Search Results

Automotive aerodynamic development requires not only to reduce aerodynamic drag but also to develop vehicles that perform well under real road conditions. Although a few types of research have studied the wind characteristics vehicles experienced on-road, the mechanisms of turbulent effects on vehicle aerodynamics are still not well understood. For this reason, an alternative computational fluid dynamics (CFD) method is adopted in this study to reproduce the turbulent wind characteristics, with the aim of providing a more accurate and reliable simulation method to help further understand the wind environment in the atmospheric boundary layer. To fully trust this numerical method, both scale and full-scale simulations are conducted and verified with the corresponding data measured in wind tunnel experiments and on-road measurements.

Comparison of the results of experimental and theoretical investigations of the performance of an air cooled diesel engine with two stage mixing using two injector fuel system and the usual single stage mixing have been presented in this paper. It is shown that two injector fuel system results in an increase of power output by 20-25% on diesel fuel in both the stages and is accompanied only by a moderate rise in cycle peak pressure and exhaust gas temperature. The results of theoretical investigations using mathematical model show that the two stage mixing provides greater controllability of the combustion process through changes in injection characteristic than is possible in the conventional operation. It is concluded that two injector fuel system provides a very simple and reliable method of carrying out two stage mixing in diesel engines.

In-cabin noise induced by tyre air cavity resonance is one of the major issues among other sources. Introducing foam in cavity or changing tyre cavity design is expensive and sometimes they may not solve the problem. Most of the cases the intended techniques are difficult to implement. There are several factors which can affect the tyre cavity resonance. In this work we have studied the effect of acoustic and structural coupling of tyre wheel assembly on tyre cavity resonance. The modal testing of tyre wheel assembly and rim reveals that wheel rim mode affects the tyre cavity resonance. Shifting wheel rim mode away from air cavity mode by using lighter wheel rim reduces the In-cabin noise due to air cavity resonance. Later air cavity resonance mechanism is simulated and verified with the modal test results. In-cabin noise due to air cavity resonance can be optimized by means of using this validated numerical simulation method in the early design stage of tyre development.

Over the last few years, the Electric Vehicle Market (EV’s) has experienced significant growth. One of the major challenges faced by electric vehicles is its tyre performance requirements. Reduced range, Increased vehicle weight, higher motor torque and absence of engine needs lower rolling resistance, higher load capacity, low tread wear & low noise tyre, respectively. All these demands will lower the ride comfort performance of the Electric Vehicle. The objective of this work is to investigate the impact of tyre parameters on the ride comfort performance of EV’s. Tyre construction, tread compound and tyre pressure have a significant impact on the ride comfort performance. Tests like drive point mobility, modal analysis and cleat test are conducted experimentally as well as using virtual tools, the ride comfort performance of tyres is evaluated. The results show that tyre construction and inflation pressure have major influence on the ride comfort performance of EV tyres.

The urgent need to combat global warming has spurred legislative efforts within the transport sector to transition away from fossil fuels. Hydrogen is increasingly being utilised as a green energy vector, which can aid the decarbonisation of transport, including internal combustion engines. Computational fluid dynamics (CFD) is widely used as a tool to study and optimise combustion systems especially in combination with new fuels like hydrogen. Since the behaviour of the injection event significantly impacts combustion and emissions formation especially in direct injection applications, the accurate modelling of H2 injection is imperative for effective design of hydrogen combustion systems. This work aims to evaluate unsteady Reynolds-Averaged Navier Stokes (URANS) modelling of the advective transport process and related numerical methods.

The sampling protocol proposed by the international PMP program for determination of particle emissions from clean light-duty vehicles was applied to the emissions from a California heavy-duty trap-equipped diesel truck. CARB is interested in developing opinions about the potential of this new European approach for emission determination and in exploring its utility for use in California. In this exercise, the use of various commercially available instruments for counting and sizing particles in the context of the PMP recommendations are explored. A single vehicle on a chassis dynamometer was exercised over steady-state and transient cycles. Multiple measurements of gaseous, mass, and particle emissions were collected in order to determine statistical significance. The PMP approach yielded particle emission measurements with higher precision and accuracy than the reference mass-based emission measurement.

Direct measurement of dilution air volume in a Constant Volume emission sampling system may be used to calculate tailpipe exhaust volume, and the total dilution ratio in the CVS. A Remote Mixing Tee (RMT) often includes a subsonic venturi (SSV) flowmeter in series with the dilution air duct. The venturi meter results in a flow restriction and significant pressure drop in the dilution air pipe. An ultrasonic flow meter for a similar dilution air volume offers little flow restriction and negligible pressure drop in the air duct. In this investigation, an ultrasonic flow meter (UFM) replaces the subsonic venturi in a Remote Mixing Tee. The measurement uncertainty and accuracy of the UFM is determined by comparing the real time flow rates and integrated total dilution air volume from the UFM and the dilution air SSV in the RMT. Vehicle tests include FTP and NEDC test cycles with a 3.8L V6 reference vehicle.

The Selective Catalytic Reduction (SCR) is the main after-treatment solution for high efficient diesel engines under development to cope with future lower fuel consumption and NOx emissions requirements (EU6+ legislation). Exhaust gas temperatures are decreasing too, leading to new after-treatment system developments in a close coupled position. Nevertheless before all vehicle architectures allow it, SCR systems are and will still be installed in underbody position. The current paper deals with an underbody metal SCR after-treatment systems, which is capable of active thermal management, and an ultra-compact SCR dosing system. These technologies are described and emission results obtained on several application examples (from passenger cars to light duty commercial vehicles) are presented and discussed in conjunction with an effective active thermal management of the SCR function.

A total of eight low-speed, rear-end impact tests using two Post Mortem Human Subjects (PMHS) in a seated posture are reported. These tests were conducted using a HYGE-style mini-sled. Two test conditions were employed: 8 kph without a headrestraint or 16 kph with a headrestraint. Upper-body kinematics were captured for each test using a combination of transducers and high-speed video. A 3-2-2-2-accelerometer package was used to measure the generalized 3D kinematics of both the head and pelvis. An angular rate sensor and two single-axis linear accelerometers were used to measure angular speed, angular acceleration, and linear acceleration of T1 in the sagittal plane. Two high-speed video cameras were used to track targets rigidly attached to the head, T1, and pelvis. The cervical spine kinematics were captured with a high-speed, biplane x-ray system by tracking radiopaque markers implanted into each cervical vertebra.

With increasing applications of urea SCR for NOx emission reduction, improving the system performance and durability has become a high priority. A typical urea SCR system includes a urea injector, injector housing, mixer, and appropriate pipe configurations to allow continuous urea injection into the exhaust stream and evaporation of urea solution into gaseous products. Continuous operation at various conditions with high NOx reduction is possible, but one problem that threatens the life and performance of these systems is urea deposit. When urea or its byproducts become deposited on the inner surfaces of the system including walls, mixers, injector housings and substrates it can create concerns of backpressure and material deteriorations. In addition, deposits as a waste of reagents can negatively affect engine operation, emissions performance and DEF economy. Urea deposit behavior is explored in terms of heat transfer, pipe geometry, injector layout and mixing mechanisms.

Ideally, complete decomposition of urea should produce only two products in active Selective Catalytic Reduction (SCR) systems: ammonia and carbon dioxide. In reality, urea decomposition reaction is a two-step process that includes the formation of ammonia and isocyanic acid as intermediate products via thermolysis. Being highly reactive, isocyanic acid can initiate the formation of larger molecular weight compounds such as cyanuric acid (CYN), biuret (BIU), melamine (MEL), ammeline (AML), ammelide (AMD), and dicyandimide (DICY). These compounds can be responsible for the formation of deposits on the walls of the decomposition reactor in urea SCR systems. Composition of these deposits varies with temperature exposure, and under certain conditions can create oligomers that are difficult to remove from exhaust pipes. Deposits can affect efficiency of the urea decomposition, and if large enough, can inhibit the exhaust flow and negatively impact ammonia distribution on the SCR catalyst.

Ideally, complete thermal decomposition of urea should produce only two products in active Selective Catalytic Reduction (SCR) systems: ammonia and carbon dioxide. In reality, urea thermal decomposition reaction includes the formation of isocyanic acid as an intermediate product. Being highly reactive, isocyanic acid can initiate the formation of larger molecular weight compounds such as cyanuric acid, biuret, melamine, ammeline, ammelide, and dicyandimide [1,2,3,4]. These compounds can be responsible for the formation of deposits on the walls of the decomposition reactor in urea SCR systems. Composition of these deposits varies with temperature exposure, and under certain conditions, can create oligomers such as melam, melem, and melon [5, 6] that are difficult to remove from exhaust systems. Deposits can affect the efficiency of the urea decomposition, and if large enough, can inhibit the exhaust flow.

An extensive set of data is acquired during engine testing, which is then utilized to evaluate the engine performance characteristics. When engine modifications are carried out in order to improve performance, the whole testing process needs to be repeated. Artificial intelligence-based prediction models can be utilized to reduce the repetitions in engine testing. The data gathered during testing aids in the development of a prediction model that can estimate expected test results with a minimum number of trials. The objective of this study is to predict the in-cylinder pressure of a diesel engine based on the crank angle and load using a model built using artificial neural networks (ANN) in machine learning with MATLAB. ANN prediction model is developed from the data gathered from testing a single-cylinder diesel engine. In ANN, the back propagation algorithm is used to develop the prediction model, which is then validated and compared to the real test data.

Heavy-Duty (HD) diesel engines fulfill the current NOx limits by a sophisticated combination of in-cylinder technologies and an aftertreatment system. In the face of current testing cycles with low average load and efficiency/CO₂ demands measures for the provision of an adequate exhaust temperature become a development core. An alternative to common exhaust management strategies could be variable valve actuation (VVA). Hence a self-developed camless valve actuation system was implemented on a single-cylinder research engine to investigate potential strategies. As these investigations require an appropriate test bench setup the paper consists of two parts. The first part describes the design process of the test bench and focuses on the Rapid Prototyping Systems (RPS) that enabled its operation. The second part discusses the results of different VVA-based exhaust management strategies and gives an outlook to further investigations.

Transient operation is frequently used by vehicle engines and the exhaust emissions from the engine are mostly higher than those under the steady station. An experimental study has been conducted to investigate the effect of various valve timings and spark timings on combustion characteristics and particle emissions from a modern 3.0-liter Gasoline Direct Injection (GDI) passenger car engine. The transient condition was simulated by load increase from 5% to 15% at a constant engine speed with different settings of valve timings and spark timings. The transient particle emission measurement was carried out by a Cambustion DMS500 particulate analyser. The combustion characteristics of the engine during transient operation including cycle-by-cycle combustion variations were analyzed. The time-resolved particle number, particulate mass and particle size distribution were compared and analyzed between different engine settings.

Controlled Auto Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), is one of the most promising combustion technologies to reduce the fuel consumption and NOx emissions. In order to take advantage of the inherent ability to retain a large and varied amount of residual at part-load condition and its potential to achieve extreme engine downsizing of a poppet valve engine running in the 2-stroke cycle, a single cylinder 4-valves camless direct injection gasoline engine has been developed and employed to investigate the CAI combustion process in the 2-stroke cycle mode. The CAI combustion is initiated by trapped residual gases from the adjustable scavenging process enabled by the variable intake and exhaust valve timings. In addition, the boosted intake air is used to provide the in-cylinder air/fuel mixture for maximum combustion efficiency.

The main objectives this paper is two-fold. First, the paper highlights the role of good road and traffic infrastructure for improving the on-road fuel economy of vehicle. Second, it investigate the dynamic driving parameters like positive tractive power level, modes of driving and velocity acceleration envelopes, affecting the on road energy demand and fuel economy. In this study, the gasoline passenger car was driven about 260 km each on two different intercity highways by same driver and at same load. The road and traffic condition of two highways was chosen entirely different, one highway as well organized and other as poorly organized. The fuel consumption and speed time trace were captured using on-board equipments in the field run. The average on road fuel economy was observed as 16.65 km/l (around 18% higher) for well organized highway as compared to 14.13 km/l for other highway.

Recently, several bus systems whose routes are determined by passenger demands transmitted from bus stops have proven to be failures. The paper records efforts to compare the efficiency and degree of success of the various systems. The paper describes the organization of one such system ("Cosby"). The heart of the system is a computer which continually updates bus routes according to passenger demands; these route changes are then transmitted to the bus drivers. The advantages of this system are compared to those of conventional bus systems; in general, the demand-controlled buses can respond to varying amounts of passengers more economically, while conventional buses operate most efficiently with high passenger traffic. This conclusion leads to a description of combinations of demand-controlled and conventional buses. A subsequent simulation of bus lines has demonstrated the potential advantages of such a system.

The characteristics of suspension elastic elements (i.e., spring, damper and anti-roll bar) are directly related to the handling and ride comfort performances, how to tune the characteristics of suspensions' elastic elements is always a big issue in developing the chassis of a vehicle. In this paper, a multi-body dynamics model of a passenger car within MSC.ADAMS® is integrated with iSight FD®, an optimization tool, to carry out a multi-objective optimization for improving the behavior of vehicle handling and ride comfort. The characteristics of suspension elastic elements (i.e., spring, damper and anti-roll bar) are considered as design variables. For handling, the objectives are defined by the measurements from multi-body dynamics simulation of typical double lane change according to ISO3888 standard. For ride comfort, the frequency-weighted RMS (Root Mean Square) value of vertical acceleration of the front seat rail according to ISO2631 standard is set as the objective.