Spring-loaded Valve Research Articles

A simple and reliable approach for the direct injection of hydrogen in internal combustion engines at low and medium pressures

Direct injection of hydrogen in internal combustion engines is being recognized as the most appropriate approach to smooth and efficient operation. However, control techniques for the direct injection of hydrogen are all built around the idea of spring-loaded puppet valves, controlled mechanically through rocker arm and camshaft arrangements, or using electromagnetic coils. In both approaches, technical difficulties usually arise because of the relatively complicated multi-component arrangements and because of the excessive temperatures at the top of the cylinder head. To help solve these problems, an assembly comprising a simple hydrogen injector, separated from a simple rotary controller, is introduced in this paper. The hydrogen injector assembly worked in our laboratory, safely and reliably, without the need for springs, coils or cams. Nevertheless, if required, any of these components could be incorporated in a separate controller, away from the high temperature cylinder head. In this way, simple electromagnetic or mechanical controllers could be reliably used.

Fast variable-amplitude cold gas thruster

A fast response variable amplitude cold gas thruster is described. A laboratory prototype comprised of a piezoelectric stack and an associated microprocessor-based programmable dc power source, a low-loss mechanical displacement amplifier, a high-pressure spring-loaded axial valve, an integral high-pressure valve seat; an expansion nozzle, and a high-pressure gas supply were constructed and tested. The device is designed to operate as a stand-alone unit with a dedicated onboard microcontroller system and onboard energy storage system. Minimum pulse-width resolution (base-to-base) was shown to be 0.98 ms, with a lag time of 0.37 ms relative to the initiation of the drive pulse. Linear amplitude response was achieved beyond a threshold drive voltage of 80 vdc and was maintained through the limit of testing at 240 vdc.

Cementing - A Systematic Approach

Summary We developed a step-by-step cementing process design chart for Conoco Inc.'s operating divisions. It includes information on selecting cement and additives and the associated hardware for casing and liner cementing operations. Each cementing operation is designed to ensure the compatibility of hardware and cement slurry components. The chart is separated into two major categories - primary and liner cementing. These categories are separated further into design criteria for cementing each casing string in a well, conductor pipe through production string, and each type of liner that is set. Conoco has reduced primary cementing costs by as much as $35,000/well and has had fewer remedial cement jobs because of adherence to practices in the design chart. These cost savings can be attributed to proper cementing practices consolidated from many geographic regions that are included in this easy-to-use chart. For example, cement costs can be reduced by limiting the use of expensive synthetic cement additives in less critical pipe strings. Less expensive natural cement additives, which perform just as well, can be used to reduce the cost per cubic foot of cement slurry. Introduction Because of economic "belt-tightening" caused by depressed oil prices, all phases of drilling, completion, and production operations are undergoing cost reviews. When high-cost areas are identified, we must reduce costs without compromising design specifications. One such cost area is cement and cement additives that are used in oil, gas, and injection well cementing. During the drilling and completion phases of a well, all casing strings must be cemented to effect a hydraulic seal between the formation and pipe, to protect and to support the casing, and to isolate production zones. Failure to accomplish this can result in costly well repairs and may endanger equipment, lives, or the environment. For this reason, primary cementing operations must be carried out in such a way as to attain these cementing goals without resorting to expensive remedial squeeze cementing. The engineer must optimize primary cement slurry design and placement techniques. Casing and liner cement design generally is a joint effort among drilling, engineering, and cement service companies. The resulting design often is influenced by such factors as personal experiences, total cost or bids, profit margins, working-time safety factors, and equipment availability, rather than by prudent engineering based on available data. This method contributes to increased primary cementing costs, increased remedial costs, and sometimes, lost production. This paper describes how we have reduced cementing costs without compromising design specifications. Furthermore, in-house cementing schools and cementing studies are conducted to improve cementing practices and to reduce cementing costs. We will present case histories and the cementing process design chart that incorporates this philosophy in a systematic approach for cementing casing strings in a cost-effective manner. The Process Design Chart The process design chart in the Appendix will aid engineers and operations personnel in designing and executing successful cementing operations. While the chart is intended for general use, we realize that each well has individual characteristics that must be examined separately. Therefore, we do not specify how much additive is needed for a particular case, but we do indicate maximum amounts. When cementing recommendations exceed the maximum limits, the slurry design should be questioned and the reasons explained. We also consider casing hardware. The design of the chart generally proceeds from the well bottom to the top and reflects what is considered the best technology to obtain a uniform cement sheath around each casing string. For example, float equipment that has a spring-loaded dart valve generally is recommended over ball or flapper valves. This recommendation is based on calculations of the differential forces exerted on the seal during cement placement vs. the seal's resistance to failure. The chart does not necessarily recommend the use of the least expensive cement slurry, but it does inform the user about the available products and slurry design choices. The choice of what slurry and casing hardware to use will depend on well parameters and other design considerations the user feels are most important during the life of the well. The chart is designed so that the user can read from the top to the bottom of a casing string or liner column, and make decisions that are based on well requirements. By the end of the column, the user should be able to select an appropriate cementing procedure and corresponding cement slurry design, as well as the compatible casing hardware.

Automatic mechanical alveolar gas sampler for multiple-sample collection in field.

A mechanical alveolar gas sampler using the revolver principle capable of collecting six individual expired gas samples is described. The 0.91-kg sampler collects 19-ml samples in pre-evacuated aluminum ampoules equipped with spring-loaded valves from a sampling chamber equipped with two removable one-way valves. On depression of external handles, one of six ampoules located in a removable cartridge is aligned and advanced into the sampling chamber where its valve is opened and then closed. Releasing the handles removes the ampoule from the sampling chamber and automatically rotates the cartridge through 60 degrees to position a new ampoule in preparation for the next sampling sequence. A lock-out mechanism prevents reexposure of any of the ampoules after six samples have been taken. The performance of the sampler is described including its successful use in the field to collect alveolar gas samples on the summit of Mount Everest.

A SIMPLE AND INEXPENSIVE DEVICE FOR ADMINISTRATION OF CONTINUOUS POSITIVE AIRWAY PRESSURE BREATHING

A simple system for administration of continuous positive airway pressure breathing uses a corrugated hose in the modified Mapleson D system for anaesthesia. The only mechanical component of the system is a spring-loaded valve for positive end expiratory pressure.

Use of a cell rupturing pump for the preparation of thymocyte subcellular fractions

A motor-driven cell-rupturing pump is described and its performance in preparing thymocyte membranes evaluated. Cell suspensions are forced through a spring-loaded valve which can be adjusted to regulate the operating pressure. Any degree of cell rupture up to complete disintegration of subcellular components can be produced by varying the pressure. The pump can be operated continuously, so that there is no limit to the volume which can be processed, but volumes down to 0.1 ml can also be handled. A good yield of highly antigenic and enzymatically active cell membranes and other subcellular components was obtained. The pump appears to be at least as effective as any other available device for cell rupturing, and is small, versatile, and simple to use.

Determination of stresses in plates of spring-loaded valves made of strip

Determination of stresses in plates of spring-loaded valves made of strip

A Fine-Control Carbon Dioxide Injection Circuit for the Measurement of Rates of Net Photosynthesis by Infra-Red Gas Analysis

The measurement of rates of net photosynthesis by infra-red gas analysis has in the past been carried out in open, closed, and semi-closed circuits, all of which are unsuitable for factorial experiments involving, as the dependent variate, predeter mined rates of photosynthesis at measured steady-state carbon dioxide concentra tions (Heath, 1969). In addition, the closed circuit does not allow for steady-state measurements and the open circuit must be operated with an expensive flow-meter of great accuracy at variable high volume flows. Other processes such as trans piration and leaf temperature will, of course, be afFected by the variable high volume flows even if there is a good mixing fan in the chamber. As an alternative to varying the main flow, air-carbon dioxide mixtures must be supplied by expensive mixing pumps. In the semi-closed circuit a special air-carbon dioxide mixture must be provided under constant pressure and the total through-flow will remain variable with possible effects on processes other than photosynthesis. The carbon dioxide injec tion circuit described below removes most of the shortcomings mentioned and has the advantage of using ordinary laboratory equipment. Carbon dioxide injection in such quantities as are assimilated by the plant material in the chamber (i.e. as are necessary to maintain a constant carbon dioxide concentration in a closed system), has hitherto been from a carbon dioxide cylinder with a pressure-reducing valve in combination with a fine needle valve and capillary soap-bubble meter (Meidner, 1967, 1968). Results obtained were satisfactory, but the unavoidable play in even the best spring-loaded needle valve made fine adjustments during an experiment time-consuming and difficult. The

Paper 3: An Analytical and Experimental Study of Self-Acting Valves in a Reciprocating Air Compressor

A digital computer is used to solve the differential equations which form a mathematical model of a self-acting valve. The model describes the movement of a suction or a discharge valve, and the pressure difference across the valve. The computer results are compared with experimental records obtained over a range of operating conditions from a single-stage air compressor fitted with spring-loaded ring-plate valves. Subsequently the analysis provides conventional criteria of compressor performance.

The Theory of Spring-Loaded Valves for Reciprocating Compressors

Abstract The inlet and discharge processes of a reciprocating compressor equipped with spring-loaded valves of the automatic type have been analyzed to determine the effects of the main design variables on performance. The most important criterion is found to be a parameter involving effective flow area through the valves and piston speed. Valve dynamics is a secondary consideration. For optimum valve dynamics, the valve would have no weight and a very small spring constant, giving an infinite natural frequency of the valve system. If certain valve characteristics are known (or measured by static-flow test), the performance of a compressor using these valves can be predicted with fair accuracy.

Pressure Calculations for Oil Engine Fuel-Injection Systems

The paper gives details of a method of calculation for use in determining the pressure variations in the normal fuel-injection system. This method, besides dealing with the transmission of pressure impulses from one end of the pipe to the other, includes those modifying conditions present in an actual system, namely the capacity effects at the pump and at the nozzle, the action of the pump delivery valve, and the varying conditions in the spring-loaded injection valve. The results of a calculation on a typical injection system have been incorporated in the paper. A diagram of nozzle pressure, obtained experimentally from the same system, is also included for comparison with the results of the calculation. This experimental diagram agrees so well with the calculated results that the treatment described may be regarded as giving a very close approximation to the actual conditions in the injection system.