Search Results

This paper investigates Homogeneous Charge Compression Ignition (HCCI) combustion on an engine that is fuelled with ethanol, iso-octane, and ethanol/iso-octane. The engine is a four-stroke three cylinder indirect injection type diesel engine converted to a single cylinder HCCI operation. In order to clarify the effects of fuel chemistry on HCCI combustion, the trials were done at a constant engine speed, a fixed initial charge temperature and engine coolant temperature. The HCCI engine was fuelled with a lean mixture of air and fuel (ethanol, iso-octane or mixture of ethanol/iso-octane). The engine performance parameters studied here include indicated mean effective pressure (IMEP) and thermal efficiency. Heat-release rate (HRR) analysis was done to determine the effect of fuels on combustion on-set. The experimental results demonstrate that the addition of iso-octane to ethanol retards the on-set of combustion and subsequently leads to a reduction of the IMEP and thermal efficiency.

This paper investigates the expansion of the HCCI operating range and combustion control by use of internal fuel reforming with subsequent reduction of NO emissions through Exhaust Gas Recirculation (EGR). The study is focused on multi-step simulation of the engine cycle, comprised of a fuel reformation cycle and a HCCI combustion cycle, with and without EGR. The study is carried out using a single-zone well-stirred reactor model and established reaction mechanisms. The HCCI engine cycle is fueled with a lean mixture of air and ethanol. This study demonstrates that supplementing EGR with internal reforming reduces the NO emissions level. Furthermore, the study shows that internal fuel reforming extends the operational range of HCCI engines into the partial load region and is effective in the combustion onset control. However, the model requires several enhancements in order to moderate the cycle pressure rise and pressure magnitude, and to lower the cycle temperatures and NO emissions.

Stirling cryocoolers with a single stage of expansion routinely achieve cryogenic refrigeration temperatures of 70 K. Lower temperatures can be achieved with multiple expansion stages arranged ‘in series’, 20 K with two stages, and less than 10 K with three or four stages. Multiple expansion Stirling power systems are also in prospect particularly for exhaust heat recovery systems using different stages of progressively lower temperatures. Two or more stages can be combined in a single cylinder. Multiple expansion Stirling machines have been a topic of interest at The University of Calgary for some years. Recently a second-order computer simulation program with integral graphics package for Stirling cryocoolers with up to four stages of expansion were developed and made available to the Stirling community. Adaptation of the program to multiple expansion Stirling power systems is anticipated. This paper briefly introduces the program and presents a specimen result.

In pipeline compressor stations natural gas fuelled aircraft derivative gas turbines are frequently used in conjunction with a power turbine to drive the large centrifugal compressors for ‘boosting’ the pipeline pressure. Typically two thirds of the energy provided to drive the turbine is carried off as heat in the exhaust stream. These hot exhaust streams, typically at temperatures around 500 K contain very substantial energies, 50 MW being not uncommon. This paper summarises recent studies carried out to assess the feasibility and worth of applying Stirling power systems to generate electric power from these ‘waste’ streams. Both ‘bottoming’ and topping cycles are of interest and are briefly considered in this paper. An elementary, but realistic, performance analysis indicates the possibility of recovering as much as 9 MW power from the exhaust of a gas compressor equipped with a Rolls-Royce RB 211 aircraft derivative gas turbine.

The Fluidyne, or liquid piston stirling engine, has many characteristics which make its use in developing nations particularly attractive. Besides being compatible with the use of lowgrade heat sources, the machine is simple to manufacture using a variety of low cost materials and is exceedingly reliable. This paper uses a summary of fluidyne experience to evaluate applications of the fluidyne to water pumping requirements in developing countries for purposes including domestic, livestock, and irrigating uses for water pumping. Possible sources of energy are evaluated in the light of availability and needs. Environmental, economic, and social benefits are also examined. Particular applications of the fluidyne to existing situations in China are evaluated in detail.

Stirling refrigerators are well established in the cryogenic temperature range and the system of choice in the miniature closed cycle versions used for cooling the infrared detectors of night vision and missile guidance systems. They are rarely used at the higher ‘near ambient’ temperatures of air conditioning plants and domestic or commercial refrigerating systems. However, increasing public concern at the impact of ‘Freon’ refrigerants on the ozone layer of the Earth has focussed attention on the need for alternatives to the present vapor-compression refrigerating systems. This social concern provides unparalleled opportunities for the development and application of ‘near-ambient’ temperature refrigerating systems. This paper briefly reviews the previous work and presents recent innovative concepts and designs for compact Stirling refrigerators that could be the basis for alternatives for Freon-free refrigeration.