Heavy-duty Commercial Vehicles Research Articles

Role of proton exchange membrane fuel cell in efficiency improvement of ammonia–hydrogen fusion zero-carbon powertrains for long-haul, heavy-duty transportation

Ammonia fuel, a transport zero-carbon energy carrier with a much lower life-cycle greenhouse gas footprint than existing fuels and the ability to overcome the storage and transportation challenges of hydrogen fuel, is an effective means of realizing the energy transition for long-haul, heavy-duty transportation such as heavy trucks. Although the efficient use of liquid ammonia fuel cannot be realized directly at this stage, it can be realized indirectly by converting ammonia fuel into hydrogen and combining the hydrogen generated with ammonia in an ammonia–hydrogen fusion fuel supply method. In this study, we assess four ammonia–hydrogen fusion-fueled zero-carbon powertrains for heavy-duty commercial vehicles, each of which is designed to determine its most efficient green zero-carbon fuel utilization scenario at the point of steady state operation as well as over the entire power-demand interval. It was found that the required engine capacity decreases with the increase of the hydrogen energy ratio in the ammonia–hydrogen composite fuel. Considering the indicated thermal efficiency of the engine and the combustion stability in the cylinder, the ammonia–hydrogen composite fuel with 30% hydrogen energy share was selected for the matching design of the powertrains. The study results show that powertrain equipped with engine and fuel cell are more energy efficient than others. The powertrain with range extender consisting of the engine and fuel cell takes ammonia dissociation separation unit and fuel cell as an important part of engine exhaust gas heat recovery, which reduces the dependence of ammonia cracking hydrogen production on electric heating power. By regulating the energy distribution ratio between the engine and the fuel cell, the system can be maintained at a high level of energy efficiency. Under different power requirements of highway application scenarios, the system efficiency is not less than 36%, and the system energy utilization efficiency is higher than 44%. Compared to engine direct drive powertrain, engine range-extended powertrain, and fuel cell range-extended powertrain, the average system efficiency increases by 30.8%, 8.68%, and 14.24%, while the average system energy utilization increased by 41.12%, 25.26%, and 39.43%, respectively.

Hydrogen-diesel dual-fuel combustion sensitivity to fuel injection parameters in a multi-cylinder compression-ignition engine

Adding hydrogen to the intake of a diesel engine offers a near-term route to reducing greenhouse gas emissions from heavy-duty commercial vehicles. Variations in combustion behavior between cylinders can limit the performance and H2 utilization in these engines. This research evaluates the impacts of varying H2 concentrations between cylinders due to the phasing of pulsed fuel injection in the intake manifold, and the potential to optimize the diesel injection strategy for each cylinder to compensate for these effects. The study is conducted using a predictive phenomenological combustion model for H2-diesel combustion within the GT-SUITE™ software environment calibrated and validated using experimental data from a 4-cylinder, 5.2 L engine at three loads and at two different H2 concentrations per load. Predictions of engine and combustion performance were within 5% of the experimental results for key parameters. The validated model is then used to quantify the impacts of varying H2 distribution between cylinders on combustion performance and hardware limitations including peak cylinder pressure, rate of pressure rise, and exhaust temperature. From these results, the diesel injection parameters, including timing and quantity of both pilot and main injections, are optimized for each cylinder to minimize variations in engine performance. The results indicate that cylinder-to-cylinder variations in H2 concentration increased with more rapid H2 injection, due to limited dispersion of H2 between the cylinders. Variations in indicated power approached 13.5% between cylinders, with those with high H2 content encountering a substantial risk of knock and noise. Adjusting the diesel injected mass per cylinder balanced power variations, while adjusting pilot injection timing minimized variations in the rate of pressure rise (dP/dCA). Exhaust temperature and efficiency were most sensitive to the timing of the main diesel injection. Combined, these control approaches reduced diesel fuel consumption and CO2 emission by 5.2 and 6.2%, respectively, where an average 3.8% increase in the engine's indicated efficiency was observed. The optimization findings offer a promising approach for balancing the engine performance when there is unbalanced H2 distribution between the cylinders.

Effect of differential control and sizing on multi-FCS architectures for heavy-duty fuel cell vehicles

The current trend towards a zero-emission transport sector has increased the interest of the scientific community and the industry in fuel cell (FC) technologies in the past few years. Previous studies have focused on passenger car analyses to differentiate them from the current battery electric vehicle (BEV) alternative. However, deploying these technologies may be even more critical for the transportation-produced global emissions if they are used in different applications, such as heavy-duty commercial vehicles. This study uses a differential control strategy to find the best fuel-cell performance for a heavy-duty vehicle application. In addition, and as a differentiation point from other studies in the literature, this article exploits the modularity of the heavy-duty truck sector to implement a design with optimal fuel cell system (FCS) sizing and control dynamics distribution in terms of durability and H2 consumption. Low dynamics could increase 471% in durability just for a 3.8% increase in H2 consumption. When using a multi-FCS with non-equal power FCS, a high dynamics behavior of the small FCS significantly improves the durability for a small consumption penalty (less than 0.7%). The obtained data has proven that the combination of these two design strategies shows an improved vehicle performance that could lead to environmental impact and cost reduction, which is significant in the current development stage of fuel cell vehicle (FCV) technologies.

Design of an Optimum Compact EGR Cooler in a Heavy-Duty Diesel Engine towards Meeting Euro 7 Emission Regulations

Exhaust gas recirculation (EGR) has been an efficient emission treatment strategy employed in internal combustion engines (ICEs) to cope with NOx emission limits since the introduction of Euro 4 regulations for heavy-duty commercial vehicles. A portion of the exhaust gas is fed back into the intake port, replacing O2 in the fresh air with inert CO2 from the exhaust gas, resulting in a reduction in the combustion temperature and, hence, a reduction in NOx emissions. Considering the high exhaust temperature, this process increases the charge mixture temperature and degrades the volumetric efficiency of the engine. EGR coolers have been introduced as vital parts of EGR exhaust treatment systems with the aim of reducing the intake port temperature to increase volumetric efficiency and further reduce combustion temperatures. EGR coolers are heat exchangers (HXs) that generally employ engine coolant to reduce the EGR temperature with effectiveness values around 0.7~0.85 and downgrade with engine usage owing to soot deposition. Increasing the effectiveness of the EGR cooler has a positive effect on engine volumetric efficiency and reduces NOx, particulate matter (PM), and fuel consumption. The current study involved the design of a microchannel HX for a 500 PS heavy-duty Euro 6 diesel engine EGR cooler. The mechanical and thermal-hydraulic design calculations of the proposed HX were performed using Mathematica software. The optimum HX dimensions for the required boundary conditions were determined, and the performance of the EGR cooler was analyzed for the current and proposed options. Furthermore, Diesel-RK software was used to model the engine performance with NOx, PM, CO2 emissions, and fuel consumption predictions. The results show that the newly proposed microchannel HX design improves NOx, PM, and specific fuel consumption by 6.75%, 11.30%, and 0.65%, respectively.

The effects of biodiesel produced from waste cooking oils on vibroacoustic properties of a heavy-duty diesel engine

This paper aims to investigate the vibroacoustic properties of biodiesel produced from waste cooking oils and petroleum-based diesel fuel depending on engine speed and load. Tests were conducted on a diesel engine with a 6 L cylinder volume which is used in today’s heavy-duty commercial vehicles. The engine tests were performed at various speeds and a constant engine load of 100 Nm. A vibration transducer and microphone were used to obtain the experimental data to determine vibroacoustic properties. The root mean square and coherence methods have been used for vibration analysis. The results show that the vibration amplitude of B100 at high engine speeds is slightly higher than that of pure petroleum-based diesel fuel (PBDF). B100 has a maximum 8.5% higher vibration amplitude relative to PBDF at an engine speed of 1500 rpm, where the engine is in the maximum torque intensity. Coherence analysis showed that the engine sound increased with increasing engine speed. The highest sound pressure level was 94.9 dB with B100 at an engine speed of 2000 rpm.

Technical and Economic Analysis to Select Suitable Design Parameters of an E-Machine for Electric Commercial Vehicles

In the European Union (EU), road transport contributes a major proportion of the total greenhouse gas (GHG) emissions, of which a significant amount is caused by heavy-duty commercial vehicles (CV). The increasing number of emission regulations and penalties by the EU have forced commercial vehicle manufacturers to investigate powertrain technologies other than conventional internal combustion engines (ICE). Since vehicle economics plays an important role in purchase decisions and the powertrain of a battery electric vehicle (BEV) contributes to about 8–20% of the total vehicle cost and the electric machine (EM) alone contributes to 33–43% of the drivetrain cost, it is necessary to analyze suitable EM topologies for the powertrain. In this paper, the authors aim to analyze the technical and cost aspects of an EM for electric commercial vehicles (ECV). Based on prior research and literature on this subject, an appropriate methodology for selecting suitable geometrical parameters of an e-machine for the use case of a heavy-duty vehicle is developed using MATLAB and Simulink tools. Then, for the economic analysis of the e-machine, reference ones are used, and their design parameters and cost structures are utilized to develop a cost function. Different use cases are evaluated according to the vehicle’s application. The results for a use case are compared by varying the design parameters to find the most cost-effective EM. Later, an analysis is performed on other decisive factors for EM selection. This highlights the importance of collaborative consideration of technological as well as the economic aspects of EMs for different use cases in ECVs. The method developed in this work contributes to understand the economic aspect of EMs as well as considering their performance factors. State-of-the-art methods and research are used to develop a novel methodology that helps with the selection of the initial geometry of the electric motor during the design process, which can serve to aid future designers and converters of electric heavy-duty vehicles.

Optimization of Engine Control Strategies for Low Fuel Consumption in Heavy-Duty Commercial Vehicles

Optimization of Engine Control Strategies for Low Fuel Consumption in Heavy-Duty Commercial Vehicles

Investigation of the Effect of Loading on Fatigue Life by Comparing Strain Gauge Measurements and Finite Element Analysis Under Gradually Increasing Load in An Axle Housing

In this study, the stress values obtained from commercial finite element analysis software ANSYS® and stress values measured by strain gauges applied on an axle housing in test environment were compared. The axle housing is a test sample from heavy duty commercial vehicles. Besides from stress values comparison, fatigue behavior of the housing was observed under gradually increased loading conditions via hydraulic loaded test benches. Load conditions, configuration change steps, test parameters and fatigue life results will be explained in detail. It was observed that the results of FEA and strain gauge are coherent to each other and as the load was increased, the fatigue life decreased. The stress values in specified points of housing increase linearly with the load increment. However, as predicted, the relationship between load change and fatigue life is not linear. For instance, fifty percent increase in load reduces life by about seventy-five percent. The aim of the study is firstly correlate the FEA results by comparing with the test measurements and then try to observe the effect of load increase on the fatigue life which will be a beneficial source for estimation of the life of the axle housing under diverse loadings in the further studies.

Investigations on fuel consumption characteristics of heavy-duty commercial vehicles under different test cycle

In order to narrow the gap between real-road and certification test fuel consumption rate of heavy-duty commercial vehicles. CHTC (China Heavy-duty vehicle Test Cycle) series test cycles have been developed, and will replace C-WTVC (China-World Transient Vehicle Cycle) test cycle in the latest standard for fuel consumption rate measurement of heavy-duty commercial vehicle. Due to the change of test cycle, the fuel consumption limits standard should also be revised. In this paper, all kinds of the heavy-duty commercial vehicles have been chosen, and the fuel consumption rates under CHTC and C-WTVC have been measured. The fuel consumption values under idling, acceleration, deceleration and constant speed conditions were calculated after the treatment of same mileage. Also the fuel consumption rate under different conditions were compared in order to realize the reasons causing the fuel consumption rate variation. Results showed that the fuel consumption rate of CHTC were slightly lower than C-WTVC except for bus and coach. And the main reasons for the fuel consumption rate variation were attributed to the fuel consumption rate under constant speed condition and the accelerated condition. In addition, the driving efficiency of the two test cycles was another reason, that is, the difference of the duration of each condition under the same mileage. The longer the duration, the higher the fuel consumption.

Stochastic model predictive braking control for heavy-duty commercial vehicles during uncertain brake pressure and road profile conditions

When heavy-duty commercial vehicles (HDCVs) must engage in emergency braking, uncertain conditions such as the brake pressure and road profile variations will inevitably affect braking control. To minimize these uncertainties, we propose a combined longitudinal and lateral controller method based on stochastic model predictive control (SMPC) that is achieved via Chebyshev–Cantelli inequality. In our method, SMPC calculates braking control inputs based on a finite time prediction that is achieved by solving stochastic programming elements, including chance constraints. To accomplish this, SMPC explicitly describes the probabilistic uncertainties to be used when designing a robust control strategy. The main contribution of this paper is the proposal of a braking control formulation that is robust against probabilistic friction circle uncertainty effects. More specifically, the use of Chebyshev–Cantelli inequality suppresses road profile influences, which have characteristics that are different from the Gaussian distribution, thereby improving both braking robustness and control performance against statistical disturbances. Additionally, since the Kalman filtering (KF) algorithm is used to obtain the expectation and covariance used for calculating deterministic transformed chance constraints, the SMPC is reformulated as a KF embedded deterministic MPC. Herein, the effectiveness of our proposed method is verified via a MATLAB/Simulink and TruckSim co-simulation.

Achieving Diesel Powertrain Ownership Parity in Battery Electric Heavy Duty Commercial Vehicles Using a Rapid Recurrent Recharging Architecture

<div class="section abstract"><div class="htmlview paragraph">Battery electric vehicles (BEV) in heavy duty (HD) commercial freight transport face challenging technoeconomic barriers to adoption. Specifically, beyond safety and compliance, fleet and operational logistics require both high up-time and parity with diesel system productivity/Total Cost of Ownership (TCO) to enable strong adoption of electrified powertrains. At present, relatively high energy storage prices coupled with the increased weight of BEV systems limit the practicality of HD commercial freight transport to shorter range applications, where smaller batteries will suffice for the mission energy requirements (single operational shift). This paper presents an approach to extend the feasibility of BEV HD trucking for a broad range of applications. The concept is based on the leveraging rapid and recurrent recharging of a BEV HD truck that may either already make frequent stops due to shipment drop-offs/reloading or be required to make frequent stops along with longer missions for recharging. While the challenges of the latter are well appreciated, the concept proposed explores making minimal impact to overall mission time by targeting high C-rate charging while optimizing the frequency (miles) through which these events must occur. The concept optimizes battery size and chemistry, such that the expected life (years and total energy throughput) is balanced with the depth of discharge between recharging events, thus making complete use of the energy available through the life of the battery system. The solution is constrained to minimize the impact on payload capacity. The paper analyzes critical levers in achieving diesel price parity (based on a simplified vehicle TCO), achieved through different purchase options (including lease versus buy) and operational models (half-life swap out). Finally, the paper identifies the application design domain where these solutions are viable with limited impact on fleet operations.</div></div>

HV Components for Commercial EVs

A discussion on the benefits of high-voltage components in heavy-duty commercial electric vehicles

Chemistry is Everything

Dedicated lubricants for electrified heavy duty commercial vehicles are designed to handle the high demands of eCV e-motors

Effects of driving cycle on CO2 emission of heavy-duty commercial vehicles based on VECTO simulation

European has adopted Vehicle Energy Consumption Calculation Tool (VECTO) to calculate the fuel consumption of heavy-duty commercial vehicles for fulfill the carbon-neutral requirement. In this paper, VECTO was used to evaluate the CO2 emission for four types of vehicles including city bus, coach, heavy truck and trailer tractor. China Version World Transient Vehicle Cycle (C-WTVC) and China Heavy-duty Commercial Vehicle Test Cycle (CHTC) were used as simulation cycles. The CO2 emission characteristics and cycle differences of both cycles were compared and analyzed. The results show that CO2 emissions of CHTC are higher than that of C-WTVC for these four types of vehicles with increase percentages ranging from 1.5% to 19%. Cycle average acceleration difference is the most predominant factor. Driving strategy changes due to the cycle difference also lead to the CO2 emission difference because the engine operation points has changed to some extent.

Fuel consumption comparison of heavy-duty commercial vehicles under CHTC and C-WTVC cycles based on VECTO

In this paper, the simulation method of calculating the fuel consumption of heavy-duty commercial vehicles based on VECTO (Vehicle Energy Consumption Calculation Tool) was introduced, and the fuel consumption of four vehicles under C-WTVC and CHTC cycles was calculated with VECTO. The differences between C-WTVC and CHTC cycles were analyzed by comparing the characteristic parameters, and the fuel consumption map and driving acceleration of two cycles were compared, so as to explore the influence of different test cycles on fuel consumption. The results show that compared with the C-WTVC cycle, the fuel consumption of CHTC cycle increases by 17.08g/km~28.12g/km, with an increase of 6.42%~17.26%. Most of the engine working points in the CHTC cycle work in the middle and low speed and torque regions and the acceleration range of CHTC cycle is wider are important reasons for the increase of fuel consumption.

Scenario-oriented stacks allocation optimization for multi-stack fuel cell systems

The multi-stack fuel cell system (MFCS) could have advantages (e.g. higher efficiency, stronger robustness, longer lifetime, etc.) versus the single-stack fuel cell system (SFCS) in high-powered application scenarios. For an application scenario with its probability distribution of electrical power demands, the optimization problem of stacks allocation is generally proposed for the MFCS under constraint conditions of the probability distribution and characteristics (e.g. specific efficiency curves) of a set of available stacks. As a special case, a decision model of MFCS stacks allocation and related power management for the application of heavy-duty commercial vehicles is established with an integrated optimization index of efficiency and remaining useful life (RUL) and co-solved by iterative and heuristic algorithms. The optimal stacks allocation schemes for three stacks to five stacks is obtained. The optimal stacks output powers scheme is analyzed with three stacks. Finally, the solution results are investigated and analyzed through change the impact factors of efficiency weights, application scenarios, the efficiency, and RUL characteristics of available stacks.

Evaluating Influence of On-Road Parameter Variation in HD Application Using Virtual Approach for Upcoming IRDE Norms

<div class="section abstract"><div class="htmlview paragraph">Real Driving Emission (RDE) norms have changed the way vehicles are required to be calibrated and developed. This has moved the legislative requirements from predictable lab conditions to more realistic, real world conditions. Current Indian legislation allows certification for Heavy Duty (HD) applications on engine level and therefore decoupled from vehicle and the real world scenarios such as uncertainty and randomness in driver behavior, traffic conditions, road profiles, ambient conditions etc. which are not captured. Upcoming RDE legislation to be implemented in year 2023, has made it necessary to integrate engine with vehicle to consider the impact of various parameters on engine operating points and therefore on tail pipe emissions. This paper focusses upon the methodology developed using RDE cycle generator tool (RCG) for generating on-road parameters which influences the zone of engine operation and resulting emission levels. At ARAI, we have established a calibration strategy for Heavy Duty Commercial Vehicles for BS-VI RDE using virtual technique, which can be easily extendable to passenger vehicles as well. Virtual Test Bed (VTB) approach gives advantage to include all possible variations during early stages of vehicle calibration and therefore making it more robust. RDE Cycle Generator (RCG) module from AVL is used to generate GPS based road profile data including gradients and realistic traffic conditions. The module is capable to consider Indian legislative requirements for HD application requirements. The well validated Real Time (RT) HD vehicle plant model capable of complying to BS-VI norms is considered for evaluating influence of different parameters. Different routes are generated by varying parameters such as driver characteristics, traffic conditions, start and stop criteria etc. The vehicle is operated virtually under all possible extreme conditions to evaluate the engine-operating zone and accordingly revisit the calibration requirements to avoid surprises during real vehicle testing. The convenience of changing any critical parameter on RCG and then running vehicle virtually on VTB has benefitted in reducing the time and efforts for calibration and focusing more on calibration work and thus will help in achieving In-Service Conformity (ISC) requirements more confidently.</div></div>

Experimental studies regarding the thermal operating regime for SCR catalysts of heavy-duty commercial vehicles

SCR, selective catalytic reduction, is the most efficient method for treating nitrogen oxides – one of the main pollutants of internal combustion engines. The SCR system involves the injection of a reductant (the solution AdBlue) in the exhaust gas flow, the reduction of the oxides being achieved in the catalyst’s interior [1,4,6]. The operating limits of the SCR system are given by need to maintain the temperature conditions for the injected solution as well as the catalyst and its internal components (oxygen and temperature sensors, reductant injector) [2]. Overheating the AdBlue injectors may have a major influence for the operation of the SCR system, the deposits of the decomposed solution within the injectors leading to the system’s out of use. Thus, maintaining an optimum thermal regime by cooling the AdBlue injectors becomes a required solution for a good functioning of the entire system. The paper presents experimental studies in relation to the thermal evolution of SCR catalysts on heavy-duty commercial vehicles in different turnover situations as well as an analysis of the measured values.

The Norwegian Vehicle Electrification Policy and Its Implicit Price of Carbon

The rapid market uptake of battery and hybrid electric cars in Norway is unparalleled. We examine the fiscal policy instruments behind this development. In essence, the Norwegian policy consists in taxing internal combustion engine vehicles rather than subsidizing electric ones. There are 14 different fiscal incentives in place bearing on vehicles, fuel, or road use. All of them are in some way CO2-differentiated. In the tradition of positive economics, we derive the price of carbon implicit in each policy instrument and in the total package of taxes and subsidies. The price of carbon characterizing the trade-off between conventional and battery electric cars in Norway as of 2019 exceeds €1370 per ton of CO2. For light and heavy-duty commercial vehicles the corresponding prices have been conservatively estimated at €640 and €200 per ton of CO2, respectively. In addition, the penalty incurred by automakers for not meeting their 2020/2021 target under EU Regulation 2019/631 corresponds to a carbon price of the order of €340 per ton of CO2. As compared to the price of emission allowances in the European cap-and-trade system, the price of carbon paid by automakers and Norwegian motorists is one or two orders of magnitude higher.

Torsional vibrations in heavy-duty truck powertrains with dual mass flywheels

Many of the measures taken to improve combustion engine efficiency lead to higher torsional vibrations. For heavy-duty commercial vehicles it is foreseen that the conventional flywheel and clutch will not be able to sufficiently reduce those increased engine torsional vibrations to the driveline. In this paper, the steady-state torsional vibrations in a heavy-duty truck powertrain are studied. The focus is engine excited vibrations at high load within operating speed range. Vibration phenomena in a conventional heavy-duty powertrain and in powertrains equipped with dual mass flywheels are studied. It is shown how the use of a dual mass flywheel can enable down-speeding and increased engine torque with maintained or reduced levels of torsional vibrations.