Browse Topic: Compound engines

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NEW VOLVO D13 VGT utilizes 24V architecture25TOFHP06_026/1/2025
Volvo Trucks North America launches the all-new VNR with standard D13 VGT engine and announces an upcoming CARB- 24 Omnibus compliant engine variant. When Volvo Trucks revealed its all-new VNR regional haul truck in March 2025, it also marked the launch of something new under the hood: the Volvo D13 VGT (variable geometry turbo) engine. The new D13 VGT engine will be standard in the VNR and optional for the VNL day cab. The D13 VGT engine builds on improvements launched with the D13 Turbo Compound engine, which is standard on the new VNL (www.sae.org/news/2024/02/volvo-vnl-launch) that commenced commercial production at the New River Valley assembly plant in Dublin, Virginia, in October 2024.
Gehm, Ryan
Evaluating the Potential of a Turbo-Compound System for a Heavy-Duty Natural Gas Engine: A Modelling Study2025-01-83554/1/2025
Combining a low-carbon content fuel, such as natural gas, with a high-efficiency engine can reduce greenhouse gas emissions significantly in hard-to-electrify long-haul trucking applications. Turbo-compounding, where an additional power turbine is installed in the exhaust stream after the turbocharger turbine, can extract useful amounts of energy from diesel engine exhaust at high loads. This work assesses the net benefits of combining turbo-compounding with a high-efficiency, natural gas fuelled heavy-duty engine. The effects on brake specific fuel consumption (BSFC), greenhouse gas emissions, and engine-out emissions of nitrogen oxides (NOx) and methane (CH4) are considered. The experimentally validated 1D model for a 13L diesel pilot- direct injection of natural gas, heavy-duty engine in GT-SUITETM is used to develop a series turbo-compound model. The effects of turbine sizes and flow capacities in fixed-geometry turbocharging and power turbines are evaluated on the engine’s performance, considering the trade-off between power output in the power turbine and turbo-compound losses because of increased back pressure. A parametric analysis is conducted in the 1D model to select the best combination of turbine sizes and the gear ratio between the power turbine’s shaft and engine’s crankshaft to optimize the rotational speed of the power turbine. The results show that the turbocharging turbine’s size has the most significant effect on BSFC. The model results indicate that the most promising combination of turbines may reduce BSFC by 1% to 4% at high loads within the range of 1000 rpm to 1400 rpm, with even larger reductions of 5% to 6% at the peak power conditions around 1600 rpm. At lower loads (below 40%), the BSFC increased from 1% at mid-load to 6% or more at low loads. The net benefits of the turbo-compound system are evaluated in a developed class-8 truck model in GT-SUITETM over standard long-haul and regional delivery transient drive cycles with different cargo loads. The truck transient simulation results show that fuel consumption was reduced by 2% to 4% in 35% to 100% cargo loads in drive cycles with more cruising time but did not change substantially in lower cargo loads. More benefits in higher cargo loads are attributed to the shifted engine operating points to the higher loads where the turbo-compound system significantly improves engine system efficiency. The truck simulation results also showed that the turbo-compound system did not change the cumulative engine-out NOx and CH4 emissions over the studied drive cycles.
Balazadeh, Navid, Munshi, Sandeep, Shahbakhti, Mahdi, McTaggart-Cowan, Gordon
Turbo Compounding of a Naturally Aspirated Single Cylinder Diesel Engine – A Simulation and Experimental Study2023-01-184510/24/2023
Almost one-third of the fuel energy is wasted into the atmosphere via exhaust gas from an internal combustion engine. Despite several advancements in waste heat recovery technology, single-cylinder engines in the market that are currently in production remain naturally aspirated without any waste heat recovery techniques. Turbocharging is one of the best waste heat recovery techniques. However, a standard turbocharger cannot be employed in the single-cylinder engine due to technical challenges such as pulsated flow conditions at the exhaust, phase lag in the intake and exhaust valve opening. Of late, the emphasis on reducing exhaust emissions has been a primary focus for any internal combustion engine manufacturer, with the onset of stricter emission norms. Thus, the engine designer must prioritize emission reduction without compromising engine performance. Current work focuses on enhancing the power output of a 0.6-litre, single-cylinder naturally aspirated diesel engine by employing a power turbine. Since the exhaust flow conditions were pulsated, an impulse turbine was employed. One-dimensional simulation studies were carried out after validating the base naturally aspirated engine model. An impulse turbine was designed and simulated for the pulsated flow conditions. Simulation results show that the single-cylinder naturally aspirated engine delivered a superior performance with turbo compounding. The brake power output of the turbo-compounded engine improved by 6% compared to the base NA version. Also, the thermal efficiency of the turbo-compounded engine improved by 2%. HC emissions were reduced by 31% and CO emissions by 11% for the turbo-compounded engine. Soot emissions were 2% lower, and NOx emissions were 5% lower for the turbo-compounded engine than the base naturally aspirated engine. Thus, turbo-compounding is an effective waste heat recovery system that improves the performance and reduces exhaust pollutants of a single-cylinder naturally aspirated engine.
Ramkumar, J, Krishnasamy, Anand, Ramesh, A
Direct and Indirect Exhaust Heat Recovery from Turbocharged Heavy-Duty Engine2023-24-01228/28/2023
Waste Heat Recovery (WHR) is one of the most viable opportunities to reduce fuel consumption and CO2 emissions from internal combustion engines in the transportation sector. Hybrid thermal and electrical propulsion systems appear particularly interesting because of the presence of an electric battery that simplifies the management of the electrical energy produced by the recovery system. The different technologies proposed for WHR can be categorized into direct and indirect ones, if the working fluid operating inside the recovery system is the exhaust gas itself or a different one whose sequence of transformations follows a thermodynamic cycle. In this paper, a turbocharged diesel engine (F1C Iveco) equipped with a Variable Geometry Turbine (VGT) has been tested to assess the energy recoverable from the exhaust gases both for direct and indirect recovery. A direct technology based on an auxiliary turbine placed in the exhaust pipe (turbo-compounding) has been considered and compared with an Organic Rankine cycle (ORC)-based recovery unit fed by the exhaust gases. A model-based comparison between the two technologies has been assessed in this paper. The input data were the result of an experimental campaign done on the exhaust gases of the F1C Iveco operated on a high-speed dynamometer test bench. Data on exhaust gas properties, turbocharger equilibrium and engine performances were collected for a wide range of engine operating conditions. Concerning the ORC-based power unit, the model uses the significant research experience done on the sector that set up the most relevant machine performances (expander and pump efficiency, engine backpressure produced, pinch points at the two heat exchangers) so giving the model high reliability. Preliminary data on a turbo-compounding system operated on the same engine were also measured so resolving the most important uncertainties of the recovery unit (engine backpressure produced, turbine and electrical generator efficiency, matching between the turbocharging unit). A preliminary assessment of the overall potential recovery when both technologies were present has been done, focusing the attention on heavy-duty engines.
Di Bartolomeo, Marco, Di Battista, Davide, Fatigati, Fabio, Cau, Giorgio, Cipollone, Roberto
Turbogenerator Transient Energy Recovery Model2023-01-02084/11/2023
Significant exhaust enthalpy is wasted in gasoline turbocharged direct injection (GTDI) engines; even at moderate loads the WG (Wastegate) starts to open. This action is required to reduce EBP (Exhaust Back Pressure). Another factor is catalyst protection, placed downstream turbine. Lambda enrichment is used to perform this. However, the conventional turbine has a temperature drop across it when used for energy recovery. Catalyst performance is critical for emissions, therefore the only location for any additional device is downstream of it. This is a challenge for any additional energy recovery, but a smaller turbine is a design requirement, optimised to work at lower operating pressure ratios. A WAVE model of the 2.0L GTDI engine was adapted to include a TG (Turbogenerator) and TBV (Turbine Bypass Valve) with the TG in a mechanical turbocompounding configuration, calibrated with steady state dynamometer data to estimate drive cycle benefit. The model derived is used in the development of more advanced control system algorithms. Furthermore, transient verification with WAVE-RT in co-simulation is performed on drive cycles (NEDC, WLTP). Analysis includes power and fuel consumption, and an additional knock impact assessment. It is shown on the WLTP that, depending on the calibration, up to 9% FC (Fuel Consumption) reduction is achievable with a 0.03kW thermodynamic power recovery, for a similar controller performance. Hints are given for further controller enhancements. Prototype dynamometer testing or vehicle could be performed to verify design assumptions and simulation results. Electrical turbo-compounding, interfacing to the power-grid, and calibration optimisation, with combined WG and TBV settings is feasible based on this initial work.
Petrovich, Simon, Ebrahimi, Kambiz, Watson, Andrew, Mason, Byron
Realistic Steady State Performance of an Electric Turbo-Compound Engine for Hybrid Propulsion System2022-24-00159/16/2022
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. In this paper instead the authors present the result of new evaluations performed by adequately considering the real efficiency of the exhaust gas turbine, which was designed and calculated by means of simple yet effective 1D approach, and validated by means of 3D CFD analysis. The 1D design and evaluation methodology, characterized by short calculation time, revealed sufficiently accurate compared to the result obtained by the time-consuming CFD simulations; the exhaust gas turbine efficiency was hence calculated for each required operating condition and used to compute the expected real efficiency of the compound engine; as a final result, it was found that, compared to a traditional turbocharged engine of the same rated power (73.5 kW), the realistic compound engine exhibit efficiency increments between 5% and 15%, depending on the output power.
Pipitone, Emiliano, Caltabellotta, Salvatore, Beccari, Stefano, Lanzafame, Rosario, Mauro, Stefano, Brusca, Sebastian
Supercharging with Turbo-Compounding - A Novel Strategy to Boost Single Cylinder Diesel Engines2022-01-11138/30/2022
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. A suitable nozzle exit diameter was chosen based on simulation results. The simulated exit conditions of the nozzle were used as inputs for velocity triangle calculations. Based on these calculations, major design features of the impulse turbine, such as blade speed, nozzle exit diameter and stator exit angle, were established. The key parameters were thus designed for the impulse turbine. The designed impulse turbine resulted in about 91% impulse turbine efficiency at rated power conditions. The proposed layout with the designed impulse turbine delivered 68% higher brake power output and improved the engine efficiency by 9.36% compared to the naturally aspirated stock engine.
Ramkumar, J, Krishnasamy, Anand, Ramesh, A
Investigations on a Novel Supercharging and Impulse Turbo-Compounding of a Single Cylinder Diesel Engine2022-01-11118/30/2022
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. An optimum nozzle area ratio of 50% for the first layout was arrived, which provided better net engine performance with 53.7% higher brake power output and 5.8% higher brake thermal efficiency. The second layout fared better with a nozzle area ratio of 13% and a plenum volume of 1 litre. The second layout delivered 52.8% higher brake power output and 5.5% higher brake thermal efficiency at rated power conditions. Both supercharged configurations produced 1.8 bar (absolute) boost pressure that increased airflow rate by 33% more than the NA configuration. This would improve combustion efficiency and reduce exhaust emission congruent with any charged engine. Thus, the present novel approach with both the layouts benefitted from charging the single-cylinder diesel engine, which was otherwise difficult in conventional turbocharging.
Ramkumar, J, Krishnasamy, Anand, Ramesh, A
Modeling Transient Control of a Turbogenerator on a Drive Cycle2022-01-04153/29/2022
GTDI engines are becoming more efficient, whether individually or part of a HEV (Hybrid Electric Vehicle) powertrain. For the latter, this efficiency manifests itself as increase in zero emissions vehicle mileage. An ideal device for energy recovery is a turbogenerator (TG), and, when placed downstream the conventional turbine, it has minimal impact on catalyst light-off and can be used as a bolt-on aftermarket device. A Ricardo WAVE model of a representative GTDI engine was adapted to include a TG (Turbogenerator) and TBV (Turbine Bypass Valve) with the TG in a mechanical turbocompounding configuration, calibrated using steady state mapping data. This was integrated into a co-simulation environment with a SISO (Single-Input, Single-Output) dynamic controller developed in SIMULINK for the actuator control (with BMEP, manifold air pressure and TG pressure ratio as the controlled variables). Transient verification with WAVE-RT was conducted on WLTP and NEDC drive cycles, estimating dynamic energy recovery and fuel consumption improvement. Hints are given for a more advanced MIMO (Multiple-Input, Multiple-Output) control system architecture and calibration.
Petrovich, Simon, Ebrahimi, Kambiz, Mason, Byron, Watson, Andrew
Investigations on Supercharging and Turbo-Compounding of a Single Cylinder Diesel Engine2022-01-04233/29/2022
Despite the advantages of turbocharging in improved engine performance and reduced exhaust emissions, commercial single-cylinder engines used for automotive applications remain naturally aspirated (NA) and are not generally turbocharged. This is due to the shortcomings with pulsated and intermittent exhaust gas flow into the turbine and the phase lag between the intake and exhaust stroke. In the present study, experimental investigations are initially carried out with a suitable turbocharger closely coupled to a single-cylinder diesel engine. Results indicated that the engine power dropped significantly by 40% for the turbocharged engine compared to the NA version even though the air mass flow rate was increased by at least 1.5 times with turbocharging. A novel approach of decoupling the turbine and the compressor and coupling them separately to the engine is proposed to address these limitations. Also, an impulse turbine is chosen for this application, better suited to extract energy during the pulsated exhaust flow. Commercially available AVL Boost software was used to carry out the simulation studies to understand the improvement in overall engine performance with the proposed novel approach compared to the base naturally aspirated engine. Different nozzle area ratios were analyzed to estimate the kinetic energy available at the nozzle exit. An optimum nozzle area ratio of 1:2 for the impulse turbine was arrived, which provided better net engine performance. The net effect of the supercharged and turbo-compounded engine resulted in an improved performance with 43% higher brake power output and 3% higher brake thermal efficiency at the rated power conditions. Thus, the present approach reaped the benefits of charging the single-cylinder diesel engine, which was otherwise impossible by the conventional turbocharging method.
Ramkumar, J, Krishnasamy, Anand, Ramesh, A
Downsized Boosted Dilute Combustion, Exhaust Compounded (DBDC+EC) Experimental Engine Design, Thermodynamic Model Comparison, and Performance Potential Predictions2021-01-04434/6/2021
An experimental piston compounded engine was designed with guidance from thermodynamic modeling, then was built and tested to compare the model predictions to measured results. The piston-compounded concept has shown great potential for improvements in efficiency over current state-of-the-art light-duty engines through the use of an efficient second expansion process to more fully recover energy still present in the exhaust gasses, and was further developed into the Downsized Boosted Dilute Combustion, Exhaust Compounded (DBDC+EC) engine presented here. This paper documents some of the more unique design elements of this engine as well as a performance comparison between test data and modeling expectations. Ultimately, an experimental stoichiometric spark-ignited piston compounded engine was designed, five blocks were built, and collectively they were run for thousands of hours. The experimental engines achieved a minimum of 222 g/kW-hr BSFC with a wide region of operation under 250 g/kW-hr, and the performance matched predictions from a thermodynamic model that reflected the as-built hardware. Predictions for a 2nd generation DBDC+EC engine result in a 10% fuel economy improvement over a similar downsized boosted stoichiometric SI engine, with an additional 9% improvement for lean operation at low load. These result in minimum BSFCs of 212 and 206 g/kW-hr for the stoichiometric and lean DBD+EC Gen 2 engines respectively.
Andruskiewicz, Peter, Durrett, Russell, Najt, Paul
Experimental Comparison of Low-Load Piston Compounding Deactivation for the DBDC+EC Engine Architecture2021-01-04524/6/2021
An experimental piston compounded engine was designed with guidance from thermodynamic modeling, then was built and tested to compare the model predictions to measured results. This Downsized Boosted Dilute Combustion, Exhaust Compounded (DBDC+EC) engine concept has shown great potential for improvements in efficiency at high loads through extended second expansion process, but suffered from excessive expander cylinder pumping and low exhaust temperatures at low loads. Four expander operating strategies were experimentally tested and simulated at a range of engine speeds and loads to determine the most efficient method to deactivate the piston compounding at low loads. The most effective method involved deactivating all the expander valves and operating it as an air-spring while diverting power cylinder exhaust gasses through a separate bypass port. While this method requires some unique hardware development to enable on-the-fly actuation, it offers 15% to 22% improvements in low-load BSFC over the active expander method while improving exhaust temperatures by 100° to 150°C.
Andruskiewicz, Peter, Durrett, Russell, Najt, Paul
Further Investigations into the Benefits and Challenges of Eliminating Port Overlap in Wankel Rotary Engines2021-01-06384/6/2021
In a previous study it was shown that a production vehicle employing a Wankel rotary engine, the Mazda RX-8, was easily capable of meeting much more modern hydrocarbon emissions than it had been certified for. It was contended that this was mainly due to its provision of zero port overlap through its adoption of side intake and exhaust ports. In that earlier work a preliminary investigation was conducted to gauge the impact of adopting a zero overlap approach in a peripherally-ported Wankel engine, with a significant reduction in performance and fuel economy being found. The present work builds on those initial studies by taking the engine from the vehicle and testing it on an engine dynamometer. The results show that the best fuel consumption of the engine is entirely in line with that of several proposed dedicated range extender engines, supporting the contention that the Wankel engine is an excellent candidate for that role. Also, continued 1-D modelling of the zero overlap peripherally-ported engine has shown that a potential route to regain lost performance and better fuel economy is to turbocompound the engine. While compounding using turbomachinery provides one direction for further work, a new concept is proposed which uses the conventional three-flank Wankel rotor in its two-lobe housing to provide a positive displacement compounder to enable zero overlap anywhere in the device. This will allow the potential to configure large unobstructive ports with unimpeded timing. This novel concept is discussed in the paper.
Turner, James, Turner, Matthew, Islam, Reza, Shen, Xuankun, Costall, Aaron
Turbocompounding the Opposed-Piston 2-Stroke Engine2021-01-06364/6/2021
This paper presents analytical research conducted into the level of fuel consumption improvement that can be expected from turbocompounding a medium-duty opposed-piston 2-stroke engine, which is part of a hybridized vehicle propulsion system. It draws on a successful earlier study which showed a non-compounded opposed-piston engine to be clearly superior to other forms of 2-stroke engine, such as the widely adopted uniflow-scavenged poppet valve configuration. Electrical power transmission is proposed as the method of providing the necessary variable-speed drive to transmit excess turbine power to the system energy storage medium. The work employs one-dimensional engine simulation on a single-cylinder basis, using brake specific fuel consumption (BSFC) as the reportable metric, coupled with positive or negative power flow to the engine from the compounder; this is a variation on an approach successfully used in earlier work. Here it shows the sensitivities of the overall system to cylinder pressure, the compressor and turbine efficiencies, exhaust backpressure and also provides a means to investigate the effect of the power transmission efficiency on the overall benefit. Reheating the air before the turbine is also investigated as a means of providing a “burst” performance facility, albeit at the expense of extra fuel consumption. Positive compounding work is shown to be achievable across all investigated engine operating points under certain conditions. Operating points at lower engine speeds showed an increased propensity for turbocompounding, with 5-6% of the brake torque arising from the compounder, compared to those at higher engine speeds, where a maximum of 4% was seen. BSFC was found to be highly dependent on compounding torque with improvements only arising from reducing backpressure. A better understanding of the flow restrictions of the exhaust aftertreatment and muffler systems, for a given application, would allow for more accurate determination of the possibility for BSFC reduction within realistic operating conditions.
Young, Alexander, Turner, James, Head, Robert
A Hybrid Heavy-Duty Diesel Power System for Off-Road Applications - Concept Definition2021-01-04494/6/2021
A multi-year Power System R&D project was initiated with the objective of developing an off-road hybrid heavy-duty concept diesel engine with front end accessory drive-integrated energy storage. This off-road hybrid engine system is expected to deliver 15-20% reduction in fuel consumption over current Tier 4 Final-based diesel engines and consists of a downsized heavy-duty diesel engine containing advanced combustion technologies, capable of elevated peak cylinder pressures and thermal efficiencies, exhaust waste heat recovery via SuperTurbo™ turbocompounding, and hybrid energy recovery through both mechanical (high speed flywheel) and electrical systems. The first year of this project focused on the definition of the hybrid elements using extensive dynamic system simulation over transient work cycles, with hybrid supervisory controls development focusing on energy recovery and transient load assist, in Caterpillar’s DYNASTY™ software environment. Three key off-road applications were the focus of the hybrid concept definition with an aim of understanding the system’s modular capability for the diverse off-road heavy-duty market. Core engine performance 1D and 3D simulations isolated the efficiency contributions from the downsized engine, turbocompounding, and in-cylinder thermal barrier coatings. A fuel consumption improvement range of 14 to 24% was predicted, resulting in successful project progression to the design and experimental validation phase. An overview of the experimental engine and hybrid system status concludes the discussion along with the multi-year project’s next steps.
Koci, Chad, Steffen, Jay, Kruiswyk, Rich, Guo, Fang, Bazyn, Tim, McDavid, Robert, Ivanov, Radoslav, Sirimalla, Dheeraj
Steady State Performance of Spark Ignition Engine with Exhaust Energy Recovery2020-24-00129/27/2020
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%. If completely recovered by the use of a properly designed expander-generator unit, the energy content of the unexpanded in-cylinder gas could substantially increase the overall efficiency of the thermal unit. In the present paper the authors evaluate, by means of simple yet effective calculations, the efficiency attainable by a thermal unit composed of a spark ignition engine endowed of an exhaust gas energy recovery expander connected to a proper generator. The proposed thermal unit, which is particularly suitable for hybrid propulsion solutions, has been evaluated both in the naturally aspirated and in the supercharged version. The efficiency of each thermal unit is also compared to reference baseline engine, thus highlighting the real benefit introduced by the adoption of the proposed thermal unit. As result, it was found that the complete and efficient recovery of the unexpanded gas energy has the potential to increase the overall efficiency of the propulsion system by 10-15%, depending on the characteristics of the thermal engine and of the exhaust energy expander-generator unit.
Pipitone, Emiliano, Caltabellotta, Salvatore
Performance Improvement of an Asymmetric Twin Scroll Turbocharger Turbine through Secondary Flow Injection2020-01-10114/14/2020
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 preliminary design consists of ten design parameters, which is able to control circumferential area distributions, exit flow angles, and flow velocities. To investigate the availability of the injection system, a DOE study has been conducted with the creation of 200 different design candidates that cover the entire design space. Each design candidate is evaluated under ten different turbine operating points, which were picked from the engine exhaust pulse at 90 krpm, covering both equal and unequal admission conditions. To evaluate the turbine performance, a full-rotor steady-state simulation has been conducted using the commercial CFD solver ANSYS-CFX 19.2. This study found the injection system does not influence the original turbine matching during the idle operation (zero injection flow). Within the current DOE set-up, the mean turbine torque can be increased by 24.22%, but the improvement of energy-weighted mean turbine efficiency is limited because of the extra cost by introducing additional flow resources. The secondary flow injection system can be regarded as a novel turbocompounding technology, which can be used to increase the engine torque whenever needed. The current study reveals the availability of the novel system and provides a framework for further optimizations.
Liu, Zheng, Romagnoli, Alessandro, Palenschat, Torsten, Chiong, Meng Soon, Rajoo, Srithar, Padzillah, Muhamad H., Mamat, Aman, Kraft, Markus
CARB Low NO X Stage 3 Program - Aftertreatment Evaluation and Down Selection2020-01-14024/14/2020
With the conclusion of the California Air Resources Board (CARB) Stage 1 Ultra-Low NOX program, there continues to be a commitment for identifying potential pathways to demonstrate 0.02 g/hp-hr NOX emissions. The Stage 1 program focused on achieving the Ultra-Low NOX (ULN) levels utilizing a turbo-compound (TC) engine, which required the integration of novel catalyst technologies and a supplemental heat source. While the aftertreatment configuration provided a potential solution to meet the ULN target, a complicated approach was required to overcome challenges from low temperature exhaust. The Stage 3 program leverages a different engine architecture more representative of the broader heavy-duty industry to meet the Phase 2 Greenhouse Gas (GHG) targets and to simplify the ULN aftertreatment solution. The following work will discuss the aftertreatment technology evaluation, down selection criteria, and the emission results for the candidate ULN systems
Zavala, Bryan, Sharp, Christopher, Neely, Gary, Rao, Sandesh
MIMO Control of a Turbogenerator for Energy Recovery2020-01-02614/14/2020
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 WAVE model of the 2.0L GTDI engine was adapted to include a TG (Turbogenerator) and TBV (Turbine Bypass Valve) with the TG in a mechanical turbocompounding configuration, calibrated with steady state dynamometer data. This includes power and fuel consumption, and additionally a sensitivity analysis and knock impact assessment. Further work includes transient verification with WAVE-RT on WLTP and RDE drive cycles, estimating dynamic energy recovery, assessing electrical turbocompounding, interfacing to the powergrid, and calibration optimisation, using combined WG and TBV settings. Development of more advanced MIMO (Multiple-Input, Multiple-Output) control system algorithms and prototype testing on dynamometer or vehicle could be performed to verify design assumptions and simulation results.
Petrovich, Simon, Ebrahimi, Kambiz, Kalantzis, Nikolaos, Pezouvanis, Antonios
Isobaric Combustion: A Potential Path to High Efficiency, in Combination with the Double Compression Expansion Engine (DCEE) Concept2019-01-00851/15/2019
The efficiency of an internal combustion engine is highly dependent on the peak pressure at which the engine operates. A new compound engine concept, the double compression expansion engine (DCEE), utilizes a two-stage compression and expansion cycle to reach ultrahigh efficiencies. This engine takes advantage of its high-integrity structure, which is adapted to high pressures, and the peak motored pressure reaches up to 300 bar. However, this makes the use of conventional combustion cycles, such as the Seiliger-Sabathe (mixed) or Otto (isochoric) cycles, not feasible as they involve a further pressure rise due to combustion. This study investigates the concept of isobaric combustion at relatively high peak pressures and compares this concept with traditional diesel combustion cycles in terms of efficiency and emissions. Multiple consecutive injections through a single injector are used for controlling the heat release rate profile to achieve isobaric heat addition. In this study, the intake pressure is varied to enable a comparison between the isobaric cases with different peak pressures, up to 150 bar, and the mixed cycle cases. Tests are performed at several different levels of EGR. The experiments are performed on a 12.8 L displacement 6-cylinder Volvo D13C500 engine utilizing a single cylinder with a standard 17-compression-ratio piston. In this study, the cylinder represents the high-pressure unit of the DCEE. The fuel used in all the experiments is a standard EU diesel. In each target condition, the different injection strategies are compared with the total amount of fuel kept relatively constant. The results prove that the isobaric combustion concept is feasible with a traditional injection system and can achieve gross indicated efficiencies close to or higher than those of a conventional diesel combustion cycle. Moreover, the results show that with an isobaric cycle, heat transfer losses can be reduced by over 20%. However, the exhaust energy is higher, which can eventually be recovered in the second stage of expansion. Thus, this cycle could be suitable for the DCEE concept. The CO, UHC and soot emission levels are proven to be fairly similar to those of the conventional diesel combustion. However, the NOx emissions are significantly lower for the isobaric combustion.
Babayev, Rafig, Ben Houidi, Moez, Andersson, Arne, Johansson, Bengt
IMPROVED ENGINE PERFORMANCE AND EFFICIENCY UTILIZING A SUPERTURBOCHARGER2024-01-32818/9/2011
ABSTRACT VanDyne SuperTurbo Inc. has recently completed Phase I of an Army SBIR project entitled “Diesel Waste Heat Recovery Utilizing a SuperTurbocharger”. The project focused on modeling a SuperTurbocharger for a specific Army application and evaluating the potential benefits from a single device capable of supercharging, turbocharging and turbocompounding. The modeling effort resulted in predicted efficiency gains from both air flow management and mechanical waste heat recovery. Additionally, the modeling program revealed additional engine power available that was inaccessible with the engine’s current turbocharged configuration. This paper will cover the fundamentals of the technology, the Phase I engine modeling results and the path forward for the Phase II prototype testing project.
VanDyne, Ed, Waldron, Thomas
ACHIEVING 44% THERMAL EFFICIENCY in TODAY’S ENGINES “More for Less”2024-01-31888/17/2010
ABSTRACT The US Army is seeking improvements in the fuel efficiency of their military vehicles.. They have initiated a number of R&D projects aimed at advancing the state-of-the-art of powertrain efficiency including demonstration in a laboratory environment. This effort will set a benchmark for the vehicle integrators, allowing them to improve future vehicle offerings. The SAIC, AVL, Badenoch, QinetiQ and Ker-Train Research team offered powertrain solutions from 7 Tons to 40 Tons that achieved the goal of 44% thermal efficiency and the stringent flexible fuel and emissions requirements. In each of these offerings the team was able to identify modifications to existing engines that allowed dramatic improvements in the thermal efficiency. These efficiency improvements were achieved through a combination of techniques, combustion cycle adjustments using in-cylinder pressure monitoring and precise control of fuel injector timing, and turbo-compounding. For the R&D project, the fuel injector timing will be controlled using commercial engine development hardware and software. The high speed hardware emulates the engine control module but allows the developer to finely tune the fuel injection to maximize the 50% Maximum Fuel Burn point (MFB50) with only limited NOx production. This will be accomplished using a variety of fuels and maintaining the output power to within 2% of the engine’s nominal rating. This paper will describe the fundamental diesel combustion process that must be controlled and techniques for usable power extraction from the waste exhaust gases to provide this performance. It will describe the engine development tools that enable these controls changes to be realized within a vehicle development cycle and retain the baseline engine maturity.
McDowell, Jim, Hunter, Gary L., Hennessy, Chris
Design and Control of a Two-stage Electro-hydraulic Valve Actuation System2004-01-12653/8/2004
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.
Turner, Christopher W., Babbitt, Guy R., Balton, Christopher S., Raimao, Miguel A., Giordano, Daniel D.
High Output Compound Diesel Engine Schemes - How do they Compare with State-of-the-Art Turbocharged Engines?9520999/1/1995
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. In the second part, sections 4 and 5, the principle of the differential compound engine (DCE) as an integrated engine-transmission system is briefly described, followed by a comparative performance assessment of two alternative builds, both again using a 6 cylinder, 8 litre DI Diesel engine, in either 4 cycle or 2 cycle form, together with the results of a design study for a 1000 hp military engine. In the concluding section 6 the outstanding torque-speed and transient performance characteristics of the DCE are set against the background of the inevitable compromises involved in using high pressure air not only as the working fluid for the engine, but also for the continuously variable transmission.
Wallace, Frank
A Simulation Test Method for Deterioration of FKM Compounds Engine Crankshaft Oil Seals92237310/1/1992
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. By analyzing the elements in the seal lip compounds, it was found that the sulfur level had the greatest impact on seal material deterioration. Results of the elemental analyses of field and bench tested lip seals confirm the validity of the simulation tests presented in this paper.
Masuda, Yoshi-hiko, Nakada, Masahiko, Esaki, Yasuo, Yoshihara, Tomio, Yarimizu, Ken-ich
Concepts, Materials, and Efficiencies of Piston Compounded Adiabatic Engines9108952/1/1991
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.
Bell, James A.E.
Observation of the Combustion Process in a Heat Insulated Engine9104622/1/1991
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.
Kawamura, Hideo, Sekiyama, Shigeo, Hirai, Katsunori
Control Design for a Differential Compound Engine8903922/1/1989
A microcomputer-based controller has been designed for a differential compound engine (DCE). Following assessment of the DCE state interactions, single input-output loop strategies were developed using a dynamic simulation. The simulation, control strategies and final implementation are described, and simulated transient responses are presented.
Hall, J., Wallace, F.J.
Transient Response and Route Simulations for Heavy Vehicles with Alternative Engine-Transmission System8903932/1/1989
The paper describes the results of a study of the dynamic response of a 30 tonne truck equipped with two alternative engine-transmission systems, viz. a) the stepless differential compound engine (DCE) b) a highly turbocharged engine of the same rating with a 7 ratio stepped transmission. The comparisons cover: a) 0 - 80 krn/hr acceleration using a true dynamic and a quasi dynamic technique b) a cross country 9 km route. The DCE is shown to have superior acceleration characteristics but route behaviour of the two systems is similar.
Dequan, Zou, Rezaian, M., Wallace, F.J.
Development Status of Isuzu Ceramic Engine8800112/1/1988
Ceramics show high degree of heat resistance. But an attempt to build an adiabatic engine using ceramic materials should be carried out by full evaluation of characteristics of each ceramic material. The strength of ceramic parts are dependent on both their manufacturing processes and the mechanical and thermal stresses to which the parts are subjected. Full consideration should be given to these factors in evaluating ceramic parts. Even if a ceramic engine were manufactured after full consideration (1) to these factors, adiabatic engines proposed by R. Kamo and other researchers have had difficulty in realizing performance level and fuel economy as first suggested. Today, the adiabatic turbo compound engine still has many problems and themes to be addressed, some of which are adiabatic efficiency, combustion rate, intake air rate and method of recovering exhaust gas energy. (2),(3) On the other hand, however, an adiabatic engines with ceramic parts have already reached the stage where they can be actually used on automobiles. Further efforts, therefore, should be concentrated on attacking the aforementioned problems and themes to achieve the levels of performance suggested earlier. This paper is intended to report some part of the studies conducted by the author and his group.
Kawamura, Hideo
Future Scope of Diesel Propulsion for Merchant Marine8612079/1/1986
Since the 1973 petroleum crisis, marine diesel engine designers had to cope with the new world market requirements that is to say lower overall transportation cost and consequently: reduced fuel consumption, low maintenance cost, capability to burn the cheapest available fuel and improved reliability. These criteria and specially the two last, are more or less in contradiction. The paper enlights how, thanks to strong research and development strengths, this goal has been achieved taking as examples the SEMT PIELSTICK four stroke medium speed engines: Their specific fuel consumption is below 120 g/HP.hour, They use a Recovery Power Turbine (compound engine) enlarging their range at high torque and reduced speed, They keep their high heat recovery capability, They allow to make freely the best choice of the propeller speed. As soon as the installation (heating, purifying, filtration and water emulsification processes) are all right, they can burn the cheapest heavy fuel available on the market.
Gallois, Jacques
A Review of Engine Advanced Cycle and Rankine Bottoming Cycle and Their Loss Evaluations8301242/1/1983
Turbo aftercooled vehicle engine is widely accepted today. Two-stage turbo intercooled and aftercooled engines up to 300–350 bmep are in initial application stages for some medium speed stationary and marine diesels. Turbo compound engine has been tested and developed; the adiabatic engine concept has recently been advanced. For these advanced diesels, exhaust heat is a major source of engine performance improvement. Rankine bottom cycle has been applied the last few years to stationary engines for further exhaust heat recovery. Due to initial cost, complexity, and reliability of additional heat recovery equipment needed, few prototypes have been installed. Engine cycle exhaust is used as bottom cycle source heat as shown in the illustration below. This simplified H-S diagram gives a birds-eye view of how a basic diesel cycle and Rankine bottom cycle are coupled. The advancement of the adiabatic concept renders interesting potential for additional exhaust heat recovery.
Chen, Simon K., Lin, Rocky
Laboratory and On-Highway Testing of Diesel Organic Rankine Compound Long-Haul Vehicle Engine8301222/1/1983
An Organic Rankine-Cycle System (ORCS) designed for use with a 288-Bhp, Class 8, Long-Haul Vehicle Diesel Engine has undergone both laboratory endurance-performance testing and actual on-highway fuel economy comparison testing. Two, 1000-hour endurance tests have been conducted to demonstrate the functional integrity of the basic ORCS design and reveal any "infant mortality" problems with individual components. On highway vehicle fuel economy tests demonstrated a statistical average of 12½-percent improvement in fuel consumption. Such tests have been conducted in a project sponsored by the U.S. Department of Energy as part of their long-term national goals of improving the fuel consumption in energy-intensive industries, such as, but not restricted to, the U.S. Trucking Industry. Approximately 100,000 barrels of oil per day are expected to be saved with the full implementation of a Diesel Organic Rankine-Cycle Compound Engine in the U.S. Trucking Industry. (1)* A brief description of the basic ORCS components including the advanced microprocessor-based control system is included. The results of the laboratory endurance-performance and the on-highway vehicle tests will be given. A short discussion of the future work required in advancing the development of a commercial ORCS for long-haul vehicles is also given.
DiBella, Francis A., DiNanno, Luco R., Koplow, Michael D.
Steady State and Transient Control Through a Microprocessor-Electrohydraulic System of an Integrated Engine-Transmission Unit8305782/1/1983
The paper describes the steps in the implementation of a self-optimising steady state micro-processor control system for the integrated truck engine transmission system known as the differential compound engine (DCE). References (1–5). Although the system in its present form is based on a small and slow microprocessor, the control strategy evolved is directly applicable to the faster system ultimately envisaged. The second part of the paper deals with the requirements for faster control of transients, with particular reference to operational safety requirements, such as limiting compressor speed and maximum cylinder pressure. It is considered that the unit forms the basis for advanced on- and off-highway vehicle power plant with uniquely attractive operating characteristics.
Wallace, F. J., Howard, D., Tarabad, M.
Optimization of the Differential Compound Engine Using Microprocessor Control8102562/1/1981
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.
Wallace, F. J., Kimber, R. M.
Installation of a Diesel-Organic Rankine Compound Engine in a Class 8 Truck for a Single-Vehicle Test7906462/1/1979
A Class 8 truck has been equipped with a diesel-organic Rankine compound engine in preparation for a 1-year test program. The compound engine consists of an organic Rankine bottoming cycle system directly coupled to a Mack diesel engine from which it recovers the waste heat in the exhaust gases. The components of the bottoming cycle system are described, and their installations in three pre-assembled modules - a power conversion package, a vapor generator, and a cooling system - are discussed. Plans for the 1-year test program, including baseline performance tests on the compound engine, chassis dynamometer tests, noise tests, and over-the-road fuel economy measurements, are also outlined.
Doyle, Edward, DiNanno, Luco, Kramer, Saunders
RESULTS OF MATCHING CALCULATIONS FOR TURBOCHARGED AND COMPOUND ENGINES WITH REDUCED HEAT LOSS7908242/1/1979
The paper describes the results of matching calculations showing the effect of reduced heat loss on the interaction between an engine and the turbomachinery components. The engine used is the Perkins 6.354 six cylinder engine with low compression ratio pistons. Results are shown over a speed range between 1000-2500 rev/min for both simple turbocharged and turbocharged compound engines in either standard form or with 50% heat suppression, the effect on engine only performance being based on the results of the detailed cycle analysis described in Paper I. The results show that compounding increases the efficiency by a significant margin, while the effect of heat suppression on engine efficiency alone is relatively small.
Way, R.J.B., Wallace, F.J.
Multi-Variable Control for Engine Transmission Systems with Infinitely Variable Ratios7707522/1/1977
Two systems involving an infinitely variable connection between engine and output shaft are investigated, viz: (a) the Differential Compound Engine (DCE) (b) the shunt-hydrostatic transmission coupled to a turbocharged Diesel engine. In both cases a given demanded input shaft condition can be met with a wide range of engine operating conditions. Since at least three external controls are available in both cases, viz: (a) fuel pump metering valve or governor set point (b) turbine nozzle angle (DCE) or hydrostatic motor swash (c) engine bypass (DCE) or hydrostatic pump swash optimisation of these control settings for best overall efficiency, torque backup or minimum emissions becomes a necessity and will form an important element in traction power plant design in the future.
Wallace, F. J., Winkler, G., Bowns, D. E.
The Staged Combustion Compound Engine (SCCE): Exhaust Emissions and Fuel Economy Potential7508892/1/1975
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. The staged combustion concept was implemented using a 7.46 litre V-8 engine, for which the necessary control systems were devised and built. This engine was evaluated in an experimental vehicle on a chassis dynamometer with a 2041 kg (4500 lb) inertia weight. Present FTP emission levels are 0.87 g/mi HC, 8.7 g/mi CO, and 0.34 g/mi NOX at low mileage using a catalytic converter. FTP fuel economy is 4.9 km/ℓ (11.5 mpg), but acceleration performance is poorer than comparable production cars. Adequate evaluations of production-related factors such as driveability, durability, and fuel requirements have not been made. Although the low NOX emission demonstrated by this engine concept is noteworthy, the engine is presently precluded from serious contention by the stringent limitations which current statutes place on allowable HC and CO emissions during the 1975 FTP.
Siewert, Robert M., Turns, Stephen R.
The Differential Compound Engine - Part 1: Steady-State and Emission Characteristics7407212/1/1974
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.
Wallace, F. J., Sivakumaran, K.
The Differential Compound Engine - Part 2: Transient Response of the Differential Compound Engine (DCE) Compared with Conventional Turbocharged Engines7407222/1/1974
The paper describes experimental and analytical results for transient response of a prototype differential compound engine (DCE). It is shown that the transient response of the DCE is particularly favorable due to two inherent features: the low inertia associated with the fully floating epicyclic gearbox and inherently favorable trapped air fuel ratios. Comparisons between a hypothetical DCE and a similar turbocharged engine installed in a 24 ton truck bear on the findings on the prototype unit.
Wallace, F. J., Hargreaves, M. R. O., Bowns, D. E., Cave, P. R.
A Compound Cycle Employing Two-Stage Combustion to Reduce Automotive Air Pollution7207362/1/1972
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.
Decher, Reiner, Hertzberg, Abraham, Corlett, Richard C.
Characteristics of the Brobeck Steam Bus Engine7206842/1/1972
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. The exhaust steam is condensed in a vented system, where the exhaust is maintained at nearly atmospheric pressure. Condensate is recirculated to a monotube type vapor generator. The feedwater and burner control are similar to those used in the later Doble steam cars. Data on performance of the bus with this engine are presented.
Younger, Francis C.
The Differential Compound Engine - Further Development7100852/1/1971
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.
Wallace, F. J., Few, P. C., Cave, P. R.
The Next Decade for Piston Engines6706852/1/1967
Spark-ignition and compression-ignition piston engines are currently undergoing intense examination as energy conversion devices. Much of this attention has been focused on the contribution of these conventional engines to the air pollution problem. Exhaust emissions will be a major consideration in the design and selection of engines for the future. However, it is believed that evolutionary changes in the conventional piston engines will overcome the exhaust emission problem during the next decade. Changes in the types of engines used for the various applications may occur; if other energy conversion devices prove to be superior for a given application and are economically justified, they will break into the market presently held by our conventional engines. This paper discusses alternate powerplants we believe will be important in the next decade. It includes brief discussions of such energy conversion devices as rotary combustion engines, gas turbines, stratified-charge engines, compound engines, fuel cells, and batteries. The challenges facing the spark-ignition and compression-ignition engines are covered in detail, along with estimates of possible changes in engine design or of shifts in the use of types of engines for various applications. The effects that such changes will have on fuel and lubricant requirements are explored.
Adams, W. E., Kerley, R. V.
The Differential Compound Engine6701102/1/1967
A differential compound engine is described which indicates it to be a significant advance over other traction prime movers. Its engine rating, as confirmed by both theoretical and experimental analysis, represents an increase of approximately 150% over the corresponding naturally aspirated engine. Furthermore, the compound mode of operation implies feedback of surplus power to the output shaft and therefore overall efficiencies in excess of engine efficiency, at least over part of the load range. Values of 40% in the neighborhood of the design point can be expected, experimental work having demonstrated engine brake thermal efficiencies in excess of 42-43%. Additional advantages include rising torque characteristics with decreasing output shaft speed, the incorporation of effective engine braking, and response characteristics superior to those of a turbocharged engine.
Wallace, F. J.
Future Development of Free Piston Gasifier Turbine Combinations for Vehicle Traction6601322/1/1966
The present status and future developments of automotive outward compressing free piston gasifiers are discussed, with particular reference to gas generators in relation to turbocharged and compound engines, the present status of the machine produced by the authors' company, and the operating characteristics of a proposed 150 shaft horsepower gasifier-turbine-gearbox combination for vehicle traction. It is shown that under certain specified conditions, the gas generator cycle operates with superior efficiency, and with stated improvements in component efficiencies, the present gasifier will achieve a gas thermal efficiency of the order of 45%. Further, a vehicle power unit having an estimated specific weight of 8 lb/shp and volume of 9.75 shp/cu ft for the complete unit, with an overall torque ratio of 10:1, can be realized.
Wallace, F. J., Wright, E. J., Campbell, J. S.
Matching Fuels to Diesel Combustion Systems6304651/1/1963
A historical review of the diesel engine, from Rudolph Diesel’s original idea and machine to today’s modern applications. Consideration is given to the many development problems, and the opinions of many prominent engineers throughout the world on such aspects as the compound engine principle. Future applications and developments of the diesel engine are discussed.
Rosen, C.G.A.
Development of the Turbo Compound Engine5402391/1/1954
THE 18-cyl turbine-compounded engine developed by Wright is claimed to be an attractive powerplant for aircraft designed to fly up to speeds of about 450 mph. The compounding of this engine is accomplished by means of three blowdown turbines. This type of turbine is used because, according to the authors, it is more efficient than the pressure turbine up to an altitude of about 30,000 ft. It is estimated that at take-off a suitable pressure turbine would provide about 8% increased engine output. The present Turbo Compound engine, with its blowdown turbines, gives an 18% increase.
Wiegand, F.J., Eichberg, W.R.
Free-Piston and Turbine compound Engine–Status of the Development5402551/1/1954
THE history of the free-piston and turbine compound engine development is reviewed briefly. After consideration of the status here and abroad, the salient features of the free-piston engine concept are considered. These are mechanical simplicity, compactness, and an excellent torque-speed characteristic, coupled with a fuel economy comparable to the conventional diesel, the modern record holder in this respect. Some prognostications for the future of the development in this country are also presented.
London, A.L
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