28 Matching Results

Search Results

Advanced search parameters have been applied.

in creator/contributor: "Martinez-Frias, J."

open access

Analysis of Homogeneous Charge Compression Ignition (HCCI) Engines for Cogeneration Applications

This paper presents an evaluation of the applicability of Homogeneous Charge Compression Ignition Engines (HCCI) for small-scale cogeneration (less than 1 MWe) in comparison to five previously analyzed prime movers. The five comparator prime movers include stoichiometric spark-ignited (SI) engines, lean burn SI engines, diesel engines, microturbines and fuel cells. The investigated option, HCCI engines, is a relatively new type of engine that has some fundamental differences with respect to oth… more

Date: April 30, 2004

Creator: Aceves, S; Martinez-Frias, J & Reistad, G

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Final Progress Report for the NASA Inductrack Model Rocket Launcher at the Lawrence Livermore National Laboratory

The Inductrack magnetic levitation system, developed at the Lawrence Livermore National Laboratory, was studied for its possible use for launching rockets. Under NASA sponsorship, a small model system was constructed at the Laboratory to pursue key technical aspects of this proposed application. The Inductrack is a passive magnetic levitation system employing special arrays of high-field permanent magnets (Halbach arrays) on the levitating cradle, moving above a ''track'' consisting of a close-… more

Date: June 27, 2001

Creator: Tung, L S; Post, R F & Martinez-Frias, J

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Certification Testing and Demonstration of Insulated Pressure Vessels for Vehicular Hydrogen Storage

Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen or ambient-temperature compressed hydrogen. This flexibility results in multiple advantages with respect to compressed hydrogen tanks or low-pressure liquid hydrogen tanks. Our work is directed at verifying that commercially available aluminum-lined, fiber-wrapped pressure vessels can be safely used to store liquid hydrogen. A series of tests have been conducted, and the results indicate th… more

Date: May 22, 2002

Creator: Aceves, S. M.; Martinez-Frias, J. & Espinosa-Loza, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Analysis of a High-Efficiency Natural Gas-Assisted Steam Electrolyzer for Hydrogen Production

This paper presents a description and analysis of a high-efficiency hydrogen production system. The main component of the system is a novel steam electrolyzer. In conventional electrolyzers, oxygen produced from electrolysis is usually released into the environment. In this design, natural gas is used to react with the oxygen produced in the electrolysis, reducing reduce the chemical potential difference across the electrolyzer, thus minimizing electricity consumption. The oxygen produced from … more

Date: June 26, 2001

Creator: Martinez-Frias, J.; Pham, A. Q. & Aceves, S. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Performance Evaluation Tests of Insulated Pressure Vessels for Vehicular Hydrogen Storage

Date: March 1, 2002

Creator: Aceves, S M; Martinez-Frias, J & Espinoza-Loza, F

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Prediction of Carbon Monoxide and Hydrocarbon Emissions in Isooctane HCCI Engine Combustion Using Multi-Zone Simulations

Homogeneous Charge Compression Ignitions (HCCI) engines show promise as an alternative to Diesel engines, yet research remains: development of practical HCCI engines will be aided greatly by accurate modeling tools. A novel detailed chemical kinetic model that incorporates information from a computational fluid mechanics code has been developed to simulate HCCI combustion. This model very accurately predicts many aspects of the HCCI combustion process. High-resolution computational grids can be… more

Date: May 2, 2002

Creator: Flowers, D; Aceves, S M; Martinez-Frias, J & Dibble, R

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Coal-Fired Power Plant with Zero Atmospheric Emissions

This paper presents the thermodynamic analysis of a coal-based zero-atmospheric emissions electric power plant. The approach involves an oxygen-blown coal gasification unit. The resulting synthetic gas (syngas) is combusted with oxygen in a gas generator to produce the working fluid for the turbines. The combustion produces a gas mixture composed almost entirely of steam and carbon dioxide. These gases drive multiple turbines to produce electricity. The turbine discharge gases pass to a condens… more

Date: May 27, 2003

Creator: Martinez-Frias, J; Aceves, S M; Smith, J R & Brandt, H

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Insulated Pressure Vessels for Vehicular Hydrogen Storage: Analysis and Performance Evaluation

Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen (LH{sub 2}) or ambient-temperature compressed hydrogen (CH{sub 2}). Insulated pressure vessels offer the advantages of liquid hydrogen tanks (low weight and volume), with reduced disadvantages (fuel flexibility, lower energy requirement for hydrogen liquefaction and reduced evaporative losses). The work described here is directed at verifying that commercially available pressure vessels can… more

Date: June 26, 2001

Creator: Aceves, S. M.; Martinez-Frias, J.; Garcia-Villazana, O. & Espinosa-Loza, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Vehicular Storage of Hydrogen in Insulated Pressure Vessels

This paper describes the development of an alternative technology for storing hydrogen fuel onboard automobiles. Insulated pressure vessels are cryogenic-capable pressure vessels that can accept cryogenic liquid fuel, cryogenic compressed gas or compressed gas at ambient temperature. Insulated pressure vessels offer advantages over conventional H{sub 2} storage approaches. Insulated pressure vessels are more compact and require less carbon fiber than GH{sub 2} vessels. They have lower evaporati… more

Date: January 3, 2005

Creator: Aceves, S. M.; Berry, G. D.; Martinez-Frias, J. & Espinosa-Loza, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Performance and Certification Testing of Insulated Pressure Vessels for Vehicular Hydrogen Storage

Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen (LH2) or ambient-temperature compressed hydrogen (CH2). Insulated pressure vessels offer the advantages of liquid hydrogen tanks (low weight and volume), with reduced disadvantages (fuel flexibility, lower energy requirement for hydrogen liquefaction and reduced evaporative losses). The work described here is directed at verifying that commercially available pressure vessels can be safely u… more

Date: June 3, 2001

Creator: Aceves, S. M.; Martinez-Frias, J.; Garcia-Villazana, O. & Espinosa-Loza, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

HCCI engine control by thermal management

This work investigates a control system for HCCI engines, where thermal energy from exhaust gas recirculation (EGR) and compression work in the supercharger are either recycled or rejected as needed. HCCI engine operation is analyzed with a detailed chemical kinetics code, HCT (Hydrodynamics, Chemistry and Transport), that has been extensively modified for application to engines. HCT is linked to an optimizer that determines the operating conditions that result in maximum brake thermal efficien… more

Date: May 11, 2000

Creator: Martinez-Frias, J; Aceves, S M; Flowers, D; Smith, J R & Dibble, R

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Low Temperature and High Pressure Evaluation of Insulated Pressure Vessels for Cryogenic Hydrogen Storage

Date: June 25, 2000

Creator: Aceves, S.; Martinez-Frias, J. & Garcia-Villazana, O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Certification Testing and Demonstration of Insulated Pressure Vessels for Vehicular Hydrogen and Natural Gas Storage

We are working on developing an alternative technology for storage of hydrogen or natural gas on light-duty vehicles. This technology has been titled insulated pressure vessels. Insulated pressure vessels are cryogenic-capable pressure vessels that can accept either liquid fuel or ambient-temperature compressed fuel. Insulated pressure vessels offer the advantages of cryogenic liquid fuel tanks (low weight and volume), with reduced disadvantages (fuel flexibility, lower energy requirement for f… more

Date: May 22, 2002

Creator: Aceves, S. M.; Martinez-Frias, J.; Espinosa-Loza, F.; Schaffer, R. & Clapper, W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Equivalence Ratio-EGR Control of HCCI Engine Operation and the Potential for Transition to Spark-Ignited Operation

This research investigates a control system for HCCI engines, where equivalence ratio, fraction of EGR and intake pressure are adjusted as needed to obtain satisfactory combustion. HCCI engine operation is analyzed with a detailed chemical kinetics code, HCT (Hydrodynamics, Chemistry and Transport), that has been extensively modified for application to engines. HCT is linked to an optimizer that determines the operating conditions that result in maximum brake thermal efficiency, while meeting t… more

Date: July 31, 2001

Creator: Martinez-Frias, J; Aceves, S M; Flowers, D L; Smith, J R & Dibble, R

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Evaluation of insulated pressure vessels for cryogenic hydrogen storage

This paper presents an analytical and experimental evaluation of the applicability of insulated pressure vessels for hydrogen-fueled light-duty vehicles. Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen (LH?) or ambient-temperature compressed hydrogen (CH2). Insulated pressure vessels offer the advantages of liquid hydrogen tanks (low weight and volume), with reduced disadvantages (lower energy requirement for hydrogen liquefaction and re… more

Date: March 1, 1999

Creator: Aceves, S M; Garcia-Villazana, O & Martinez-Frias, J

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Computer Generated Reduced Iso-Octane Chemical Kinetic Mechanism Applied to Simulation of HCCI Combustion

This paper shows how a computer can systematically remove non-essential chemical reactions from a large chemical kinetic mechanism. The computer removes the reactions based upon a single solution using a detailed mechanism. The resulting reduced chemical mechanism produces similar numerical predictions significantly faster than predictions that use the detailed mechanism. Specifically, a reduced chemical kinetics mechanism for iso-octane has been derived from a detailed mechanism by eliminating… more

Date: August 12, 2002

Creator: Aceves, S. M.; Martinez-Frias, J.; Flowers, D.; Smith, J. R.; Dibble, R. & Chen, J. Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fuel and Additive Characterization for HCCI Combustion

This paper shows a numerical evaluation of fuels and additives for HCCl combustion. First, a long list of candidate HCCl fuels is selected. For all the fuels in the list, operating conditions (compression ratio, equivalence ratio and intake temperature) are determined that result in optimum performance under typical operation for a heavy-duty engine. Fuels are also characterized by presenting Log(p)-Log(T) maps for multiple fuels under HCCl conditions. Log(p)-Log(T) maps illustrate important pr… more

Date: February 12, 2003

Creator: Aceves, S. M.; Flowers, D.; Martinez-Frias, J.; Espinosa-Loza, F.; Pitz, W. J. & Dibble, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Operation of a Four-Cylinder 1.9L Propane Fueled Homogeneous Charge Compression Ignition Engine: Basic Operating Characteristics and Cylinder-to-Cylinder Effects

A four-cylinder 1.9 Volkswagen TDI Engine has been converted to run in Homogeneous Charge Compression Ignition (HCCI) mode. The stock configuration is a turbocharged direct injection Diesel engine. The combustion chamber has been modified by discarding the in-cylinder Diesel fuel injectors and replacing them with blank inserts (which contain pressure transducers). The stock pistons contain a reentrant bowl and have been retained for the tests reported here. The intake and exhaust manifolds have… more

Date: March 12, 2001

Creator: Flowers, D.; Aceves, S. M.; Martinez-Frias, J.; Smith, J. R.; Au, M.; Girard, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Operation of a Four-Cylinder 1.9L Propane Fueled HCCI Engine

Date: March 15, 2001

Creator: Flowers, D.; Aceves, S. M.; Martinez-Frias, J.; Smith, J. R.; Au, M.; Girard, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

HCCl Combustion: Analysis and Experiments

Homogeneous charge compression ignition (HCCI) is a new combustion technology that may develop as an alternative to diesel engines with high efficiency and low NOx and particulate matter emissions. This paper describes the HCCI research activities being currently pursued at Lawrence Livermore National Laboratory and at the University of California Berkeley. Current activities include analysis as well as experimental work. On analysis, we have developed two powerful tools: a single zone model an… more

Date: May 4, 2001

Creator: Aceves, S. M.; Flowers, D. L.; Martinez-Frias, J.; Smith, J. R.; Dibble, R.; Au, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Analysis of the Effect of Geometry Generated Turbulence on HCCI Combustion by Multi-Zone Modeling

This paper illustrates the applicability of a sequential fluid mechanics, multi-zone chemical kinetics model to analyze HCCI experimental data for two combustion chamber geometries with different levels of turbulence: a low turbulence disc geometry (flat top piston), and a high turbulence square geometry (piston with a square bowl). The model uses a fluid mechanics code to determine temperature histories in the engine as a function of crank angle. These temperature histories are then fed into a… more

Date: December 13, 2004

Creator: Aceves, S. M.; Flowers, D. L.; Martinez-Frias, J.; Espinosa-Loza, F.; Christensen, M.; Johansson, B. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Exhaust energy recovery for control of a homogenous charge compression ignition engine

No Description Available.

Date: April 3, 2000

Creator: Martinez-Frias, J M; Aceves, S M; Flowers, D; Smith, J R & Dibble, R

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development and Testing of a 6-Cylinder HCCI Engine for Distributed Generation

This paper describes the technical approach for converting a Caterpillar 3406 natural gas spark ignited engine into HCCI mode. The paper describes all stages of the process, starting with a preliminary analysis that determined that the engine can be operated by preheating the intake air with a heat exchanger that recovers energy from the exhaust gases. This heat exchanger plays a dual role, since it is also used for starting the engine. For start-up, the heat exchanger is preheated with a natur… more

Date: July 12, 2005

Creator: Flowers, D. L.; Martinez-Frias, J.; Espinosa-Loza, F.; Killingsworth, N.; Aceves, S. M.; Dibble, R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Piston-Liner Crevice Geometry Effect on HCCI Combustion by Multi-Zone Analysis

A multi-zone model has been developed that accurately predicts HCCI combustion and emissions. The multizone methodology is based on the observation that turbulence does not play a direct role on HCCI combustion. Instead, chemical kinetics dominates the process, with hotter zones reacting first, and then colder zones reacting in rapid succession. Here, the multi-zone model has been applied to analyze the effect of piston crevice geometry on HCCI combustion and emissions. Three different pistons … more

Date: September 4, 2002

Creator: Aceves, S. M.; Flowers, D. L.; Espinosa-Loza, F.; Martinez-Frias, J.; Dibble, R. W.; Christensen, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department