NVH refinement of passenger vehicle is essential to customer acceptance for premium or even mid-size segment passenger cars. Hydraulic engine mount is becoming common for these segments to reduce engine bounce, idle shake and noise transfer to passenger cabin. Modern layout of hydraulic mount with integrated engine-bracket and smaller size insulator has made it cost-effective to use due to reduction of cost gap from conventional elastomeric mounts. However the downsizing and complex internal structure may create some new types of noises in passenger cabin which are very difficult to identify in initial development stage.Main purpose of hydraulic mount is to provide high damping at low-frequency range (6~15 Hz) and to isolate noise transfer from combustion engine to passenger cabin within wide frequency range (15~600 Hz).This paper emphasizes on challenges and problems related to hydraulic mount development. Tuning of Hydraulic mount is required to avoid cavitation noise at low-frequency and also any abnormal noise due to hydraulic unit resonance at higher frequency. Design measures to curb NVH problems, e.g. cavitation noise, bump noise of mount stopper, resonance from…

The Lockheed Martin Low-Speed Wind Tunnel (LSWT) is a closed-return wind tunnel with two solid-wall test sections. This facility originally entered into service in 1967 for aerodynamic research of aircraft in low-speed and vertical/short take-off and landing (V/STOL) flight. Since this time, the client base has evolved to include a significant level of automotive aerodynamic testing, and the needs of the automotive clientele have progressed to include acoustic testing capability. The LSWT was therefore acoustically upgraded in 2016 to reduce background noise levels and to minimize acoustic reflections within the low-speed test section (LSTS). The acoustic upgrade involved detailed analysis, design, specification, and installation of acoustically treated wall surfaces and turning vanes in the circuit as well as low self-noise acoustic wall and ceiling treatment in the solid-wall LSTS. The preservation of the aerodynamic flow quality and the reduction in background noise levels in the LSTS were demonstrated by a series of measurements that were performed both prior to and after the acoustic upgrade.

To face the current challenges of the automotive industry, there is a need for computational models capable to simulate the engine behavior under low-temperature and low-pressure conditions. Internal combustion engines are complex and have interconnected systems where many processes take place and influence each other. Thus, a global approach to engine simulation is suitable to study the entire engine performance. The circuits that distribute the hydraulic fluids -liquid fuels, coolants and lubricants- are critical subsystems of the engine. This work presents a 0D model which was developed and set up to make possible the simulation of hydraulic circuits in a global engine model. The model is capable of simulating flow and pressure distributions as well as heat transfer processes in a circuit. After its development, the thermo-hydraulic model was implemented in a physical based engine model called Virtual Engine Model (VEMOD), which takes into account all the relevant relations among subsystems. In the present paper, the thermo-hydraulic model is described and then it is used to simulate oil and coolant circuits of a diesel engine.…

Indian automobile industry is set to witness the biggest emission reforms of the last two decades with the implementation of BS6 emission norms from 1st April 2020 and Real Driving Emissions (RDE) from 1st April 2023. However, there are still a lot of unanswered questions regarding the test procedure of RDE for India. For India, adopting European RDE test procedure as it is may be a challenge because of the significant differences between India and Europe in terms of weather, geography, demography, road infrastructure, driving behavior and fuel quality. This paper discusses the detailed experimental results of Real Driving Emission tests analyzing after-treatment system configurations (LNT, sDPF, ufSCR) considering different scenarios such as test routes, test days, driving behavior etc. Variation in trip dynamics (Severity, Softness in driving), trip validity and normality and post-processed results are other key points of interests investigated. The overall activity provided great insights into the possible modifications which may be required for RDE test suitable to Indian conditions. The learning such derived will be of immense value for future design…

The effects of Variable Valve Timing (VVT) on Homogeneous Charge Compression Ignition (HCCI) engine energy distribution and waste heat recovery are investigated using a fully flexible Electromagnetic Variable Valve Timing (EVVT) system. The experiment is carried out in a single cylinder, 657 cc, port fuel injection engine fueled with n-heptane. Exergy analysis is performed to understand the relative contribution of different loss mechanisms in HCCI engines and how VVT changes these contributions. It is found that HCCI engine brake thermal efficiency, the Combined Heat and Power (CHP) power to heat ratio, the first and the second law efficiencies are improved with proper valve timing. Further analysis is performed by applying the first and second law of thermodynamics to compare HCCI energy and exergy distribution to Spark Ignition (SI) combustion using Primary Reference Fuel (PRF). HCCI demonstrates higher fuel efficiency and power to heat and energy loss ratios compared to SI. The results are applicable for the development of micro-CHP systems using an HCCI engine operating at a constant engine speed with varying loads.

Superchargers are engine driven positive displacement devices which increase the air mass flow into the engine, thereby leading to a better combustion efficiency. This gives an advantage of extracting more power from the same engine [1], thereby reducing emissions and achieving a better fuel economy [2]. With emission norms getting more and more stringent, the need for boosting engine intake air becomes very important [3]. There are many types of superchargers based on design [4], out of which, the roots-type positive displacement supercharger, is discussed in here. A 1-dimensional model of supercharger gives flexibility of choosing the right aspect ratio (length to the diameter of the rotor), deciding on the clearances (a tradeoff between volumetric efficiency and manufacturing capabilities) and arriving at the inlet and discharge port dimensions. The dependency of the above parameters on mass flow rate of air and volumetric efficiency of the supercharger can be studied in good depth with a simplified one dimensional model [3]. This paper aims to present a one dimensional model of roots-type twin rotor (each 3 lobed)…

Meeting Euro 6d NOx emission regulations lower than 80 mg/km for light duty diesel (60 mg/km gasoline) vehicles remains a challenge, especially during cold-start tests at which the selective catalyst reduction (SCR) system does not work because of low exhaust gas temperatures (light-off temperature around 200 °C). While several exhaust aftertreatment system (EATS) designs are suggested in literature, solutions with gaseous ammonia injections seem to be an efficient and cost-effective way to enhance the NOx abatement at low temperature. Compared to standard SCR systems using urea water solution (UWS) injection, gaseous NH3 systems allow an earlier injection, prevent deposit formation and increase the NH3 content density. However non-uniform ammonia mixture distribution upstream of the SCR catalyst remains an issue. These exhaust gas/ NH3 inhomogeneities lead to a non-optimal NOx reduction performance, resulting in higher than expected NOx emissions and/or ammonia slip. Thus, efficient mixers upstream of the SCR are crucial for the overall EATS performance. In the experimental study reported in this article, planar laser induced fluorescence (PLIF) is used to quantify mixing performance of four novel CFD…

Improved propulsion system cooling remains an important challenge in the transportation industry as heat generating components, embedded in ground vehicles, trend toward higher heat fluxes and power requirements. The further minimization of the thermal management system power consumption necessitates the integration of parallel heat rejection strategies to maintain prescribed temperature limits. When properly designed, the cooling solution will offer lower noise, weight, and total volume while improving system durability, reliability, and power efficiency. This study investigates the integration of high thermal conductivity (HTC) materials, carbon fibers, and heat pipes with conventional liquid cooling to create a hybrid “thermal bus” to move the thermal energy from the heat source(s) to the ambient surroundings. The innovative design can transfer heat between the separated heat source(s) and heat sink(s) without sensitivity to gravity. A case study examines the thermal stability, heat dissipation capabilities, power requirements, and system weights for several driving cycles. Representative numerical results show that the HTC materials and carbon fibers offer moderate cooling while loop heat pipes provide significant improvements for passive cooling.

Construction vehicles own some inherent characteristics, such as low velocity, high power and following heavy heat flux et al. Aiming at decreasing flow resistance and managing airflow, a 39 ton single drum road roller from one of the biggest manufactures in China was employed as a research target to seek out the effect of air flow resistance on the performance of its heat dissipation system. For a start, a simplified 3D model of the road roller in a virtual wind tunnel was established with a commercial software, which was pre-processed in Gambit later. The radiators were set with heat exchanger boundary condition based on the analysis on the air-side elementary unit, as for the cooling fan, the experimental results in the wind tunnel were transformed into the corresponding boundary condition. Following that, a new design scheme was offered to assign the air flow inside the engine cabin, detail flow trajectories of which were introduced by velocity vector and path line acquired from the simulation results in FLUENT. At last, a field experiment was carried out…

Intelligent transportation systems (ITSs) and advanced driver assistance systems (ADASs) are considered as key technologies for improving road safety, fuel economy and driving comfort. For various ITSs and ADASs, e.g. for energy management systems in hybrid electric vehicles and adaptive cruise control systems, the velocity prediction of the ego vehicle and the target vehicles can substantially improve the system performance and is therefore an important building block. In this paper a novel concept for cloud-based vehicle velocity prediction using seasonal autoregressive integrated moving average (SARIMA) processes is proposed. The concept relies on collecting velocity profiles and estimating SARIMA processes using the collected velocity profiles for distinct road segments in a cloud (offboard). When a vehicle enters a road segment, the SARIMA model for the road segment is transmitted from the cloud to the vehicle for velocity prediction (onboard). The actual velocity profiles are transmitted from the vehicle back to the cloud for updating the SARIMA models. For quantifying the prediction uncertainty, an analytical formulation of the prediction bounds is provided. Such an analytical formulation is…