Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ENGINES”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Model predictive control of a lean-burn gasoline engine coupled with a passive selective catalytic reduction system

Lean-burn gasoline engines have demonstrated 10–20% engine efficiency gain over stoichiometric engines and are widely considered as a promising technology for meeting the 54.5 miles-per-gallon (mpg) Corporate Average Fuel Economy standard by 2025. Nevertheless, NOx emissions control for lean-burn gasoline for meeting the stringent EPA Tier 3 emission standards has been one of the main challenges towards the commercialization of highly-efficient lean-burn gasoline engines in the United States. Passive selective catalytic reduction (SCR) systems, which consist of a three-way catalyst and SCR, have demonstrated great potentials of effectively reducing NOx emissions for lean gasoline engines but may cause significant fuel penalty due to ammonia generation via rich engine combustion. The purpose of this study is to develop a model-predictive control (MPC) scheme for a lean-burn gasoline engine coupled with a passive SCR system to minimize the fuel penalty associated with passive SCR operation while satisfying stringent NOx and NH3 emissions requirements. Simulation results demonstrate that the MPC-based control can reduce the fuel penalty by 47.7% in a simulated US06 cycle and 32.0% in a simulated UDDS cycle, compared to the baseline control, while achieving over 96% deNOx efficiency and less than 15 ppm tailpipe ammonia slip. The proposed MPC control can potentially enable high engine efficiency gain for highly-efficient lean-burn gasoline engine while meeting the stringent EPA Tier 3 emission standards.

Chen, Pingen↗
DOE OSTI2019

Enterprise: a reduced-scale, flexible fuel, single-cylinder crosshead marine diesel research engine

A custom-built 1/10 scale, flexible-fuel, single-cylinder crosshead marine diesel research engine, dubbed the Enterprise, was designed and built as a platform for conducting marine lubricant research. The engine design was focused on maintaining lubricant boundary conditions similar those of full-scale engines. The Enterprise has a rated speed of 625 rpm to match the linear mean piston speed of full-scale marine engines with the reduced stroke and is capable of 18 bar brake mean effective pressure (BMEP). A high-swirl, uniflow-scavenged, two-stroke combustion system was designed to operate on either distillate diesel or heavy fuel oil (HFO). A hydraulic electronic unit injector (HEUI) fuel injection system with two injectors having customized three-hole nozzles provides fueling and is driven by the MAHLE Flexible ECU (MFE). Intake air boost is provided using a variable speed industrial air compressor along with closed-loop electronically controlled pressure regulation. Exhaust backpressure is also controlled electronically using an electro-pneumatic butterfly valve. A customized, miniaturized Hans Jensen Lubetronic cylinder lubrication system, which is capable of delivering 0.88 mg of cylinder oil per lubricator per injection to the ring pack at up to the maximum engine overspeed rating of 656 rpm, was commissioned for the Enterprise. Four independently temperature-controlled cooling zones are used to provide control of the liner temperature profile. The four coolant zones as well as the system oil and cylinder oil supplies are all controlled within 1°C for consistent thermal boundary conditions. The engine is instrumented with an in-cylinder pressure transducer as well as an inline torque transducer and numerous process temperature and pressure measurements to allow for detailed thermodynamic efficiency analysis, and experimental facilities allow for precise measurement of liner wear and characterization of deposits on the piston and rings. A radio telemetry system from IR Telemetrics is used to measure piston crown temperatures during engine operation. Engine design considerations and experimental facilities are described in detail, along with the results of a study investigating the impact of both system oil and cylinder oil viscosity on friction and efficiency. A test matrix was designed to compare base stock chemistries and viscosities for both system and cylinder oils. Experiments were completed using a fuel economy test protocol that was defined, consisting of repeating six speed/load operating conditions. An automated dynamometer control system was implemented to ensure repeatability of the test procedure. Preliminary testing indicated that the coolant, oil, and exhaust temperatures reach a steady state within 5 minutes of changing operating conditions. The system oil viscosity was found to have a significant impact on friction, with a reduction in viscosity from SAE 30 to SAE 20 resulting in over 6% reduction in friction mean effective pressure (FMEP) and over a 2% reduction in brake-specific fuel consumption (BSFC). Chemistry effects were also evident in the system and cylinder oils. Repeatability comparisons between the individual repetitions of each operating condition were used to ensure that results are statistically valid. For the initial cylinder oil viscosity experiments, observed changes were within the established/normal repeatability; ongoing experiments will determine whether improvements in boundary condition control will enable cylinder friction changes of this magnitude to be measured on this engine platform.

Kaul, Brian↗
DOE OSTI2020

Opposed-piston engine in a light-duty truck

An opposed-piston engine is configured to fit in an engine compartment of a light-duty truck without compromising engine operations or the integrity of the engine compartment. The opposed-piston engine includes an air handling system and can be configured so that a cylinder assembly of the engine is tilted. The tilt of the cylinder assembly can allow for all of the components of the engine's air handling system to be located on one side of the opposed-piston engine. The air handling system of the opposed-piston engine can be configured with a cobra-head shaped intake duct assembly.

Warlick, Jr., Richard D.↗
DOE OSTI2018

Low pressure direct injection strategies effect on a small SI natural gas two-stroke engine’s energy distribution and emissions

This paper examines methods to simultaneously improve efficiency and reduce emissions from a 34 cc air-cooled two-stroke engine configured to operate on natural gas, using tuned intake plus exhaust resonators designed from Helmholtz resonance theory to promote effective scavenging. The engine was developed for novel application in a small, free piston engine for decentralized power generation. Operation occurred at wide-open-throttle at a speed of 5400 RPM for both port injection (PI) and low-pressure direct injection (LPDI). In both cases, the electronic ignition timing was adjusted for maximum brake torque, while the fuel was adjusted such that both rich and lean combustion were examined. The LPDI engine was then operated over a variety of engine speeds. An energy balance was completed for both PI and LPDI operation, which quantified all energy pathways, as engine operating regimes changed. Results showed that exhaust chemical energy (ECE) for LPDI was reduced significantly when compared to PI, mostly due to less fuel slip. The fuel slip rate ranged from 35 to 40% for PI operation while it was in the range of 6–20% for LPDI operation. However, mixture stratification with LPDI operation increased carbon monoxide emissions. The start-of-injection (SOI) was also examined, targeting a SOI to provide the highest trapping efficiency and most stable combustion. For LPDI operation, trapping efficiency, which is function of engine speed, showed significant effects on overall efficiency and fuel slip. Air volumetric efficiency increased due to the absence of gaseous fuel within the intake manifold. It was shown that, relative to PI, the overall engine indicated efficiency increased by 90% to a maximum indicated efficiency of 30% for LPDI operation with a SOI of 180 CAD BTDC.

42 ENGINEERING↗
DOE OSTI2018

Recent advances in metabolic engineering of Saccharomyces cerevisiae: New tools and their applications

Metabolic engineering aims to develop efficient cell factories by rewiring cellular metabolism. As one of the most commonly used cell factories, Saccharomyces cerevisiae has been extensively engineered to produce a wide variety of products at high levels from various feedstocks. In this paper, we summarize the recent development of metabolic engineering approaches to modulate yeast metabolism with representative examples. Particularly, we highlight new tools for biosynthetic pathway optimization (i.e. combinatorial transcriptional engineering and dynamic metabolic flux control) and genome engineering (i.e. clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR associated (Cas) system based genome engineering and RNA interference assisted genome evolution) to advance metabolic engineering in yeast. Lastly, we also discuss the challenges and perspectives for high throughput metabolic engineering.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2020

COMDES-MELT: A Turbofan Engine Icing Risk Analysis Tool, User’s Manual

The computational tool COMDES-MELT was developed to predict the susceptibility of turbofan engines to ice accretion when flying in an ice crystal environment. COMDES-MELT is a first-generation computational tool that can estimate the conditions at which the accretion of ice can occur, location within the turbofan engine compression system, and at which engine operating points within the flight trajectory. This is accomplished by tracking the parameters of static wet bulb temperature, ice particle melt ratio, and the ice-water to airflow rates ratio as ice crystals are ingested into the engine compression system. It has been used successfully to predict engine operating points for simulation in an altitude wind tunnel with ice crystal ingestion. These engine tests occur in a simulated ice crystal cloud environment. This predictive analysis has been used to generate the test matrix in preparation for tests in the Propulsion Systems Laboratory, an altitude test facility at the NASA Glenn Research Center. Furthermore, due to the speed of the code during an engine icing test, adjustments to the test matrix can be provided to the test engineer in real time to focus on a particular area of ice accretion susceptibility. The use of the COMDES-MELT code will be examined in this manual.

Turbofan engine↗
NASA NTRSDate not supplied

NASA Aeronautics Research Mission Directorate System Security Engineering Approaches

System security engineering (SSE) is a set of formal engineering methods and is considered a subset of systems engineering. It is a relatively new development in systems engineering with the initial NIST (National Institute of Standards) standard published in November of 2016 with updates in 2018, and 2022. The guiding principles in our methodology are based in NIST Special Publication 800-160 Vol. 1 “Systems Security Engineering: Considerations For A Multidisciplinary Approach In The Engineering Of Trustworthy Secure Systems” and integrate methodologies from common IT (Information Technology) threat modeling approaches utilizing MBSE (Model-Based Systems Engineering). The presentation will discuss how our teams utilize SSE and MBSE (Model-Based Systems Engineering) to develop secure architectures for systems under development in our NASA aeronautics research environment. This includes the activities to develop Protection Needs (PN) that, in turn result in security requirements in the design context and policies for the future state operational context for system protection. The process of applying SSE to analyze project architectures and ConOps (Concept of Operations) is intended to ensure the transferred research is both secure and securable in a “real-world” setting.

Systems Security Engineering↗
NASA NTRS2026

Understanding and Controlling Hybrid Electric Gas Turbine Engine Transient Dynamics

The electrification of the gas turbine engine is known to increase the flexibility of aircraft architectures by enabling the generation of electrical power to distribute to other electrically based, thrust producing subsystems. It also has potential for direct performance benefits in the gas turbine engine itself, both at steady state and dynamically. Although the design focus of the gas turbine engine performance is primarily at steady state, it is often the instabilities occurring during transients that cause disequilibrium and constrain performance improvements. Instabilities arise due to the disequilibrium of the energy storage mechanisms within the traditional engine system and likewise for the electrified engine system. The primary energy storage mechanisms in the traditional system are the rotational inertia, gas path volumes, the thermal masses that make up the mechanical structure, and now, the electrical power system will provide additional contributions. Understanding the effect each of these energy storage mechanisms has on the others and controlling them appropriately allows for the suppression of state changes within the turbomachinery components to the degree that the components remain near steady state, thus reducing the disequilibrium within the system. The ability to tightly regulate the state changes of turbomachinery components, such as the compressor, minimizes the excursion of the compressor operating point from the operating line (operability), allowing for higher performing, more efficient compressor designs by decreasing the amount of stall margin needed for safe engine power level changes. Preliminary studies with the electrification of the turbine engine have shown that this is possible, and this concept can lead to design trades benefitting engine performance, weight, and volume. This paper explores in detail the energy storage mechanisms and control approaches for coordinating their state changes, and ultimately proposes that a higher performing, more efficient compressor design can result.

transient dynamics↗
DOE OSTI2018

Steady-State Calibration of a Diesel Engine in Computational Fluid Dynamics Using a Graphical Processing Unit-Based Chemistry Solver

The prospect of analysis-driven precalibration of a modern diesel engine is extremely valuable in order to significantly reduce hardware investments and accelerate engine designs compliant with stricter fuel economy regulations. Advanced modeling tools, such as CFD, are often used with the goal of streamlining significant portions of the calibration process. The success of the methodology largely relies on the accuracy of analytical predictions, especially engine-out emissions. However, the effectiveness of CFD simulation tools for in-cylinder engine combustion is often compromised by the complexity, accuracy, and computational overhead of detailed chemical kinetics necessary for combustion calculations. The standard approach has been to use skeletal kinetic mechanisms (~50 species), which consume acceptable computational time but with degraded accuracy. In this work, a comprehensive demonstration and validation of the analytical precalibration process is presented for a passenger car diesel engine using CFD simulations and a graphical processing unit (GPU)-based chemical kinetics solver (Zero-RK, developed at Lawrence Livermore National Laboratory, Livermore, CA) on high performance computing resources to enable the use of detailed kinetic mechanisms. Diesel engine combustion computations have been conducted over 600 operating points spanning in-vehicle speed-load map, using massively parallel ensemble simulation sets on the Titan supercomputer located at the Oak Ridge Leadership Computing Facility. The results with different mesh resolutions have been analyzed to compare differences in combustion and emissions (NOx, carbon monoxide CO, unburned hydrocarbons (UHC), and smoke) with actual engine measurements. The results show improved agreement in combustion and NOx predictions with a large n-heptane mechanism consisting of 144 species and 900 reactions with refined mesh resolution; however, agreement in CO, UHC, and smoke remains a challenge.

42 ENGINEERING↗
NASA NTRS1953

Altitude Operational Characteristics of Prototype J40-WE-8 Turbojet Engine

The altitude operational characteristics of the prototype J40-WE-8 turbojet engine were determined in the NACA Lewis altitude wind tunnel. The operational characteristics that were obtained include (1) compressor surge characteristics, (2) acceleration and deceleration rates, (3) steady-state windmilling-engine characteristics, (4) altitude ignition characteristics, and (5) the effect of two grades of fuel on steady-state engine performance at an altitude of 45,000 feet and a flight Mach number of 0.20. The altitude ignition characteristics determined include the effects of (1) ignition fuel flow, (2) two ignition procedures, (3) fuel temperatures, and (4) two grades of fuel on ignition characteristics. The compressor surge line, when presented as a function of compressor pressure ratio and corrected engine speed, was not affected by changes in flight condition and was independent of engine-inlet installation and of the manner in which surge was approached, rapidly or slowly. Also there was no effect of altitude or engine-inlet installation on the compressor surge recovery line when presented as a function of compressor pressure ratio and corrected engine speed.

FUELS - RELATION TO ENGINE PERFORMANCE↗
DOE OSTI2021

Perceived Conflicts of Systems Engineering in Early-Stage Research and Development 1

Early Systems Research and Development (ESR&D) is one of the most crucial phases in the product development process. It both blends and blurs the lines between science and engineering, and requires a risk-based, disciplined, and graded approach to effectively manage scope, cost, and complexity of the final product. Many leaders, program managers, and scientists are unwilling to involve systems engineering because of the perception that systems engineering is heavily process oriented, adds unnecessary costs, and should be applied only to mature technologies. The value of systems engineering as applied to ESR&D is unclear to these key individuals. The unfortunate result is that system engineering is not applied to ESR&D. This results in R&D efforts that may have solved the wrong problem, selected the wrong architecture, require technical rework, have difficulty transitioning later maturity levels, and result in higher R&D costs and extended development timelines. This work discusses the difficulty of introducing systems engineering to the research and early development process and their inclination perspectives of researchers, engineers, and managers. The article shall offer potential means to manage the cultural transformation of early adoption of right-sized systems engineering in ESR&D and reverse the attitudinal positions.

42 ENGINEERING↗
DOE OSTI2018

Genome-Scale 13 C Fluxomics Modeling for Metabolic Engineering of Saccharomyces cerevisiae .

Synthetic biology is a rapidly developing field that pursues the application of engineering principles and development approaches to biological engineering. Synthetic biology is poised to change the way biology is practiced, and has important practical applications: for example, building genetically engineered organisms to produce biofuels, medicines, and other chemicals. Traditionally, synthetic biology has focused on manipulating a few genes (e.g., in a single pathway or genetic circuit), but its combination with systems biology holds the promise of creating new cellular architectures and constructing complex biological systems from the ground up. Enabling this merge of synthetic and systems biology will require greater predictive capability for modeling the behavior of cellular systems, and more comprehensive data sets for building and calibrating these models. The so-called "-omics" data sets can now be generated via high throughput techniques in the form of genomic, proteomic, transcriptomic, and metabolomic information on the engineered biological system. Of particular interest with respect to the engineering of microbes capable of producing biofuels and other chemicals economically and at scale are metabolomic datasets, and their insights into intracellular metabolic fluxes. Metabolic fluxes provide a rapid and easy to understand picture of how carbon and energy flow throughout the cell. Furthermore, we present a detailed guide to performing metabolic flux analysis and modeling using the open source JBEI Quantitative Metabolic Modeling (jQMM) library. This library allows the user to transform metabolomics data in the form of isotope labeling data from a 13 C labeling experiment into a determination of cellular fluxes that can be used to develop genetic engineering strategies for metabolic engineering.The jQMM library presents a complete toolbox for performing a range of different tasks of interest in metabolic engineering. Various different types of flux analysis and modeling can be performed such as flux balance analysis, 13 C metabolic flux analysis, and two-scale 13 C metabolic flux analysis (2S- 13 C MFA). 2S- 13 C MFA is a novel method that determines genome-scale fluxes without the need of every single carbon transition in the metabolic network. In addition to several other capabilities, the jQMM library can make model based predictions for how various genetic engineering strategies can be incorporated toward bioengineering goals: it can predict the effects of reaction knockouts on metabolism using both the MoMA and ROOM methodologies. In this chapter, we will illustrate the use of the jQMM library through a step-by-step demonstration of flux determination and knockout prediction in a complex eukaryotic model organism: Saccharomyces cerevisiae ( S. cerevisiae ). Included with this chapter is a digital Jupyter Notebook file that provides a computable appendix showing a self-contained example of jQMM usage, which can be changed to fit the user's specific needs. As an open source software project, users can modify and extend the code base to make improvements at will, allowing them to share their development work and contribute back to the jQMM modeling community.

-Omics data↗
DOE OSTI2022

Chapter 10: Advances in Protein Engineering and its Application in Synthetic Biology

Protein engineering has been used successfully in fields ranging from medicine to food science to biofuels. Applications of protein engineering include developing antiviral peptides or other protein therapeutics, antibody engineering, designing protein-based logic circuits, engineering enzymes to be more specific or to function under industrially relevant conditions such as at higher temperatures or high/low pH, modifying cell signaling or regulatory functions, and so on. Advances in recombinant DNA, "omics," and CRISPR-Cas (clustered regularly interspaced short palindromic repeats and its associated proteins) technologies, combined with high-throughput screening facilities, will lead to improved methods for protein engineering, enabling easy modification of more proteins/enzymes for new specific applications. New methods for rational design, directed evolution, and computer-aided protein design will further accelerate the speed of protein evolution and expand the scope for protein engineering. In this chapter we discuss general protein engineering strategies and advances in engineering proteins with desired functions, focusing on the "design" and "build" part of the design-build-test-learn cycle.

BIOMASS FUELS↗
DOE OSTI2021

Model predictive combustion control of a Gasoline Compression Ignition engine

Gasoline Compression Ignition is a novel combustion concept that derives its superiority from the high compression ratio of a compression ignition engine as well as the properties of gasoline fuel, such as longer ignition delay and higher volatility compared to diesel. Here, this combustion concept was experimentally tested on a 12.4L Class 8 truck engine. Based on these experimental data, prior efforts by the authors focused on the development of an engine model for a heavy-duty engine operating on a low-reactivity fuel. This engine model was leveraged within this study to investigate a combustion control strategy at different engine conditions and injection methods and was augmented to incorporate cycle-to-cycle combustion variations. State estimation is performed by means of a Kalman filter which feeds into a model predictive controller. The model predictive controller chooses control actions based on a predefined cost function under consideration of bounds reflecting physical constraints. The engine model was utilized to establish a state-space model that serves the Kalman filter and model predictive controller for estimation and prediction. A comparative study investigating control actions and engine behavior was performed with and without limiting in-cylinder peak pressure as well as combustion noise, which is of particular interest for early pilot injection strategies. In addition, the proposed control architecture was investigated at two different levels of cycle-to-cycle variations and compared to the performance of a control structure with input disturbance rejection. For increased cycle-to-cycle variations, disturbance estimation reduces state fluctuations and control effort. In general, this investigation highlights control aspects specific to a compression-ignited combustion regime with low-reactivity fuel. The control algorithm is able to maintain the desired references for brake mean effective pressure and combustion phasing while controlling peak in-cylinder pressure and combustion noise.

42 ENGINEERING↗
DOE OSTI2025

CFD modeling of near-wall combustion and unburned methane prediction in natural gas spark ignition engines

Natural gas-powered engines play a critical role in gas drilling, compression, and transmission sectors, but methane (CH 4 ) from engine combustion slip can be significant over their lifespan, contributing to atmospheric pollution and signaling reduced engine efficiency. Here, to address this challenge, computational fluid dynamics (CFD) simulations offer valuable insights into the in-cylinder combustion process, enabling the optimization of combustion strategies and engine designs to minimize unburned CH 4 slip. This study aims to evaluate and improve combustion models for simulating the combustion process and predicting unburned CH 4 concentrations in natural gas spark-ignition (SI) engines, including engines that are part of combined reformer-engine systems. Specifically, the performance of two flamelet-based combustion models—the Extended Coherent Flame Model (ECFM) and the G-equation model—was assessed using experimental engine data collected under varying excess-air ratio (λ) conditions and fuel compositions, including natural gas and syngas blends. In addition, to enhance the predictive capabilities of the G-equation model, a flame-wall interaction (FWI) sub-model was integrated into its framework. The effects of its model parameters, such as quenching and influence distance, on combustion behavior and unburned methane predictions were analyzed in detail. The ECFM tended to predict delayed combustion phasing under diluted mixture conditions, resulting in overprediction of unburned CH 4 concentrations. In contrast, the G-equation model provided reasonable predictions of combustion pressure, while representing higher the CH 4 reduction rate across the operating condition compared to experimental data. Incorporating the FWI sub-model—with the quenching distance calculated based on a pressure-dependent relation (P -0.48 ) and a fixed influence distance of 1.5 mm—further improved the G-equation model’s accuracy in predicting CH 4 reduction rates without compromising its ability to simulate the combustion process.

Combustion model↗
DOE OSTI2014

Sonic IR crack detection of aircraft turbine engine blades with multi-frequency ultrasound excitations

Effectively and accurately detecting cracks or defects in critical engine components, such as turbine engine blades, is very important for aircraft safety. Sonic Infrared (IR) Imaging is such a technology with great potential for these applications. This technology combines ultrasound excitation and IR imaging to identify cracks and flaws in targets. In general, failure of engine components, such as blades, begins with tiny cracks. Since the attenuation of the ultrasound wave propagation in turbine engine blades is small, the efficiency of crack detection in turbine engine blades can be quite high. The authors at Wayne State University have been developing the technology as a reliable tool for the future field use in aircraft engines and engine parts. One part of the development is to use finite element modeling to assist our understanding of effects of different parameters on crack heating while experimentally hard to achieve. The development has been focused with single frequency ultrasound excitation and some results have been presented in a previous conference. We are currently working on multi-frequency excitation models. The study will provide results and insights of the efficiency of different frequency excitation sources to foster the development of the technology for crack detection in aircraft engine components.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Experimental Study and Model Predictive Control of a Lean-Burn Gasoline Engine Coupled With a Passive Selective Catalytic Reduction System

Lean-burn gasoline engines have reflected 10–20% engine efficiency gain over stoichiometric engines and are widely considered as a promising technology for meeting the 54.5 miles-per-gallon (mpg) corporate average fuel economy standard by 2025. Nonetheless, nitrogen oxides (NO x ) emissions control for lean-burn gasoline for meeting the stringent Environmental Protection Agency tier 3 emission standards has been one of the main challenges toward the commercialization of highly efficient lean-burn gasoline engines in the United States. Passive selective catalytic reduction (SCR) systems, which consist of a three-way catalyst (TWC) and SCR, have demonstrated great potentials of effectively reducing NO x emissions for lean gasoline engines at low cost. Yet, passive SCR operation may cause significant fuel penalty since rich engine combustion is required for ammonia generation. The purpose of this study is to develop a model-predictive control (MPC) scheme for a lean-burn gasoline engine coupled with a passive SCR system to minimize the total equivalent fuel penalty associated with passive SCR operation while satisfying stringent NO x and ammonia (NH 3 ) emissions requirements. Simulation results demonstrate that the MPC approach can reduce the fuel penalty by 43.9% in a simulated US06 cycle and 28.0% in a simulated urban dynamometer driving schedule (UDDS) cycle, respectively, compared to the baseline control, while achieving over 97% DeNO x efficiency and less than 15 ppm tailpipe ammonia slip. The proposed MPC controller can potentially enable highly efficient lean-burn gasoline engines while meeting the stringent Environmental Protection Agency tier 3 emission standards.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2020

CONTROLLED END GAS AUTO IGNITION WITH EXHAUST GAS RECIRCULATION ON A STOICHIOMETRIC, SPARK IGNITED, NATURAL GAS ENGINE

The goal of this study is to address fundamental limitations to achieving diesel-like efficiencies in heavy duty on-highway natural gas (NG) engines. Engine knock and misfire are barriers to pathways leading to higher efficiency engines. This study explores enabling technologies for development of high efficiency stoichiometric, spark ignited, natural gas engines. These include design strategies for fast and stable combustion and higher dilution tolerance. Additionally, advanced control methodologies are implemented to maintain stable operation between knock and misfire limits. To implement controlled end- gas autoignition (C-EGAI) strategies a Combustion Intensity Metric (CIM) is used for ignition control with the use of a Woodward large engine control module (LECM). Tests were conducted using a single cylinder, variable compression ratio, cooperative fuel research (CFR) engine with baseline conditions of 900 RPM, engine load of 800 kPa indicated mean effective pressure (IMEP), and stoichiometric air/fuel ratio. Exhaust gas recirculation (EGR) tests were performed using a custom EGR system that simulates a high pressure EGR loop and can provide a range of EGR rates from 0 to 40%. The experimental measurements included the variance of EGR rate, compression ratio, engine speed, IMEP, and CIM. These five variables were optimized through a Modified Box- Benken design Surface Response Method (RSM), with brake efficiency as the merit function. A positive linear correlation between CIM and f-EGAI was identified. Consequently, CIM was used as the feedback control parameter for C-EGAI. As such, implementation of C-EGAI effectively allowed for the utilization of high EGR rates and CRs, controlling combustion between a narrower gap between knock and lean limits. The change from fixed to parametric ignition timing with CIM targeted select values of f-EGAI with an average coefficient of variance (COV) of peak pressure of 5.4. The RSM efficiency optimization concluded with operational conditions of 1080 RPM, 1150 kPa IMEP, 10.55:1 compression ratio, and 17.8% EGR rate with a brake efficiency of 21.3%. At this optimized point of peak performance, a f-EGAI for C-EGAI was observed at 34.1% heat release due to auto ignition, a knock onset crank angle value of 10.3° aTDC and ignition timing of - 24.7° aTDC. This work has demonstrated that combustion at a fixed f-EGAI can be maintained through advanced ignition control of CIM without experiencing heavy knocking events.

Cooperative Fuel Research Engine, Auto Ignition, E↗