Refine Your Search

Topic

Author

Search Results

Technical Paper

A Search for a Low Nitric Oxide Engine

1974-02-01
741172
Various homogeneous charge and stratified charge engine configurations were studied at wide-open throttle conditions, using simplified computer models. An order-of-magnitude parametric study was performed to find those combinations of variables which predicted a low nitric oxide level. Extreme values of variables were studied for a homogeneous charge engine configuration, which could be difficult to do in a real engine. As expected, these calculations indicated that for practical engine operation the equivalence ratio of the mixture must either be very rich or very lean for a resultant low nitric oxide level. Two extremes of stratified charge engine operation were investigated analytically, in other words, immediate mixing of newly formed products of rich combustion with excess air (instantaneous mixing) and a period of rich combustion followed by air addition to the rich products (delayed mixing). Comparisons of power, efficiency, and specific NOx are presented.
Technical Paper

An Experimental Study of the Delayed Mixing Stratified Charge Engine Concept

1977-02-01
770042
Preliminary computer studies indicated that the delayed mixing stratified charge engine concept might produce low emissions of nitrogen oxide and still provide reasonable efficiency and power. In the delayed mixing stratified charge engine concept a fuel-rich region is burned followed by air being mixed into the rich products. Nitrogen oxide formation was initially limited in the rich product mixtures because of the lack of oxygen and after mixing by the relatively low temperatures due to charge expansion. A single cylinder engine was used to simulate the delayed mixing stratified charge combustion process. A rich charge was drawn into the engine through the carburetor. Combustion was initiated with a spark; later air was injected to complete the combustion process. The results showed that emissions could be controlled by the delayed mixing combustion process. The engine specific power was also at reasonable levels. However, the engine efficiency was low.
Technical Paper

Air Velocity Measurements in Engines by Vortex Shedding

1974-02-01
741057
This paper describes a new application of Karman vortex shedding frequency as a velocity sensor in a motored internal combustion engine cylinder. The probe design, experimental setup and data reduction procedures are described. The quality of data obtained depends strongly on the relative frequency distribution of the free-stream turbulence and of the vortex shedding induced by the vortex generator. The instrument was evaluated on a CFR engine equipped with a shrouded intake valve. The results are presented in terms of the airswirl ratio at several selected crank angle degrees versus engine speed. The limitations of the device were also demonstrated in L-head engine tests.
Technical Paper

Experimental Determination of Local H/C Ratio and Hydrogen-Particulate

1982-02-01
820362
An intermittent sampling valve was used to investigate local fuel H/C ratio and species concentrations in an operating DI diesel engine. Additionally, predictions of carbon and hydrogen originating from particulates and nonmethane hydrocarbons (carbon and hydrogen remainders) were made by calculation. Sample H/C ratio was used to assess local fuel phase as gaseous or liquid. Evidence of intermediate species quenching in the lean region between spray plumes was found under low swirl. Reduction in the rate of penetration under high swirl may account for the observed loss in efficiency under this condition.
Technical Paper

An In Situ Determination of the Thermal Properties of Gombustion-Chamber Deposits

1982-02-01
820071
A technique for making a radiometric measurement of the deposit surface temperature in a methane-fired engine was developed. The wavelength region between 3.5 and 4.1 μm was investigated. It was determined that while the combustion gases were relatively transparent, the surface temperature measurements would contain some gas radiation. A method of averaging the measurements of many cycles and correcting these data for the gas radiation was developed. Time-averaged surface temperature was used in a steady-state heat transfer analysis to determine deposit thermal conductivity. Deposit thermal diffusivity was determined from a transient experiment in which the engine’s ignition system was turned off and the cooling response of the deposit and wall were measured.
Technical Paper

Analysis of Energy-Storage Concepts for Refuse Collection Trucks

1984-02-01
840056
Four hybrid powertrain designs are compared for a refuse collection truck driven over approach, loading and return segments of a representative route. Appropriate matching of component characteristics, drivetrain design and control strategy is shown to reduce fuel consumption by 39% to 56% compared to a conventional vehicle. Concurrently, brake usage is reduced 54% to 85% and the number of engine revolutions is reduced 66% to 84%. The four hybrid powertrains consist of “Integrated” and “Add-On” designs using flywheel or accumulator energy storage to recover braking energy and optimize engine efficiency. The average engine efficiency for each design is comparable and the vehicle fuel economy depends on the ability of each design and control strategy to minimize parasitic losses and use of the service brakes.
Technical Paper

Heavy Duty HCPC

2011-08-30
2011-01-1824
This paper concerns an innovative concept to control HCCI combustion in diesel-fuelled engines. It was named Homogenous Charge Progressive Combustion (HCPC) and operates on the split-cycle principle. In previous papers the feasibility of this combustion concept was shown for light-duty diesel engines. This paper illustrates a CFD study concerning a heavy-duty version of the HCPC engine. The engine displaces 13 liters and develops 700 kW indicated power at 2200 rpm with 49% maximum indicated efficiency and clean combustion.
Technical Paper

Sources and Tradeoffs for Transient NO and UHC Emissions with Low Temperature Diesel Combustion

2011-04-12
2011-01-1356
High bandwidth transient data from a multi-cylinder diesel engine operating in a low temperature combustion regime was analyzed to identify and characterize the transient response behaviors primarily responsible for transient emissions of NO and UHC. Numerous different speed and load transients as well as different combustion modes and control strategies were studied to determine how these parameters affect transient performance. Limitations in the transient response of the air system were found to be the largest contributor to transient emissions, although the mechanism by which these limitations affect performance can vary greatly depending on conditions. Analysis of the data shows that transient emissions for low temperature combustion strategies are highly dependent on cycle-to-cycle changes in intake charge conditions. No fundamental difference was observed between the transient processes controlling speed and load changes.
Technical Paper

A Computational Investigation of Stepped-Bowl Piston Geometry for a Light Duty Engine Operating at Low Load

2010-04-12
2010-01-1263
The objective of this investigation is to optimize a light-duty diesel engine in order to minimize soot, NOx, carbon monoxide (CO), unburned hydrocarbon (UHC) emissions and peak pressure rise rate (PPRR) while improving fuel economy in a low oxygen environment. Variables considered are the injection timings, fractional amount of fuel per injection, half included spray angle, swirl, and stepped-bowl piston geometry. The KIVA-CHEMKIN code, a multi-dimensional computational fluid dynamics (CFD) program with detailed chemistry is used and is coupled to a multi-objective genetic algorithm (MOGA) along with an automated grid generator. The stepped-piston bowl allows more options for spray targeting and improved charge preparation. Results show that optimal combinations of the above variables exist to simultaneously reduce emissions and fuel consumption. Details of the spray targeting were found to have a major impact on the combustion process.
Technical Paper

The Impact of Engine Design Constraints on Diesel Combustion System Size Scaling

2010-04-12
2010-01-0180
A set of scaling laws were previously developed to guide the transfer of combustion system designs between diesel engines of different sizes [ 1 , 2 , 3 , 4 ]. The intent of these scaling laws was to maintain geometric similarity of key parameters influencing diesel combustion such as in-cylinder spray penetration and flame lift-off length. The current study explores the impact of design constraints or limitations on the application of the scaling laws and the effect this has on the ability to replicate combustion and emissions. Multi dimensional computational fluid dynamics (CFD) calculations were used to evaluate the relative impact of engine design parameters on engine performance under full load operating conditions. The base engine was first scaled using the scaling laws. Design constraints were then applied to assess how such constraints deviate from the established scaling laws and how these alter the effectiveness of the scaling effort.
Technical Paper

Investigation of the Effects of Cetane Number, Volatility, and Total Aromatic Content on Highly-Dilute Low Temperature Diesel Combustion

2010-04-12
2010-01-0337
The objective of this study is to increase fundamental understanding of the effects of fuel composition and properties on low temperature combustion (LTC) and to identify major properties that could enable engine performance and emission improvements, especially under high load conditions. A series of experiments and computational simulations were conducted under LTC conditions using 67% EGR with 9.5% inlet O₂ concentration on a single-cylinder version of the General Motors Corporation 1.9L direct injection diesel engine. This research investigated the effects of Cetane number (CN), volatility and total aromatic content of diesel fuels on LTC operation. The values of CN, volatility, and total aromatic content studied were selected in a DOE (Design of Experiments) fashion with each variable having a base value as well as a lower and higher level. Timing sweeps were performed for all fuels at a lower load condition of 5.5 bar net IMEP at 2000 rpm using a single-pulse injection strategy.
Technical Paper

Reactivity Controlled Compression Ignition (RCCI) Heavy-Duty Engine Operation at Mid-and High-Loads with Conventional and Alternative Fuels

2011-04-12
2011-01-0363
Engine experiments and multi-dimensional modeling were used to explore Reactivity Controlled Compression Ignition (RCCI) to realize highly-efficient combustion with near zero levels of NOx and PM. In-cylinder fuel blending using port-fuel-injection of a low reactivity fuel and optimized direct-injection of higher reactivity fuels was used to control combustion phasing and duration. In addition to injection and operating parameters, the study explored the effect of fuel properties by considering both gasoline-diesel dual-fuel operation, ethanol (E85)-diesel dual fuel operation, and a single fuel gasoline-gasoline+DTBP (di-tert butyl peroxide cetane improver). Remarkably, high gross indicated thermal efficiencies were achieved, reaching 59%, 56%, and 57% for E85-diesel, gasoline-diesel, and gasoline-gasoline+DTBP respectively.
Technical Paper

Estimating Instantaneous Losses Within a Firing IC Engine Using Synthetic Variables

2011-04-12
2011-01-0611
A new method for instantaneous friction estimation in firing internal combustion engines has been developed in the Powertrain Control Research Laboratory (PCRL) at the University of Wisconsin - Madison. This Synthetic Variable approach, which has previously been used for combustion quality diagnostics, focuses on carefully measuring instantaneous engine speed and other easily measurable engine variables and combining them with dynamic models of other engine processes. This approach numerically strips away the dynamic effects that mask friction effects on engine speed and reveals friction estimates with clarity. This information could be useful for engine designers and developers to assist in accurately understanding the sources of instantaneous friction within the running engine. The friction results from these studies have been very encouraging.
Technical Paper

Coupling of Scaling Laws and Computational Optimization to Develop Guidelines for Diesel Engine Down-sizing

2011-04-12
2011-01-0836
The present work proposes a methodology for diesel engine development using scaling laws and computational optimization with multi-dimensional CFD tools. A previously optimized 450cc HSDI diesel engine was down-scaled to 400cc size using recently developed scaling laws. The scaling laws were validated by comparing the performance of these two engines, including pressure, HRR, peak and averaged temperature, and pollutant emissions. A novel optimization methodology, which is able to simultaneously optimize multiple operating conditions, was proposed. The method is based on multi-objective genetic algorithms, and was coupled with the KIVA3V Release 2 code to further optimize the down-scaled diesel engine. An adaptive multi-grid chemistry model was used in the KIVA3V code to reduce the computational cost of the optimization. The computations were conducted using high-throughput computing with the CONDOR system.
Technical Paper

Extension of the Lower Load Limit of Gasoline Compression Ignition with 87 AKI Gasoline by Injection Timing and Pressure

2014-04-01
2014-01-1302
Previous work has demonstrated the capabilities of gasoline compression ignition to achieve engine loads as high as 19.5 bar BMEP with a production multi-cylinder diesel engine using gasoline with an anti-knock index (AKI) of 87. In the current study, the low load limit of the engine was investigated using the same engine hardware configurations and 87 AKI fuel that was used to achieve 19.5 bar BMEP. Single injection, “minimum fueling” style injection timing and injection pressure sweeps (where fuel injection quantity was reduced at each engine operating condition until the coefficient of variance of indicated mean effective pressure rose to 3%) found that the 87 AKI test fuel could run under stable combustion conditions down to a load of 1.5 bar BMEP at an injection timing of −30 degrees after top dead center (°aTDC) with reduced injection pressure, but still without the use of intake air heating or uncooled EGR.
Technical Paper

Effects of Temporal and Spatial Distributions of Ignition and Combustion on Thermal Efficiency and Combustion Noise in DICI Engine

2014-04-01
2014-01-1248
The effects of the temporal and spatial distributions of ignition timings of combustion zones on combustion noise in a Direct Injection Compression Ignition (DICI) engine were studied using experimental tests and numerical simulations. The experiments were performed with different fuel injection strategies on a heavy-duty diesel engine. Cylinder pressure was measured with the sampling intervals of 0.1°CA in order to resolve noise components. The simulations were performed using the KIVA-3V code with detailed chemistry to analyze the in-cylinder ignition and combustion processes. The experimental results show that optimal sequential ignition and spatial distribution of combustion zones can be realized by adopting a two-stage injection strategy in which the proportion of the pilot injection fuel and the timings of the injections can be used to control the combustion process, thus resulting in simultaneously higher thermal efficiency and lower noise emissions.
Technical Paper

Computational Investigation of Low Load Operation in a Light-Duty Gasoline Direct Injection Compression Ignition [GDICI] Engine Using Single-Injection Strategy

2014-04-01
2014-01-1297
The use of gasoline in a compression ignition engine has been a research focus lately due to the ability of gasoline to provide more premixing, resulting in controlled emissions of the nitrogen oxides [NOx] and particulate matter. The present study assesses the reactivity of 93 RON [87AKI] gasoline in a GM 1.9L 4-cylinder diesel engine, to extend the low load limit. A single injection strategy was used in available experiments where the injection timing was varied from −42 to −9 deg ATDC, with a step-size of 3 deg. The minimum fueling level was defined in the experiments such that the coefficient of variance [COV] of indicated mean effective pressure [IMEP] was less than 3%. The study revealed that injection at −27 deg ATDC allowed a minimum load of 2 bar BMEP. Also, advancement in the start of injection [SOI] timing in the experiments caused an earlier CA50, which became retarded with further advancement in SOI timing.
Technical Paper

Experimental and Computational Assessment of Inlet Swirl Effects on a Gasoline Compression Ignition (GCI) Light-Duty Diesel Engine

2014-04-01
2014-01-1299
The light-medium load operating regime (4-8 bar net IMEP) presents many challenges for advanced low temperature combustion strategies (e.g. HCCI, PPC) in light-duty, high speed engines. In this operating regime, lean global equivalence ratios (Φ<0.4) present challenges with respect to autoignition of gasoline-like fuels. Considering this intake temperature sensitivity, the objective of this work was to investigate, both experimentally and computationally, gasoline compression ignition (GCI) combustion operating sensitivity to inlet swirl ratio (Rs) variations when using a single fuel (87-octane gasoline) in a 0.475-liter single-cylinder engine based on a production GM 1.9-liter high speed diesel engine. For the first part of this investigation, an experimental matrix was developed to determine how changing inlet swirl affected GCI operation at various fixed load and engine speed operating conditions (4 and 8 bar net IMEP; 1300 and 2000 RPM).
Technical Paper

Use of Multiple Injection Strategies to Reduce Emission and Noise in Low Temperature Diesel Combustion

2015-04-14
2015-01-0831
The low temperature combustion concept is very attractive for reducing NOx and soot emissions in diesel engines. However, it has potential limitations due to higher combustion noise, CO and HC emissions. A multiple injection strategy is an effective way to reduce unburned emissions and noise in LTC. In this paper, the effect of multiple injection strategies was investigated to reduce combustion noise and unburned emissions in LTC conditions. A hybrid surrogate fuel model was developed and validated, and was used to improve LTC predictions. Triple injection strategies were considered to find the role of each pulse and then optimized. The split ratio of the 1st and 2nd pulses fuel was found to determine the ignition delay. Increasing mass of the 1st pulse reduced unburned emissions and an increase of the 3rd pulse fuel amount reduced noise. It is concluded that the pulse distribution can be used as a control factor for emissions and noise.
X