Browse Topic: Medium trucks
The recent addition of fully electric powertrains to propulsion system options has increased the relevance of sound and vibration from electric motors and gearboxes. Electrified beam axles require different metrics from conventional beam axles for noise and vibration because they have multiple sources of vibration energy, including an electric motor and a reduction gearbox. Improved metrics are also driven by the stiff suspension connections and lack of significant isolation compared to electric drive units. Blocked force is a good candidate because it can completely characterize the vibration energy transmitted into a receiver and is especially useful because it is theoretically independent of the vehicle-side structure. While the blocked force methodology is not new, its application to beam axles is relatively unexplored in the literature. This paper demonstrates a case study of blocked force measurement of an electrified beam axle with a leaf spring suspension. The axle was tested both in vehicle and in a hemianechoic axle test cell. Measurement setup, including the selection of interface, instrumentation, and impact locations, is discussed. Comparisons between the blocked forces measured in vehicle and in dyno are made. Several key learnings, opportunities for measurement improvement, and ideas for future work are also addressed.
REE Automotive is aiming to be a major disruptor in the medium-duty truck space with the rollout of its P7 EV chassis. The P7 frame is built around its “REEcorners” suspension, which are modular suspension units featuring REE's x-by-wire design. By packaging components into the area between the chassis and the wheel, REE claims that it was able to design the P7 with a completely flat chassis with up to 35% more interior volume for passengers, cargo and batteries. “The REEcorners suspension system is the core of the technology that we built this truck around,” Peter Dow, VP of engineering for REE Automotive, said during an interview with Truck & Off-Highway Engineering. “It also allows us to achieve the level of vehicle dynamics we were looking for. We were trying to make a truck that was very exciting and easy to drive.”
Improvements in component/system design is a daily challenge these days, always looking for high performance, reduced mass and low costs. The source for the best fit between these factors, coupled with adequate durability performance, is crucial to the success of a given product and this is what motivates engineering teams around the world. The demand for efficient projects with short deadlines for validation and certification is huge and simulation tools focused on accelerated durability and virtual validation are increasingly being used. When developing a new spring for commercial vehicles, lessons learned from the actual loads applied to the suspension are the “key” to a successful project. The loads/stresses from the ground (vertical loads, lateral loads, longitudinal and braking loads) are quite high and, consequently, relevant to the proper definition of the design of the suspension components. The objective of this work is to describe the main development activities faced during a completely new spring development, passing through the design, considering all the limit conditions related to the raw material, lamination process, tempering, rhinestone/shot peening, prefixing and, finally, the load conditions for an adequate fatigue life. The methodology adopted for the definitions of load and fatigue in a bench test is part of this document and, in the end, all iteration results, such as correlation with the application, the MBS and FEA models to be fed again until final validation in a vehicle. This document is a joint development made in partnership between Thyssen Krupp Springs and Stabilizer Bars, Dana Corporation and Volkswagen Truck & Bus (VWTB).
Several commercial truck OEMs revealed new medium-duty EVs at NTEA's 2023 Work Truck Week (WTW) in Indianapolis, Indiana. Interest in Class 5, 6 and 7 EVs has ramped up rapidly in recent years, and many OEMs are rolling out new models to meet the increased demand.
Allison Transmission continues to invest in and accelerate its electric-vehicle propulsion solutions, but it also remains committed to its conventional-product portfolio, which the company expects to remain relevant for decades. Boosting the capabilities of both technology pathways is Allison's next-generation electronic controls platform, which features advanced communications, functional safety, cybersecurity and over-the-air (OTA) programming capability. Allison partnered with multiple OEMs to build the first commercial vehicles equipped with the next-gen platform, which combines state-of-the-art microprocessor and software operating system technology. Freightliner Custom Chassis Corp. has begun producing the first walk-in vans equipped with the enhanced electronic controls. Other OEMs using the new system include Mack Trucks in its medium-duty trucks, Prevost and MAN. Allison expects all OEM partners to transition to this controls platform by February 2023.
The noise and vibration are directly related to the perceived quality of a vehicle and it is crucial that the manufacturers focus their efforts to reduce that. When an unusual noise appears, it is a great challenge to define an approach for understanding the phenomenon, identifying the cause and then defining a solution to reduce its effect. A “knocking noise” coming from the brake rigid pipes is perceived while driving the vehicle in a cobbled pavement at low speed and it coincides with the closure of brake system module inlet valves. When a valve closes quickly, there is a sudden change in the flow velocity, which generates a pressure transient in the brake fluid inducing vibrations in the rigid pipes. The pressure transient can be minimized by reducing the speed at which the pressure waves travel in the pipe. The bulk modulus, the density of the fluid, the velocity of valve closing, the Young’s modulus and the dimensions of the pipes, determine the wave speed. The objective of this work is, first to correlate the phenomenon with the theory regarding the transient flow by presenting the measurements of pressure change in the brake lines during the brake unit valves actuation. Afterwards, evaluate the experimental results of changing the variables that affect the wave speed, and its influence in the noise perception. At the end, show how the application of a hybrid pipe solution, which reduces the Young’s modulus of the brake line, can reduce the pressure transient as well as the “knocking noise”.
In this study, the preliminary validation method of the steering system is constructed and the objective is to satisfy the target performance in the conceptual design stage for minimizing the problems after the detailed design. The first consideration about steering system is how to extract the reliable steering effort for parking. The tire model commonly used in MBD(Multi-Body Dynamics) has limited ability to represent deformations under heavy loads. Therefore, it is necessary to study adequate tire model to simulate the behavior due to the large deformation and friction between the ground and the tire. The two approaches related with F tire model and mathematical model are used. The second is how to extract each link’s load in the conceptual design stage. Until now, each link’s load could be derived only by actual vehicle test, and a durability analysis was performed using only pre-settled RIG test conditions. Therefore, in this study, we established the process of deriving the RIG test conditions by integrating the hydraulic system and the dynamics model without actual vehicle test. The last one is how to apply the flexibility of structure to MBD. In this study, a tool is constructed to automatically reflect the beam’s property by making discrete beam model. As a result, it can be used to set the vehicle’s hard points which minimize the influence between steering system and suspension system on the excessive payload or other events. Through the whole process, we are able to find optimal result by applying the ATC(analysis target cascading) to the steering system concept of the medium truck FMC(Full Model Change).
This paper provides a summary of a Liquefied Petroleum Gas (LPG) concept engine developed for medium duty applications (class 6-7 trucks) targeting high efficiency with a power density that matches turbocharged diesel engines. The turbocharged in-line 6 cylinder engine incorporates an advanced spark ignition combustion system design, a purpose built medium-duty class engine structure optimized for operation with a direct propane injection system, dual overhead cams with individual cam phasers and twin-entry turbocharger. The high tumble charge motion combustion system targeted for operation with direct injected (DI) LPG has resulted in an engine capable of producing up to 22 bar brake mean effective pressure (BMEP) at high brake thermal efficiency (BTE) throughout the operating map. The high BTE combined with low carbon to hydrogen ratio of LPG results in 12% lower Brake Specific CO2 (BSCO2) emissions on the heavy-duty FTP cycle when compared to a diesel engine of same displacement and power and 15-30% lower BSCO2 when compared to other commercially available medium-duty LPG engines. The present work demonstrates total cost savings between 1 and 40% (depending on the cost differential between LPG and diesel) over 10 years on a drive cycle represented by the FTP cycle when compared to a diesel engine with similar displacement and torque curve. The ability to run at or close to Maximum Brake Torque (MBT) spark timing along with low pumping losses have ensured high BTE over the entire operating region of the engine.
Recent research to investigate the aerodynamic-drag reduction associated with truck platooning systems has begun to reveal that surrounding traffic has a measurable impact on the aerodynamic performance of heavy trucks. A 1/15-scale wind-tunnel study was undertaken to measure changes to the aerodynamic drag experienced by heavy trucks in the presence of upstream traffic. The results, which are based on traffic conditions with up to 5 surrounding vehicles in a 2-lane configuration and consisting of 3 vehicle shapes (compact sedans, SUVs, and a medium-duty truck), show drag reductions of 1% to 16% for the heavy truck model, with the largest reductions of the same order as those experienced in a truck-platooning scenario. The data also reveal that the performance of drag-reduction technologies applied to the heavy-truck model (trailer side-skirts and a boat-tail) demonstrate different performance when applied to an isolated vehicle than to conditions with surrounding traffic. The results suggest that vehicle shape optimization strategies may differ if the influence of wake effects from surrounding traffic is included in product development cycles. Additionally, truck-platooning benefits should be taken in the context of typical traffic scenarios for which trucks are already experiencing a background-platooning effect and therefore may not be expected to attain the benefits relative to isolate-vehicle conditions.
The development, analysis, and comparison of battery electric class-4 medium-duty trucks equipped with three possible powertrain layouts, namely, direct drive, single-speed gearbox, and two-speed transmission options, are discussed in this paper. The problem definition is included and the performance evaluation criteria for the proposed truck architectures are defined, namely, acceleration time, top speed, and efficiency. Designs of four new traction motors are proposed and their benefits compared for use in medium-duty electric trucks (e-trucks). The procedure for gear-ratio range selection is outlined, the ranges of gear ratios for the single-speed gearbox and two-speed transmission powertrains being calculated for each of the proposed electric traction motors. The simulation and gear-ratio optimization tasks for the e-trucks are formulated. The energy consumption of the e-truck with the three possible powertrain combinations is minimized over the six driving cycles. The most efficient powertrain layouts that meet the performance criteria are determined.
Higher compression ratio and turbocharging, with engine downsizing can enable significant gains in fuel economy but require engine operating conditions that cause engine knock under high load. Engine knock can be avoided by supplying higher-octane fuel under such high load conditions. This study builds on previous MIT papers investigating Octane-On-Demand (OOD) to enable a higher efficiency, higher-boost higher compression-ratio engine. The high-octane fuel for OOD can be obtained through On-Board-Separation (OBS) of alcohol blended gasoline. Fuel from the primary fuel tank filled with commercially available gasoline that contains 10% by volume ethanol (E10) is separated by an organic membrane pervaporation process that produces a 30 to 90% ethanol fuel blend for use when high octane is needed. In addition to previous work, this paper combines modeling of the OBS system with passenger car and medium-duty truck fuel consumption and octane requirements for various driving cycles. Medium duty driving cycles were included; HHDDT cruise mode for long-haul heavy truck cruising and HTUF 4 for delivery truck duty. Commercial vehicle modeling was done under unloaded, half and fully loaded conditions. Additionally, for the first time, transient separator performance and effective separation limits were included in the evaluation. Separator start-up, and membrane selectivity decrease achievable real-world fuel economy from what can be achieved with two separate tanks: one with gasoline, the other with ethanol. However, using the fuel separation system, the reduction in fuel economy is modest compared to a two tank system with pure ethanol while the need to fill a second tank is removed. Fuel efficiency gains compared to equivalent-performance current engines, including real world limitations ranged from 17.5-30% with commercial gasoline that includes 10% ethanol as base fuel.
In this paper an alternative engineering solution to control vehicle steering wheel vibration is presented. The strategy is focused on the implementation of an effective tuned vibration absorber which also complies with time frame and costs requisites. The vibration levels in this case study are enhanced due resonances in the chassis frame and steering column. The tuned mass damper is basically a suspended mass attached on a vulcanized rubber body, aiming for the customer benefits; this solution can be classified as low cost as well low complexity for implementation. In this case study, a mid-size truck was used as a physical hardware and the data were collected through accelerometers on the steering wheel and other critical components. As a control factor, different tunings on different parts were applied to optimize the auxiliary system performance and robustness. As a final output, the relationship between the tuned mass damper and the acceleration levels on the steering wheel is established. The conclusion of the study presents the optimal results on minimizing the steering wheel vibration through multiple tuned mass damper (TMD) applications, achieving the proposed target levels.
Reducing fuel consumption was a focal point of several trucks unveiled in March. Electric drivetrains and four-cylinder engines were among the tactics disclosed at The Work Truck Show in Indianapolis. Mitsubishi Fuso Truck of America, Inc. rolled out an all-electric medium-duty work truck, the eCanter, which it says will be the first plug-in electric work truck produced by a major truck manufacturer. The Class 4 truck has a payload capacity of roughly 9380 lb (4255 kg).
The government of India has decided to implement Bharat Stage VI (BS-VI) emissions standards from April 2020. This requires OEMs to equip their diesel engines with costly after-treatment, EGR systems and higher rail pressure fuel systems. By one estimate, BS-VI engines are expected to be 15 to 20% more expensive than BS-IV engines, while also suffering with 2 to 3 % lower fuel economy. OEMs are looking for solutions to meet the BS-VI emissions standards while still keeping the upfront and operating costs low enough for their products to attract customers; however traditional engine technologies seem to have exhausted the possibilities. Fuel economy improvement technologies applied to traditional 4-stroke engines bring small benefits with large cost penalties. One promising solution to meet both current, and future, emissions standards with much improved fuel economy at lower cost is the Opposed Piston (OP) engine. Recently, there has been surge in developing highly efficient OP engine architecture to modernize it using today’s analytical tools, high pressure fuel system and manufacturing technologies to meet emissions, while reaping the fuel economy advantage. As the company pioneering the OP engine technology, Achates Power Inc. (API) has been publishing technical papers in recent years, including a paper describing inherent efficiency benefits of OP engines, multi-cylinder steady state and transient results for medium duty truck and light duty applications. This technical paper provides detailed performance and emissions results measured on API’s 4.9L multi-cylinder OP 2-stroke diesel engine configured specifically to meet BS-VI emissions standards for commercial truck application. The results include: Measured performance and emissions data for emissions test cycles. After-treatment details and confirmation to meet tailpipe emissions for BS-VI standards. Details of API’s multi-cylinder test engine’s indicated thermal efficiency, friction and pumping losses. Comparison with 4-stroke diesel engine.
This study aimed to clarify the relationship between truck-pedestrian crash impact velocity and the risks of serious injury and fatality to pedestrians. We used micro and macro truck-pedestrian accident data from the Japanese Institute for Traffic Accident Research and Data Analysis (ITARDA) database. We classified vehicle type into five categories: heavy-duty trucks (gross vehicle weight [GVW] ≥11 × 103 kg [11 tons (t)], medium-duty trucks (5 × 103 kg [5 t] ≤ GVW < 11 × 103 kg [11 t]), light-duty trucks (GVW <5 × 103 kg [5 t]), box vans, and sedans. The fatality risk was ≤5% for light-duty trucks, box vans, and sedans at impact velocities ≤ 30 km/h and for medium-duty trucks at impact velocities ≤20 km/h. The fatality risk was ≤10% for heavy-duty trucks at impact velocities ≤10 km/h. Thus, fatality risk appears strongly associated with vehicle class. The results also revealed that a 10 km/h reduction in impact velocities could mitigate the severity of pedestrian injuries at impact velocities ≥30 km/h for all five analyzed vehicle types. Therefore, serious injuries and fatalities to pedestrians could be decreased by the development and deployment of collision mitigation systems (CMSs) to all vehicles, including to commercial trucks, because CMSs can detect pedestrians in even severe conditions, such as when the drive’s view is obstructed, and can reduce the impact velocity. The present results indicate that CMS design specifications should differ between vehicle types because of the strong dependence of serious-injury and fatality risks on vehicle type.
Various 1D simulation tools (KULI & LMS Amesim) and 3D simulation tools (ANSYS FLUENT®) can be used to size and evaluate truck cooling system design. In this paper, ANSYS FLUENT is used to analyze and validate the design of medium duty truck cooling systems. LMS Amesim is used to verify the quality of heat exchanger input data. This paper discusses design and simulation of parent and derivative trucks. As a first step, the parent truck was modeled in FLUENT (using standard' k - ε model) with detailed fan and underhood geometry. The fan is modeled using Multiple Reference Frame (MRF) method. Detailed geometry of heat exchangers is skipped. The heat exchangers are represented by regular shape cell zones with porous medium and dual cell heat exchanger models to account for their contributions to the entire system in both flow and temperature distribution. Good agreement is observed between numerical and experimental engine out temperatures at different engine operating conditions. Once the CFD approach is validated, CFD simulation is carried out with derivative truck design. The rich information from CFD simulations will be used to evaluate the new designs much faster and eventually improve the efficiency of cooling system designs. Implemented design recommendations are shown to meet the cooling requirements.
In this paper, researchers at the National Renewable Energy Laboratory present the results of simulation studies to evaluate potential fuel savings as a result of improvements to vehicle rolling resistance, coefficient of drag, and vehicle weight as well as hybridization for four powertrains for medium-duty parcel delivery vehicles. The vehicles will be modeled and simulated over 1,290 real-world driving trips to determine the fuel savings potential based on improvements to each technology and to identify best use cases for each platform. The results of impacts of new technologies on fuel saving will be presented, and the most favorable driving routes on which to adopt them will be explored.
Turbocharging, increasing the compression ratio, and downsizing a spark-ignition engine are well known strategies for improving vehicle fuel economy. However, such strategies increase the likelihood of engine knock due to higher in-cylinder pressures and temperatures. A high octane fuel, such as E85, effectively suppresses knock but is not necessary in most parts of the engine operating map. To better utilize a high octane fuel, dual fuel injection has been suggested where high octane fuel is injected only when the engine is about to knock. However, the effects of downsizing, retarding spark timing, and increasing compression ratio on dual fuel applications are not well understood. To investigate these questions, GT-power simulations along with engine experiments and engine-in-vehicle simulations for a passenger vehicle and a medium-duty truck were conducted. First, engine performance maps for various boosts, compression ratios, and spark retards were created, with lines of constant fuel RON superposed. Then, parametric studies were conducted to analyze the effects of cylinder volume/boost level, spark retard, and compression ratio on the vehicle fuel consumption, ethanol usage, and the average engine efficiency. Downsizing a naturally-aspirated engine by 50% resulted in about a 30% increase in fuel economy. Ethanol consumption varied from 5 to 40% (by volume) of the total fuel used, depending on the details. Moderate amounts of spark retard reduced ethanol consumption by half while not deteriorating fuel economy by much. Increasing compression ratio above 11.5 had a marginal return in fuel economy while demanding a significantly larger amount of ethanol.
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