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As is known, internal combustion engines based on Otto or Diesel cycles cannot complete the expansion process of the gas inside the cylinder, thus losing a relevant energy content, in the order of 30% of total. The residual energy of the unexpanded gas has been partially exploited through the use of an exhaust gas turbine for turbocharging the internal combustion engine; further attempts have been made with several compound solutions, with an electric generator connected to the turbocharger allowing to convert into electrical energy the quota power produced by the turbine which is not used by the compressor, or with a second turbine downstream the first to increase the exhaust gas energy recovery. Turbo-compound solutions were also employed in large marine Diesel engines, where the second turbine downstream the first was used to deliver more power to the main propeller shaft. In all these cases the overall efficiency increments remained within 5%.

Market trends for increased engine power and more electrical energy on the powergrid (3kW+), along with customer demands for fuel consumption improvements and emissions reduction, are driving requirements for component electrification, including turbochargers. GTDI engines waste significant exhaust enthalpy; even at moderate loads the WG (Wastegate) starts to open to regulate the turbine power. This action is required to reduce EBP (Exhaust Back Pressure). Another factor is catalyst protection, where the emissions device is placed downstream turbine. Lambda enrichment or over-fueling is used to perform this. However, the turbine has a temperature drop across it when used for energy recovery. Since catalyst performance is critical for emissions, the only reasonable location for an additional device is downstream of it. This is a challenge for any additional energy recovery, but a smaller turbine is a design requirement, optimized to operate at lower pressure ratios.

A powerful and efficient turbocharger turbine benefits the engine in many aspects, such as better transient response, lower NOx emissions and better fuel economy. The turbine performance can be further improved by employing secondary flow injection through an injector over the shroud section. A secondary flow injection system can be integrated with a conventional turbine without affecting its original design parameters, including the rotor, volute, and back disk. In this study, a secondary flow injection system has been developed to fit for an asymmetric twin-scroll turbocharger turbine, which was designed for a 6-cylinder heavy-duty diesel engine, aiming at improving the vehicle’s performance at 1100 rpm under full-loading conditions. The shape of the flow injector is similar to a single-entry volute but can produce the flow angle in both circumferential and meridional directions when the flow leaves the injector and enters the shroud cavity.

The technologies which comprise heat insulated turbo compound engine are summarized as (1) establishment of heat insulation structure. (2) improvement of combustion under high temperature ambient condition. (3) establishment of energy recovering from exhaust gas.

A new practical concept for piston compounding engines is described. The calculated thermal efficiency of a fully insulated, piston compounded, overcharged diesel engine can exceed 60%. The design considerations for construction of such an engine from controlled expansion superalloys is also described.

This paper discusses the design and control of a two-stage electro-hydraulic camless Variable Valve Actuation (VVA) system designed for gasoline engines that encompass a wide rpm range. The VVA portion of each engine valve assembly in the system consists of two miniature pilot valves, a proportional valve, a compound engine valve actuator and an engine valve return mechanism. The design and proper control of these devices allow for variable valve timing, lift, duration, seating velocity and flank velocity. This flexibility enables an array of combustion strategies. Many of these strategies (such as Miller cycle operation, cylinder and valve deactivation, etc.) have been tested on fired engines that have been redesigned to incorporate the VVA system. Test results for both bench and fired engines running in a dynamometer cell are presented. These results indicate the current level of controllability of the system and the power consumed by the system in a variety of test conditions.

Mass-production single-cylinder engines are generally not turbocharged due to pulsated exhaust flow. Hence, about one-third of the fuel chemical energy is wasted in the engine exhaust. To extract the exhaust energy and boost the single-cylinder engines, a novel supercharging with a turbo-compounding strategy is proposed in the present work, wherein an impulse turbine extracts energy from the pulsated exhaust gas flow. Employing an impulse turbine for a vehicular application, especially on a single-cylinder engine, has never been commercially attempted. Hence, the design of the impulse turbine assumes higher importance. A nozzle, designed as a stator part of the impulse turbine and placed at the exhaust port to accelerate the flow velocity, was included as part of the layout in the present work. The layout was analyzed using the commercial software AVL BOOST. Different nozzle exit diameters were considered to analyze their effect on the exhaust back pressure and engine performance.

Single-cylinder engines in mass production are generally not turbocharged due to the pulsated and intermittent exhaust gas flow into the turbocharger and the phase lag between the intake and exhaust stroke. The present work proposes a novel approach of decoupling the turbine and the compressor and coupling them separately to the engine to address these limitations. An impulse turbine is chosen for this application to extract energy during the pulsated exhaust flow. Commercially available AVL BOOST software was used to estimate the overall engine performance improvement of the proposed novel approach compared to the base naturally aspirated (NA) engine. Two different impulse turbine layouts were analyzed, one without an exhaust plenum and the second layout having an exhaust plenum before the power turbine. The merits and limitations of both layouts are compared in the present study.

The efficiency of Hybrid Electric Vehicles (HEVs) may be substantially increased if the unexpanded exhaust gas energy is efficiently recovered and employed for vehicle propulsion. This can be accomplished employing a properly designed exhaust gas turbine connected to a suitable generator whose output electric energy is stored in the vehicle storage system; a new hybrid propulsion system is hence delineated, where the power delivered by the main engine is combined to the power produced by the exhaust gas turbo-generator: previous studies, carried out under some simplifying assumptions, showed potential vehicle efficiency increments up to 15% with respect to a traditional turbocharged engine. Given the power target of the required exhaust gas turbo-generator, no commercial or reference product could be considered: on account of this, in the preliminary evaluations, the turbine efficiency was assumed constant.

A laboratory scale simulation test method was developed to evaluate deterioration of radial lip seals of fluoroelastomer (FKM) compounds for engine crankshafts. The investigation of the collected radial lip seals of FKM compounds from the field with service up to 450,000km indicated that the only symptom of deterioration is a decrease of lip interference. This deterioration was not duplicated under conventional test conditions using an oil seal test machine because sludge build up at the seal lip caused oil leakage. However, revised test conditions make it possible to duplicate the deterioration experienced in the field. An immersion test using a radial lip seal assembled with the mating shaft was newly developed. This test method was found to be useful to evaluate deterioration of radial lip seals using FKM compounds. Oil additives affect the deterioration of lip seal materials significantly. Therefore, immersion tests of four different oils were conducted to evaluate this effect.

The paper is divided into two main parts. In the first part, section 2 and 3, the performance of turbocharged and compounded systems based on a hypothetical 6 cylinder, 8 litre, 4 cycle DI Diesel engine is discussed under two subheadings: a) the comparative performance, at rated conditions of 2200 rev/min of the two types of system operating at boost levels of 3 bar and 5 bar. b) a much more detailed comparison of the two systems over the full speed range, at the same rated levels of boost, with the 3 bar system operating with a single stage turbocharger, and the 5 bar system with a 2 stage turbocharger.

The paper describes further work on the differential compound engine (DCE) which, following earlier theoretical work on the feasibility of multi-variable control is now being converted to microprocessor controlled continuous optimization for minimum fuel consumption for any demanded combination of output shaft conditions. The controlled variables on this integrated compounded engine transmission system include: i) engine governor set point ii) geared turbine nozzle angle iii) engine bypass setting and, additionally, in a system yet to be developed, but already theoretically investigated, fuel injection timing and duration. The paper describes the experimental and analytical procedures, using a programmable high response hydrostatic dynamometer, for establishing the 3-dimensional control surfaces for the above 3 variables, and the subsequent implementation of a microprocessor controlled system.

This paper introduces the development of a new idea in traction prime movers, to be known as the Differential Compound Engine. The DCE contains in addition to the compressor, an exhaust driven turbine geared into the output shaft, which leads to improved power and efficiency. It also enables the engine to operate at unchanged speed and power, regardless of output shaft speed. This concept was designed to provide an integrated engine transmission of high output and with stepless single pedal control.

This paper describes the characteristics of a low-pollution steam engine for the California Steam Bus Demonstration Project. The nature of combustion in an external combustion engine is such that lower levels of exhaust emissions should be expected. To demonstrate the lower exhaust emission level and to show that steam engines are feasible powerplants for automotive applications, a reciprocating-type steam powerplant was designed, built, tested, and installed in an urban bus. The system was designed to provide performance and handling characteristics similar to those initially found in the diesel-powered bus without significantly altering the appearance of the bus or reducing its seating capacity. To accomplish this limited objective for demonstration purposes, all available space, including that under the bus, was utilized for major components. A 3-cyl double-acting compound engine is used to extract work from steam delivered at 800 psia and 850 F.

This paper presents a compound engine concept that has the potential of significantly reducing exhaust emissions. This cycle is based on a combination of components of the spark-ignition engine and the gas turbine. The cycle utilizes a two-stage combustion process involving fuel-rich combustion at high temperatures to reduce NOx formation and followed by lean burning to eliminate unburned hydrocarbons in a thermodynamically productive manner. A thermodynamic analysis of this cycle and a comparison with the conventional otto cycle is presented. The combustion processes involved are examined and methods of implementing this cycle in a practical manner are shown. The results of this analysis indicate that a practical automotive power cycle with excellent part load and transient response characteristics is possible via this approach.

A COMPOUND engine, consisting of a piston engine mechanically connected to a turbine, with the turbine receiving the piston-engine exhaust, is suggested by Mr. Bachle as a method of converting into useful work some of the exhaust-gas energy of both diesel and gasoline engines that is usually wasted. The combination of a gasoline engine compound with gas turbine and driven by a propeller is considered by Mr. Bachle to offer the minimum weight of powerplant plus fuel for long-range aircraft cruising at 300 mph; for short-range cruising at 300 mph, the gas turbine and propeller combination is best, with the gas turbine driven by jet propulsion offering the next best possibilities. Only when higher speeds become more practical, as a result of reduced aircraft drag, does Mr. Bachle believe that piston engines may be replaced by jet-propulsion turbines.

THIS authors sees a need, in the near future, for commercial vehicles with engines of 1000 to 1200 hp - powerplants that yield high outputs but require limited space. He sees an immediate need for more and more horsepower per cubic inch of piston displacement and per unit of space for the engine. He directs attention to six design potentials which may supply the answer: (1) the gas turbine; (2) supercharging; (3) aircooled diesels; (4) higher engine speeds; (5) 2-stroke diesel improvement; (6) compound engines. He also links the future development of the internal-combustion engine with basic improvement of components through simplification, calling for the elimination of extraneous gadgetry.

A staged combustion engine has been evaluated in which pairs of cylinders are coupled in series. The first cylinder of the pair inducts and burns a homogeneous, fuel-rich mixture which produces exhaust products containing substantial amounts of combustibles (CO, H2, and HC) and only small quantities of NOX. These products are then cooled, mixed with additional air, and inducted into another cylinder for a second stage of combustion. Additional work is extracted in this second stage, where substantial cleanup of CO and HC occurs while maintaining a low level of NOX. Experiments with a two-cylinder research engine showed that low NOX emission could be obtained without sacrificing engine efficiency. However, approximately 40 percent more displacement is required to produce the same power as conventional SI engines. The sources of HC, CO, and NOX emissions were investigated, as were the effects of major engine variables on these exhaust emissions and fuel consumption.

Comprehensive experimental results obtained with a 4-stroke diesel engine are presented. Development of the differential compound engine in its present form, with flexible, multivariable operating controls, is given in detail. Output shaft torque and power envelopes demonstrate both constant power and implied high torque backup. The possibility of stepless transmissions or, at most, a 2-forward/reverse ratio gearbox, makes the unit particularly attractive for a wide range of transport applications.