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The current study introduces a Variable Valve Timing (VVT) trapezoidal rotary valve for a 4-stroke spark-ignition engine. Being trapezoidal, enables the rotary valve to change the inlet and exhaust timing continuously, therefore allowing it to control the engine load without the need for a throttle valve. The geometry of the valve is studied in detail, calculating the intersection areas between the windows (ports) of the valve and those of the combustion chamber during the engine cycle. As the valve openings are trapezoidal and the opening of the combustion chamber is trapezoidal as well, there is a multitude of geometry variables that need to be optimized. During idle the engine needs to breathe through just a very small area, while during high load operation the opening needs to be generous. Finally, the trapezoidal rotary valve system is compared to a conventional VVT system.

Over-expansion is one of the promising strategies for improving Internal combustion engine (ICE) efficiency and emissions. It can be implemented by using an unconventional crankshaft. These mechanisms have mass production potential and acceptable friction losses, but also a complex kinematic and dynamic behaviour. This paper proposes such a crank design, a small planetary hypotrochoid over-expanded single cylinder engine - UMotor - and compares it to equivalent conventional ICEs with similar intake or expansion strokes. A suitable crankshaft counter weight geometry was determined in order to minimize the overall reaction forces. The mass balancing studies were conducted via a dynamic motion analysis of the crank drive, including a Fast Fourier Transform (FFT) frequency analysis. For the tested engine speeds, the UMotor average and peak magnitude reaction forces proved to be similar to those generated in the conventional engines for intermediate and high engine speeds.

This paper describes predictive models and validation experiments used to quantify the in-chamber heat transfer of LiquidPiston’s rotary 70cc SI “XMv3” engine. The XMv3 engine is air cooled, with separate cooling flow paths for the stationary parts and the rotor. The heat transfer rate to the stationary parts was measured by thermal energy balance of that circuit’s cooling air. However, because the rotor’s cooling air mixes internally with the engine’s exhaust gas, a similar procedure was not practical for the rotor circuit. Instead, a CONVERGE CFD model was developed, and used together with GT-POWER to derive boundary conditions to estimate a ratio between rotor and stationary parts heat transfer, thus allowing estimation of rotor and total heat losses. For both cases studied (5000 and 9000 rpm under full load), the rotor’s heat loss was found to be ∼60% that of the stationary parts, and overall heat losses were less than 35% of supplied fuel energy.

One way to increase efficiency and performance of 2-stroke engines is the addition of an exhaust valve to control the opening/closure of the exhaust port. With this implementation it is possible to change the exhaust timing for different conditions. However, conventional systems cannot change the exhaust opening and closure timings independently. The work herein presented shows the development of a new exhaust rotary valve enabling the control of the opening independently from the control of the closure of the exhaust port. The study is based on kinetic and thermodynamic analysis. Some manufacturers use exhaust rotary valves but none of them performs a fully rotary motion. This kind of motion has various benefits such as smoothness and most notably the ability to control both the opening and the closure timing of the exhaust independently. Regarding the kinematic analysis, a simple model was created to determine the most suitable valve angles.

The main source for the estimation of stiffness coefficients to be used in accident reconstruction calculations is a very large database of crash-test related information from NHTSA. However, that database includes only car models sold in the USA. Unfortunately, there is no such information for European-only cars besides the raw video recordings of EuroNCAP crash tests. In the present work a methodology is proposed to estimate the stiffness coefficients of European-only models from video images of EuroNCAP crash tests. However, these images are intricate to assess, because the car front is crushed into a deformable barrier at 40% of the front width and usually the bonnet (hood) hides most of the crash damage. Therefore, the top images could not be used straightforward, so a procedure was envisaged to circumvent this difficulty and still allow to calculate stiffness coefficients for European-only cars.

Increasingly stringent targets on energy efficiency and emissions, as well as growing vehicle electrification are making attractive the electric recovery of the energy normally wasted through the tailpipe of Internal Combustion Engines. Recent developments in thermoelectrics (TE) may soon make them a viable solution for such applications [1]. This team has been exploring the potential of using TE modules in combination with variable conductance heat pipes for transferring the exhaust heat to the generator with very low thermal resistance and at a constant, prescribed temperature. This passive temperature control eliminates the need for by-pass systems in the event of temperature overshoots. The operating temperature of a generator should be as high as possible in order to maximize the Seebeck effect. However, currently available modules are temperature limited.

Biodiesel is becoming a common propulsion fuel, as various countries around the world add it to mineral diesel oil, usually as B2 or B5. In low percentages there is no major difference to diesel fuel in terms of power delivered and emissions, but as the percentage rises some alterations are evident on the engine output. These alterations depend on the type of engine, being different from engine to engine. Two Ford Ranger PickUps were used in this study. The diesel engines were different, one a high compression ratio with an old pump-distributer fuel injection system and the other using a common rail system were tested with 5%, 50% and 100% biodiesel-diesel blends on a rolling road dynamometer. The control system of the engines was stock, with no alterations for the various blends. The results show the expected trend in terms of power and emissions, but the differences between the engines display interesting results that can be traced to the differences in engine specifications.

The amount of energy wasted through the exhaust of an Internal Combustion Engine (ICE) vehicle is roughly the same as the mechanical power output of the engine. The high temperature of these gases (up to 1000°C) makes them intrinsically apt for energy recovery. The gains in efficiency for the vehicle could be relevant, even if a small percentage of this waste energy could be regenerated into electric power and used to charge the battery pack of a Hybrid or Extended Range Electric Vehicle, or prevent the actuation of a conventional vehicle's alternator. This may be achieved by the use of thermodynamic cycles, such as Stirling engines or Organic Rankine Cycles (ORC). However, these systems are difficult to downsize to the power levels typical of light-vehicle exhaust systems and are usually bulky. The direct conversion of thermal energy into electricity, using Thermoelectric Generators (TEG) is very attractive in terms of minimal complexity.

Currently, a great deal of the automotive industry's R&D effort is focused on improving overall vehicle environmental and energy efficiency [1]. For instance, one of the things that Electric Vehicles (EVs) and Hybrid cars (HEV) have in common is the recovery of waste energy, namely during braking. But, when an I.C. engine is operating (e. g. as a range extender in an EV), a large amount of energy is also wasted within the exhaust gases and with engine cooling, energy that could otherwise be recovered by different methods. This paper reports on the recovery of waste thermal energy using thermoelectric generators (TEG) for application in hybrid, extended range electric vehicles and more generally in any vehicle that could benefit from the generation of a small amount of electric current that would reduce the alternator operation time.

Since the late 19th century until recently several electric vehicles have been designed, manufactured and used throughout the world. Some were just prototypes, others were concept cars, others were just special purpose vehicles and lately, a considerable number of general purpose cars has been produced and commercialized. Since the mid nineties the transportation sector emissions are being increasingly regulated and the dependency on oil and its price fluctuations originated an increasing interest on electric vehicles (EV). A wide research was made on existing electric/hybrid vehicle models. Some of these vehicles were just in the design phase, but most reached the prototype or full market production. They were divided into several types, such as NEVs, prototypes, concept cars, and full homologated production cars. For each type of vehicle model a technical historic analysis was made.

One of the ways to improve thermodynamic efficiency of Spark Ignition engines is by the optimisation of valve timing and lift and compression ratio. The throttleless engine and the Miller cycle engine are proven concepts for efficiency improvements of such engines. This paper reports on an engine with variable valve timing (VVT) and variable compression ratio (VCR) in order to fulfill such an enhancement of efficiency. Engine load is controlled by the valve opening period (enabling throttleless operation and Miller cycle), while the variable compression ratio keeps the efficiency high throughout all speed and load conditions. A computer model is used to simulate such an engine and evaluate its improvement potential, while a single cylinder engine demonstrates these results. The same base engine was run on the test bench under the Diesel cycle, Otto cycle and Miller cycle conditions, enabling direct thermodynamic comparisons under a wide variety of conditions of speed and load.

Spark ignition engines have low efficiency when working at part and light loads. This can be opposed by using a slightly different thermodynamic cycle known as Miller cycle. This cycle can be implemented in conventional engines if they are equipped with systems providing variable valve timing and variable compression ratio. A computer model to simulate internal combustion engines is used to generate and characterize in terms of torque and brake specific fuel consumption, both Otto cycle engines and Miller cycles engines with VCR. These engines are used in a second computer model to generate the European driving cycle, using the same car and the same gear box, in order to evaluate its performance in terms of fuel consumption. Different ratios for gear boxes using the Miller cycle are proposed in order to achieve a more efficient car (engine, gear box, structure), with less fuel consumption and less green house gas emissions for the urban driving operation.

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 developed in this paper, together with equations for the Otto cycle, diesel cycle and dual cycle, all at part load, so they can be compared. Furthermore, indicated cycle thermodynamical comparisons of a S.I. engine at part load (Otto cycle at half load), a S.I. engine at WOT (with half displacement) and two over-expanded S.I. engines (with different compression strokes) are examined and compared, with the aim of extending the referred theoretical cycle comparisons.

Few diesel vehicles engines from Czech production have been converted into gas (LPG, CNG) fuelled SI engines. The higher power engines (peMAX > 1 MPa) used the concept λ »1 in turbocharging-intercooler and with oxidation catalysts mode with total (max) efficiency of about 38%. For lower power engines (peMAX < 1 MPa) the more suitable concept was using λ=1 in naturally aspirated (atmospheric) mode with 3-way catalysts. Most of the work included the development of the engines to work on Natural Gas (CNG) and LPG for buses and medium trucks. Some laboratory tests were done also with Hydrogen and Natural Gas on the laboratory single-cylinder engine. The measurements consists of standard emissions (CO, HC, NOx, CO2, PM) but Polycycle Aromatic Hydrocarbons (PAH and their carcinogenic derivatives PAHcarc) were also investigated. Combustion stability was assessed by means of Coefficient of MIP (indicated mean effective pressure) Variation (VARpi) for lean and very lean gas fuelled engines.