The hydrogen-fueled internal combustion engine : a technical review.

https://biblio.ugent.be/publication/818298/file/818329.pdf

Hydrogen-fueled internal combustion engines

Four types of hydrogen detectors are used by researchers, engineers, and manufacturers 
today, and if hydrogen continues to play a role in emerging alternative energy sources, 
there will be exponential growth in the use and need for more advanced and more robust 
devices in the future. The types of sensors reviewed in this chapter are (1) room-temperature hydrogen leak sensors; (2) thermometers, particularly useful at low temperature; 
(3) liquid hydrogen volume and mass gauges; and (4) para/ortho hydrogen ratiometers.

Demonstrating the Multi Fuel Capability of a Homogeneous Charge Compression Ignition Engine with Variable Compression Ratio

https://www.engr.colostate.edu/~marchese/combustion10/2.pdf

Homogeneous charge compression ignition (HCCI): Benefits, compromises, and future engine applications

Sandia National Laboratories has been investigating a new, integrated approach to generating electricity with ultra low emissions and very high efficiency for low power (30 kW) applications such as hybrid vehicles and portable generators. Our approach utilizes a free piston in a double-ended cylinder. Combustion occurs alternately at each cylinder end, with intake/exhaust processes accomplished through a two stroke cycle. A linear alternator is mounted in the center section of the cylinder, serving to both generate useful electrical power and to control the compression ratio by varying the rate of electrical generation. Thus, a mechanically simple geometry results in an electronically controlled variable compression ratio configuration.

/pdf/homogeneous-charge-compression-ignition-with-a-free-piston-a-5gpzo52fka.pdf

Homogeneous Charge Compression Ignition with a Free Piston: A New Approach to Ideal Otto Cycle Performance

A free piston, internal combustion (IC) engine, operating at high compression ratio (~30:1) and low equivalence ratio (φ~0.35), and utilizing homogeneous charge compression ignition combustion, has been proposed by Sandia National Laboratories as a means of significantly improving the IC engine’s cycle thermal efficiency and exhaust emissions. A zero-dimensional, thermodynamic model with detailed chemical kinetics, and empirical scavenging, heat transfer, and friction component models has been used to analyze the steady-state operating characteristics of this engine. The cycle simulations using hydrogen as the fuel, have indicated the critical factors affecting the engine’s performance, and suggest the limits of improvement possible relative to conventional IC engine technologies.

A numerical study of a free piston ic engine operating on homogeneous charge compression ignition combustion

A free piston internal combustion (IC) engine operating on high compression ratio (CR) homogeneous charge compression ignition (HCCI) combustion is being developed by Sandia National Laboratories to significantly improve the thermal efficiency and exhaust emissions relative to conventional crankshaft-driven SI and Diesel engines. A two-stroke scavenging process recharges the engine and is key to realizing the efficiency and emissions potential of the device. To ensure that the engine’s performance goals can be achieved the scavenging system was configured using computational fluid dynamics (CFD), zero- and onedimensional modeling, and single step parametric variations. A wide range of design options was investigated including the use of loop, hybrid-loop and uniflow scavenging methods, different charge delivery options, and various operating schemes. Parameters such as the intake/exhaust port arrangement, valve lift/timing, charging pressure and piston frequency were varied. Operating schemes including a standard uniflow configuration, a low charging pressure option, a stratified scavenging geometry, and an over-expanded (Atkinson) cycle were studied. The computational results indicated that a stratified scavenging scheme employing a uniflow geometry, and supplied by a stable, low temperature/pressure charge will best optimize the efficiency and emissions characteristics of the engine. The operating CR can be maximized through substantial replacement of the burned charge, while short-circuiting emissions can be controlled by late fuel introduction. The in-cylinder flows are important to both NOx and short-circuiting emissions with inadequate mixing (and resulting temperature stratification) the predominant driver of NO production, and fuel penetration to the exhaust valve region the main cause of unburned hydrocarbon emissions.

Optimizing the Scavenging System for a Two-Stroke Cycle, Free Piston Engine for High Efficiency and Low Emissions: A Computational Approach

NOx Emissions and Efficiency of Hydrogen, Natural Gas, and Hydrogen/Natural Gas Blended Fuels

A combustion system which can utilize high compression ratios, short burn durations, and homogeneous fuel/air mixtures in conjunction with low equivalence ratios In particular, a free-piston, two-stroke autoignition internal combustion engine including an electrical generator having a linear alternator with a double-ended free piston that oscillates inside a closed cylinder is provided Fuel and air are introduced in a two-stroke cycle fashion on each end, where the cylinder charge is compressed to the point of autoignition without spark plugs The piston is driven in an oscillating motion as combustion occurs successively on each end This leads to rapid combustion at almost constant volume for any fuel/air equivalence ratio mixture at very high compression ratios The engine is characterized by high thermal efficiency and low NO x emissions The engine is particularly suited for generating electrical current in a hybrid automobile

Peter Van Blarigan

Papers

Homogeneous Charge Compression Ignition with a Free Piston: A New Approach to Ideal Otto Cycle Performance

A numerical study of a free piston ic engine operating on homogeneous charge compression ignition combustion

Optimizing the Scavenging System for a Two-Stroke Cycle, Free Piston Engine for High Efficiency and Low Emissions: A Computational Approach

NOx Emissions and Efficiency of Hydrogen, Natural Gas, and Hydrogen/Natural Gas Blended Fuels

Free-piston engine