Figure 3- - uploaded by Jorge Martins
Content may be subject to copyright.
Source publication
When the exhaust valve of a conventional spark ignition engine opens at the end of the expansion stroke, a large quantity of high pressure exhaust gas is freed to the atmosphere, without using its availability. An engine that could use this lost energy should have a better efficiency. The equations for an over-expanded cycle (Miller cycle) are deve...
Context in source publication
Similar publications
In this document a very detailed hybrid model of a spark ignition engine in idle condition is provided. The model collects the non–linear intake manifold dynamics, the cyclic cylinders behavior, the clutch, the spark–ignition coil, the throttle valve and sensors dynamics. In particular, the hybrid dynamics of each cylinder captures the thermodynami...
Citations
... Due to the GENERATOR I BATTERY + MOTOR DRIVE Figure 9: An ER-SES confguration block diagram. Low 73% [139] 78% [138] 77% [137] ER-fuel cell 500 km [141] 650 km [142] 665 km [144] 594 km [144] 1500 km [146] 20 Low 20-40% [147,148] 31% [77] lack of chemical reactions, a supercapacitor has a greater power density than a battery by charging its electrodes [168]. Supercapacitor is most suitable for fast charging and discharging applications due to its inherent characteristics, high efciency, and low internal resistance than the battery [169]. ...
Transportation is the leading source of logistics, and people contribute the signifcant primary emissions for increasing global warming, so we should avoid such a situation and concentrate on zero emissions. Te range of the vehicle is the major problem (range-anxiety) in electric vehicles. Nowadays, researchers focus on range extender optimization since range extenders sig-nifcantly improve the range of the vehicle with an auxiliary power unit (APU), which can prove consumer satisfaction. However, range extenders can recover energy by proposing the various confgurations and systems of extended-range electric vehicles (EREV). Many industries and researchers summarize these eforts to optimize and fnd the solution for range-extenders. Tis paper reviewed the most suitable technologies for energy recovery and state-of-the-art topological constructions. Te analysis of the study primarily concentrated on optimizing the cost of the systems, fewer emissions, and more fuel economy. Te research is based on the range-extenders evaluation and summary for electric vehicles to guide automakers and researchers to invent other state-of-the-art confgurations and topologies to obtain optimized EV ranges, namely, enhanced functionality and fewer emissions. A survey on specifc extend-range electric vehicles and classifcation of EREV technologies, the performance of APUs, diferent control strategies of energy management in EREVs, and various existing difculties are discussed and further enhanced for the future researcher EREV forecast ofered by advanced technologies.
... Furthermore, a long expansion stroke increases the cylinder body length and weight, piston friction loss, and exhaust pumping loss. Despite this, the over-expansion cycle can able to provide higher partial load efficiency, and for the same efficiency, it is equivalent about 25:1 compression ratio of conventional diesel and dual cycles [15]. Liu et al. [16] reported that Atkinson cycle provides low heat loss, relatively longer expansion stroke, and 4.5% improvement in indicated thermal efficiency over the prototype. ...
... Figure 15 shows the comparative value of CO in V% and NO in ppm between non-OE and with OE at exhaust valve open for the maximum BMEP spark timing. It can be pointed out that for both the non-OE and OE, the CO and 15 Comparative NO and CO exhaust emission at EVO between over-expanded and non-over-expanded stroke engine at maximum BMEP spark timing NO concentration increases with the increment of engine rpm. The NO formation mainly depends on the availability of oxygen and combustion flame temperature inside the cylinder. ...
Improvement in fuel conversion efficiency in an internal combustion engine increases power and reduces fuel consumption. The efficiency of an engine increases either by the increase in compression ratio or expansion ratio. This paper presents a new concept for a higher expansion process in comparison to compression process stroke on the base of the Miller cycle, rather than early or late closing inlet valves. The proposed mechanism works with eccentric crankshaft movement around the eccentric-derived path to achieve a shorter compression process and longer over-expansion process stroke. The theoretical simulation results of SI engine were obtained using thermodynamic quasi-dimensional combustion (burned and unburned zone) power cycle integrated with the intake and exhaust system. The best result of over-expansion (OE) system over non-OE has been observed at 1500–2000 rpm, and the corresponding results are: increment in indicated thermal efficiency from 36 to 38.5%, brake torque from 32 to 46 N-m, brake power from 6.52 to 9.46 kW and indicated power from 7.36 to 10.89 kW, and maximum BSFC decrement 5.42% at 1500 rpm. OE system has a higher value of CO concentration throughout the speed range; however, the NO concentration in ppm decreased by 1.62% at 1500 rpm at the same EVO crank angle. Thus, this mechanism offers significant benefits in thermal efficiency, fuel consumption, and NO emission. And, it is highly beneficial at 1500–2000 rpm engine run, which shows most suitable for engine-integrated electric power generation.
... Therefore, Miller cycle is a very promising strategy in modern advanced SI engine. Subsequently, the quasi-dimensional model [38], one-dimensional (1D) model [39] and three-dimensional model [40] were used to comprehensively investigate the performance behavior of the Miller cycle engine. Gonca et al. [41] systematically studied the effects of the engine design and operating parameters on the performance of the turbocharged Miller cycle engine by adopting the finite-time thermodynamics model. ...
In order to further improve thermal efficiency and fuel economy, the engine community pays more attention to the advanced controlling strategy. In this paper, the impacts of the continuous variable valve lift (CVVL) system and Miller cycle strategy on the performance behavior of the natural gas spark ignition (SI) engine were comprehensively investigated. The results indicated that pumping loss was decreased, and volumetric efficiency slightly increased with using CVVL. In addition, the intake air mass flow at the intake ports became more smooth, and turbulence flow and its intensity were strengthened with using CVVL, which were beneficial to accelerate combustion rate and improve combustion efficiency. Under the partial load of the 1200 rpm 5 bar, the ratio of the pumping mean effective pressure (PMEP) in indicated mean effective pressure (IMEP) was reduced by 2.74%. Furthermore, an extra 5.43% improvement of indicated thermal efficiency was obtained. On the other hand, peak in-cylinder pressure and peak combustion temperature of the natural gas SI engine operated on Miller cycle were decreased with late intake valve close (LIVC), particularly the pressure and temperature at the end of the compression stroke, which resulted in reducing NOx emissions formation and mitigating knocking combustion. However, the intake mass flow at the intake ports became fluctuation and the volumetric efficiency was decreased with using LIVC. In addition, brake specific fuel consumption was increased and indicated thermal efficiency decreased with employing LIVC.
... Internal combustion engines play a very important role in reducing emissions and saving energy. Vehicle manufacturers, research and development centers and scientists have been working on internal combustion engines to improve performance, reduce fuel consumption and harmful exhaust emissions using variable valve timing systems, alternative combustion modes and alternative fuels [7][8][9][10][11][12][13][14][15][16]. It is also aimed to increase the performance and efficiency, and decrease emissions by using alternative cycles such as Atkinson and Miller cycles in internal combustion engines [17,18]. ...
In this study, an Otto cycle engine was converted to the Atkinson cycle engine using the method of late intake valve closing and increasing the compression ratio. Firstly, the thermodynamic analysis was conducted. In the analysis, the variation of specific heats with temperature, heat losses, pumping, and mechanical friction losses was taken into account. In-cylinder pressure variations, torque, power, thermal efficiency and brake-specific fuel consumption variations with speed were obtained. For the experimental study, a new camshaft was designed and manufactured using a circular arc curve. The IVC timing of the Atkinson engine was delayed by a 20° crankshaft angle with respect to standard timing. The compression ratio was increased from 8.5 to 9.5. Tests were conducted at 1400–3400 rpm speed range at WOT. Experiments were conducted at three different operating conditions: Otto cycle for the standard engine, late closing of the intake valve at 20 ° CA at 8.5 compression ratio and late closing of the intake valve at 20 ° CA at 9.5 compression ratio. In the tests, the variation of torque, power, BSFC and thermal efficiency with speed were investigated. The results showed that torque, power, BSFC and thermal efficiency were improved with Atkinson CR9.5 operation compared to the standard Otto cycle operation at high speeds. It was obtained that the torque and power of the Atkinson CR9.5 cycle engine increased by 6.7% and the thermal efficiency increased by 12.8% at 3400 rpm speeds. In addition, BSFC of the Atkinson CR9.5 engine decreased by 12.7%.
... Introduction 36 The quest for reducing energy consumption, pollutants and greenhouse-gas (GHG) emissions is one 37 of the main factors affecting the automotive industry research nowadays [1][2][3]. In terms of fuel 38 consumption, the 2020 European Union target equates to approximately 4.1 L/100 km of petrol or 39 3.6 L/100 km of diesel. ...
... step [37]. The engine model is based on steady-state engine maps [10,36]. These models have already 211 been described elsewhere [35] , and included validation with a small prototype [34]. ...
One of the main obstacles for the use of thermoelectric generators (TEGs) in vehicles is the highly variable thermal loads typical of driving cycles. Under these conditions it will be virtually impossible for a conventional heat exchanger to avoid both thermal dilution under low thermal loads and TEG overheating under high thermal loads. The authors have been exploring an original heat exchanger concept able to address the aforementioned problems. It uses a variable conductance thermosiphon-based phase-change buffer between the heat source and the TEGs so that a nearly constant, optimized temperature is obtained regardless of operating conditions. To the best of the authors’ knowledge, the thermal control feature of the system is unique among existing TEG concepts. The novelty of the present work is the actual computation of operating pressure and temperature and the corresponding vaporization and condensation rates inside the thermosiphon system during driving cycles along with the assessment of the influence of the volumes and pre-charge pressure on electrical output. The global energy and emission savings were also computed for a typical yearly driving profile. It was observed that indeed the concept has unparalleled potential for improving the efficiency of vehicles using TEGs, with around 6% fuel and CO2 emissions savings using the system. This seems a breakthrough for such light duty applications since the efficiency of conventional (passive) systems is strongly deprecated by thermal dilution under low thermal loads and the need to by-pass high thermal load events to avoid overheating. On the contrary, the present concept allows the control of the hot face temperature of the TEGs even under highly variable thermal load (i.e. driving cycle) environments.
... The vehicle and engine models predict the required instantaneous engine map position (torque, speed) to fulfil the driving cycle and the corresponding exhaust flow rate and inlet temperature for each time step [37]. The engine model is based on steady-state engine maps [10,36]. These models have already been described elsewhere [35], and included validation with a small prototype [34]. ...
... This may be accomplished simply via the reduction of the intake stroke by anticipating (Early Intake Valve Closure -EIVC) or delaying (Late Intake Valve Closure -LIVC) the closure of the intake valve. As shown in previous works [6,7], this method allows for significant improvements of the thermal efficiency of the theoretical cycle [1]. Nevertheless, it has the disadvantage of reducing the effective engine displacement. ...
... Therefore it would be possible, in principle, to use that enthalpy and produce some mechanical power using a thermal cycle, such as an ORC (Organic Rankine Cycle). With this strategy, a theoretical SI engine with a compression ratio of 12:1 could increase its efficiency from the 63% of the Otto cycle ( Fig. 1) to the 73% of the Atkinson cycle [1] and still improve to 87% using the enthalpy of the exhaust gases. Even with the theoretic Atkinson cycle the gases would exit at 830ºC. ...
Traditional Internal Combustion Engines (ICE), particularly Spark Ignition (SI) engines, have a maximum thermal efficiency which does not usually exceed the 35% mark. Typically, only a third of the energy supplied within the fuel reaches the crankshaft and the other two thirds are, more or less, equally divided between the exhaust heat (enthalpy of the burned gases) and through the engine cooling. Therefore, in order to improve engine efficiency, one should look at these two waste heat sources and try to reduce them as far as possible. By the second law of thermodynamics a thermal engine receives heat from a hot reservoir and looses heat to a cold reservoir. The cold reservoir is the atmosphere and the heat that should be lost is in the form of exhaust gas enthalpy. However, the extent of heat lost within the exhaust gases is much higher than the one required from a second law perspective. In fact, the exhaust gases leave the engine at a temperature much higher than the ambient temperature, so we developed a way to reduce this wasted energy by the use of over-expansion. Other supplementary methods of recovering energy from the hot exhaust gases is by the use of Organic Rankine Cycles (ORC) or using ThermoElectric Generators (TEG), which are devices that can convert directly a portion of the exhaust heat into electricity using the so-called Seebeck effect.
... Correspondingly, the thermal efficiency of the conventional SI gasoline degrades considerably at engine light loads, on account of fixed compression ratios varying from 8 to 12 as well as limitations of fuel quality and engine knocking. Moreover, the authors [30], [31] have derived and explored the thermal efficiencies of several engine cycles and have figured out that the optimum thermal efficiency contributing thermodynamic cycle is the over-expanded cycle (Atkinson cycle). ...
... So, to cater for the SI engine performance degrading behavior, hybrid electric vehicles are using the over-expanded Atkinson cycle engine appreciated through VVT and incorporated with Variable Compression Ratio (VCR) mechanism [31]. About 50% fuel consumption is reduced by HEVs through the Atkinson cycle engine as one of its propulsion system. ...
... The research [34] has figured out that there is around 6% decrease in fuel consumption with VCR Overexpanded engine cycle, using Cylinder by Cylinder Engine Model (CCEM) model in comparison with the Otto cycle engine during the typical new European driving cycle (NEDC). About 19% reduction in specific fuel consumption (SFC) of the VVT along with VCR mechanism built-in Atkinson cycle engine with regards to the usual Otto cycle spark ignition engine [31], [35]. ...
Energy Management Strategies are widely used for the fuel efficiency of Hybrid Electric Vehicle (HEV). Most of the on road Hybrid cars use Atkinson cycle engine instead of Otto cycle engine, on account of better efficiency. The authors have already proposed a control oriented extended mean value engine model (EMVEM) of the Atkinson cycle engine and also developed and evaluated its control framework. The prior research was limited to evaluate the fuel efficiency of the engine only, while HEV employs both the engine and the motor. The presented work is an attempt to devise and demonstrate Energy Management Strategy (EMS) by giving full consideration to the powertrain using Atkinson cycle engine. A novel energy management strategy based on the vehicle speed for Atkinson cycle engine for HEV is proposed. A parallel hybrid electric vehicle is modeled in Matlab/Simulink through a forward facing simulator. The proposed EMS with Atkinson cycle engine control framework exhibits the significant improvement in the fuel economy around 12.30% for standard Manhattan driving cycle and 7.22% for the modified Federal Urban Driving Schedule (FUDS) driving cycle in comparison with the Otto cycle engine.
... Internal combustion engines play a very important role in reducing emissions and saving energy. Vehicle manufacturers, research and development centers and scientists have been working on internal combustion engines to improve performance, reduce fuel consumption and harmful exhaust emissions using variable valve timing systems, alternative combustion modes and alternative fuels [7][8][9][10][11][12][13][14][15][16]. It is also aimed to increase the performance and efficiency, and decrease emissions by using alternative cycles such as Atkinson and Miller cycles in internal combustion engines [17,18]. ...
In this study, a single cylinder, 4-stroke, spark ingition Otto cycle engine was converted to Atkinson cycle and performance variations were investigated. The engine is converted to Atkinson cycle engine via late intake valve closing timing and increasing the compression ratio. Torque, power, thermal efficiency and specific fuel consumption variaitons with engine speed were obtained experimentally at wide open throttle without any modification. Thermodynamic analysis was performed for Otto and Atkinson cycle operation of the engine and the theoretical values were compared with experimental values.
