be implemented in different types of hybrid electric vehicles.

Malmir, Farzam, Xu, Bin, Filipi, Zoran

Q&A: Dr. Patrick Hopkins, Professor, University of Virginia, Charlottesville

TBMG-3323311/1/2018

Professor Hopkins and University of Virginia colleagues — in collaboration with materials scientists at Penn State, the University of Maryland, and the National Institute of Standards and Technology — have studied a material that can dynamically regulate its thermal properties, switching back and forth between insulating and cooling based on the amount of water that is present.

Experimental Investigation of Ethanol-Diesel-Butanol Blends in a Compression Ignition Engine by Modifying the Operating Parameters

03-11-05-003710/31/2018

The rapid utilization of fossil fuels has triggered the finding of alternative renewable fuel that replaces or reduces the consumption by alternative fuels for fueling compression ignition (CI) engines. One such renewable fuel is ethanol which can be manufactured from biomass. The present study details the utilization of an optimum amount of ethanol in CI engine by modifying the operating parameters. It was already published in the previous paper that 45% ethanol can be utilized along with diesel using 10% butanol as cosolvent. This fuel is also meeting the minimum requirement with respect to properties as per ASTM standards. This experimental study was performed to investigate the influence of modifying the engine operating parameters on the performance, combustion, and emission parameters fueled with the blend containing 45% ethanol under various load conditions. Taguchi method was used to find out the optimal parameters such as injection timing (IT), injection pressure (IP), compression ratio (CR), and intake air temperature (IAT) by deploying L9 orthogonal array. Testing has been conducted with and without modifying the engine operating parameters, and the results were compared with that of diesel. The test results showed that there was an improvement in the performance and emission parameters of diesel-ethanol-butanol blends fueled with modified engine parameters, namely, IP, 190 bar; IT, 29° before top dead center (BTDC); CR, 19:1; and IAT, 100°C, compared to normal operating parameters when fueled in CI engine. This experiment reduced 55% of diesel consumption and significant reduction in emissions compared to diesel. This experiment ensures better utilization of ethanol in diesel engine, thereby reducing the consumption of diesel (fossil fuel).

Prabakaran, B., Vijayabalan, Palanimuthu, Balachandar, M.

A Simulation Study of Optimal Integration of a Rankine Cycle Based Waste Heat Recovery System into the Cooling System of a Long-Haul Heavy Duty Truck

2018-01-17799/10/2018

As a promising solution to improve fuel efficiency of a long-haul heavy duty truck with diesel engine, organic Rankine cycle (ORC) based waste heat recovery system (WHR) by utilizing the exhaust gas from internal combustion engine has continuously drawn attention from automobile industry in recent years. The most attractive concept of ORC-based WHR system is the conversion of the thermal energy of exhaust gas recirculation (EGR) and exhaust gas from Tailpipe (EGT) to kinetic energy which is provided to the engine crankshaft. Due to a shift of the operating point of the engine by applying WHR system, the efficiency of the overall system increases and the fuel consumption reduces respectively. However, the integration of WHR system in truck is challenging by using engine cooling system as heat sink for Rankine cycle. The coolant mass flow rate influences strongly on the exhaust gas bypass which ensures a defined subcooling after condenser to avoid cavitation of pump. The coolant temperature decides the condensation pressure which impacts on the efficiency of WHR system. This paper aims to investigate the impacts of cooling conditions on WHR system by simulation. An optimal integration position of WHR condenser has been found. A complex 0D/1D-simulation model for a turbocharged production heavy duty engine with low-/high-temperature cooling circuits and a WHR system with ethanol as working fluid have been established in a conventional 1D-simulation software. A comparison between two WHR system layouts is made to determine WHR system concepts. An optimization for thermal management of the engine has been conducted to evaluate the maximal recovered energy in consideration of cooling fan engagement, thermostat operation and interactions between subsystems under transient conditions.

Yang, Kangyi, Grill, Michael, Bargende, Michael

Exhaust Energy Recovery with Variable Geometry Turbine to Reduce Fuel Consumption for Microcars

2018-01-18259/10/2018

The objective proposed by EU to reduce by about 4%/year CO2 emission of internal combustion engines for the next years up to 2030, requires to increase the engine efficiency and accordingly improving the technology. In this framework, hybrid powertrains can have the possibility of a deep market penetration since they may recover energy during brake, allow the engine to operate in better efficiency conditions and with less transients, Moreover, they can recover a large amount of energy lost through the exhaust and use it to reduce fuel consumption. This paper concerns the modification of a conventional two in-line cylinders Diesel engine (440 cm3) adding a variable geometry turbine (VGT) coupled with a generator. The turbine is used to recover exhaust gas energy that otherwise would be lost. The generator, connected to the turbo shaft, converts mechanical energy into electrical energy and is used to charge the vehicle battery or the auxiliaries. The aim of this work is reducing fuel consumption by replacing the alternator with a kind of electric turbo-compounding system to drive vehicle auxiliaries. If the selected turbine recovers enough energy to power auxiliaries, the alternator, which usually has low efficiency, can be removed. Along these lines, fuel consumption savings can be achieved. At a later stage, a microcar has been tested on WLTC (Class 1) driving cycle. The results show fuel consumption reduction of 6 to 9%, depending on VGT size. Indeed, four different VGT sizes have been analyzed to choose the optimal configuration that reflects a compromise between energy recovery and fuel consumption reductions.

Ortenzi, Fernando, Genovese, Antonino, Carrazza, Martina, Rispoli, Franco, Venturini, Paolo

Novel Rankine Cycle for Hybrid Vehicles

2018-01-17119/10/2018

The European Union (EU) has defined legally-binding targets for the fleet of new cars allowing 95 grams CO2 per kilometer in 2021. It is already under discussion to reduce average emissions of the EU car fleet by further 15% in 2025 and again by 30% in 2030 compared to 2021 goal. Therefore, improvement of fuel economy is becoming one of the most important issues for the car manufacturers. Today’s conventional car powertrain systems are reaching their technical limits and will not be able to meet future fuel economy targets without further development of additional measures. This paper presents the analysis of a Rankine cycle unit applied to improve the overall efficiency of a hybrid electric vehicle (HEV). The authors propose a new concept for recovering a considerable part of exhaust waste heat from an HEV with spark ignition internal combustion engine (ICE) by applying a bottoming Rankine cycle with a Ruths storage tank. It enables the storage of discontinuously available exhaust waste heat from the internal combustion engine as sensible heat in a pressurized working fluid. Thus, the vapor generating process is temporally decoupled from the transient engine operating condition and its unsteady flow of exhaust heat energy. The major benefits of this proposed concept are the utilization of recovered waste heat energy within the hybrid electric powertrain and faster engine warm up resulting in optimum ICE operating conditions. The potential for fuel economy improvement for the proposed powertrain concept is demonstrated in standard certification cycles by applying vehicle simulation. The simulation models used in this study were validated by experiments.

Kraljevic, Ivica, Gottwald, Theo, Spicher, Ulrich

Simulative Evaluation of Various Thermodynamic Cycles and the Specification of Their System Components Regarding the Optimization of a Cogeneration Unit

2018-01-50349/5/2018

Given the increasing globalization and industrialization, the worldwide demand for energy continuously increases. In the context of modern Smart Grids, especially small and distributed power plants are a key factor. The present article essentially focuses on the investigation of different approaches for waste heat recovery (WHR) in small-scale CHP (combined heat and power) applications with an output range of approximately 20 kW. The engine integrated into the CHP system under investigation applies a lean-burn combustion process generally providing comparatively low exhaust gas temperatures, thus requiring a careful design that is crucial for efficient WHR. Therefore, this article presents the development and use of a simulation environment for the design and optimization of WHR in small-scale CHP applications. The MATLAB-based code allows various combinations of specific components (e.g., heat exchangers and pumps, as well as turbines and compressors) in different thermodynamic cycles. The focus of this article essentially lies on the comparison of the Joule-Brayton and the Clausius-Rankine cycle regarding operating characteristics as well as the selection of specific working fluids. For the Brayton cycle, the working fluid’s heat capacity and molar mass mainly define feasible operation ranges. Among the working fluids taken into consideration, ammonia indicates the highest potential adding approximately 10% effective net power and increasing the electrical efficiency by about 2%-pts. The Rankine cycle (RC), however, mainly depends on the working fluid’s evaporation. Here, organic working fluids and refrigerants, respectively, indicate highest potentials adding about 19% net power and increasing electrical efficiency by approximately 3%-pts. For applications mainly requiring additional thermal energy, the RC using, for example, ethanol as working fluid provides heated water at temperature levels covering the potential consumption of single households. The Brayton cycle using, for example, ammonia as working fluid, however, allows the feeding of heated water into a district heating grid.

Zirngibl, Sebastian Andreas, Günter, Florian, Prager, Maximilian, Wachtmeister, Georg

Evaluation of friction coefficient of lamellar and compacted graphite irons in lubricated ring-on-cylinder system

2018-36-00589/3/2018

The current investigation compares the friction behavior between specimens extracted from engine blocks of grey cast iron (class FC 250 ABNT NBR 6589 standard) and compacted graphite iron (class GJV450 ISO 16112 standard). The effect of wall thickness was evaluated, by extracting samples from regions equivalent to two levels of thickness. The piston ring used was a nitrided martensitic stainless steel with an asymmetric profile, and the lubricant oil was the SAE 30 CF. The tribological tests were conducted at 75 N normal load for a duration of 1 hour, a frequency of 5 Hz and a stroke of 10 mm. The tests were carried out at a controlled temperature of 40° C. In a general way, the compacted graphite irons presented smaller friction coefficients when compared to that observed for the lamellar ones; and the wall thickness showed relevance only for the compacted graphite iron, being the lowest values found for the thinner wall. On the other hand, for the grey cast iron, the wall thickness did not affect significantly the friction behavior. Finally, all materials presented a tendency to a smoothing of the surface after tests.

Vale, João Luiz do, Guesser, Wilson Luiz, da Silva, Carlos Henrique, Pintaúde, Giuseppe

Experimental Investigation and Modelling of a 1.5 kW Axial Turbine for Waste Heat Recovery of a Gasoline Passenger Car through a Rankine Cycle

2018-37-00075/30/2018

The Rankine cycle power system is a promising technology to convert the wasted thermal energy from engines into useful energy. In a way to decrease the CO2 emissions of passenger cars, it is possible to recover the waste heat from the exhaust gas that presents a high exergy compared to other sources of waste heat (engine cooling, exhaust gas recovery cooling, etc.). A Rankine cycle test-rig is designed and built to assess the performance of such a cycle in real operating conditions. The most critical component is the expander. This component needs to be compact, light, efficient, reliable and cheap among other criteria. In this context, a 1.5 kW axial turbine composed of two wheels is tested on a Rankine cycle test-rig coupled with a 150 kW engine. A detailed analysis of the performance is proposed. The maximum turbine mechanical isentropic efficiency reached is 41.5%. A semi-empirical approach is proposed to predict the performance of the axial turbine in a wide range of conditions. Finally, the performance on a driving cycle is compared with another technology of expander (scroll).

Dumont, Olivier

2021-12-29.TEST Towards Optimal Performance of a Thermoelectric Generator for Exhaust Waste Heat Recovery from an Automotive Engine

2018-01-0050

4/3/2018

Thermoelectric generator has very quickly become a hot research topic in the last five years because its broad application area and very attractive features such as no moving parts, low maintenance, variety of thermoelectric materials that total together cover a wide temperature range. The biggest disadvantage of the thermoelectric generator is its low conversion efficiency. So that when design and manufacture a thermoelectric generator for exhaust waste heat recovery from an automotive engine, the benefit of fuel consumption from applying a thermoelectric generator would be very sensitive to the weight, the dimensions, the cost and the practical conversion efficiency. Additionally, the exhaust gas conditions vary with the change of engine operating point. This creates a big challenge for the design of the hot side heat exchanger in terms of optimizing the electrical output of the thermoelectric generator during an engine transient cycle. Based on experimental work and a validated thermoelectric generator dynamic model, the authors have identified a few issues that have big impact on the thermoelectric generator performance for automotive applications. Potential solutions also have been proposed and discussed in this paper. They include module level optimization, heat exchanger design optimization in terms of fin thermal resistance for a transient cycle, assembly and interface optimization aims for compact size and minimized contact thermal resistance, optimization of the number of modules for total maximum power output etc.

Yang, Zhijia, Stobart, Richard, Lan, Song, Mason, Byron, Winward, Edward

A System-Level Approach to the Development of Optimized Waste Heat Recovery Exhaust Evaporators

2018-01-13654/3/2018

This work presents a system-level methodology developed to identify the optimum design of heat exchangers for Organic Rankine Cycle (ORC) Waste Heat Recovery Systems (WHRS) for automotive applications. The optimization of the evaporators is done following an iterative system-level approach, where system and vehicle outputs, such as the Fuel economy (FE) and the System Payback Period are the objects of study. A 1D software has been developed to run an algorithm that, fed with corroborated assumptions, calculates the efficiency of the ORC cycle, the WHRS power output, the WHRS payback period, the FE potential and the Fuel Savings per year - hereby FSPY - for different sets of evaporator designs. The algorithm identifies the optimum trade-off for evaporator efficiency, pressure drop, weight and cost to maximize the system FSPY. The concept of the evaporator is a counter cross-flow heat exchanger; this is, the exhaust gas flows all along the outer case across the internal tubes. The working fluid flows within the tubes transversally in a meander path, in an overall counter current arrangement. There are several geometrical parameters open for optimization, such as the evaporator aspect ratio, cross section vs. length trade-off, arrangement of the tubes, shape of the outer case, number and diameter of the tubes, corrugation of the tubes, transversal and longitudinal corrugation pitch, etc. The resultant performance, size, weight and cost of the heat exchanger depend on which set of parameters is chosen. Moreover, every resultant heat exchanger output is linked in such a way that the optimum trade-off is not trivial.

Folgueira, Adrian, Teniente, Jorge, Carballido, Roman

Review of Exhaust Gas Heat Recovery Mechanism for Internal Combustion Engine Using Thermoelectric Principle

2018-01-13634/3/2018

Automotive power packs have been the focus of research over a long period of time. Among various power packs when we consider internal combustion engines, there is an ample opportunity in developing systems that can make optimal utilization of all the energy streams related to the automotive engine. In this regard utilization of internal combustion engine exhaust waste heat and environmental pollution have been the focus of research in the recent past. About 35% of the automotive input fuel energy is converted to useful crankshaft work and about 30% energy is expelled with exhaust. This leaves about one-third (35%) of the total energy that must be transmitted from the enclosed cylinder through the cylinder walls and head to the surrounding. The exhausted energy from engine results in entropy elevation and solemn environmental pollution. So it is desired to utilize waste heat to the extent possible. The recuperation and utilization of waste heat not only conserves fuel but also additionally reduce the amount of waste heat and greenhouse gases dumped into environment. The objective of this study is to suggest waste heat recovery methods using thermoelectric generator which can be used to power various low energy consumption accessories of an automotive system. Thermo-electric generators are capable of enhancing the thermal efficiency of engines and can utilize the 35% of the exhaust gas stream energy efficiently.

Rathore, Souvik Singh, Singh, Anand, Kumar, Prashant, Alam, Nazish, Sahu, Mithilesh Kumar, R, Sanjay

Waste Heat Recovery System for a Turbocharged Diesel Generator at Full and Part Load Operating Conditions Using Rankine and Organic Rankine Cycles

2018-01-13704/3/2018

Waste Heat Recovery System (WHRS) is used to extract heat from the exhaust gas from internal combustion (IC) engines to produce additional power with increase in overall efficiency of the engine. Amongst various WHRS, this paper focuses on WHRS using Rankine Cycle (RC) and Organic Rankine Cycle (ORC). A 100 kVA (80 kW engine) diesel generator was used for this research. Water, R245fa, and R134a were used as the working fluids for the cycle. To assess the performance of WHRS, the system was designed for 80 kW, 70 kW and 60 kW loads and then, for each designed load the WHRS was run for other loads and then compared. Assessment provide simulation results of RC and ORC using Engineering Equation Solver (EES) software. It was found that using water as the working fluid around 20% additional power was achieved. But it limited the working range of the system making it unsuitable for lower loads of 10 and 20 kW for this generator. R245fa and R134a on the other hand provided comparatively less efficiency but covered wide load range. R245fa showed power improvement of 11.2%, and R134a showed a power improvement of 7.0% at 80 kW. At lower powers of 10 and 20 kW the additional powers were 0.84 kW, 1.35 kW and 0.2 kW, 0.43 kW, for R245fa and R134a, respectively and water as the working fluid could not produce any additional power at these lower loads.

Joshi, Shreyas, Kanchibhotla, Saisri Aditya, Bari, Saiful

Optimum Design Point to Recover Maximum Possible Exhaust Heat Over the Operating Range of a Small Diesel Truck Using Bottoming Rankine Cycle

2018-01-13774/3/2018

This paper focuses on waste heat recovery (WHR) system, which is an efficient technology to reduce fuel and vehicle carbon dioxide (CO2) emissions per kW of power produced. Wide variations of power of a vehicle make it difficult to design a WHR system which can operate optimally at all powers. The exhaust temperature from the engine is critical to design a WHR system. Higher the temperature higher will be the gain from the WHR system. However, as power drops the exhaust temperature drops which makes the WHR system perform poorly at lower powers. In this research, a small diesel truck engine was used to design a WHR system to produce additional power using a Rankine cycle (RC). The WHR system was designed at the rated power and speed of 42.8 kW and 2600 rpm, respectively. At this design point, around 15% additional power improvement was achieved resulting around 13% break specific fuel consumption reduction. Next, the performances of the WHR system were evaluated at different operating points lower than the rated power of the engine covering the range of vehicle operations. At few lower power regions, the WHR system could not produce any additional power due to lower exhaust temperatures when designed at the rated power and speed. Then, the WHR system was designed at lower powers which managed to produce additional powers at few lower power regions, but the overall performances of the WHR system were better when designed at the rated power and speed of the engine.

Kanchibhotla, Saisri Aditya, Bari, Saiful

Exergo-environmental Analysis of Basic and Intercooled-Recuperated Gas Turbine based Aviation Auxiliary Power Unit

2018-01-13764/3/2018

This paper deals with the exergo-environmental analysis of gas turbine with possible application as aviation auxiliary-power-unit (APU). The present work reports a comparison of thermodynamic performance, NOx and CO emission for basic gas turbine cycle (BGT) and intercooled-recuperated gas turbine (IcRcGT) cycle based engines for possible use by the aviation industry as auxiliary power unit (APU). In addition to this environmental sustainability index of these two cycles is also presented. Various cycle operating parameters such as compressor-pressure-ratio (rp,c), combustor-primary-zone-temperature, equivalence-ratio, and residence time have been chosen for analysis of the cycles. Mathematical modeling of the cycles has been done and the same have been coded in MATLAB. Results show that IcRcGT cycle exhibits higher gas turbine power output and gas turbine efficiency in comparison to BGT cycle for the same rp,c and turbine inlet temperature (TIT). Percentage exergy destruction for combustion chamber has been found to be lower for IcRcGT cycle as compared to BGT cycle. NOx and CO emission are higher in case of IcRcGT cycle as compared to BGT cycle. Adoption of the proposed scheme i.e. IcRcGT cycle based APU promises to deliver enhanced performance i.e. thermal efficiency of around 10.62 percentage points higher thermal efficiency as compared to traditional BGT based APU (rp,c = 2.6 and TIT = 1400K). Also for the proposed APU system, percentage exergy destruction for combustion chamber is reduced by around 14.95% and by 13.18% for the overall cycle (rp,c = 3.8 and TIT = 1300K). Also, IcRcGT cycle is more sustainable aviation APU technology as compared to BGT cycle.

Sahu, Aishi, Sahu, Mithilesh Kumar, R, Sanjay

Thermodynamic Cycle and Working Fluid Selection for Waste Heat Recovery in a Heavy Duty Diesel Engine

2018-01-13714/3/2018

Thermodynamic power cycles have been shown to provide an excellent method for waste heat recovery (WHR) in internal combustion engines. By capturing and reusing heat that would otherwise be lost to the environment, the efficiency of engines can be increased. This study evaluates the maximum power output of different cycles used for WHR in a heavy duty Diesel engine with a focus on working fluid selection. Typically, only high temperature heat sources are evaluated for WHR in engines, whereas this study also considers the potential of WHR from the coolant. To recover the heat, four types of power cycles were evaluated: the organic Rankine cycle (ORC), transcritical Rankine cycle, trilateral flash cycle, and organic flash cycle. This paper allows for a direct comparison of these cycles by simulating all cycles using the same boundary conditions and working fluids. To identify the best performing cycle, a large number of working fluids were evaluated with regards to the maximum power output of the power cycle for each heat source. Taking into account the constraints and boundary conditions, this study shows that the ORC gives the best performance with a power output of around 1.5 kW for the coolant, 2.5 kW for the exhaust gas recirculation cooler, and 5 kW for the exhaust with acetone, cyclopentane and methanol as the best performing working fluids.

Rijpkema, Jelmer, Andersson, Sven, Munch, Karin

2021-12-29.TEST Micro-Channel Heat Exchanger: An Exhaust Waste Heat Recovery Device

2018-01-0052

4/3/2018

Almost one-third of the fuel energy is wasted through the exhaust of a vehicle. An efficient waste heat recovery (WHR) process will undoubtedly lead to improved fuel efficiency and reduced greenhouse gases (GHG) emission. Currently, there are multiple WHR technologies that are being investigated by various entities in the auto industry. One relatively simple device to extract heat energy from the exhaust is a heat exchanger. Heat exchangers are used in some automotive applications to transfer heat from the hot exhaust gas to the colder coolant fluid to raise the coolant temperature. The warmer coolant fluid can be used for several purposes such as; faster heating of the engine’s lubrication oil and transmission fluids during cold starts, and faster cabin heating, which in turn, can potentially improve the overall engine efficiency and reduce exhaust emissions. Currently, in the US market place, hybrid vehicles, such as the Toyota Prius and Chevy Malibu, use heat exchangers as an integral part of their WHR systems. While traditional heat exchangers have been studied and employed in some automotive applications, the use of a micro-channel heat exchanger (MCHX) is a relatively new concept. Especially, in the realm of automobiles, use of micro-channel heat exchanger is unprecedented. As the name suggests, the micro-channel heat exchanger may provide a significant advantage in terms of packaging compared to a traditional heat exchanger when higher thermal performance is desired. However, the MCHX design has to be optimized for a particular application to avoid creating high backpressure in the exhaust system. In this paper, the design and performance of a micro-channel heat exchanger is described for a range of exhaust mass flows and temperatures. Predicted results from two 1-D models developed using the GT SUITE and Excel are compared and validated against preliminary experimental results from a prototype MCHX design. Finally, the thermal performance of the MCHX is compared to other traditional heat exchangers.

Sahoo, Dipankar, Gardner, Timothy, Whyatt, Greg

Novel Approach to Integration of Turbocompounding, Electrification and Supercharging Through Use of Planetary Gear System

2018-01-08874/3/2018

Technologies that provide potential for significant improvements in engine efficiency include, engine downsizing/downspeeding (enabled by advanced boosting systems such as an electrically driven compressor), waste heat recovery through turbocompounding or organic Rankine cycle and 48 V mild hybridization. FEV’s Integrated Turbocompounding/Waste Heat Recovery (WHR), Electrification and Supercharging (FEV-ITES) is a novel approach for integration of these technologies in a single unit. This approach provides a reduced cost, reduced space claim and an increase in engine efficiency, when compared to the independent integration of each of these technologies. This approach is enabled through the application of a planetary gear system. Specifically, a secondary compressor is connected to the ring gear, a turbocompounding turbine or organic Rankine cycle (ORC) expander is connected to the sun gear, and an electric motor/generator is connected to the carrier gear. The planetary gear system is equipped with a dry clutch and a band brake allowing flexibility in mechanical and electrical integration of the turbocompound turbine, secondary compressor and electric motor/generator to the engine. The system provides the ability to do electrical integration of turbocompound turbine/ORC expander when the turbine power output is low and mechanical/power-split integration when the turbine power output is high. At low engine speeds and high loads, the secondary compressor can provide power from the turbocompound turbine or from the electric motor. Furthermore, the electric motor/generator can be used for regenerative braking as well as to provide torque assist to the engine when possible. The 1D simulation tool GT-Power was used to evaluate the performance of this planetary gear enabled approach against an approach that integrates each of these technologies (a turbocompound turbine, a 48 V belt starter generator and a 48 V e-compressor) independently on a downsized four cylinder diesel engine applied in a medium heavy-duty class 6/7 vocational vehicle. The fuel consumption of both approaches was compared over the engine map and over engine certification test cycles. The simulations demonstrated the ability of the planetary gear coupled system to match the engine performance of the baseline 7.7 L 6 cylinder engine while providing an additional fuel consumption benefit when compared to independent integration of these technologies. Finally, a 3D CAD model of the planetary gear coupled system was developed and the space claim was compared against the baseline 6 cylinder engine.

Joshi, Satyum, Dahodwala, Mufaddel, Koehler, Erik W., Franke, Michael, Tomazic, Dean, Naber, Jeffrey

Range Extension Opportunities While Heating a Battery Electric Vehicle

2018-01-0066

4/3/2018

The Kia Soul battery electric vehicle (BEV) is available with either a positive temperature coefficient (PTC) heater or an R134a heat pump (HP) with PTC heater combination [1]. The HP uses both ambient air and waste heat from the motor, inverter, and on-board-charger (OBC) for its heat source. Hanon Systems, Hyundai America Technical Center, Inc. (HATCI) and the National Renewable Energy Laboratory jointly, with financial support from the U.S. Department of Energy, developed and proved-out technologies that extend the driving range of a Kia Soul BEV while maintaining thermal comfort in cold climates. Improved system configuration concepts that use thermal storage and waste heat more effectively were developed and evaluated. Range extensions of 5%-22% at ambient temperatures ranging from 5 °C to −18 °C were demonstrated. This paper reviews the three-year effort, including test data of the baseline and modified vehicles, resulting range extension, and recommendations for future actions.

Meyer, John J., Lustbader, Jason, Agathocleous, Nicos, Vespa, Antonio, Rugh, John, Titov, Gene

2021-12-29.TEST Study of CO ₂ /Hydrocarbons Mixture as the Working Fluids for Engine Waste Heat Recovery

2018-01-0049

4/3/2018

Transcritical Rankine cycle (TRC) is a promising technology for the engine waste heat recovery due to its good temperature matching ability for the waste heat sources. As for the high-temperature engine exhaust, working fluids selection has been an essential issue without a good solution. It was found in this research that mixtures of CO2 and small molecule hydrocarbons are the potential working fluids for the engine waste heat recovery, since they have good chemical stability and thermal performance. Besides, CO2 can be used as the retardant to suppress the flammability of hydrocarbons to ensure safety. In this research, CO2 mixed with five small molecule hydrocarbons are proposed as the working fluids. A thermodynamic model of TRC system is established to evaluate the thermal performance of those mixtures. The effects of mass fraction of CO2, turbine inlet temperature and pressure are investigated. The influence of composition shift is also discussed. The results show that, 65% CO2 in the mixtures is a tremendous improvement for the system safety, comparing to pure hydrocarbons. Compared with the pure CO2 TRC system, the thermal performance of the system can be effectively improved by mixing appropriate hydrocarbons with CO2, and the operation pressure can be decreased, which is beneficial for the future application. Take CO2/n-Pentane for example, the thermal efficiency and net power output can reach up to 16.4% and 16.06 kW, increasing by 34.4% and 13.3% compared with pure CO2. And the composition shift of those mixtures has little effect on the performance of TRC, but can improve the TRC system safety.

Shu, Ge-Qun, Yan, Nanhua, Zhao, Mingru, Li, Linqing

Engine oil Thermal Management: Oil Sump Volume Modification and Heating by Exhaust Heat During ICE Warm Up

2018-01-13664/3/2018

In the perspective of fuel saving and emissions reduction, engine oil thermal management has not yet received the attention it deserves. Lubricating oil, in fact, should be the focus of a specific warmup action: the expected benefits is on friction reduction – mechanical efficiency improvement – but also on a positive interaction with the cooling fluid thermal dynamics. The lower thermal capacity of the circulating oil (with respect to the cooling fluid) and the instantaneous reduction of the viscosity due to temperature increase produces a faster engine overall efficiency benefit: this invites to focus specific actions on its thermal management in the direction of speeding up the temperature rise during a cold engine starting. Being the mechanical engine efficiency strongly influenced by the friction losses and considering the important benefits on oil viscosity due to a temperature increase, important beneficial effects should be observed on fuel consumption: unfortunately, the big oil quantity inside the oil sump delays the oil warm-up which is continuously heated during the engine passage but also remixed inside the oil sump in which a great oil quantity is present. So, during a homologation cycle for passenger cars and light duty engines, the oil temperature rise is dominated by the mass inside the oil sump: considering that the oil flow rate is limited by the limited engine speed of rotation. In this paper, a modified oil sump has been designed and tested on an Iveco F1C 3 L engine test bench in order to temporarily reduce the oil quantity from which the oil pump aspirates it. In this way, the oil is remixed with a smaller oil quantity inside the sump, speeding up its temperature rise. When the engine reached a thermal stabilized state, the capacity of the oil sump is restored to its full capacity. The temporarily volume reduction of the oil inside the sump is realized by modifying it with a metal septum that divides the capacity into two parts: a thermo-controlled opening links the two parts together when the oil reaches the design temperature. Fuel consumption and CO2 emission reduction have been demonstrated and this further positive result has been added to another positive action in order to further speed up its temperature, using exhaust heat to warm the oil. Fuel consumption benefits has been demonstrated and pollutants reduction has been also reported, produced by the modified thermal behavior of the whole engine due to the positive interactions with the cooling fluid.

Di Battista, Davide, Cipollone, Roberto, Fatigati, Fabio

Part-Load Performance Analysis of an Electricity-Cooling Cogeneration System for Engine Waste Heat Recovery

2018-01-13754/3/2018

Gaseous fuel internal combustion engines (gas engines) for electric generating are important primary movers in distributed energy systems. However, the average thermal efficiency of the gas engine is just about 30%-40% and most of the waste heat is discharged by exhaust. So it is very meaningful to recover the exhaust waste heat. Electricity-cooling cogeneration system (ECCS) inclusive of a steam Rankine cycle (RC) and an absorption refrigeration cycle (ARC) is an effective way for recovering exhaust waste heat of gas engine. Partload performance analysis of ECCS is of great significance due to the frequently varied working conditions of gas engines in practical operation. In this paper, an off-design simulation model of ECCS is firstly established by Matlab. Then the effects of the engine working condition on the performance of ECCS are analyzed by this model. The results indicate that ECCS can improve the thermal efficiency of gas engine by 15.2%-16.9% from 40% to 100% working condition, which proves the excellent part-load adaptability of ECCS. Results would have guiding significance in practical operation of ECCS.

Jing, Dongzhan, Shu, Ge-Qun, Wang, Xuan

2021-12-29.TEST Performance of a Half-Heusler Thermoelectric Generator for Automotive Application

2018-01-0054

4/3/2018

Thermoelectric generators (TEGs) have been researched and developed for harvesting energy from otherwise wasted heat. For automotive applications this will most likely involve using internal combustion engine exhaust as the heat source, with the TEG positioned after the catalyst system. Applications to exhaust gas recirculation systems and compressed air coolers have also been suggested. A thermoelectric generator based on half-Heusler thermoelectric materials was developed, engineered, and fabricated, targeting a gasoline passenger sedan application. This generator was installed on a gasoline engine exhaust system in a dynamometer cell, and positioned immediately downstream of the close-coupled three-way catalyst. The generator was characterized using a matrix of steady-state conditions representing the important portions of the engine map. Detailed performance results are presented. Measurements indicate the generator can produces over 300 W of power with 900 °C exhaust at relatively high flow rates, but less than 50 W when the exhaust is 600 °C and at lower flow rates. The latter condition is typical of standard test cycles and most driving scenarios.

Szybist, James, Davis, Steven, Thomas, John, Kaul, Brian C.