Max Fiedler developed a lightweight automotive diesel engine with a novel combustion system, presenting initial results in 1939. A unique injection concept incorporated in the engine created a pre-mixed, semi-homogeneous charge using uniformly low injection pressures and advanced injection timing. His evidence showed: extremely smooth combustion and controlled energy release in the early stages of burning; complete elimination of diesel knock; appropriate timing of the onset of combustion; and a combustion event that remained robust through to its conclusion, likely forming a minimum of particulate. Fiedler’s work was largely ignored by other engineers of the day, but there is significant evidence in later work that both explains and confirms his basic claims. The available knowledge relating to Fiedler’s combustion system provides important information about the conditions required to produce smooth heat release in well mixed compression ignition systems.

Measuring and analyzing combustion is a critical part of the development of high efficiency and low emitting engines. Faced with changes in legislation such as Real Driving Emissions and the fundamental change in the role of the combustion engine with the introduction of hybrid-electric powertrains, it is essential that combustion analysis can be conducted accurately across the full range of operating conditions. In this work, the sensitivity of five key combustion metrics is investigated with respect to eight necessary assumptions used for single zone Diesel Combustion analysis. The sensitivity was evaluated over the complete operating range of the engine using a combination of experimental and modelling techniques. This provides a holistic understanding of combustion measurement accuracy. For several metrics, it was found that the sensitivity at the mid speed/load condition was not representative of sensitivity across the full operating range, in particular at low speeds and loads. Peak heat release rate and indicated mean effective pressure were found to be most sensitive to the determination of top dead center (TDC) and the assumption of in-cylinder gas properties. An error of 0.5° in the location of TDC would cause on average a 4.2% error in peak heat release rate. The ratio of specific heats had a strong impact on peak heat release with an error of 8% for using the assumption of a constant value. A novel method for determining TDC was proposed which combined a filling and emptying simulation with measured data obtained experimentally from an advanced engine test rig with external boosting system. This approach improved the robustness of the prediction of TDC which will allow engineers to measure accurate combustion data in operating conditions representative of in-service applications.

For past decades, substantial developments have been accomplished in internal combustion (IC) engine technology, but there still remain some possible improvements. The combustion in an IC engine is a highly intricate phenomenon, thus, numerous factors correlated with different forms of loss decides the efficiency of an engine. In spark-ignition (SI) engines, the combustion duration is considered important because it plays a key role in determining the combustion phasing for best possible energy conversion. The geometry of engine components may directly change the burning rate of air-fuel mixture, therefore, it should also be considered as significant as other aspects like exhaust gas recirculation (EGR) rate or boosting in investigation of the engine performance. This is the reason the development engineers are putting their effort to design an engine with optimized flow motion. Tweaking the flow dynamics via design modification or use of auxiliary device influences the turbulence level inside the combustion chamber, thus, the burning rate as well. Intake port orientation, masking, and piston shape are one of the typical design parameters manipulated for such purpose, and profound understanding on the effect of these design parameters on burning rate is encouraged in order to assist the optimization process. The design optimization process should be based on a fundamental understanding of how the design parameters affect the flow motion and combustion characteristics. This study aims for a simpler and faster method to investigate the consequences of design modifications. As a base model, a physics-based quasi-dimensional (QD) engine model is developed for simulation of SI combustion phenomenon. It is modeled to consider the change in flow motion and turbulence properties via simplified modeling. The advantages of such QD model is that it requires much less computational resource compared to 3D CFD model, and allows a greater degree of freedom within the simulation process which facilitates parametric studies. A zero-dimensional (0D) turbulence submodel is used to describe energy cascade mechanism, and turbulence intensity is calculated reflecting the effect cause by design modification. According to the sensitivities drawn from parametric study, the results of each effect on burning rate and other engine performance properties are compared individually and collectively. A qualitative analysis suggests how sensitive each effect are at given operating conditions. The result infers that the flow concentration by port design modification boosts the burning rate, but it is advantageous in terms of fuel economy to enhance the breathing ability by valve masking. The product of this comparative study assists an intuitive understanding on how the design modification would affect the engine operations, and it is encouraged to develop the model further via validation with experiment data to provide more reliable output. It is believed that it can be utilized as a good reference in engine design process.

A Finite Element Method (FEM) for the solution of turbulent reactive flow on parallel machines is being developed for engine and combustion modeling. This FEM solver is parallel (MPI), solves multi-species fluids using either Reynolds Averaged Navier-Stokes (RANS) k-ε model or dynamic LES model for turbulent reactive flow. The code provides an excellent platform for developing better in-cylinder fuel and species evolution, including sprays associated with injection. This code is more robust and more accurate than current engine simulators, with quick turn-around times required by design engineers. We’ve also developed a dynamic LES method which can transition through laminar to fully turbulent flow, and hence requires no assumptions about the turbulent sublayers near walls in bounded flows; this is ideal for engines where the turbulent wall layers are never in equilibrium and the flow is not always turbulent. Another key component of combustion modeling for engines is fuel injection. Spray modeling from KIVA is adopted in our work with the ability to solve large 3D turbulent flow by the help of the parallel technique.

Engine cycle-by-cycle combustion variation is a potential source of emissions and drivability issues in automobiles, and has become an important concern for engine control engineers. The nature of turbulent combustion in IC engines means that combustion variations cannot be eliminated completely. Furthermore, it is inevitable for the engine to run at conditions with high combustion variations in most vehicle applications. For example, during gear shifts spark timing can be changed dramatically to help track the fast transitions of torque demand, often resulting in high Coefficient of Variation in Indicated Mean Effective Pressure (COV of IMEP). Under these circumstances, the control engineers have to weigh between combustion variation and other performance demands (i.e. fast torque tracking). An accurate online estimation of COV of IMEP can be beneficial to this process. A calibrated map of COV of IMEP versus engine operating conditions can be an option for engines with few control actuators. As the number of control actuators increases, combustion variation modelling using inputs with physical representations becomes favorable due to the potential for reduced calibration effort. However, since COV of IMEP is a stochastic variable describing the distribution of IMEP output, it can only be modelled empirically. This research proposes a control-oriented real-time COV of IMEP model based on an Artificial Neural Network (ANN) and inputs from turbulent combustion research. The effects of premixed turbulent combustion variation are analyzed with flame regime analysis in this research after a brief introduction of the experimental setup and engine information. In-cylinder thermodynamics are then evaluated to reveal how the changes of heat release transform into the variation of cylinder pressure, producing COV of IMEP. A range of model input parameters are assessed to determine the set that produces the most accurate prediction of IMEP variation with minimal computational requirements. An Artificial Neural Network (ANN) is applied to capture the nonlinear coupled correlations between COV of IMEP and model inputs. The ANN is combined with a regression pretreatment to reduce network size and improve extrapolation stability. This computationally efficient single-layer three-neuron ANN COV of IMEP model achieved 0.29% normalized Root Mean Square Error (RMSE). Dynamometer tests show that the model performs well outside the training region.

In-cylinder surface temperature has significant impacts on the thermo-kinetics governing the Homogeneous Charge Compression Ignition (HCCI) process. Thermal Barrier Coatings (TBCs) enable selective manipulation of combustion chamber surface temperature profiles throughout a fired cycle. In this way, TBCs enable a dynamic surface temperature swing, which prevents charge heating during intake while minimizing heat rejection during combustion. This preserves volumetric efficiency while fostering more complete combustion and reducing emissions. This study investigates the effect of a Yttria-Stabilized Zirconia (YSZ) coating on Low Temperature Combustion (LTC) engine combustion, efficiency, and emissions. This is an initial step in a systematic effort to engineer coatings best suited for LTC concepts. A YSZ coating was applied to the top of the aluminum piston using a powder Air Plasma Spray process, Final thickness of the coatings was approximately 150 microns. The coated piston was subsequently evaluated in the single-cylinder HCCI engine with exhaust re-induction. Engine tests indicated significant advancement of the autoignition point and reduced combustion durations with the YSZ coating. Hydrocarbon and carbon monoxide emissions were reduced, thereby increasing combustion efficiency. The combination of higher combustion efficiency and decreased heat loss during combustion produced tangible improvements in thermal efficiency. When the effects of combustion advance were removed, the overall improvements in emissions and efficiency were lower, but still significant. Overall, the results encourage continued efforts to devise novel coatings for LTC.

There is increasing interest in application of various alternative fuels in marine diesel engines, including methanol. One of the challenges in the relevant research is the development of computer codes for simulation of the dual-fuel working process and engineering optimization of engines. In this work the mathematical model is described which simulates a mixture formation and combustion in an engine with a dual-fuel system, in which methanol is used as main fuel and a pilot portion of diesel oil is injected to ignite methanol. The developed combustion model was incorporated into the existing engine full cycle thermodynamic simulation tool, namely DIESEL-RK [1]. The developed combustion model includes the self-ignition delay calculation sub-model based on the detail chemistry simulation of methanol pre-combustion reactions, sub-model of evaporation of methanol droplets, submodels of methanol fuel sprays penetration, spray angle and droplets forming, respectively. The developed computer code allows engineers to account for the arbitrary shape of the combustion chamber. Additionally, each fuel system (for methanol and diesel oil) may include several injectors with arbitrary oriented nozzles with different diameters and central, off-central and side location in the combustion chamber. The fuel sprays evolution model consists of equations with dimensionless parameters to account for fuel properties and in-cylinder conditions. Specifics of injection pressure profiles and interaction of sprays with the air swirl and between themselves are also considered. The model allows engineers to carry out rapid parametric analysis. Results of modelling for a medium speed dual-fuel diesel engine are presented which demonstrate a good agreement between calculated and experimental heat release curves and integral engine data.

The Chevrolet Small-Block engine was officially introduced to the public as one of the two engines in the 1955 Chevrolet passenger car. Its companion engine powering Chevrolet products was the very dated “Blue-Flame” 6. This six-cylinder driven powertrain was a key contributor to the reputation at that time that Chevrolet cars were dull and, at best, average. The team: In late 1952, my father, Ed Cole, assumed the role as Chevrolet Chief Engineer. A few years earlier he was the Chief Engineer at Cadillac and led the development of a new, advanced design overhead valve V-8. The expectation at Chevy was that he would lead the development of a Chevrolet version but he had other ideas. At this time each GM division had their own powertrain operations. Key people were recruited from across the company based on their unique skills. The entire effort of developing, tooling and launch of the engine, as well as the total vehicle, took less than 2 years. The engine: The Small-Block engine was considered revolutionary at that time. Features included a new casting technology that reduced the casting cores by about half, a valve train that featured simple stamped rocker arms that pivoted on individual studs and elimination of all external oil lines. Its weight was over 40 pounds less than the Blue-Flame 6 and it was very compact. The Chevrolet Small-Block V-8 was a revolutionary engine when it was developed in the 50’s, and even today the basic architecture of the current GM Small-Block is similar.

The natural gas industry has long depended on large bore, two-stroke cycle, spark-ignited, gas-powered, reciprocating engines to move gas from the well to the pipeline and downstream. As regulations governing the pollutant emissions from these engines are tightened the industry is turning to the engine OEMs for a solution. The challenge of further reducing engine emissions is not a new task to the industry. However, as the requirements placed on the engines are further restricted, the technology required to achieve these goals becomes more advanced, along with the required tools and technology to create it. New predictive tools have been created and have become more powerful and capable as computer software and hardware becomes more advanced, enabling engineers to create more complex designs and to do so quickly and at lower cost, all of which may not have been possible previously. This paper investigates methods used in designing the Ajax 2800 series, which is a large bore, two-stroke cycle, gas-powered, reciprocating engine and the improvements in emissions that resulted from the application of these methods.. Solutions to overcoming the challenges encountered during the process will also be presented.

A comparative cold flow analysis between Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) cycle-averaged velocity and turbulence predictions is carried out for a single cylinder engine with transparent combustion chamber (TCC) under motored conditions using high-speed Particle Image Velocimetry (PIV) measurements as the reference data. Simulations are done using a commercial CFD code CONVERGE with the implementation of standard k-ε and RNG k-ε turbulent models for RANS and a one-equation eddy viscosity model for LES. The following aspects are analyzed in this study: 1. The effects of computational domain geometry (with or without intake and exhaust plenums) on mean flow and turbulence predictions for both LES and RANS simulations 2. Comparison of LES versus RANS simulations in terms of their capability to predict mean flow and turbulence Both RANS and LES full and partial geometry simulations are able to capture the overall mean flow trends qualitatively; but the intake jet structure, velocity magnitudes, turbulence magnitudes and its distribution are more accurately predicted by full geometry simulations. The guideline therefore for CFD engineers is that RANS partial geometry simulations (computationally least expensive) are good enough for capturing overall qualitative flow trends. However, if one is interested in getting reasonably accurate estimates of velocity magnitudes, flow structures, turbulence magnitudes and its distribution, they must resort to LES simulations. Furthermore, to get the most accurate turbulence distributions, one must consider running LES full geometry simulations.

Accurate combustion analysis at the test bed is an important tool for the development engineer. It can help engine design, efficiency improvements or emissions reduction by providing instantaneous feedback on the combustion process. It can also provide detailed combustion information to help speed-up the engine calibration process. By implementing shared memory communication, multiple core capability and streamlined calculation techniques, the calculation time of AVL gas exchange and combustion analysis software GCA (Gas Exchange and Combustion Analysis) has been dramatically reduced without significantly decreasing calculation results accuracy. This allows AVL IndiCOM (in combination with AVL GCA) to perform accurate gas exchange and combustion analysis calculations directly and promptly at the test bed. This opens the door to a number of promising new applications by erasing the bridge between measurement data acquisition and post-processing analysis. Increase of measurement data consistency and the reduction of development time are two of the most important benefits of being able to perform “on-line” plausibility checks of measurement data. The strong links connecting AVL GCA calculation results to the measurement data and the redundancy between calculation and measurement for the assessment of some highly relevant engine parameters (e.g. IMEP, air mass flow) can greatly extend the “on-line” plausibility checks functions already available in AVL IndiCom or AVL test bed automation software PUMA. Some passenger car application examples, where valve train flexibility is used to enhance fuel economy or reduce exhaust emissions of internal combustion engines, show that the immediate availability at the test bed of gas exchange related parameters (e.g. internal EGR rate, scavenged mass, mass flows through the valves) supports an intuitive optimization of the valve train parameters.

The variable stroke length of the free-piston engine poses an interesting problem for the controls engineer. At a low level, the control system must be able to track piston position and address changes in top and bottom dead center positions. To accomplish this, a new FPGA (field programmable gate array) based engine position tracking software was developed, along with a simple method of mapping from a conventional engine control system to a free-piston control system. The tracking software was integrated into a complete rapid prototyping control system that was responsible for all control actions of the engine. The control system was laboratory tested on the HiPerTEC, an opposed, free-piston engine with a circular piston arrangement (as opposed to linear free-piston engines) developed by Applied Thermal Sciences, Inc (ATS). The control system has been demonstrated to run 8 cylinders up to an effective speed of 2,200rpm in spark ignition mode.

When designing control systems, it is important to keep in mind the end-users. In general, the complexity and difficulty of implementing and tuning a control strategy determine if such a strategy should be adopted, despite its performance. The automotive industry is no exception to that; powertrain control system engineers are constantly tasked to design controllers that are simple to follow, fairly robust, and require moderate resources for implementation and validation. Obviously, stability is critical for any control strategy; an oscillating controller not only could result in fluctuation in engine torque which could lead to customer dissatisfaction, but also could have a negative impact on vehicle tailpipe emissions. Bottom line is the controller must provide good stability as well as superb reference tracking. Proportional–Integral-Derivative (PID) controllers are attractive solutions for powertrain calibrators. They are widely used in the automotive industry as they are easy to implement and tune, especially when the Derivative term is dropped to reduce the sensitivity of the system and improve its robustness. Consequently, with only two gains to adjust, tuning a PI controller is a relatively simple task, but quite often calibrators struggle trying to meet both stability requirements and tracking performance. Adding a Smith Predictor (SP) to the PI controller, is one way to achieve the tracking performance desired. This is indeed a well known approach that allows for much higher gains to be used in order to improve the tracking ability while maintaining stability in the presence of plant models changing dynamics and system delays. However, with this combination (PI-SP), the robustness of the overall control strategy suffers as errors in the plant models tend to reduce the stability of the over all system and could potentially lead to an unstable or undesirable performance. In this paper, we will present a practical approach to improve the performance and robustness of the PI controller. This is achieved by adding unity-gain feed-forward (FF) of the air fuel set point for improved tracking plus a set-point filter in the input to the PI controller (FF-PI) to prevent overshoots. We will also show that this control structure provides excellent and robust reference tracking without destabilizing the system in the presence of errors in the plant model. In addition, we will include results obtained with the FF-PI controller when applied to two applications: Air-fuel ratio (A/F) control for gasoline lean burn vehicles (5.4L F150 and 4.0L Ford of Australia Falcon), and Exhaust Gas Recirculation (EGR) control on a 2.0L Gasoline, Turbocharged, Direct Injection Engine.

Generating an optimum cam profile for an internal combustion engine application is usually a very involved process. This is because of the challenge faced by the engine engineers to perform several trade-offs between fuel economy, performance, durability and emissions. Typically, the trade offs are worked out using several computer codes and with the involvement of a cross-functional team of engineers. Hence, there is a need to develop a tool that can encapsulate the various computer codes and can manipulate the cam profile with ease. With the existence of such an automated tool, optimization of the cam profile can be achieved with a specified trade-off between the several metrics identified above. This paper describes the development of such a tool, and discusses the ingredients that make it flexible and computationally efficient. Results from the use of this tool are documented in this paper as well.

Rising fuel costs and increasingly stringent emission standards push engineers to develop more efficient turbo-machinery. Reducing turbocharger turbine tip clearance is one method of improving turbine performance, thereby improving overall engine operation. By using tip seals or abradable seals, reduction of this clearance is possible. Metco 314 NS material was applied to an Elliot-H type turbocharger turbine shroud to reduce the cold clearance from 0.762 mm (0.030 inch) to 0.457mm (0.018 inch). Two separate yet virtually identical performance tests were conducted at speeds of 13,000 rpm, 15,000 rpm, and 17,000 rpm on the turbocharger. The first test established the efficiency condition of the turbocharger with the tip seal installed. The second was to quantify a decrease in efficiency, if present, after the tip seal was removed. Both tests were conducted as identically as possible. The average amount of available energy not utilized with the tip seal removed was 30.26 kW at 13,000 rpm, 51.42 kW at 15,000 rpm and 45.71 kW at 17,000 rpm.

Advancing simulation technologies are making it possible for engineers to construct models of increasing complexity and fidelity. Southwest Research Institute (SwRI ® ) has investigated integrated analysis techniques that account for the dynamic interaction of cylinder load, hydrodynamic bearing orbits and flexible structural components in a time-based multi-body structural simulation. Misalignment of the main bearing bore is also simulated to investigate a condition that affects this type of mechanical system. This paper describes general modeling techniques implemented in ADAMS/Engine and how the component models influence the prediction of crankshaft stress through simulation of an HBA-6 engine/compressor. The HBA-6 is one of a class of reciprocating compressors used in the gas pipeline and process industries. It has a unique layout of power and compressor cylinders that helps to highlight the robustness of the simulation technique.

Fierce competition, particularly in the market for medium-speed four-stroke diesel engines, requires the continuous technical development of the products available in that market. Alongside the continued pressure on reducing prices and demands for low fuel consumption rates without compromising power/bulk ratios and reliability, optimization work on medium-speed engines is increasingly also dominated by a tightening of emission regulations. Soot concentrations in the exhaust below the visibility level and constantly falling NO x exhaust concentrations place ever greater demands, particularly on the combustion process, supercharging and fuel injection systems. Recent years have seen extensive basic development work in this field using simulation calculations and tests on our 1L 32/40 research engine. This work produced an array of measures with which the trade-off between soot, NO x and specific fuel consumption can be effectively reduced. This paper discusses how these customer and market led measures are being implemented by our design engineers in our 32/40 and 48/60 engine types.

Engine oil consumption is an important source of hydrocarbon and particulate emissions in modern automobile engines. Great efforts are being made in recent years to minimize the impact of oil consumption on engine emissions. Research engineers continue to study the sources and driving mechanisms of oil consumption. Of these mechanisms, the contribution from the Positive Crankcase Ventilation (PCV) system is the least investigated. However, recent studies have shown that the blowby contribution to oil consumption could be significant under certain conditions. The PCV system refers to the system that vents the blowby gases loaded with oil back to the engine air intake system. It includes oil separators, air breather connecting the intake with the crankcase, and a flow-regulating valve. In a closed crankcase ventilation system, the oil-loaded blowby and crankcase gases are fed back into the air intake. Blowby gases are formed during engine operation by leakage of unburdened and compressed air-fuel mixture from the combustion chamber past the engine piston and ring pack into the crankcase. The oil that is circulated back into the intake through the PCV system could leave deposits in the intake manifold, and thus both the quantity and physical characteristics of the re-circulated oil are of great interest. This study analyzes the PCV blowby-oil consumption mechanisms and examines the main oil sources and oil characteristics by combining oil-consumption with in-cylinder measurements. A sulfur-tracer method was used along with a gravimetric method to measure the blowby oil consumption dependence on oil level, coolant outlet temperature, operating speed and load in a production spark ignition engine. Liquid oil distribution on the liner and piston was also studied using a Laser Induced Fluorescence (LIF) technique. In addition, in-cylinder variables such as the liner temperature and cylinder pressure that affect the oil evaporation and blowby flow rates were also measured. The blowby oil consumption map showed an increase in oil consumption with load and speed. Further analysis showed that the blowby flow was mainly dependent on the load of the engine, whereas the oil concentration in the blowby did not show this strong relationship. Whether the blowby gases pick up more oil in the ring-pack region than oil in the crankcase was thus carefully analyzed. Supplementally, a strong relationship was observed between oil consumption and sump oil level, showing that oil in the crankcase is an important source of oil in the blowby. More experiments were run at different coolant outlet temperatures to study the blowby oil consumption aimed at identifying the sources of oil in the blowby. The results show that oil evaporation is dependent on the liner temperatures that increase with load and speed. These data provided additional information to distinguish among the possible sources of blowby oil consumption. Additional experimentation was carried out to estimate drop-size distribution of oil suspended in the ventilated gases, which showed that entrainment of small oil droplets in the PCV flow varied with both speed and load.

Due to market demands aimed at increasing the efficiency and the power density of gas engines, existing ignition systems are rapidly approaching their limits. To avoid this, gas engine manufacturers are seeking new technologies. From the viewpoint of gas engine R&D engineers, ignition of the fuel/air mixture by means of a laser has great potential. Especially the thermodynamic requirements of a high compression ratio and a high power density are fulfilled well by laser ignition. Results of measurements on the test bench confirm the high expectations — with a BMEP of 1.8 MPa it was possible to verify NOx values of a non-optimized system of 30 ppm (70 mg/Nm 3 @ 5 % O 2 ) with very high combustion stability. Despite this, considerable developmental steps are still necessary to adapt the laser ignition concept fully to desired objectives (especially costs).